连续施用沼液对土壤性质的影响及重金属污染风险评价

为实现沼液资源化利用,采用3年田间定位试验研究施用猪粪沼液对土壤理化性质的影响,并评估其对土壤潜在的重金属污染风险。田间试验种植方式为水稻—油菜轮作,施肥方式分别以清水和常规化肥为对照,另设10个猪粪沼液施用量梯度。通过单因子污染、内梅罗综合污染和Hakanson潜在生态风险指数法,评价连续施用猪粪沼液对土壤潜在的重金属污染风险。结果表明:当3年沼液施用总量为(546.25～626.00)×103 kg/hm2时,能显著提高土壤肥力,改善土壤结构,防止土壤生态功能遭破坏,保障农业安全生产,但需合理配施氮肥,防止土壤养分失衡;单因子污染指数显示土壤重金属Cd、As、Cr、Hg为轻度污染,Pb较安全;内梅罗综合污染指数显示Cd、As、Pb、Cr、Hg总体为轻度污染;Hakanson潜在生态风险指数显示Pb、Cd、Cr、As存在轻微潜在生态污染风险,Hg存在中等潜在生态污染风险,综合潜在生态污染风险程度属轻度;沼液还田引起土壤环境重金属污染的风险较小,需合理管控Hg和As可能引起的土壤环境污染问题。

The Long-term Effects of Biogas Slurry on Soil Properties and Potential Risks of Heavy Metals in Soils

In order to utilization of biogas slurry, this paper used a 3-years fixed site field experiment to study the effects of pig manure biogas slurry application on soil physical and chemical properties, and to assess the potential pollution risk of heavy metals in the soil. The planting pattern of the field experiment was rice-rape rotation, fertilization treatments included 2 controls of water and chemical fertilizer, and 10 application rates of pig manure biogas slurry. The indexes of single factor pollution, Nemerow pollution comprehensive and Hakanson pollution index of potential ecological risk were selected as evaluation indexes of the soil heavy metal pollution and potential ecological risk.The results showed that after 3-year application of biogas slurry in a total amount of(546.25~626.00)×10³ kg/hm²,the soil fertility and structure were significantly improved. It is worth to note that nitrogen fertilizer should be properly applied to cropland, in order to prevent soil nutrient imbalance. The contents of Cd, As, Pb, Cr and Hg were increased in the biogas slurry treated soils with an increasing application of biogas slurry. Furthermore, Pb, Cd, Cr, and As show slightly potential ecological pollution risk, and Hg exhibited a medium risk of potential ecological pollution, indicating biogas slurry can be safely used in agricultural production. This study indicates that the long-term application of biogas slurry is beneficial for the soil ecological function and the production of food security. Nevertheless,proper management of soil Hg and As is required to prevent soil contamination.