崇明岛芦笋种植区土壤盐碱化与重金属污染风险评估

崇明岛位于长江入海口，土壤肥沃，是上海的蔬菜生产基地之一。芦笋是一种营养丰富，口感爽脆的一种蔬菜，成为崇明岛种植的特色蔬菜。随着科学技术的高速发展，工业化加速，城市化进入快车道。农业在生产发展中遇到了许多问题，工业发展中大量的废弃物被排放和土地不科学的使用使土壤利用率下降，农业环境中土壤盐碱化和重金属污染问题变的严峻。专门针对芦笋种植区进行的土壤盐碱化程度和土壤重金属污染特征缺及芦笋农产品质量安全的风险评估。因此，本文选取崇明岛农田土壤及其栽种芦笋为研究对象，进行采样研究，进行土壤主盐碱化检测和健康风险评价方法，研究蔬菜基地土壤重金属的盐碱化程度，土壤重金属污染特征，与潜在的健康风险，为芦笋基地产业布局提供土壤盐碱特征和重金属污染含量基础数据。

研究结果表明：

芦笋种植区土壤测定阳离子：Ｋ+、Na+、Ca2+、Mg2+。平均含量为0.109 、0.174、 0.441、0.134g/kg。Ｋ+和 Mg2+含量较低。阳离子中Mg2+变异系数最大，为0.748。Ca2+含量最高，占水溶性阳离子总量的51%。芦笋种植区土壤中阴离子HCO-3，SO2-4和Cl-为主，CO2-3存在较少，HCO-3、 Cl-、 SO2-4平均含量为0.013g/kg、0.176g/kg，0.592g/kg，在土壤中SO2-4含量较高。阴离子中Cl-的变异系数最大，为0.761。土壤盐渍化类型为硫酸盐-氯化物型、氯化物-硫酸盐型和硫酸盐型。B部分出现轻度盐渍土。

崇明岛表层土壤中：As、Ca、Cd、Cr、Cu、Fe、Mg、Mn、Ni、Pb、Zn、Hg的平均值含量为11.726、5219.766、0.192、 52.686、 65.298、 29608.889、 4215.255、474.241、 23.902、 21.11、 116.038、 0.214 mg/kg。（GB15618—2018）规定的风险管制值元素都没有超过。与背景值相比，土壤中Mg Zn Cu As Hg Cd均出现了不同程度的累积,Mn、Ni、Pb出现减少。土壤中低变异系数有As，中等程度变异的有Ca、Cd、Cr、Cu、Fe、Mg、Mn、Ni、Pb、Zn，Hg属于高变异。从地质累计指数看As的平均值属于轻微污染，整体呈轻微污染状态；Cd属于无污染，但是存在局部轻微污染状态；Cr属于无污染状态；Cu属于无污染，但是存在局部轻微污染状态；Mn属于无污染状态；Ni属于无污染状态；Pb属于无污染状态；Zn属于无污染状态，但是存在局部轻微污染状态；Hg属于无污染状态，但是存在局部轻微污染污染状态。

研究区芦笋食用部分中Cr量超过食品安全国家标准（GB 2762-2022）规定限值，其他元素的含量均低于限值。芦笋对Zn 的富集系数最大，Pb富集系数最小。生物富集系数趋势为：Zn> As > Ca > Cd > Cr > Cu > Fe >Hg> Mg > Mn > Ni > Pb。在成人和儿童非致癌风险五种金属都是Cr的风险最高，在儿童致癌风险五种金属中也是Cr的风险最高，致癌风险，不论成人和儿童， Cr经芦笋摄入途径产生的致癌风险最高超过1×10-4。

主要结论：崇明芦笋种植区土壤开始出现轻微盐碱地，芦笋Cr平均值浓度均高于国标限定值。芦笋基地土壤重金属汞空间特变异系数最高，可能人为活动导致变异系数大对土壤重金属分布明显的影高，小孩经膳食途径摄入重金属的量均超过成人，健康风险更高。重金属Cd和Cr的致癌风险值超过安全线，存在一定的健康风险。

