Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Key Laboratory of Soil Resources & Biotech Applications, Northwestern Bio-Agriculture Research Center, Chinese Academy of Sciences, Xi'an, 710043, China.
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Xi'an Botanical Garden of Shaanxi Province, Institute of Botany of Shaanxi Province, Xi'an, 710061, China.
Environ Pollut. 2018 Oct;241:412-421. doi: 10.1016/j.envpol.2018.05.086. Epub 2018 May 31.
The diffusive gradients in thin films (DGT) technique is recognized to have advantages over traditional techniques. For example, the passive measurement generally follows the principle of metal uptake by plants, and its result incorporates the influences of soil properties, which may make DGT a good protocol for improving soil quality guidelines (SQGs). However, DGT has rarely been applied to assess Cd phytoavailability in soils under greenhouse vegetable production (GVP) systems. In this study, 29 turnips (Raphanussativus L.), 21 eggplants (Solanum melongena L.) and their corresponding soils were collected from GVP systems in Dongtai and Shouguang, eastern China. Simple linear regression and stepwise regression were performed using the soil Cd content and soil properties to predict the vegetable Cd content. Soil thresholds were derived based on both total and available Cd concentrations. The results showed that total Cd, DGT-measured Cd (DGT-Cd), soil-solution Cd (Soln-Cd) and CaCl-extractable Cd (CaCl-Cd) were all significantly correlated with vegetable Cd. DGT-Cd had the best correlation with turnip Cd. The total Cd threshold values ranged from 4.87 (pH 6.5) to 5.18 (pH 7.5) mg kg for turnips and 14.60 (pH 6.5) to 14.90 (pH 7.5) mg kg for eggplants. These Cd thresholds were higher than the current SQGs. The predicted of turnip Cd by DGT-Cd was not improved significantly by further considering the soil properties. The calculated soil threshold of DGT-Cd was 5.35 μg L for turnips. However, the predicted soil threshold of DGT-Cd for eggplant was improved by including SOM, with R values from 0.53 to 0.70. The DGT-Cd threshold was calculated as 1.81 μg L for eggplant (30.0 g kg SOM). In conclusion, whether DGT measurements are independent of soil properties and preferable for the evaluation of Cd phytoavailability and the generation of soil thresholds remains to be clarified in future research.
薄膜扩散梯度（DGT）技术被认为具有优于传统技术的优势。例如，被动测量通常遵循植物摄取金属的原理，其结果包含了土壤性质的影响，这使得 DGT 成为改善土壤质量指南（SQG）的一个很好的方案。然而，DGT 很少应用于评估温室蔬菜生产（GVP）系统下土壤中的 Cd 植物可利用性。在这项研究中，从中国东部的东台和寿光的 GVP 系统中采集了 29 个萝卜（Raphanussativus L.）、21 个茄子（Solanum melongena L.）及其相应的土壤。采用土壤 Cd 含量和土壤性质对蔬菜 Cd 含量进行简单线性回归和逐步回归分析。根据总 Cd 和有效 Cd 浓度得出土壤阈值。结果表明，总 Cd、DGT 测定的 Cd（DGT-Cd）、土壤溶液 Cd（Soln-Cd）和 CaCl 提取的 Cd（CaCl-Cd）均与蔬菜 Cd 显著相关。DGT-Cd 与萝卜 Cd 相关性最好。萝卜的总 Cd 阈值范围为 4.87（pH 6.5）至 5.18（pH 7.5）mg kg，茄子的总 Cd 阈值范围为 14.60（pH 6.5）至 14.90（pH 7.5）mg kg。这些 Cd 阈值高于现行的 SQG。通过进一步考虑土壤性质，DGT-Cd 对萝卜 Cd 的预测并没有显著提高。计算出的 DGT-Cd 对萝卜的土壤阈值为 5.35μg L。然而，通过包含 SOM，对茄子的 DGT-Cd 预测土壤阈值得到了改善，R 值从 0.53 到 0.70。DGT-Cd 阈值计算为 1.81μg L 用于茄子（30.0g kg SOM）。总之，DGT 测量是否独立于土壤性质，以及是否更适合评估 Cd 植物可利用性和生成土壤阈值，仍有待在未来的研究中加以澄清。
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