Andra, Research and Development Division, 1-7 rue Jean Monnet, 92298 Châtenay-Malabry, France.
Environ Sci Technol. 2011 Sep 1;45(17):7202-8. doi: 10.1021/es2011918. Epub 2011 Aug 3.
Recent studies have shown that extensive chlorination of natural organic matter significantly affects chlorine (Cl) residence time in soils. This natural biogeochemical process must be considered when developing the conceptual models used as the basis for safety assessments regarding the potential health impacts of 36-chlorine released from present and planned radioactive waste disposal facilities. In this study, we surveyed 51 French forested areas to determine the variability in chlorine speciation and storage in soils. Concentrations of total chlorine (Cl(tot)) and organic chlorine (Cl(org)) were determined in litterfall, forest floor and mineral soil samples. Cl(org) constituted 11-100% of Cl(tot), with the highest concentrations being found in the humus layer (34-689 mg Cl(org) kg(-1)). In terms of areal storage (53 - 400 kg Cl(org) ha(-1)) the mineral soil dominated due to its greater thickness (40 cm). Cl(org) concentrations and estimated retention of organochlorine in the humus layer were correlated with Cl input, total Cl concentration, organic carbon content, soil pH and the dominant tree species. Cl(org) concentration in mineral soil was not significantly influenced by the studied environmental factors, however increasing Cl:C ratios with depth could indicate selective preservation of chlorinated organic molecules. Litterfall contributions of Cl were significant but generally minor compared to other fluxes and stocks. Assuming steady-state conditions, known annual wet deposition and measured inventories in soil, the theoretical average residence time calculated for total chlorine (inorganic (Cl(in)) and organic) was 5-fold higher than that estimated for Cl(in) alone. Consideration of the Cl(org) pool is therefore clearly important in studies of overall Cl cycling in terrestrial ecosystems.
最近的研究表明,天然有机物的广泛氯化会显著影响氯(Cl)在土壤中的停留时间。在开发用于评估当前和计划中的放射性废物处置设施释放的 36 氯潜在健康影响的概念模型时,必须考虑到这一自然生物地球化学过程。在这项研究中,我们调查了 51 个法国森林地区,以确定土壤中氯形态和储存的可变性。在凋落物、森林地表和矿质土壤样品中测定了总氯(Cl(tot))和有机氯(Cl(org))的浓度。Cl(org)占 Cl(tot)的 11-100%,最高浓度出现在腐殖质层(34-689mg Cl(org)kg(-1))。就面积储存(53-400kg Cl(org)ha(-1))而言,由于其厚度较大(40cm),矿质土壤占主导地位。腐殖质层中有机氯的 Cl(org)浓度和估计保留量与 Cl 输入、总 Cl 浓度、有机碳含量、土壤 pH 和优势树种有关。然而,矿质土壤中 Cl(org)浓度不受所研究环境因素的显著影响,但是随着深度的增加 Cl:C 比的增加可能表明氯化有机分子的选择性保存。凋落物对 Cl 的贡献虽然显著,但与其他通量和储量相比通常较小。假设稳态条件、已知的年湿沉降和土壤中的实测储量,计算得出的总氯(无机(Cl(in))和有机)的理论平均停留时间比单独计算 Cl(in)的停留时间长 5 倍。因此,在研究陆地生态系统中氯的整体循环时,必须考虑 Cl(org)库。