Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
Gansu Salinization Field Observation and Research Station, Lanzhou 730000, China.
Int J Environ Res Public Health. 2022 Oct 25;19(21):13880. doi: 10.3390/ijerph192113880.
Soil is an important natural resource in the agricultural areas of northwest China. The heavy metal concentration and ecological risk assessments are crucial for food safety and human health. This work collected 35 surface soil samples and focused on a typical soda soil quality of the Hetao Plain in Bayannur, which is an important grain production base in northern China. The concentration and composition of heavy metal (arsenic (As), cobalt (Co), copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), nickel (Ni), zinc (Zn)), soluble salts, total organic carbon (TOC), and minerals of the surface soils were analyzed to assess the biotoxicity, ecological risk, sources, and influencing factors of heavy metals in these soda soil from this region. The enrichment factors () showed that As, Co, Cu, and Pb were not contaminated in these soils, while Cd, Cr, Hg, Ni, and Zn were lightly contaminated. The index of geoaccumulation () for the soda soils indicated that Co and Pb were uncontaminated, and Cr, Cd, Ni, Zn, Hg, Cu, and As were lightly contaminated. The potential ecological risk index () indicated there were no or low risks for As, Co, Cr, Cu, Ni, Pb, and Zn. Although the concentrations of Cd and Hg in the soil were low, the two heavy metals exhibited moderate-high ecological risk because they have high biological toxicity. Cd in the soils from Hetao Plain in Bayannur is mainly exchangeable and reducible fractions. The other heavy metals in these soda soils are mainly in residue fraction, implying that their mobility is low and not easily absorbed and used by plants. Heavy metal fractions, principal component analysis (PCA), and correlation analysis showed that As, Co, Cr, Cu, and Pb were mainly from natural sources, while Ni, Cd, and Zn were mainly from anthropogenic discharge-related irrigation, fertilizers, and pesticide application, and Hg was mainly from winter snowfall in the study area. Naturally sourced metal elements have obvious sediment properties, and their adsorption by clay minerals and coupling with organic matter along with sediment transport sorting. The salinity and pH of soda soils in the study area have a highly positive correlation, hence the influence of factors on the concentrations of soil heavy metals are consistent. For anthropogenically imported heavy metals, increasing salinity and pH promote the precipitation of metallic elements in water. Cd is present as an exchangeable and reducible fraction, while Ni and Zn are mainly sequestered by organic matter and clay minerals.
土壤是中国西北地区农业区的重要自然资源。重金属浓度和生态风险评估对于食品安全和人类健康至关重要。本研究采集了 35 个表层土壤样品，重点研究了中国北方重要粮食生产基地巴彦淖尔市河套平原的典型苏打土质量。分析了表层土壤中重金属（砷（As）、钴（Co）、铜（Cu）、铅（Pb）、镉（Cd）、铬（Cr）、汞（Hg）、镍（Ni）、锌（Zn））、可溶性盐、总有机碳（TOC）和矿物的浓度和组成，以评估该地区苏打土中重金属的生物毒性、生态风险、来源和影响因素。富集因子（EF）表明，这些土壤中 As、Co、Cu 和 Pb 没有受到污染，而 Cd、Cr、Hg、Ni 和 Zn 则受到轻度污染。苏打土的地积累指数（Igeo）表明 Co 和 Pb 没有受到污染，Cr、Cd、Ni、Zn、Hg、Cu 和 As 则受到轻度污染。潜在生态风险指数（RI）表明，As、Co、Cr、Cu、Ni、Pb 和 Zn 均不存在或风险较低。尽管土壤中 Cd 和 Hg 的浓度较低，但由于它们具有较高的生物毒性，这两种重金属仍表现出中度到高度的生态风险。巴彦淖尔市河套平原土壤中的 Cd 主要以可交换态和还原态为主。这些苏打土中的其他重金属主要以残渣态为主，这表明它们的迁移性较低，不易被植物吸收和利用。重金属形态、主成分分析（PCA）和相关性分析表明，As、Co、Cr、Cu 和 Pb 主要来源于自然源，而 Ni、Cd 和 Zn 主要来源于与灌溉、施肥和农药施用有关的人为排放，Hg 主要来源于研究区冬季的降雪。自然源金属元素具有明显的沉积特性，它们通过粘土矿物的吸附和与有机质的结合以及随沉积物的搬运分选而与有机质结合。研究区苏打土的盐分和 pH 值呈高度正相关，因此影响土壤重金属浓度的因素是一致的。对于人为输入的重金属，盐分和 pH 值的增加促进了水中金属元素的沉淀。Cd 以可交换态和还原态为主，而 Ni 和 Zn 主要被有机质和粘土矿物固定。
