**5. Characterization ceramic**

The *Pb*0*:*95*Sr*0*:*05ð Þ *Zr*0*:*53*Ti*0*:*47 *O*3 þ *x*%*wtCr*2*O*3 is a ferroelectric ceramic powder, and it is possible to characterized by x-ray and electric measures [8, 16]. The EPR measures were taking at Biophysics and Magnetic Measure National Polytechnic Institute Laboratory using an EPR JEOL JES-RE3X spectrometer, **Figure 7**.

**Figure 7.** *EPR JEOL spectrometer [23].*

#### **Figure 8.**

*General diagram for paramagnetic resonance spectrometer (EPR) that consist of magnetic system (electromagnet, modulation coils, magnet power supply and field scan drive), field modulation system (power amplifier, 100 kHz oscillator), cavity system (resonant cavity with sample, iris and the T-magic system), microwave source system (klystron power supply, automatic frequency control, etc.) and detection system (detector crystal, 100 kHz signal detector, 100 kHz signal amplifier, oscilloscope, computer and data bank; and display of the spectrum) [12].*

The temperature measures were at 300K and 77K. The power potency was varied from 1 mW until 40 mW [17–23], at 9.45GHz microwave frequency at X-band. The lead zirconate titanate was doped with five percentages of Cr of 0%, 1%, 2%, 4% and 5%, we called the samples 0, 1, 2, 4 and 5 respectively.

The spectrometer is connected to workstation ES-PRIT to HP-9000 computer with a converter analogic digital target (A/D). The programing package performs acquisition, procession and simulation data [23, 24]. The block diagram typical X-band EPR spectrometer employing 100KHz phase sensitive detection is shows in **Figure 8** [12, 23].

### **6. Results and discussions**

The X-rays and electric measured was published by F. Calderon, and Yañez, et al. [8], the x-rays spectra are show in **Figure 9** for samples 4 and 5. The X-rays program fixed the *Pb Zr* ð Þ 0*:*44*Ti*0*:*56 *O*3 compound and this do not detect secondary phases. The quantity of chromium is not enough for be detected by X-rays measures, because the limit detection is 5% of the element. About electric measured, when the chromium concentration varies from sample 1 to 5, the Curie's temperature value increases. The Cr substitution causes a tetragonal distortion field to the tetrahedral symmetry structure causes energy splitting effect by zero splitting field [12]. Due to the *Cr*3þ quantity is more than *Ti*4þ or *Zr*4þ quantities, the system tetragonality be modified and the grain size is increased [8]. The Curie's temperature varies slightly, and the energy activation is below and above to the transition.

#### **Figure 9.**

*X-rays for 4 and 5 samples that corresponds to perovskite structure or tetrahedral symmetry from Pb (Zr0.44Ti0.56)O3.*

The presence of chromium determined by EPR guaranteed an oxygen or hold vacancy mechanism, also this effect was confirmed by Yañez, et al. [8].


**2.7. Calcium-activated chloride channels in breast cancer**

Calcium-activated chloride channel anoctamin 1 (ANO1) was demonstrated to be highly expressed in breast cancer cell lines and primary tumors and was considered to be a predictive factor for the disease degree and poor prognosis [102]. ANO1 activation was demonstrated to be done via the EGF receptor and calmodulin-dependent protein kinase II signaling, and its expression was associated with tumor cell survival [102].

An extensive clinical study including 431 patients with invasive ductal breast carcinoma and 46 patients with fibroadenoma analyzed the expression of anoctamin 1 (Ano1, TMEM16A), one of the members in the Ano family [103]. The study identified a correlation between Ano1 overexpression and the good prognosis in patients with lower clinical stage (stage I or II) of the breast cancer or in patients with triple-negative breast cancers [103].

**3. Calcium signaling pathways as pharmacological targets in breast**

cium concentration in both oscillating and nonoscillating MDA-MB-231 cells [78].

charged liposomes and to target only highly metastatic breast cancer cells.

**3.2. Voltage-gated calcium channels as pharmacological targets in breast cancer**

reduced by 90% the triple-negative MDA-MB-231 and MCF7 breast cancer cells [76].

