Figure 2 shows the temporal variations in Chl-a, TSI, and SD for 2019, 2020, 2021, and 2022. The statistical analysis of chlorophyll-a (Fig. 2.a) in DMo Lake revealed that in 2019, the average concentration was 41.73 µg/l, with a marginal reduction of 0.18 µg/l recorded in 2020 (averaging 41.55 µg/l). Furthermore, a significant decrease of 21.01 µg/l was observed in 2021, followed by a slight increase of 2.82 µg/l in 2022 (a total of 23.83 µg/l). Similarly, the chlorophyll content of SCh Lake decreased to 42.82 µg/l in 2019, 32.17 µg/l in 2020, 23.08 µg/l in 2021, and 16.17 µg/l in 2022. For DORh Lake, chlorophyll decreased by 7.44 µg/l between 2019 and 2020 (53.77 µg/l in 2019 compared with 46.33 µg/l in 2020). Moreover, an increase to 61.96 µg/l was observed in 2021, followed by a decrease to 25.3 µg/l in 2022.
For the TSI (Fig. 2.b), the values obtained indicate the positive effect of the lockdown on water quality. For DMo Lake, the average was 5.95 in 2019. In 2020, this average decreased to 5.86. A notable decline in TSI values is recorded in 2021, with an average of 5.36 (a decrease of 0.5). An increase of 0.51 (resulting in a TSI of 0.87) is expected to occur in 2022. For SCh Lake, the TSI increased by 0.41 between 2019 and 2020 (5.32 in 2019 against 5.73 in 2020), followed by a significant decrease of 1.61 in 2021. An increase to 4.81 is expected to occur in 2022. The same changes also affected DORh Lake, with an increase of 0.02 between 2019 and 2020, followed by a decrease to 5.32 in 2021 before the values increase again to reach 5.85 in 2022.
Similarly, the Secchi depth (Fig. 2.c) confirmed the positive effect of the lockdown on the changes in the physicochemical characteristics of the water in the three studied wetlands. DMo Lake exhibited a significant improvement in water clarity, with an average depth of 1.31 m in 2019 and 1.51 m in 2020, reaching 2.75 m in 2021. This clarity is substantially reduced to a depth of 1.33 m in 2022. The same trend was also observed for SCh Lake, with improvements of 1.40, 1.43, and 2.07 meters in 2019, 2020, and 2021, respectively. This is followed by a decrease in depth to reach 1.31 m in 2022. For DORh Lake, the water quality significantly improved between 2019, 2020, and 2021, with depths of 1.16, 1.75, and 2.61 meters, respectively. However, a decrease in water quality is expected to occur in 2022, with a maximum depth of 1.4 meters.
Chl-a can be used as a common parameter for the water quality index (Muduli et al. 2021). This study provides insights into the trophic state and overall health of aquatic ecosystems (Table 3 and Fig. 3). In 2019, 55.70% of DORh Lake was characterized by chlorophyll concentrations exceeding 61.52 µg/l, while 21.13% of the lakes had chlorophyll concentrations ranging between 50.87 µg/l and 61.51 µg/l. Additionally, low concentrations (< 22.10 µg/l) occupy barely 2.6% of the overall surface area. In 2020, there was a clear trend toward the dominance of medium concentrations (32.77–50.86 µg/l), covering 85.94% (262.06 ha) of the total area. Following the imposed lockdown, the Chl-a concentration gradually decreased in 2021, with 8.96% (23.66 ha) of the total area falling below 22.10 µg/l. The consequences of this lockdown are expected to reach optimal values in 2022, with 12.91% (39.01 ha) for the class < 22.10 µg/l, 86% for the class 22.11–32.76 µg/l, and 0% for concentrations exceeding 50.87 µg/l. Based on the Chl-a classification table and its ecological characteristics (Carlson and Simpson 1996), it is evident that in 2019, DORh Lake was dominated by a hypereutrophic ecological characteristic (76%), with water quality deemed uninhabitable. In 2020, water quality improved, with 85% of the surface exhibiting eutrophic ecological characteristics dominated by blue‒green algae, algal blooms, and macrophyte issues. However, despite the lockdown implemented in 2021, a considerable increase in the area dominated by hypereutrophic (59%) and eutrophic (15%) ecological characteristics was noted. In 2022, water quality significantly improved, with 86% exhibiting eutrophic characteristics (dominated by blue‒green algae, algal blooms, and macrophyte issues) and 12% displaying hypolimnetic anoxia, with possible macrophyte problems.
