Soils Group, School of Agriculture, Food and Wine and Waite Research Institute, The University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia.
Soils Group, School of Agriculture, Food and Wine and Waite Research Institute, The University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia; CSIRO, Land & Water, PMB 2, Glen Osmond SA 5064, Australia.
Chemosphere. 2015 Jan;119:99-104. doi: 10.1016/j.chemosphere.2014.05.066. Epub 2014 Jun 24.
Sorption of non-ionic organic compounds to soil is usually expressed as the carbon-normalized partition coefficient (KOC), because it is assumed that the main factor that influences the amount sorbed is the organic carbon content of the soil. However, KOC can vary by a factor of at least ten across a range of soils. We investigated two potential causes of variation in diuron KOC - organic matter-mineral interactions and organic matter chemistry - for a diverse set of 34 soils from Sri Lanka, representing a wide range of soil types. Treatment with hydrofluoric acid (HF-treatment) was used to concentrate soil organic matter. HF-treatment increased KOC for the majority of soils (average factor 2.4). We attribute this increase to the blocking of organic matter sorption sites in the whole soils by minerals. There was no significant correlation between KOC for the whole soils and KOC for the HF-treated soils, indicating that the importance of organic matter-mineral interactions varied greatly amongst these soils. There was as much variation in KOC across the HF-treated soils as there was across the whole soils, indicating that the nature of soil organic matter is also an important contributor to KOC variability. Organic matter chemistry, determined by solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, was correlated with KOC for the HF-treated soils. In particular, KOC increased with the aromatic C content (R=0.64, p=1×10(-6)), and decreased with O-alkyl C (R=-0.32, p=0.03) and alkyl C (R=-0.41, p=0.004) content.
土壤对非离子有机化合物的吸附通常用碳归一化分配系数（KOC）来表示，因为人们认为影响吸附量的主要因素是土壤的有机碳含量。然而，KOC 在一系列土壤中至少可以相差 10 倍。我们研究了两种可能导致敌草隆 KOC 变化的原因——有机质-矿物相互作用和有机质化学——选择了来自斯里兰卡的 34 种具有广泛土壤类型的土壤。我们使用氢氟酸（HF 处理）来浓缩土壤有机质。HF 处理增加了大多数土壤的 KOC（平均增加 2.4 倍）。我们将这种增加归因于矿物质对整个土壤中有机质吸附位的封锁。整个土壤的 KOC 与 HF 处理土壤的 KOC 之间没有显著相关性，这表明有机质-矿物相互作用的重要性在这些土壤中差异很大。HF 处理土壤的 KOC 变化与整个土壤的 KOC 变化一样大，这表明土壤有机质的性质也是 KOC 变异性的一个重要贡献因素。通过固态（13）C 核磁共振（NMR）光谱确定的有机质化学性质与 HF 处理土壤的 KOC 相关。特别是，KOC 随芳香族 C 含量的增加而增加（R=0.64，p=1×10(-6)），随 O-烷基 C（R=-0.32，p=0.03）和烷基 C（R=-0.41，p=0.004）含量的增加而减少。
