Division of Soil and Water Management, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20-bus 2459, 3001 Heverlee, Belgium.
Environ Sci Technol. 2011 Apr 1;45(7):2584-90. doi: 10.1021/es103532a. Epub 2011 Mar 15.
Dissolved organic matter (DOM) in surface waters affects the fate and environmental effects of trace metals. We measured variability in the Cd, Cu, Ni, and Zn affinity of 23 DOM samples isolated by reverse osmosis from freshwaters in natural, agricultural, and urban areas. Affinities at uniform pH and ionic composition were assayed at low, environmentally relevant free Cd, Cu, Ni, and Zn activities. The C-normalized metal binding of DOM varied 4-fold (Cu) or about 10-fold (Cd, Ni, Zn) among samples. The dissolved organic carbon concentration ranged only 9-fold in the waters, illustrating that DOM quality is an equally important parameter for metal complexation as DOM quantity. The UV-absorbance of DOM explained metal affinity only for waters receiving few urban inputs, indicating that in those waters, aromatic humic substances are the dominant metal chelators. Larger metal affinities were found for DOM from waters with urban inputs. Aminopolycarboxylate ligands (mainly EDTA) were detected at concentrations up to 0.14 μM and partly explained the larger metal affinity. Nickel concentrations in these surface waters are strongly related to EDTA concentrations (R2=0.96) and this is underpinned by speciation calculations. It is concluded that metal complexation in waters with anthropogenic discharges is larger than that estimated with models that only take into account binding on humic substances.
溶解有机质 (DOM) 会影响痕量金属在地表水中的归宿和环境效应。我们测量了从自然、农业和城市地区淡水源中反渗透分离的 23 种 DOM 样本对 Cd、Cu、Ni 和 Zn 的亲和力的可变性。在均匀 pH 值和离子组成下，以低浓度、环境相关的游离 Cd、Cu、Ni 和 Zn 活性进行了亲和力测试。DOM 的 C 归一化金属结合能力在样本之间变化了 4 倍（Cu）或约 10 倍（Cd、Ni、Zn）。水中的溶解有机碳浓度仅相差 9 倍，表明 DOM 质量与 DOM 数量一样，是金属络合的一个同等重要的参数。DOM 的紫外吸光度仅能解释受城市输入影响较小的水域中的金属亲和力，这表明在这些水域中，芳香族腐殖质是主要的金属螯合剂。来自受城市输入影响的水域的 DOM 具有更大的金属亲和力。多氨基多羧酸配体（主要是 EDTA）的浓度高达 0.14 μM，部分解释了更大的金属亲和力。这些地表水中的镍浓度与 EDTA 浓度密切相关（R2=0.96），这是通过形态计算得到的。结论是，考虑到仅与腐殖质结合的模型，人为排放水域中的金属络合作用大于模型估计的结果。