For DMo Lake, chlorophyll-a concentrations were notably found in the medium (37.07–41.85 µg/l) and high (41.86–47.73 µg/l) classes, covering 33.14 ha (23.87%) and 96.18 ha (69.29%), respectively. Low concentrations ranging from 10.49 to 27.04 µg/l barely accounted for 1%. Water quality is expected to improve significantly in 2020, with values of 11%, 18%, and 45% for the 27.05–37.06 µg/l, 37.07–41.85 µg/l, and 41.86–47.73 µg/l classes, respectively. A notable improvement is observed in 2021 and 2022, with dominance at low concentrations. Specifically, 65% of the compounds were in the 10.49–27.04 µg/l class, 31% were in the 27.05–37.06 µg/l class in 2021, and 55% and 44% were in the same classes in 2022. The dominant ecological characteristic in 2019 was eutrophic (with the dominance of blue‒green algae, algal blooms, and macrophyte issues), indicating poor water quality. However, in 2020, an increase in hypereutrophic characteristics was easily identified. The COVID-19 pandemic contributed to improving water quality, with eutrophic characteristics and poor water quality.
The same trend was observed for SCh Lake, with a dominance of medium (36.73–44.49 µg/l) and high (44.49–53.82 µg/l) concentrations in 2019, accounting for 21.28% and 60.86%, respectively. In 2020, there was an improvement in water quality, with an increase in concentrations below 25.32 µg/l reaching 6%, a considerable increase in the class ranging from 25.33 µg/l to 36.72 µg/l with 52%, and finally an increase in the class ranging from 36.73 µg/l to 44.49 µg/l, covering a total area of 33%. Moreover, with the lockdown, the chlorophyll concentration decreased significantly in 2021 and 2022. Concentrations below 36.72 µg/l accounted for 93% of the total in 2021, reaching 100% in 2022. In general, SCh Lake is no exception. The dominance of the hypereutrophic ecological characteristic was observed in 2019, followed by 2020, 2021, and 2022 by the eutrophic characteristic with the dominance of blue‒green algae, algal blooms, and macrophyte issues in 2020, and hypolimnetic anoxia with possible macrophyte problems in 2021 and 2022.
Table 3. Variations in Chl-a for 2019, 2020, 2021 and 2022
class
|
2019
|
2020
|
2021
|
2022
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Lake of Dayet Oum Rhalez
|
10.39 – 22.10
|
8.18
|
2.68
|
4.18
|
1.37
|
23.66
|
8.96
|
39.01
|
12.91
|
22.11 – 32.76
|
53.57
|
17.53
|
2.60
|
0.85
|
6.49
|
2.46
|
262.78
|
86.93
|
32.77 – 50.86
|
9.09
|
2.97
|
262.06
|
85.94
|
35.14
|
13.30
|
0.49
|
0.16
|
50.87 – 61.51
|
64.57
|
21.13
|
30.89
|
10.13
|
41.71
|
15.79
|
0.00
|
0.00
|
61.52 – 78.29
|
170.24
|
55.70
|
5.19
|
1.70
|
157.14
|
59.49
|
0.00
|
0.00
|
Lake of Dhayat Morasli
|
10.49 – 27.04
|
1.50
|
1.08
|
5.41
|
3.90
|
88.55
|
65.21
|
76.07
|
55.09
|
27.05 – 37.06
|
5.61
|
4.04
|
16.10
|
11.61
|
43.29
|
31.88
|
61.87
|
44.81
|
37.07 – 41.85
|
33.14
|
23.87
|
25.78
|
18.58
|
1.84
|
1.36
|
0.14
|
0.10
|
41.86 – 47.73
|
96.18
|
69.29
|
63.31
|
45.64
|
1.00
|
0.74
|
0.00
|
0.00
|
47.74 – 66.03
|
2.38
|
1.71
|
28.12
|
20.27
|
1.11
|
0.82
|
0.00
|
0.00
|
Lake of Sidi Chahmi
|
9.781 - 25.32
|
0.47
|
3.03
|
0.94
|
6.05
|
5.95
|
40.48
|
15.15
|
96.68
|
25.33 – 36.72
|
1.40
|
9.03
|
8.08
|
52.03
|
7.77
|
52.86
|
0.52
|
3.32
|
36.73 – 44.49
|
3.30
|
21.28
|
5.24
|
33.74
|
0.63
|
4.29
|
0.00
|
0.00
|
44.49 - 53.82
|
9.44
|
60.86
|
0.95
|
6.12
|
0.35
|
2.38
|
0.00
|
0.00
|
53.82 - 75.84
