Monitoring of surface water quality in autumn 2019
In autumn, the general classification for this season was in class I (Table 3), which precedes the dry period, and is characterized by the beginning of a decrease in the volume of precipitation, also presenting the highest vegetative index and better water quality among all seasons. (Fig. 3). These results corroborate what was observed in other studies that found an improvement in water quality related to the presence of vegetation cover (Wang et al., 2014; Ding et al., 2015; Zhang et al., 2018).
Table 3 - Analytical results of the physical and chemical parameters of surface water and their classification according to Resolution 357/2005 CONAMA at UW in autumn 2019.
Parameters analyzed
|
Unit
of measure
|
Monitoring Points
|
Classification
by parameter
|
4
|
5
|
6
|
7
|
8
|
Physical Parameters Parâmetros físicos
|
Temperature
|
°C
|
23
|
23
|
23
|
23
|
23
|
|
Color
|
Pt/Co
|
41
|
78
|
266
|
52
|
79
|
II
|
Turbidity
|
NTU
|
1.49
|
5.99
|
30.5
|
4.48
|
8.9
|
S
|
TDS
|
mg/L
|
6.16
|
21.8
|
6.84
|
8.06
|
9.1
|
I
|
TSS
|
mg/L
|
3
|
8
|
101
|
1
|
7
|
|
Chemical Parameters
|
pH
|
|
7.05
|
6.7
|
6.12
|
6.38
|
6.76
|
I
|
DO
|
mg/L
|
10.5
|
7.44
|
6.28
|
8.62
|
11.93
|
I
|
EC
|
µS/cm
|
12.54
|
44
|
14.41
|
19.56
|
18.69
|
S
|
ALK
|
Ppm
|
8.2
|
19.2
|
7
|
9.8
|
9.6
|
|
OM
|
Ppm
|
0.88
|
2.16
|
24
|
1.68
|
1.04
|
|
Cl-
|
Ppm
|
0.43
|
1.508
|
0.253
|
0.256
|
0
|
I
|
SO4-2
|
Ppm
|
0
|
0
|
0
|
0
|
0
|
S
|
Total Fe
|
Ppm
|
0.222
|
0.0111
|
0.215
|
0.387
|
0.305
|
|
COD
|
mg/L
|
25.96
|
31.18
|
12.56
|
0.79
|
7.54
|
|
TP
|
Ppm
|
0.01
|
0.01
|
0.02
|
0.01
|
0.01
|
I
|
Hardness
|
Ppm
|
12
|
14
|
9
|
5
|
8
|
|
Al
|
Ppm
|
0.05
|
0
|
0.23
|
0
|
0
|
I
|
Mn
|
Ppm
|
0
|
0.39
|
0
|
0
|
0
|
I
|
Mg
|
Ppm
|
0.79
|
2.55
|
0.88
|
0.95
|
1.01
|
|
Na
|
Ppm
|
0
|
1
|
0
|
0
|
0
|
|
Ca
|
Ppm
|
2.96
|
4.91
|
3.4
|
2.91
|
2.98
|
|
Cu
|
Ppm
|
0.04
|
0.05
|
0.04
|
0.05
|
0.04
|
|
Fe
|
Ppm
|
0.57
|
0.13
|
0.85
|
0.43
|
0.35
|
III
|
Average rating per point
|
I
|
I
|
I
|
I
|
I
|
Autumn Overall Ranking I
|
The turbidity presented classification in all points, as well as in general, in the Special class (0 to 20). In the correlation matrix, a trend of positive correlation was observed, TSS, TDS and OM. At point 3, turbidity and TSS showed concentrations that may be related to the topographic factor, as it is an aggradation area, characterized by sediment deposition and an increase in organic and inorganic matter in the water (Chen and Chau, 2016). Turbidity is closely associated with rain (Silva, 2013) and TSS, as the main factor responsible for turbidity is TSS (Gilvear and PettS, 1985; Grayson et al., 1996; Hannouche et al., 2011).
The TDS was within the limits of class I (200 to 300) at all sampling points. The correlation matrix showed a trend of positive correlation with EC, corroborating what was found by Atekwana et al. (2004), and with conductive ions such as Ca, Cl- and ALK (Table 4).
The color presented a classification in class II (<75) at points 2, 3 and 5 and class I at points 1 and 4. This parameter shows a tendency of positive correlation with TSS, OM, which was observed by Macedo (2004), and turbidity, as well as dissolved substances (Rocha and Costa, 2015), such as iron, Al and TP.
The pH and the DO presented a general classification in class I. The stability of these parameters is associated with the high levels of vegetal biomass, providing protection of the soil and water resources, and with the decrease of the precipitation.
