Research Institute of Poyang Lake, Jiangxi Academy of Sciences, Nanchang 330012, China; State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
Ecotoxicol Environ Saf. 2024 Sep 15;283:116825. doi: 10.1016/j.ecoenv.2024.116825. Epub 2024 Aug 1.
To better understand the impact of long-term irrigation practices on arsenic (As) accumulation in agricultural soils, 100 soil samples from depths of 0-20 cm were collected from the Datong basin, where the As-contaminated groundwater has been used for irrigation for several decades. Soil samples were analyzed for major elements, trace elements, and As, Fe speciation. Results reveal As content ranging from 4.00 to 14.5 mg/kg, an average of 10.2 ± 2.05 mg/kg, consistent with surveys conducted in 1998 and 2007. Arsenic speciation ranked in descending order as follows: As associated with silicate minerals (As, 29.70 ± 7.53 %) > amorphous Fe-minerals associated As (As, 26.40 ± 3.27 %) > crystalline Fe-minerals associated As (As, 24.02 ± 4.60 %) > strongly adsorbed As (As, 14.29 ± 2.81 %) > As combined with carbonates and Fe-carbonates (As, 2.30 ± 0.44 %) > weakly adsorbed As (As, 2.59 ± 1.00 %). The anomalous negative correlation between As and Fe content reflects the primary influence of soil provenance. Evidence from major element compositions and rare earth element patterns indicates that total As and Fe contents in soils are controlled by parent materials, exhibiting distinct north-south differences (As: higher levels in the north, lower levels in the south; Fe: higher levels in the south, lower levels in the north). Evidence from the Chemical Index of Alteration (CIA) and As/Ti ratio suggests that chemical weathering has led to As enrichment in the central basin. Notably, relationships such as As/Ti, As/Ti with CIA and total Fe content indicate significant influences of irrigation practices on adsorbed As (both weakly and strongly adsorbed) contents, showing a pattern of higher levels in the central basin and lower levels in the Piedmont. However, total As content remained stable after long-term irrigation, potentially due to the re-release of accumulated As via geochemical pathways during non-irrigated periods. These findings demonstrate that the soil systems can naturally remediate exogenous As contamination induced by irrigation practices. Quantitative assessment of the balance between As enrichment and re-release in soil systems is crucial for preventing soil As contamination, highlighting strategies like water-saving techniques and fallow periods to manage As contamination in agricultural areas using As-contaminated groundwater for irrigation.
为了更好地了解长期灌溉实践对农业土壤中砷（As）积累的影响，从大同盆地采集了 100 个 0-20cm 深度的土壤样本，该盆地的地下水已被用于灌溉数十年。对土壤样本进行了常量元素、微量元素和 As、Fe 形态分析。结果表明，As 含量范围为 4.00 至 14.5mg/kg，平均值为 10.2±2.05mg/kg，与 1998 年和 2007 年的调查结果一致。As 形态按降序排列如下：与硅酸盐矿物结合的 As（As，29.70±7.53%）>与无定形 Fe 矿物结合的 As（As，26.40±3.27%）>与结晶 Fe 矿物结合的 As（As，24.02±4.60%）>强吸附 As（As，14.29±2.81%）>与碳酸盐和 Fe-碳酸盐结合的 As（As，2.30±0.44%）>弱吸附 As（As，2.59±1.00%）。As 与 Fe 含量之间的异常负相关反映了土壤来源的主要影响。主量元素组成和稀土元素模式的证据表明，土壤中的总 As 和 Fe 含量受母质控制，表现出明显的南北差异（As：北部较高，南部较低；Fe：南部较高，北部较低）。化学蚀变指数（CIA）和 As/Ti 比值的证据表明，化学风化导致了中部盆地的 As 富集。值得注意的是，As/Ti、As/Ti 与 CIA 和总 Fe 含量之间的关系表明，灌溉实践对吸附态 As（弱吸附态和强吸附态）含量有显著影响，表现为中部盆地含量较高，山前地带含量较低。然而，长期灌溉后总 As 含量保持稳定，这可能是由于非灌溉期通过地球化学途径重新释放了积累的 As。这些发现表明，土壤系统可以自然修复灌溉实践引起的外源 As 污染。定量评估土壤系统中 As 富集和再释放之间的平衡对于防止土壤 As 污染至关重要，这凸显了节水技术和休耕期等策略的重要性，以管理使用受 As 污染的地下水进行灌溉的农业区的 As 污染。
