Removal of microplastics in municipal sewage from China's largest water reclamation plant.

Municipal sewage treatment plants (STPs) are an important point source of microplastics in domestic waterways. In the present study, effluents from the largest water reclamation plant in China were sampled throughout the treatment process and microplastics were extracted and identified to evaluate their removal. As expected, microplastics were detected in the influent (12.03 ±â€¯1.29 items/L). Following treatment, concentrations of microplastics were reduced by greater than 95% and 0.59 ±â€¯0.22 items/L of microplastics were detected in reclaimed waters. Among detected microplastics, 18 types of polymers of ten colors were identified. Polyethylene terephthalate (PET), polystyrene (PS) and polypropylene (PP) accounted for greater than 70% of detected microplastics. Furthermore, microfibers were the dominant shape detected with an average size of 1110.72 ±â€¯862.95 µm. However, microparticles accounted for only 14.08% of total microplastics with an average size of 681.46 ±â€¯528.73 µm. Results of the present study suggest that current treatment technologies employed at the chosen STP are efficient to remove the majority of microplastics, however consideration of STPs as a point source of microplastics is important due to the large volumes of effluents being released into the aquatic environment on a consistent basis.

Microfiber release from different fabrics during washing.

Microfiber is a subgroup of microplastics and accounts for a large proportion of microplastics in aquatic environment, especially in municipal effluents. The purpose of the present study was to quantify microfiber shedding from three most populate synthetic textile fabrics: polyester, polyamide, and acetate fabrics. The results showed that more microfibers were released after washing with a pulsator laundry machine than a platen laundry machine. The greatest number of microfibers was released from acetate fabric, which was up to 74,816 ±â€¯10,656 microfibers/m2 per wash, although microfibers were shed from all materials. Moreover, an increasing trend was found in the number of microfibers shedding from synthetic fabrics with the washing temperature increasing, and greater microfiber release occurred when washing fabrics with detergent rather than with water alone. The lint filter bag equipped with the pulsator laundry machine retained the longer microfibers (>1000 µm), but not the shorter microfibers (<500 µm) instead of releasing into the drainage system. Our data suggested that microfibers released during washing of synthetic fabrics may be an important source of microfibers in aquatic environment due to the increasing production and use of synthetic fabrics globally. Thus, more efficient filtering bags or other technologies in household washing machines should be developed to prevent and reduce the release of microfibers from domestic washing.

[Spatio-temporal Distribution and Source Apportionment of Nitrogen in Rivers of Tieling].

This study analyzed the spatio-temporal distribution and sources of nitrogen (N) in 22 rivers in Tieling City during 2013-07-2014-07. The results showed that the concentrations of TN, NO3--N, and NH4+-N were 1.26-18.85, 0.53-11.8, and 0.3-15.7 mg·L-1, with an annual mean value of (5.8±1.9), (2.8±1.74), and (2.0±1.1) mg·L-1, respectively. Overall, NO3--N was the main form of N with a percentage of 48%. The concentration of N in the wet season was significantly higher than that in the normal and dry seasons. According to the standards for surface water quality, water quality in eight rivers was worse than grade Ⅲ. Tiaozi River and Xiaoqing River were seriously polluted by ammonia N with a grade Ⅴ water quality through the sampling period, while Xiliao River, Xiaohezi River, and Liao River met the water quality standards. During the sampling period, δ15 N and δ18 O in nitrate in river waters were -3.0‰-23.9‰ and -11.7‰-57‰, respectively. Based on the data on the isotopes of N and O, N in the rivers in Tieling City mainly originated from human and animal excreta, industrial effluents, and domestic sewage. Sources of riverine N varied with seasons. For example, N in Tiaozi River and Nianpan River was mainly from fertilizer use and soil nitrogen in the wet season while it was from the industrial effluents and domestic sewage in the dry season.

Effects of land use on the concentration and emission of nitrous oxide in nitrogen-enriched rivers.

Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Nitrogen-enriched rivers are significant sources of atmospheric N2O. This study conducted a one-year field campaign in seven N-enriched rivers draining urban, rural, and agricultural land to determine the link between the production, concentrations, and emissions of N2O and land use. Estimated N2O fluxes varied between 1.30 and 1164.38 µg N2O-N m-2 h-1 with a mean value of 154.90 µg N2O-N m-2 h-1, indicating that rivers were the net sources of atmospheric N2O. Concentrations of N2O ranged between 0.23 and 29.21 µg N2O-N L-1 with an overall mean value of 3.81 µg N2O-N L-1. Concentrations of ammonium and nitrate in urban and rural rivers were high in the cold season. The concentrations were also high in agricultural rivers in the wet season. N2O concentrations and emissions in rural and urban rivers followed a similar pattern to ammonium and a similar pattern to nitrate in agricultural rivers. A strong link between the concentrations and emissions of N2O and land use was observed. N2O concentrations in and emissions from the rivers draining the urban and rural areas were significantly higher than the rivers draining the agricultural areas (P < 0.01). Stepwise regression analysis indicated that dissolved N2O were primarily influenced by NH4+ in agricultural rivers and by NO3- in rural rivers; while dissolved N2O in urban rivers was primarily predicted by temperature and reflected the integrated impact of sewage input and river hydrology. Nitrate-N and NO3--O isotope data and linear regression of N2O and river water variables strongly indicated that dissolved N2O was mainly derived from nitrification in agricultural rivers and denitrification in rural and urban rivers.

[Concentration, Flux, and Emission Factor of N2O in Rivers with Different Nitrogen Pollution Features].

In this study, 22 rivers in Tieling City were selected to study the concentration, flux, and emission factor (EF5r) of N2O. Based on the concentrations and components of nitrogen (N), the 22 rivers can be divided into ammonia nitrogen (NH4+)-polluted rivers (mean NH4+=5.86 mg·L-1), nitrate nitrogen (NO3-)-polluted rivers (mean NO3-=3.05 mg·L-1), and N-limited rivers[mean DIN (NH4++ NO3-)=1.04 mg·L-1]. Overall, the concentration of N2O ranges from 17.03 to 9028.60 nmol·L-1, with a mean value of 546.75 nmol·L-1 (mean saturation=6256%). The emission fluxes across the water-air interface range from 17.21 to 15655.3 µg·(m2·h)-1, with a mean value of 949.36 µg·(m2·h)-1, indicating that those rivers are net sources of atmospheric N2O. The concentration and flux of N2O observed in NH4+-polluted rivers are significantly higher than that in the NO3--polluted and N-limited rivers. According to the method proposed by the IPCC, EF5r varies greatly among the three types of rivers and the coefficient of variation of EF5r is 445%. The EF5r for NO3--polluted rivers is on average 0.0005, which is lower than the recommended value of 0.0025. However, the EF5r for NH4+-polluted rivers is on average 0.4456, which is 180 times the recommended value and may be caused by the lower NO3- concentration of those rivers. The EF5r of N-limited rivers averages 0.0050 and is two times the recommended value. Thus, it is necessary to assess the pollution status of N before calculating the EF5r for the riverine system. We suggest that the EF5r for NH4+-polluted and N-limited rivers should be calculated using[N2O]/[NH4+] and[N2O]/[DIN], respectively, without assessing the composition and concentration of N.

Transcriptomic responses of the freshwater snail (Parafossarulus striatulus) following dietary exposure to cyanobacteria.

Freshwater snails are promising bioindicators that can be used in ecotoxicological testing and ecological risk assessments. To screen molecular responses following mollusk exposure to algal blooms, whole transcriptome sequencing was performed with the freshwater snail (Parafossarulus striatulus) fed with blue algae (Microcystis aeruginosa). A total of 86,848 unigenes were assembled, and 10,413 unigenes were annotated in the TrEMBL, Pfam, KEGG, and SwissProt databases. In snails fed with both green and blue algae, a total of 276 differentially expressed unigenes were identified, though there were limited differences in snails fed with only green algae. In addition, ten randomly selected differentially expressed unigenes were analyzed in snails collected from Taihu Lake, China. The expression of four unigenes exhibited a trend consistent with that observed in transcriptome profiling of laboratory snails. The results of this study provide an invaluable resource for enhancing our understanding of ecotoxicology following the occurrence of algal blooms in lakes.