Table 4 - Correlation matrix of physical and chemical parameters of surface water at UW in autumn 2019
|
DO
|
pH
|
EC
|
ALK
|
OM
|
Cl
|
Fe total
|
Cor
|
Turbidity
|
TDS
|
TSS
|
COD
|
TP
|
Hardness
|
Al
|
Mg
|
Ca
|
Cu
|
pH
|
0.70
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
EC
|
-0.36
|
0.09
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
ALK
|
-0.27
|
0.22
|
0.99
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
OM
|
-0.64
|
-0.77
|
-0.28
|
-0.39
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cl
|
-0.48
|
0.19
|
0.90
|
0.91
|
-0.19
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Fe total
|
0.43
|
-0.20
|
-0.74
|
-0.74
|
-0.08
|
-0.88
|
|
|
|
|
|
|
|
|
|
|
|
|
Cor
|
-0.60
|
-0.76
|
-0.21
|
-0.33
|
0.99
|
-0.17
|
-0.12
|
|
|
|
|
|
|
|
|
|
|
|
Turbidity
|
-0.55
|
-0.78
|
-0.25
|
-0.37
|
0.97
|
-0.24
|
-0.05
|
0.99
|
|
|
|
|
|
|
|
|
|
|
TDS
|
-0.33
|
0.13
|
0.99
|
0.99
|
-0.27
|
0.91
|
-0.79
|
-0.19
|
-0.23
|
|
|
|
|
|
|
|
|
|
TSS
|
-0.60
|
-0.74
|
-0.28
|
-0.39
|
1.00
|
-0.19
|
-0.10
|
0.99
|
0.98
|
-0.26
|
|
|
|
|
|
|
|
|
COD
|
-0.18
|
0.53
|
0.51
|
0.57
|
-0.12
|
0.78
|
-0.90
|
-0.12
|
-0.21
|
0.58
|
-0.10
|
|
|
|
|
|
|
|
TP
|
-0.61
|
-0.75
|
-0.33
|
-0.43
|
1,00
|
-0.22
|
-0.05
|
0.98
|
0.97
|
-0.31
|
1.00
|
-0.13
|
|
|
|
|
|
|
Hardness
|
-0.16
|
0.51
|
0.53
|
0.58
|
-0.09
|
0.77
|
-0.92
|
-0.06
|
-0.14
|
0.60
|
-0.06
|
0.99
|
-0.10
|
|
|
|
|
|
Al
|
-0.54
|
-0.62
|
-0.43
|
-0.51
|
0.97
|
-0.24
|
-0.06
|
0.93
|
0.91
|
-0.40
|
0.97
|
-0.04
|
0.98
|
-0.01
|
|
|
|
|
Mg
|
-0.38
|
0.12
|
0.99
|
0.98
|
-0.23
|
0.93
|
-0.82
|
-0.16
|
-0.20
|
1.00
|
-0.22
|
0.61
|
-0.27
|
0.64
|
-0.35
|
|
|
|
Ca
|
-0.55
|
-0.01
|
0.93
|
0.90
|
0.02
|
0.94
|
-0.91
|
0.08
|
0.02
|
0.94
|
0.02
|
0.69
|
-0.02
|
0.71
|
-0.09
|
0.96
|
|
|
Cu
|
-0.42
|
-0.16
|
0.71
|
0.70
|
-0.36
|
0.61
|
-0.19
|
-0.38
|
-0.40
|
0.64
|
-0.41
|
0.03
|
-0.41
|
-0.03
|
-0.51
|
0.63
|
0.51
|
|
The EC classified in the Special class (<50) showed a positive correlation trend with ALK, Cl, Mg and Ca, which are parameters associated with EC. The highest occurrence of EC was detected at point 2 and may be related to livestock activities, combined with the elevation of dissolved ion concentration (Anjinho et al., 2020).
PT, classified as class I (<0.020), showed a trend of positive correlation with turbidity and, mainly, with OM and TSS (Table 4). The reduction in total P concentration may be related to the vegetation cover, as riparian vegetation contributes to the reduction of phosphorus input into the water body (Neilen et al., 2017).
Al presented a value of <0.1 and was occasionally categorized in point 1 as class I. Between points 2, 4 and 5, the Special class (0) was identified and in point 3, Class III (<0.2), with the same classification for Fe. Both parameters showed a positive correlation with color, turbidity and TSS. Occasionally, points 1 and 3 have the highest concentrations of Fe, with a positive correlation trend, not only with color, turbidity and TSS, but also with OM and TDS, whose association of Fe with OM can increase the color (Richter and Netto, 1991). This Fe concentration may also be associated with the geology of the basin, as they are based on the Santo Anastácio Formation, which contains a thin layer of iron in its composition (Ipt, 1981).
Monitoring of surface water quality in the winter of 2019
In winter, the general classification for this station was in class I, although higher concentrations individually between some parameters are already presented in the other points, such as pH, Fe and Al (Table 5).
Table 5 - Analytical results of physical and chemical parameters of surface waters and their classification according to Resolution 357/2005 CONAMA of UW in winter.
