宜宾市江安县稻田土壤及稻米重金属现状评价

发布时间：2018-10-22 12:17

【摘要】：近年来,我国受重金属污染的耕地面积持续增长,由土壤污染导致的食品安全事件频频发生。稻田作为我国第一大粮食作物的耕种地,其重金属污染带来的健康风险更为突出。重金属不仅影响水稻产量和品质及整个农田生态系统,还可通过食物链危及动物和人类的健康。当下,稻田重金属污染问题日趋凸显,其污染状况调查和防控也愈加紧迫。本文以江安县境内土壤—水稻系统中常见且与人类密切相关的8种重金属元素(砷、镉、铬、铜、汞、镍、铅、锌)为研究对象,对不同方位、不同类型的表层土壤及对应区稻米中重金属元素进行了检测,并参照相关背景值和国家标准评价土壤环境质量、稻米安全质量及重金属污染程度;同时,讨论了土壤和稻米中重金属全量间的相关性以及土壤pH、有机质对稻米吸收土壤重金属能力的影响;并以此为依据,提出了针对性的重金属污染防控建议。论文研究结果可为江安县土壤-水稻系统中重金属污染的防控提供科学依据。主要研究结果如下:1.以国家土壤二级标准值为参照,该地区镉污染最严重,受污染比例高达77.1%,根据内梅罗综合污染指数评价结果,约三分之一样点存在生态安全隐患。以背景值为参照,江安县重金属潜在生态风险指数较低,为134.59,处无风险状态。单项风险系数大小为:汞镉砷铅铜镍铬锌,潜在生态风险指数在空间上分布规律为:北部中部南部,交通干道区农业耕种区工业集中区自然保护区,平地河漫滩丘陵。2.稻米重金属中,该地区锌含量最高,汞含量最低。以食品安全国家标准为参照,除镉、铬个别样点超标外,其余均达标。根据内梅罗综合污染指数评价结果,受污染的稻米比例为8.6%。以背景值为参照,稻米重金属污染严重,镍污染指数为23.09,铅无污染,其他6元素污染指数介于二者之间。空间上的分布规律为,工业集中区所在的中部污染最重,自然保护区所在的南部污染次之。3.该地区土壤—水稻系统的重金属相关性很小,其中砷相关系数最高,为0.202。水稻对土壤中重金属的富集系数介于0.002～0.231之间,顺序为:锌汞镍镉铜砷铬铅。多元回归结果表明,富集系数与土壤pH呈负相关、与土壤有机质总体上呈正相关关系。稻米吸收土壤中重金属的能力受土壤pH的影响程度具体顺序为:镍砷锌镉汞铜铬铅。
[Abstract]:In recent years, the area of cultivated land polluted by heavy metals has been increasing, and food safety events caused by soil pollution have occurred frequently. As the largest cultivated land of grain crops in China, the heavy metal pollution brings more serious health risks. Heavy metals not only affect the yield and quality of rice and the whole farmland ecosystem, but also endanger the health of animals and human beings through the food chain. At present, the problem of heavy metal pollution in paddy field is becoming more and more serious, and its pollution investigation and prevention and control become more and more urgent. In this paper, eight heavy metal elements (arsenic, cadmium, chromium, copper, mercury, nickel, lead, zinc) which are common in the soil-rice system in Jiangan County are studied. Heavy metal elements in different types of topsoil and rice were detected, and soil environmental quality, rice safety quality and heavy metal pollution were evaluated according to relevant background values and national standards. The correlation between the total amount of heavy metals in soil and rice and the effect of soil pH, organic matter on the ability of rice to absorb heavy metals were discussed, and based on this, some suggestions for prevention and control of heavy metal pollution were put forward. The results can provide scientific basis for the prevention and control of heavy metal pollution in the soil-rice system in Jiangan County. The main results are as follows: 1. According to the national soil secondary standard value, cadmium pollution is the most serious in this area, and the polluted ratio is as high as 77.1. According to the evaluation results of Nemero comprehensive pollution index, there is a hidden danger of ecological security at about one third of the same point. Taking the background value as reference, the potential ecological risk index of heavy metals in Jiangan County was low, 134.59, and it was in a risk-free state. The single risk coefficient is mercury, cadmium, arsenic, lead, copper, nickel, chromium and zinc. The spatial distribution of potential ecological risk index is as follows: the central and southern part of north, the nature reserve of industrial concentration area in agricultural cultivation area of traffic trunk area, and the flat floodplain hilly area. 2. Among the heavy metals in rice, zinc content was the highest and mercury content was the lowest in this area. With food safety national standards as reference, except cadmium and chromium other points exceed the standard, the rest are up to standard. According to the comprehensive pollution index of Nemero, the proportion of contaminated rice was 8.6%. Compared with the background value, the heavy metal pollution of rice was serious, the pollution index of nickel was 23.09, the pollution index of the other six elements was between them. The spatial distribution law is that the pollution in the middle of the industrial concentration area is the most serious, followed by the southern pollution in the nature reserve. 3. 3. The correlation of heavy metals in the soil-rice system is very small, and the correlation coefficient of arsenic is the highest (0.202). The enrichment coefficient of heavy metals in soil by rice was between 0.002 and 0.231, in the order of zinc, mercury, nickel, cadmium, copper, arsenic, chromium and lead. The results of multiple regression showed that the enrichment coefficient was negatively correlated with soil pH and positively correlated with soil organic matter in general. The order of the ability of rice to absorb heavy metals in soil affected by soil pH was: nickel, arsenic, zinc, cadmium, mercury, copper, chromium, lead.
【学位授予单位】：南京农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X825;S511

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