**3. Off-shore structures**

Off-shore marine structures such as oil rigs and columns of bridges, underwater pipe line supports, etc., are conventionally made using reinforced cement concrete having steel rods as reinforcements inside the concrete. In some other cases, steel pipes, pillars, and column supports are used.

The underwater static steel structures are protected from corrosion and fouling by electrochemical protection system and paints. A new method of protecting the steel structure is to provide a wrap of composite as an outer lining, which is far more durable than painting and more maintenance-free. Steel pipes are used as a mandrel for a filament winding technique to provide a composite lining. Steel structures require underwater welding, etc., for repair and maintenance, which is very complicated and costly. The FRP lining provides a very convenient solution to reduce such maintenance cost and frequency of repair.

The concrete with diffused sea water generates more alkali, and the pH of this alkaline seawater increases from normal range of 8–8.3 to about 12–13 and

accelerates the corrosion of the steel reinforcement in the RCC structure. Therefore, FRP reinforcements are modern way of construction for higher durability and lesser maintenance. However, in a higher alkaline sea water environment, the FRP degradation is expected to be faster than in normal sea water.

For off-shore and maritime civil engineering structures, carbon fiber composites (CFRP) are preferred over glass fiber (GFRP) because of higher mechanical strength of CFRP. In addition, sea water uptake and degradation of GFRP in sea water are higher those in than CFRP. There are very few applications of GFRP in marine structures despite the fact that GFRP is cheaper compared with CFRP.

The durability is also dependent on the resin type and its interface bonding with the fiber. Generally, thermosetting polymers such as epoxy, polyurethane, phenolic resin, vinyl ester, and unsaturated polyester resins are used for composites. These resins and corresponding composites are to be evaluated for long period of sea water exposure in an RCC construction for durability. As accelerated studies might give some extrapolated figures of service life, but such studies cannot determine the effect of microorganisms on degradation of a composite. A very common example is sulfate-reducing bacteria (SRB) in the sea water. These organisms use sulfates dissolved in the sea (for example, MgSO4) for metabolism and produce hydrogen sulfide, which is highly corrosive to metals and may also increase the degradation of composites after settling onto the surface. The effect of such organisms is much more important for static structures rather than moving objects. Fouling by other micro and macro-organisms and subsequently the effect on the composite is another aspect of static structures. The protection from bio-fouling by application of anti-fouling coating is another subject of study. However, this type of coatings work either on toxin release mechanism or by providing a low surface energy coating. In case of toxin release coating, the toxin release depends on the hydrolysis and dissolution of the toxin in water, which is more effective in moving condition than stagnant water. Because of toxin depletion, the coating requires renewal after a certain time, mostly 3 years. In case of low surface energy coating, the effectiveness is far less for static structures, as this type of coating is quite good for moving objects, that too at certain minimum speed. However, the advantage is that the settlement of bio-fouling species on these low surface energy coating is very weak and can be removed by a soft cleaning mop. The second most important aspect of static structures is stress. Most supports and beams are under stress, small or large. The pre-stressed composite structure may have lesser service life compared with no-stress elements. The third consideration is fatigue. A bridge column, pipeline carrying liquids under the sea are subjected to vibrations. Hence, the composite elements are to be evaluated by fatigue for a predetermined frequency and number of cycles. This should be done in a repeated experiment and at a regular immersion period. The effect of pre-stress and vibration parameters may reveal some results, which could be different from normal static experiments.

## **4. Quality of a marine-grade resin and FRP**

A general understanding of large-scale application of FRP is that there can be three main alternatives for a techno-commercially viable thermoset selection, e.g., (1) unsaturated polyester resin (USP) cross-linked with styrene, (2) vinyl ester resin (VE) cross-linked with styrene, and (3) epoxy resin cross-linked with amine. Whereas, there can be two common fibers such as glass and carbon.

Service life of a structural element for marine vessels has to be minimum 25 years for reducing the investment for replacement and should be maintenancefree for at least 8 years to reduce the cost of refits in drydocks. For off-shore

### *FRP for Marine Application DOI: http://dx.doi.org/10.5772/intechopen.101332*

structures, where FRPs are used to make barrier for underwater cement concrete structures, the maintainability is even more difficult, requiring high service life without maintenance activity. Apart from the general physical and mechanical properties, an FRP for marine application must have additional characteristics of low moisture/sea water ingress, minimum hydrolysis, good bond strength between fiber and polymer, minimum physical damage of fiber and polymer due to water ingress and retention of mechanical properties even after prolonged sea water immersion. However, all the properties are primarily dependent on the matrix polymer and fiber and their interaction, secondary parameter being processing technique and fabrication methods to make flawless FRP components with fairly accurate dimensions, such as for a marine ball valve or pipe joint. Processing assumes larger importance since partially cured samples are prone to poorer physico-mechanical properties and higher degradation in water.

A significant improvement in properties of marine composites can be achieved by prepreg method and resin transfer molding (RTM) assisted by vacuum. Good compaction and high fiber volume fraction can be achieved by these processes. The process of prepreg molding is feasible where the resin-hardener reaction does not take place at ambient or storage temperature, and the curing is done at a fixed higher temperature. There are high-temperature reacting systems such as epoxy resin 4,40 methylene dianiline tetraglycidyl ether (TGDDM), to be cured with hardener such as 4,40 -diaminodiphenyl sulfone (DDS), modified polyamines, etc., which are used for making prepregs. The shelf life of such prepregs at storage temperature of �20°C is about 10–12 months, but few weeks at 20°C. The prepregs are cured in compression at above 100°C. However, prepreg system may not be possible for vinyl ester or polyester resins. RTM process requires low viscosity resin and hardener to facilitate good flow in the fabric stacked in the mold for proper wetting at all corners and contours. Trujillo et al. [6] reported the properties of RTM processed composites based on three common resins, i.e., epoxy, vinyl ester, and unsaturated polyester with glass and carbon fabrics. The flexural modulus of the glass composites was about 40GPa and about 110–120 GPa for carbon fabric composites, while the flexural strengths were seen to be in the range of 600–800 for glass composites and 1300–1400 MPa for carbon fabric composites.

Sea water absorption causes changes in the matrix by both plasticization and hydrolysis. Initial effect of water ingress is a plasticizing effect and swelling of the polymer matrix. The results are lowering of glass transition temperature due to plasticization and a possibility of debonding of the polymer-fiber interface due to swelling of the polymer. The initial effect of water ingress also causes hydrolysis of the fiber sizing and generates alkali (Na+ and K+) and the Fiber-polymer interface weakens. All these events result in reduction of ultimate strength and elastic modulus of an FRP.

