土壤镉污染与稻米镉富集关联性研究

发布时间：2018-12-26 12:55

【摘要】：土壤是人类赖以生存的基础,Cd是一种剧毒的重金属元素,其通过食物链途径可以累积于人体内。稻米是人类主要的粮食作物,人体摄入Cd主要通过稻米。因此通过吸收系数研究土壤镉污染与稻米镉富集的关联性,并以此为依据筛选稻米Cd风险种植区,可以避免镉米对人体产生危害。为满足数据保密性需要和提高使用便捷性,建立了研究用数据库。以市、县、镇不同尺度探讨了区域吸收系数的差异性,并研究了造成差异性的原因,探讨了四种有效态方法对稻米Cd的预测能力,并基于上述研究结果筛选了稻米镉风险种植区。主要研究结论如下:(1)对不同区域吸收系数差异性进行了描述性统计,结果表明:市、县、镇都为中高度变异。不同区域吸收系数差异性的方差分析表明,研究所选用的不同市、不同县吸收系数存在普遍的显著差异,而在同一县的不同镇之间几乎不存在显著性差异,因此选取县为尺度来确定区域吸收系数。(2)吸收系数差异性的最主要影响因素为pH值,整体上呈现随着pH值升高吸收系数下降的趋势。当细化pH间隔到0.1时,吸收系数在4.8~6.0区间几乎没变化,但当pH为6.0~6.3时出现吸收系数下降突变点。当土壤pH为小于6.0时,吸收系数最高,且变化平缓;当土壤pH大于下降突变点时,吸收系数急剧下降;当土壤pH大于7.0时吸收系数降到最低。(3)土壤有机质、土壤质地、土壤类型也会对吸收系数产生影响,但影响性远小于土壤pH值。不同土壤污染程度下吸收系数随污染程度升高而降低。土壤Zn/Cd也会影响吸收系数,吸收系数较大的地区土壤Zn/Cd比较小,且土壤Zn/Cd比大于稻米Zn/Cd比,可能原因是Zn抑制稻米对Cd的吸收和Cd在稻米中的迁移转化。(4)有效态测定DGT方法、CaCl2方法都可以作为预测稻米Cd的有效方法。当土壤Cd有效率很低时,稻米Cd的吸收系数显著低于其它有效率时的吸收系数。当有效率高于某一值后,不同有效率下稻米Cd的吸收系数无显著差异。当pH值降低时,土壤Cd有效率有升高的趋势;土壤pH大于7.0时,土壤Cd有效率降至最低。(5)本研究对湖南、广东、浙江进行了稻米Cd风险种植区筛选。结果表明,湖南地区稻米种植区Cd风险程度高于广东,广东又高于浙江。浙江的稻米种植区Cd风险几乎都为安全级别。
[Abstract]:Soil is the basis of human survival. Cd is a highly toxic heavy metal element, which can be accumulated in human body through the food chain. Rice is the main food crop for human beings. Human body ingest Cd mainly through rice. Therefore, by studying the correlation between cadmium pollution in soil and cadmium enrichment in rice by absorption coefficient, and selecting rice Cd risk planting area based on this, the harm of cadmium rice to human body can be avoided. In order to meet the need of data confidentiality and improve the convenience of use, a research database was established. In this paper, the difference of regional absorption coefficient was discussed at different scales of city, county and town, and the cause of the difference was studied. The prediction ability of four effective state methods for rice Cd was discussed. Based on the above results, rice cadmium risk growing areas were selected. The main conclusions are as follows: (1) the difference of absorption coefficient in different regions is described. The results show that: city, county and town are medium height variation. The variance analysis of the difference of absorption coefficient in different regions shows that there are significant differences in absorption coefficient between different cities and different counties, but there is almost no significant difference among different towns in the same county. Therefore, the county is chosen as the scale to determine the regional absorption coefficient. (2) the main influencing factor of the difference of absorption coefficient is the pH value, and the overall absorption coefficient decreases with the increase of the pH value. When the pH interval is refined to 0.1, the absorption coefficient almost does not change in the range of 4.86.0.However, when the pH is between 6.0 and 6.3, the abrupt point of absorption coefficient decreases. When the soil pH is less than 6.0, the absorption coefficient is the highest and the change is gentle, and when the soil pH is larger than the decreasing mutation point, the absorption coefficient decreases sharply. (3) soil organic matter, soil texture and soil type also affect the absorption coefficient, but the influence is much less than the soil pH value. The absorption coefficient decreased with the increase of soil pollution. Soil Zn/Cd also affected the absorption coefficient. The soil Zn/Cd ratio was smaller and the soil Zn/Cd ratio was higher than the rice Zn/Cd ratio in the areas with higher absorption coefficient. The possible reason is that Zn inhibits the absorption of Cd in rice and the migration and transformation of Cd in rice. (4) DGT method and CaCl2 method can be used to predict Cd in rice. When the soil Cd efficiency was very low, the absorption coefficient of rice Cd was significantly lower than that of other efficient rice. When the effective rate was higher than a certain value, there was no significant difference in the absorption coefficient of rice Cd under different effective rates. When pH value decreased, soil Cd efficiency increased, and soil Cd efficiency decreased to the lowest when soil pH was greater than 7.0. (5) in Hunan, Guangdong and Zhejiang provinces, rice Cd risk planting areas were screened. The results showed that the Cd risk level in rice growing areas in Hunan was higher than that in Guangdong and Zhejiang. The Cd risk in rice growing areas in Zhejiang Province is almost always a safety level.
【学位授予单位】：中国农业科学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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