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The pollution of micro/nanoplastics in the natural environment is becoming increasingly serious, but the potential effects of nanoplastics on crops remain unclear. In the present study, the effects of polystyrene nanoplastics (PS-NPs) with a particle size of 80 nm on the chlorophyll content, antioxidant enzyme activity, and nutritional quality of Allium sativum L. were explored via hydroponic culture. The results showed that the chlorophyll contents in leaves of A. sativum treated with PS-NPs were significantly lower than those in the control, indicating that the synthesis of chlorophyll was inhibited. The superoxide dismutase (SOD), ascorbate peroxidase (APX) activities, and proline contents in leaves of A. sativum initially increased but then decreased with the increase in ρ (PS-NPs). The activity of guaiacol peroxidase (POD) increased with the increase in ρ (PS-NPs) for 10 days of treatment; however, it was inhibited for 20 days of treatment. The malondialdehyde (MDA) content increased with the rise in ρ (PS-NPs). When ρ (PS-NPs) increased to 100 mg·L -1 , the MDA content in leaves of A. sativum increased by 43.24% and 89.70% for 10 and 20-day treatments, respectively, compared with those in the control. Meanwhile, the contents of soluble protein, soluble sugar, and vitamin C were higher than those in the control for 10-day treatments; however, the vitamin C content decreased by 26.53% after 20 days of treatment. These results indicated that PS-NPs had a significant oxidative stress on A. sativum , and a high concentration of PS-NPs stress would have deleterious effects on the nutritional quality of A. sativum .

This study used vertical and horizontal subsurface constructed wetlands with continuous inflow, to compare and analyze the effects of four hydraulic residence times on the removal efficiency of conventional pollutants. Using the optimal hydraulic retention time, the two types of wetlands were examined in terms of the stromal layer nitrification, denitrification, and ammonia oxidation abundance of functional genes, as well as the intensity of nitrification and denitrification. In addition, redundancy analysis and variance decomposition analysis were used to determine the main factors affecting nitrogen removal in the two kinds of wetlands, so that targeted improvement measures can be suggested. The best removal efficiency of conventional pollutants (COD, TP, TN, and NH 4 + -N) was achieved with a hydraulic retention time of 24 h, resulting in a removal rate of more than 70%. With a 24 h retention time, the removal rate of NH 4 + -N and TN and the intensity of nitrification and denitrification exhibited a gradually decreasing trend along the flow direction. Among the three functional genes, the abundance of denitrification functional genes ( nirS ) was much higher than that of nitrification functional genes ( nxrA ) and ammonia oxidation functional genes (AOB- amoA ). In this study, the nitrogen removal ability of the two subsurface flow constructed wetlands was jointly affected by environmental factors and microbial factors, among which microbial factors contributed the most to nitrogen removal (55% and 48%). In addition, the removal rates of TN and NH 4 + -N were proportional to DO, specific surface area of substrate, COD concentration, as well as nitrification and denitrification functional genes, but inversely proportional to pH. Therefore, in order to improve the nitrogen removal efficiency of both systems, the amount of dissolved oxygen and carbon sources in the substrate layer should be increased, while the pH value should be appropriately reduced. Moreover, the horizontal subsurface constructed wetland significantly improves the nitrogen removal efficiency of the system, as the substrate layer has a larger specific surface area. This study provides a theoretical basis for the design of constructed wetlands and the selection of an optimal hydraulic residence time. Quantitative analysis of nitrogen removal pathways is of great significance for understanding the nitrogen removal mechanism and improving the nitrogen removal rate in constructed wetlands.

To identify the sources of nitrogen pollutants in the Muli River basin in the Guangdong-Hong Kong-Macao Greater Bay Area, ammonium salt isotope tracer technology, nitrate isotope tracer technology, and a multiple linear mixing model were applied in this study to effectively identify the changes of nitrogen sources in the basin. The results showed that nitrogen pollution in the Muli River basin was serious, and the concentrations of NH 4 + -N and NO 3 - -N in the confluence were higher than in the two tributaries. In addition, although there was no obvious population residence at the upstream or downstream of the Muli River basin, higher nitrogen pollution still occurred at some sites (Dakengshan tributary and aquiculture area). Qualitative analysis of ammonium salt and nitrate isotopes showed that nitrogen pollution in the Muli River basin mainly came from soil, fertilizer, atmospheric particles, and animal and human excreta. The results of the multiple linear mixing model showed that the main source of nitrogen in the upper reaches of the Dakengshan tributary is atmospheric subsidence, with a contribution rate of about 80%. The average contribution rate of soil organic nitrogen in the upper reaches of the Jilongkeng tributary was 33%, higher than those of the Dakengshan tributary (9%) and Muli River (24%). The contribution rate of sewage and manure to nitrogen pollution was up to 70% in the lower reaches of the Dakengshan tributary, the lower reaches of the Jilongkeng tributary, and the middle and upper reaches of the Muli River. In addition, while all forms of livestock and poultry farming and aquiculture activity were stopped, the contribution rate of sewage and manure in Yangzhiqu was found to be still as high as 56%, which is much higher than that at the Danshui River Dam section in the lower part of the Muli River (3%); this may be due to residual livestock waste in the sediment. This study qualitatively and quantitatively analyzed the nitrogen sources of the Muli River basin, which provids a theoretical basis for pollution source management in the Greater Bay Area.

