Caixia Yan

Antibiotics in the surface water of the Yangtze Estuary: Occurrence, distribution and risk assessment

The occurrence and distribution of five groups of antibiotics were investigated in the surface water of Yangtze Estuary over four seasons. Of the 20 antibiotics, only sulfamerazine was not detected at all sampling sites, indicating widespread occurrence of antibiotic residues in the study area. Detection frequencies and concentrations of antibiotics were generally higher in January, indicating that low flow conditions and low temperature might enhance the persistence of antibiotics in water. Antibiotic levels varied with location, with the highest concentrations being observed around river discharge and sewage outfall. Furthermore, a positive correlation between total antibiotic and DOC concentrations revealed the significant role played by DOC. Risk assessment based on single compound exposure showed that sulfapyridine and sulfamethoxazole could cause medium risk to daphnid in the Yangtze Estuary.

Occurrence and distribution of antibiotics in the surface sediments of the Yangtze Estuary and nearby coastal areas.

The occurrence and distribution of five groups of antibiotics were investigated in the surface sediments of the Yangtze Estuary over four seasons. Four tetracyclines (TCs), sulfaquinoxaline (SQ), enrofloxacin (EFC) and thiamphenicol (TAP) were detected in all the samples, while sulfamerazine (SM) and sulfathiazole (ST) showed the lowest detection frequency. The detection frequencies and antibiotic concentrations were generally higher in January and May, indicating that low flow conditions and low temperature might enhance the persistence of antibiotics in sediment. Antibiotic levels varied with location, with the highest concentrations being observed around river discharges and sewage outfalls. Furthermore, a positive correlation between the concentration of quinolones and TOC revealed the significant role played by TOC. The concentration of quinolones at Wusongkou exceeded the trigger value (0.10 mg kg(-1)) of the Steering Committee of the Veterinary International Committee on Harmonization (VICH), which should be paid attention to in future studies.

Occurrence, distribution and risk assessment of estrogens in surface water, suspended particulate matter, and sediments of the Yangtze Estuary

The occurrence and distribution of six selected estrogen compounds were investigated in samples of surface water, suspended particulate matter (SPM), and sediment in the Yangtze Estuary and its coastal areas over four seasons. With the exception of 17α-ethinylestradiol (EE2), all estrogens were detected at least once in all three phases with bisphenol A (BPA) and estriol (E3) as the dominant estrogens in all phases. EE2 was not detected in any surface water samples. In addition, the highest total estrogen concentrations were found in January in all phases, which could be due to the low flow conditions and temperature during this season. A significant positive correlation was found between total estrogen concentrations and organic carbon (OC) contents, both in the water phase and solid phase (i.e. SPM and sediment), indicating the vital role played by OC. Based on a yeast estrogen screen (YES) bioassay, the higher estrogenic risk was found in the SPM and sediment phase when compared to the water phase. These results were confirmed by a risk assessment which revealed that the Yangtze Estuary was displayed a low to high risk over the seasons for all selected estrogens.

Environmental estrogens in a drinking water reservoir area in Shanghai: Occurrence, colloidal contribution and risk assessment

The occurrence and multi-phase distribution of six environmental estrogen compounds were investigated in a drinking water reservoir area by analyzing estrogens in suspended particulate matter (SPM), filtrate (conventional dissolved phase, <1 μm), permeate (truly soluble phase, <1 kDa) and retentate (colloidal phase, 1 kDa to 1 μm). The estrogen concentrations at different sites occurred in the following order: animal feed operation (AFO) wastewater-affected streams>tributaries>main stream channel. Correlation analysis showed that organic carbon (OC) contents had significantly positive correlations with environmental estrogens in filtrate, SPM and colloidal phases, respectively, indicating the important role played by OC. Aquatic colloids, often neglected, showed a much higher sorption capability of environmental estrogens compared to SPM. Similar Kcoc values in three types of sampling sites showed that colloids could be transported from AFO wastewater to tributaries and further into the main river channel. Mass balance calculations showed that 14.5-68.4% of OP, 4.5-32.1% of BPA, 2.0-58.4% of E1, 8.36-72.0% of E2, 0-20.6% of EE2, 3.4-62.7% of E3 and 8.3-36.1% of total estrogens were associated with colloidal fractions, suggesting that the colloids could act as a significant sink for environmental estrogens. Risk assessment demonstrated that the occurrence of environmental estrogens might pose a risk to aquatic organisms in the study area.

