黄土高原白水县不同种植年限苹果园土壤重金属含量特征与风险评价

Characteristics and Risk Assessment of Heavy Metal Content in Soils of Apple Orchard with Different Cultivating Years in Baishui County on the Loess Plateau

为研究不同种植年龄苹果园土壤中的重金属元素分布特点,评价其污染现状和风险。以黄土高原陕西省白水县果园土壤为研究对象,利用电感耦合等离子质谱法方法对5种不同年龄(5年、10年、15年、20年和25年)苹果园土壤和现代农田土壤以及自然土壤的重金属含量状况进行了测量,并结合单因子污染指数和内梅罗多因子综合指数评价法开展重金属污染风险评估。结果表明Cr, Ni, As, Pb, Hg等元素的平均含量在农田土壤中比苹果园土壤中的高,这些重金属元素在农田土壤中更容易富集;而在苹果园土壤中,Ni, Cu, As, Hg等的平均含量在25年苹果园土壤中相对高于其他年龄苹果园土壤;从综合污染指数看,农田土壤中最高,苹果园土壤中则是随着种植年限的增加而增大。由此说明随着种植年限增加,苹果园土壤中重金属的富集会逐渐显现。但是,以无公害果园和绿色食品产地土壤环境质量为标准,白水土壤完全符合无公害和绿色食品产地对土壤环境的要求。

In order to study enrichment characteristics of heavy metal elements of soils from different cultivating years apple orchard and evaluate their heavy metal pollution risk, we employed inductively coupled plasma mass spectrometry(ICP-MS) method to determine the heavy metal contents of soils of apple orchards with 5 different cultivating years(5 a, 10 a, 15 a, 20 a, and 25 a) and soil in modern farmland from Baishui County in the Loess Plateau, and used the single-factor pollution index(Pi) and Nemerow multi-factor comprehensive index(NCI) to evaluate heavy metal pollution risk. The results show that the average contents of Cr, Ni, As, Pb, Hg in soil of farmland is higher than those in soil of apple orchard, suggesting that these heavy metal elements are more likely to be enriched in soil of farmland. The average contents of Ni, Cu, As, Hg in soil of the 25-year apple orchard are relatively higher than those of soils in the other apple orchards, indicating the accumulation of heavy metals in soil of the apple orchard increases with the increase of cultivating years. From the perspective of the comprehensive pollution index, the soil of farmland is the highest, while the index of soil in apple orchard increases with the increase of cultivating years. Pollution risk based on pollution indexes Pi and NCI suggests that the soils of the apple orchards can meet the heavy metal quality standard of pollution-free fruit and green food production.