|
0.90
|
5.80
|
0.32
|
2.06
|
0.00
|
0.00
|
0.00
|
0.00
|
The trophic state index (Table 4 and Fig. 4) provides a quantitative measure of water quality by assessing the nutrient levels present. In 2019, 99% of DORh Lake was characterized by a high biological productivity level exceeding 50%, while less than 0.08% exhibited low nutrient levels (> 50%). In 2020, there was a slight improvement in water quality, with an increase in the area of biological productivity below 50% at 10% (28 ha). Unfortunately, this is accompanied by an increase in the class (> 60–100%) at the expense of the class (50–60%), with 85.45% and 4.40%, respectively. Improvement can be observed in 2021, with 11.55% for the class (< 30–40%) and 8.13% for the class (40–50%). The percentage of the class with biological activity exceeding 60% decreased to 64%. Conversely, water became uninhabitable again immediately after the lockdown, with 91% (260 ha) exhibiting biological activity levels exceeding 60% and 1.71% (4.89 ha) exhibiting levels below 40%. Overall, DORh Lake is characterized by high biological activity with a hypereutrophic water body. This indicates that the water quality is poor, even after the forced lockdown is applied.
For DMo Lake, nutrient levels in 2019 exceeded 96% for the class above 60%, compared to 0.06% for the class below 40%. This reflects the poor state of water quality. A slight improvement was observed in 2020, with 1.99% for the 40–50% class and 5.05% for the 50–60% class. Following the lockdown, a significant decrease (38%) in biological activity was noted in the class above 60%, accompanied by an increase in biological activity in the class (50–60%) of 59.94% (75.45 ha). Indeed, water quality will degrade again in 2022. The biological productivity increased significantly, particularly for the class (> 60%), with a total area of 116.97 ha (92.93%). The results revealed an improvement in water quality in 2021, transitioning from a hypereutrophic water body in 2019 and 2020 to a eutrophic water body in 2021. In general, water quality fluctuates between poor and uninhabitable areas.
The results obtained for SCh Lake are intriguing. The nutrient levels in 2019 were divided as follows: 9.44% (ha) for the < 40% class, 14.08% (1.79 ha) for the 40–50% class, and 11.88% (1.51 ha) for the 50–60% class. The > 60% class represents 64% of the total class. This good water quality decreased in 2020 to yield the following results: 2.44% (0.31 ha) for the < 40% class, 3.31% (0.42 ha) for the 40–50% class, and 80.91% (10.26 ha) for the > 60% class. In 2021, the lockdown imposed due to the COVID-19 pandemic significantly improved water quality, with 28.45% for classes below 40%, 35.93% for classes 40–50%, 30.73% for classes 50–60%, and 4.89% for classes above 60%. After the lockdown, an increase in biological productivity levels can be easily observed, particularly in the classes 50–60% and > 60% at 64.20% (8.14 ha) and 10.88% (1.38 ha), respectively. According to the trophic scale, the water bodies transitioned from eutrophic in 2019 to hypereutrophic in 2021. Moreover, in 2021, the biological activity was considered moderate, indicating a mesotrophic water body. In terms of water surface pollution, this suggests a passable quality. However, this situation will rapidly degrade in 2022, when the water quality will become poor and the eutrophic water body will dominate.
