中国典型设施栽培土壤Cu、Zn累积特征及风险预测

为了探明铜(Cu)和锌(Zn)在设施栽培土壤中的累积现状及潜在风险,该研究基于中国8个省16个州市典型区域的设施栽培土壤全量和有效态含量,系统分析了Cu、Zn的累积现状及风险特征,并采用分段线性模型(Split-line Model)拟合了土壤Cu、Zn有效态累积量与种植年限的关系,预测了土壤Cu、Zn累积量超风险限量值的种植年限。结果表明:1)与各省对应土壤背景值及农业土壤有效态元素丰缺指标相比,中国设施栽培土壤的全量Cu、Zn均有不同的累积效应,Cu较为明显,有效态含量大部分均达到了极丰富水平,所有样品均未出现低于缺乏临界值的现象;2)与农用地土壤污染风险筛选值相比,全量Cu、Zn平均分别超标16.03%、4.58%;与土壤有效态风险限量值相比,土壤有效态Cu的平均超限率达到了16.92%,辽宁、河南、云南的超限率分别达到了33.33%、62.50%、32.00%,表现较为严重,有效态Zn均未超限;3)基于有效态的风险评价结果表明设施栽培土壤整体安全,仅辽宁达到了轻度污染,河南和云南均达到了警戒值水平,均以元素Cu的累积贡献较为突出;4)土壤有效态Cu、Zn累积量与其种植年限具有显著正相关关系(P0.05),基于线性模型的分析结果显示,现有设施栽培条件下,连续再种植6.7、20.5、19.3 a可分别导致酸性、中性、碱性土壤中有效态Cu累积量达到风险限量值,连续再种植32.5、67.9、91.9 a可分别导致酸性、中性、碱性土壤中有效态Zn累积量达到风险限量值。因此,设施栽培土壤Cu、Zn累积具有风险,且逐年加重,需要采用合理的安全利用措施(包括修复技术、农资产品选用)来进一步保障设施农业健康可持续发展。

Accumulation characteristics and risk prediction of Cu and Zn contents in typical facility soils in China

Excessive accumulation of trace elements in the protected cultivation soil has become an important factor for the degradation of soil quality. In particular, both copper (Cu) and zinc (Zn) are micronutrient elements required for plant growth and heavy metal in the soil environment. It is highly demanding to consider the Cu, Zn cumulative risks. Therefore, this study aims to investigate the accumulation characteristics and risk prediction of Cu, Zn content in the protected cultivation soil. A total of 131 soil samples were also collected using 5-point sampling in the typical regions of 16 cities in 7 provinces and 1 autonomous region (including Liaoning, Hebei, Shandong, Henan, Shaanxi, , Jiangsu, Yunnan, and Ningxia) in China. The cumulative status and risk characteristics of Cu and Zn were systematically analyzed using the total and available content of the soil. The relationship between the accumulation of available Cu, Zn, and the planting years was fitted to predict the risk of Cu and Zn accumulation exceeding the limit value. The results showed that: 1) The total Cu and Zn exhibited an accumulative characteristic in the protected cultivation soil, except that Cu presented a slight decrease in Jiangsu. The effective state content of Cu and Zn (except that Zn at a relatively rich level both in Shaanxi and Jiangsu) reached an extremely rich level, where there was no state below the critical value. Noted that the soil background values in each province were compared with the abundance and deficiency indexes of soil available trace elements in the agricultural system. 2) The total amount of Cu and Zn in the soil exceeded the standard by 16.03% and 4.58%, respectively, compared with the screening value of farmland soil. The average exceeding limit rate reached 16.92%, while Liaoning, Henan and Yunnan were observed the most serious up to 33.33%, 62.50%, and 32.00%, respectively, compared with the risk limits of soil available Cu and Zn. 3) The risk assessment showed that the overall performance of protected cultivation soil was safe using the effective state. The samples from Liaoning, Henan, and Yunnan reached the level of lightly, lightly pollution, and warning value level, respectively. The cumulative risks of elemental Cu were more serious than Zn element. 4) There was a significant positive correlation between the accumulations of soil available Cu and Zn with the corresponding planting years (P<0.05). The continuous replanting for 6.7, 20.5, and 19.3 years led to the accumulation of available Cu in soils with acidic, neutral, and alkaline limit values of characteristics reach risk, respectively, under the current protected cultivated conditions. At the same time, the continuous replanting for 32.5, 67.9, 91.9 years led to the accumulation of available Zn in the soils with acidic, neutral, and alkaline limit values of characteristic reach risk. The bioavailable state of trace element was used to evaluate the exceeding limit rate of Cu and Zn, while the cumulative risk in the protected cultivated soil, in order to achieve the safe utilization via transforming the excess bioavailable to low state, (such as residue, oxidizable, and reducible state). Therefore, there was a high risk in the accumulations of Cu and Zn in the protected cultivated soil in the practice, where the trends were ever increasing year by year. Consequently, it is necessary to take reasonable and safe measures (including restoration technology and selection of agricultural materials), further to ensure the healthy and sustainable development of protected cultivated agriculture.