Parameters analyzed
|
Unit
of measure
|
Monitoring points
|
Classification
by parameter
|
4
|
5
|
6
|
7
|
8
|
Physical Parameters
|
Temperature
|
°C
|
23
|
*
|
23
|
23
|
23
|
|
Color
|
Pt/Co
|
192
|
*
|
45
|
43
|
43
|
I
|
Turbidity
|
NTU
|
21.4
|
*
|
7.36
|
3.19
|
5.66
|
S
|
TDS
|
mg/L
|
9.49
|
*
|
11.19
|
8.8
|
11.29
|
I
|
TSS
|
mg/L
|
3
|
*
|
2
|
0
|
4
|
|
Chemical Parameters
|
pH
|
|
6.59
|
*
|
5.64
|
5.91
|
6.36
|
III
|
DO
|
mg/L
|
9.62
|
*
|
10.5
|
10.54
|
10.43
|
S
|
EC
|
µS/cm
|
18.97
|
*
|
22.4
|
17.6
|
22.6
|
S
|
ALK
|
Ppm
|
11.1
|
*
|
12.1
|
11.2
|
10.1
|
|
OM
|
Ppm
|
2.88
|
*
|
2.24
|
1.44
|
0.72
|
|
Cl-
|
Ppm
|
0.861
|
*
|
0.341
|
0
|
0
|
I
|
SO4-2
|
Ppm
|
0.85
|
*
|
0.168
|
0.129
|
0.149
|
I
|
Fe total
|
Ppm
|
0.616
|
*
|
0.657
|
0.417
|
0.473
|
|
COD
|
mg/L
|
11.75
|
*
|
6.33
|
0
|
0
|
|
TP
|
Ppm
|
0.03
|
*
|
0
|
0
|
0
|
I
|
Hardness
|
Ppm
|
19
|
*
|
8
|
7
|
7
|
|
Al
|
Ppm
|
2.13
|
*
|
2.31
|
1.43
|
1.53
|
IV
|
Mn
|
Ppm
|
0
|
*
|
0
|
0
|
0
|
|
Mg
|
Ppm
|
0.6
|
*
|
0.27
|
0.98
|
0.96
|
|
Na
|
Ppm
|
1
|
*
|
1
|
1
|
1
|
|
Ca
|
Ppm
|
2.18
|
*
|
2.19
|
1.95
|
2
|
|
Cu
|
Ppm
|
0
|
*
|
0
|
0
|
0
|
|
Fe
|
Ppm
|
1.62
|
*
|
4.36
|
0.52
|
0.57
|
III
|
Average rating per point
|
I
|
*
|
I
|
I
|
I
|
General Rating
Winter I
|
*dry spot.
Turbidity was present in the Special class, mainly due to low precipitation, as what occurred in autumn. This also showed a trend of positive correlation with SST (Table 6).
Color also presented a general classification in class I, except for point 1 in class II. There is a trend towards a positive correlation between this parameter and sulfate, as it is involved in the oxidation of organic matter (Ribeiro, et al., 2016), since in the process of degradation of organic matter there is a release of humic and phenolic acids responsible for increasing the color (Richter and Netto, 1991).
The TDS were identified as class I for all points, showing a trend of positive correlation with EC (Table 6), due again to the lower input of water from precipitation in the system.
Table 6 - Correlation matrix of physical and chemical parameters of surface water at UW in the winter of 2019.
|
DO
|
pH
|
EC
|
ALK
|
OM
|
Cl-
|
SO4-2
|
Total Fe
|
Color
|
Turbidity
|
TDS
|
TSS
|
COD
|
TP
|
Hardness
|
Al
|
Mg
|
Ca
|
pH
|
-0.77
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
EC
|
0.30
|
-0.16
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
ALK
|
0.09
|
-0.70
|
-0.08
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
OM
|
-0.71
|
0.09
|
-0.29
|
0.64
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cl-
|
-0.91
|
0.45
|
-0.18
|
0.31
|
0.92
|
|
|
|
|
|
|
|
|
|
|
|
|
|
SO4-2
|
-1.00
|
0.71
|
-0.34
|
0.00
|
0.77
|
0.93
|
|
|
|
|
|
|
|
|
|
|
|
|
Total Fe
|
-0.44
|
-0.07
|
0.38
|
0.61
|
0.78
|
0.75
|
0.48
|
|
|
|
|
|
|
|
|
|
|
|
Color
|
-0.99
|
0.72
|
-0.37
|
-001
|
0.76
|
0.92
|
1.00
|
0.45
|
|
|
|
|
|
|
|
|
|
|
Turbidity
|
-0.98
|
0.67
|
-0.20
|
0.05
|
0.79
|
0.97
|
0.99
|
0.60
|
0.98
|
|
|
|
|
|
|
|
|
|
TDS
|
0.30
|
-0.16
|
1.00
|
-0.08
|
-0.29
|
-0.17
|
-0.34
|
0.38
|
-0.37
|
-0.19
|
|
|
|
|
|
|
|
|
TSS
|
-0.39
|
0.62
|
0.67
|
-0.53
|
-0.08
|
0.27
|
0.31
|
0.32
|
0.29
|
0.40
|
0.67
|
|
|
|
|
|
|
|
COD
|
-0.84
|
0.33
|
-0.09
|
0.42
|
0.94
|
0.99
|
0.87