Table 4. Variations in TSI for the years 2019, 2020, 2021 and 2022
class
|
2019
|
2020
|
2021
|
2022
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Lake of Dayet Oum Rhalez
|
<30 – 40%
|
0.13
|
0.05
|
16.87
|
5.92
|
32.93
|
11.55
|
4.89
|
1.71
|
40 – 50
|
0.094
|
0.03
|
12.08
|
4.24
|
23.19
|
8.13
|
6.69
|
2.35
|
50 – 60
|
92.81
|
32.55
|
12.54
|
4.40
|
46.40
|
16.27
|
13.40
|
4.70
|
>60 – 100
|
192.12
|
67.37
|
243.70
|
85.45
|
182.62
|
64.05
|
260.19
|
91.24
|
Lake of Dhayat Morasli
|
<30 – 40%
|
0.07
|
0.06
|
1.77
|
1.41
|
0.47
|
0.37
|
0.47
|
0.37
|
40 – 50
|
0.35
|
0.28
|
2.50
|
1.99
|
1.47
|
1.17
|
4.70
|
3.73
|
50 – 60
|
3.83
|
3.04
|
6.36
|
5.05
|
75.45
|
59.94
|
3.73
|
2.96
|
>60 – 100
|
121.58
|
96.62
|
115.22
|
91.55
|
48.48
|
38.52
|
116.97
|
92.93
|
Lake of Sidi Chahmi
|
<30 – 40%
|
1.20
|
9.44
|
0.31
|
2.44
|
3.61
|
28.45
|
0.67
|
5.28
|
40 – 50
|
1.79
|
14.08
|
0.42
|
3.31
|
4.56
|
35.93
|
2.49
|
19.64
|
50 – 60
|
1.51
|
11.88
|
1.69
|
13.33
|
3.90
|
30.73
|
8.14
|
64.20
|
>60 – 100
|
8.21
|
64.59
|
10.26
|
80.91
|
0.62
|
4.89
|
1.38
|
10.88
|
The Secchi depth (Table 5 and Fig. 5) is used to measure the depth at which the disk is no longer visible from the water surface. This measurement serves as an indicator of water transparency and quality (Harrison 2016). In 2019, 99.81% of the surface area of DORh Lake was characterized by a depth not exceeding 2 m, while depths exceeding 8 m barely accounted for 0.03%. This indicates a disastrous state of water quality (poor quality according to the trophic degree scale) with a dominance of the eutrophic mass. A marginal improvement in transparency was recorded in 2020, with 88.76% of the depths being visible below 2 m and 1% exceeding 8 m. Depths ranging from 2 m to 8 m constitute 10% of the lake. Moreover, following the enforced lockdown, a significant improvement in water clarity was observed in 2021. A considerable increase in depths exceeding 8 m at 1.4% was accompanied by an increase in depths of 2–4 m and 4–8 m at 32.80% and 12.75%, respectively. A total of 53.05% of the depths below 2 m decreased. The situation deteriorated in 2022, with 98% for depths below 2 m and 0.49% for depths exceeding 8 m. Generally, the dominant trophic class in DORh Lake is eutrophic, indicating high biological activity and poor water quality. However, with confinement, considerable areas transform into mesotrophic (92.75 ha) and oligotrophic (36.06 ha) areas, with water quality ranging between fair and good.
The same trend was observed for DMo Lake, with a predominance of depths below 2 m of 99.48% in 2019 and 94.91% in 2020. This is followed by a slight improvement in depths of 2–4 m, 4–8 m, and 8–10 m at 4.76%, 5.58%, and 0.90%, respectively. In 2021, the positive effects of the lockdown were easily identifiable, with a significant improvement in transparency in the classes ranging from 2 m to 4 m (75.89%) and between 4 m and 8 m (6.85%). However, the water quality rapidly decreased in 2022, with 99.48% of the depths below 2 m and barely 0.05% of the depths exceeding 8 m. In summary, except for 2021 (with the water body classified as mesotrophic of moderate quality), the water quality of DMo Lake is poor, and its biological activity is classified as high with a eutrophic water body.
Interesting results were obtained for SCh Lake between 2019 and 2020. In addition to classes 2–4 m, depths of 0–2 m, 4–8 m, and 8–10 m exhibited decreases in surface area, with 95.93% compared to 95.45%, 2.49% compared to 2.33%, and 0.45% compared to 0.36%, respectively. After the lockdown, water quality improved in 2021, and clarity exceeding 4 m occupied more than 10% of the water surface. However, 75% of the surface remains of inferior quality (visible at less than 2 m). In 2022, the situation is no exception, and water quality will deteriorate. A total of 97.15% of the surface is characterized by a depth not exceeding 2 m. According to these statistics, the water quality in this area is poor (eutrophic water body).