Tetrodotoxin (TTX), a blocker of voltage-gated sodium channels (VGSCs), was demonstrated to diminish the number of oscillating MDA-MB-231 breast cancer cells and to reduce the amplitude and the frequency of the Ca2+ oscillations (i.e., spontaneous calcium transients) in the same cells [78]. While TTX had no effect on the basal calcium level in nonoscillating MDA-MB-231

Previous studies have demonstrated that the blockade of VGSCs inhibits the invasion of endocrine-resistant breast cancer cells [119]. It is very interesting the correlation between the blockade of VGSCs and the reduction of spontaneous calcium oscillations. Therefore, considering that only metastatic cells are characterized by spontaneous calcium transients in comparison with low-metastatic or normal cells, a possible therapeutic strategy would be to diminish calcium transients by applying targeted pharmacological agents against VGSCs. An interesting approach would be to encapsulate voltage-gated sodium channels antagonists in

1 mM Mn2+ and 0.1 mM Ni2+ ions blocked the fast activation and inactivation of the T-type

Low doses (10–20 μM) of verapamil, an antagonist of voltage-gated calcium channels, blocked the growth of triple-negative MDA-MB-231 breast cancer cells, while high doses (100 μM)

Cav3.2 channels were demonstrated to play an important role in the mechanisms involved in chemoresistance. To date, trastuzumab resistance was demonstrated to be correlated with high mRNA Cav3.2 levels in SKBR3 breast cancer cells [120]. Patients with estrogen receptor-positive breast cancer that had a poor clinical outcome presented a significant Cav3.2 upregulation [120]. Moreover, patients with HER2-positive breast cancer presented a positive correlation between the Cav3.2 expression and patient survival upon chemotherapy [120].

TRP channels have been demonstrated to be actively involved in the development and progression of breast cancer. Therefore, finding efficient strategies for blocking-/silencingspecific TRPs in breast cancer cells might represent a good strategy to diminish the breast

conditions augmented the intracellular cal-

Alterations in Calcium Signaling Pathways in Breast Cancer

http://dx.doi.org/10.5772/intechopen.80811

177

**3.1. Calcium oscillations as pharmacological targets in breast cancer**

breast cells, when applied in high extracellular K<sup>+</sup>

calcium currents in MCF7 breast cancer cells [79].

**3.3. TRP channels as pharmacological targets in breast cancer**

cancer progression.

**cancer**

Integrating these results, it is still premature to evaluate if Ano1 is or is not a predictive factor in good/poor prognosis in breast cancer patients, and if it is a suitable pharmacological target. It would be very useful to have more insights into the cellular mechanisms related to Ano1 activation. In our opinion, a possible scenario would be that the opening of calcium-activated chloride channels induces chloride efflux, membrane depolarization followed by the calcium influx through VGCCs. The high level of expression of calcium-activated chloride channels in breast cancer cells might be correlated with the tendency of these cells to be more depolarized with respect to the normal surrounding cells. However, this scenario would explain only the clinical data showing the association between Ano1 overexpression and the poor prognosis in patients with breast cancer.


**2.1.1 Description of study area**

The Čenkov plain is situated in the eastern part of the Danubian lowland, west apart from Štúrovo town. It is the fluvial plain of the Danube, which borders in the south on a 23 kilometre long river section between RK 1722 and 1745 and in the north in an arc stretching across the terrace platform, where on its boundary lies the Moča village, the Búč village, the Júrsky Chlm village, the Mužla village and the Obid village. The fluvial plain is from 2.5 km up to 6 km wide and has an overall area of 66 km2. Its surface is flat. The heights of the terrain vary from 106 up to 108 m a.s.l. The lowest-situated section under the terrace is on height level 105m a.s.l. and the highest situated section in the Čenkov wood is on the middle of the area 108 – 110m a.s.l. (Fig. 1 and 2).

Change of Groundwater Flow Characteristics After Construction of the

even in singular cases up to 1000 mm of precipitation.

**<IP_ADDRESS> Hydrogeology and geology**

Waterworks System Protective Measures on the Danube River – A Case Study in Slovakia 57

indeed the warmest but also has the driest locality. In a series of long-term observations, the lowest annual precipitation totals vary in terms of 300 – 400 mm and minimum monthly precipitation totals in particular months do not even reach (except for July) 5 mm precipitation, whereupon significant dry periods are more often in summer half-year than in winter half-year. The lowest July precipitation totals do not drop under 10 mm. On the other hand wet (precipitation) periods are lasting here mostly from 18 to 20 days, and their appearance is relatively more rare than the appearance of dry periods and it occurs mostly in spring and autumn periods. The highest annual precipitation totals could reach 900 mm,

The Danube fluvial plain at observed river sections is built by sediment deposits of the Danube River, where their thickness varies irregularly between 5 - 12 m and the most frequent thicknesses are between 6 - 9 m. Gravel and sand dominate soil layers, which are in the highest part covered by alluvial loams. Gravel–sand fillings of the Danube fluvial plain's