On prolonged exposure, several chemical reactions may take place, such as hydrolysis of the polymer resulting in small molecules such as glycol, chain breaking, and release of low-molecular-weight polymer (especially polyester), release of the constituents of the resin (typically maleic/fumaric acid), release of styrene (cross-linker for polyester and vinyl ester), and extraction of these species from the FRP to the sea water. Prolonged water immersion of FRP may also cause mechanical damage to the fiber and polymer both, which may not be observed in short period, even in few months of exposure. SEM analysis of all FRPs irrespective of the fiber showed detachment of matrix from the fiber, which is the main reason for such drastic decrease in strength of the composite laminates as reported in literature.

The polymer plays the most important role in the hydrolytic durability of an FRP. As a special case of glass fiber reinforcement, the coated material used as coupling agent chemically degrades and causes weak interface of fiber-polymer. Therefore, a polymer-fiber combination is ultimately the consideration for optimization of hydrolytic properties.

The main reason why GFRP is not used in maritime civil construction applications is because sea water environment degrades the long-term mechanical properties of GFRP composites and interlaminar shear strength (ILSS). The glass fiberpolymer interface is strengthened by a coupling agent coated on the glass fibers and the process is called "Sizing." The sizing formulations are very complicated, may contain many different chemicals, and are proprietary to the manufacturers [7]. Most common are γ-amino propyl tri ethoxy silane (APTES), γ-glycidoxy propyl trimethoxy silane (GPTMS), γ-methacryloxy propyl trimethoxy silane (MPTMS), and vinyl tri ethoxy silane (VTES) having Si-OH groups on the fiber surface for improving the interface adhesion with the resin. The sea water diffused to the interface of fiber and polymer very quickly degrades the glass to produce alkaline oxides unless protected by sizing. Even then, prolonged immersion of the GRP with fiber with appropriate sizing may cause leaching of alkali oxides (sodium and potassium) from the surface of the fiber and degrade the composite mechanical property [8].

## **4.1 Epoxy thermoset-based FRP for marine application**

Epoxy resin is a versatile thermoset, widely used in many marine structures for many years. It has good mechanical properties, is highly polar and compatible to most fibers including metals, glass, carbon, Kevlar, and polybenzimidazole. Epoxy nanocomposites are gaining importance due to lightweight and high performance in some functional properties when used with carbon nanotubes, nanofibers, graphene, and also natural nanofibers. The conventional epoxy resin thermosets are somewhat brittle and, in many occasions, modifications are done either by physical mixing or chemical reaction onto the epoxy oligomer or use of high-molecularweight epoxy and/or the amine curing agent to make optimum tough thermoset. However, flexibilization means increase in free volume in the polymer and subsequent increase in moisture absorption. As such the degradation of conventional epoxy thermoset and composites is very widely studied by many researchers since last 45 years, for example, by Augl and Berger [9] in 1976 on carbon fiber-epoxy composites, McKague et al. [10], DeIasi and Whiteside [11], and Whitney and Browning [12] studied moisture diffusion in epoxy matrix and composite, during 1976–1978, to name a few. Similarly, Loos and Springer [13], Bohlmann and Derby [14], Shirrell [15] studied moisture diffusion and its effect on graphite epoxy composites way back during 19761979. Glass fiber-epoxy composites are most widely evaluated for effect of moisture or water or sea water absorption from those periods and are still being the subject of study. A few are listed here as references [16–30].

The glass transition temperature of cured epoxy matrix and composites is reduced from 120°C to as low as 66°C on a 2-month sea water exposure, but was observed to be almost constant around 85–88°C from 4 months onward till the end of the study period (12 months), as reported by Chakraverty et al. [31]. The authors explained this anomaly by probable osmotic effect of the bulky molecules of dissolved salts in sea water, which might have initially facilitated the creation of more free volume in the cross-linked epoxy matrix, but on prolonged exposure, deposition of these salts could have reduced the water ingress. Murthy et al. [32] have shown that the water uptake by epoxy-glass composite is more (about 0.9%) compared with 0.7% by epoxy-carbon composites after 12 months and remained unchanged. However, their study was limited to 16 months. The ILSS was reduced by 38% for epoxy-carbon and by 31% for 450 days at ambient temperature. SEM analysis revealed that the moisture penetration along the fiber/matrix interfaces

### *FRP for Marine Application DOI: http://dx.doi.org/10.5772/intechopen.101332*

caused interfacial debonding and consequently degradation of the interface. Espinel et al. [28] also showed that for an epoxy-glass composite, the saturation level of sea water was 0.4% at 25°C attained after 30 days. The tensile and flexural strength reduced by about 24% and 35% respectively after 90 days sea water immersion at 25°C, but observed that the strength did not decrease much after saturation of sew water. Contrary to these results, Murad et al. [25] showed that the sea water intake in epoxy-glass unidirectional composite was 2.5% after 12 months, but the strength and elastic modulus had no noticeable change compared with fresh sample. However, the fiber volume % was only 52. Wood and Bradley [20] also reported about 2.2% sea water uptake for 5 months at ambient temperature for an epoxy-glassgraphite hybrid composite, each layer fabricated by a similar process as filament winding, and hence the layers were unidirectional. The glass and carbon were in transverse direction to each other. However, the resin used had a 5% flexibilizer (rubber) and fiber volume % was 60. Komorek et al. [29] used fabrics of glass and carbon in epoxy resin. The bending strength was found to be 8% less for the samples immersed for 36 days at 15°C in sea water.

A unique study on fatigue and sea water aging of epoxy-glass and epoxy-Kevlar composite was done by Menali et al. [33]. The authors studied the effect of sea water (artificial) immersion (40 days) after fatigue for 100–50,000 cycles for these composites. There was about 19% reduction in tensile strength for the Glass-epoxy composite samples and about 15% for Kevlar-epoxy samples which had undergone 50,000 cycles of straining and aged in sea water for 40 days. The stiffness of the composite laminates was also degraded by almost similar extent. This result, when compared with that of Komorek [29], clearly shows the additional degradation under cyclic loading.

There is another interesting review report by Li et al. [34] on effect of alkaline sea water (pH at 12–13) for pre-stressed FRP laminate and FRP tendons. The alkaline sea water simulates the property of the sea water sea sand concrete (SWSSC), which is now very much used in civil construction of marine static structures such as off-shore platforms. The authors compiled several results by some researchers. It is seen from the review article that the alkaline SWSSC at pH of 12–13 has a higher degrading effect under such condition.

A comprehensive study was done on the effect of sea water immersion at various temperatures for an epoxy thermoset plaque and its E-glass fabric composite having 55% fiber by volume. The report is not for publication. The composite samples were made by vacuum bagging process followed by compression molding at 120°C. The curing of plaque and composite was done after thorough degassing of the resinhardener mix. It was observed that after 360 days of immersion, the flexural strength reduced from about 90 MPa to about 65 MPa, and the dynamic flexural modulus was reduced from about 3.20 GPa to about 2.5 GPa at 30°C in natural sea water. The E-glass composites of the same resin were seen to deteriorate in flexural strength and modulus. The strength reduced from 250 MPa to about 180 MPa, and the dynamic modulus reduced from 8 GPa to about 5.5 GPa. The results clearly show the effect of debonding of the fiber from the epoxy matrix interface thereby drastically reducing the loadbearing capability. The water had a plasticizer effect too, as the glass transition temperature changed from 60 to 62°C to about 52–54°C in 12 months, and the SEM micrograph showed separation of the fiber from the matrix at the interface very clearly. However, the effect of the microbes on degradation could not be quantified separately.

