Differences were observed among the evaluated means of the physico-chemical variables among the rivers based on the analysis of variance (ANOVA-one way) and the grouping performed by the Tukey post-test (Table 3). The municipalities of Boa Vista da Aparecida (BVA), Catanduvas (CTD) and Três Barras do Paraná (TBP) presented pH values higher than 7, while the municipalities of Cascavel (CVEL) and Toledo (TOL) presented values close to 5 (Table 3). The municipalities of Três Barras do Paraná and Santa Tereza do Oeste (STO), presented mean values of DQO greater than 70 mg/L (Table 2). Electrical conductivity showed higher values for the municipalities of Boa Vista da Aparecida, Catanduvas, Guaraniaçu (GUAR) and Três Barras do Paraná (0.08 MS/cm-1). The total dissolved solids presented higher values for the municipalities of Três Barras do Paraná (71.75 mg/L), Boa Vista da Aparecida (77.25 mg/L) followed by Catanduvas (71.00 mg/L). The municipalities of Toledo (TOL), Foz do Iguaçu (FOZ) and Guaraniaçu stood out with the highest turbidity values, however Catanduvas presented the lowest value for this variable (Fig. 2).
Table 3
Comparisons of means (one way ANOVA) of environmental variables among the municipalities evaluated. Representative differences (p < 0.05) are highlighted in bold
Municipalities | BVA | CTD | CVEL | FOZ | GUAR | MED | STO | TBP | TOL | R² | F | p |
Temp (ºC) | 23.22 ± 1.08 | 19.45 ± 0.26 | 20.9 ± 1.00 | 22.41 ± 0.98 | 17.93 ± 0.61 | 21.93 ± 0.42 | 22.52 ± 1.26 | 21.04 ± 0.05 | 20.83 ± 0.20 | 0.88 | 9.07 | 0.01 |
DO (mg L−1) | 3.43 ± 0.32 | 4.94 ± 0.35 | 10.74 ± 0.35 | 2.58 ± 0.54 | 4.84 ± 0.22 | 2.8 ± 0.57 | 2.53 ± 0.78 | 4.47 ± 0.35 | 10.59 ± 0.29 | 0.95 | 23.64 | < 0.0001 |
pH | 7.41 ± 0.28 | 7.31 ± 0.01 | 5.47 ± 0.52 | 6.32 ± 0.13 | 6.79 ± 0.44 | 6.66 ± 0.10 | 6.64 ± 0.31 | 7.27 ± 0.09 | 5.94 ± 0.26 | 0.9 | 10.21 | 0.01 |
Condut (mS/cm−1) | 0.08± 0.01 | 0.08 ± 0.01 | 0.05 ± 0.01 | 0.05 ± 0.01 | 0.08 ± 0.01 | 0.03 ± 0.01 | 0.01 ± 0.01 | 0.08 ± 0.01 | 0.02 ± 0.01 | 0.92 | 14.21 | 0.01 |
prof (m) | 0.26 ± 0.02 | 0.17 ± 0.01 | 0.41 ± 0.15 | 0.19 ± 0.15 | 0.16 ± 0.03 | 0.21 ± 0.18 | 0.2 ± 0.01 | 0.32 ± 0.10 | 0.44 ± 0.10 | 0.63 | 1.9 | 0.17 |
Tur (NTU) | 9.21 ± 0.46 | 6.07 ± 2.31 | 9.67 ± 2.31 | 13.65 ± 3.06 | 13.25 ± 1.20 | 8.91 ± 1.20 | 10.53 ± 1.51 | 9.61 ± 0.21 | 22.25 ± 1.90 | 0.91 | 11.84 | 0.01 |
Chlorophyll (µg/L) | 0.56 ± 0.01 | 0.56 ±0.01 | 2.88 ± 2.72 | 1.72 ± 1.64 | 1.00 ± 0.62 | 0.56 ± 0.01 | 1.48 ± 1.30 | 0.76 ± 0.28 | 1.68 ± 0.33 | 0.44 | 0.88 | 0.56 |
Ecoli (NMP/100mL) | 428.50 ± 78.48 | 445.00 ± 154.14 | 663.00 ± 291.32 | 314. 50 ± 19.09 | 4695.50 ± 5612.30 | 2772.5 ± 2600.03 | 222.5 ± 142.12 | 250.5 ± 34.64 | 1118. 00 ± 362.03 | 0.49 | 1.09 | 0.44 |
Colt (NMP/100mL) | 9208 ± 4471.03 | 17154.00 ± 9958.89 | 4865.00 ± 3323.40 | 16999.50 ± 4049.60 | 10112.00 ± 0.001 | 17697 ± 50 ± 9190.27 | 2907.50 ± 764.38 | 9393.00 ± 8680.44 | 14833.50 ± 986.41 | 0.6 | 1.72 | 0.21 |