Acetyl metabolites are the major metabolites of sulfonamides. In order to investigate the removal mechanism of four commonly used sulfonamides and their metabolites in wastewater treatment plants, sulfonamides and their corresponding acetyl metabolites in wastewater and sludge in a wastewater treatment plant equipped with A 2 /O in Xiamen City were sampled. Sample selection was based on the hydraulic retention time. Solid phase extraction followed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was applied to analyze the target compounds. Results showed that six out of eight of the target compounds were detected in the wastewater, while five were detected in the sludge. Based on the removal efficiencies overall and of the different compartments, the concentration of sulfamethazine was almost unchanged during wastewater treatment plant (WWTP) processes, the other sulfonamides were removed with different removal efficiencies. Removal efficiencies varied for every compartment. The potential removal pathways were analyzed based on the mass balance of the target compounds. The removal pathway of sulfamethazine was sludge adsorption, while the potential removal mechanism of sulfamerazine, sulfadiazine, and sulfamethoxazole was biodegradation.

A detailed field survey of arsenic species and water quality parameters was conducted in different eutrophicated regions of Lake Taihu (Zhushan Bay, Meiliang Bay, Gonghu Bay and Southern Taihu) in summer and winter. Furthermore, spatial and seasonal distributions of arsenic species and their relations to water quality parameters were investigated with multivariate analysis techniques. Higher average contents of total arsenic (TAs), arsenate[As(Ⅴ)], arsenite[ As(Ⅲ)] and methylarsenicals [sum of monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA)] were observed in northern regions (including Zhushan Bay, Meiliang Bay, and Gonghu Bay) (TAs:2.58-3.34 μg·L -1 , As(Ⅴ):1.37-2.34 μg·L -1 , As(Ⅲ):0.53-0.64 μg·L -1 , methylarsenicals:0.16-0.36 μg·L -1 ), compared to those in Southern Taihu (1.73, 1.10, 0.31, 0.10 μg·L -1 ). The results exhibited obvious spatial characteristics of arsenic species in the surface water of Lake Taihu. Besides, average values of TAs, As(Ⅴ), As(Ⅲ) and methylarsenicals in summer were 3.40, 2.06, 0.73 and 0.25 μg·L -1 , respectively, higher than those in winter (1.78, 1.10, 0.30, 0.17 μg·L -1 ), reflecting significant seasonal characteristics of arsenic distribution. Factor analysis revealed the significant relationships of TAs and As(Ⅴ) with several water quality parameters, which suggested that spatial and seasonal distributions of TAs and As(Ⅴ) in Lake Taihu were affected by external pollution and internal arsenic release from sediments. Redundancy analysis further indicated significant effects of total phosphorus (TP) and total iron (TFe) on the distributions of TAs and As(Ⅴ). At the mean time, the above statistical analyses exhibited that As(Ⅲ) and methylarsenicals were positively correlated with chlorophyll-a (Chl-a). A large amount of microalgae could accumulate As(Ⅴ) and transform it more strongly to As(Ⅲ) and methylarsenicals in eutrophic regions when compared to mesotrophic region,especially in summer, reflecting the regulation of microalgae on arsenic biotransformation.

