Distribution patterns of octylphenol and nonylphenol in the aquatic system at Mai Po Marshes Nature Reserve,a subtropical estuarine wetland in Hong Kong

Spatial and temporal distribution of octylphenol （OP） and nonylphenol （NP） in Mai Po Marshes, a subtropical estuarine wetland in Hong Kong, were investigated. Surface water samples were collected every month from 11 sites during the period of September- December 2004. Concentrations of OP and NP ranged from 11.3 to 348 ng/L and from 29 to 2591 ng/L, respectively. The high levels of NP and OP were found in November and December than in September and October. The levels of OP and NP have no significant spatial differences except September. Total organic matter in the sediments appeared to be an important factor in controlling the fate of these compounds in the aquatic environment.

Dependence of bisphenol A photodegradation on the initial concentration of oxalate in the lepidocrocite-oxalate complex system

To understand the degradation of endocrine disrupting chemicals （EDCs） in natural environment with existence of iron oxides and carboxylic acids, the dependence of bisphenol A （BPA） photodegradation on the initial concentration of oxalate （Cox） in lepidocrocite （y-FeOOH） aqueous suspension was investigated under both UV and visible lights in this study. Lepidocrocite powder was home-prepared by a hydrothermal process. It was found that BPA degradation was promoted greatly in the presence of oxalate owing to the formation of lepidocrocite-oxalate complex. And there was an optimal Cox, which was 2.0 and 2.4 mmol/L, under UV and visible lights, respectively. The first-order kinetic constant, k value increased 38 times from 0.17 × 10^-2 min^-1 in the absence of oxalate to 6.39 × 10^-2 min^-1 in the presence of oxalate with an optimal Cox （2.0 mmol/L） under UV irradiation, and almost 306 times from 0.02 × 10^-2 min^-1 in the absence of oxalate to 6.11 × 10^-2 min^-1 in the presence of oxalate with an optimal Cox （2.4 mmol/L） under visible irradiation. The BPA degradation rate increased and the first-order kinetic constants decreased with the increase in BPA initial concentration. The dependence of the variation of pH value, total-Fe and Fe^2＋ during the photoreaction on Cox was also investigated. The pH value increased obviously with the reaction time. Total-Fe increased dramatically at the first 5 min and then decreased quickly under UV irradiation and slowly under visible irradiation. The initial concentration of oxalate is a main factor to affect BPA photodegradation in aqueous suspension under both UV and visible lights.