设施菜地土壤重金属累积及影响因素研究

为了解设施菜地土壤重金属累积规律及影响因,通过在全国8个省具有代表性的设施蔬菜产区采集土壤和肥料样品,系统研究了设施栽培年限、肥料施用、土壤性质对设施菜地土壤重金属Cu、Zn、Cd累积量及活度的影响.结果表明:与露天栽培相比,设施条件下随着栽培年限的延长,土壤Cu、Zn和Cd的全量和有效态浓度均呈明显的累积趋势,栽培年限>15a时的设施土壤Cu、Zn和Cd的全量和有效态浓度分别是露天栽培土壤的1.57、2.16、1.67、3.28、1.96、2.00倍.Pearson分析表明设施菜地土壤Cu、Zn、Cd均与土壤SOM呈极显著相关,说明其在来源上较强的相似性,进一步对设施栽培土壤主要投入品中Cu、Zn、Cd含量分析表明,猪粪、商品有机肥及土壤调理剂中Cu、Zn均超过了100mg/kg,Cd超过了1.0mg/kg,且投入量较大,是设施栽培土壤中Cu、Zn、Cd的主要贡献者,而秸秆和部分化肥(如尿素、硫酸钾)中的Cu、Zn、Cd含量均极低,对设施栽培土壤累积贡献微乎其微.pH值和CEC是影响Cu、Zn、Cd在土壤中累积活度的关键因素,其中随着pH值的升高土壤Cu活度表现了先升高后下降的趋势,而土壤Cd活度则表现了持续下降的趋势,仅在pH<6.26时达到了显著相关水平;土壤CEC的升高对土壤Cu活度表现了先下降后升高再下降的趋势,土壤Cd活度表现了先升高后缓慢下降再升高的趋势,而土壤Zn活度仅在CEC<5.83时随着CEC升高表现下降显著线性相关趋势.因此,防止设施栽培土壤Cu、Zn、Cd的累积与污染,选择重金属含量低的肥料和调控土壤理化特性(尤其是pH值、CEC)则是缓解设施栽培土壤重金属累积速率进而确保蔬菜质量安全的有效途径.

Study on the accumulation of heavy metals and influencing factors in the soil of facility vegetable fields

The accumulation of heavy metals in facility cultivation soil has become a prominent environmental problem. In this study, by collecting soil and fertilizer samples from representative facility vegetable production areas in eight provinces across the country, we systematically studied the effects of facility cultivation years, fertilizer application, and soil properties on the accumulation and activity of heavy metals Cu, Zn, and Cd in facility vegetable soils. The results showed that compared with open-air cultivation, the total and available concentration of Cu, Zn and Cd in the soil showed an obvious accumulation trend with the extension of planting years under facility conditions; when the years of cultivation were more than 15a, the total and available Cu, Zn, and Cd concentration in the facility soils were 1.57, 2.16, 1.67, 3.28, 1.96, and 2.00 times higher than that of the open-air cultivation soil, respectively. Pearson analysis revealed that the Cu, Zn, and Cd concentrations in the facility soil were associated with the soil SOM at an extremely significant level, indicating a high similarity in source among the heavy metals. Further analysis of the content of Cu, Zn, Cd, and soil SOM reached a very significant correlation, indicating a strong similarity in source, and further analyses on the contents of Cu, Zn, and Cd sourced from main agromaterials, showed the concentrations of both Cu and Zn in pig manure, commercial organic fertilizer and soil conditioner were greater than 100mg/kg, and that of Cd exceeded 1.0mg/kg. These agromaterial-sourced Cu, Zn and Cd could be considered the main contributors to the total amount of the heavy metals in the facility soil due to their large inputs to the soil. While the Cu, Zn, and Cd in straw and some chemical fertilizers (such as urea and K₂SO₄) were at an extremely low level, and their contributions to the accumulated heavy metals in the facility soil were basically neglectable; Both pH and CEC were confirmed as key factors influencing the cumulative activities of Cu, Zn, and Cd in the soil. As the pH increased, the soil Cu activity showed a trend of rising at first and then decreasing, while the soil Cd activity showed a continuous downtrend, reaching a significant correlation level only when pH<6.26; As the increase of soil CEC, the acidity of soil Cu showed a downtrend at first, followed by rising and then downtrend again; and the activity of soil Cd showed rising first, followed by slight downtrend and then rising again. While the activity of soil Zn only showed a significant linear correlation trend when CEC was lower than 5.83 as CEC increased. Therefore, preventing the accumulation and pollution of Cu, Zn, and Cd in the facility cultivation soil, choosing fertilizers with low heavy metal content and regulating the physical and chemical properties of the soil (especially pH and CEC) are effective means to alleviate the accumulation velocity of heavy metals in the facility cultivation soil and ensure the quality and safety of vegetables.