The purpose of this study was to characterize the decomposition process of different plant litters and its controlling factors, and to quantify the different contribution rates to sediments organic matter throughout the decomposition of different plant litters. Results showed that the decomposition rates of plant litters buried at medium tidal level were 0.655 a(-1) for mangrove and 1.723 a(-1) for Spartina, which were greater than those with 0.651 a(-1) for mangrove and 1.586 a(-1) for Spartina at high tidal level. The reduction of carbon concentration in plant litters at high tidal level was lower than that at medium tidal level, while the increment of nitrogen and sulfur concentrations in plant litters at high tidal level was greater than those at medium tidal. And the isotope abundance of carbon (delta13C) in plant litters at medium tidal level reduced much more significantly than that at high tidal level. The contribution rates of plant litters carbon to sediments organic matter differed among tidal levels, plant species and decomposition duration. Specifically, the decomposition of mangrove litters contributed 5.96% to the sediment organic matter at medium tidal level, which was greater than that (3.03%) at high tidal level. Similarly, the decomposition of Spartina litters contributed 14.81% to the sediment organic matter at medium tidal level, which was also greater than that (13.97%) at high tidal level. The contribution of the decomposition of Spartina litters organic matter (average with 14.39%) was greater than that of mangrove litters (4.50%). The decomposition of plant litters requires a long process. The contribution of plant litters to sediments organic matter throughout one year decomposition was lower than that in complete decomposition, in particular, mangrove litters. Our study showed that the quantitative differences in plant litters-derived sediment organic matter would improve the proper estimation of the contribution of litters to wetland organic matter.

Dissolved oxygen (DO) is one of the important environmental factors influencing the ammonia oxidation process. In order to examine the effects of DO on ammonia oxidation process and its potential mechanisms, surface sediments from Jiulong River Estuarine Wetland were collected and cultured to obtain enrichment cultures. Then the enrichment cultures were inoculated under different levels of DO, and the diversity of ammonia-oxidizing microorganisms was analyzed using PCR-DGGE technique to determine the effect of DO on the ammonia oxidation rate and the ammonia-oxidizing microorganism diversity. Results showed that the Shannon index was 2. 00 and 2.05 for ammonia-oxidizing bacteria (AOB) under saturated and aerobic conditions, respectively, and the values were 2.49 (saturated) and 2.03 (aerobic) for ammonia-oxidizing archaea (AOA). However, this index was 1.76 and 1.80 for AOB under hypoxia and anaerobic condition, and 1.27 and 2. 21 for AOA. Under saturated and aerobic conditions ( higher DO level), the ammonia-oxidizing rates were 14.20 mg.(L.d)-1 and 13.36 mg.(L.d)-1 and the related conversation rates of NH+4 -N were 93.8% and 88. 2% , respectively. In comparison, under hypoxia and anaerobic conditions (lower DO level), the ammonia-oxidizing rates were 7.82 mg.(L.d) -1 and 5.66 mg.(L.d)-1 and the related conversation rates of NH+4 -N were 51.7% and 37.4% , respectively. The correlation analysis showed that DO concentration was highly significantly positively correlated with the ammonia oxidation rate, and was significantly positively correlated with the AOB diversity index; DO and ammonia oxidation rate had no correlation with indices of AOA community.

In order to clarify the distribution characteristics and risk levels of heavy metals in typical drinking water sources of towns in Dongjiang River Basin, several regular water quality indexes as well as concentrations of Fe, Cu, Mn, Zn, As, Cr, Hg, Pb and Cd were analyzed in the 45 random water samples of 9 towns in the study area. The risk assessment was conducted according to different drinking water types using the environmental health risk assessment model recommended by U. S. EPA. The results indicated that the metal carcinogenic risk is relatively high in this area. The highest carcinogenic risk was from Cr in reservoir water, with the risk for adult people reaching 1.14 x 10(-4) x(-1) and the risk of children reaching 2.14 x 10(-4) x a(-1). Total carcinogenic risk of reservoir, river and underground water exceeded the accepted level of 5.0 x 10(5) x a(-1) as suggested by ICRP while all the non-carcinogenic risk levels were within the acceptable range. The primary control sequence of metal pollution in this area was Cr > As > Pb > Fe > Zn; the risk value of different drinking water sources descended in this order: reservoir > river > underground water > mountain spring.

Using submerged aquatic plant is a cheap and clean technique to remediate heavy metals in wastewaters. Batch experiments were conducted to assess the biosorption characteristics of Pb (II) ions by fresh tissues of Hydrilla verticallata. The biosorption of Pb(II) was examined for single, binary and ternary solutions at different initial concentrations and different pH values. The experimental results showed that the biosorption capacity increased with increasing pH from 2.0 to 6.0. The biosorption value reached 44.65 mg/g when initial lead concentration was 250 mg/L and pH = 5. Both Cu (II) and Zn(II) ions were found to have an adverse effect on the biosorption of Pb(II) for binary and ternary solutions. In Pb-Cu binary metal solution, when both initial concentrations of lead and copper ions were 250 mg/L, the biosorption capacity for lead ions was decreased to 49.29% of that in single lead ion solution. The biosorption equilibrium data for the Pb-Cu binary metal solution fitted the Langmuir competitive model well (R2 = 0.966). The theoretical q(max) value (58.02 mg/g) was in excellent consistent with that obtained experimentally, and the average relative error between calculated q(e) and experimental q(e) values was only 15.6%. Comparison between biosorption of Pb (II) and Cu (II) by H. verticallata in the binary solution could lead to the conclusion that H. verticallata has no preference of Pb(II) over Cu(II).