BOD (mg/L) | 1.30 ± 0.36 | 1.00 ± 0. 01 | 1.68 ± 0.82 | 1.75 ± 1.06 | 1.76 ± 0.14 | 1. 05 ± 0.08 | 1.45 ± 0.64 | 1.00 ± 0.01 | 1.72 ± 0.17 | 0.42 | 0.82 | 0.6 |
DQO (mg/L) | 67.50 ± 3.53 | 58.33 ± 2.35 | 41.66 ± 9.42 | 16.66 ± 11.78 | 63.33 ± 14.14 | 61.67 ± 14.14 | 71.66 ± 2.35 | 77.50 ± 5.89 | 25.83 ± 3.53 | 0.91 | 11.43 | 0.01 |
TP (mg/L) | 0.02 ± 0.01 | 0.02 ± 0.02 | 0.01 ± 0.01 | 0.02 ± 0.02 | 0.02 ± 0.05 | 0.02 ± 0.02 | 0.01 ± 0.02 | 0.03 ± 0.06 | 0.04 ± 0.02 | 0.69 | 2.52 | 0.09 |
Nitrate (mg/L) | 0.09 ± 0.07 | 1.00 ± 0.42 | 1.25 ± 0.49 | 1.25 ± 0.40 | 0.80 ± 0. 42 | 1.00 ± 0.01 | 0.55 ± 0.07 | 1.75 ± 0.49 | 1.80 ± 0.14 | 0.71 | 2.74 | 0.07 |
Nitrogen ammonia (mg/L) | 0.001 ± 0.01 | 0.01 ± 0.01 | 0.05 ± 0.07 | 0.17 ± 0.25 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.02 ± 0.01 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.44 | 0.89 | 0.55 |
Orthophosphate (mg/L) | 0.01 ± 0.01 | 0.01 ± 0.02 | 0.02 ± 0.01 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.01 ± 0.01 | 0.86 | 6.81 | 0.01 |
TS (mg/L) | 77.25 ± 6.72 | 71.00 ± 4.95 | 40.00 ± 3.53 | 41.50 ± 6.36 | 67.50 ± 12.02 | 48.75 ± 5.30 | 40.50 ± 8.48 | 71.75 ± 10.96 | 21.57 ± 2.47 | 0.09 | 13.34 | 0.01 |
Rainfall (mm) | 5.02 | 3.81 | 3.81 | 2.87 | 2.6 | 2.54 | 3.81 | 5.02 | 2.84 | - | - | - |
Stream flow (m³/s) | 0.22 ± 0.68 | 0.17 ± 0.17 | 0.41 ± 0.18 | 0.10 ± 0.06 | 0.08 ± 0.04 | 0.06 ± 0.03 | 0.19 ± 0. 04 | 0.1 ± 0.06 | 1.81 ± 1.68 | 0.63 | 1.91 | 0.17 |
The principal component analysis (PCA) for environmental variables summarized 49.77% of the total variability of the data sampled in the first two axes (Fig. 2). The dispersion of the scores of the sites sampled in these axes showed a separation in the diagram of the sampling municipalities, suggesting some similarities among them (Fig. 2). The first PCA axis explained the variability mainly in relation to chlorophyll a (correlation value: 0.30) and turbidity (0.32) positively for the municipalities of Cascavel and Toledo; and pH (-0.37), total solids (-0.37) and DQO (-0.32) negatively. This axis is responsible for the samplings of Guaraniaçu, Três Barras do Paraná, Catanduvas, Medianeira and Boa Vista da Aparecida (negatively), due to the similarity of the factors of higher correlation (Figure 2). The second axis is positively related to Ammoniacal Nitrogen (0.51) Total phosphorus (0.37) and Orthophosphate (0.32), and negatively by Dissolved oxygen (-0.38), depth (-0.364) and DQO (-0.25). This axis isolates the sampling site of the municipality of Foz do Iguaçu (5,00) positively and the sampling site of the municipality of Cascavel (-2.55) negatively, highlighting them from the others as a function of discrepant values before the variables with higher correlation (Fig. 2).