Selected emerging organic contaminants in the Yangtze Estuary, China: A comprehensive treatment of their association with aquatic colloids

Contaminants that are becoming detected in the environment but are not yet generally regulated or monitored are known collectively as emerging contaminants. In the present study, the occurrence and distribution of 42 emerging organic compounds (EOCs) were investigated in the Yangtze River Estuary and adjacent East China Sea coastal areas. Study compounds were mainly pharmaceuticals, including antibiotics, hormones and sterols, and also included two industrial endocrine disruptors. Samples were analyzed using cross-flow ultrafiltration (CFUF) and ultra-performance liquid chromatograph-tandem mass spectrometry (UPLC-MS/MS). Results revealed that chloramphenicols, sulfonamides and non-steroidal anti-inflammatory drugs were the dominant compounds in filtered samples with relatively high concentrations and detection frequencies. EOC levels varied with location, with the highest concentrations being observed around rivers discharging into the estuary, and near sewage outfalls. Colloids that were separated by CFUF tended to be a sink for EOCs with up to 60% being colloid-associated in the water phase. In addition, colloidal properties, including hydrodynamic size, zeta-potential and organic carbon composition, were found to be the main factors controlling the association of EOCs with aquatic colloids. Moreover, these colloidal properties were all significantly related to salinity, indicating the critical role played by increasing salinity in EOCs-colloids interaction in an estuarine system.

Effect of colloids on the occurrence, distribution and photolysis of emerging organic contaminants in wastewaters

The effect of colloids on the occurrence, phase distribution and photolysis of twenty-seven emerging organic contaminants (EOCs) was studied in domestic and livestock wastewaters (DW and LW), respectively. Filtered water (<1 μm) was separated into permeate (<1 kDa) and retentate (1 kDa-1 μm) by cross flow ultrafiltration. Results indicated that total concentration of EOCs ranged from 1220 ng L(-1) in permeate of DW to 5065 ng L(-1) in retentate of LW. The average EOC fraction associated with colloids was 13.5% and 14.4% in DW and LW. Most of the EOCs exhibited pseudo-first-order degradation kinetics in all water samples. Control experiments using glass and quartz reactors showed that UV light was more effective on the photolysis of most EOCs. The EOCs photolysis in the three fractions of DW and LW could be accelerated or inhibited compared to ultrapure water with the enhancement factor ranging from -0.94 to 7.33. The impact of colloids on the photolysis of EOCs depended on the compound and the source of water. The photolysis of most EOCs in permeates and filtrates was generally accelerated, while inhibited in the retentates, which could be attributed to the relatively high dissolved organic carbon contents in retentates.

Phenanthrene sorption to Chinese coal: Importance of coal's geochemical properties

Phenanthrene (Phen) was chosen as the probe compound for determining the sorption of PAHs to a series of different coal samples from China. Based on elemental analysis and nuclear magnetic resonance (NMR) spectra analysis, coal samples were characterized with different metamorphic evolutional degrees. The experimental sorption data were fitted well by the Freundlich model, suggesting enhanced sorption capacity and strong nonlinearity of coal samples. The combined partition and adsorption model yielded a better fit than the Freundlich isotherm, indicating that adsorption dominated the sorption at low aqueous concentrations. Correlations between coal properties and sorption capacity values indicated that C%, H/C and O/C atomic ratios were the key factors controlling the sorption behavior. Compared to total carbon, BC might play more important role in the sorption of Phen to coal samples. Moreover, there existed nonlinear relationships between combined carbon, aromatic and aliphatic carbon contents and log K(Fr) and n values, respectively, indicating the significance of aromatic and aliphatic carbon in the coal sorption behavior.

