The Environmental Geochemistry Of Trace Elements In The Middle Reaches Of The Huaihe River,Anhui,China

A total of 211 water samples from 53 key sampling points at four different depths(0m,2m,4m,8m)in each site,54 surface sediment samples,and two sediment cores were collected from Zhengyangguan to Bengbu sluice in the middle reaches of the Huaihe River,Anhui,China.Trace element concentrations(Cu,Cu,Pb,Zn,Ni,Co,Cr,Cd,As,Mn,Fe,Al,B,Ba,Mg),geochemical fractionations of trace elements(weak acid soluble,reducible,oxidizable,and residual),and stable Pb isotopes(204Pb,206Pb,207Pb,208Pb)in the samples were extracted by using mixed acid digestion and the modified BCR sequential extraction procedure,then were determined by using the inductively coupled plasma atomic emission spectrometry(ICP-OES)and inductively coupled plasma mass spectrometry(ICP-MS)to investigate their spatial variability,contamination levels,potential risk and sources,and to reconstruct the historical records of trace elements in the river.Our findings are follows:(1)The spatial variability,contamination sources and health risk of trace elements as well as the river water quality were investigated.We found that Cu,Pb,Zn,Ni,Cr,Cd,Co and Mn were mainly enriched in Fengtai and Huainan districts,among which,Pb,Zn and Cd were identified as the dominant pollutants in the water body.Results of health risk assessment revealed that potential non-carcinogenic effects on human health could be posed by Co,Cd and Pb.(2)Distribution characteristics,contamination and risk levels of trace elements in the surface sediments were analyzed on the basis of sediment physicochemical property,total concentrations and geochemical fractionations of trace elements.We found that the trace element contaminations decreased in the order:As>Zn,Cd>Pb,Mn>Cu,Cr>Fe,Ni>Al,and Cd,Pb and As posed higher potential ecological risk to the river environment;the bioavailability of trace elements based on the weak acid soluble fraction of trace elements declined in the order:Mn>As>Zn>Cu>Pb>Ni>Fe>Cr,and dominant proportions of Cu,Zn,Cr,Fe and Ni were all found in the residual fraction;iron and manganese oxides are the main scavenger of Pb and As.(3)Multivariate statistical methods used for the exploration of sources of trace elements in the water and sediments from the Huaihe river(Anhui)presented that B,Ba,Mg and A1 were of natural origins,while Mn,Cu,Co,Ni,Cr and Fe were controlled by mixed anthropogenic and natural sources both in water and sediment samples,whereas Cd,As,Pb and Zn were mainly derived from anthropogenic activities,which included domestic wastewater,mining,coal combustion,vehicle exaust,agricultural activities and wastewater from the tributaries,etc.(4)The temporal distributions,enrichment characteristics and sources of trace elements in the year of 1959-2014 were investigated by using 20Pb geochronology and stable Pb isotopes(204Pb,206Pb,207Pb,208Pb).We found that the temporal trend of trace elements effectively archives the anthropogenic activities in the region and the historical economic development of China.The gradually increasing trend of trace elements from 1990s(1991-2014)and,concentration peaks in the years of 1991,1994-1998 and 2004 could have been influenced by local industrial and agricultural developments and,water pollution accidents happened in the Huaihe River watershed in the end of 20th century and the year 2004 etc.Variable Pb sources were observed over 59 years from 1955-2014 by using stable Pb isotopes.Pb was mainly from coal,coal combustion,waste incineration,and unleaded vehicle exhaust from the mid of 1970s,whereas the Great Leap Forward Movement could have influenced Pb distributions before 1970s.