AgResearch, Lincoln Research Centre, Private Bag, Christchurch, 4749, New Zealand.
AgResearch, Invermay Agricultural Centre, Private Bag, Mosgiel, 50034, New Zealand.
Environ Sci Pollut Res Int. 2017 Oct;24(30):24046-24053. doi: 10.1007/s11356-017-0117-9. Epub 2017 Sep 16.
Cadmium (Cd) transport in overland flow from agricultural soils is potentially important when trying to predict future soil Cd concentrations, but at present there is little information on the magnitude of loss from this pathway. This study measured Cd concentrations and fluxes in overland flow from a catchment where cattle winter-grazed a forage crop (kale) (Brassica oleracea) in year one and measurements continued in year two when the catchment was returned to pasture and grazed by sheep. Flow-weighted mean concentrations (FWMC) of total, particulate and dissolved Cd in overland flow events from the forage crop were 0.49, 0.41 and 0.08 μg L, respectively. In contrast, no dissolved Cd was detected in overland flow from pasture, with a FWMC of total Cd of 0.09 μg L. In line with the Cd concentrations, total Cd fluxes were greater from the forage crop (0.06 g Cd ha year) than from pasture (0.04 g Cd ha year). Cadmium losses in overland flow were relatively minor compared with those reported for other pathways such as plant uptake or subsurface flow. Further, compared to the amount of Cd that is currently added to soil in a maintenance application of phosphate fertiliser (30 kg P ha year) which is on average 5.5 g Cd ha, Cd losses in overland flow represented < 1% of inputs. Measurement of Cd losses in overland flow should be undertaken at other sites to confirm the low Cd losses found in this study, along with the distribution between dissolved and particulate fractions.
农田地表径流中的镉（Cd）迁移对于预测未来土壤 Cd 浓度具有重要意义，但目前关于该途径损失程度的信息很少。本研究测量了一个集水区中地表径流中的 Cd 浓度和通量，该集水区在第一年冬季放牧牛群采食饲草作物（羽衣甘蓝）（Brassica oleracea），第二年则将集水区恢复为牧场并放牧绵羊。饲草作物地表径流中总 Cd、颗粒态 Cd 和溶解态 Cd 的流量加权平均浓度（FWMC）分别为 0.49、0.41 和 0.08μg/L。相比之下，牧场地表径流中未检测到溶解态 Cd，总 Cd 的 FWMC 为 0.09μg/L。与 Cd 浓度一致，饲草作物的总 Cd 通量（0.06g Cd ha 年）大于牧场（0.04g Cd ha 年）。与植物吸收或地下水流等其他途径相比，地表径流中的 Cd 损失相对较小。此外，与目前在磷酸盐肥料维持施用中添加到土壤中的 Cd 量（30kg P ha 年）相比，平均 5.5g Cd ha，地表径流中的 Cd 损失仅占输入量的<1%。应该在其他地点测量地表径流中的 Cd 损失，以确认本研究中发现的低 Cd 损失，并确定溶解态和颗粒态之间的分布。
