Sheppard M I, Sheppard S C, Amiro B D
Environmental Science Branch, AECL Research, Whiteshell Laboratories, Pinawa, Manitoba.
Health Phys. 1991 Oct;61(4):481-92. doi: 10.1097/00004032-199110000-00003.
Quantifying and understanding the mobility of 14C and organic pollutants in soils is important, especially in the context of underground waste disposal. We studied migration of 14C applied as NaHCO3 (14C-CO3) and as 2,2',5,5' tetrachlorobiphenyl (14C-PCB) in carbonated, high-organic-matter-content and acidic, low-organic-matter-content undisturbed soil cores. The mobility of 14C-PCB depends on the profile distribution and amount of soil organic matter, whereas the mobility of 14C-CO3 depends primarily on the soil carbonate content. The solid/liquid partition coefficients (Kd) for 14C-CO3 were 6.7 and 1.2 mL g-1 for the two soils, respectively. For the 14C-PCB, the corresponding Kd values were 49 and 22 mL g-1. Plant/soil concentration ratios (CR) for inorganic 14C have previously been derived using overly conservative assumptions. Using plants grown in outdoor lysimeters, CR values for 14C-CP3 of 0.7 and 1.3, on a dry-weight basis, were measured for the two soils. These values are about 25-fold lower than the currently used values. The corresponding CR values for 14C-PCB were 0.014 and 0.088. For both 14C sources, there was evidence of atmospheric transfer from the soil to the plants. This was especially important for 14C-CO3, where it may have been dominant. Detailed modelling of 14C transport from underground waste disposal should include volatilization as a loss process from soil as well as a source for plants.
量化并了解土壤中¹⁴C和有机污染物的迁移性很重要，特别是在地下废物处置的背景下。我们研究了以碳酸氢钠（¹⁴C-CO₃）和2,2',5,5'-四氯联苯（¹⁴C-PCB）形式施加的¹⁴C在碳酸化、高有机质含量以及酸性、低有机质含量的未扰动土壤芯中的迁移情况。¹⁴C-PCB的迁移性取决于土壤有机质的剖面分布和含量，而¹⁴C-CO₃的迁移性主要取决于土壤碳酸盐含量。两种土壤中¹⁴C-CO₃的固/液分配系数（Kd）分别为6.7和1.2 mL g⁻¹。对于¹⁴C-PCB，相应的Kd值为49和22 mL g⁻¹。此前推导无机¹⁴C的植物/土壤浓度比（CR）时使用了过于保守的假设。利用在室外蒸渗仪中生长的植物，测得两种土壤中¹⁴C-CP3以干重计的CR值分别为0.7和1.3。这些值比目前使用的值低约25倍。¹⁴C-PCB的相应CR值为0.014和0.088。对于两种¹⁴C源，都有证据表明存在从土壤到植物的大气转移。这对¹⁴C-CO₃尤为重要，在这种情况下大气转移可能占主导。对地下废物处置中¹⁴C迁移的详细建模应包括挥发这一土壤损失过程以及植物的来源。
