Effects of Biogas Fertilizer/Passivator on Heavy Metal Cd/Cr in Soil and Spinach

郭敬阳

李轶;张大雷

硕士

沈阳农业大学

沼肥;;菠菜;;钝化剂;;重金属铬/镉;;红外光谱

土壤重金属污染已威胁到人类的健康和生命安全,而重金属的危害与其赋存形态密切相关。沼肥作为重要的有机肥,如何科学施用对提高农产品质量和产量、减少重金属污染至关重要。本文以菠菜为种植作物,通过盆栽试验,研究施加沼肥及不同种类的钝化剂(沸石、赤泥、钙镁磷肥)对土壤重金属Cd、Cr的影响。利用BCR连续提取法分析重金属形态,对重金属各形态含量和分配率的变化、钝化效果及土壤污染指数进行分析;通过检测菠菜中根、茎、叶中重金属含量,计算了生物富集系数,分析了土壤可交换态和有效态含量与菠菜中重金属含量的相关性;分别用蒸馏水、KCl、Na_4P_2O_7、Na OH、HNO_3消煮分级提取法对土壤中重金属形态变化与腐殖质的相互作用进行分析,并采用傅立叶变换红外光谱及二维相关光谱对试验前后土壤的光谱特性进行分析,阐明土壤中重金属Cd、Cr与有机质的结合机制,为降低土壤中重金属Cd、Cr生物有效性、为沼渣沼液的合理利用及土壤重金属污染治理提供一定的科学数据。主要结论如下:(1)土壤中施加沼肥或沼肥+钝化剂,重金属Cd、Cr的可交换态含量及其分配率均较试验前的降低,而残渣态含量及其分配率均增加,Cd、Cr可交换态和有效态钝化效果均提高,污染指数均降低;方差分析结果表明,施加沼肥或沼肥+钝化剂对重金属Cd、Cr可交换态和残渣态的含量、分配率及其可交换态及有效态钝化效果均有显著影响(P<0.05)。(2)施用沼肥或沼肥+钝化剂,菠菜及其茎叶部位中重金属Cd、Cr含量和生物富集系数均降低,根茎叶中重金属Cd、Cr含量和生物富集系数大小顺序均为根>茎>叶;方差分析结果表明,施加沼肥或沼肥+钝化剂对菠菜及其茎叶部位重金属Cd、Cr含量和生物富集系数均有显著影响(P<0.05);菠菜中重金属Cd、Cr含量与土壤重金属Cd、Cr有效态含量及可交换态含量的相关性均为显著正线性相关。(3)施加沼肥或沼肥+钝化剂,土壤重金属Cd主要以有机络合态和有机结合态为主,Cr主要以残渣态为主,有机结合态和有机络合态次之。土壤中水溶态、可交换态Cd、Cr在试验后比例均降低,残渣态在试验后比例升高。重金属Cd、Cr试验前土壤主要与富里酸(FA)结合,试验后各处理与胡敏酸(HA)结合的重金属Cd、Cr的比例呈现递增趋势;方差分析结果表明,施加沼肥或沼肥+钝化剂对土壤中重金属Cd、Cr的水溶态、可交换态、残渣态和HA-Cd、HA-Cr比例均有显著影响(P<0.05)。(4)采用傅里叶变换红外光谱及二维相关红外光谱对种植前后土壤的光谱特征进行了分析,试验前后土壤的红外光谱具有相似的光谱特征,仅在相对强度上存在一定的差异。土壤中酰胺化合物、碳水化合物、蛋白质、糖类等有机物含量减少,芳香族等腐殖质含量增加。通过吸收峰强度分析结果可知:施加沼肥+钙镁磷肥处理土壤腐殖化程度最高。在1800cm~(-1)～900cm~(-1)波数范围内的二维相关红外光谱显示,土壤中蛋白质类物质和芳香环类物质和多糖类物质过程中均存在协同作用,但不同处理表现出其它不同的协同作用,施加沼肥或沼肥+钝化剂有利于增强土壤的腐殖化程度,施加沼肥+钙镁磷肥处理效果更加明显。