|
0.83
|
0.86
|
0.92
|
-0.09
|
0.25
|
|
|
|
|
|
|
TP
|
-0.99
|
0.72
|
-0.38
|
-0.02
|
0.75
|
0.92
|
1.00
|
0.44
|
1.00
|
0.98
|
-0.38
|
0.29
|
0.85
|
|
|
|
|
|
Hardness
|
-0.99
|
0.68
|
-0.34
|
0.05
|
0.80
|
0.95
|
1.00
|
0.51
|
1.00
|
0.99
|
-0.34
|
0.29
|
0.89
|
1.00
|
|
|
|
|
Al
|
-0.42
|
-0.14
|
0.30
|
0.69
|
0.82
|
0.75
|
0.47
|
0.99
|
0.44
|
0.58
|
0.31
|
0.22
|
0.84
|
0.43
|
0.50
|
|
|
|
Mg
|
0.19
|
0.38
|
-0.37
|
-0.80
|
-0.71
|
-0.57
|
-0.24
|
-0.95
|
-0.22
|
-0.37
|
-0.37
|
-0.08
|
-0.69
|
-0.20
|
-0.28
|
-0.97
|
|
|
Ca
|
-0.54
|
0.01
|
0.29
|
0.59
|
0.83
|
0.82
|
0.58
|
0.99
|
0.55
|
0.69
|
0.29
|
0.32
|
0.89
|
0.54
|
0.61
|
0.99
|
-0.92
|
|
Fe
|
0.07
|
-0.58
|
0.46
|
0.83
|
0.54
|
0.34
|
-0.02
|
0.85
|
-0.04
|
0.12
|
0.46
|
-0.01
|
0.48
|
-0.05
|
0.03
|
0.87
|
-0.97
|
0.79
|
The pH specifically presented a classification difference, point 1, located upstream, and point 5, close to the mouth, which were classified in class I; points 3 and 4 have a slightly acidic pH, categorized in class IV, which can be explained by the decomposition of the accumulation of leaves, vegetation branches, organic matter, resulting in the release of humic acid (Anjinho et al., 2020) from the parts highest on the terrain (headwaters). It should be noted that point 3 is in a sediment deposition area, therefore TSS tends to accumulate in this dry period, increasing concentration and decreasing transport (Stevaux and Latrubresse, 2017), which corroborates with what is indicated in the correlation matrix which showed a trend of positive correlation with the TSS, turbidity, color and SO42. The OD was generally in class I (>6 <10), and point 1 was the only one at this station classified in class I, due to a small variation in the concentration value, in which the other points were within the limits of the special class (>10).
As in autumn, EC in winter remained in the Special class. In this season, there was also a trend towards a positive correlation between EC and TDS due to the lower precipitation rate, limiting the entry of material through the runoff.
The Cl- was present in class I (<250), in points 1 and 3, and was absent in points 4 and 5. SO4-2, as well as Cl-, were present in class I, differently from autumn, where its occurrence was not identified. Both parameters tend to have a positive correlation with OM due to the dissolution of these elements in substances that compose these parameters.
Fe predominated in class III (<5.0), with the highest concentrations in points 1 and 3, which, as in the previous season, showed a trend of positive correlation with OM and TDS.
Al showed higher concentrations at all points, classified in class IV (>0.2), and similar to Fe, this element also showed a positive correlation with OM.
Monitoring of surface water quality monitoring in spring 2019
In spring it was found that point 2 was still dry, resulting from the removal of riparian vegetation. In the basin region, spring is characterized by the beginning of the rainy season, with a large accumulation of litter from the vegetation itself, as a result of previous seasons (Inkotte et al., 2022). According to data analysis, in general, all parameters showed an increase in their indices (Table 7).
