海南农田土壤重金属人为输入识别及分布

发布时间：2018-05-15 22:21

本文选题：海南农田 + 重金属　；参考：《海南大学》2015年硕士论文

【摘要】：土壤重金属元素的过量累积会破坏土壤系统中原有生态平衡,引起土壤成分、结构和功能变化,导致农产品的产量和品质降低,并且可作为二次污染源对大气和水体造成毒害。海南农田总体土壤质量偏低,且复种指数高,故化肥和农药用量逐年增加。这不仅导致海南耕地地力降低,还存在农用地重金属污染风险,对海南农产品的质量安全和人类健康构成极大威胁。故本研究以海南岛为研究区,采用以土壤采样为主的调查方法,分析研究区土壤中砷、铅、铬和镉的含量分布特征,对不同类型母质发育土壤分别估算其元素背景含量,并以此为基础识别超背景分布特征,并对其进行生态风险评价。主要结论如下： 1.海南土壤重金属砷、铅、铬和镉含量总体水平较低,其平均含量均低于全国平均水平和我国土壤环境质量标准规定的一级标准限值,仅个别点位的土壤存在超标现象。 2.四种重金属元素的空间分布格局存在差异,虽然不同类型母质发育土壤的重金属含量存着差异,但土壤砷、铅和镉的空间分布特征未表现出母质特征。研究区内火山堆积物和基性火成岩发育土壤的铬含量显著高于其余类型母质,土壤铬在空间分布上与母质分布关系紧密。 3.不同类型母质发育土壤的各重金属元素背景值存在差异,酸性变质岩母质发育的土壤砷、铅背景值最高,火山堆积物和碎屑沉积岩风化物母质发育土壤的镉背景值最高,北部地区的火山堆积物和基性火成岩母质发育土壤的铬背景含量高于其余类型母质。 4.土壤砷、铅和镉的高强度超背景分布主要是区域成矿作用、矿山开采和城市周围污染物排放引起的污染扩散所致；成片分布的低强度超背景土壤与农业生产上的化学物质输入有关。土壤铬含量的超背景值强度高的土壤主要为火山堆积物和基性火成岩母质,其超背景强度较高与铬在母质中分布不均有关。 5.海南耕地土壤的砷、铅、铬和镉污染水平均相对较低,各元素地累积指数高于0的分布区间主要为0-1。不同的母质中,海相沉积物母质发育的土壤重金属地累积指数相对较高。 6.土壤中的砷、镉主要以残渣态形式存在,可迁移态砷、镉主要与风化成土过程有关,人为活动对生态风险程度高的形态,即水溶态和离子交换态砷、镉,含量的影响不容忽视。
[Abstract]:Excessive accumulation of heavy metal elements in soil will destroy the original ecological balance in soil system, cause changes in soil composition, structure and function, reduce the yield and quality of agricultural products, and can be used as a secondary source of pollution to the atmosphere and water. The soil quality of Hainan farmland is on the low side and the index of multiple cropping is high, so the amount of fertilizer and pesticide is increasing year by year. This not only leads to the reduction of cultivated land fertility in Hainan, but also to the risk of heavy metal pollution in agricultural land, which poses a great threat to the quality, safety and human health of agricultural products in Hainan. Therefore, in this study, Hainan Island was used as the study area, and the distribution characteristics of arsenic, lead, chromium and cadmium in soil were analyzed by using the method of soil sampling, and the background contents of elements were estimated for different types of parent material developed soils. And based on the above-background distribution characteristics, ecological risk assessment is carried out. The main conclusions are as follows: 1. The contents of arsenic, lead, chromium and cadmium in Hainan soil are lower than the national average level and the first class standard limit of soil environmental quality standard in China. 2. The spatial distribution patterns of the four heavy metals were different. Although the contents of heavy metals in different types of parent materials were different, the spatial distribution of arsenic, lead and cadmium did not show the characteristics of parent material. The contents of chromium in volcanic deposits and basic igneous rock developed soils were significantly higher than those in other types of parent material, and the spatial distribution of chromium in soil was closely related to the distribution of parent material. 3. The background values of heavy metal elements in different types of parent materials were different. The background values of arsenic and lead were the highest in the soils of acid metamorphic rocks, and the background values of cadmium were the highest in the soils of volcanic deposits and clastic sedimentary rocks. The background content of chromium in volcanic deposits and basic igneous parent materials in northern China is higher than that in other types of parent materials. 4. The high intensity background distribution of arsenic, lead and cadmium in soil is mainly caused by regional mineralization, mine mining and pollution diffusion caused by pollutant emission around the city. The distribution of low intensity background soils is related to the input of chemicals in agricultural production. The soils with high super-background value of Cr content are mainly volcanic deposits and basic igneous rock parent materials, and the higher background strength is related to the uneven distribution of Cr in the parent material. 5. The pollution levels of arsenic, lead, chromium and cadmium in cultivated soil of Hainan were relatively low, and the distribution range of accumulation index of each element above 0 was mainly 0-1. Among different parent materials, the accumulation index of heavy metals in the soils of marine sediments was relatively high. 6. Arsenic and cadmium in soil mainly exist in the form of residual form. The transportable arsenic and cadmium are mainly related to the weathering process. The effects of human activities on the high ecological risk forms, I. e., water soluble and ion exchange arsenic, cadmium, can not be ignored.
【学位授予单位】：海南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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