Environmental Risk Assessment of Accidental Pollution Incidents in Drinking Water Source Areas: A Case Study of the Hongfeng Lake Watershed, China

Accidental pollution incidents have caused a major threat to water safety of drinking water sources. However, few studies have focused on quantitative risk assessment of pollution incidents in a watershed which contains drinking water sources. A coupling model consisting of the Seveso III Directive, SWAT, and MIKE21 models was constructed for risk assessment of sudden pollution incidents at the watershed scale. The potential hazard of risk sources (e.g., industrial enterprises), the vulnerability of risk receptors (e.g., drinking water intakes), and the environmental risk of different sub-regions of the watershed were evaluated by this model. In addition, a case study was applied in Hongfeng Lake watershed (HLW), where the Hongfeng Lake drinking water source is located. The results showed that about 68% of the industrial enterprises in the HLW were potentially hazardous according to the Seveso III Directive, including 5 high hazard enterprises, 13 medium hazard enterprises, and 37 low hazard enterprises, most of which were concentrated in the coal mining, chemical production, and building material industries. The HLW was divided into the Yangchang River watershed (YRW), the Maiweng River watershed (MRW1), the Maxian River watershed (MRW2), the Houliu River watershed (HRW), and the lake area by the hydrological characteristics, among which, the vulnerability index of YRW was the largest. Besides, it was essential to consider the vulnerability assessment of drinking water intakes when conducting an environmental risk assessment in the HLW. Regional environmental risk grade of YRW, MRW1, MRW2, HRW, and the lake area was high, medium, low, low, and none, respectively. The environmental risk assessment results showed good consistency with the pollution characteristics and spatial distribution of industrial enterprises in the HLW. Furthermore, the theory of a three-level prevention system for “risk sources–water body connection–water intakes” was proposed for environmental risk management in the HLW. Overall, the case study in the HLW indicated that the coupling model proposed in this study had a good compatibility for environmental risk assessment of sudden water pollution incidents in a watershed.

Iron Isotopic Composition of Suspended Particulate Matter in Hongfeng Lake

The geochemical study of iron isotopes is of great significance to deeply understand the surface material circulation process and its environmental effects in surface and subsurface environments. Eutrophication lakes are an important part of the surface and subsurface environment; however, knowledge of the geochemical behavior and fractionation mechanism of iron isotopes in the biogeochemical cycling of eutrophication lakes is still scarce. In this study, a eutrophic lake with seasonal anaerobic characteristics (Hongfeng Lake) was selected as the study object to systematically analyze the iron isotope composition of suspended particles in lake water in different seasons as well as examining suspended particles in the main tributaries, sediments, pore water, planktonic algae, and other samples. The results show that the value of δ56Fe in Hongfeng Lake is between −0.85‰ and +0.14‰, and the value of δ56Fe has a high linear correlation with Fe/Al, indicating that the continental source material carried by the main inflow tributaries of the lake has an important influence on the source of iron in the lake. At the same time, Hongfeng lake is a medium eutrophication lake. Algal bloom and the content of chlorophyll a (Chl-a) is high, combined with the high correlation between Chl-a and the value of δ56Fe, which indicate that the growth of algae has an important influence on the change of iron isotope composition of suspended particles matter (SPM) in lake water and the adsorption and growth absorption of Fe by algae is the main reason for the change of the value of δ56Fe, so Fe isotope can be used to trace the lake’s biological action. For the lake and its inflow tributaries, δ56Fe values are higher in summer than those in winter. And the δ56Fe value of SPM in lake that varies with depth is more obvious in summer than in winter. In addition, there is an obvious thermocline in summer, which leads to hydrochemical stratification. Moreover, according to a linear correlation analysis, the content of DOC (dissolved organic matter) in Hongfeng Lake’s upper and lower waters, respectively, has a high correlation with the value of δ56Fe. Additionally, in the upper water, it is positively correlated, while on the bottom, there is a negative correlation relationship, which indicates that the difference in algae metabolism patterns between the upper and lower water bodies of Hongfeng Lake plays an important role in the iron isotope composition of suspended particulate matters (SPM). The composition of the Fe isotope in SPM is changed by organic adsorption and growth absorption of algae in upper water. With an increase in depth, the degradation process becomes the main one. In addition, the value of δ56Fe is low and Fe/Al is high in the water bottom, which indicates that “ferrous-wheel” cycle form at the bottom of the water.

Nitrate dynamics during impoundment and flood periods in a subtropical karst reservoir: Hongfeng Lake, Southwestern China

Endogenous nitrogen contribute a high proportion of nitrate to the lake/reservoir system, particularly in impoundment period.

Accumulation of metals in zooplankton from karst plateau reservoirs with different eutrophic status in Guizhou Province, P. R. China

Metal concentrations in large zooplankton from three karst reservoirs with different eutrophic status (Hongfeng Lake reservoir, Baihua Lake reservoir, and Aha reservoir) in Guizhou Province, China, were investigated. Samples of zooplankton were collected in 2014 and 2015. It was found that accumulation of metals in zooplankton was significantly correlated with Chl-a (chlorophyll a), which can be attributed to the characteristic distribution of species of phytoplankton. A low concentration of metals in water means a higher bioaccumulation factor (BAF) and a stronger transfer to zooplankton via the trophic chain, and hence a higher ecological risk. Zooplankton in the eutrophic Aha reservoir had lower concentrations of Fe (mean 1264.25 mg/kg) than in Hongfeng (mean 2566.07 mg/kg) and Baihua (2246.87 mg/kg) in 2014-2015, because of high TP (Total Phosphorus) concentration, which has an affinity with suspended particles matter. A high level of Cd (mean 0.62 mg/kg) was found in Hongfeng. This study shows that zooplankton in the eutrophic Aha reservoir had higher concentrations of metals (Mn, mean 590.47 mg/kg; Pb, mean 7.6 mg/kg; Cr, mean 26.31 mg/kg; Ni, mean 8.54 mg/kg; Zn, mean 225.73 mg/kg; and Cu, mean 238.33 mg/kg) than in the mesotrophic Hongfeng and Baihua reservoirs. Thus, the eutrophic status was significantly, positively correlated with high concentrations of metals in the zooplankton, as also observed in other reservoir studies.