| Luhun Reservoir will deliver domestic and industrial water to Zhengzhou and its surrounding cities and counties,so the quality of water of Luhun Reservoir is related to the health and safety of residents.Luhun Reservoir is located downstream of Luanchuan County,which has many mineral resources,wastewater and waste materials containing heavy metals produces by mining enter the Luhun Reservoir along with the Yihe river,and then precipitate into the sediment.When the external conditions change,the heavy metals in the sediment will be released into the water again.Heavy metals are toxic,easy to accumulate and difficult to degrade,so it is of great significance to study the sediment of Luhun reservoir for pollution control and management.In order to understand the content,spatial distribution,chemical fraction,pollution risk,toxicity,etc.collected sediment from Luhun reservoir in Luoyang City in 2018.Through the determination of heavy metal content and its occurrence form in the sediment,the pollution risk and toxicity were evaluated by the methods of geoaccumulation index and Sediment quality guideline.The evaluation results show that:?1?The average contents of heavy metals Cd,Cr,Cu,Ni,Pb,and Zn in the sediments of Luhun Reservoir are 1.49,54.2,48.18,24.03,166.31,157.38 mg·kg-1,respectively.Among them,Cd,Cu,Pb,and Zn are higher than the background values,which are 8.76,1.99,6.46,and 2.344 times,respectively,and there is a significant accumulation of heavy metals.This is similar that the spatial distribution of the six heavy metals in the sediments.The content of heavy metals in the dam area is higher than that near the entrance of the reservoir,that is,the content of heavy metals in the downstream direction increases gradually.?2?The BCR continuous extraction method was used to analyze the chemical fraction of six heavy metal in the sediments of Luhun Reservoir.The results showed that Cd was mainly in the acid extractable fraction?62.96%?,and it was extremely easy to release to water when external conditions changed,followed by a reducible fraction?24.38%?.Pb is mainly a reducible fraction?64.11%?.Cu and Zn are mainly a reducible fraction and a residue fraction?32.56%?42.77%?.Cr and Ni are mainly in the residue fraction?78.32%,58.49%?,and the potential hazard is low and it is not easy to release.?3?The results of the geoaccumulation index method show that the order of pollution levels of different heavy metals is:Cd?2.4?>Pb?2.0?>Zn?0.6?>Cu?0.3?>Ni?-1?=Cr?-1?,Cd For heavy pollution,Pb is medium-strong pollution,and the evaluation results of heavy metals by the enrichment factor are similar to the geoaccumulation index.The potential ecological risk index method shows that the average ecological risk in the Cd is a strong ecological risk,and other metals are light ecological.Risk;the average value of the comprehensive potential ecological risk index?RI?reaches 312.94,reaching a high level of ecological risk,of which Cd is the main contributing factor.In the Sediment quality guideline,Pb will adversely affect benthic organisms,and the remaining five heavy metals may It has a toxic effect on aquatic life.In the evaluation of toxic factors,Pb is the most important contributing factor.In the risk assessment code,Cd has a high risk?62.96%?,and Cu,Pb and Zn are medium risks?18.01%?18.89%?Ni is low risk?9.16%?and Cr is risk free?0.82%?.Cd and Pb should be the key heavy metals that are currently concerned.?4?In the analysis of sources,Cd,Cu,Pb,and Zn are derived from anthropogenic sources,Cr and Ni are mainly derived from natural activities such as natural weathering of rocky soil,and TN and TC are derived from agricultural pollution sources.In summary,the main pollutants of heavy metals in the sediments of Luhun Reservoir are Cd and Pb,and the area near the dam in the reservoir area should be prioritized as an area for environmental governance and management. |
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