When evaluated in a multivariate manner, the environmental variables that characterize water quality indicate a representative difference as a function of the municipalities according to PERMANOVA (Gl: 8; R²: 0.73; F: 3.10; p-valor: 0.001). This factor effectively confirms the statistical difference in the water quality of the environments as indicated in the ordination represented by PCA (Fig. 2).
Among the watersheds evaluated, there was predominance of the gently undulating (3-8% of slope), being more representative in the municipalities of Foz do Iguaçu (70.86%) (Fig. 3A), Três Barras do Paraná (60.80%) (Fig. 3B), Medianeira (56.20%) (Fig. 4A), Santa Tereza do Oeste (53.17%) (Fig. 3D) and Toledo (52.85%) (Fig. 4B) (see Table 4). Then the undulating class (8 - 20% of slope), with predominance in the municipalities of Catanduvas (58.06%) (Fig. 3C), Cascavel (53.27%) (Fig. 3E), Boa Vista da Aparecida (49,55%) (Fig. 3F) and Guaraniaçu (47.63%) (Fig. 4C) (Table 4). The watersheds with steeper relief, represented by the strongly undulating class (20 - 45% of the slope) were Guaraniaçu (38.43%), Boa Vista da Aparecida (29.65%) and Catanduvas (21.03%). On the other hand, the watersheds with lower slopes, considered flat (0 - 3% of slope) were Santa Tereza do Oeste (29.60%), Três Barras do Paraná (16.40%), Foz do Iguaçu (9.95%) and Toledo (5.02%).
Table 4
Percentage of the slope classes of the watersheds of the municipalities of western Paraná-BR
Slope Classes | BVA | CVEL | CTD | FOZ | GUA | MED | STO | TBP | TOL |
(%) | (%) | (%) | (%) | (%) | (%) | (%) | (%) | (%) |
Plan | 0.6 | 2.42 | 1.14 | 9.95 | 0.53 | 4.90 | 29.60 | 16.40 | 5.02 |
Gently undulating | 20.20 | 37.26 | 19.77 | 70.86 | 13.36 | 56.20 | 53.17 | 60.80 | 52.85 |
Strongly Undulating | 49.55 | 53.27 | 58.06 | 19.13 | 47.63 | 37.10 | 17.00 | 22.30 | 41.35 |
Mountainous | 29.65 | 6.94 | 21.03 | 0.06 | 38.43 | 1.70 | 0.23 | 0.50 | 0.78 |
Total | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
Regarding the soil use and occupation, the most prominent class is agricultural (Fig. 5, Fig. 6, Table 5), being predominant in the municipalities of Boa Vista da Aparecida (70.18%) (Figure 5F), Toledo (68.90%) (Fig. 6B), Catanduvas (62.24%) (Fig. 5C), Foz do Iguaçu (56.64%) (Fig. 5A), Três Barras do Paraná (56.03%) (Fig. 5B), Guaraniaçu (55.48%) (Fig. 6C) and Medianeira (54.31%) (Fig. 6B). Observing the territorial extension of the agricultural class, the watersheds that have the largest areas are: Toledo with 63.62 km², Santa Tereza do Oeste with 45.19 km² and Cascavel with 21.13 km².
As far as the forest class is concerned, the watersheds that present the largest areas are Santa Tereza do Oeste (55.08%) (Figure 5D), Três Barras do Paraná (43.02%) and Guaraniaçu (39.64%), and in the other municipalities, less than 30% of the area was represented by this class. In the context of territorial extensions, the watersheds that have larger forest areas are: Santa Tereza do Oeste (59.15 km²), Toledo (12.65 km²) and Cascavel (12.42 km²).
In the urban area class, the watersheds that have the larger territorial extension are: Cascavel (16.15 km²) (Figure 5E), Toledo (15.70 km²) and Medianeira (9.66 km²). The watersheds that have higher percentages of this class are: Cascavel (32.12%), Medianeira (31.96%) and Foz do Iguaçu (23.26%). On the other hand, the watersheds that have lower percentages of urban area are: Três Barras do Paraná (0.74%), Boa Vista da Aparecida (0.93%), Santa Tereza do Oeste (2.79%), Guaraniaçu (4.69%) and Catanduvas (7.86%).
