崇明岛芦笋种植区土壤盐碱化和重金属污染特征及健康风险评估

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 vegetable grown on Chongming Island. With the rapid development of science and technology, industrialization and urbanization are accelerating. Agriculture has encountered many problems in production development, such as the discharge of large amounts of industrial waste and the unscientific use of land, which have led to a decline in soil utilization efficiency. The problems of soil salinization and heavy metal pollution in agricultural environments have become severe. This article focuses on the risk assessment of soil salinization, heavy metal pollution, and product quality and safety of asparagus planting areas. Therefore, this study selected Chongming Island agricultural soil and asparagus planting as the research object, conducted sampling research, and studied the salinization degree of vegetable base soil, the characteristics of heavy metal pollution, and the potential health risks, providing basic data for the soil salinization characteristics and heavy metal pollution content of asparagus base industrial layout.

The research results show that: The cations K+, Na+, Ca2+, and Mg2+ in the soil of the asparagus planting area were determined, with average contents of 0.109, 0.174, 0.441, and 0.134 g/kg, respectively. K+ and Mg2+ contents were low, and Mg2+ had the highest variation coefficient of 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 contents of HCO- 3, Cl-, and SO2- 4 in the soil were 0.013, 0.176, and 0.592 g/kg, respectively, with high SO2- 4 content. Cl- had the highest variation coefficient of 0.761. The soil salinization types were sulfate-chloride, chloride-sulfate, and sulfate. Mild saline soil appeared in part B.

The average contents of As, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn, and Hg in the surface soil of Chongming Island were 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 GB15618-2018. Compared with the background values, different degrees of accumulation of Mg, Zn, Cu, As, Hg, and Cd were found in the soil, while Mn, Ni, and Pb decreased. As had a low variation coefficient, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn belonged to moderate variability, and Hg had high variability. From the perspective of geological accumulation index, the average value of As was slightly polluted, and the overall soil was slightly polluted; Cd was not polluted, but there was a local slight pollution status; Cr was not polluted; Cu was not polluted, but there was a local slight pollution status; Mn was not polluted; Ni was not polluted; Pb was not polluted; Zn was not polluted, but there was a local slight pollution status; Hg was not polluted, but there was a local slight pollution status.

The Cr content in the edible part of asparagus in the study area exceeded the limit set by the national food safety standard (GB 2762-2022), and the content of other elements was lower than the limit. Asparagus had the highest enrichment coefficient for Zn, and the lowest for Pb. The trend of biological enrichment coefficient was: Zn> As> Ca> Cd> Cr> Cu> Fe> Hg> Mg> Mn> Ni> Pb. In both adults and children, Cr had the highest risk among the five non-carcinogenic metals, and also had the highest risk among the five carcinogenic metals in children. Regardless of adults or children, the carcinogenic risk of Cr from asparagus ingestion was the highest, exceeding 1×10-4.

The main conclusions are that the soil of the asparagus planting area on Chongming Island has begun to show slight salinization, 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 variability coefficient, which may be caused by human activities and has a significant impact on the distribution of heavy metals in the soil. Children's intake of heavy metals through dietary routes is higher than that of adults, and the health risks are higher. The carcinogenic risk values of heavy metals Cd and Cr exceed the safety line, and there is a certain health risk.