Iowa Geological Survey, University of Iowa, Iowa City, IA, USA.
Iowa Geological Survey, University of Iowa, Iowa City, IA, USA.
Sci Total Environ. 2019 Mar 20;657:1432-1440. doi: 10.1016/j.scitotenv.2018.12.113. Epub 2018 Dec 11.
Roadside ditches are an integral component to the >6.3 million km of roadsides in the U.S. and act as drainageways for millions of hectares of watershed runoff. Our study of six roadside ditches in Lime Creek watershed characterized soil nutrients and heavy metal patterns as well as quantified the physical and hydrological properties of ditch soils. At all ditch sites, we identified significant sedimentation of silt-sized particles, total nitrogen, and soil carbon in shallow roadside ditch soils. A post-settlement surface soil horizon significantly higher in silt content was observed compared to the underlying subsoil and parent material. Although accumulation of several heavy metals was measured in ditch soils, significant variability was not observed within the ditch environment. Most of the heavy metal concentrations were found to be either similar to or lower than state-wide averages. Higher levels of calcium near the roads were likely due to annual use of road deicers. Overall, we estimated that 42 Mg/ha of total carbon and 5 Mg/ha of total nitrogen are being stored in agricultural ditch soils, which is similar to that of surrounding agricultural land in terms of total carbon storage, but much higher than estimates of total nitrogen storage. Our study of six roadside ditches in an eastern Iowa watershed documented the soil chemistry, morphology, and sediment accumulation that occurred since ditch construction. Further research is needed to develop a better understanding of how the soil and water conditions in the ditches related to the watershed areas that feed them.
美国有超过 630 万公里的道路，路边沟渠是其不可或缺的组成部分，它们充当了数百万公顷集水区径流水的排水通道。我们对 Lime Creek 流域的 6 个路边沟渠进行了研究，描绘了土壤养分和重金属模式，并量化了沟渠土壤的物理和水文特性。在所有沟渠地点，我们发现浅路边沟渠土壤中存在显著的泥沙粒径、总氮和土壤碳的沉积。与底层底土和母质相比，后沉降的表土具有显著更高的泥沙含量。尽管在沟渠土壤中测量到了几种重金属的积累，但在沟渠环境中没有观察到显著的变化。大多数重金属浓度与州内平均值相似或更低。道路附近较高的钙水平可能是由于每年使用道路除冰剂所致。总体而言，我们估计在农业沟渠土壤中储存了 42 Mg/ha 的总碳和 5 Mg/ha 的总氮，这与周围农业土地的总碳储存相似，但远高于总氮储存的估计。我们对爱荷华州东部流域的 6 个路边沟渠进行的研究记录了自沟渠建设以来发生的土壤化学、形态和沉积物积累。需要进一步研究以更好地了解沟渠中的土壤和水条件与为其提供养分的流域区域之间的关系。