The studies done so far indicate a common observation and conclusion that the degradation of epoxy-based composites is significantly high in terms of delamination, loss of mechanical properties and glass transition on exposure in sea water even for a year. The initial moisture ingress has a plasticizing and swelling effect,

due to which the glass transition temperature reduces with a drop in mechanical properties. In prolonged exposure, the water molecules chemically react with the resin (hydrolysis) producing small chemical substances, which tend to diffuse out of the resin, causing blisters. Also, various salt components of the sea water may affect the moisture absorption rate compromising some properties of FRP in sea water. It is also known that the effect of sea water on glass fiber reinforced composites differs according to the type of matrix and fiber. The mode of failure of glass/epoxy composite is altered from a brittle matrix and ductile fiber to ductile matrix and brittle fiber. However, in some opinion, the strength stabilizes after the absorbed moisture attains saturation.

In construction of FRP elements of ships, the items that are not in continuous immersed condition such as superstructures, ladders, stanchions, guard rails, etc., are better designed with toughened epoxy resin and carbon/glass fabric composites since the degradation is limited in the atmosphere and the composites can have sufficient strength, reasonable glass transition temperature even after the toughening process of the resin. For naval ships of stealth features, carbon fiber and nanocarbons cannot be used as the radar reflection will be increased. For elements to be used underwater, epoxy resin is not that superior to the vinyl ester class of resins.

## **4.2 Vinyl-ester-based FRP composites**

Vinyl ester resins are most commonly used for marine composites for two main reasons, the mechanical strength retention on prolonged exposure in sea water and the strength is comparable to epoxy composites and higher than polyester-based composites. The resin has inherent resistance to water diffusion and consequently lesser effect on its glass transition and strength. For large ship structures, vinyl ester resin is a better thermoset due to suitability for processing large items such as hulls, using vacuum infusion due to its low viscosity, apart from its durability in marine environment.

Conventional vinyl esters are having aromatic backbone of epoxy base and the double bond of the unsaturated ester is cured by styrene, exactly the same process as a polyester resin. The presence of the higher content of stiff aromatic epoxy backbone provides the higher mechanical strength compared with phthalic-acidbased polyesters. The higher aromatic content also restricts the diffusion of fluids. Unlike epoxy matrix cured by amines, the vinyl ester matrix is cured by hydrophobic monomer styrene, and hence, the water ingress is lesser than epoxy resin.

VE-CFRP and VE-GRPF have different strength ratios depending on the mode of force application. Wonderly et al. [35] compared these two types of composites in terms of tensile strength and found that CFRP was about 850–950 MPa and was 1.6–1.75 times higher than GFRP, but the open hole tensile strength was comparable at about 250–265 MPa, and compression strength of GFRP was about 330–360 MPa for CFRP and was about 17% lower than GFRP. Transverse tensile strength of CFRP was also about 75% of GFRP. One interesting study was done by the authors on ballistic impact test, which is important for military application. At a comparable areal density, the specific energy (J/kg/m2 ) required to penetrate the panels for CFRP was higher by about 25% compared with GFRP for identical muzzle velocity.

In general, the glass transition temperature of a vinyl ester matrix is about 115–120°C. The flexural modulus and strength of a vinyl ester plaque are about 3.0–3.5 GPa and 80–120 MPa respectively, almost same as epoxy plaque. GFRP of vinyl ester has flexural modulus of about 10–12 GPa and flexural strength of about 270–300 MPa, ILSS of about 30–35 MPa, depending on the fiber type and fiber volume fraction in the composite. The CFRP of vinyl ester has much higher strength and modulus, about 3–3.5 times higher than GFRP at the identical volume fraction of fiber.

Water diffusion studies show on an average 0.6% water intake at equilibrium for GFRP and about 0.4% for CFRP, which are almost half of corresponding figures for epoxy CFRP. Murthy et al. [32] showed that the sea water saturation levels in both GFRP and CFRP of vinyl ester are about 0.7% and approximately 0.4% respectively, and there was no reduction in the total weight of the samples even after 450 days of immersion. The interlaminar shear strength was reduced by about 35% after 365 days for both CFRP and GFRP of vinyl ester. Similar extent of degradation was observed for flexural strength. The reduction of tensile strength was about 30% for the same period of immersion. However, it is observed that the mechanical properties and the water uptake almost became steady after 365 days. The authors showed that after immersion in artificial sea water for 450 days, the strength reduced by about 35% for both the composites. Similarly, the ILSS also reduced by about same extent. CFRP is marginally better in ILSS on aging in sea water. The maximum water intake for CFRP was about 0.4% compared with about 0.48% for GFRP.

A study by Mungamurugu et al. [36] showed about 1% water absorption at 20°C for vinyl ester GFRP composite for glass fiber volume of 58% compared with about 0.75% for the plaque after 450 day and the reduction in flexural strength (original 250 MPa) by about 25% for the composite after 300 days.

However, most experiments reported in literature are done with artificial sea water, and the effect of the microorganisms and of the evolved materials due to the metabolism of the microbes present in sea water was not possible to observe. Therefore, the drastic decrease in mechanical strength for thermosets resin plaques is due to reaction with water and hence loss of molecular integrity of the cross-linked matrix.


**4. Heavy metals**

As mentioned earlier, heavy metals contained in mine wastes, particularly rocks and tailings, may in turn become contamination to water systems around the dumping site. Analyses of these solid wastes must be very crucially considered for environmental protection plan during the mining operation. In fact, these heavy metals usually have different forms appeared in these rocks and tailings. Some forms are quite stable and durable to natural reactions such as weathering and erosion; however, some forms may be leached and available to contamination. Moreover, their stable chemical bonds may have been destroyed during the mining process, mineral dressing and metal extraction. Therefore, placement and dumping of these solid wastes should concern about these geochemical characteristics. Several standard procedures have been proposed for analyses of heavy metals contained in geological materials such as soils, stream sediments and rocks. These methods were initially engaged for geochemical exploration searching for potential area of mineral deposits. Although, they can also be applied for environmental purpose, some assumption must be taken into consideration as well as limitation of selected method must be understood clearly before interpretation will be carried out. Some methods are designed for total concentrations of element contained in the samples; on the other hand, some of them are planned for partial portions of these elements reliable for specific concern. However, some methods have been developed for environmental impact assessment. In this section, some selective standard procedures are described for suitable application of mining waste and related fields.