Table 7 - Analytical results of physical and chemical parameters of surface waters and their classification according to Resolution 357/2005 CONAMA of UW in Spring
Parameters analyzed
|
Unit
of measure
|
Monitoring points
|
Classification
by parameter
|
4
|
5
|
6
|
7
|
8
|
Physical Parameters
|
Temperature
|
°C
|
20
|
*
|
20
|
20
|
20
|
|
Color
|
Pt/Co
|
579
|
*
|
637
|
99
|
71
|
II
|
Turbidity
|
NTU
|
49.4
|
*
|
85.7
|
4.94
|
7.95
|
I
|
TDS
|
mg/L
|
11.76
|
*
|
4.67
|
7.29
|
9.53
|
I
|
TSS
|
mg/L
|
13
|
*
|
0
|
0
|
1
|
|
Chemical Parameters
|
pH
|
|
7.08
|
*
|
5.53
|
6.13
|
6.62
|
II
|
DO
|
mg/L
|
8.78
|
*
|
8.52
|
9.5
|
10.62
|
I
|
EC
|
µS/cm
|
23.5
|
*
|
9.53
|
14.58
|
19.06
|
S
|
ALK
|
Ppm
|
8.6
|
*
|
5.9
|
9.1
|
9.9
|
|
OM
|
Ppm
|
4.64
|
*
|
4.48
|
0
|
0
|
|
Cl-
|
Ppm
|
2.152
|
*
|
0.472
|
0
|
0
|
I
|
SO4-2
|
Ppm
|
0.301
|
*
|
0.897
|
0.202
|
0.127
|
I
|
Total Fe
|
Ppm
|
4.85
|
*
|
1.574
|
1.706
|
0.739
|
|
COD
|
mg/L
|
74.28
|
*
|
9.92
|
21.06
|
0
|
|
TP
|
Ppm
|
0.07
|
*
|
0.06
|
0
|
0
|
I
|
Hardness
|
Ppm
|
1
|
*
|
3
|
26
|
8
|
|
Al
|
Ppm
|
4.34
|
*
|
11.08
|
0.58
|
0.82
|
IV
|
Mn
|
Ppm
|
0
|
*
|
0
|
0
|
0
|
-
|
Mg
|
Ppm
|
0.75
|
*
|
0.75
|
0.78
|
1.06
|
|
Na
|
Ppm
|
1
|
*
|
1
|
0
|
0
|
|
Ca
|
Ppm
|
3.16
|
*
|
2.4
|
3.26
|
4.03
|
|
Cu
|
Ppm
|
0.03
|
*
|
0.13
|
0.03
|
0.03
|
|
Fe
|
Ppm
|
4.25
|
*
|
1.83
|
1.5
|
1.21
|
III
|
Average rating per point
|
II
|
|
II
|
I
|
I
|
Spring Overall Ranking II
|
* dry spot.
The turbidity showed variations in the concentration between the sampling points, as well as in other works (Antunes et al., 2014; Rossiter et al., 2015; Amorim et al., 2017), with points 1 and 3 in class II ( 40 to 70) and points 4 and 5 in the special class.
Color proved to be general in class 2 (>75), and occasionally, except for point 4 in class I, the others were classified in class II. It can be observed that there was an increase in the concentration of this parameter in relation to previous seasons, mainly due to the increase in the concentration of dissolved substances such as sulfate, Fe and even OM, registering a trend of positive correlation between these elements (Table 8).
Table 8- Correlation matrix of physical and chemical parameters of surface water at UW in spring 2019.
|
OD
|
pH
|
EC
|
AKL
|
OM
|
Cl-
|
SO4-2
|
Total Fe
|
Color
|
Turbidity
|
TDS
|
TSS
|
COD
|
TP
|
Hardness
|
Al
|
Mg
|
Ca
|
Cu
|
pH
|
0.31
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
EC
|
0.28
|
1.00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
ALK
|
0.81
|
0.71
|
0.68
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
OM
|
-0.86
|
-0.04
|
-0.01
|
-0.73
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cl-
|
-0.57
|
0.59
|
0.62
|
-0.13
|
0.76
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
SO4-2
|
-0.74
|
-0.73
|
-0.71
|
-0.99
|
0.70
|
0.06
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Total Fe
|
-0.57
|
0.60
|
0.62
|
-0.05
|
0.65
|
0.97
|
-0.04
|
|
|
|
|
|
|
|
|
|
|
|
|
Color
|
-0.89
|
-0.15
|
-0.12
|
-0.80
|
0.99
|
0.69
|
0.77
|
0.58
|
|
|
|
|
|
|
|
|
|
|
|
Turbidity
|
-0.83
|
-0.41
|
-0.39
|
-0.93
|
0.91
|
0.42
|
0.92
|
0.29
|
0.95
|
|
|
|
|
|
|
|
|
|
|
TDS
|
0.29
|
1.00
|
1.00
|
0.69
|
-0.01
|
0.61
|
-0.71
|
0.62
|
-0.12
|
-0.39
|
|
|
|
|
|
|
|
|
|
TSS
|
-0.35
|
0.78
|
0.80
|
0.13
|
0.57
|
0.97
|
-0.20
|
0.95
|
0.48
|
0.18
|
0.80
|
|
|
|
|
|
|
|
|
COD
|
-0.51
|
0.64
|
0.66
|
0.04
|
0.57
|
0.94
|
-0.13
|
0.99
|
0.50
|
0.19
|
0.66
|
0.95
|
|
|
|
|
|
|
|
TP
|
-0.85
|
0.04
|
0.07
|
-0.68
|
1.00
|
0.81
|
0.64
|
0.71
|
0.98
|
0.87
|
0.07
|
0.63
|
0.63
|
|
|
|
|
|
|
Hardness
|
0.34
|
-0.22
|
-0.24
|
0.40
|
-0.76
|
-0.61
|
-0.44
|
-0.40
|
-0.73
|
-0.69
|
-0.23
|
-0.52
|
-0.31
|
-0.76
|
|
|
|
|
|
Al
|
-0.77
|
-0.58
|
-0.55
|
-0.97
|
0.81
|
0.24
|
0.98
|
0.11
|
0.87
|
0.98
|
-0.56
|
-0.02
|
