绿色屋面降雨径流水质及消减污染负荷研究

2011年5月至11月对12场降雨时段的屋面径流和干湿沉降进行采样监测,比较了屋面径流(绿色屋面和沥青屋面)、干湿总沉降和降雨中污染物的浓度和污染负荷,并运用多元统计方法分析了降雨特征对绿色屋面径流水质的影响。结果表明,从径流水质层面上分析,绿色屋面是总悬浮物(TSS)的汇,对p H值有较好的中和作用,对于总磷(TP)、溶解态铜(DCu)和溶解态锌(DZn)是非源非汇,是电导率(EC)、总氮(TN)、氨态氮(NH+4-N)、硝态氮(NO-3-N)、化学需氧量(COD)、5日生化需氧量(BOD5)和溶解态铅(DPb)的源;从污染负荷的角度分析,绿色屋面是NH+4-N、TSS和BOD5的汇,对于TN、DPb、DCu、DZn、TP和COD是非源非汇,是NO-3-N的源;与控制屋面相比,绿色屋面可以消减TSS、TP、BOD5、COD、NH+4-N、DZn和DPb的污染负荷,分别消减了90.53%、49.38%、41.31%、36.48%、35.45%、28.27%和14.20%;但是增加了NO-3-N和TN的污染负荷,分别增加了821.02%和275.48%;绿色屋面径流污染物的浓度与降雨量、降雨历时和降雨强度呈负相关关系,而与降雨间隔呈正相关关系。研究结果为绿色屋面的科学设计及正确评价绿色屋面对径流水质的影响提供依据。

Research on green roof in water quality of rainfall runoff and reduction of pollution load

With the rapid urbanization and continued improve to control urban point source pollution in China, the ratio of urban surface runoff accounted for pollution load of receiving water will be raised increasingly and pose a serious threat to urban water body. "Green" roofs, also referred to as vegetated or ecology roofs, are of the important technologies for controlling urban nonpoint source pollution, which has been taken as an important component of technical system in many advanced concepts for the management of urban stormwater runoff. Green roof has several beneficial effects in an urban setting, such as their ability to retain and detain roof stormwater runoff, reduce urban heat islands, improve air quality, provide wildlife habitats, and their esthetic value. However, there is a very important aspect that has often been overlooked in previous studies is the quality of the runoff water from green roofs. Therefore, it is very important to investigate runoff water quality from green roofs for its popularization and application. In the paper, we investigated water quality of storm runoff from green roof, asphalt roof (control roof), dry-wet deposition and rainfall from May to December, 2011, and calculated the pollution load of them, and analyzed the effect of rainfall characteristics on runoff water quality using multivariate statistical analysis. Compared the water quality from green roof, asphalt roof (control roof), dry-wet deposition and rainfall, we found that the green roof was a sink of total suspended solids (TSS), because the average TSS concentration of the green roof (20.42 mg/L) was significantly lower than on the asphalt roof (67.04 mg/L) and was also lower than that of the dry-wet deposition (36.53 mg/L) samples. The green roof can neutralize the pH from 5.61 to 6.84. The green roof is non-source and non-sink for total phosphorus (TP), dissolved copper (DCu) and dissolved zinc (DZn); conversely, the green roof was a source of electrical conductivity (EC), total nitrogen (TN), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), chemical oxygen demand (COD), biochemical oxygen demand after 5 days (BOD₅) and dissolved lead (DPb), because the average concentration of there parameters of green roof was significantly higher than of the asphalt roof, dry-wet deposition and rainfall. However, considered about the pollution load from green roof, asphalt roof (control roof) and dry-wet deposition, we noticed that the green roof was a sink of NH₄⁺-N, TSS and BOD₅, the green roof is non-source and non-sink for TN, DPb, DCu, DZn, TP and COD, conversely, the green roof was a source of NO₃^--N. Compared the pollution load between green roof and asphalt roof (control roof), 90.53% of TSS, 49.38% of TP, 41.31% of BOD₅, 36.48% of COD, 35.45% of NH₄⁺-N, 28.27% of DZn and 14.20% of DPb could be abated, however, 821.02% of NO₃^--N and 275.48% TN could be added; The concentration of the pollutants of green roof runoff were negatively correlated with precipitation, rainfall duration and rainfall intensity, however, there was positive correlation with the antecedent dry weather period. The results can provide a basis for design of the green roof and scientific assessment the effect of the green roof to runoff water quality.