The use of bioretention areas is common in urban stormwater management, but their performance varies significantly depending on rainfall characteristics and design conditions. In this study, a pilot experiment using bioretention columns with different media (commercial activated carbon and river sediment-derived biochar) investigated the influence of rainfall on bioretention performance. The results indicated that the runoff volume retention ratio (R_v), which included the runoff purified and discharged at the bottom of the column, and the runoff retained in media during rainfall event, decreased significantly with increases in the rainfall event return period (p<0.05). The R_v of the activated carbon and biochar columns decreased with a 2-yr return period and then fell further with a 50-yr return period. Porous material has been shown to improve the water-holding capacity of bioretention media, but it did not result in an improved R_v under heavy rain that exceeded the 2-yr return period. With the increase of the return period from two to 50 yr, the mass removal efficiency (R_L) of total phosphorus and phosphate illustrated a clear decreasing trend in all columns. The total nitrogen, ammonia and nitrate removal did not show a clear trend with return periods because of transformations among different forms of nitrogen and similar saturation periods during the different rainfall events. The influence of the return period on chemical oxygen demand (COD) removal was related to whether the inflow COD reached maximum COD removal capacity of the bioretention media. Under a rainfall event with a specific return period, there were no significant differences in the R_L of all nitrogen species and COD among the different columns (p>0.05). The addition of adsorptive material, such as activated carbon and biochar, may not be the key factor for improving nitrogen and COD removal under heavy rain that exceeds the 2-yr return period. The bioretention performance of phosphorus removal from urban stormwater runoff could be improved by replacing or adding media with high adsorption capacity, but these improvements would not be significant under heavy rain that exceeds the 2-yr return period. The results provide some reference for evaluating bioretention performance and optimizing bioretention design in the future.

生物滞留区的使用在城市雨水管理中很常见，但其性能因降雨特征和设计条件而有显着差异。在这项研究中，使用具有不同介质（商业活性炭和河流沉积物衍生的生物炭）的生物滞留柱进行的试点实验研究了降雨对生物滞留性能的影响。结果表明，包括在柱底净化排放的径流和降雨事件期间滞留在介质中的径流的径流体积保留率（R _v）随着降雨事件重现期的增加而显着降低（p <0.05）。在[R _v活性炭和生物炭柱的数量随着 2 年的回归期而下降，然后在 50 年的回归期中进一步下降。多孔材料已被证明可以提高生物滞留介质的持水能力，但在超过 2 年重现期的大雨下，它并没有导致R _v的提高。随着重现期从 2 年增加到 50 年，质量去除效率（R _L) 的总磷和磷酸盐在所有列中都显示出明显的下降趋势。由于不同降雨事件期间不同形态氮的转化和相似的饱和期，总氮、氨和硝酸盐的去除没有表现出明显的重现期趋势。回流期对化学需氧量 (COD) 去除的影响与流入 COD 是否达到生物滞留介质的最大 COD 去除能力有关。在特定重现期的降雨事件下，R _L没有显着差异不同列中所有氮种类和 COD 的百分比 (p>0.05)。在超过 2 年重现期的大雨下，添加吸附材料，如活性炭和生物炭，可能不是提高氮和 COD 去除率的关键因素。从城市雨水径流中去除磷的生物保留性能可以通过更换或添加具有高吸附能力的介质来提高，但在超过 2 年重现期的大雨下，这些改进不会显着。研究结果为今后评价生物滞留性能和优化生物滞留设计提供了一定的参考。