0.00
|
0.76
|
-0.60
|
|
|
|
|
Mg
|
0.93
|
0.27
|
0.25
|
0.63
|
-0.65
|
-0.48
|
-0.53
|
-0.58
|
-0.68
|
-0.58
|
0.25
|
-0.31
|
-0.56
|
-0.65
|
0.01
|
-0.52
|
|
|
|
Ca
|
0.93
|
0.63
|
0.61
|
0.95
|
-0.74
|
-0.24
|
-0.90
|
-0.23
|
-0.80
|
-0.86
|
0.61
|
0.01
|
-0.17
|
-0.69
|
0.23
|
-0.87
|
0.85
|
|
|
Cu
|
-0.59
|
-0.81
|
-0.79
|
-0.95
|
0.56
|
-0.12
|
0.98
|
-0.24
|
0.64
|
0.85
|
-0.80
|
-0.37
|
-0.33
|
0.49
|
-0.38
|
0.94
|
-0.38
|
-0.81
|
|
Fe
|
-0.57
|
0.61
|
0.63
|
-0.09
|
0.72
|
0.99
|
0.01
|
0.99
|
0.64
|
0.37
|
0.62
|
0.97
|
0.97
|
0.77
|
-0.53
|
0.18
|
-0.52
|
-0.23
|
-0.18
|
The pH predominated in class II, point 6 was presented in class IV and the others in class I. This may be related to the physical characteristics of point 3. This parameter showed a tendency of positive correlation with EC and TDS, TSS, total Fe and Fe (Table 8), which was a correlation already observed in some parameters in previous seasons.
The DO at points 1, 3 and 4 was presented in class I and point 5 in the Special class. It was observed that there was a decrease in the concentration of this parameter in relation to previous seasons. This may be related to the increase in TSS concentration, in the surface water temperature absorbed by solids (Kannel et al., 2007; Naveedullah et al., 2016), by OM, COD and Fe, resulting in DO consumption so much so that the correlation matrix (Table 8) showed that the DO has a negative correlation tendency with the TSS, the OM, Fe and COD.
The EC remained in the Special class, as in previous seasons, and also showed a very high positive correlation trend for pH and TDS, and high for ALK, Fe, Cl, TSS and Ca parameters. This can be explained by the entry of materials into the water body due to the increase in precipitation and, consequently, the release of Fe and Ca ions, which tended to show a positive correlation.
The Cl- was another parameter that remained in the same class as autumn and was not detected at points 4 and 5. SO4-2, as well as Cl-, which remained in class I (<250), compared to the previous season.
TP specifically presented only in point 1 with class II (<0.030) and in point 3 with classification in class III (<0.05). This also showed a high trend of positive correlation with OM, which may be associated with anthropic or natural actions (Von Sperling and Chernicharo, 2002; Oliveira et al., 2017). The concentration of this element may also be associated with the accumulation of organic matter from plant material (Andrade et al., 2008), dissociation of suspended sediments and soil leaching by precipitation (Marins et al., 2007; Santos et al., 2010).
The Fe presented a general classification in class III (<5.0), with a trend of positive correlation between the color, turbidity, COD, TDS and TSS parameters, which already presented this correlation characteristic in previous seasons.
The Al remained in class IV (>0.2), having increased its concentration: in point 4, which doubled the concentration and in point 3 where it was tripled. On the other hand, points 4 and 5 showed a drop in concentration, and were identified in class III showing once more a trend of positive correlation with SO4-2, OM, color, turbidity and TP.
Monitoring of surface water quality in the summer of 2020
This season is characterized by an increase in precipitation, with an average value of 200 mm, as well as in the volume of plant density and temperature, providing the acceleration of litter decomposition processes. The general classification registered in the summer was in class III (Table 9), quite different from what was observed in the other seasons.
Table 9 - Analytical results of the physical and chemical parameters of surface water and their classification according to UW Resolution 357/2005 CONAMA in the summer.