Sorption behavior of phenanthrene in Yangtze estuarine sediments: Sequential separation

In the present study, phenanthrene was chosen as the probe compound for determining the sorption of PAHs in sediments from Yangtze estuary and nearby coastal area, China. Sorption isotherms were fitted well by the Freundlich and dual models, respectively. Selected sediments were further sequentially separated to remove the carbonate and organic carbon (OC). Calculated OC sorption capacity values based on both H(2)O(2) oxidization and 375 °C combustion methods were similar and comparable to the K(oc) values estimated by the empirical linear sorption equations. Both sorption models and sorption data using sequentially separated samples achieve the similar conclusions: (1) the partition behavior dominated by OC in sediments with f(oc)>0.01; (2) for sediments with 0.001<f(oc)<0.01, OC dominated sorption at relatively high aqueous concentration; whereas mineral phase adsorption dominated sorption at lower concentration especially when C(w)/S(w) was in the range of 0.0001-0.001 in natural aqueous system.

Fluorescence characterization of fractionated dissolved organic matter in the five tributaries of Poyang Lake, China

Characterization of natural colloids is the key to understand pollutant fate and transport in the environment. The present study investigates the relationship between size and fluorescence properties of colloidal organic matter (COM) from five tributaries of Poyang Lake. Colloids were size-fractionated using cross-flow ultrafiltration and their fluorescence properties were measured by three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM). Parallel factor analysis (PARAFAC) and/or Self-organizing map (SOM) were applied to assess fluorescence properties as proxy indicators for the different size of colloids. PARAFAC analysis identified four fluorescence components including three humic-like components (C1-C3) and a protein-like component (C4). These four fluorescence components, and in particular the protein-like component, are primarily present in <1 kDa phase. For the colloidal fractions (1-10 kDa, 10-100 kDa, and 100 kDa-0.7 μm), the majority of fluorophores are associated with the smallest size fraction. SOM analysis demonstrated that relatively high fluorescence intensity and aromaticity occur primarily in <1 kDa phase, followed by 1-10 kDa colloids. Coupling PARAFAC and SOM facilitate the visualization and interpretation of the relationship between colloidal size and fluorescence properties with fewer input variables, shorter running time, higher reliability, and nondestructive results. Fluorescence indices analysis reveals that the smallest colloidal fraction (1-10 kDa) was dominated by higher humified and less autochthonous COM.

Enhanced removal of organic contaminants in water by the combination of peroxymonosulfate and carbonate

In this study, a favorable CO32-/PMS system for efficient degradation of organic contaminants (acid orange 7 (AO7), acetaminophen, para-aminobenzoic acid, phenol, methylene orange, methylene blue) in water was firstly reported. Under optimal conditions, the decolorization ration of AO7 was 100% within 40 min. Data fitting showed that the AO7 decolorization could be described by the pseudo-first-order kinetics, and the rates constant values ranging from 0.0006 to 0.2297 min-1 depending on the operating parameters (initial PMS, CO32-, AO7 concentrations). Radical scavenging studies revealed that superoxide anion radical (O2-) and singlet oxygen (1O2) rather than sulfate (SO4-) nor hydroxyl (HO) were the dominant oxidants might be responsible for AO7 degradation. The presence of NO3-, HPO42- and low concentration of Cl-, NO2-, HCO3-, H2PO4-, HA had no significantly effect on the decolorization of AO7. Adding a higher Cl- concentration displayed favorable effects on the removal efficiencies of AO7, but adding a higher NO2-, HCO3-, H2PO4- and HA concentration apparently inhibited this process. The decolorization of AO7 was lower in wastewater in comparison to other natural waters and ultrapure water, which was probably due to the presence of higher concentration of colloids in wastewater. Nevertheless, up to 94.8%, 97.0% and 85.1% of AO7 were degraded from the filtrate, permeate, and retentate phases of wastewater within 60 min, respectively. Consequently, CO32-/PMS would be promising for removal methodology for AO7 in wastewater containing considerable colloids. Finally, three intermediates were identified and degradation pathways of AO7 were proposed.