It is important to emphasize that all the collection points are located in a forest region, however, all the municipalities have at least one of the points located near the agricultural region. Some municipalities have urban areas close to the collection points, namely: Toledo (TOL_P2), Santa Tereza do Oeste (STO_P1 and STO_P2), Medianeira (MED_P1), Foz do Iguaçu (FOZ_P1 and FOZ_P2) and Cascavel (CVEL_P1). It is important to highlight that in Cascavel and Toledo there are mining areas, and that in Cascavel one of the collection points is located near this region (CVEL_P2).
Table 5
Areas and percentage of the Use and Occupation of watersheds classes of the municipalities of western Paraná-BR
Use and occupation | BVA | CVEL | CTD | FOZ | GUA | MED | STO | TBP | TOL |
Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % |
Agricultural | 20.3 | 70.18 | 21.13 | 41.73 | 15.10 | 62.2 | 10.9 | 56.6 | 11.6 | 55.5 | 16.4 | 54.31 | 45.19 | 42.07 | 6.86 | 56.03 | 63.62 | 68.90 |
Water | 0.28 | 0.74 | 0.40 | 0.80 | 0.04 | 0.14 | 0.09 | 0.49 | 0.04 | 0.19 | 0.04 | 0.15 | 0.07 | 0.06 | 0.02 | 0.21 | 0.27 | 0.30 |
Urban Area | 0.33 | 0.93 | 16.15 | 32.12 | 1.89 | 7.86 | 4.41 | 23.3 | 0.97 | 4.69 | 9.66 | 31.96 | 3.01 | 2.79 | 0.09 | 0.74 | 15.70 | 16.98 |
Forest | 10.2 | 28.15 | 12.42 | 24.88 | 7.20 | 29.8 | 3.72 | 19.6 | 8.26 | 39.6 | 4.11 | 13.58 | 59.15 | 55.08 | 5.23 | 43.02 | 12.65 | 13.74 |
Mining | 0 | 0 | 0.23 | 0.47 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0.07 | 0.08 |
Total | 36.1 | 100 | 50.33 | 100 | 24.2 | 100 | 19.1 | 100 | 20.8 | 100 | 30.3 | 100 | 107.4 | 100 | 12.20 | 100 | 92.31 | 100 |
The municipalities fit within the same macro-region of the state, with similar climatic characteristics. The predominant climatic type identified, according to the Brazilian climate classification by Köppen, adapted by Alvares et al. (2013) was CFA, characterized as subtropical, with a mean temperature in the coldest month less than 18 ºC and in the hottest month with a temperature higher than 22 ºC. Only the municipality of Catanduvas presented two climatic types, CFA and CFB, classified as temperate itself, with a mean temperature below 18 ºC in the coldest month and in the warmest month, a mean temperature below 22 ºC (EMBRAPA 2012).
The fragility maps indicate that the predominant class is the intermediate class (Fig. 7, Fig. 8, Table 6), being the watersheds with predominance of this Boa Vista da Aparecida (94.94%) (Fig. 7F), Toledo (90.93%) (Fig. 8B), Santa Tereza do Oeste (87.27%) (Fig. 7D) and Medianeira (83.80%) (Fig. 8A). It is noteworthy that areas with very high fragility were not found in all the evaluated watersheds, highlighting that in the watershed of the municipality of Foz do Iguaçu (Fig. 7A) no areas with high fragility were found either.
The classes found with the lowest percentages in the watersheds were very low and high classes. The watersheds with the lowest percentages of very low class are: Toledo (0.05%), Medianeira (0.07%), Boa Vista da Aparecida (0.08%). Whereas, the watersheds with the lowest percentages of very low class are: Três Barras do Paraná (0.49%) Guaraniaçu (0.34%) and Santa Tereza do Oeste (0.21%). Regarding the high class, the watersheds that have the largest areas are: Guaraniaçu (1.34%), Catanduvas (0.33%) (Figure 5B), and Cascavel (0.26%) (Fig. 7E), the watersheds that have lower percentages of high class are: Foz do Iguaçu (0.00%), Toledo (0.02%) and Santa Tereza do Oeste (0.02%).