#### **4.1 Total digestion**

**Whole-Rock Geochemical Analyses:** this method is designed for analysis of total chemical concentrations contained in the rock materials. This method may not be suitable to the environmental concern because major and minor compositions of these rocks are usually non toxic and they are quite stable. However, their trace compositions may have partly impact after accumulation and transportation have taken place for some periods of time, particularly due to AMD. Moreover, these whole-rock analyses are very useful for

**Potentially Net Acid Forming (PAF):** the acid potential exceeds the neutralization potential. These rocks are described as potentially acid forming. They may generate AMD if they are exposed to sufficient oxygen to allow sulfide oxidations. Geochemical tests usually yield

**Uuncertain Net Acid Forming (UC):** uncertain classification is obtained when there is an apparent conflict between the NAPP result and NAG pH; for example, NAPP is negative but NAG pH lower than 4.5 or NAPP is positive but NAG pH higher than 4.5. However, further testing work would be performed for such rock types to determine proportion

Recently, this classification has been using widely for geochemical study of waste rock and assessment of acid forming potential. Tran et al. (2003), for an example, also used NAG together with NAPP tests to figure out key criteria for construction design of waste rock dumps to avoid AMD. They collected samples from 2 sites in which have different temperatures. NAG and NAPP tests were applied to classify PAF, NAF and UC materials prior to placement control of waste rocks within the dumps. They succeeded to have

As mentioned earlier, heavy metals contained in mine wastes, particularly rocks and tailings, may in turn become contamination to water systems around the dumping site. Analyses of these solid wastes must be very crucially considered for environmental protection plan during the mining operation. In fact, these heavy metals usually have different forms appeared in these rocks and tailings. Some forms are quite stable and durable to natural reactions such as weathering and erosion; however, some forms may be leached and available to contamination. Moreover, their stable chemical bonds may have been destroyed during the mining process, mineral dressing and metal extraction. Therefore, placement and dumping of these solid wastes should concern about these geochemical characteristics. Several standard procedures have been proposed for analyses of heavy metals contained in geological materials such as soils, stream sediments and rocks. These methods were initially engaged for geochemical exploration searching for potential area of mineral deposits. Although, they can also be applied for environmental purpose, some assumption must be taken into consideration as well as limitation of selected method must be understood clearly before interpretation will be carried out. Some methods are designed for total concentrations of element contained in the samples; on the other hand, some of them are planned for partial portions of these elements reliable for specific concern. However, some methods have been developed for environmental impact assessment. In this section, some selective standard procedures are described for suitable application of mining

**Whole-Rock Geochemical Analyses:** this method is designed for analysis of total chemical concentrations contained in the rock materials. This method may not be suitable to the environmental concern because major and minor compositions of these rocks are usually non toxic and they are quite stable. However, their trace compositions may have partly impact after accumulation and transportation have taken place for some periods of time, particularly due to AMD. Moreover, these whole-rock analyses are very useful for

positive NAPP and NAG pH below 4.5.

between NAF and PAF if they occur.

**4. Heavy metals**

waste and related fields.

**4.1 Total digestion**

reduced AMD load that may be generated from both dumps.

geological classification as well as mining operation. Placement and disposal may be designed based on this classification in cooperation with other testing methods. Rock powdering using appropriate crusher and miller must be done prior to further analyses. Subsequently, the powdered rock samples may be fused to glass beads or pressed as pellet for X-ray Fluorescence (XRF) analyses of 9 major oxides (i.e., SiO2, TiO2, FeOt, MnO, MgO, CaO, Na2O, K2O and P2O5) and perhaps some trace elements (e.g., Ba, Zn, Sr, Rb, Zr, Co, Cr, Ni, Y and V). Rock standards should be used for calibration at the same analytical condition. Moreover, loss on ignition (LOI) should also be measured by weighting rock powders before and after ignition at 900º C for 3 hrs in an electric furnace. Trace and rare earth elements may be additionally analyzed using advanced instruments such as Inductively Coupled Plasma (ICP) Spectrometer, Atomic Absorption Spectrometer (AAS) and other spectrometric techniques. Rock samples have to be digested totally without remaining of rock powders. About 0.1000 g (±0.0001 g) of powdered samples are weighted and then dissolved in a concentrate HF-HNO3-HClO4 acid mixture in sealed Teflon beakers. The digested samples were diluted immediately and added mixed standard solution to all samples. Proportion of these concentrate acids is usually adapted in laboratory as well as time of digestion. Hotplate has been engaged traditionally but it may take long time. Alternatively, microwave has been applied to shorten the digestion time. This method is total digestion which most elements including toxic elements and non toxic ones are dissolved for analyses. However, these contents do not clearly reflect environmental impact. Microwave-assisted acid solubilization has been proved to be the most suitable method for the digestion of complex matrices such as sediments and soil. This method shortens the digestion time, reduces the risk of external contamination and uses smaller quantities of acid (Wang et al., 2004). However, there are different procedures required for appropriate sample types. Some standard digestion techniques are usually used for soil, sediment and sludge; for example, EPA 3052, EPA 3050B and EPA 3051 are described below.

*EPA 3052:* This method is an acid digestion of siliceous matrices, and organic matrices and other complex matrices (e.g., ashes, biological tissues, oils, oil contaminated soils, sediments, sludges and soils) which they may be totally decomposed for analysis. Powdered sample of up to 0.5 g is added into 9 ml of concentrated nitric acid and usually 3 ml hydrofluoric acid for 15 minutes using microwave. Several additional alternative acids and reagents have been applied for the digestion. These reagents include hydrochloric acid and hydrogen peroxide. A maximum sample of 1.0 g can be prepared by this method. Mixed acids and sample are placed in an inert polymeric microwave vessel then sealed prior to heating in the microwave system. Temperature may be set for specific reactions and incorporates reaching 180 ± 5 ºC in approximately shorter than 5.5 minutes and remaining at 180 ± 5 ºC for 9.5 minutes to complete specific reactions. Solution may be filtered before appropriate volume is made by dilution. Finally, the solution is now ready for analyses (e.g., AAS or ICP). More details should be obtained from EPA (1996).

