Humic Substance Effect on Photochemical Fate of PAHs

多环芳烃（PAHs）在水体中的光解受自然沃茨中人类物质（HS）的影响。一方面，由于有色HS作为光过滤器的竞争吸收，直接光解可以被抑制。这可能会导致在HS的存在下的光解速率降低相比，在纯水中的反应。另一方面，紫外线也会引起溶解有机碳（包括腐殖酸和富里酸）和多环芳烃的各种光化学变化，并导致活性氧的产生，天然水环境中的多环芳烃可能与纯水中的多环芳烃存在显着差异。在这项拟议的研究中，我们将确定选定的多环芳烃在自然沃茨以及在缓冲蒸馏水与HS的光降解动力学。HA和FA材料将从商业来源和自行提取来源获得。将确定HS对候选化合物的持久性、毒性和降解途径的影响。本研究将利用微生物生物活性导向的化学分馏方法，通过对多环芳烃光降解产物的鉴定，探讨HA和FA存在下多环芳烃的光降解机理。本研究还将探讨pH值对HS与PAHs相互作用的影响。具体而言，我们将：（1）采用Mutatox试验、Microtox试验和其他技术，如呼吸测定法和微生物对葡萄糖和胸苷的异养摄取，在存在和不存在HA和FA的情况下，测定选定的多环芳烃的急性遗传毒性和生态毒性;（2）比较存在和不存在HA和FA的情况下，多环芳烃光产物的主要种类;（3）确定HS对核黄素（一种环境友好的光敏剂）对多环芳烃的生物修复效率的影响;（4）模拟毒性/抑制指数值的依赖性（例如，（5）研究了pH值对HS对多环芳烃光致毒性的影响。本研究假设：（1）腐殖物质可以减少地表沃茨中太阳辐射的有效性，因此，天然水环境中多环芳烃的光致毒性将低于纯净水溶液中的多环芳烃;（2）通过适当控制pH值，可以成功实施多环芳烃污染沃茨的修复。本项目的具体目标是：1）通过微生物生物测定法研究HS对天然水环境中多环芳烃光致生态毒性和遗传毒性的影响：2）研究腐殖酸对候选多环芳烃持久性和降解途径的影响;（3）研究HS对敏化光解处理多环芳烃污染沃茨的效率和健康影响的影响;（4）研究pH对HS影响多环芳烃光致毒性的影响。长期目标是：（1）提高JSU在环境健康领域的研究能力;（2）完成MBRS计划的使命，研究多环芳烃危害人类健康的可能机制。

The aquatic photolysis of polycyclic aromatic hydrocarbons (PAHs) can be influenced in several ways by the human substances (HS) present in natural waters. On one hand, direct photolysis can be inhibited because of the competitive absorption by colored HS as a light filter. This may lead to decrease in the photolysis rates in the presence of HS compared to the reactions in pure water. On the other hand, UV also induces a variety of photochemical changes in dissolved organic carbons (including humic acid, HA and fulvic acid, FA) and PAHs and lead to production of reactive oxygen species and PAHs in natural aquatic environments may differ significantly from those present in pure water. In this proposed research, we will determine the kinetics of photodegradation of selected PAHs in natural waters as well as in buffered distilled water with and without HS. HA and FA materials will be obtained from commercial source and self-extracted sources. The effect of HS on the persistence, toxicity and degradation pathways of the candidate compounds will be determined. The mechanism of PAHs photolysis in the presence of HA and FA will be studied through the identification of the photoproducts by using microbial bioassay-directed chemical fractionation approach. The influence of pH on the interaction between HS and PAHs will also be investigated in this study. Specifically, we will: (1) measure acute genotoxicity and ecotoxicity of selected PAHs with Mutatox PAHs with Mutatox Test, Microtox Test and other techniques such as respirometry and microbial heterotrophic uptake of glucose and thymidine in the presence of absence of HA and FA; (2) compare major species of the PAHs photoproducts in the presence and absence of HA and FA; (3) determine the effect of HS on bioremediation efficiency of PAHs with riboflavin (an environmentally friendly photosensitizer); (4) model the dependence of toxicity/inhibition index values (e.g., ED50 of Microtex Test and respirometric technique) in individual toxicity tests on HS concentrations; and (5) assess the effect of pH on the influence of HS on the photo-induced toxicity of PAHs. The hypotheses for this study are: (1) The humic substances can reduce availability of solar irradiation in surface waters; therefore, photo- induced toxicity of PAHs in natural aquatic environment will be lower than the counterpart in pure aqueous solutions; (2) With proper manipulation of pH, remediation of PAHs-contaminated waters can be successfully implemented. The Specific Aims of this project are: 1) To determine the influence of HS on photo-induced ecotoxicity and genotoxicity of selected PAHs in natural aquatic environments with microbial bioassays; (2) To determine the effect of humic substances on the persistence and degradation pathways of the candidate PAHs; (3) To study the influence of HS on the efficiency and health impact of using sensitized photolysis for treating PAHs-contaminated waters; (4) To determine the effect of pH on the influence of HS on photo-induced toxicity of PAHs. The long-term objectives are: (1) To enhance the research capability of JSU in th area of environmental health; and (2) To fulfill MBRS Program's mission to study the possible mechanisms by which PAHs compromise human health.