Soil heavy metal pollution has threatened human health and life safety,and the harm of heavy metals is closely related to its occurrence form.As an important organic fertilizer,how to apply biogas fertilizer scientifically is very important to improve the quality and yield of agricultural products and reduce heavy metal pollution.The effects of biogas fertilizer and different kinds of passivators(zeolite,red mud,calcium magnesium phosphate fertilizer)on soil heavy metals Cd and Cr were studied by pot experiment.The BCR continuous extraction method was used to analyze the forms of heavy metals,and the changes of the content and distribution rate of heavy metals,the passivation effect and the soil pollution index were analyzed.The bioaccumulation coefficient was calculated by detecting the heavy metal contents in roots,stems and leaves of spinach,and the correlation between the contents of exchangeable and available forms in soil and the contents of heavy metals in spinach were analyzed In order to reduce the bioavailability of Cd and Cr in soil,the interaction between humus and heavy metal speciation in soil was analyzed by the extraction method of KCl、Na_4P_2O_7、Na OH、HNO_3.Fourier transform infrared spectroscopy and two-dimensional correlation spectrum were used to analyze the spectral characteristics of soil before and after the experiment.The binding mechanism of heavy metals Cd,Cr and organic matter in soil was clarified The reasonable utilization of the liquid and the treatment of soil heavy metal pollution provide certain scientific data.The main conclusions are as follows:(1)When biogas fertilizer or biogas fertilizer+passivator was applied to the soil,the exchangeable contents and distribution rates of Cd and Cr decreased,while the residual contents and their distribution rates increased,The results of variance analysis showed that the contents and distribution rates of exchangeable and residual forms of Cd and Cr,as well as the passivation effects of exchangeable and available forms of Cd and Cr were significantly affected by biogas fertilizer or biogas fertilizer+passivator(P<0.05).(2)Applying biogas fertilizer or biogas fertilizer+passivator,the contents of Cd,Cr and bioconcentration coefficient in spinach and its stems and leaves decreased,and the order of Cd,Cr content and bioconcentration coefficient in roots,stems and leaves was root>stem>leaf.The results of variance analysis showed that the application of biogas fertilizer or biogas fertilizer+passivator had significant effects on Cd,Cr content and bioconcentration coefficient of spinach and its stems and leaves There was a significant positive linear correlation between the contents of Cd and Cr in spinach and the contents of available and exchangeable Cd and Cr in soil.(3)When biogas fertilizer or biogas fertilizer+passivator was applied,the main heavy metal Cd in soil was organic complex and organic bound,Cr was mainly in residual form,followed by organic bound and organic complex.The proportion of water-soluble and exchangeable Cd and Cr in soil decreased after the test,while the proportion of residual Cd and Cr increased.The results of variance analysis showed that the application of biogas fertilizer or biogas fertilizer+passivator had significant effects on the water-soluble,exchangeable and residual forms of Cd and Cr,and the proportion of HA-Cd and HA-Cr in the soil was significantly affected by biogas fertilizer or biogas fertilizer+passivator(P<0.05).(4)Fourier transform infrared spectroscopy(FTIR)and two-dimensional correlation infrared spectroscopy(2D-IR)were used to analyze the spectral characteristics of soil before and after planting.The contents of amide compounds,carbohydrates,proteins,sugars and other organic matter decreased,while the contents of aromatic humus increased.The results of absorption peak intensity analysis showed that the application of biogas fertilizer and calcium magnesium phosphate fertilizer had the highest degree of soil humification.In the range of 1800cm~(-1)～900cm~(-1),the two-dimensional correlation infrared spectra showed that there were synergistic effects in the process of protein,aromatic ring and polysaccharide in soil,but different treatments showed different synergistic effects.Biogas fertilizer or biogas fertilizer+passivator could enhance the degree of soil humification,and the effect of biogas fertilizer+calcium magnesium phosphate fertilizer was more obvious.