Parameters analyzed
|
Unit of
measure
|
Monitoring points
|
Classification
by parameter
|
4
|
5
|
6
|
7
|
8
|
Physical Parameters
|
Temperature
|
°C
|
19.6
|
20
|
19.8
|
19.8
|
19.7
|
|
Color
|
Pt/Co
|
712
|
332
|
412
|
178
|
284
|
II
|
Turbidity
|
NTU
|
35.4
|
19.1
|
27.3
|
12.4
|
25.4
|
I
|
TDS
|
mg/L
|
19.75
|
24.7
|
12.65
|
10.75
|
11.15
|
I
|
TSS
|
mg/L
|
45
|
16
|
0
|
0
|
1
|
|
Chemical Parameters
|
pH
|
|
5.85
|
6.29
|
5.86
|
6.14
|
6.3
|
II
|
DO
|
mg/L
|
10.26
|
10.3
|
10.58
|
9.97
|
9.93
|
I
|
EC
|
µS/cm
|
39.5
|
49.4
|
25.3
|
21.5
|
22.3
|
S
|
AKL
|
Ppm
|
20.7
|
26.5
|
11.2
|
10.4
|
12.1
|
|
OM
|
Ppm
|
6.08
|
8.56
|
6.82
|
6.8
|
5.28
|
|
Cl-
|
Ppm
|
0.321
|
0.239
|
0.218
|
0
|
0.089
|
I
|
SO4-2
|
Ppm
|
0.278
|
0.124
|
0.123
|
0.18
|
0.08
|
I
|
Total Fe
|
Ppm
|
5.278
|
5.774
|
11.655
|
2.905
|
5.122
|
|
COD
|
mg/L
|
25.47
|
35.88
|
45.96
|
216.65
|
26.59
|
|
TP
|
Ppm
|
0
|
0.004
|
0.003
|
0
|
0.001
|
I
|
Hardness
|
Ppm
|
5
|
18
|
0
|
12
|
17
|
|
Al
|
Ppm
|
0.18
|
0
|
0.18
|
0.04
|
0.47
|
II
|
Mn
|
Ppm
|
0
|
0
|
0
|
0
|
0
|
-
|
Mg
|
Ppm
|
1.53
|
2.43
|
0.68
|
0.95
|
0.93
|
|
Na
|
Ppm
|
1
|
1
|
1
|
1
|
1
|
|
Ca
|
Ppm
|
1.48
|
2.72
|
1.51
|
1.74
|
1.61
|
|
Cu
|
Ppm
|
0.04
|
0.05
|
0.05
|
0.05
|
0.06
|
|
Fe
|
Ppm
|
20.6
|
8.19
|
0.05
|
2.75
|
4.68
|
III
|
Average rating per point
|
II
|
I
|
I
|
I
|
I
|
Overall Summer Ranking I
|
Turbidity concentrations in the summer at points 2 and 4 were in the Special class and points 1, 3 and 5 in class I. In general, with class I, there was a trend of positive correlation with TSS and Fe (Table 10). It is important to note that in this season, there were changes in land use and land cover, namely the forestry harvest near points 1 and 3, which did not show major changes such as increased concentration of TSS and OM, and may increase its concentration in the rainy season, as already observed in other works (Anjinho et al., 2020). It can be observed that changes in land use and land cover, such as harvesting activity, are related to the increase in the concentration of solids in the water (Ensign and Mallin, 2001; Lima and Zakia, 2006).
The TDS was presented in all points in class I due to the higher vegetation density in the summer. It also showed a positive correlation trend with EC, Cl-, ALK, Fe and Ca (Table 10). The highest TDS values were detected in areas containing pasture, such as points 1 and 2, places where increased TDS concentration can unbalance biochemical reactions (Wang et al., 2013).
The color showed varied concentrations at the collection points, and the highest one was in the summer. This is due to the increase in precipitation, which caused an increase in dissolved substances and organic materials, with a record of a positive correlation trend between SO4-2, TSS, Fe and Turbidity (Table 10).
Table 10 - Correlation matrix of physical and chemical parameters of surface water at UW in the summer of 2020.
The pH showed a slightly elevated acidity level, in class IV for points 1 and 3 (Table 9). This is due to the influence of increased precipitation (Damasceno et al., 2015; Alvarenga et al., 2016; Ben-Eledo et al., 2017). The pH showed a tendency of negative correlation with the OM, in such a way that when the decomposition processes accelerate, there is an increase in the pH (Table 10). Points 2, 4 and 5 were classified within the limit established for class I (Table 9). It should be noted that although points 1 and 3 have little in common in terms of land use and land cover, both showed the most altered parameters among all the analyzed stations, especially point 3.
The DO at points 1, 2 and 3 with the Special class and points 4 and 5 with class I (Table 9) indicated that there was greater water oxygenation at this station, and that may be related to the increase in water volume of precipitation (Zanata et al., 2015; Araújo et al., 2018).
The EC featured in the Special class at all points for this season. This parameter reached the highest values in this season, showing a trend of positive correlation with TDS, TSS, as well as ALK, EC, Mg and Cl- (Table 10).
The ALK showed the highest values in this season, focusing on points 1 and 2. It had a tendency towards a positive correlation with TDS, TSS, TP, Cl-, Ca and Mg (Table 10) due to increased precipitation and ion availability originating from the dissolution of rock and soils (Lima and Zakia, 2006; Cruz et al., 2016).