Fig. 3. Hydrogeological profile 1-1 (400x exceeded). Comments: 1-young Pleistocene blown sands, 2-medium to smooth sands, 3-sandy gravel to rough sands with gravel, 4-downhill loamy sediments along upper terrace step, 5-dusty to loamy sands, eventually dusty – sandy loams, 9- marking of the tertiary base surface, 10-groundwater level on 29 Sept.1954, 11-the

It is possible to observe their partial subtilization in longitudinal profiles of gravel sand alluvia (Fig. 3 and 4) in the Danube direction, although the appearance of heavier gravel layers is possible in the whole profile. The left edge of the Danube's fluvial plain is lined by

highest groundwater level in years 1954 – 1956 (Duba, 1964)

bed in this section belong to Würm, and the cover of sandy loam is Holocene.

Fig. 1. Geographical situation of the Čenkov plain

Fig. 2. Water management map of the Čenkov plain


3.3.1. Analysis of Landscape Pattern Index Change on Patch Type Scale

As shown in Figure 5, the PD of the cultivated land is the largest among all land types, with a mean value of 0.24. This shows that the cultivated land has a profound influence on the landscape pattern of the Nanming River Basin. From 2000 to 2010, the PD of the forest, cultivated land, and constructed land increased. However, the PD of grassland showed a decreasing trend from 2010 to 2020. Except for the constructed land, the PD of the forest, constructed land, grassland, and water showed an increasing trend. The human ecological footprint has had a greater impact on the forest and cultivated landscapes over the past 20 years. Moreover, their ecological processes were more active, in which the expansion of the constructed landscapes was reasonably restrained during 2010–2020.

Among the landscapes in the watershed, the mean of the PLAND of the forest is the maximum of approximately 45.08%, which is about 28 times that of the smallest PLAND (waters), indicating that the forest offers more advantages in the landscape. This result agrees with the results of the spatial characterization of land use described above. From 2000 to 2010, the forest area and constructed land patches showed an increasing trend. From 2010 to 2020, the PLAND of the constructed land increased by 19.53%, which was 12% more than that of 2000. Nevertheless, the constructed land patches experienced continuously increasing trends during the study period. Since 2001, Nanming River Basin experienced comprehensive environmental improvement, which includes increasing projects on cultivated land, forest, and the construction of a comprehensive landscape on both sides of the river. With a rise in urbanization, a large construction continues to expand to the periphery of the city. However, patches of cultivated land and grassland continue to decline.

**Figure 5.** Change of landscape pattern index on patch type scale from 2000 to 2020.

From the LPI, the LPI of the forest land far exceeds that of other land types, indicating that forest is the major land substrate in the watershed. From 2000 to 2020, the LPI of constructed land continues to increase.

From the COHESION, the patch cohesiveness of the forest and constructed land is higher, indicating that the natural connectivity of these two types of land is efficient, and the distributions are patchy in spatial distribution. From 2000 to 2020, the COHESION of cultivated land, grassland, and waters generally declined, whereas the COHESION of constructed land continued to increase, reaching 35% from 2000 to 2010, which was three times that of 2010–2020. With large-scale land exploitation, the distribution of patches of cultivated land, grassland, and water fragments go through aggregation to fragmentation, with a decrease in the natural connectivity of the landscapes. However, the patches of constructed land gradually turn into aggregated blocks of spatial distribution.

3.3.2. Analysis of the Landscape Pattern Index Change on Landscape Scale

As shown in Figure 6**,** the PD and CONTAG have a more pronounced geographical variability. The CONTAG increased significantly in the southwestern part of the basin, and the PD was high in most of the northeastern part of the basin. Moreover, the spatial distribution of the CONTAG in these areas showed the opposite PD characteristics. We found that the high-value areas of CONTAG are concentrated in the urban center of Guiyang City, owing to its simple landscape structure, its constructed land as the matrix land, and a high degree of agglomeration, which greatly reduces the fragmentation of the

landscape patches. Moreover, the low-value areas comprise the interspersed distribution of cultivated land, constructed land, and grassland, consisting of an intricate landscape structure with a high degree of landscape fragmentation in the watershed. The lower stream of the basin, at Wudang and Longli, has a lower level of landscape diversity, indicating that human activities in this area are infrequent, and the development is low. The SHEI and SHDI in the basin have similar spatial variations. In the southern part of Nanming District and the eastern part of Guanshan Lake District and Yunyan District upstream, the SHEI and SHDI have decreased significantly with a rise in urbanization and an increase in the project construction, which have become the main advantages of the landscape.

