Xuede Li

The occurrence and distribution of antibiotics in Lake Chaohu, China: Seasonal variation, potential source and risk assessment

The distribution and seasonal variation of fifteen antibiotics belonging to three classes (sulfonamides, fluoroquinolones and tetracyclines) were investigated in Lake Chaohu, China. The concentrations of the selected antibiotics in the surface water, eight major inflowing rivers and sewage treatment plant (STP) samples were analyzed by UPLC-MS/MS. The results indicated that sulfamethoxazole and ofloxacin were the predominant antibiotics, with maximum concentrations of 95.6 and 383.4ngL(-1), respectively, in the river samples. In Lake Chaohu, the western inflowing rivers (the Nanfei and Shiwuli Rivers) were the primary import routes for the antibiotics, and the domestic effluent from four STPs were considered the primary source of the antibiotics. The level of antibiotics in Lake Chaohu clearly varied with seasonal changes, and the highest detectable frequencies and mean concentrations were found during the winter. The quality of water downstream of Lake Chaohu was influenced by the lake, and the results of risk assessment of the antibiotics on aquatic organisms suggested that sulfamethoxazole, ofloxacin, ciprofloxacin and enrofloxacin in the surface water of Lake Chaohu and inflowing rivers might pose a high risk to algae and plants.

Facile synthesis of tea waste/Fe3O4 nanoparticle composite for hexavalent chromium removal from aqueous solution

The modification of biomass waste, as a multifunctional composite, has received tremendous attention for resource utilization and recycling. In this study, tea waste, which is a high level generator of biomass waste, was loaded with nano-Fe3O4 particles to prepare a magnetic tea waste/Fe3O4 (TW/Fe3O4) composite through a facile chemical co-precipitation approach. BET, SEM, TEM, XRD, magnetic properties, FTIR, XPS were used to characterize the TW/Fe3O4 composite. A superparamagnetic TW/Fe3O4 composite (Fe3O4: about 20 nm) was successfully synthesized and possessed the advantages of tea waste and nano-Fe3O4 particles. A chromium(VI) adsorption experiment showed that this material has a strong adsorption capacity for aqueous chromium ions, which reached 75.76 mg g−1 based on the Langmuir model. The adsorption process could be well fitted by a pseudo-second-order kinetic model and Langmuir, Temkin and Dubinin–Radushkevich (D–R) isotherm models, and was spontaneous and endothermic according to the thermodynamic analysis. The TW/Fe3O4 composite revealed good reusability and the removal rate was more than 70% after five recycling cycles. The mechanism of Cr(VI) removal involved electrostatic attraction, reduction process, ion exchange, surface complexation, etc. 70% of Cr(VI) was reduced to Cr(III) in this investigation. This study indicated that a TW/Fe3O4 composite could be an attractive option for heavy metal treatment.

Promoting photosensitized reductive dechlorination of chlorothalonil using epigallocatechin gallate in water.

Chlorothalonil (CTL) is a broad-spectrum fungicide. Photodegradation is a main degradation pathway of CTL in water. Because of the high aquatic toxicity of CTL and its metabolite 4-hydroxy CTL (CTL-OH), it is significant to develop an effective method to degrade CTL but without formation of CTL-OH. Epigallocatechin gallate (EGCG) is an abundant tea byproduct and has more than 100-fold reducing power than vitamin C. The present study reports photosensitization effects of EGCG on CTL photodegradation in water under sunlight and artificial lights. The results indicated that EGCG significantly photosensitizes CTL photodegradation. Under high-pressure mercury light illumination, CTL underwent primarily reductive dechlorination. CTL-OH, a main CTL photolytic product, was not detected when EGCG was added in the water. We concluded that EGCG not only significantly enhances CTL photodegradation rate but also alters the photodegradation pathways, avoiding the production of the highly toxic CTL-OH. The results indicated high potential of using EGCG to minimize CTL aquatic toxicity and pollution.

