淮北冲积平原棕壤区饲料-猪粪-发酵沼液-水稻田土壤系统重金属累积迁移特征研究

Study of the Characteristics of the Accumulation,Migration,and Transformation of Heavy Metals in a Feed-Pig Manure-fermented Biogas Liquid-Paddy Soil System in the Brown Soil Area of the Huaibei Alluvial Plain

为探讨猪粪沼液还田对土壤重金属的累积迁移影响,对饲料-猪粪-发酵沼液-水稻田土壤系统开展重金属含量变化规律研究。沼液田间试验选取淮北冲积平原棕壤区水稻田,设置沼液全量施用(BS)和化肥全量施用(CF)为对照的2个实验组。研究分析了生猪不同生育阶段饲料、猪粪重金属分布情况,重点分析了沼液还田对土壤重金属和环境因子的影响。结果显示:不同生猪生育阶段,饲料中重金属Cu、Zn添加含量存在差异,猪粪中Cu、Zn累积与饲料呈正相关,且保育猪粪中Cu、Zn超出农用污泥标准14.6%、53.9%。沼液重金属Cu、Zn、Cr、Cd、As和Pb平均含量分别为0.092 2、0.545 6、0.018 9、0.000 98、0.004 5、0.005 1 mg/kg,均未超过灌溉水标准(GB 5084—2005)限值。沼液全量(BS)水稻田施用后,0~20、20~40 cm土层Cu、Zn、Cr和As含量较化肥施用(CF)均有所降低,Pb、Cd含量升高,Cd平均含量分别为14.73、15.07 mg/kg,严重超出《农用地土壤污染风险管控标准》限值。土壤中Cu、Zn的累积与沼液Cu、Zn含量负相关,土壤中As与沼液中Cu、As呈负相关。冗余分析表明,不同土层中,土壤总氮(TN)、电导率(EC)和pH负向影响Cu的累积,含水率(MC)正向影响土壤Cu、Pb的累积。

To explore the impact of swine manure and digestate on the accumulation and migration of heavy metals in soil and to study the changes in heavy metal content in soil systems from feed-swine manure-fermented digestate-rice paddies, a field experiment involving digestate was performed on rice paddies in the brown loam area of the Huabei alluvial plain. Two experimental groups were set up, with the digestate(BS) and chemical fertilizer(CF) applied as controls. This study analyzed the distribution of heavy metals in feed and pig manure at different fertility stages in pigs, focusing on the effects of the return of biogas to the field on soil heavy metals and environmental factors. The results revealed differences in the contents of the heavy metals Cu and Zn in feed at different fertility stages, and the accumulation of Cu and Zn in pig manure was positively correlated with that in feed. The Cu and Zn concentrations in the nursery pig manure exceeded the agricultural sludge standard by 14.6% and 53.9%, respectively. The average contents of the heavy metals Cu, Zn, Cr, Cd, Asm, and Pb in the biogas were 0.092 2, 0.545 6, 0.018 9, 0.000 98, 0.004 5, and 0.005 1 mg·kg–1, respectively, and none of them exceeded the limits of the standard for irrigation water(GB5084-2005). After the application of the full amount of biogas(BS) to the rice field, the contents of Cu, Zn, Cr, and As in the 0-20 and 20-40 cm soil layers were lower than those in the chemical fertilizer(CF) treatment, and the contents of Pb and Cd were elevated, with average Cd concentrations of 14.73 and 15.07 mg·kg^(–1), respectively, which significantly exceeded the limits of the Standards for Risk Control and Management of Soil Contamination of Agricultural Land. The accumulation of Cu and Zn was closely negatively correlated with the amount of biogas Cu and Zn, and the As concentration was negatively correlated with the Cu and As in the digestate. Redundancy analysis revealed that in the different soil layers, the soil total nitrogen(TN), electrical conductivity(EC), and pH negatively affected the accumulation of Cu, and the water content(MC) positively affected the accumulation of soil Cu and Pb.