Table 5. Variations in SD for the years 2019, 2020, 2021 and 2022
class
|
2019
|
2020
|
2021
|
2022
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Area (ha)
|
Area (%)
|
Lake of Dayet Oum Rhalez
|
0 – 2
|
284.64
|
99.81
|
251.92
|
88.76
|
150.02
|
53.05
|
278.22
|
98.00
|
2 - 4
|
0.14
|
0.05
|
13.52
|
4.76
|
92.75
|
32.80
|
1.36
|
0.48
|
4 – 8
|
0.33
|
0.12
|
15.83
|
5.58
|
36.06
|
12.75
|
2.93
|
1.03
|
8 - 10
|
0.078
|
0.03
|
2.56
|
0.90
|
3.97
|
1.40
|
1.39
|
0.49
|
Lake of Dhayat Morasli
|
0 – 2
|
125.13
|
99.48
|
119.04
|
94.91
|
21.54
|
17.13
|
125.19
|
99.48
|
2 - 4
|
0.30
|
0.24
|
3.53
|
2.81
|
95.42
|
75.89
|
0.38
|
0.30
|
4 – 8
|
0.35
|
0.28
|
2.39
|
1.91
|
8.61
|
6.85
|
0.21
|
0.17
|
8 - 10
|
0.008
|
0.01
|
0.46
|
0.37
|
0.17
|
0.14
|
0.06
|
0.05
|
Lake of Sidi Chahmi
|
0 – 2
|
11.94
|
95.93
|
11.86
|
95.45
|
9.43
|
75.93
|
11.95
|
97.15
|
2 - 4
|
0.14
|
1.12
|
0.23
|
1.85
|
1.66
|
13.37
|
0.09
|
0.73
|
4 – 8
|
0.31
|
2.49
|
0.29
|
2.33
|
1.21
|
9.74
|
0.18
|
1.46
|
8 - 10
|
0.056
|
0.45
|
0.045
|
0.36
|
0.12
|
0.97
|
0.08
|
0.65
|
The concentration of chlorophyll an in a lake is influenced by various environmental, biological, and anthropogenic factors (Huang et al. 2022); (Benkesmia et al. 2023); (Zhang et al. 2024). These factors may vary depending on specific lake characteristics, such as proximity to urban and industrial development and the presence or absence of direct discharge into the lake. Additionally, meteorological conditions, especially precipitation, can affect chlorophyll-a concentrations through variations in water levels in the lake (Das Sarkar et al. 2020); (Han et al. 2023). They can also influence nutrient runoff from the watershed into the lake. Heavy rainfall events can lead to sudden nutrient inputs. In this study, we aimed to explore the underlying factors behind spatiotemporal variations in environmental parameters such as the chlorophyll-a concentration (Chl-a), trophic state index (TSI), and Secchi depth (SD) in DORh, DMo, and SCh lakes. To do so, we use a correlation coefficient to help identify the main causes of these variations. Our hypothesis is as follows: if the obtained correlation coefficient is high, precipitation is the primary influencing factor. Conversely, if the correlation is low, this could indicate that the confinement imposed in response to the COVID-19 pandemic is the main cause of the observed variations in the three parameters.
According to the results shown in Fig. 6, the effect of precipitation is weak in DMo Lake, with correlations of 16.7%, 26.22%, and 34.29% for Chl-a, TSI, and SD, respectively. Furthermore, for water bodies relatively distant from urban areas (especially DORh Lake), the effect of precipitation is significant at 81.55%, 60.19%, and 11.87%, respectively. Moreover, for SCh Lake, the effect of precipitation was relatively moderate, with 63.74%, 23.5%, and 45.02% for Chl-a, TSI, and SD, respectively. This suggests that the positive effect of confinement is recorded in DMo and to a lesser extent in SCh. This leads us to conclude that the observed pollution in DMo primarily results from untreated industrial discharge from the Es-Sénia industrial zone, specifically from factories lacking water treatment facilities, which significantly contributes to the degradation of water quality. Similarly, industrial discharge from units near SCh Lake constitutes the major source of pollution. The geographical proximity of these industrial units amplifies their impact on the ecological balance of the lake. Moreover, the implementation of confinement measures was a determining factor for the sharp decrease in chlorophyll-a concentrations recorded in 2021. In response to these measures, several industrial activities were either suspended or forced to drastically reduce their production. Consequently, industrial discharge into the DMo and SCh Lakes significantly decreased, explaining the abrupt decrease in chlorophyll-a concentrations during this period.