Photodegradation Rate and Products of Acetochlor in Aqueous Solution

Photodegradation of acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphe myl) acetamide] was carried out in water and water-H2O2 solution under high pressure mercery lamp(HPML) or sunlight illuminating. The result shown that the photodegradation of acetochlor followed the first-order kinetics. The photolysis rate constants were 1.04 times 10-1 min-1 by HPML illuminating and 1.93 times 10-2 h-1 under sunlight illuminating, respectively. H2O2 increased the photodegradation rate of acetochlor in water solution. At least 12 photodegradation products of acetochlor were found by GC-MS analyses. Among them, three components, namely 8-methyl-1 -methoxymethyl-4-methyl-2-oxo-1,2,3,4-tet rahydroquinone( I ), 2 - methyl - 6 - N - methoxyethyl - N - oxacycloethylene - aniline( II), N- chloroacetyl - 7 - ethyl - 2, 3 - dihydroindole(III), were identified by TLC and GC-MS.

Bioconcentration, metabolism and the effects of tetracycline on multiple biomarkers in Chironomus riparius larvae

The antibiotic tetracycline (TC) is widespread in surface waters, but few data are available regarding its adverse effects on aquatic insects. In this study, we investigated the bioconcentration, metabolism, and effects of TC on Chironomus riparius larvae exposed to different concentrations of TC (1.83, 18.5 and 174 μg L-1) for 48 h. The bioconcentration factors were 3.65, 0.74 and 0.23 in larvae with exposure to 1.83, 18.5 and 174 μg L-1 TC, respectively. High concentration ratios of the metabolites anhydrotetracycline (0.56-0.60), 4-epitetracycline (0.43-0.69), and 4-epianhydrotetracycline (0.50-0.55) to the unmetabolized compound were found. Additionally, the activities of superoxide dismutase and glutathione S-transferase were markedly inhibited with a significant increase in malondialdehyde contents at high exposure concentrations of TC (18.5 and 174 μg L-1). Moreover, significant up-regulation of heat shock genes (hsp70 and hsp27), the ecdysone receptor gene, and the E74 early ecdysone responsive gene was observed at all exposure concentrations except for hsp70 at 1.83 μg L-1. Collectively, these results suggested that TC was quickly absorbed and metabolized by C. riparius and resulted in molecular and biochemical disturbances.

Oxalate Enhances Desorption of Perfluorooctane Sulfonate from Soils and Sediments

Perfluorooctane sulfonate (PFOS) is one of the most widespread toxic substances in water distribution systems, posing a significant risk to public health and the environment due to its toxic and non-biodegradable nature. In this study, the effect of oxalate on PFOS adsorption/desorption to/from soil and sediment samples was studied with batch experiments. Dissolved organic carbon content in soil strongly enhanced the retention of organic halogens. Oxalate increased PFOS desorption by 1.43- to 17.14-fold and significantly increased the release of dissolved organic carbon and inorganic ions in soils. The effects of root exudates were similar to those of oxalate. Addition of low molecular weight dissolved organic carbon caused partial dissolution of the soil structure (e.g., through formation of organo-mineral complexes), resulting in the release of organic carbon and metal ions and subsequently enhancing PFOS desorption. The effects of oxalate on organic halogen desorption were influenced by dissolved organic carbon content and formation of calcium oxalate.

Effects of Surfactants on the Photolysis of Chlorothalonil on Pepper (Capsicum annuum var. grossum Sendt)

Chlorothalonil is a widely used fungicide on pepper and other vegetables in China. The present study was aimed to evaluate effects of three different surfactants, sodium dodecyl sulfonate (SDS), Span-20, and cetyltrimethylammonium bromide (CTAB), on the photolysis of chlorothalonil on peppers under irradiation of either high-pressure mercury lamp (HPML) or sunlight inside and outside greenhouse. Results showed that both SDS and Span-20 at a low concentration exhibited a photosensitization effect on the photolysis of chlorothalonil under HPML. Such effect gradually decreased with increasing concentrations of either surfactant prior to photoquenching effects observed. In contrast, CTAB showed a photoquenching effect on chlorothalonil photolysis, which was gradually enhanced with an increasing CTAB concentration. SDS, Span-20, and CTAB had consistent effects on the photolysis of chlorothalonil under sunlight as those observed under HPML irradiation. The use of appropriate surfactants as pesticide additives at optimal concentrations could decrease the residue of pesticide in agricultural food and improve food safety.