渤海湾西部表土中HCHs与DDTs的残留特征

分析采自渤海湾西部地区302个表土样品中的HCHs和DDTs含量.结果表明,区域表土中HCHs、DDTs含量的算术均值±标准偏差分别为(3.88±25.92)ng·g-1和(63.60±255.83)ng·g-1;几何均值±标准偏差分别为(0.44±3.97)ng·g-1和(8.68±5.51)ng·g-1.两类污染物的原始数据大多呈右偏态分布.HCHs的对数浓度与角变换的土壤TOC含量存在较为显著的相关关系;而对于DDTs关系并不明显.不同土地利用条件下HCHs和DDTs的残留水平存在明显差异,其中,菜地、林地和荒地表现出较高的HCHs残留,而菜地、林地、耕地和棉田则具有较高的DDTs残留.渤海湾西部地区表土中若干地区存在HCHs和DDTs的新输入.根据国家现行的土壤质量标准,DDTs污染水平达到三级和三级以上的样点占总数的2.6%,二级水平的样点比例为11.9%;而HCHs污染水平达到二级的仅占总数的2%.据此,表土HCHs潜在生态风险较高的样点主要分布于河北省石家庄市、北京市和天津市;表土DDTs潜在生态风险较高的样点则集中在河北省石家庄市和邯郸市、山东省济南市、北京市和天津市.

Residual characteristics of HCHs and DDTs in surface soils from the western zone of Bohai Bay

Three hundreds and two surface soil samples were collected from the western watershed of Bohai Bay and measured for residual HCHs and DDTs.The analytical results indicated that, the arithmetic average concentrations and standard deviations of HCHs and DDTs were (3.88±25.92) ng·g-1 and (63.60±255.83) ng·g-1, respectively; and the geometric mean values and standard deviations of HCHs and DDTs were (0.44±3.97) ng·g-1 and 8.68(5.51 ng·g-1, respectively. The distribution of the raw data showed right-skew characteristics. The logarithm transformed concentrations of HCHs had significant correlation with angular transformed soil TOC contents, while this correlation was not found for the case of DDTs. There were apparent differences between different types of land use, and vegetable plot, woodland and barren had relatively higher concentrations of HCHs, while elevated residues of DDTs occurred at vegetable plot, woodland, cultivated land and cotton field. In some areas, new inputs of HCHs and DDTs may exist. Based on the current national soil quality standards, the percentage of the number of the sites with DDTs concentrations over the III or higher quality grades was 2.6%, and 11.9% for the sites with DDT residual levels in the II grade; in the case of HCHs, the proportion of the sites with concentrations above the II grade was only 2%. Accordingly, the resulted sites with higher potential ecological risk of HCHs were mainly located in Shijiazhuang of Hebei Province, Beijing and Tianjin, while the corresponding sites with higher potential ecological risk of DDTs were mostly situated in Shijianzhuang and Handan of Hebei Province, Jinan of Shandong Provinve, Beijing and Tianjin.