Study On Heavy Metal Pollution Characteristics And Testing Standards Of Typical Crab Pond Bottom Mud

Heavy metal pollution has become a global problem that can not be ignored.Whether it is air deposition or polluted wastewater discharge,the final air heavy metal pollution and water heavy metal pollution will eventually enter the soil(sediment).Because of the characteristics of the structure of the soil(sediment),for heavy metals,the soil(sediment)is both a "source"and a "sink",that is,heavy metals and may be adsorbed in the soil(sediment),or can change with the environment(e.g.,Temperature,PH,etc.)released into the water,air,etc.It can also be absorbed by passive plants and finally enter the human body through the food chain,resulting in the accumulation of heavy metals in the human body.Therefore,the detection of heavy metals in soil(sediment)is particularly important.As the only heavy metal mercury among heavy metals that can spread its effects globally,with the implementation of the Minamata Convention,The corresponding laws and regulations and the standardization of monitoring limits will play a good guiding role in the standardization of mercury-related industries in China.Therefore,this paper studies the characteristics and risk assessment of sediment pollution in typical crab ponds around Taihu Lake,and summarizes the current mercury laws and regulations and monitoring limits.The main results are as follows:(1)The metal content was determined by plasma emission spectrometry(ICP-OES)in four typical crab ponds around Taihu Lake and river sediment near crab ponds.According to the content of heavy metals,the pollution status of heavy metals was evaluated by common evaluation methods and the corresponding evaluation suggestions were given,the average concentration of heavy metals was as follows:Na>Al>Fe>Mg>Mn>Ba>Sr>Zn>Cr>Li>Ni>Cu>Sb>Pb>As>Co>Cd.Compared with other areas,the concentrations of Zn and Cu are significantly higher than those in other areas,which may be due to the fact that ZnSO4,CuSO4 is a common insecticide used in aquaculture and finally deposited in sediment,resulting in the content of Zn,Cu is significantly higher than that of other heavy metals.By comparing the total concentration of heavy metals at the sampling sites,it is found that the concentrations of heavy metals in the sediment do not vary greatly with the location of the sampling points,and there is no significant difference in the concentrations of heavy metals between the nearby rivers and the four typical crab ponds.Basically at the same level.According to the "Environmental requirements of pollution-free Aquatic products producing area",this study used the geoaccumulation index method and the potential ecological risk index(RI)to Cu,Zn,Cr,Pb,Cd,respectively.The six most harmful and common heavy metal pollution levels of As were evaluated.The results of these two average methods show that Cd is an important factor in the pollution of crab ponds and nearby rivers.At the same time,since the TOC content often affects the content of heavy metals in the sediment,we have done TOC testing.Through positive correlation studies,it was found that the TOC content of the sediment in the sample did not significantly affect the heavy metal content,and the TOC content of the ground was in a relatively stable range compared with other regions.