Spatial Variation And Source Apportionment Of Typical Heavy Metals In Cropland Soil And River Sediment In Huanjiang County,Guangxi

In order to study the spatial variation and source apportionment of typical heavy metals in cropland soil and river sediment in Huanjiang County,which has the widely distribution of karst rocky desertification,212 soil samples and 60 sediment samples were collected from the county.Four kinds of heavy metal elements such as arsenic,mercury,lead,zinc were chose as the research object.The spatial variation of heavy metals were analyzed by Kriging interpolation of GIS.And the correlation analysis,principal component analysis and isotope were used to analyze the source apportionment and pollution characteristics of heavy metals.The conclusion is as follows.The statistical analysis of heavy metals in farmland soil showed that the content of zinc,arsenic and mercury in mulberry field soils was higher than other farmland soil.Paddy field soil showed an higher content of lead,while maize field soil showed an higher content of arsenic.The higher coefficient of variation of mercury in all utilization types showed that mercury is more affected by human activities.The speciation of zinc in farmland soil showed that residual state> oxidizable state> weak acid extract> reducible state.The reducible Pb content was highest among all Pb speciations,followed by residual state,oxidizable state,weak acid extraction.The speciation of As in farmland soil showed that residual state>reducible state> oxidizable state> weak acid extract.The speciation of Hg in farmland soil showed that residual state> weak acid extraction> reducible state> oxidation state.The contents of heavy metals such as zinc,lead,arsenic and mercury in cropland soil were significantly correlated with their respective available states(P<0.01).Lead and zinc showed significant correlation with their respective available contents(P <0.01).There was a significant negative correlation between pH and the available of mercury(P<0.05).The spatial variation of farmland soil heavy metals showed: The distribution of lead and zinc in farmland soil is zonal,mainly concentrated in Beishan lead-zinc mine,Chuanshan town and both sides of provincial highway.The homology of Pb and Zn indicated that the lead-zinc mine in Huanjiang is the main cause of Pb and Zn pollution,followed by traffic pollution.The distribution of high arsenic in the Huanjiang farmland soil was relatively scattered.The excessive soil samples are mainly concentrated in the urban and rural areas.The pollution of mercury in cropland is much serious than other heavy metals,and the pollution area is more extensive.The pollution is mainly distributed in Luoyang town,shuiyuan town and Chuanshan town which showed an outward diffraction distribution characteristic.The distribution of heavy metals in sediments showed that,The pollution of heavy metals in the DaHuanjiang sediments is more serious,and the pollution sources of four heavy metal is relatively concentrated.The main sources of heavy metal pollution are concentrated in the tributaries of the Beishan lead-zinc mine and the tributaries of the Chuan-shan town,while Zn pollution is the most serious,followed by As.The XiaoHuanjiang sediment had high content of As,which was mainly distributed in up-steam of Longyan township and Longyan township area.In the river sediments,the residual state is the main form of fourtypes of heavy metals.The speciation of As in sediment showed that residual state> reducible state> oxidizable state> weak acid extract.The speciation of Zn in sediment showed that residual state> reducible state> oxidizable state> weak acid extract.The content of residual mercury in the sediments of the river is the highest,and the oxidation state is the lowest.The content of residue lead was the highest,followed by the content of reducible lead,the least content is weak acid extraction.Analysis of heavy metals in farmland soil and water sediments showed: there were significant positive correlations between zinc,lead and arsenic in farmland(P <0.01),and they had good homo-logy.Principal component analysis showed that lead and zinc had good homology which were mainly effected by man-made mining.Agricultural pollution is a human factor for mercury pollution.As pollution was more extensive and regional,was mainly cause by nature.There were significant positive correlations(P <0.01)among the four heavy metal elements in the Dahuanjiang sediments with the correlation coefficient of mercury and lead reaching 0.914.Principal component analysis showed that the first component was resulted from zinc,mercury,and other heavy metal pollution caused by the mine.The second component was mainly due to traffic pollution of lead elements.The third component was mainly due to arsenic mineral and agricultural pollution.Lead isotope analysis showed that the lead content in the downstream sediment samples of XiaoHuanjiang was consistent with that of the parent soil,which was caused by nature.The source of lead in the sediments of the lower reaches of the DaHuanjiang is mainly due to the migration and diffusion of the tributaries of the upper reaches of the Beishan lead-zinc mine.The pollution assessment of heavy metal in farmland soils showed that mercury pollution was much serious.More than half of the samples were heavily polluted and the environmental capacity was in a state of load.Lead,zinc pollution was lighter.80 percent samples were in high environmental capacity.Arsenic pollution level is the lowest.More than80% of the samples were in a clean state.