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首页> 外文期刊>Journal of Environmental Management >Evaluating cadmium bioavailability in contaminated rice paddy soils and assessing potential for contaminant immobilisation with biochar
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Evaluating cadmium bioavailability in contaminated rice paddy soils and assessing potential for contaminant immobilisation with biochar

机译：评估受污染稻田土壤中镉的生物利用度，并评估生物炭固定化污染物的潜力

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Cadmium (Cd) contaminated soils from the Mae Sot district in northwest Thailand, a region in which rice Cd concentrations often exceed health limits (0.4 mg/kg) set by the World Health Organisation, were examined for isotopically exchangeable Cd (Cd E values using a111Cd spike) to determine how this rates as a predictor of rice grain Cd in comparison with soil total Cd and solution extractable Cd (using the commonly applied BCR scheme and, in an attempt to distinguish carbonate bound forms, the Tessier soil sequential extraction scheme reagents). Step 1 of the BCR scheme (0.11 M CH3COOH) and step 1 of the Tessier scheme (1M MgCl2) showed the highest R2values in regressions with rice Cd (91% and 90%, respectively), but all predictors were strongly linked to rice Cd (p < 0.001) and could be used for prediction purposes. One soil, of the six tested, was an exception to this, where all predictors over-estimated grain Cd by a factor of 2.5–5.7, suggesting that rice grain Cd had been restricted here by the differing flooding regime and subsequent changes to redox conditions. E values and Tessier step 1 extractions were closely related, indicating that these measurements access similar pools of soil Cd. Separately, the isotopic exchangeability (representing bioavailability) of Cd was also assessed in two soils amended with rice husk and miscanthus biochars (0, 1, 5, 10, 15 and 20% w/w) in order to assess the utility of the biochars as a soil amendment for immobilising Cd in situ. One soil showed significant reductions in Cd E value at 5% rice husk biochar addition and at 15% miscanthus biochar addition however, based on the E value-rice grain Cd regression relationship previously established, the E values in the amended soils still predicted for a rice Cd concentration above the health limit. In the second soil, neither of the biochars successfully reduced the Cd E value. This indicates that further work is needed to customise biochar properties to suit specific soil and contaminant situations if they are to be used successfully for remediation of metal contaminated soils.
机译：对泰国西北部湄索地区（该地区稻米Cd浓度经常超过世界卫生组织设定的健康限值（0.4μmg/ kg）的区域）中的镉（Cd）污染土壤进行了同位素交换Cd（ a111Cd穗数），以确定与土壤总Cd和溶液可萃取Cd相比，水稻谷粒Cd的预测指标如何（使用常用的BCR方案，并试图区分碳酸盐结合形式，Tessier土壤顺序萃取方案试剂）。 BCR方案的第1步（0.11 CHM CH3COOH）和Tessier方案的第1步（1M MgCl2）在水稻Cd回归中显示最高的R2值（分别为91％和90％），但所有预测因子均与水稻Cd紧密相关（p <0.001），可用于预测目的。在这六种土壤中，有一种土壤是例外，所有预测因素高估了谷物Cd的2.5-5.7倍，这表明稻米Cd在这里受到不同洪水方法和随后氧化还原条件变化的限制。 。 E值与Tessier步骤1的提取量密切相关，表明这些测量值可访问相似的土壤Cd库。另外，还在两种用稻壳和桔梗生物炭（0、1、5、10、15和20％w / w）改良的土壤中评估了镉的同位素交换能力（代表生物利用度），以评估生物炭的效用。作为土壤固定剂，用于原位固定Cd。一种土壤在添加5％稻壳生物炭和添加15％桔类生物炭时显示Cd E值显着降低，但是，根据先前建立的E值-水稻籽粒Cd回归关系，经修正的土壤中的E值仍可预测为大米中镉的浓度超过健康极限。在第二种土壤中，两种生物炭均未成功降低Cd E值。这表明，如果要成功地将其用于金属污染土壤的修复，则需要进一步的工作来定制生物炭的特性以适合特定的土壤和污染物情况。

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