*2.4. Human Health Risk Assessment*

The human health risk assessment is the basis for controlling groundwater pollution and ensuring a safe drinking water supply [49,60–62]. Groundwater can affect human health through various exposure pathways, the most common of which are drinking water intake and dermal contact [63]. The model recommended by the Ministry of Ecology and Environment of the P.R. China [64] based on the United States Environmental Protection Agency models [65] was adopted in this study. There are many agricultural and industrial production activities in the study area. Therefore, representative pollutants F−, nitrogen (NO3-N, NO2-N, NH4-N), and PTEs (Fe, Mn, Hg, As, Cd, Cr6+, and Pb) are selected as the parameters of risk assessment. Due to differences in the physiology of males, females, and children, this study separately evaluated the health risks of oral intake and dermal intake.

The non-carcinogenic risk through drinking water intake is calculated as follows [60,63]:

$$\text{Intake}\_{\text{oral}} = \frac{\mathbb{C} \times \text{IR} \times \text{EF} \times \text{ED}}{\text{BW} \times \text{AT}} \tag{5}$$

$$\text{HQ}\_{\text{oral}} = \frac{\text{Intake}\_{\text{oral}}}{\text{RfD}\_{\text{oral}}} \tag{6}$$

The non-carcinogenic risk through dermal contact is expressed as follows [42]:

$$\text{Intake}\_{\text{demand}} = \frac{\text{DA} \times \text{EV} \times \text{SA} \times \text{EF} \times \text{ED}}{\text{BW} \times \text{AT}} \tag{7}$$

$$\mathbf{DA} = \mathbf{K} \times \mathbf{C} \times \mathbf{t} \times \mathbf{CF} \tag{8}$$

$$\text{SA} = \text{239} \times \text{H}^{0.417} \times \text{BW}^{0.517} \tag{9}$$

$$\text{HQ}\_{\text{demand}} = \frac{\text{Intake}\_{\text{demand}}}{\text{RfD}\_{\text{demand}}} \tag{10}$$

$$\text{RfD}\_{\text{demand}} = \text{RfD}\_{\text{oral}} \times \text{ABS}\_{\text{gi}} \tag{11}$$

where Intakeoral, Intakedermal, HQoral, HQdermal, RfDoral, and RfDdermal represent the chronic daily dose via ingestion and dermal contact (mg/(kg day)), the hazard quotient through oral and dermal exposure pathways, reference dose for oral and dermal contact pathways (mg/(kg day)), respectively. C, DA, SA, and ABSgi are the pollutant concentration of groundwater (mg/L), exposure dose (mg/cm2 ), skin surface area (cm2 ), and gastrointestinal absorption factor, respectively. The definitions and values of other parameters are shown in Tables 1 and 2.

**Table 1.** Definition and values of key parameters for human health risk assessment.

a refer to [64]; b refer to [66]; c refer to [67]; d refer to [63].

**Table 2.** The values of RfD, ABSgi, and SF for different ions.

The total non-carcinogenic risks are calculated as follows [1,29,45]:

$$\rm{HQ}\_i = \rm{HQ}\_{\rm{oral}} + \rm{HQ}\_{\rm{dermal}} \tag{12}$$

$$\text{HI}\_{\text{total}} = \sum\_{\mathbf{i}=1}^{\text{n}} \text{HQ}\_{\mathbf{i}} \tag{13}$$

where HQ is the non-carcinogenic hazard quotient and HI is the hazard index. i represents the risk assessment parameters. When the value of HQ and HI is less than 1, it is safe for human health. HI > 1 indicates unacceptable risk, and residents are exposed to noncarcinogenic risks [60,64].

In addition to non-carcinogenic risk, As, Cd, and Cr6+ can also create carcinogenic risks for humans [7,41]. The carcinogenic risk through drinking water intake and dermal contact is calculated as follows:

$$\text{CR}\_{\text{oral}} = \text{Intake}\_{\text{oral}} \times \text{SF}\_{\text{oral}} \tag{14}$$

$$\text{CR}\_{\text{demand}} = \text{Intake}\_{\text{demand}} \times \text{SF}\_{\text{demand}} \tag{15}$$

$$\text{SF}\_{\text{demand}} = \frac{\text{SF}\_{\text{oral}}}{\text{ABS}\_{\text{g}^{\text{l}}}} \tag{16}$$

$$\text{CR}\_{\text{total}} = \text{CR}\_{\text{oral}} + \text{CR}\_{\text{demand}} \tag{17}$$

where CR denotes the carcinogenic risk. SF is the slope factor for the carcinogenic contaminants (mg/(kg day))−1 . The SForal values for As, Cd, and Cr6+ are shown in Table 2. The average time (AT) for carcinogenic risk is set at 27,740 days for both adults and children, as the harm to human health caused by cadmium, chromium, and arsenic will last a lifetime [64]. The acceptable limit for CR is 1 × 10−6 .


