Ali Waqar, Zhang Hua, Mao Kang, Shafeeque Muhammad, Aslam Muhammad Wajahat, Yang Xuefeng, Zhong Li, Feng Xinbin, Podgorski Joel
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China..
Sci Total Environ. 2022 Jun 20;826:153910. doi: 10.1016/j.scitotenv.2022.153910. Epub 2022 Feb 17.
Chromium (Cr) contamination in paddy soil-rice systems threatens human health through the food chain. This study used a new dataset of 500 paddy soil and plant tissue samples collected in the rice-growing regions of Sindh and Punjab Provinces of Pakistan. Overall, 97.4% of grain samples exceeded the Cr threshold values of 1.0 mg kg, determined by the China National Food Standard (CNFS). The Cr in paddy soil, 62.6% samples exceeding the China natural background threshold value (90 mg kg) for Cr concentration in paddy soil, and lower than the (pH-dependant > 7.5 threshold value for Cr 350 mg kg) as determined by China Environmental Quality Standards (EQSs) for paddy soil (GB15618-2018). Geographically weighted regression (GWR) modelling showed spatially nonstationary correlations, confirming the heterogeneous relationship between dependent (rice grain Cr) and independent paddy soil (pH, SOM, and paddy soil Cr) and plant tissue variables (shoot Cr and root Cr) throughout the study area. The GWR model was then used to determine the critical threshold (CT) for the measured Cr concentrations in the paddy soil system. Overall, 38.4% of paddy soil samples exceeding CT values confirm that the paddy soil Cr risk prevails in the study area. Furthermore, the GWR model was applied to assess the loading capacity (LC), the difference between the CT, and the actual concentration of Cr in paddy soil. Loading capacity identified potential paddy soil Cr pollution risk to rice grain and assessed the risk areas. Overall LC% of samples paddy soil Cr risk areas grade: low-risk grade I (34.6%); moderate-risk grade II (15.8%); high-risk grade III (11.2%); and very high-risk grade IV (38.4%) have been assessed in the study area. The human health index, total hazard quotient (THQ ≪ 1), indicates no potential health risk originating from Cr exposure to the population. However, the excess Cr level in paddy soil and rice grain is still a concern. The current study's results are also valuable for the national decision-making process regarding Cr contamination in the paddy soil-rice system.
稻田土壤-水稻系统中的铬（Cr）污染通过食物链威胁人类健康。本研究使用了一个新数据集，该数据集包含在巴基斯坦信德省和旁遮普省水稻种植区采集的500个稻田土壤和植物组织样本。总体而言，97.4%的谷物样本超过了中国国家食品标准（CNFS）规定的1.0毫克/千克的铬阈值。稻田土壤中的铬，62.6%的样本超过了中国稻田土壤铬浓度的自然背景阈值（90毫克/千克），且低于中国稻田土壤环境质量标准（EQSs，GB15618 - 2018）所确定的（pH值大于7.5时铬的阈值350毫克/千克）。地理加权回归（GWR）建模显示出空间非平稳相关性，证实了在整个研究区域内，因变量（水稻籽粒铬）与自变量稻田土壤（pH值、土壤有机质和稻田土壤铬）以及植物组织变量（地上部铬和根部铬）之间存在异质关系。然后使用GWR模型确定稻田土壤系统中实测铬浓度的临界阈值（CT）。总体而言，38.4%的稻田土壤样本超过CT值，这证实了研究区域内稻田土壤铬风险普遍存在。此外，应用GWR模型评估了负荷能力（LC），即CT与稻田土壤中铬实际浓度之间的差值。负荷能力确定了稻田土壤铬对水稻籽粒的潜在污染风险，并评估了风险区域。研究区域内已评估的稻田土壤铬风险区域样本的总体LC%等级为：低风险I级（34.6%）；中度风险II级（15.8%）；高风险III级（11.2%）；以及极高风险IV级（38.4%）。人类健康指数，即总危害商（THQ远小于1），表明人群因接触铬而不存在潜在健康风险。然而，稻田土壤和水稻籽粒中过量的铬水平仍然令人担忧。本研究的结果对于国家在稻田土壤-水稻系统铬污染方面的决策过程也具有重要价值。
