Waara Sylvia, Färm Carina
Department of Public Technology, Mälardalen University, Box 883, 721 23 Västerås, Sweden.
Environ Sci Pollut Res Int. 2008 May;15(3):205-10. doi: 10.1065/espr2007.12.463.
GOAL, SCOPE AND BACKGROUND: The potential negative impact of urban storm water on aquatic freshwater ecosystems has been demonstrated in various studies with different types of biological methods. There are a number of factors that influence the amount and bioavailability of contaminants in storm water even if it is derived from an area with a fairly homogenous land use such as a roadscape where a variation in toxicity during rain events might be expected. There are only a few previous investigations on the toxicity of highway runoff and they have not explored these issues extensively. The main objective of this study is therefore to characterize the potential toxicity of highway runoff during several rain events before it enters a detention pond in Västerås, Sweden, using laboratory bioassays with test organisms representing various functional groups in an aquatic ecosystem. The results are to be used for developing a monitoring program, including biological methods.
The storm water was sampled before the entrance to a detention pond, which receives run-off from a highway with approximately 20,000 vehicles a day. The drainage area, including the roadscape and vegetated areas, is 4.3 ha in size. Samples for toxicity tests were taken with an automatic sampler or manually during storm events. In total, the potential toxicity of 65 samples representing 15 different storm events was determined. The toxicity was assessed with 4 different test organisms; Vibrio fischeri using the Microtox comparison test, Daphnia magna using Daphtoxkit-F agna, Thamnocephalus platyurus using the ThamnotoxkitF and Lemna minor, duckweed using SS 028313.
Of the 65 samples, 58 samples were tested with DaphniatoxkitF agna, 57 samples with the Microtox comparison test, 48 samples with ThamnotoxkitF and 20 samples with Lemna minor, duckweed. None of the storm water samples were toxic. No toxicity was detected with the Lemna minor test, but in 5 of the 23 samples tested in comparison to the control a growth stimulation of 22-46% was observed. This is in accordance with the chemical analysis of the storm water, which indicated rather large concentrations of tot-N and tot-P. In addition to the growth stimulation, morphological changes were observed in all the 5 samples from the winter event that was sampled. The lack of toxicity observed in our study might be due to a lower traffic intensity (20,000 vehicles/day) at the site and the trapping of pollutants in the vegetated areas of the roadscape, resulting in much smaller loads of pollutants in the storm water than in some previous studies.
Ecotoxicological evaluations of storm water including run off from rain events from urban roadscape studies clearly reveal that toxicity may or may not be detected depending upon site, storm condition and the test organism chosen. However, storm water might not be as polluted as previously reported nor may the first flush be such a widespread phenomenon as we originally expected. In this study, there was also a good correlation between pollutant load measured and the lack of toxicity. The test organisms chosen in this study are commonly used in effluent control programs in Sweden and other countries, which makes it possible to compare the results with those from other effluents. In this study, only acute toxicity tests were used and further studies using chronic toxicity tests, assays for genotoxic compounds or in situ bioassays might reveal biological effects at this site. Furthermore, most of the samples were taken in spring, summer or fall and it is possible that winter conditions might alter the constituents in the storm water and, thus, the toxicity of the samples.
Considering the complex nature of run off from urban roadscapes, it will be virtually impossible to evaluate properly the potential hazard of particular storm water and the efficiency of a particular treatment strategy from only physical and chemical characterizations of the effluent. Therefore, despite the lack of toxicity detected in this study, it is recommended that toxicity tests or other biological methods should be included in evaluations of the effects of runoff from roadscapes.
目标、范围和背景：各种不同类型的生物学方法研究已证实城市雨水对淡水水生生态系统存在潜在负面影响。即使雨水源自土地利用相当单一的区域，如道路景观区，影响雨水中污染物含量和生物可利用性的因素仍有许多，降雨期间毒性可能会有所变化。此前关于公路径流毒性的研究较少，且未广泛探讨这些问题。因此，本研究的主要目的是利用实验室生物测定法，通过代表水生生态系统中各种功能组的测试生物，对瑞典韦斯特罗斯一个滞洪池之前几场降雨期间公路径流的潜在毒性进行表征。研究结果将用于制定监测计划，包括生物学方法。
雨水在进入一个滞洪池之前进行采样，该滞洪池接收来自一条日均车流量约20000辆的公路的径流。排水区域包括道路景观区和植被区，面积为4.3公顷。毒性测试样本在暴雨期间用自动采样器或手动采集。总共测定了代表15次不同暴雨事件的65个样本的潜在毒性。使用4种不同的测试生物评估毒性；利用Microtox比较试验的费氏弧菌、使用Daphtoxkit - F大型溞的大型溞、使用ThamnotoxkitF的扁头鲎以及使用SS 028313的浮萍。
65个样本中，58个样本用DaphtoxkitF大型溞进行测试，57个样本用Microtox比较试验，48个样本用ThamnotoxkitF，20个样本用浮萍进行测试。所有雨水样本均无毒。浮萍测试未检测到毒性，但在与对照相比测试的23个样本中有5个样本观察到生长刺激，刺激幅度为22 - 46%。这与雨水的化学分析结果一致，化学分析表明总氮和总磷浓度相当高。除了生长刺激外，在采样的冬季事件的所有5个样本中还观察到形态变化。本研究中未观察到毒性可能是由于该地点交通强度较低（日均20000辆车）以及道路景观植被区对污染物的截留作用，导致雨水中污染物负荷比之前的一些研究小得多。
对包括城市道路景观降雨径流在内的雨水进行生态毒理学评估清楚地表明，根据地点、暴雨条件和所选测试生物的不同，可能检测到毒性，也可能检测不到。然而，雨水可能不像之前报道的那样污染严重，而且首次冲刷现象可能也不像我们最初预期的那样普遍。在本研究中，测量的污染物负荷与无毒之间也存在良好的相关性。本研究中选择的测试生物在瑞典和其他国家的废水控制项目中常用，这使得能够将结果与其他废水的结果进行比较。本研究仅使用了急性毒性测试，使用慢性毒性测试、遗传毒性化合物检测或原位生物测定的进一步研究可能会揭示该地点的生物效应。此外，大多数样本是在春季、夏季或秋季采集的，冬季条件可能会改变雨水中的成分，从而改变样本的毒性。
考虑到城市道路景观径流的复杂性，仅从废水的物理和化学特征来正确评估特定雨水的潜在危害以及特定处理策略的效率几乎是不可能的。因此，尽管本研究未检测到毒性，但建议在评估道路景观径流的影响时应包括毒性测试或其他生物学方法。
