Fig 1.
Map illustrating the study area and the positions of sampling sites.
Notably, S1-S3 and G1-G4 represent sampling sites upstream, while S4-S7 and G5-G8 denote sampling sites downstream. The land cover mapping results from Yang and Huang’s work in 2021 [31].
Table 1.
Statistics of heavy metal elements and physicochemical parameters in dry and wet seasons of the basin.
Fig 2.
Seasonal and spatial variations in the concentrations of nine heavy metal elements in the basin.
In this figure, “WHO” denotes the standard limits for heavy metals as provided by the WHO.
Fig 3.
Contribution of APCS-MLR model (a: dry season; b wet season) and PMF model (c: dry season; d wet season) extraction factors to heavy metals.
Fig 4.
Co-occurrence network of water chemistry factors with heavy metals in dry (a) and wet (b) seasons. In the co-occurrence network, the size of the nodes is related to the value; green lines indicate negative correlations and red lines indicate positive correlations; line widths indicate the magnitude of the correlation coefficients; * indicates that the correlation is significant at the P < 0.05 level and ** indicates that the correlation is significant at the P < 0.01 level.
Fig 5.
Non-cancer (a) and cancer (b) risk of source-specific heavy metals at each sampling site. N is for natural sources; I is for sources of industrial waste; and M is for sources of metal smelting.
Fig 6.
The proportion of source-specific contributions to human health risk in the dry (left) and wet (right) seasons.