Department of Civil and Environmental Engineering, University of California, Los Angeles, USA.
Department of Earth and Environmental Science, Temple University, Philadelphia, USA.
Sci Total Environ. 2020 Sep 15;735:139180. doi: 10.1016/j.scitotenv.2020.139180. Epub 2020 May 20.
Amending roadside soil with adsorbents such as biochar can help remove pollutants from road runoff. To maintain soil stability, the roadside soil requires compaction. However, it is unknown how compaction conditions affect the capacity of biochar-augmented roadside biofilters to infiltrate stormwater and remove pollutants. This work examines the effect of compaction conditions on the release of biochar particles disintegrated during compaction, and the change in their capacity to infiltrate stormwater and remove E. coli. The net loss of biochar particles by mobilization with stormwater was insignificant compared to the biochar remained in the filters. The initial release of biochar particles in wet-compacted biochar columns was greater than that in dry-compacted biochar. The results revealed that compaction can affect the release of biochar particles in a series of three-step processes: generation of particles by disintegration of large biochar under compaction, diffusion of particles deposited near grain walls to bulk pore water, and transport and retention of particles in constricted pore paths based on pore water connectivity. Under similar conditions, compost columns released more particles than biochar columns, suggesting biochar is more stable than compost under compaction. E. coli removal in wet-compacted columns was greater than removal in dry-compacted columns, owing to greater pore path connectivity in wet-compacted columns. These results indicate that addition of moisture during compaction can increase contaminant removal, initial particle release, and infiltration capacity of biochar-augmented sand filters for road runoff treatment. The results would help develop design guidelines for roadside stormwater treatment systems that require compaction of filter media.
用生物炭等吸附剂改良路边土壤可以帮助去除道路径流中的污染物。为了保持土壤稳定性，需要对路边土壤进行压实。然而，压实条件如何影响增强型路边生物过滤器渗透雨水和去除污染物的能力尚不清楚。本研究考察了压实条件对压实过程中生物炭颗粒解体释放的影响，以及它们渗透雨水和去除大肠杆菌能力的变化。与过滤器中残留的生物炭相比，生物炭颗粒在雨水的迁移作用下的净损失微不足道。在湿压实的生物炭柱中，生物炭颗粒的初始释放量大于干压实的生物炭。结果表明，压实可以通过三个步骤过程影响生物炭颗粒的释放：压实过程中大块生物炭解体产生颗粒、壁附近沉积的颗粒扩散到体相孔隙水中、以及基于孔隙水连通性的颗粒在狭窄孔隙路径中的迁移和保留。在相似条件下，堆肥柱释放的颗粒多于生物炭柱，这表明生物炭在压实条件下比堆肥更稳定。由于湿压实柱中孔隙路径连通性更大，因此湿压实柱中大肠杆菌的去除率大于干压实柱。这些结果表明，在压实过程中添加水分可以提高生物炭增强砂过滤器处理道路径流的污染物去除率、初始颗粒释放率和渗透能力。这些结果将有助于为需要压实过滤介质的路边雨水处理系统制定设计指南。
