Distribution Characteristics And Reasons Of Anomalous Elements In Soil From The Middle And Lower Reaches Of The Second Songhua River

The middle and lower reaches of the Second Songhua River is the mainly rice and corn producing areas in Jilin Province. However, agricultural geological survey revealed some elements of high-content in the soil of the place. This paper systematically studied the characteristics and formation mechanism of the soil anomalous elements, providing a scientific basis for environmental protection and management of the soil and green-agriculture development and so on.The Second Songhua River originates from the main peak of Mt Changbai Mountain's Tianchi and has two branches, Toudao River and Erdao River. At the main stream in the upper reaches of the Songhua River exists the convergence of Huifa River and Jiao River. The rock types of the region where Toudao River and Erdao River flow through are mainly partial alkali basalt, olivine basalt, a small amount of alkali trachybasalt and tuff breccia etc. The rock types of the region where Huifa River and Jiao River flow through are mainly granites belonging to Hercynian and Yanshanian periods.The content of SiO2, Ba, Al2O3, K2O, Ti, Ga, Sr, V of surface soil in the study area ranges little , the content of I, Corg, S, Cd, CaO, Nb, Mo, Hg and Cl ranges widely, and the content of Cu, Mn, U, Bi, Sc, Zr, As, La, Ce, Be ranges between the two. The content of Br, Cd, Hg, I, N, S, Se and Corg in the surface soil is greatly higher than that of deep soil. Along middle and lower reaches of the Second Songhua River, the content of Ce, La, Y, Nb, U, Th, Zr, Cd, Hg and Zn has obviously zonal anomaly.The statistical analysis indicated that the contents of U and Th in the research area conform to the normal distribution, and others conform to the lognormal distribution. The background values of Nb, Th, Cd, Ce and Y in this research area are slightly higher than that in Jilin Province, but the content of Hg is correspondence with the background value in Jilin Province, the background values of Zn, Zr, La and U in this research area are slightly lower than that in Jilin Province. Comparing with the background value of national soil, the background values of Zr, Cd and Y are obviously higher, the background values of Ce, Nb, La, Zn and Hg are slightly higher, the content of Th is correspondence with the national background value, but the content of U is slightly lower than the national background value of soil.In the anomalous zone, the content of Ce, Y, La, Nb, Zr, U and Th drops obviously from upstream to downstream, and the content of Cd, Hg and Zn is relatively higher in the upstream and downstream; in the shore direction, all the elements have different concentration nearby the river; In the vertical direction, the content of Ce, Y, La, Nb, Zr, U and Th change slightly, but Cd, Hg and Zn concentrate in the surface layer of soil.Study on elements zone indicates that the elements with HFS concentrate relatively in upstream of the anomalous zone, but Hg, Cd and Zn concentrate relatively in the downstream. The connection analysis of the elements indicates that elements have obvious relevance with each other, and the element association of soil in anomalous zone has close contacting with the Sediment in upstream of the second Songhua River.The content differences of U, Th and Ta in clay between the main current and the branch of the Songhua River are relatively small, but content of other elements changes obviously, the content order of La, Ce, Y, Nb, Ta, Hf and Zr is: Erdao Songhua River>Toudao Songhua River>main current of Songhua River>unusual area>Huifa River and Jiaohe River. The values of La/Ce, La/Y, Nb/Ta and Zr/Hf of clay in Toudao Songhua River, Erdao Songhua River and the main current of Songhua River are close, which are higher than that in Huifa River, Jiaohe River and the soil in anomalous zone.Graphics of Zr-Zr/Hf, Nb-Nb/Ta and La/Yb-∑REE shows that Zr and Hf are mainly from rock weathering product of Toudao River and Erdao River, locating at the upper reaches of Songhua Lake, and particularly have close relationship with Changbai Mountain's alkali basalt weathering product which have a high content of rare element, rare earth element and radioactive element.Content of Hg in water from the branch of Songhua River had a little difference and content of Cd and Zn in water from the branch in water from the branch had a great diversity. Content of Cd was relatively high in Erdao Songhua River and Huifa River and relatively low in Toudao River, Jiao River and main curent of Songhua River was relatively low. Content of Hg in water from the branch of upstream Songhua Lake had a little difference. In the water from downstream, content of Cd and Zn increases significantly.Content of Cd, Hg and Zn in suspended matter from Toudao Songhua River significantly exceeds Erdao Songhua River. In main curent of Songhua River, Content of Cd and Zn in suspended matter increases significantly and content of Hg decreases slightly. Content of Cd, Hg and Zn in suspended matter in Huifa River and Jiao River was relatively low. Content of Cd, Hg and Zn in suspended matter from Songhua Lake decreases significantly, but Content of Hg increases。Content of Cd, Hg and Zn in suspended matter increases significantly in downstream of Jilin City.he comprehensive research results indicates that in anomalous zone,Ce,Y,La,Nb,Zr,U and Th mainly originates from supracrustal rocks in the Upper Reaches and Cd,Hg and Zn originated from natural source and human activities source.