The Cl- and SO4-2 parameters at all points showed class I values. The sulfates detected in natural water resources are also ions that can come from the dissolution of soils and rocks (Fernandes et al., 2012). Cl- tended to have a positive correlation with turbidity, TDS and TSS, and SO4-2with color, TSS and Fe.
The TP was in the special class at points 1 and 4 and at points 2, 3 and 5 in class I. The TP showed a trend of positive correlation with the OM (Table 10). Not only P, but nitrogen and K are nutrients that may be related to the increase in water discharge, runoff, over the forest exploitation area (Malmer and Grip, 1994; Vital et al., 1999). Al resulted in the Special class (0) at point 2; class I (<0.1) at point 4; class II (>0.1) at points 1 and 3, and class III (<0.2) at point 5. In general, for summer, with class II, it showed a very high trend of positive correlation with OM, ALK, EC and DO.
Total Fe (dissolved more in suspension) showed high concentrations in this season and Fe showed higher concentrations at points 1, 2, 4 and 5, overall with class III (<5.0). This is due to natural conditions with the geological (Ipt, 1981) and pedological formation of the basin as there is an occurrence of iron concentration in the other stations.
Correlation Analysis
Water quality presents variations in the concentration of its elements depending on several factors, including land use and cover and time (Rodrigues et al., 2018). In all stations, through the correlation matrices (Tables 4, 6, 8 and 10), for example, the parameters TDS and EC presented interaction with R2 above 0.98 (Fig. 6). They were the only ones in all stations to maintain the occurrence of high R2, as they are associated with the occurrence of several parameters such as Ca, Mg, ALK, pH and Hardness. The influence of seasonality between parameters stands out, for example, between parameters such as DO x pH and TDS x ALK, as the volume of precipitation increases (Fig. 3) and the DO concentration increases due to the greater turbidity of the water, consequently increasing the concentration of dissolved salts, TDS and pH so much so that Mendes and Ferreira (2014) detected a negative correlation between precipitation and pH and attributed this result to the leaching of Cerrado soils.
The ALK and TDS parameters, in autumn, resulted in an R2 of 0.97 due to the association with EC and Ca, Mg, Cl- and Cu ions, already presented in the trend matrices. It can be inferred that this pair of parameters is correlated with seasonality, in addition to TDS and EC, as the measure that decreases the entry of water into the system, precipitation, the correlation trend is practically null.
The SO4-2 and color, in spring, resulted in R2 of 0.99, both associated with Turbidity and TDS. The pH and TDS, in spring, also resulted in R2 of 0.99, associated with Ca and Mg cations, which in turn are associated with EC and ALK parameters. It can also be observed that these associations occur between the organoleptic parameters of water. TDS and Mg also resulted in an R2 0.89, which was related to EC, ALK and TDS.
Fig. 7 presents the concentration of some of the parameters for the entire period that can be highlighted in the analysis, as demonstrated by Alvareda et al. (2020).
The quartile sampling of Fig. 7 showed that points 1, 2 and 3 were the ones that stood out due to the occurrence of concentrations between the evaluated parameters, which may be related to erosive features and anthropic interventions such as cattle raising, pasture reform and areas of silviculture harvested, given that the latter alters the concentrations of nutrients and sediments in water bodies (Rodrigues et al., 2019).
Points 1, 2 and 3 are located on pasture areas mostly intended for cattle raising, which may be influencing the increase in parameter concentrations, as the highest concentrations of TP are in these areas, as this parameter is closely associated with the analysis of the impacts of agricultural activities (Assis and Azevedo Lopes, 2017).
Another aggravating factor is the suppression of riparian vegetation, which is important in containing/barring the entry of organic and inorganic elements into the water body (Connolly et al., 2015), as riparian zones have long been known to help stabilize biodiversity and water quality (Souza et al., 2013; Fernandes et al., 2014; Keir et al., 2015).
In point 3, in addition to the influence of agriculture and livestock, there is also the action of forestry harvesting activities and the erosive processes installed in the river channel (Fig. 8) that may influence the entry of elements/materials that corroborate with the increase in the pH and concentration of turbidity and Al.
The occurrence of the concentration of some parameters not only in point 3 but also in points 1 and 2 has been observed since the first collection, such as turbidity, TDS, Al, pH and Fe. These concentrations are influenced by the chemical characteristics of the soil, with Fe (Ipt, 1981) and Al is abundant in the soils of the Brazilian cerrado.
Points 4 and 5 were the ones that presented the concentrations of the parameters with the best classifications, which may be related to the classes of land use and land cover, as these together presented the largest area of planted forests and natural vegetation. In addition, water quality may be related to several factors such as seasonality, configuration of land use and land cover, spatial and temporal scale and other intrinsic characteristics (Xiao et al., 2016).