**EPA 3050:** Two separate procedures have been proposed for digestion of sediment, sludge and soil etc. The first procedure is preparation for analysis of Flame Atomic Absorption Spectrometry (FLAA) or Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) whereas the other is for Graphite Furnace AA (GFAA) or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Appropriate elements and their detection limits must be concerned and designed for selection of both methods (EPA, 2009). Alternative determination techniques may also be modified as far as scientific validity is proven. This method can also be applied to other elements and matrices but performance need to be

Geochemical Application for Environmental Monitoring and Metal Mining Management 101

In the environmental field, determination of total metal concentrations in mining wastes does not give sufficient information about the mobility of metals. Metals may be bound to particulate matter by several mechanisms such as particle surfaces absorption, ion exchange, co-precipitation and complexation with organic substances. For example, not all of heavy metals in soil are available for plant uptaking, only the dissolved metals content in soil solution is moveable enough for plant to absorb. Therefore, heavy metals speciation in form of water soluble fraction and free weak acid soluble fraction out of total heavy metal content are the maximum amount of heavy metals possibly uptaken by plant. However, actual bioavailability of heavy metals by each species of plant must be determined from the plant itself. This will lead to protection and reclamation plans after the mine close. Chemical extraction is played an important role to define metal fractions, which can be related to chemical species, as well as to potentially mobile, bioavailable, or ecotoxic phase of sample. The mobile fraction is defined as the sum of amount dissolved in the liquid phase and an amount which can be transferred into the liquid phase. It has generally accepted that ecological effects of metals are related to such mobile fractions rather than the total

Sequential extraction procedures are operationally defined as methodologies that are widely applied for assessing heavy metal mobility in sediment. It is also used for the fractionation of trace metal within sediment (Quevauviller et. al., 1993 ; Ure et. al., 1993) and allows for the study of the bioavailability and behavior of metals fixed to the sediment (Pazos-Capeáns et al. 2005). BCR has been applied to characterize the metal fraction of a variety of matrices, including sediment with distinct origin, sewage sludge, amended soils and different

There are many methods to determine the different forms of metals. BCR three-step sequential extraction procedure is one of them, which was proposed by the Standards, Measurements and Test Programme (SM&T-formerly Community Bureau of Reference, BCR) of the European Union. It has been applied for the determination of trace metals (e.g., Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) binding various forms. It is strongly recommended to quantify the fractions of metal characterized by the highest mobility and availability applied for sample which the total concentration is high enough. This procedure provides a measurement of extractable metals from a reagent such as acetic acid (0.11 mol/l), hydroxlyammonium chloride (0.1 mol/l) and hydrogen peroxide (8.8 mol/l), plus ammonium acetate (1 mol/l), which are exchangeable, reducible and oxidizable metals, respectively. There are many researchers have studied about this procedure and results indicated that this procedure gave excellent recoveries for all six elements (e.g., Cu, Cr, Cd, Zn, Ni and Pb). The concentration of metal extracted by the various reagents above gave a good reproducibility on species bonded to carbonates, Fe/Mn-oxides, and the residual fraction. Characters of each fraction are simplified and shown in Fig. 5 which summary of

these fractions are given below and details were described by Serife et al. (2003).

chain. It is therefore the most dangerous form for the environment concern.

**BCR 1:** is an exchangeable, water and acid-soluble fraction*.* This fraction represents amounts of elements that may be released into the environment if the condition becomes more acidic. Acetic acid is applied for this extraction. The extracted solution includes water-soluble form, easily exchangeable (non-specifically adsorbed) form and carbonate bonding form which are vulnerable to change of pH and sorption–desorption processes. In addition, plants can uptake this fraction easily; consequently, this metal form may in turn contaminate into food

**4.2 Sequential extraction**

concentration.

industrial soil (Mossop & Davidson, 2003).

tested. It should be notified that this method is not a total digestion for most types of sample. However, it is a very strong acid digestion that may dissolve most elements that could cause environmental impact. In particular, silicate-bonding elements are unlikely to be dissolved by this procedure. About 1-2 g (wet weight) or 1 g (dry weight) sample is dissolved by repeated additions of nitric acid and hydrogen peroxide. For GFAA or ICP-MS analysis, the digested solution is reduced in volume while heating then the final volume is made to 100 ml. This method may refer to EPA 3050B. On the other hand, for ICP-AES or FLAA analyses, hydrochloric acid (HCl) is additionally poured into the previous digested solution; consequently, the solubility of some metals may be increased which may refer to EPA 3050A. After filtering, filter paper and residue are dissolved by additional HCl and then filtered again. Final digested solution is diluted to 100 ml (EPA, 2009).

A simplified procedure of EPA 3050B has been suggested as following detail. Powdered sample (e.g., soil, sediment and sludge) is mixed in 10 ml of 1:1 HNO3, then sample is covered with a watch glass. Subsequently, the sample is heated to 95±5 ºC and refluxed for 10 to 15 minutes without boiling. When the sample is allowed to cool, 5 ml of concentrate HNO3 is added and covered and refluxed for 30 minutes. If brown flumes are generated, indicating oxidation of the sample by HNO3, repeat this step (addition of 5 ml of HNO3conc.) over and over until no brown flame will be given off by the sample indicating the complete reaction with HNO3. The solution has to be evaporated to approximately 5 ml without boiling or heating at 95±5 ºC for 2 hrs. After the sample had been cooled, 2 ml of water and 30 ml of 30% H2O2 are added into the sample. In addition, 1 ml of 30% H2O2 has been continuously added with warming until the generated sample appears to have no further change. The sample has to be heated until the volume reduces to about 5 ml. Finally, the sample is then diluted to 100 ml with D.I. water after cooling. Particulates in the solution must be removed by filter (Wattman No.41). The sample is now ready for analyses of ICP or AAS.

*EPA 3051:* is an alternative to EPA 3050 procedure which is a rapid acid digestion of multielement for analysis. Leaching levels must be designed. In case, hydrochloric acid is required for digestion of certain elements; therefore EPA 3050A would be applied. Otherwise, EPA 3051 may be considered. After 0.5 g of sample is placed in a digestion vessel, 5 ml of 65% HNO3 is added and the vessel is closed with a Teflon cover. Then, the sample will be heated at 170±5ºC for approximately 5.5 minutes and remained at 170-180ºC for 10 minutes to accelerate the leaching process by microwave digestion system. Heating temperature and time may be adjusted as appropriate to each microwave system produced by various manufacturers. After cooling, the solution must be filtered by membrane filter of 0.45 μm pore diameter. Finally, the filtered solution is further diluted in 50 ml volumetric flask. The sample is now ready to be analyzed by ICP and AAS.

It has to be notified that EPA 3050 and 3051 methods usually are not total digestions; undigested materials will be remained after acid is added into the sample. However, most of the chemical bonding forms potentially environmental impact appear to have been dissolved. Silicate bonding in particular is a stable form and unlikely to be removed; it actually has no impact. Both methods are suitable for mining wastes that can be used for environmental monitoring and protection plans. In addition, Aqua Regia, mixture of hydrochloric acid and nitric acid, may also be applied for digestion. It is quite similar to EPA 3050A method. Gold can be dissolved in this mixed acid which the method is usually applied for stream sediment collected for mineral exploration.

