基质有机质类型对干植草沟去除多环芳烃的影响

Effects of types of substrate organic matters on removal of PAHs by dry grass swales

基质层是影响干植草沟对道路径流净化效果的决定因素。为此,搭建6个不同基质层组成的干植草沟模拟柱,以路面径流中代表性多环芳烃(PAHs)配制的人工径流作为进水,考察各模拟柱去除PAHs的运行效果并进行质量平衡核算,评价外源有机质的存在及类型对PAHs去除效果及其归宿的影响。结果表明:各模拟柱对萘(NaP)、菲(PhA)和荧蒽(FlA)的平均去除率分别为69.0%~87.5%、33.7%~72.9%和90.8%~96.8%,浅基质层相对不利于以溶解态为主的低分子质量(LMW)PAHs的去除;在基质中添加外源有机质有利于提高进水中PAHs的净化效果;在5个月的运行周期内,随着PAHs分子质量的增加,PAHs在基质中的积累越明显,生物降解的程度也相应降低,在接近实际使用的运行条件下,不同基质模拟柱中NaP、PhA和FlA的微生物降解率分别为62.1%~76.6%、32.2%~42.9%和17.1%~36.6%;生物炭和木屑有效地提高了PAHs的降解率,可作为良好的外源有机质材料在LID设施的实际应用中发挥作用,后者更具经济性。

Substrate layer is the key factor determining the purification efficiency of road runoff by dry grass swales.Six dry grass swale columns with different substrate components were constructed for simulation,and the artificial runoff containing representative polycyclic aromatic hydrocarbons(PAHs)was used as influent water.The performance of different simulation columns for the removal of PAHs was analyzed,and the mass balance was performed,in order to evaluate the effects of the presence and types of exogenous organic matters in substrates on the removal efficiency of PAHs and their fate.Results show that the average removal rates of NaP,PhA,and FlA were 69.0%-87.5%,33.7%-72.9%,and 90.8%-96.8%,respectively.The dry grass swale with a shallow substrate layer was less conducive to the removal of low molecular weight(LMW)PAHs.The addition of exogenous organic matters in substrates was beneficial to improve the removal efficiencies of influent PAHs.During the five-month operation period,with the increase in the molecular weight of PAHs,the accumulation of PAHs in substrates increased and the degree of biodegradation was correspondingly decreased.Under the operation conditions close to the actual situations,the microbial degradation rates of NaP,PhA,and FlA were 62.1%-76.6%,32.2%-42.9%,and 17.1%-36.6%,respectively.Biochar and woodchips could effectively improve the degradation rates of PAHs,and both of them can be used as exogenous organic materials in practical application of low impact development(LID)facilities,while woodchips are more economical.