Franklin Hannah M, Doederer Katrin, Neale Peta A, Hayton Joshua B, Fisher Paul, Maxwell Paul, Carroll Anthony R, Burford Michele A, Leusch Frederic D L
Australian Rivers Institute, Griffith University, Nathan, 4111, Brisbane, Queensland, Australia.
The University of Queensland, Advanced Water Management Centre, Gehrmann Building, St. Lucia, Brisbane, QLD, 4072, Australia.
Environ Pollut. 2021 Aug 15;283:117232. doi: 10.1016/j.envpol.2021.117232. Epub 2021 May 7.
Restoring woody vegetation to riparian zones helps to protect waterways from excessive sediment and nutrient inputs. However, the associated leaf litter can be a major source of dissolved organic matter (DOM) leached into surface waters. DOM can lead to the formation of disinfection by-products (DBPs) during drinking water treatment. This study investigated the DBPs formed during chlorination of DOM leached from leaf litter and assessed the potential toxicity of DBPs generated. We compared the leachate of two native Australian riparian trees, Casuarina cunninghamiana and Eucalyptus tereticornis, and a reservoir water source from a catchment dominated by Eucalyptus species. Leachates were diluted to dissolved organic carbon concentrations equivalent to the reservoir (~9 mg L). E. tereticornis leachates produced more trihalomethanes (THMs), haloacetic acids (HAAs), and haloketones after chlorination, while C. cunninghamiana produced more chloral hydrate and haloacetonitriles. Leachate from both species produced less THMs and more HAAs per mole of carbon than reservoir water. This may be because reservoir water had more aromatic, humic characteristics while leaf leachates had relatively more protein-like components. Using in vitro bioassays to test the mixture effects of all chemicals, chlorinated E. tereticornis leachate induced oxidative stress in HepG2 liver cells and bacterial toxicity more frequently and at lower concentrations than C. cunninghamiana and reservoir water. Overall, this study has shown that the DOM leached from litter of these species has the potential to generate DBPs and each species has a unique DBP profile with differing bioassay responses. E. tereticornis may pose a relatively greater risk to drinking water than C. cunninghamiana as it showed greater toxicity in bioassays. This implies tree species should be considered when planning riparian zones to ensure the benefits of vegetation to waterways are not offset by unintended increased DBP production and associated toxicity following chlorination at downstream drinking water intakes.
在河岸带恢复木本植被有助于保护水道免受过多沉积物和养分输入的影响。然而，相关的落叶可能是溶解有机物（DOM）渗入地表水的主要来源。DOM在饮用水处理过程中会导致消毒副产物（DBPs）的形成。本研究调查了落叶沥出的DOM氯化过程中形成的DBPs，并评估了所产生DBPs的潜在毒性。我们比较了两种澳大利亚本土河岸树木——细叶短穗柳（Casuarina cunninghamiana）和柳叶桉（Eucalyptus tereticornis）的沥出液，以及一个以桉属物种为主的集水区的水库水源水。将沥出液稀释至溶解有机碳浓度与水库水相当（约9毫克/升）。柳叶桉沥出液氯化后产生的三卤甲烷（THMs）、卤乙酸（HAAs）和卤代酮更多，而细叶短穗柳产生的水合氯醛和卤乙腈更多。两种树种的沥出液每摩尔碳产生的THMs较少，HAAs较多于水库水。这可能是因为水库水具有更多芳香、腐殖特性，而树叶沥出液具有相对更多类似蛋白质的成分。使用体外生物测定法测试所有化学物质的混合效应时，氯化后的柳叶桉沥出液比细叶短穗柳和水库水更频繁且在更低浓度下诱导HepG2肝细胞中的氧化应激和细菌毒性。总体而言，本研究表明，这些树种落叶沥出的DOM有产生DBPs的潜力，且每个树种都有独特的DBP谱，生物测定反应不同。柳叶桉对饮用水可能构成比细叶短穗柳相对更大的风险，因为它在生物测定中表现出更大的毒性。这意味着在规划河岸带时应考虑树种，以确保植被对水道的益处不会被下游饮用水取水口氯化后意外增加的DBP产量和相关毒性所抵消。