#### **4.2 Sequential extraction**

100 Environmental Monitoring

tested. It should be notified that this method is not a total digestion for most types of sample. However, it is a very strong acid digestion that may dissolve most elements that could cause environmental impact. In particular, silicate-bonding elements are unlikely to be dissolved by this procedure. About 1-2 g (wet weight) or 1 g (dry weight) sample is dissolved by repeated additions of nitric acid and hydrogen peroxide. For GFAA or ICP-MS analysis, the digested solution is reduced in volume while heating then the final volume is made to 100 ml. This method may refer to EPA 3050B. On the other hand, for ICP-AES or FLAA analyses, hydrochloric acid (HCl) is additionally poured into the previous digested solution; consequently, the solubility of some metals may be increased which may refer to EPA 3050A. After filtering, filter paper and residue are dissolved by additional HCl and then filtered again. Final digested solution is diluted to 100 ml (EPA,

A simplified procedure of EPA 3050B has been suggested as following detail. Powdered sample (e.g., soil, sediment and sludge) is mixed in 10 ml of 1:1 HNO3, then sample is covered with a watch glass. Subsequently, the sample is heated to 95±5 ºC and refluxed for 10 to 15 minutes without boiling. When the sample is allowed to cool, 5 ml of concentrate HNO3 is added and covered and refluxed for 30 minutes. If brown flumes are generated, indicating oxidation of the sample by HNO3, repeat this step (addition of 5 ml of HNO3conc.) over and over until no brown flame will be given off by the sample indicating the complete reaction with HNO3. The solution has to be evaporated to approximately 5 ml without boiling or heating at 95±5 ºC for 2 hrs. After the sample had been cooled, 2 ml of water and 30 ml of 30% H2O2 are added into the sample. In addition, 1 ml of 30% H2O2 has been continuously added with warming until the generated sample appears to have no further change. The sample has to be heated until the volume reduces to about 5 ml. Finally, the sample is then diluted to 100 ml with D.I. water after cooling. Particulates in the solution must be removed by filter (Wattman No.41). The sample is now ready for analyses of ICP or

*EPA 3051:* is an alternative to EPA 3050 procedure which is a rapid acid digestion of multielement for analysis. Leaching levels must be designed. In case, hydrochloric acid is required for digestion of certain elements; therefore EPA 3050A would be applied. Otherwise, EPA 3051 may be considered. After 0.5 g of sample is placed in a digestion vessel, 5 ml of 65% HNO3 is added and the vessel is closed with a Teflon cover. Then, the sample will be heated at 170±5ºC for approximately 5.5 minutes and remained at 170-180ºC for 10 minutes to accelerate the leaching process by microwave digestion system. Heating temperature and time may be adjusted as appropriate to each microwave system produced by various manufacturers. After cooling, the solution must be filtered by membrane filter of 0.45 μm pore diameter. Finally, the filtered solution is further diluted in 50 ml volumetric

It has to be notified that EPA 3050 and 3051 methods usually are not total digestions; undigested materials will be remained after acid is added into the sample. However, most of the chemical bonding forms potentially environmental impact appear to have been dissolved. Silicate bonding in particular is a stable form and unlikely to be removed; it actually has no impact. Both methods are suitable for mining wastes that can be used for environmental monitoring and protection plans. In addition, Aqua Regia, mixture of hydrochloric acid and nitric acid, may also be applied for digestion. It is quite similar to EPA 3050A method. Gold can be dissolved in this mixed acid which the method is usually

flask. The sample is now ready to be analyzed by ICP and AAS.

applied for stream sediment collected for mineral exploration.

2009).

AAS.

In the environmental field, determination of total metal concentrations in mining wastes does not give sufficient information about the mobility of metals. Metals may be bound to particulate matter by several mechanisms such as particle surfaces absorption, ion exchange, co-precipitation and complexation with organic substances. For example, not all of heavy metals in soil are available for plant uptaking, only the dissolved metals content in soil solution is moveable enough for plant to absorb. Therefore, heavy metals speciation in form of water soluble fraction and free weak acid soluble fraction out of total heavy metal content are the maximum amount of heavy metals possibly uptaken by plant. However, actual bioavailability of heavy metals by each species of plant must be determined from the plant itself. This will lead to protection and reclamation plans after the mine close. Chemical extraction is played an important role to define metal fractions, which can be related to chemical species, as well as to potentially mobile, bioavailable, or ecotoxic phase of sample. The mobile fraction is defined as the sum of amount dissolved in the liquid phase and an amount which can be transferred into the liquid phase. It has generally accepted that ecological effects of metals are related to such mobile fractions rather than the total concentration.

Sequential extraction procedures are operationally defined as methodologies that are widely applied for assessing heavy metal mobility in sediment. It is also used for the fractionation of trace metal within sediment (Quevauviller et. al., 1993 ; Ure et. al., 1993) and allows for the study of the bioavailability and behavior of metals fixed to the sediment (Pazos-Capeáns et al. 2005). BCR has been applied to characterize the metal fraction of a variety of matrices, including sediment with distinct origin, sewage sludge, amended soils and different industrial soil (Mossop & Davidson, 2003).

There are many methods to determine the different forms of metals. BCR three-step sequential extraction procedure is one of them, which was proposed by the Standards, Measurements and Test Programme (SM&T-formerly Community Bureau of Reference, BCR) of the European Union. It has been applied for the determination of trace metals (e.g., Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) binding various forms. It is strongly recommended to quantify the fractions of metal characterized by the highest mobility and availability applied for sample which the total concentration is high enough. This procedure provides a measurement of extractable metals from a reagent such as acetic acid (0.11 mol/l), hydroxlyammonium chloride (0.1 mol/l) and hydrogen peroxide (8.8 mol/l), plus ammonium acetate (1 mol/l), which are exchangeable, reducible and oxidizable metals, respectively. There are many researchers have studied about this procedure and results indicated that this procedure gave excellent recoveries for all six elements (e.g., Cu, Cr, Cd, Zn, Ni and Pb). The concentration of metal extracted by the various reagents above gave a good reproducibility on species bonded to carbonates, Fe/Mn-oxides, and the residual fraction. Characters of each fraction are simplified and shown in Fig. 5 which summary of these fractions are given below and details were described by Serife et al. (2003).

**BCR 1:** is an exchangeable, water and acid-soluble fraction*.* This fraction represents amounts of elements that may be released into the environment if the condition becomes more acidic. Acetic acid is applied for this extraction. The extracted solution includes water-soluble form, easily exchangeable (non-specifically adsorbed) form and carbonate bonding form which are vulnerable to change of pH and sorption–desorption processes. In addition, plants can uptake this fraction easily; consequently, this metal form may in turn contaminate into food chain. It is therefore the most dangerous form for the environment concern.