Based on the concept of ecosystem services and welfare, a definition of a sustainable city is proposed, and a quantitative model to describe sustainable welfare is established. With the analysis of the major issues and driving forces of sustainable city construction in China, the approaches for sustainable city construction are proposed as follows: to promote study on the theory and methodology of sustainable city construction, to set up and perfect institutional and management systems, and to establish a performance assessment system and an effective operation mechanism for sustainable city construction in China.

Combined pollution is more ubiquitous than the single pollution in water and soil environment. Iodine method was used to study the effects of both single and combined pollution of Cd and NH4+ on Hydrilla verticillata and Myriophyllurn spicatum. Results came out that H. verticillata was distinctly stressed at 4.0 mg x L(-1) concentration of NHI4+, oxygen production of photosynthesis and oxygen depletion of respiration all declined, but for M. spicatum ,it was not be stressed. If treated with 0.2 mg x L(-1) Cd, H. verticillata and M. spicatum all were stressed, and H. verticillata was stressed more seriously. Combined pollution of Cd and NH4+ produced cooperative adverse effects on H. verticillata. But for M. spicatum, the stress was less severe comparatively. The main reason was that M. spicatum made of less crude cellulose. So it had less combined pathway with heavy mental than H. wvrticillata. It demonstrated that M. spicatum is suit for pioneer plant comparatively during the process of lake restoration.

Equilibrium sorption isotherms for Cu2+ onto Hydrilla verticillata Royle and Myriophyllum spicatum were studied. Both methods of linear and non-linear fitting were applied to describe the sorption isotherms, and their applicability were analyzed and compared. The results were: (1) The applicability of simulated equation can't be compared only by R2 and chi2 when equilibrium sorption model was used to quantify and contrast the performance of different biosorbents. Both methods of linear and non-linear fitting can be applied in different fitting equations to describe the equilibrium sorption isotherms respectively in order to obtain the actual and credible fitting results, and the fitting equation best accorded with experimental data can be selected; (2) In this experiment, the Langmuir model is more suitable to describe the sorption isotherm of Cu2+ biosorption by H. verticillata and M. spicatum, and there is greater difference between the experimental data and the calculated value of Freundlich model, especially for the linear form of Freundlich model; (3) The content of crude cellulose in dry matter is one of the main factor affecting the biosorption capacity of a submerged aquatic plant, and -OH and -CONH2 groups of polysaccharides on cell wall maybe are active center of biosorption; (4) According to the coefficients qm of the linear form of Langmuir model, the maximum sorption capacity of Cu2+ was found to be 21.55 mg/g and 10.80mg/g for H. verticillata and M. spicatum, respectively. The maximum specific surface area for H. verticillata for binding Cu2+ was 3.23m2/g, and it was 1.62m2/g for M. spicatum.

Economic development and increase of population pressure have caused a series of ecological environmental problems of Erhai Lake. These problems include: (1) Quickening of eutrophication process, (2) Decrease of water level and water resources, (3) Habitat deterioration of lakeside zone, and (4) Overfishing and slow depletion of aboriginal fish. Pollutant loading of Erhai Lake is as follows: COD(Cr) 3 008 t x a(-1), TP 137.31 t x a(-1), TN 1 426.35 t x a(-1). According to the mestrophic target of water quality, loading of nitrogen and phosphorus is far above environmental capacity of Erhai Lake. Erhai Lake is now in a pivotal and hypersensitive period of trophic states change, and the position is very critical. Therefore, some countermeasures to solve the problems are presented as follows: (1) Defining the dominant functions of Erhai Lake, (2) Paying attention to the adjustment of the industrial structure and distribution in the course of urbanization, (3) Setting up lakeside zone reserve, (4) Strengthening the control of tourism pollution, (5) Properly adjusting the water level of Erhai Lake, and (6) Some ecological engineering measures for water resources protection in the basin should be taken through collecting and treating of urban sewages, ecological rehabilitating of the main inflowing rivers, constructing of ecological agricultures and improving of rural environment, ecological restoring of aquatic ecosystem, and soil and water conservation.