Nowack Bernd, Koehler Sandra, Schulin Rainer
Institute of Terrestrial Ecology, Swiss Federal Institute of Technology (ETH), Grabenstrasse 3, CH-8952 Schlieren, Switzerland.
Environ Sci Technol. 2004 Feb 15;38(4):1133-8. doi: 10.1021/es034867j.
The technique of diffusive gradients in thin films (DGT) has been shown to be a promising tool to assess metal bioavailability in soils under laboratory conditions. In this study we used DGT to investigate the resupply kinetics of Cu and Zn under in-situ conditions in a polluted lysimeter soil and compared the results with laboratory measurements using undisturbed soil cores at defined water contents as well as homogenized soil samples. Results differed considerably between these treatments, although the same soil material was used in all experiments. A small pool of rapidly available Zn was found in the field but not in the homogenized soil. Soil solution pH and dissolved metal concentrations also varied significantly between the soil treatments. In addition, we compared the DGT-measured effective concentration with the uptake of Cu and Zn into the shoots of Lolium perenne (Ryegrass) under the same three types of conditions, i.e., field, soil cores, and homogenized soil. A close relationship was found which was not linear but could be described by a saturation-type behavior. L. perenne is a metal excluder plant, and thus, metal accumulation is limited by translocation of metals from roots to shoots. DGT predicted plant metal uptake much better than the soil solution concentration or pH. The results of this study suggest that DGT may be successfully used under field conditions to study the kinetics of metal resupply. Plant metal concentrations were not well predicted in all cases by the effective concentration CE under field conditions. Some plants took up considerably more metals than estimated by CE. Variations in metal uptake independent of their bioavailability can be caused by local variations in microsite conditions, e.g. light, temperature, water, and nutrients. To some degree, such indetermination has to be expected as an inherent feature of the system and the concept of bioavailability.
薄膜扩散梯度技术（DGT）已被证明是一种在实验室条件下评估土壤中金属生物有效性的有前景的工具。在本研究中，我们使用DGT来研究污染的蒸渗仪土壤原位条件下铜和锌的再供应动力学，并将结果与在规定含水量下使用原状土芯以及均质化土壤样品的实验室测量结果进行比较。尽管所有实验都使用了相同的土壤材料，但这些处理之间的结果差异很大。在田间发现了一小部分快速可用的锌，但在均质化土壤中未发现。土壤处理之间的土壤溶液pH值和溶解金属浓度也有显著差异。此外，我们在相同的三种条件下，即田间、土芯和均质化土壤，比较了DGT测量的有效浓度与黑麦草（Lolium perenne）地上部对铜和锌的吸收情况。发现了一种密切关系，这种关系不是线性的，但可以用饱和型行为来描述。黑麦草是一种金属排斥植物，因此，金属积累受到金属从根向地上部转运的限制。DGT预测植物对金属的吸收比土壤溶液浓度或pH值要好得多。本研究结果表明，DGT可成功用于田间条件下研究金属再供应的动力学。在田间条件下，有效浓度CE并不能在所有情况下很好地预测植物金属浓度。一些植物吸收的金属比CE估计的要多得多。微生境条件（如光照、温度、水和养分）的局部变化可能导致与生物有效性无关但与金属吸收变化有关的情况。在某种程度上，这种不确定性作为系统和生物有效性概念的固有特征是可以预期的。