Geochemical Application for Environmental Monitoring and Metal Mining Management 103

Sutthirat et al., 2011). Although, obvious environmental impacts have never been directly evidenced, some concerns have been raised by some sectors. Waste rocks from particular mining pit and tailings from tailing pond were characterized based on their geochemistry. Apart from AMD assessment, investigation of the geochemical characteristics, including their heavy metal contents and the potential of each of these metals to leach, is the first step to develop the best practice for environmental protection. Results of these studies are

Six types of waste rocks including volcanic clastic, porphyritic andesite, andesite, silicified tuff, silicified lapilli tuff and sheared tuff were collected under supervision of mining geologists. Whole-rock geochemistry, particularly their major compositions (rock powders analyzed by XRF), can be used to differentiate these rocks clearly as shown in Fig. 6; moreover, some trace elements and rare earth elements, using EPA 3052 digestion and analyzed by ICP-OES, were applied for determination of their geneses and evolutions (Sutthirat et al., 2011). Although, these may not be related to environmental aspect they should be initial investigation, at least to distinguish types of waste rock clearly before

Subsequently, nitric leaching of these rocks was experimented following the EPA 3051 method. Amounts of leachable elements were then compared with the total digestion. Almost linear relationship between both forms of at least eight heavy metals was observed (Fig. 7). Except for As, the nitric recoverable levels of the heavy metals were slightly lower than the total concentrations. In conclusion, the maximal leaching potential (%) of these heavy metals were calculated as 30.5 - 63.2% for As, 80.4 - 81.9% for Ag, 0 - 92. 8% for Cd, 63.6 - 87.6% for Co, 91.1 - 100% for Cu, 87.9 - 99.7% for Mn, 85.3 - 93.5% for Ni and 0 - 82.8% for Pb, respectively. Three of the six rock types, i.e., porphyritic andesite, silicified tuff and silicified lapilli tuff, are of the greatest concern because they contain a high heavy metal load (proportional concentration) each with a high maximal acid leaching potential. In the worst case scenario, over 50% of the total heavy metal load would be leached by a very strong acid passing through these rocks and impacting the environment, consequently; however, this

Acid Base Accounting (ABA) and Net Acid Generation (NAG) tests were applied for evaluation of acid generation potential of these waste rocks (Changul et al., 2010a). Experimental results reveal silicified lapilli tuff and shear tuff are potentially acid forming materials (PAF); on the other hand, the other rocks, i.e., volcanic clastic, porphyritic andesite, andesite and silicified tuff are potentially non-acid-forming (NAF). Among these west rocks, shear tuffs appear to be the most impact to the environment, based on their highest potential of acid forming. Therefore, great care must be taken and focused on this rock type. Finally, they also finally concluded that AMD generation from some waste rocks may be occur a long time after mine closure due to the lag time of the dissolution of acidneutralizing sources. In addition, environmental conditions, particularly the oxidation of sulphides which is usually activated by oxygen and water, are the crucial factor. Consequently, waste rock dumping and storage must be planned and designed very well that will lead to minimization of risk from AMD generation in the future. Surface management system and addition storage pound should be installed to control the over flood and runoff direction away from the rock waste dump. Environmental monitoring plan

summarized below.

further testing program will be designed.

case is unrealistic and unlikely to happen.

including water quality should be also put in place.

**5.1 Waste rocks**

**BCR 2:** is a reducible fraction. It theoretically represents contents of metals bond to iron and manganese oxides/hydroxides. These oxides/hydroxides are excellent cleaners of some trace metals that have been weathered and transported from the initial sources. They are thermodynamically unstable under anoxic conditions (Panda et al., 1995). Hydroxylamine hydrochloride is used for this extraction. Levels of extraction in this step should be effected by efficiency and selectivity of reagents used in the previous BCR 1. Therefore, this fraction may be too high if the carbonates have not been completely dissolved or too low if parts of the iron and manganese hydroxides have already been extracted.

**BCR 3:** is an oxidisable fraction or organic bound. Hydrogen peroxide and ammonium acetate are applied for this extraction. Metals can bond to various forms of organic matter. The complexities of natural organic matter are well recognized, as the phenomenon of bioaccumulation in certain living organisms. These organic matters can be degraded naturally under oxidizing conditions in waters leading to release of soluble metals. An oxidizing condition may have occurred during exposure to the atmosphere either by natural or artificial processes.

**BCR 4**: is defined as final residue*.* The final fraction can be calculated as the difference between metal contents extractable from Aqua Regia method (using nitric and hydrochloric acids) and metal contents released from the previous sequential extractions. Metal contents of all three previous fractions are considerable as more mobile and bioavailable than the residual fractions (Tack & Verloo, 1995; Ma & Rao, 1997). The residual metals appear to have relation with mineral structures that are the most difficult to be extracted (Kersten & Förstner, 1991).

Fig. 5. Chemical fractions of metals in sediments and their characters.

#### **5. Case study in Thailand**

Geochemical investigations as mentioned above were applied to the environmental aspects of Akara Gold mine in Pichit Province of Thailand (i.e., Changul et al., 2010 a and b; Sutthirat et al., 2011). Although, obvious environmental impacts have never been directly evidenced, some concerns have been raised by some sectors. Waste rocks from particular mining pit and tailings from tailing pond were characterized based on their geochemistry. Apart from AMD assessment, investigation of the geochemical characteristics, including their heavy metal contents and the potential of each of these metals to leach, is the first step to develop the best practice for environmental protection. Results of these studies are summarized below.

#### **5.1 Waste rocks**

102 Environmental Monitoring

**BCR 2:** is a reducible fraction. It theoretically represents contents of metals bond to iron and manganese oxides/hydroxides. These oxides/hydroxides are excellent cleaners of some trace metals that have been weathered and transported from the initial sources. They are thermodynamically unstable under anoxic conditions (Panda et al., 1995). Hydroxylamine hydrochloride is used for this extraction. Levels of extraction in this step should be effected by efficiency and selectivity of reagents used in the previous BCR 1. Therefore, this fraction may be too high if the carbonates have not been completely dissolved or too low if parts of

**BCR 3:** is an oxidisable fraction or organic bound. Hydrogen peroxide and ammonium acetate are applied for this extraction. Metals can bond to various forms of organic matter. The complexities of natural organic matter are well recognized, as the phenomenon of bioaccumulation in certain living organisms. These organic matters can be degraded naturally under oxidizing conditions in waters leading to release of soluble metals. An oxidizing condition may have occurred during exposure to the atmosphere either by natural

**BCR 4**: is defined as final residue*.* The final fraction can be calculated as the difference between metal contents extractable from Aqua Regia method (using nitric and hydrochloric acids) and metal contents released from the previous sequential extractions. Metal contents of all three previous fractions are considerable as more mobile and bioavailable than the residual fractions (Tack & Verloo, 1995; Ma & Rao, 1997). The residual metals appear to have relation with mineral structures that are the most difficult to be extracted (Kersten &

the iron and manganese hydroxides have already been extracted.

Fig. 5. Chemical fractions of metals in sediments and their characters.

Geochemical investigations as mentioned above were applied to the environmental aspects of Akara Gold mine in Pichit Province of Thailand (i.e., Changul et al., 2010 a and b;

or artificial processes.

