山东省威海市区域地质背景下土壤Cd的地球化学特征

为获取威海市区域地质背景下土壤重金属元素Cd的地球化学特征,以区域表层和深层土壤Cd为研究对象进行讨论。统计分析得出Cd区域土壤背景值为0.090×10-6,基准值为0.056×10-6。区域Cd的土壤环境质量较好,全区仅3.42%的表层土壤、1.17%的深层土壤超出国家土壤质量一级标准限值,其中仅1.67%的表层土壤出现污染,超出国家土壤二级标准。研究区土壤Cd的物源主要表现为自然源和人为源两大类。自然源主导区占54.68%,自然属性特征明显,表层和深层土壤Cd的相关性较好,且Cd与其他重金属元素间具有较好的地球化学组合特征;表层土壤Cd的分布主要受母质影响,在丘陵区土壤Cd含量受中生代中酸性侵入岩的分布影响较大,而平原区受第四系沉积物影响较大,其中陆源为主的平原区土壤Cd相对含量较高,与海水有关的平原区Cd含量普遍偏低。人为源主导区占45.32%,自然属性较差,受人为源影响较大,与工矿点等人为活动密集区分布较吻合。

Geochemical characteristics of Cd in soils based on regional geological background in Shandong Province

The regional data of Cd in surface and deep layer of soils in Weihai were collected to investigate the geochemical characteristics of heavy metal Cd based on regional geological background. The results suggest that the background and baseline values are 0.090×10^-6and 0.056×10^-6, respectively. The regional soil environment quality of Cd element is generally good, only 3.42% of the region＇ s surface soils and 1.17% of the deep soils exceeds the I grade of National Environmental Quality Standards in Soils of China, and on- ly 1.67% of the surface soils exceeds the 11 grade of National Environmental Quality Standards in Soils of China due to contamination. The input of Cd in soils of the study area could be mainly classified into natural and anthropogenic sources. The natural sources domina- ted area of Cd accounts for 54.68%, in which a good correlation of Cd between the surface and deep soils and geochemical element combination characteristics of Cd with other heavy metals in surface soils could be detected; the distribution of Cd content in surface soils of natural area is mainly affected by the parent materials, the Mesozoic intermediate-acidic intrusive rocks control the distribution of Cd in soils of hilly areas, and the Quaternary sediments control Cd of soils in plain areas. In addition, the terrigenous sedlment-dom- inated plains＂ surface soils have relatively higher level of Cd content, whereas the plain related to seawater generally has a lower Cd content. However, the anthropogenic sources-dominated area accounts for 45.32%, in which the natural properties of Cd in soils have been destroyed because of artificial interference, and the increasing of Cd content in surface soils could be attributed to human activities such as factories and mining activity.