**Figure 6.** Spatial distribution of landscape pattern index at landscape level in the Nanming River Basin from 2000 to 2020. Note: (**A1**) PD in 2000; (**A2**) PD in 2010; (**A3**) PD in 2020; (**B1**) CONTAG in 2000; (**B2**) CONTAG in 2010; (**B3**) CONTAG in 2020; (**C1**) SHEI in 2000; (**C2**) SHEI in 2010; (**C3**) SHEI in 2020; (**D1**) SHDI in 2000; (**D2**) SHDI in 2010; (**D3**) SHDI in 2020.

#### *3.4. Landscape Ecological Safety Evaluation*

#### 3.4.1. Landscape Ecological Safety Changes of Nanming River Watershed

The ecological safety index of the Nanming River Basin was divided into five classes (refer to related studies regarding each grade [55]). As shown in Figure 7 and Table 1, the overall landscape ecological safety shows a continuous positive trend in the last 20 years. The medium ecological safety zone is the largest area. The low-security area is concentrated in the southwest part of the watershed, which is characterized by a farming economy, underdeveloped economy, extensively cultivated land, and interspersed distribution of grassland, forest, and waters, which destroys the stability of the landscape. Driven by urbanization, a large patch of arable land is used for infrastructure construction to improve the standard of living. The construction of residential housing is increasing on the large arable land, leading to a rise in the landscape ecological risk. However, the low-security areas decline by about 25% in 2020. The shrinkage rate in the lower security zone was 11.13%. Spatially, the constructed land is connected to patches. The patches also converge and shift to the middle-security zone, revealing a gradual increase in ecological security. The higher security zone is increasing yearly, which is mainly concentrated in the northern part of the watershed, showing that the forest offers advantages to the landscape. Despite the recent government's policy of encouraging people to return to cultivated land, the forest has not yet been encroached upon by other landscape types, providing policy support to maintain a higher security-level state. The trend of a high-security zone is increasing, which is distributed in the center of Guiyang City and at a lower elevation at the watershed. With the obvious landscape advantages and contiguous urban housing, this area has become a stable landscape structure and has low landscape fragmentation.

**Figure 7.** (**a**) Spatial distribution of landscape ecological security in 2000; (**b**) Spatial distribution of landscape ecological security in 2010; (**c**) Spatial distribution of landscape ecological security in 2020.

3.4.2. Spatial Autocorrelation Analysis of Landscape Ecological Security Index

As shown in Figure 8, the Moran's I values of the landscape ecological safety index of the Nanming River Basin were 0.394, 0.464, and 0.488, greater than 0 for the study periods 2000, 2010, and 2020 at a significance level of *p* < 0.05. This indicates that the landscape ecological safety index in the study zone is correlated, and the spatial convergence is gradually increasing.

**Figure 8.** Scatter map of ecological security index of landscape pattern in the study area from 2000 to 2020.

As shown in Figure 9, the spatial clustering pattern of landscape ecological safety values in the Nanming River basin is characterized by high–high clustering and low–low clustering. The percentage of high–high concentration sample areas gradually increased over the three periods, ranging from 7.66% to 12.66%. From the local autocorrelation of the study area, the cluster structure of "high–high" values of the landscape ecosystem security index continues to extend outward from 2000. However, the range of "low–low" values continues to shrink. In terms of spatial distribution, the ecological safety high-value catchment area of the watershed is concentrated in the center of Guiyang City, with little distribution in the eastern part of the downstream Wuzhong. In this area, the terrain is relatively flat, and the topographic conditions are simple, with a single land-use landscape type as the main feature. Low-value ecological security catchment areas are focused on the central Huaxi and southern Pingba in the upper part of the watershed. At the same time, we found that the internal structure of the landscape in the adjacent areas of the region is finely fragmented. Additionally, each land use landscape type is disturbed by human activities and interspersed with each other; so the ecological safety is in a low-value state, and its stability may be difficult to maintain.

**Figure 9.** (**a**) LISA Map of Landscape Ecological Security in 2000; (**b**) LISA Map of Landscape Ecological Security in 2010; (**c**) LISA Map of Landscape Ecological Security in 2020.