[Denitrification in water of Daliao River estuary in summer and the effect of environmental factors].

Ratios of nitrogen loss and N2O production by denitrification were observed in Daliao River and the estuary in summer 2013. The results showed that the concentrations of N and P in the main stream of Daliao River were significant higher than those in the estuary (P < 0.05). Decrease of nutrients concentration in the estuary might be integrally caused by water diluting and biogeochemical processes. The net increase of dissolved N2 (ΔN2) ranged between -11.01 and 71.37 µmol x L(-1), in which the negative values were mostly determined in the main stream of the river, indicating the consumption amount of N2 was higher than the production in the fresh water. The mean ratio of N2O production during the process of denitrification was about 0.007%, and the N2O flux across water-air interface was about 0.04% of the total fluxes (N2O + N2). In this study, ΔN2 was not related with DO, while exhibited a significant positive correlation with water temperature and salinity, and a negative correlation with NO3-. This suggests that denitrification was not totally regulated by DO level in the estuary, and coupled nitrification-denitrification was the main denitrification process. Finally, we estimated that 26% of the TN, 37% of the DIN, and 43% of the NO3- were removed by denitrification in the Daliao River estuary based on the ratio of ΔN2 to N concentrations.

Mechanism of ofloxacin fluorescence quenching and its interaction with sequentially extracted dissolved organic matter from lake sediment of Dianchi, China.

The wide use and occurrence of antibiotics in water environments have caused wide concerns. Ofloxacin (OFL) was selected as a target antibiotic, and the interaction between OFL and sequential extracted dissolved organic matter (DOM) from the sediment of Dianchi, a hypertrophic lake in Southwest China, was explored using fluorescence quenching technology. The method of fuorescence quenching was used to characterize the interaction between OFL and sequentially extracted DOM. The result indicated that static and dynamic quenching both existed in the interaction. The interaction in the background water (0.01 mol/L NaCl and 200 mg/L NaN3) became increasingly weak with the further extraction of DOM. A low non-linear factor N value (0.53∼0.63) of Freundlich model was observed, indicating a non-linear interaction between OFL and DOM. Elemental characterization and infrared spectrum analysis showed an enhanced OFL-DOM binding with the decrease in humic acid (HA) polarity. The effect of ion strength was tested in the OFL-DOM interaction to show the impact of usually existing metal ions in water environment on the OFL behavior. The result showed that K(+) had little influence, but Cu(2+) had a significant promotion (p < 0.05) in the OFL-DOM interaction in background water, indicating that divalent metal ions, which have the bridge bond or complexation capacity, are more active in the OFL-DOM interaction than monovalent ions, with no bridge bond or complexation capacity. This work would be useful in the fate and risk assessment of antibiotics in water environments.

Temporal and spatial changes in nutrients and chlorophyll-a in a shallow lake, Lake Chaohu, China: an 11-year investigation.

Temporal and spatial changes of total nitrogen (TN), total phosphorus (TP) and chlorophyll-a (Chl-a) in a shallow lake, Lake Chaohu, China, were investigated using monthly monitoring data from 2001 through 2011. The results showed that the annual mean concentration ranges of TN, TP, and Chl-a were 0.08-14.60 mg/L, 0.02-1.08 mg/L, and 0.10-465.90 microg/L, respectively. Our data showed that Lake Chaohu was highly eutrophic and that water quality showed no substantial improvement during 2001 through 2011. The mean concentrations of TP, TN and Chl-a in the western lake were significantly higher than in the eastern lake, which indicates a spatial distribution of the three water parameters. The annual mean ratio of TN:TP by weight ranged from 10 to 20, indicating that phosphorus was the limiting nutrient in this lake. A similar seasonality variation for TP and Chl-a was observed. Riverine TP and NH4+ loading from eight major tributaries were in the range of 1.56 x 10(4)-5.47 x 10(4) and 0.19 x 10(4)-0.51 x 10(4) tons/yr over 2002-2011, respectively, and exceeded the water environmental capability of the two nutrients in the lake by a factor of 3-6. Thus reduction of nutrient loading in the sub-watershed and tributaries would be essential for the restoration of Lake Chaohu.