某停车场生物滞留系统介质累积重金属释放规律

The Release Characteristic of Heavy Metals in Bioretention of a Parking Lot

采集某停车场生物滞留系统中表层和10cm深处介质,考察Cu、Zn、Cd、Pb四种重金属释放规律,探究介质有机质、pH值对重金属释放的影响,采用Tessier形态分类提取法分析释放前后介质累积重金属赋存形态变化。结果表明,停车场生物滞留系统表层和10cm处介质重金属释放浓度大小顺序均为Zn>Pb>Cu>Cd,且表层介质重金属释放量均高于10cm深处介质;介质重金属释放量与有机质释放量呈正相关,有机质释放量越高,介质所释放的各种重金属浓度也越高;介质重金属释放量与介质pH值呈负相关,pH值越大,重金属释放量越小;介质释放的重金属主要是其积蓄的有机结合态和铁锰氧化物结合态,释放后Cu、Zn、Pb和Cd的有机结合态占比分别比释放前平均减少了2.81%、5.11%、11.03%和12.97%,铁锰氧化物结合态则平均减少了2.28%、9.04%、0.14%和6.82%。

To determine the release characteristics of heavy metals,the medium filled in the bioretention system were sampled at the surface and 10cm depth in a parking lot.The correlations between pH value,organic matter content and heavy metals release amounts were also analyzed.The chemical fractions of accumulated heavy metals in the medium were compared before and after the release process.The results showed that the release amounts of heavy metals in the surface medium of the bioretention system was higher than that in 10cm depth,both following the order of Zn>Pb>Cu>Cd.The release of heavy metals from the medium was positively correlated with the release of organic matter,the higher the release of organic matter,the higher the concentration of each heavy metal released from the medium;the release of heavy metals from the medium was negatively correlated with pH value.The heavy metals released from the medium were mainly in their accumulated organic-bound state and Fe-Mn oxide-bound state.Compared to the proportion before release,Cu,Zn,Pb and Cd in the organic-bound state after release averagely decreased by 2.81%,5.11%,11.03%and 12.97%,and the Fe-Mn oxide-bound state averagely decreased by 2.28%,9.04%,0.14%and 6.82%,respectively.