**10. References**

[1] Weng W. Chow and Stephen W. Koch, Semiconductor Laser: Fundamentals (Berlin, Springer, 1999), 1.

4REs 3REs

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

InAs0.1Sb0.9/GaAs0.1Sb0.9/Al0.1Ga0.9As

Time (s)

The progress towards SOAs, and then QD-SOAs, is reviewed. The importance of Sb-based structures is illuminated. To see the effect of QD-SOA layers, a REs for QD, WL and SCH layers are solved numerically. This make us specify gain-input power relation for Sb-based QD-SOAs and then examine layers dynamics. Both QD and SCH layers are shown to have an importance in the static characteristics due to their considerable effect in structure confinement. WL is shown to affect carrier dynamics especially in the ES and GS. Global quasi-Fermi energy (which included SCH, WL, QD ES and QD GS) is shown to be important in the explanation of results. At all cases, the inclusion of the SCH in the REs is shown to be

We acknowledge our indebtedness to Prof. Mohammed Jasim Betti (Dept. of English, College of Education, Thi-Qar University) for proofreading the language of this work.

[1] Weng W. Chow and Stephen W. Koch, Semiconductor Laser: Fundamentals (Berlin,

Fig. 8. A comparison between three- and four-REs system for (a) WL carrier density, (b) ES and (c) GS occupation probabilities for InAs.1Sb.9/GaAs.1Sb.9/Al.1Ga.9As QD-SOA.

0

**8. Conclusions**

essential.

**9. Acknowledgment**

Springer, 1999), 1.

**10. References**

0.1

0.2

0.3

0.4

Carrier Occupation Probability of GS

0.5

0.6

(c)

0.7

0.8

x 10-10

[18] P. Mock and others, "MOVPE grown self-assembled Sb-based quantum dots

[19] M. Mehta, A. Jallipalli, J. Tatebayashi, M. N. Kutty, A. Albrecht, G. Balakrishnan, L.

[21] H. Al-Husseini, Amin H. Al-Khursan, S. Al-Dabagh, "III-nitride QD lasers", Open

[22] Wei Zhang and M. Razeghi, "Antimony-Based Materials forElectro-Optics," in

[23] Shun-Lien Chuang, Physics of optoelectronic devices, (New York, J. Willy & sons,

Emitting at 1.65 μm," IEEE Phot. Tech. Lett. 19, no. 13 (2007) 1628. [20] Amin H. Al-Khursan, M. Al-Khakan, K. Al-Mossawi, "Third-order non-linear

Fundamentals and Applications 7, no. 3 (2009): 153.

Steiner, (Boston, Artech House, 2004) 229.

(2000): 209.

1995), 708.

Nanosci. J. 3, (2009): 1.

assessed by means of AFM and TEM," IEE Proc.-Optoelectronics 147, no. 3

R. Dawson, and D. L. Huffaker, "Room-Temperature Operation of Buffer-Free GaSb–AlGaSb Quantum-Well Diode Lasers Grown on a GaAs Platform

susceptibility in a three-level QD system," Photonics and Nanostructures –

Semiconductor nanostructures for optoelectronic applications, ed. Todd


**4.4 Stream restoration**

In many instances, pollutant source reductions and built SWM infrastructure may not be enough to recapture watershed integrity because of stream channel alteration. In these instances, restoring stream channels is now a preferred goal. In these designs, hydrology, sediment transport and watershed processes that have fundamentally changed are incorporated into a new channel design [70]. In these designs, streambank stabilization, restoration of the stream channel and reestablishment of riparian vegetation are the areas of focus. To stabilize banks, jetties, tree revetments, rock vanes, rock toes, retaining walls and gravel banks are used [71]. While retaining walls and gravel banks provide good stability they are expensive. Jetties may not provide the same level of protection but are the most cost effective measure and provide a more natural look to the restoration. Tradeoffs exist between appearance, effective stabilization and costs.

To rehabilitate the stream channel, regional curve dimensions, planform pattern, and grade control structures are developed [72]. Grade control structures hold the vertical elevation of the stream constant preventing vertical downcutting. Planform pattern creates an alignment of the stream channel to resemble meanders typical for the regional landscape. Proper channel width and depth are created from a "best-fit" consideration using the bankfull channel dimensions of similar reference stream from within the drainage area.

Unfortunately, there is considerable scientific evidence that instream restoration in USA and Europe has shown very limited success [73–77]. Storm events that exceed bankfull have fundamentally changed restoration design reducing expected performance [78]. Restoration of features (stormwater ponds, riparian vegetation) outside the stream channel have shown some improvement but well under expectations based on investment [79]. Prevention remains the single most effective

**Figure 2.** *Channelized urban river in need of stream restoration.*

restoration technique. Lack of effective measure for restoration may be sensitive to time scales as full recovery may take over 15 years to be realized [80].