#### **4. Discussion**

#### *4.1. Landscape Ecological Safety Evolution Rules*

(1) Change in the Landscape Ecological Safety Index

From 2000 to 2020, the landscape ecological security index showed an increasing trend, indicating that the ecological security of the Nanming River Basin gradually increased. Driven by the market economy, crop cultivation has increased in the upper watershed, making a certain amount of forest and grassland reclaimed as cropland. Moreover, a huge number of cultivated land has been converted to forest and constructed land, which was driven by the policy of returning farmland to forest and the construction of land expansion. This policy has increased the fragmentation of forest and cropland landscapes, decreased connectivity, and decreased the ecological security index. With urbanization and rapid economic development, the non-farm population has increased, and the disturbance to the watershed landscape from human activities has risen. This development enhances the distribution of the construction of landscapes favoring human ecological and living needs. Moreover, the contiguous distribution of constructed land decreases the fragmentation of landscape patches and increases the degree of stability because of the low vulnerability in the flat topography. Thus, the ecological safety index of the constructed land has maintained its maximum value in the last 20 years. Additionally, the implementation of artificial landscaping projects in the watershed has rationalized the layout of the grassland landscape and increased the landscape ecological safety index.

#### (2) Spatial Distribution of Landscape Ecological Safety Index

Table 2 shows a comparative analysis of the relevant literature [56–68]. In karst areas, the regional characteristics above the higher ecological safety level are manifested as follows: 1 They are located at lower elevations and in urban centers with faster economic development. 2 These areas are also the most concentrated belt of forest or the constructed land and forest of the landscape. Low-security and lower-security areas are characterized by cultivated land, grassland, and water. In non-karst areas, areas above medium security level are dominated by natural ecosystems such as forest and grassland, which are concentrated in agricultural areas or natural landscape protection zones far from urban centers. However, low-security level areas are distributed on constructed land, and natural landscape structures are fragmented by human interference.

Thus, the higher safety-level areas of the watershed are distributed in the central urban areas, whereas the constructed land is concentrated and contiguous. Moreover, the low and lower ecological safety areas are characterized by a distribution of interspersed and scattered forest, grassland, and cultivated land.

These results contradict results presented by previous studies conducted in non-karst areas. Compared with related studies in karst areas, the Panlong River Basin located in Kunming [60] has a social and geomorphic environment comparable to the study area. Lin et al. found that the ecological safety index of the constructed land within the Panlong River Basin was higher than that of other landscape types. Moreover, the landscape types formed by human behavioral activities have the characteristics of being the most resistant and stable to external disturbances. Taking the Dianchi watershed as a case study, Wu et al. analyzed ecological security and found that the high-security areas were located in the urban areas because urban housing was distributed in a row, with almost no other land use landscape. Moreover, the patches are highly connected and less fragmented, making them capable of resisting external disturbances [61]. These findings are in line with the results of this study.

From the above comparison of the landscape ecological security research in non-karst and karst areas, it is recommended to give more attention to the fallibility and fragility of natural ecosystems during the process of karst ecosystem restoration and reconstruction, such as forests and grassland. In non-karst areas, we should pay more attention to the uncontrolled expansion of constructed land and the quality of the surrounding natural ecosystem. In addition, in the follow-up study, the factors influencing the spatial distribution difference of ecological security of landscape patterns in non-karst and karst areas should be discussed in depth.

**Table 2.** Relevant study on ecological security of landscape pattern.

#### *4.2. Limitations and Shortcomings*

In interpreting land use type data through RS images and analyzing land use changes and landscape patterns in the Nanming River Basin, this study evaluated the spatiotemporal variation characteristics of ecological security in the basin. However, some shortcomings are found that require improvement. The results inevitably have certain errors when interpreting images through RS technology because the results have been influenced by objective factors and human subjective factors, thereby affecting the accuracy verification. Thus, the ground-based field data surveys and historical record data must be rectified to

improve the accuracy of the interpretation results. The dynamic and landscape indicators of land use types only reflect the macro-structural changes influenced by topographic factors [68]. However, it is difficult to reveal the microstructural changes in the landscape. Thus, the microstructural changes in the landscape should be explored in future studies.

As a natural geographical unit, a watershed is the unification of multiple catchment areas within a natural environment [69]. However, watershed boundaries and administrative boundaries cannot completely overlap [70]. Thus, when exploring the influence of the natural environment and anthropogenic activities on watershed landscape patterns and ecological security, these influences cannot be fully quantified because of some constraints on the analysis of watershed change.

