The main aim of this study was to determine the fate, bio-metabolism and environmental risk of low-ring and high-ring polycyclic aromatic hydrocarbons (PAHs) in a water-soil-ryegrass multi-media system, under long-term irrigation condition with micro-polluted treated wastewater. Field experiments were carried out to simulate garden irrigation using treated wastewater containing typical representative low-ring naphthalene (Nap) and high-ring benzo[a]pyrene (BaP). The results showed that BaP's vertical attenuation rate and adsorption accumulation rate were 1.7 and 1.2 times higher than Nap's, respectively. The adsorption, biodegradation, and the rhizosphere effect were responsible for 40.7%, 28.4%, 21.6%, and 30.5%, 36.6%, 17.7%, respectively, of the attenuation of BaP and Nap. The major metabolic pathways of Nap and BaP are hydroxylation, ring opening cleavage, and decarboxylation, with the metabolic chain of BaP being longer than that of Nap due to more ring cleaving reactions. Pseudomonas, Mycobacterium, and Sphingomonas were the functional microorganisms with PAHs degradation capacity that were positively correlated with PAHs degradation, particularly in the rhizosphere. After ten years of irrigation with treated wastewater, the prediction of environmental risk revealed that there were few potential risks. Thus, the results of this feasibility study demonstrated that using treated wastewater for garden irrigation was a relatively safe and effective strategy.

本研究的主要目的是确定长期灌溉条件下水-土壤-黑麦草多媒体系统中低环和高环多环芳烃 (PAHs) 的去向、生物代谢和环境风险处理微污染的废水。使用含有典型代表性低环萘 (Nap) 和高环苯并[ a]芘 (BaP)。结果表明，BaP的垂直衰减率和吸附积累率分别是Nap的1.7倍和1.2倍。吸附、生物降解和根际效应分别导致 BaP 和 Nap 衰减的 40.7%、28.4%、21.6% 和 30.5%、36.6%、17.7%。Nap和BaP的主要代谢途径是羟基化、开环裂解和脱羧，由于开环反应较多，BaP的代谢链比Nap长。假单胞菌属、分枝杆菌属和鞘氨醇单胞菌属是具有 PAHs 降解能力的功能性微生物，与 PAHs 降解呈正相关，特别是在根际。经过十年灌溉处理后的废水，对环境风险的预测表明潜在风险很少。因此，这项可行性研究的结果表明，将处理后的废水用于花园灌溉是一种相对安全有效的策略。