Table 6
Areas and percentage of the Environmental Fragility of watersheds classes of the municipalities of western Paraná-BR
Fragility | BVA | CVEL | CTD | FOZ | GUA | MED | STO | TBP | TOL |
Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % | Km² | % |
Very Low | 0.03 | 0.08 | 0.08 | 0.16 | 0.04 | 0.16 | 0.02 | 0.16 | 0.07 | 0.16 | 0.02 | 0.07 | 0.23 | 0.21 | 0.06 | 0.49 | 0.05 | 0.05 |
Low | 1.75 | 4.85 | 13.68 | 27.18 | 4.77 | 19.69 | 3.63 | 19.69 | 4.33 | 19.69 | 4.81 | 15.90 | 13.42 | 12.49 | 3.27 | 26.80 | 8.30 | 8.99 |
Intermediate | 34.26 | 94.88 | 36.44 | 72.40 | 19.34 | 79.82 | 15.46 | 79.82 | 16.15 | 79.82 | 25.35 | 83.80 | 93.75 | 87.27 | 8.85 | 72.54 | 83.94 | 90.93 |
High | 0.07 | 0.19 | 0.13 | 0.26 | 0.08 | 0.33 | 0 | 0 | 0.28 | 1.34 | 0.07 | 0.23 | 0.02 | 0.02 | 0.02 | 0.16 | 0.02 | 0.02 |
Very High | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Total | 36.11 | 100 | 50.33 | 100 | 24.23 | 100 | 19.1 | 100 | 20.8 | 100 | 30.3 | 100 | 107.4 | 100 | 12.20 | 100 | 92.3 | 100 |
Environmental fragility presented significant dependence on temperature and pH variables, and the higher the rate of, the higher temperatures and lower pH are observed (Table 7). Another point to be highlighted is E. coli and COD, which, although not reaching p < 0.05, pointed to a tendency toward higher concentrations of E. coli and lower COD for higher fragilities (Table 7).
Table 7
Comparison of limnological variables as a function of the percentage of occurrence of the environmental fragility classes. (T water: Water temperature, DO: Dissolved oxygen, Condut: conductivity: electrical conductivity, Prof.: Depth, Tur: Turbidity, CL-a: Chlorophyll; Eci: Escherichiacoli, TC:total coliforms, BOD: biological oxygen demand, COD: chemical oxygen demand, TP: Total phosphorus, N03: nitrate, TN: Total Kjeidahl Nitrogen, P04: orthophosphate and TS: Total solids) measured in the eighteen sampling stations of urban rivers in the western region of Paraná
standardized coefficient | Temp | DO | pH | Condut | Prof | Tur | Chlorophyll | Ecoli | Colt | BOD | COD | TP | Nitrate | | Ammoniacal Nitrogen | Orthophosphate |
Very Low | 0.043 | -0.436988 | 0.7865284 | 0.272 | -0.069 | -0.097 | -0.392 | -0.179 | -0.390 | -0.322 | 0.854 | -0.118 | 0.116 | | -0.374 | 0.359 |
Low | 2.309 | 0.8522065 | -3.7940966 | -2.479 | 2.034 | 3.048 | 2.286 | 1.325 | -1.969 | 2.684 | -1.453 | 0.567 | 0.894 | | 1.444 | -3.321 |
Intermediate | 2.627 | 0.4201527 | -3.1369079 | -2.546 | 1.890 | 3.344 | 1.824 | 1.347 | -2.032 | 2.614 | -0.952 | 0.433 | 0.682 | | 1.041 | -3.016 |
High | -0.534 | 0.0784789 | -0.1753511 | 0.156 | -0.206 | 0.247 | 0.019 | 0.753 | -0.034 | 0.400 | -0.008 | -0.242 | -0.351 | | -0.087 | 0.088 |
R² | 0.721 | 0.142 | 0.606 | 0.354 | 0.176 | 0.256 | 0.232 | 0.412 | 0.191 | 0.191 | 0.479 | 0.095 | 0.179 | | 0.176 | 0.359 |
F | 8.400 | 0.537 | 4.993 | 1.781 | 0.695 | 1.119 | 0.983 | 2.276 | 0.770 | 0.768 | 2.991 | 0.340 | 0.708 | | 0.694 | 1.819 |
P value | 0.001 | 0.711 | 0.012 | 0.193 | 0.609 | 0.389 | 0.450 | 0.117 | 0.564 | 0.565 | 0.059 | 0.846 | 0.601 | | 0.609 | 0.185 |