State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, P. O. Box 821, Nanjing, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Co-Innovation Center for the Sustainable Forestry in Southern China/College of Biology and Environment, Nanjing Forestry University, Nanjing, 210037, China.
Environ Pollut. 2024 Jun 15;351:124061. doi: 10.1016/j.envpol.2024.124061. Epub 2024 Apr 26.
Diffusive gradients in thin films technique (DGT) is recognized as a more reliable method for determining labile heavy metal (HM) concentration in soil than traditional destructive methods. However, the current DGT measurement index, C, theoretically underestimates the true labile concentration (C) of HMs in soil and lacks direct comparability with the conventional soil HM content indices due to unit differences. Here, we proposed C, a new simple index which is defined as the HM accumulation in the binding layer, normalized to the weight of soil (optimized water content = 100% of the maximum water holding capacity) filled in the open cavity-type DGT device over a specified deployment time (optimized time = 24 h). The procedure for measuring C is analogous to that of C but includes precise determination of water content (water/dry soil) and the mass of soil filled in the cavity. We conducted measurements of Cu, Pb, Cr(Ⅵ) and As(V) as C, C, solution concentration (C), and CaCl extractable concentration (C) on three soils with a diverse range of HM concentrations. C showed significant linear correlations with all other tested indexes. The ratios of C to C varied between 0.30 and 0.98 for all HM-soil combinations with only one exception, a range much greater than C/C (typically <0.1) but lower than 1. This suggested that C may more accurately reflect C than C (theoretically underestimates C) and C(likely overestimates C). Additionally, C measurements for these four HMs exhibited a broad measure concentration range and a low detection limit (mg/kg level). Consequently, C may offer a more reliable alternative to C for characterizing C in unsaturated soils.
薄膜扩散梯度技术（DGT）被认为是一种比传统破坏性方法更可靠的方法，可用于测定土壤中不稳定重金属（HM）的浓度。然而，目前的 DGT 测量指标 C 理论上低估了土壤中 HM 的真实可利用浓度（C），并且由于单位差异，缺乏与传统土壤 HM 含量指标的直接可比性。在这里，我们提出了 C，这是一个新的简单指标，定义为结合层中 HM 的积累，归一化为在指定部署时间（优化时间=最大持水能力的 100%）内填充在开放式腔体型 DGT 装置中的土壤重量（优化水含量= 100%的最大持水能力）。测量 C 的程序类似于 C 的程序，但包括精确确定水含量（水/干土）和腔体内填充的土壤质量。我们在三种具有不同 HM 浓度的土壤上测量了 Cu、Pb、Cr(Ⅵ)和 As(V)的 C、C、溶液浓度（C）和 CaCl 可提取浓度（C）。C 与所有其他测试指标均呈显著线性相关。对于所有 HM-土壤组合，C 与 C 的比值在 0.30 到 0.98 之间变化，只有一个例外，范围远大于 C/C（通常<0.1）但低于 1。这表明 C 可能比 C（理论上低估 C）和 C（可能高估 C）更准确地反映 C。此外，这四种 HM 的 C 测量值表现出广泛的测量浓度范围和较低的检测限（mg/kg 级）。因此，C 可能是一种更可靠的替代 C 的方法，用于表征非饱和土壤中的 C。
