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Survey of Heavy Metal Pollution and Source Identification of Black Soil in Zea mays L. Cultivated Region of Yushu City, China

YU Rui;WANG Yang;WANG Chenxu;WANG Qicun;CUI Zhengwu;Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences;  
This study aims to investigate the content of heavy metal and metal sources in agricultural black soils. We investigated heavy metal concentrations in soil of Yushu city, China, located in black soil region. A total of 196 soil samples were collected from Yushu. Heavy metal content was analyzed by flame atomic absorption spectrophotometer or graphite furnace atomizer. We used correlation analysis and principal component analysis to identify metal sources. The mean contents of Cd, Cr, Cu, Zn and Pb in soil were(0.119±0.08),(56.51±9.10),(19.21±3.42),(70.58±14.57) and(34.42±7.85) mg·kg~(-1), respectively. The percentages of Cd, Cr, Cu, Zn and Pb contents exceeding corresponding black soil background values were 69.9%, 36.7%, 26.5%, 82.1% and 84.2%. The percentages of Cd and Zn contents exceeding corresponding grade Ⅱ of environmental quality standard for soil in China were 6.6% and 0.5%, respectively. Compared to parent material, accumulation factors was as follows: Pb(1.56)Cr(1.29)Zn(1.24)Cd(1.20)Cu(1.16). Compared to data obtained by the second national soil survey, the mean content of Pb, Cd and Zn increased by 48.1%, 8.2% and 5.1%, respectively and Cr and Cu content did not changed. The relationship between soil Cu and Cr was highly significant(r2=0.369, P0.01). The relationship between Pb and Zn was highly significant(r2=0.333, P0.01). The correlation analysis results showed that Cu and Cr in soil may be had same pollution source, so did Pb and Zn. Based on results of initial eigenvalues, three principal components(PC) were considered, which account for over 79.13% of total variance. According to rotated component matrix, Zn and Pb were closely associated with PC1, which explained 29.33% of total variance. The coal burning, household heating, atmospheric deposition and over-application of chemical fertilizers were acknowledged as the main source of these elements pollution. PC2 can explain 26.81% of total variance and included Cr and Cu. PC2 can be considered to be controlled by parent material. The Cr and Cu in soil were still controlled by parent material. PC3 can explain 23.00% of total variance and included Cd. The accumulation of Cd was associated with phosphate fertilizer. In a word, heavy metal pollution of black soil was not serious. We should pay attention to Cd content, because Cd content in some soils was exceed standard.
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