Chongming Island is located at the mouth of the Yangtze River, with fertile soil, and is one of the vegetable production bases in Shanghai. Asparagus, a nutritious and crispy vegetable, has become a characteristic crop grown in Chongming Island. With the rapid development of science and technology, acceleration of industrialization, and urbanization entering the fast lane, agriculture has encountered many problems in production development. Large amounts of industrial waste are discharged and improper land use has led to a decrease in soil utilization rate. Soil salinization and heavy metal pollution in agricultural environments have become severe problems. A risk assessment was conducted specifically for the soil salinization and heavy metal pollution characteristics in the asparagus planting area and the safety of asparagus agricultural products. Therefore, this study selected Chongming Island farmland soil and asparagus as the research objects, conducted sampling research, and evaluated soil salinization and health risk assessment methods. The degree of soil salinization and heavy metal pollution in the vegetable base soil and potential health risks were studied, providing basic data for the soil salinization characteristics and heavy metal pollution content of the asparagus base industry layout.

Research results show that:

The soil of the asparagus planting area was measured for cations: K+, Na+, Ca2+, Mg2+. The average content was 0.109, 0.174, 0.441, and 0.134g/kg, respectively. K+ and Mg2+ had lower content. The variation coefficient of Mg2+ in cations was the highest, at 0.748. Ca2+ had the highest content, accounting for 51% of the total water-soluble cations. The main anions in the soil of the asparagus planting area were HCO-3, SO2-4, and Cl-, with less CO2-3. The average content of HCO-3, Cl-, and SO2-4 in the soil was 0.013g/kg, 0.176g/kg, and 0.592g/kg, respectively, with a higher content of SO2-4 in the soil. The variation coefficient of Cl- in anions was the highest, at 0.761. The soil salinization types were sulfate-chloride type, chloride-sulfate type, and sulfate type. Mild saline soil appeared in section B.

The average content of As, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn, and Hg in the surface soil of Chongming Island was 11.726, 5219.766, 0.192, 52.686, 65.298, 29608.889, 4215.255, 474.241, 23.902, 21.11, 116.038, and 0.214 mg/kg, respectively, and none of the elements exceeded the risk control values specified in GB 15618-2018. Compared with the background values, different degrees of accumulation occurred for Mg, Zn, Cu, As, Hg, and Cd in the soil, while Mn, Ni, and Pb decreased. As had a low variation coefficient, while Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn, and Hg had a moderate degree of variation, and Hg had a high degree of variation. From the perspective of geological accumulation index, the average value of As belonged to a slightly polluted state, and the overall trend was a slightly polluted state. Cd belonged to a non-polluted state, but a local slightly polluted state existed. Cr belonged to a non-polluted state. Cu belonged to a non-polluted state, but a local slightly polluted state existed. Mn belonged to a non-polluted state. Ni belonged to a non-polluted state. Pb belonged to a non-polluted state. Zn belonged to a non-polluted state, but a local slightly polluted state existed. Hg belonged to a non-polluted state, but a local slightly polluted state existed.

The Cr content in the edible part of asparagus in the study area exceeded the limit specified in the national food safety standard (GB 2762-2022), while the content of other elements was lower than the limit. The enrichment coefficient of Zn in asparagus was the largest, and that of Pb was the smallest. The trend of biological enrichment coefficient was Zn> As> Ca> Cd> Cr> Cu> Fe> Hg> Mg> Mn> Ni> Pb. Among the five non-carcinogenic risk metals for adults and children, the risk of Cr was the highest, and among the five carcinogenic risk metals for children, the risk of Cr was also the highest. The carcinogenic risk of Cr from asparagus intake was the highest and exceeded 1×10-4 for both adults and children.

Main conclusions: Mild saline-alkali land has started to appear in the asparagus planting area of Chongming Island, and the average concentration of Cr in asparagus exceeds the national standard limit. The heavy metal mercury in the soil of the asparagus base has the highest spatial variation coefficient, which may be due to human activities, and the significant impact on the distribution of heavy metals in the soil. The amount of heavy metals ingested by children through dietary pathways is higher than that of adults, and the health risk is higher. The carcinogenic risk values of heavy metals Cd and Cr exceed the safety line, indicating a certain health risk.