榆树市玉米种植区黑土重金属污染状况及来源浅析

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

为明晰农田黑土重金属含量状况以及污染来源,选择黑土区连续多年种植玉米的榆树市为研究区,原位采集196个土壤样品,采用火焰-石墨炉原子吸收分光光度计对土壤中5种重金属含量进行分析测定,并采用相关分析和主成分分析法进行污染来源解析。结果表明,土壤中Cd、Cr、Cu、Zn、Pb质量分数平均值分别为(0.119±0.08)、(56.51±9.10)、(19.21±3.42)、(70.58±14.57)和(34.42±7.85)mg·kg-1;土壤中Cd、Cr、Cu、Zn、Pb含量超过相应的黑土背景值的点位百分比分别为69.9%、36.7%、26.5%、82.1%、84.2%;土壤中Cd和Zn含量超过相应的土壤环境质量二级标准的点位百分比分别为6.6%和0.5%;与成土母质相对比,富集系数为:Pb(1.56)>Cr(1.29)>Zn(1.24)>Cd(1.20)>Cu(1.16);与中国第二次土壤普查数据对比,土壤Pb、Cd、Zn平均含量分别增加48.1%、8.2%、5.1%;土壤Cr和Cu含量变化较小。相关分析表明,土壤Cu和Cr含量呈极显著正相关(r^2=0.369,P<0.01),土壤Pb和Zn含量呈极显著正相关(r^2=0.333,P<0.01),表明土壤Cu和Cr可能有相同的污染来源,Pb和Zn污染来源相似。主成分分析表明,3个主成分(PC)可解释总方差的79.13%。PC1解释总方差的29.33%,主要包括Zn和Pb,土壤中Pb和Zn污染主要来源于燃煤、大气干湿沉降物和化肥施加;PC2解释总方差的26.81%,包括Cr和Cu,土壤中Cr和Cu主要受成土母质控制;PC3解释总方差的23.00%,包括Cd,而土壤Cd富集可能来源于磷肥。总体而言,榆树市玉米种植区黑土重金属污染较轻,但Cd有超标现象,应引起重视。

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, P〈0.01）. The relationship between Pb and Zn was highly significant （r2=0.333, P〈0.01）. 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.