| The Fenhe River watershed is a region where the industry and agriculture are developed. The Fenhe River watersheds plays a key role in economic development in Shanxi Province. In recent years, the annual precipitation decreased and varied seasonally, the ecological functions of Fenhe River have degraded greatly.As more and more direct and indirect pollutants from commercial, industrial, and recreational uses of the watershed discharge into Fenhe river, Environmental pollution and damage accidents which brought about has gradually become a prominent problem, and are danger to human health. Heavy metals pollution is increasingly concerned because of their no-degradation and characteristics that they can be rich and the concentrations may be increased as toxins are passed up the food chain.This paper studies the following aspects:The water geochemical survey including water, suspended matter and bottom mud and the geochemical fluvial sediments survey are carried out. The eco-geochemical evaluation about heavy metals Hg, Cd, Pb, As, Cr, Cu, Ni and Zn are executed. The abundance of isotopes 210Pb of floodplain sediments was tentatively measured. The deposition rate of sediments and sediment flux of heavy metals in Fenhe River are estimated. The main period of pollution are deduced. The chemical speciation of high-heavy metals samples is analyzed, and the ecological danger, the sources and migration of heavy metals are discussed.The following results and knowledge were obtained:(1) Heavy metal content is the lowest in suspended matter, the second high in water and the highest in bottom mud in Fenhe River. As a whole, heavy metal content tends to increase from Taiyuan to Hejing.The content of heavy metals Hg, Cd, Pb, As, Cr, Cu, Ni and Zn in filtered water is lower in Huanghe River than in Fenhe. And higher in Linyi than in Yumenkou. Heavy metal concentrations of the suspended matter in Fenhe River during flood periods are higher than during drought periods. It shows that in monsoon surface running water washed pollution source clearly. Compared with Huanghe, the heavy metals pollution in botton mud is more serious in Fenhe river. All in all, the water of Fenhe river give obvious pollution to Huanghe River.(2)The pollutants in Fenhe River stay mainly in the sediments of Taiyuan basin and Linfen basin. The maximum concentrations of heavy metals in sediments focus approximately on the depth of 12?66 centimeters in Taiyuan basin, and on the depth of 88?100 centimeters in Linfen basin. The maximum concentrations of sediment flux of heavy metals occur after 1980 which is the peak-period of anthropogenic input of heavy metals. Concentrations of heavy metals have a positive correlation with sediment flux, which is different from the rivers in the south. Taiyuan basin and Linfen basin are the reservoirs where the pollutants are assembled and also new pollution source of Huanghe River.(3) The pollution degree of heavy metals in water and sediments was appraised fully and impersonality. According to comprehensive evaluation, the water in Fenhe river has been poluted. Hg, Cr and Cd pollution in Hejin section belong to V category according to GB3838-2002. The content of metal Hg in six sections belong to V category. The main pollutants in the river are Hg and Cd. Concentrations of Pb, As, Zn, Cu and Ni in water are lower, and the pollutions are slighter. The main pollutants in the fluvial sediments are also Hg and Cd. The pollutions of other heavy metals in the fluvial sediments are also slighter. The pollution levels of heavy metals in the sediments of six sedimentary columns were in the following orders:MHH1420FU>MHH1419> MHH1418> MHH1421> MHH1414> MHH1417. All sedimentary columns were seriously polluted by heavy metals except MHH1418, that is to say, the service functions of ecological system were seriously degraded, the ecological environment was destroyed, and more ecological problem and disaster appeared.(4)The speciation analysis of the elements Hg, Cd, Pb and Zn was carried out among the sediment in different stations. The content of heavy metals unsteady states reflected different influence of anthropogenic factors among different stations. Among Hg, Cd, Pb and Zn, the environment risk of mercury is the lowest, while the environment risk of Cd is the highest. Pb and Zn are potentially hazardous. When the conditions and environment are changed, Cd in the sediments easily become active and is released into water, which will become a new pollution source. Therefore more attentions should be paid.(5)The sources of heavy metals are identified by being compared with concentrations of heavy metals in the rocks of the Fenhe River watersheds, by carrying out correlation analysis and factor analysis, and by being compared with the development status of industry in the Fenhe River watershed. The natural origin of mercury is from sedimentary rocks such as stratum P1x, C2, C3 and O2f. Concentrations of mercury are very low in metamorphic rocks and magmatic rocks. Concentrations of cadmium are high mainly in stratum T1 and C3. The anthropogenic pollutions of mercury and cadmium are chiefly affected by industrial coal combustion and coal mining. The other heavy metals, having slighter or medium pollution and being rich in sediments in different degrees, come from the natural weathering of the rocks of the Fenhe River watersheds, and are influenced by the rapid growth of its population, industry and commerce. In addition, we presume that the accumulation of these heavy metals is perhaps related with geological structure of Fenhe Graben, and the conclusion needs further research. |
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