Furthermore, DMo has been supplied with industrial discharge (estimated flow of 6000 m3/day) and is currently receiving water that has come into contact with landfills, inert waste, and drainage water from the surrounding road network (Fig. 7). In this lake, eutrophication and the presence of illegal dumps are visible signs of water pollution (Ben Bayer et al. 2019). In 2009, a study conducted by the Ministry of Territorial Planning, Environment, and Tourism at three lake sites (Table 6) revealed that the water is excessively polluted with organic matter due to its COD and BOD5 values. The pH and suspended matter content also indicate water pollution. The results obtained show that even though there are no longer untreated discharges from the Es-Sénia industrial zone today, the water is still excessively polluted due to the measured concentrations of cadmium, copper, and chromium. These findings are also supported by two recent studies (Mahi et al. 2021); (Ben Bayer et al. 2019). According to (Mahi et al. 2021), physicochemical and bacteriological analyses exceed international standards, indicating a trend of lake pollution, particularly with values of 9.4 for pH, 198 mg/l for suspended matter, and 123.93 mg/l for COD.
Additionally, the significant increase in concentrations in DORh Lake in 2021 underscores a direct correlation with behavioral changes related to the confinement measures implemented. The small agglomeration of Khedaimia, located within 500 meters of the lake, played a crucial role in this dynamic. Due to the restrictions imposed by confinement, residents were compelled to stay at home for considerable periods. This situation led to a substantial change in lifestyle, characterized by an extended time spent at home. Consequently, domestic water consumption has notably increased, affecting various aspects of daily life. Particularly affected by these changes, the quantities of household and toilet water significantly increased. Furthermore, it is essential to note that the wetland of DORh is facing the discharge of untreated industrial water but at lower rates than DMo. This is supported by a study conducted by (Aibeche et al. 2020), in which the results of physicochemical water analyses exceeded the recommended levels in Algeria, with values of 376.27 mg/l for COD, 29.70 mg/l for BOD5, and 7.8 for pH.
In conclusion, despite the interesting results obtained and the potential of remote sensing techniques, this study has limitations that must be considered. Every remote sensing study requires ground-based measurements for validation. Unfortunately, in our case, obtaining such in situ measurements is challenging and costly, potentially introducing uncertainties. Additionally, comparing our work with other studies conducted in the same area and within a closer temporal framework can validate our findings. Moreover, it is noteworthy that the fundamental question of this study revolves around the impact of confinement on water quality, which is addressed with satisfactory results.
Table 6. Grid of the classification of surface water quality in Algeria and the results of the analyses (MATET 2010)
Parameters
|
Unit
|
Good
|
Moderate
|
polluted
|
Extremely polluted
|
Analysis results
|
Site 1
|
Site 2
|
Site 3
|
Physical quality
|
pH
|
/
|
6.5 – 8.5
|
6.5 – 8.5
|
8.5 – 9.0
|
< 6.5 et > 9.0
|
9.43
|
8.93
|
9.13
|
Suspended matter
|
mg/l
|
0-30
|
30-75
|
75-100
|
>100
|
190
|
358
|
258
|
Organic quality
|
DBO5
|
mg/l
|
5
|
5-10
|
10-15
|
>15
|
178.9
|
202.8
|
229.8
|
DCO
|
mg/l
|
20
|
20-40
|
40-50
|
>50
|
892
|
843
|
882
|
Oils and greases
|
mg/l
|
/
|
/
|
/
|
/
|
25.18
|
14.08
|
8.11
|
Heavy metals quality
|
Arsenic (As)
|
mg/l
|
/
|
/
|
> 0,01
|
/
|
0.361
|
0.108
|
0.164
|
Chrome (Cr+2)
|
mg/l
|
0
|
0-0.05
|
0.05-0.5
|
>0.5
|
0.77
|
2.08
|
0.50
|
Copper (Cu+2)
|
mg/l
|
0-0.02
|
0.02-0.05
|
0.05-1
|
>1
|
2.84
|
2.01
|
1.97
|
Cadmium (Cd)
|
mg/l
|
0
|
0
|
0-0.01
|
>0.01
|
0.168
|
0.987
|
0.123
|
Lead (Pb)
|
mg/l
|
/
|
/
|
>0.01
|
/
|
0.97
|
0.87
|
1.16
|