基于蚯蚓生物毒性的土壤Cd生态阈值研究

发布时间：2018-02-28 09:07

本文关键词： 镉中国土壤赤子爱胜蚓毒性效应生态阈值　出处：《苏州科技学院》2015年硕士论文　论文类型：学位论文

【摘要】：本文选用我国18种典型田间土壤,采用OECD颁布的标准方法研究了镉在不同类型土壤中对模式动物赤子爱胜蚓的急性毒性和慢性毒性,获取基于不同的测试终点土壤镉生态毒性阈值。探讨了土壤性质对镉的生态阈值的影响并建立了在蚯蚓生物毒性基础上基于土壤性质的镉的生态阈值预测模型。(1)急性毒性试验结果表明,土壤类型对Cd对蚯蚓的急性毒性有较大的影响,镉在鹰潭红壤中的毒性表现最强,而在贵阳黄壤中的毒性最弱,Cd在不同土壤中的引起蚯蚓半数致死毒性阈值LC的变化范围为440.7-1520.4mg/kg。将Cd的毒性阈值LC_(50)与主要的土壤理化性质(土壤pH值、阳离子交换量、有机质含量和粘粒含量)进行相关性分析,发现土壤pH值和有机质含量是导致Cd在不同类型土壤中毒性差异的主要因素,二者与LC_(50)呈显著正相关关系。分析土壤中有效态Cd含量与蚯蚓体内Cd积累量,二者显著正相关。土壤理化性质通过影响土壤有效态Cd含量,影响蚯蚓体内Cd积累量,进而对蚯蚓Cd毒性产生影响。(2)慢性毒性试验结果表明,赤子爱胜蚓的生长发育(体重变化)对Cd的响应不太敏感,大多数土壤中只有当镉浓度达到较高水平(200 mg/kg)时才对蚯蚓的体重产生比较明显的抑制效应,而反映赤子爱胜蚓生殖的测试终点(产茧量)对Cd的响应十分敏感。不同类型土壤中Cd对蚯蚓产茧量的影响差异较大,其中Cd抑制赤子爱胜蚓产茧的毒性阈值EC_(50)作用范围为66.5 263.5 mg/kg。将Cd的毒性阈值EC_(50)值与主要的土壤理化性质进行相关性分析,发现土壤pH值和有机质含量与EC_(50)呈显著正相关关系,粘粒与EC_(50)呈显著负相关关系。同时分析不同类型土壤中蚯蚓体内镉积累量变化,土壤pH越高,有机质含量越高,土壤中Cd生物有效性就越低。(3)针对影响土壤镉的生态阈值预测模型的重要环境特征—有机质(以低分子有机酸为例),模拟土壤溶液,探究其影响镉毒性/生物有效性内在机制,发现有机质与重金属镉离子形成金属有机配合物,从而降低了土壤溶液中自由态镉离子,进而降低了重金属镉的毒性,其解毒能力大小取决于有机质与金属所形成有机配合物时络合常数,络合常数越大,解毒能力越强,金属镉的毒性也就越低。本论文研究结果可为评价我国土壤镉的生态风险和建立土壤Cd生态阈值提供依据。
[Abstract]:In this paper, the acute and chronic toxicity of cadmium to model animal Aicheng vermis in different types of soils was studied by using the standard method issued by OECD in 18 typical field soils in China. The ecological toxicity threshold of cadmium in soil based on different testing endpoints was obtained. The effects of soil properties on ecological threshold of cadmium were discussed and a prediction model of ecological threshold of cadmium based on soil properties was established based on the biological toxicity of earthworm. The results of acute toxicity test showed that. Soil type had a great effect on the acute toxicity of CD to earthworms, and cadmium had the strongest toxicity in Yingtan red soil. The toxicity of CD in yellow soil of Guiyang was the weakest, and the LC50 of LC50 caused by CD in different soils ranged from 440.7-1520.4 mg / kg. The toxicity threshold of CD LCSP 50 was compared with the main soil physical and chemical properties (soil pH value, cation exchange capacity, and so on). The correlation analysis of organic matter content and clay content showed that pH value and organic matter content were the main factors that led to the difference of CD toxicity in different types of soils. The content of available CD in soil and the accumulation of CD in earthworm were positively correlated. The physical and chemical properties of soil affected the accumulation of CD in earthworm by affecting the content of available CD in soil. The results of chronic toxicity test showed that the growth and development (body weight change) of Aisheng earthworm was not sensitive to CD. In most soils, only when cadmium concentration reached a high level of 200 mg / kg did the weight of earthworms be inhibited significantly. But the test end point (cocoon yield) which reflects the reproduction of Aisheng vermis is very sensitive to the response of CD. The effect of CD on the cocoon production of earthworm in different types of soil is quite different. The toxicity threshold of CD on cocoon production of Aisheng earthworm was 66.5 ~ 263.5 mg / kg 路kg ~ (-1). The correlation between the toxicity threshold of CD and the physical and chemical properties of soil was analyzed. It was found that soil pH value and organic matter content were positively correlated with ECS _ (50). There was a significant negative correlation between clay and ECS 50. At the same time, the change of cadmium accumulation in earthworm in different types of soil was analyzed. The higher the soil pH, the higher the content of organic matter. The lower the CD bioavailability in soil is, the lower the CD bioavailability is.) aiming at the important environmental characteristics of the ecological threshold prediction model affecting soil cadmium-organic matter (taking low molecular organic acid as an example, simulating soil solution to explore the intrinsic mechanism of its effect on cadmium toxicity / bioavailability, It is found that organic matter forms organometallic complexes with heavy metal cadmium ions, thus reducing the free state cadmium ions in soil solution and thus reducing the toxicity of heavy metal cadmium. The degree of detoxification ability depends on the complexation constant of organic complex formed by organic matter and metal. The larger the complexation constant is, the stronger the detoxification ability is. The toxicity of cadmium is also lower. The results of this paper can be used to evaluate the ecological risk of soil cadmium and to establish the ecological threshold of soil CD in China.
【学位授予单位】：苏州科技学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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