木屑生物炭在雨水径流中的氮磷淋出和吸附特性

现阶段生物滞留系统的填料存在氮磷营养素淋出及吸附净化效果不稳定的问题.为评估木屑生物炭作为生物滞留系统过滤层填料的可行性，选用传统填料（椰糠、堆肥、陶粒和火山石）作为对比材料，通过理化性质测试、批量淋洗实验、等温吸附和解吸实验，研究木屑生物炭的基本性质、淋出特性和吸附特性，探究木屑生物炭对生物滞留系统的优化效果与改良机制.结果表明，经高温热解生成的木屑生物炭具有疏松和多孔的特性，饱和含水率为195.65%，持水效果好；热解后木屑生物炭表面的氮磷元素转换为稳定的化合物，在批量淋洗实验中其氮素淋出量低、淋出速度快，磷素淋出滞缓但在人造雨水径流的淋洗中保持线型负值增长，吸附效果稳定；在典型雨水径流浓度（2mg·L^-1的NH₄⁺及2mg·L^-1的PO₄^3-）下，木屑生物炭可吸附34.6mg·kg^-1的NH₄⁺和59.5mg·kg^-1的PO₄^3-，具有突出的综合吸附能力；NH₄⁺及PO₄^3-吸附平衡后的木屑生物炭在去离子水中的平均解吸率为21.23%和17.43%，吸附效果稳定.综上所述，木屑生物炭的施用可解决填料营养盐过剩淋出的问题，且具有较好的氮磷吸附效果，可用作生物滞留系统的填料解决雨水径流污染问题.

Nitrogen and Phosphorus Leaching Characteristics and Adsorption Properties of Hardwood Biochar in Stormwater Runoff

At present, the fillers used in bioremanent systems are limited by problems such as unstable leaching and adsorption of nitrogen and phosphorus. To assess the feasibility of using hardwood biochar as a filter filler material in bioretention systems, it was compared to traditional filter filler materials, namely coconut chaff, compost, ceramsite, and volcanic stone. Experiments and tests were conducted to study the physico-chemical properties, leaching, and adsorption characteristics of hardwood biochar, and to explore the optimizing effect and mechanism of hardwood biochar in bioretention systems. Hardwood biochar created through high temperature pyrolysis was found to be porous and loose, with a saturated moisture content of 195.65% and good water retention capacity. After pyrolysis, the nitrogen and phosphorus elements on the hardwood biochar surface were converted into stable compounds. In a batch leaching experiment, the quantity of leached nitrogen was low, and the leaching speed was fast; phosphorus leaching was slow, although the linear negative value increased during artificial rainwater runoff leaching, and the adsorption effect was stable. When exposed to typical nitrogen and phosphorous concentrations in rainwater runoff (2 mg·L^-1 of NH₄⁺ and 2 mg·L^-1 of PO₄^3-), hardwood biochar adsorbed 34.6 mg·kg^-1 NH₄⁺ and 59.5 mg·kg^-1 PO₄^3-, showing outstanding comprehensive adsorption capacity. After reaching adsorption equilibrium, the average desorption rates of the hardwood biochar in deionized water were 21.23% and 17.43%, proving that the adsorption effect was stable. In conclusion, the application of hardwood biochar can mitigate excessive leaching of nutrients from fillers, as it has a better adsorption capacity for nitrogen and phosphorus. Therefore, hardwood biochar can be used as the filler material in bioretention systems, to reduce pollution associated with rainwater runoff.