Shu-Chuan Peng

Organochlorine Pesticides in Sediments around Chaohu Lake: Concentration Levels and Vertical Distribution

ABSTRACT Eighteen organochlorine pesticides (OCPs) were investigated in surface sediments from the Nanfei River and in four sediment cores from the primary estuaries of Chaohu Lake, Eastern China. The results indicate that the OCP concentrations in the surface and core sediments around Chaohu Lake were 3.48–121.08 (with a mean of 34.93) ng/g and 0.60–39.28 (7.07) ng/g, respectively. Significantly higher concentrations of ΣOCPs were observed in sediment samples from the Nanfei River and its estuary. The three important OCP contributors around Chaohu Lake were dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), and hexachlorobenzene (HCB), which originated primarily from the historical use of technical DDTs and HCHs. A principal component analysis (PCA) suggests that HCB and lindane may originate from the same sources, and DDTs were greatly influenced by organic carbon from the soil environment and the impact of urbanization processes.

Identification and determination of the contribution of iron–steel manufacturing industry to sediment-associated polycyclic aromatic hydrocarbons (PAHs) in a large shallow lake of eastern China

Seventeen polycyclic aromatic hydrocarbon (PAH) compounds were determined in surface sediments collected from the Chaohu Lake (a large shallow lake in eastern China) and its tributaries. Both diagnostic ratios and a receptor model (positive matrix factorization, PMF) were applied to identify and determine the contribution of a local iron–steel manufacturing plant located in the Nanfei River (NFR) to the Chaohu Lake basin. The results show that sites located in the downstream of the steel plant contained concentrations of 17 PAH (Σ17PAH) approximately two orders of magnitudes higher than those from other sites. Five factors were identified by the PMF model, including industrial waste, wood/biomass burning, diagenetic origin, domestic coal combustion, and industrial combustion. Our findings suggest that sediments in the downstream of the plant and in the western part of the Chaohu Lake were predominantly affected by industrial coal combustion. A mixture of pyrolytic origins impacted urban sediments in the upstream of the plant, whereas diagenetic origins along with coal and biomass burning were suggested to influence the eastern part and rural tributaries of the lake. To assess the potential ecological risk and toxicity caused by the iron–steel plant, sediment toxicity was evaluated by the PMF model, sediment quality guideline, and toxic equivalent factors. All of the three approaches suggested PAH accumulation in the NFR sediments could produce significant adverse ecological effects and half of the sediment toxicity in the NFR may be attributed to the emissions from the iron–steel plant. Some rural locations also exhibited PAH concentrations above probable effects, most likely contributed by wood/biomass burning.

Photochemistry of the Mixed Aqueous Solution of Nitrobenzene and Hydrogen Peroxide Initiated with 266 nm UV Light

ABSTRACT The reaction microscopic mechanism of mixed aqueous solutions of nitrobenzene and hydrogen peroxide under different conditions was studied by the laser flash photolysis technique (266 nm). The main characteristic peaks in these transient absorption spectra were attributed and the build-up/decay trends of several transient species were investigated. The transient absorption peaks of 285 nm and 305 nm were attributed to when nitrobenzene aqueous solutions were irradiated by 266 nm UV light and the decay rate constant was k 285 nm = 1.22 × 104 s−1 and k 305 nm = 1.05 × 104 s−1 in the presence of N2. k 285 nm and k 305 nm increased to 1.32 × 104 s−1 and 2.05 × 104 s−1, respectively, in the presence of O2. OH radical can be produced through the 266 nm laser flash photolysis of hydrogen peroxide in aqueous solutions. The rate constant of the reaction between OH radical and nitrobenzene was measured to be (3.6–6.0) × 109 (L · mol−1 · s−1). The intermediate of the C6H5NO2-OH adduct can undergo secondary self-decay with a reaction rate of 2k/ϵl = 1.82 × 106 s−1. The C6H5NO2-OH adduct is able to react with O2 to form C6H5NO2-OHO2 with a rate constant of (6.6 ± 0.56) × 107 (L · mol−1 · s−1).