Department of Civil and Environmental Engineering, University of California, Los Angeles, USA.
Department of Earth and Environmental Science, Temple University, Philadelphia, USA.
Water Res. 2019 Nov 15;165:115008. doi: 10.1016/j.watres.2019.115008. Epub 2019 Aug 20.
Stormwater biofilters have been increasingly used to mitigate the impact of climate change on the export of contaminants including nitrate to water bodies. Yet, their performance is rarely tested under high-intensity rainfall events, which are predicted to occur more frequently under climate change scenarios. We examined the potential of biochar to improve the resilience of woodchip biofilters under simulated high-intensity rainfall events and linked denitrification to biochar-mediated changes in hydrological (physical), chemical, and biological properties of woodchip biofilters. Results showed that nitrate removal capacity of woodchip biofilters decreased with increases in rainfall intensity or duration and decreases in antecedent drying time. However, adding biochar to woodchips significantly decreased the exhaustion rate of woodchips, only when the hydraulic residence time (HRT) was less than 5 h. At longer HRT (>5 h), the benefits of biochar became less apparent. We attributed the improved denitrification during high nitrate loading to biochar's ability to decrease dissolved oxygen in pore water and increase water holding capacity and retention of dissolved organic carbon and nitrate-all of which could increase nitrate utilization. Biochar increased the net microbial biomass but did not affect the relative abundance of denitrifying genes, which indicates that a shift in microbial biomass could not fully explain the observed increase in nitrate removal in biochar-augmented woodchip biofilters. Overall, the results showed that biochar could increase the resiliency of woodchip biofilters for denitrification in high-intensity rainfall events, a worst-case scenario, thereby mitigating the water quality degradation during climate change.
雨水生物过滤器越来越多地被用于减轻气候变化对包括硝酸盐在内的污染物向水体输出的影响。然而，它们的性能很少在高强度降雨事件下进行测试，而气候变化情景预计会更频繁地发生高强度降雨事件。我们研究了生物炭在模拟高强度降雨事件下提高木屑生物过滤器弹性的潜力，并将反硝化作用与生物炭介导的木屑生物过滤器水文（物理）、化学和生物特性变化联系起来。结果表明，随着降雨强度或持续时间的增加，以及前期干燥时间的减少，木屑生物过滤器的硝酸盐去除能力下降。然而，当水力停留时间（HRT）小于 5 小时时，向木屑中添加生物炭会显著降低木屑的枯竭率。在较长的 HRT（>5 小时）下，生物炭的益处变得不那么明显。我们将高硝酸盐负荷下反硝化作用的改善归因于生物炭降低孔水中溶解氧、增加持水能力和保留溶解有机碳和硝酸盐的能力，所有这些都可以增加硝酸盐的利用。生物炭增加了净微生物生物量，但不影响反硝化基因的相对丰度，这表明微生物生物量的变化不能完全解释在生物炭增强的木屑生物过滤器中观察到的硝酸盐去除增加。总的来说，结果表明，生物炭可以提高木屑生物过滤器在高强度降雨事件中的反硝化弹性，这是一种最坏的情况，从而减轻气候变化期间水质恶化。