#### **5. Conclusions**

This study used 3S technology, the landscape pattern index method, and spatial autocorrelation theory to systematically analyze the landscape pattern evolution characteristics of the Nanming River watershed and evaluate the ecological security of the karst watershed in the Guizhou plateau. Several conclusions were obtained as follows. Forest was the leading landscape and mainland substrate in the watershed from 2000 to 2020. The cohesiveness of constructed land patches continues to increase. Moreover, the fragmentation and diversity of landscape pattern in the patchy distribution of forest and constructed land have declined. The growth rate of the Nanming River Basin Landscape Ecological Safety Index has increased by 5.80%, and the overall ecological safety has shown a continuous positive trend. The high-value ecological safety clusters are distributed in the central urban areas, where the constructed land is concentrated and contiguous. Moreover, the low-value clusters show the scattered distribution characteristics of forest, grassland, and cultivated land. Thus, the spatial clustering effect of the ecological security index is obvious, which is dominated by high–high clustering and low–low clustering types. The study reveals the landscape pattern evolution rules of the typical karst watershed in the Guizhou plateau since 2001 by systematically evaluating the spatiotemporal distribution characteristics of ecological security in the watershed. The findings provide scientific reference for maintaining the ecological balance in the watershed, optimizing land resource allocation and regulation, and improving the ecological environment of typical karst watershed geomorphic units.

**Author Contributions:** Y.L.: Methodology, Investigation, Formal Analysis, Visualization, Writing— Original Draft, Writing—Review and Editing. H.G.: Data Curation, Resources, Formal Analysis. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was jointly supported by the Youth Talent Growth Project of Guizhou Provincial Department of Education (Qian Jiao He KY [2022] No. 202), the Water Conservancy Science and Technology Funding Projects in Guizhou Province (KT202114), the Water Conservancy Science and Technology Funding Projects in Guizhou Province (KT202223), National Natural Science Foundation of China (42261044).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declared that they have no conflict of interest to this work. We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

#### **References**

**Yu Zhang 1, Chaoyong Shen 1,2,3,\*, Shaoqi Zhou 1,\*, Ruidong Yang 1, Xuling Luo 3 and Guanglai Zhu 1**

**Abstract:** Remote sensing image with high spatial and temporal resolution is very important for rational planning and scientific management of land resources. However, due to the influence of satellite resolution, revisit period, and cloud pollution, it is difficult to obtain high spatial and temporal resolution images. In order to effectively solve the "space–time contradiction" problem in remote sensing application, based on GF-2PMS (GF-2) and PlanetSope (PS) data, this paper compares and analyzes the applicability of FSDAF (flexible spatiotemporal data fusion), STDFA (the spatial temporal data fusion approach), and Fit\_FC (regression model fitting, spatial filtering, and residual compensation) in different terrain conditions in karst area. The results show the following. (1) For the boundary area of water and land, the FSDAF model has the best fusion effect in land boundary recognition, and provides rich ground object information. The Fit\_FC model is less effective, and the image is blurry. (2) For areas such as mountains, with large changes in vegetation coverage, the spatial resolution of the images fused by the three models is significantly improved. Among them, the STDFA model has the clearest and richest spatial structure information. The fused image of the Fit\_FC model has the highest similarity with the verification image, which can better restore the coverage changes of crops and other vegetation, but the actual spatial resolution of the fused image is relatively poor, the image quality is fuzzy, and the land boundary area cannot be clearly identified. (3) For areas with dense buildings, such as cities, the fusion image of the FSDAF and STDFA models is clearer and the Fit\_FC model can better reflect the changes in land use. In summary, compared with the Fit\_FC model, the FSDAF model and the STDFA model have higher image prediction accuracy, especially in the recognition of building contours and other surface features, but they are not suitable for the dynamic monitoring of vegetation such as crops. At the same time, the image resolution of the Fit\_FC model after fusion is slightly lower than that of the other two models. In particular, in the water–land boundary area, the fusion accuracy is poor, but the model of Fit\_FC has unique advantages in vegetation dynamic monitoring. In this paper, three spatiotemporal fusion models are used to fuse GF-2 and PS images, which improves the recognition accuracy of surface objects and provides a new idea for fine classification of land use in karst areas.

**Keywords:** spatiotemporal fusion; land use; high resolution; FSDAF; STDFA; Fit\_FC


**4. Discussion**

4. Discussion

and no doors.