The how and where to restore is difficult to decide. Urban land is expensive and the best areas may be privately owned and unwelcoming. Projects are driven by available land to municipalities and public sentiments rather than effectiveness in bringing about the best project restoration outcomes [81]. So because of the expense and limited measured effectiveness restoration projects are currently under debate. It appears that good channel restoration projects are best when integrated into multi management efforts including protection of existing good quality stream sections, reducing stormwater flow, controlling sewage overflows upgrading sewage treatment facilities (**Figure 2**) [82].

#### **4.5 Sediment management**

Managing sediment in urban stream channels may be paramount for improving urban river systems. Sediment moves through these systems in what can be characterized as the "urban sediment cascade" [83]. In this cascade, sediment is generated from two primary sources; first roads and impervious surfaces and then the bed of the aquatic system. As the sediment flows through this urban cascade it mixes with multiple contaminants such as metals [84] and microplastics [85]. This sediment flows from parts of the urban landscape such as street surfaces, pot holes, storm sewers, ditches and docks eventually entering rivers and lakes. This phenomenon makes every storm event a polluting event with the concentration of contaminates dependent upon the storm intensity.

Once in the stream bed this sediment may accumulate for extended periods of time. Evidence suggests movement of sediment fractions larger than the median size of the bed surface material is rare and occurs only at relatively high flows [86]. Such flows may occur once every few years and the movement might not last more than a few hours. This further suggests years of accumulation of contaminated sediment may be severe and pose a possible health risk [87]. Removal of dams as part of an overall restoration strategy to improve fish passage and sediment flow downstream may in actuality be counterproductive toward restoration goals as beneficial evidence of this practice is highly experimental [88, 89]. Prevention or clean up through practices such as street sweeping may be a better management strategy [90].

#### **4.6 Citizen science and education**

The importance of citizen science protecting water quality [91] is becoming more widespread and may be integral to restoring these systems. It bridges the gap between regulators and the public energizing citizens living in urban areas impacted by poor river quality. Citizens can be trained to complete essential tasks, are affordable and can generate good data when verified [92]. Programs such as the The Izaak Walton League's Save Our Streams [93] builds an army of volunteers through training and information to monitor our waterways. This program serves as an intermediary successfully uncovering problems and urging local leaders to take action. These types of programs can even transcend data collection and scientific analysis moving those involved toward a greater sense of place in the watershed [94]. This can further the idea of watershed protection and lead to real policy change.

Education is the other effort underway to secure river protection. Theoretically, an educated public will hold regulators and developers responsible for their actions. Programs such as Global Rivers Environmental Education Network (GREEN)

educates global citizens about water quality problems [95]. Education based curriculum teaching stormwater principles in schools educates future generations about the problems rivers are facing [96]. Such programs are productive. But education is complex. People formulate perceptions about the environment using various levels of experience, normative influences, temporal discrepancies and attitude-behavior measures [97]. Why should people care or why be involved? Answers to these questions are extremely diverse, complex, and poorly understood. The furtherance of educational understanding can only enhance opportunities for improvement.


7. Conclusion

The heat and mass transfer effect of a thin film over the extended surface of a cylinder has been explored in the recent research. The spray phenomenon has been studied in the form of velocity, temperature, concentration, and pressure distribution profiles, respectively. The similarity transformation has been used to alter the governing equations into the set of nonlinear differential equations. The solution of the problems has been obtained through the homotopy analysis method (HAM). The impact of the embedded parameters has been examined and discussed. The outcomes of the recent study have been pointed out as:


**5. Optimization of the dyeing processes to reduce the environmental impact of the textile industry**

The search and development of new methods to promote the treatment of effluents from the textile industry with a maximum of efficiency of the process of decolorization and / or re‐ moval of these compounds present in the medium can trigger further damage human health and the environment is fundamental importance. The understanding of the composition of waste generated is extremely significant to develop these methods of treatment due to the high complexity by virtue of huge number of compounds which are added at different stages of the dyeing fabrics.

Environmental problems with used dye baths are related to the wide variety of different components added to the dye bath, often in relatively high concentrations. In the future, many of textile factories will face the requirement of reusing a significant part of all incom‐ ing freshwater because traditionally used methods are insufficient for obtaining the required water quality.

However, due to dwindling supply and increasing demand of water in the textile industries, a better alternative is to attempt to further elevate the water quality of wastewater effluent from a secondary wastewater treatment plant to a higher standard for reuse. Thus far very little attention has been paid to this aspect [105].

Therefore, the investment in the search for methodologies to more effective treatment of these effluents can be much smaller than that spent in tertiary treatment to remove these products in low level of concentrations and in the presence of much other interference. This requires action that the cost / benefit are reviewed and the development of new techniques for wastewater treatment capable of effective removal of these dyes is intensified and made economically viable [105,106].

An alternative to minimize the problems related to the treatment of textile effluents would be the development of more effective dye that can be fixed fiber with higher efficiency de‐ creasing losses on tailings waters and reducing the amount of dye required in the dyeing process, reducing certainly improve the cost and quality of the effluent.