Effects of acid mine drainage on photochemical and biological degradation of dissolved organic matter in karst river water

Dissolved organic matter(DOM)can be removed or transformed by photochemical and biological processes,producing the negative effect of transforming organic carbon into inorganic carbon,which plays a vital role in the karst carbon cycle.However,acid mine drainage(AMD)will affect this process,so the degradation of DOM in karst river water(KRW)needs to be studied in this context.In this study,to reveal the evolution processes of DOM under photochemical and biological conditions in AMD-impacted KRW,AMD and KRW were mixed in different ratios under conditions of visible light irradiation(VL),biodegradation(BD),ultraviolet irradiation(UV)and ultraviolet irradiation+biodegradation(UV+BD).The average DOC concentrations in samples after mixing AMD and KRW in different proportions decreased significantly(by 23%)in UV+BD,which was 1.2–1.4 times higher than under the other conditions and would lead to a significant release of inorganic carbon.Further analysis of the fluorescence parameters via parallel factor analysis(PARAFAC)revealed that the DOM fluorescence components in AMD comprised mainly protein-like substances derived from autochthonous components,while the DOM fluorescence components in KRW were mainly humic-like substances with both autochthonous and allochthonous sources.Therefore,AMD could promote both the photochemical and biological degradation of DOM in karst receiving streams,resulting in the conversion of DOC to inorganic carbon.The results showed that the synergistic effects of UV+BD and AMD accelerated the degradation of DOM and the release of inorganic carbon in KRW,thus affecting the stability of the karst carbon cycle.

Human health ambient water quality criteria for 13 heavy metals and health risk assessment in Taihu Lake

Heavy metals are widely concerning because of their toxicity,persistence,non-degradation and bioaccumulation ability.Iluman health ambient water quality criteria(AWQC)are specific levels of chemicals that can occur in water without harming human health.At present,most countries do not consider the effects of aquatic vegetables in deriving human health AWQC.Therefore,the intake of aquatic vegetables(Brasenia schreberi)was added to the derivation of human health AWQC and a health risk assessment for 13 heavy metals in Taihu Lake.The human health AWQC(consumption of water,fish and aquatic vegetables)values of 13 heavy metals ranged from 0.04(Cd)to 710.87μg/L(Sn),and the intake of B.schreberi had a very significant effect on the human health AWQC for Cu,with a more than 62-fold difference.The hazard quotients of As(2.8),Cd(1.6),Cr(1.4)and Cu(4.86)were higher than the safe level(HQ=1),indicating that As,Cd,Cr and Cu in Taihu Lake posed a significant health risk.Sensitivity analysis showed that the contribution rate of B.schreberi intake to the human health risk from Cu was 91.6%,and all results indicated that the risk of Cu in B.schreberi to human health should be of particular concern.This study adds the consideration of aquatic vegetable consumption to the traditional method of human health AWQC derivation and risk assessments for the first time,and this approach can promote the development of risk assessments and water quality criteria.