The water quality assessment in Guinea-Bissau revealed that the water sources used for drinking purposes countrywide were acidic to very acidic, and heavily contaminated with faecal material. Higher levels of contamination were found during the wet season, associated with wells and the use of a bucket to withdraw water. This trend has previously been identified in regional studies performed in the country [12,25].In Guinea-Bissau, the majority of the population retrieve water from shallow (<15 m), hand-dug wells, without any wall isolation or well cover protection. Typically, each well was fitted with a bucket and rope to withdraw water, although some had a manual pump associated. This proportion was visible during the survey, with about one borehole analysed for every six wells. Only 20.5% of the population has access to proper sanitation; thus, communal latrines are the standard, although in rural areas open defecation is still common [9]. Nevertheless, The water quality assessment in Guinea-Bissau revealed that the water sources used for drinking purposes countrywide were acidic to very acidic, and heavily contaminated with faecal material. Higher levels of contamination were found during the wet season, associated with wells and the use of a bucket to withdraw water. This trend has previously been identified in regional studies performed in the country [12,25].In Guinea-Bissau, the majority of the population retrieve water from shallow (<15 m), hand-dug wells, without any wall isolation or well cover protection. Typically, each well was fitted with a bucket and rope to withdraw water, although some had a manual pump associated. This proportion was visible during the survey, with about one borehole analysed for every six wells. Only 20.5% of the population has access to proper sanitation; thus, communal latrines are the standard, although in rural areas open defecation is still common [9]. Nevertheless, most are single pit latrines, with a basic thatched or galvanized corrugated sheet walls and no doors.

most are single pit latrines, with a basic thatched or galvanized corrugated sheet walls The high faecal contamination observed throughout the year is essentially a consequence of the proximity between wells and latrines (<30 m), the presence of freely wandering domestic animals (including cattle), and the contact of the bucket and rope with The high faecal contamination observed throughout the year is essentially a consequence of the proximity between wells and latrines (<30 m), the presence of freely wandering domestic animals (including cattle), and the contact of the bucket and rope with contaminated soil, as reported by several previous studies in Guinea-Bissau [12–14,26] and perceived by the authors in the field.

contaminated soil, as reported by several previous studies in Guinea-Bissau [12–14,26] and perceived by the authors in the field. The influence of pit latrines on groundwater quality was previously described, being recognized as a major source of water contamination depending on the surrounding environment, particularly hydrological and soil conditions [27–29]. Rainfall promotes the mobilization of soil particles through infiltration and percolation that eventually reach the The influence of pit latrines on groundwater quality was previously described, being recognized as a major source of water contamination depending on the surrounding environment, particularly hydrological and soil conditions [27–29]. Rainfall promotes the mobilization of soil particles through infiltration and percolation that eventually reach the subsurface groundwater, conveying associated bacteria and viruses. Sediments are well known reservoirs for microorganisms, typically revealing higher bacterial levels than the water column [30]. Indeed, in accordance with other studies [13,26], high levels of

subsurface groundwater, conveying associated bacteria and viruses. Sediments are well

tamination could be observed in the wet season, associated with a simultaneous increase in turbidity. Turbidity in water is caused by suspended particles or colloidal matter, and

contamination could be observed in the wet season, associated with a simultaneous increase in turbidity. Turbidity in water is caused by suspended particles or colloidal matter, and may be caused by inorganic or organic matter, or a combination of the two [31]. Due to the high superficial area and metabolic substrate concentration, high turbidity can provide an adequate environment for microorganism growth and persistence. Indeed, drinking water turbidity has been associated with the incidence of gastrointestinal diseases [32]. In Guinea-Bissau, the reported diarrhoea episodes systematically peak at the onset of the wet season [33,34], and the main cholera outbreaks have been reported during the wet season [11]. Additionally, the persistent high water temperature (average 29.1 ◦C) observed in wells year-round can also contribute to foster microbial growth [35].

Furthermore, the majority of wells were fitted with buckets and ropes that are often placed on the ground due to the lack of a basic overhead frame to hang them when not in use. This may allow contact with animals and human excreta; moreover, the tools may not exclusively be used to retrieve water. The aggravated situation was confirmed by the results obtained from the models, indicating that the method used to collect water was one of the most influential predictors. The use of a bucket considerably increased the contamination levels. On the other hand, boreholes (>20 m) were drilled mechanically and fitted with a pump (solar, electric), and were thus less prone to contamination.

The relationship between faecal indicators and the nitrogen species strengthen the hypothesis stated above; that microbial contamination enters groundwater due to infiltration and percolation from the surface. The presence of high concentrations of ammonium, nitrate, or nitrite in drinking water are recognized as indicators of possible bacterial, sewage, and animal waste pollution or agricultural runoff [36]. Moreover, there is an increased risk of methemoglobinemia development in bottle-fed infants associated with high concentrations of N species in drinking water, which can further be complicated by the concurrent presence of microbial contamination [36,37]. Additionally, nitrate appears to competitively inhibit iodine uptake, and the long-term exposure by drinking water intake can contribute to the iodine deficiency problem felt in countries such as Guinea-Bissau [36,38].