Förstner, 1991).

**5. Case study in Thailand**

Six types of waste rocks including volcanic clastic, porphyritic andesite, andesite, silicified tuff, silicified lapilli tuff and sheared tuff were collected under supervision of mining geologists. Whole-rock geochemistry, particularly their major compositions (rock powders analyzed by XRF), can be used to differentiate these rocks clearly as shown in Fig. 6; moreover, some trace elements and rare earth elements, using EPA 3052 digestion and analyzed by ICP-OES, were applied for determination of their geneses and evolutions (Sutthirat et al., 2011). Although, these may not be related to environmental aspect they should be initial investigation, at least to distinguish types of waste rock clearly before further testing program will be designed.

Subsequently, nitric leaching of these rocks was experimented following the EPA 3051 method. Amounts of leachable elements were then compared with the total digestion. Almost linear relationship between both forms of at least eight heavy metals was observed (Fig. 7). Except for As, the nitric recoverable levels of the heavy metals were slightly lower than the total concentrations. In conclusion, the maximal leaching potential (%) of these heavy metals were calculated as 30.5 - 63.2% for As, 80.4 - 81.9% for Ag, 0 - 92. 8% for Cd, 63.6 - 87.6% for Co, 91.1 - 100% for Cu, 87.9 - 99.7% for Mn, 85.3 - 93.5% for Ni and 0 - 82.8% for Pb, respectively. Three of the six rock types, i.e., porphyritic andesite, silicified tuff and silicified lapilli tuff, are of the greatest concern because they contain a high heavy metal load (proportional concentration) each with a high maximal acid leaching potential. In the worst case scenario, over 50% of the total heavy metal load would be leached by a very strong acid passing through these rocks and impacting the environment, consequently; however, this case is unrealistic and unlikely to happen.

Acid Base Accounting (ABA) and Net Acid Generation (NAG) tests were applied for evaluation of acid generation potential of these waste rocks (Changul et al., 2010a). Experimental results reveal silicified lapilli tuff and shear tuff are potentially acid forming materials (PAF); on the other hand, the other rocks, i.e., volcanic clastic, porphyritic andesite, andesite and silicified tuff are potentially non-acid-forming (NAF). Among these west rocks, shear tuffs appear to be the most impact to the environment, based on their highest potential of acid forming. Therefore, great care must be taken and focused on this rock type. Finally, they also finally concluded that AMD generation from some waste rocks may be occur a long time after mine closure due to the lag time of the dissolution of acidneutralizing sources. In addition, environmental conditions, particularly the oxidation of sulphides which is usually activated by oxygen and water, are the crucial factor. Consequently, waste rock dumping and storage must be planned and designed very well that will lead to minimization of risk from AMD generation in the future. Surface management system and addition storage pound should be installed to control the over flood and runoff direction away from the rock waste dump. Environmental monitoring plan including water quality should be also put in place.

Geochemical Application for Environmental Monitoring and Metal Mining Management 105

Fig. 7. Correlations between the total and nitric-leachable concentrations of eight heavy metals from various waste rocks from Akara Gold Mine, Thailand, showing linear

regression relation

#### **5.2 Tailings**

Tailing samples were also systematically collected and analyses for chemical composition and mineral assemblages (Changul et al., 2010b). Consequently, these tailings have little differences of chemical compositions quantitatively from place to place but their mineral assemblages could not be clearly distinguished. They suggested that these end-processed tailings were mixed between high and low grade ores which may have the same mineral assemblages. Variation of chemical composition appeared to have been modified slightly by the refining processes that may be somehow varied in proportion of alkali cyanide and quick lime in particular. Moreover, content of clay within the ore-bearing layers may also cause alumina content in these tailings, accordingly. Total heavy metals in the tailing samples were analyzed using solution digested following the EPA 3052 method. Toxic elements including Co, Cu, Cd, Cr, Pb, Ni, Zn etc. range within the Soil Quality Standards for Habitat and Agriculture of Thailand. Only Mn contents are higher than the standard.

Potential of acid generation of these tailings was tested on the basis of Acid-Base Accounting (ABA) and Net Acid Generation (NAG) tests. Tailing samples appear to have high sulfur content but they also gave high acid neutralization capacity; therefore, they were generally classified as a non-acid forming (NAF) material. However, they still suggested that oxidizing process and dissolution should be protected with great care. Clay layer may be placed over the pound prior to topping with topsoil for re-vegetation after the closure of the mining operation. Native grass is suitable for stabilization of the surface and reduction of natural erosion. In addition, water quality should also be monitored annually.

Mining and environmental management programs usually require considerable data for best practice of mining operation and environmental monitoring. The management techniques include the sampling and classification of waste rock types.

Fig. 6. Alkali-silica discrimination diagram of Le Bas et al. (1986) applied for whole-rock geochemical analyses of waste rocks from the Akara Gold Mine, Thailand

Tailing samples were also systematically collected and analyses for chemical composition and mineral assemblages (Changul et al., 2010b). Consequently, these tailings have little differences of chemical compositions quantitatively from place to place but their mineral assemblages could not be clearly distinguished. They suggested that these end-processed tailings were mixed between high and low grade ores which may have the same mineral assemblages. Variation of chemical composition appeared to have been modified slightly by the refining processes that may be somehow varied in proportion of alkali cyanide and quick lime in particular. Moreover, content of clay within the ore-bearing layers may also cause alumina content in these tailings, accordingly. Total heavy metals in the tailing samples were analyzed using solution digested following the EPA 3052 method. Toxic elements including Co, Cu, Cd, Cr, Pb, Ni, Zn etc. range within the Soil Quality Standards for Habitat and Agriculture of Thailand. Only Mn contents are higher than the standard. Potential of acid generation of these tailings was tested on the basis of Acid-Base Accounting (ABA) and Net Acid Generation (NAG) tests. Tailing samples appear to have high sulfur content but they also gave high acid neutralization capacity; therefore, they were generally classified as a non-acid forming (NAF) material. However, they still suggested that oxidizing process and dissolution should be protected with great care. Clay layer may be placed over the pound prior to topping with topsoil for re-vegetation after the closure of the mining operation. Native grass is suitable for stabilization of the surface and reduction of

natural erosion. In addition, water quality should also be monitored annually.

techniques include the sampling and classification of waste rock types.

Mining and environmental management programs usually require considerable data for best practice of mining operation and environmental monitoring. The management

Fig. 6. Alkali-silica discrimination diagram of Le Bas et al. (1986) applied for whole-rock

geochemical analyses of waste rocks from the Akara Gold Mine, Thailand

**5.2 Tailings**

Fig. 7. Correlations between the total and nitric-leachable concentrations of eight heavy metals from various waste rocks from Akara Gold Mine, Thailand, showing linear regression relation

Geochemical Application for Environmental Monitoring and Metal Mining Management 107

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