The faecal contamination was revealed to be related with latitude, with an increment towards the northern part of the country, that can be potentially explained by additional faecal contamination associated with the livestock presence. Although recent data are not available, according to the national livestock census in Guinea-Bissau conducted in 2009, it was estimated that the total number of cattle was approximately 1,325,412, mainly concentrated in the northern areas (Gabu, Bafata, and Oio regions) [39], owned by Fulani, Mandinga, and Balanta ethnic groups. The practice of extensive cattle ranching still dominates in Guinea-Bissau, with a marked transhumance period during the dry season for pasturage and water [40]. Cattle lairage is an unused practice in Guinea-Bissau and livestock roam free in the fields, representing a potential pollution source for unprotected shallow wells. It could be argued that the lairage of cattle could somehow contribute to a diffuse contamination decrease; however, the solution is unworkable due to the lack of water and fodder, technical resources, and infrastructure support.

Overall, similarly to other studies [12–14], the chemical contamination was less relevant, with metal concentrations below the acceptable limits for the majority of the studied water sources. Nonetheless, it is important to note that high metal levels were observed in several wells, and the consumption of elevated levels of metals through drinking water has been associated with the development of health problems, including cancer [31]. Again, the positive correlation found between metal concentration and turbidity indicated the potential role of soil particles as a natural contamination source. During the wet season, the soil particles and associated metal-rich leachates can easily be mobilized by percolation and infiltration, reaching the subsurface groundwater that feeds the shallow wells. In the dry season, the water–soil contact is promoted by the low water level and higher residence time of the water, with increased contact with the earth walls and bottom sediments, fostering high water turbidity.

The majority of the water sources were outside the suitable pH range for drinking water according to EU standards, in the acidic to very acidic interval, a consequence of red, sulphur-rich, sandy-clay soil characteristics [41]. The consumption of acidic water can have a direct impact on population health, particularly in dental erosion [42,43] and through the potential mobilization of heavy metals [44]. Currently, very limited working water networks are available in the country; therefore, the risk of metal contamination through pipes does not seem to be problematic, although such low pH values have to be taken into account in the construction of future infrastructure or rehabilitation initiatives, in order to choose the most suitable materials. Additionally, the corrosion of the materials used in constructing well and distribution systems can enable the feed and growth of microorganisms from adjacent areas in the water used for drinking. Bacteria can adapt to environmental conditions such as low pH, potentially reducing the stomach acidic barrier efficiency, and consequently, the required infectious dose to cause disease [45].

The access to safe drinking water, in addition to being a basic human right, is associated with population health, and consequently, with poverty. Waterborne diseases linked to inadequate WASH are a key public health concern [46–48], particularly in middle- and low-income countries, which needs to be addressed for country development. Furthermore, the expected population growth and the climate change scenario will pose an additional threat to WASH infrastructure and services [49].

This study highlighted the urgent need to improve the access to safe drinking water in sub-Saharan countries, such as Guinea-Bissau. For a long-term solution, a robust, countrywide intervention on WASH infrastructure is pivotal. New construction or rehabilitation of the limited water and sanitation networks should be performed, taking into account the local and regional conditions (such as the acidic groundwater), and forearm periodic maintenance and water quality monitoring, which are presently inexistent. To ensure water quality safety, government administration and non-governmental organizations must favour the construction of deep boreholes, even if it means cooperation and co-ordination between agencies, as well as constructing less infrastructure, due to the higher associated costs. Water quality should be regularly monitored, and if needed, promptly treated using the disinfection treatments techniques currently available and applied in countries with limited resources [50,51]. Emphasis should also be placed on the collection and treatment of effluent from latrines, including the construction of sealed tanks—septic tanks—and the disposal of waste into small collective treatment plants with biological beds. Furthermore, scientific and technical advice, prior and during construction, is essential for correct guidance on the establishment of local infrastructure and maintenance.

The traditional or settled way of living can be a hindrance to development; therefore, the implementation of behaviour change programs, with structured formative and educational interventions to raise awareness at the different societal levels (individual, household, community, and institutional) will be decisive to prevent disease transmission. The integration of local stakeholders and the community, throughout the implementation programs, will help to ensure the sustainable use and management of water.

On other hand, considering the urgency overt in the results of this study, the authors propose the short-term implementation of simple, sustainable measures, which could drastically improve the access to safe drinking water, mitigating the associated health risk: