The accumulation and volatilization of Se by algae in surface water are important parts of the biogeochemical cycle of selenium but are also variable and complex. Experiments with 5-8 day of exposure under various temperatures, solution pH values, lighting regimes, and different initial Se concentrations were carried out to study the change in Se accumulation and volatilization behavior of algae. The study showed that algae accumulated and volatilized more Se under harsher environments, such as a lower pH, a shorter lighting time, and a higher Se load. The maximum average daily volatilization rate of Se was 234 ± 23 μg Se (g algae·d)-1, much greater than the values of previous studies. Therefore, in some Se-polluted water environments, when the pH of lakes is acidic, Se emissions to the atmosphere are much higher than currently estimated. Both the accumulation rate (Raccu) and volatilization rate (Rvol) of Se by algae were significantly negatively correlated with final pH, final OD, and residual Se in solution (Cres). Moreover, multiple linear regression equations were used to estimate the rates of Se accumulation and volatilization. This study provides theoretical basis data to quantify the contribution of selenium metabolism by algae to selenium biogeochemistry and a technical reference for the treatment of Se-containing wastewater.

Land use is an effective way to reduce carbon emission in the recycling process of municipal sludge compost; meanwhile, heavy metals (HMs) in the sludge can be phytoextracted by ornamental plants. As an eco-friendly soil amendment, citric acid (CA) has been reported to be of great potential aid to phytoremediation, and its effect on ryegrass ( Lolium perenne L. ) extraction of HMs (Zn, Ni, Pb, Cu, and Cd) from municipal sewage sludge compost-amended (MSSC) soils has been investigated through pot experiments in the study. The growth of ryegrass was significantly promoted under 2 and 4 mmol kg −1 CA treatments. The concentrations of HMs in MSSC soil after 45-day planting were significantly reduced ( p < 0.05 ), and they were further reduced except for Cu while CA treated. The acid-extractable fraction of HMs in the soil was increased significantly as CA treated, and further improvement could be found when CA dose increased, which was due to the decreased soil pH and the complexation of CA with metal ions. The phytoremediation factor (PRF) was proposed to assess the phytoremediation efficiency, which was obtained as a ratio of the product of the biomass and metal concentration of plant shoot between the CA-treated group and the control group. When the CA dose was 6 mmol kg −1 , the average PRF of five heavy metals reached 2.29, and Cd was the highest (3.72), demonstrating that CA had great promotion on phytoremediation of heavy metals. This study made a contribution to the research of phytoremediation in sludge land use by demonstrating ryegrass as an ideal bioaccumulator for heavy metals, especially for Cd.

The development of phytoremediation by garden plants is an effective way to deal with the dilemma of municipal sewage sludge disposal. In this study, two ornamental plants were used as phytoremediation plants to rehabilitate heavy-metal-contaminated municipal sewage sludge in field experiments, and the role of exogenous phytohormone IAA was also tested. Ornamental plants Loropetalum chinense var. rubrum (L. rubrum) and Rhododendron pulchrum (R. pulchrum) adapted well to the artificial soil made of municipal sewage sludge, and the concentrations of Cu, Zn, Pb, and Ni were decreased by 7.29, 261, 20.2, and 11.9 mg kg−1, respectively, in the soil planted with L. rubrum, and 7.60, 308, 50.1, and 17.7 mg kg−1, respectively, in the soil planted with R. pulchrum, accounted for 11–37% of the total amounts and reached significant levels (p < 0.05), except Cd. The concentration of Pb in all parts of the two ornamental plants was increased, as well as most heavy metals in L. rubrum root. As a result, three months after transplant, the phyto-extraction amounts in L. rubrum were 397, 10.9, and 1330 μg for Ni, Cd, and Pb, respectively, increased by 233% to 279%. The phyto-extraction amount in R. pulchrum were 1510, 250, and 237 μg for Zn, Pb, and Cu, respectively, increased by 143% to 193%. These results indicated a potential to remediate heavy metals of the two ornamental plants, especially L. rubrum. The results of correlation analysis implied that the interaction of heavy metals in the plant itself played an important role in the uptake of heavy metals. This seemed to explain why applying IAA in the experiment had little effect on plant growth and phytoremediation of heavy metals. This study provided a green and feasible idea for the proper disposal of municipal sewage sludge.

In the presence of dissolved organic matter, the mechanism of algal bioaccumulation of different metals is complex, and its significance goes far beyond the alga-metal binary system. In the presence of 10 and 20 mg L-1 fulvic acid (FA), the maximum tolerance concentrations of Chlorella pyrenoidosa to Ni were 0.25 and 0.26 mmol L-1, and to Zn were 0.62 and 0.68 mmol L-1, respectively. Within the maximum tolerance concentration ranges, the bioaccumulation behaviors of Ni and Zn were systematically compared in the presence of FA. The presence of FA shortened the adsorption equilibrium time and decreased the maximum bioaccumulation capacity of Ni and Zn. The bioaccumulation mechanism of Ni by C. pyrenoidosa was more inclined to monolayer adsorption, while the bioaccumulation mechanism of Zn was more inclined to multilayer adsorption. More details were revealed after the bioaccumulated metals were separated into adsorption and internalization states by 0.01 M EDTA elution. The presence of FA decreased more adsorbed Zn than the adsorbed Ni, due to the different competitive roles of FA in the ternary system of Ni and Zn, but the presence of FA increased the internalized Ni might due to the stronger complexation of Ni-FA. This research indicated that algae had unique bioaccumulation mechanisms for different metals in the presence of FA, which is of great significance to accurately evaluate the ecological risk posed by heavy metals.

Trace metal pollution in soils is one of the universal environmental problems in the world. Phytoremediation is a green, safe, ecological, and economic method to achieve continuous reduction of soil pollutants. Turfgrass is a plant with great landscape value and has considerable biomass when used for remediation of trace metal contaminated soil. However, its remediation ability needs to be improved in future application. The combined application of turfgrass, citric acid (CA) and auxin (gibberellin, GA(3)) were applied in the phytoremediation of an artificial nutritive soil derived from sludge, and a field scale orthogonal experiment (L-9) was conducted to understand the interaction effect and obtain the optimum phytoremediation. Experimental results showed that the types and cultural patterns of turfgrass mainly determined plant height, root length and trace metal concentration in turfgrass, however CA treatment was prone to increase the aboveground biomass and the concentrations of most trace metals in turfgrasses, especially the concentration of Ni in turfgrass. GA(3) spraying significantly increased the concentration of Cd in turfgrass. The culture patterns of turfgrass played 42.4% influence on acid-extractable Cd, while CA applying had 53.8% influence on the acid-extractable Ni. The annual phytoextraction amount of trace metals based on five mowing a year were proposed to assess the remediation ability of treatments, which of the combination treatment (T3, intercropping Zoysia matrella and Lolium perenne, and applying 400 mg kg(-1) CA and 30 mg kg(-1) GA(3)) were 1.6-2.1 times higher CK group. This research provides technical reference for intercropping turfgrass for remediation of trace metals in sludge-derived nutritive soil.

The accumulation and volatilization of Se by algae in surface is an important part of the biogeochemical cycle of selenium, but also variable and complex. A 5-day exposure time at 25 °C was finally determined through 8-day exposure observations at three temperatures. The single factor experiment showed that the harsher the environment (lower pH, less lighting regime, higher Se load), the more Se the algae tended to accumulate and volatilize. The maximum average daily volatilization rate of Se was obtained at 234 μg (g d) −1 , much greater than 156.4 μg (g d) −1 reported in previous studies. The multiple linear regression equation of the daily accumulation rate was R accu =27.7-2.06 pH-0.268 C res , R 2 =0.963, while that of the volatilization rate was R vol =181-108 OD-4.37 C res , R 2 =0.950. This study provides theoretical basis data to quantify the contribution of selenium metabolism by algae to selenium biogeochemistry and a technical reference for the treatment of Se containing wastewater.

The combined application of turfgrass intercropping, citric acid and auxin were applied in the phytoremediation of artificial soil and optimized through the field scale orthogonal experiment (L9) to understand the interaction mechanisms and obtain the optimum phytoremediation effect. Experimental results showed that plant height, root length and heavy metal concentration in turfgrass were mainly determined by the grass species and planting strategies, while the aboveground biomass were significantly increased with CA treatment. In addition, CA treatment significantly increased the concentration of Ni in turfgrass, while auxin spraying significantly increased the concentration of Cd in turfgrass. The fraction analysis of BCR showed that treatments increased the proportion of the residual Zn, Pb, and Cu, but decreased the proportion of the residual Ni and Cd. Furthermore, turfgrass planting strategy showed dominant influence on BCR1-Cd, BCR1-Zn, and BCR1-Pb (42.4% - 56.1%), while CA applying had the greatest influence (53.8%) on the BCR1-Ni, and auxin spraying on BCR1-Cu. For the assessment of remediation ability, CA applying had predominant influence on BCF and the annual phytoextraction amount of trace metals. This paper provides technical reference for phytoremediation of trace metals in sludge-derived nutritive soil.

The West Lake is a World Heritage site in the West Lake watershed in eastern China. In this study, the hydrogeological and dual isotopic approaches were integrated to evaluate the seasonal and spatial variations of nitrate (NO3(-)) in the West Lake watershed, and to characterize NO3(-) sources and transformations. The results revealed that the geochemical facies of the water samples were dominated by Ca(2+)+Na(+)-HCO3(-)+SO4(2)(-) in the surface water and transfer water, Ca(2+)+Na(+)-HCO3(-) and Ca(2+)+Na(+)-SO4(2-) in the groundwater, which most likely reflect natural reactions and anthropogenic inputs. About 13% of the groundwater samples containing NO3(-) exceeded the World Health Organization (WHO) standard of 10 mg N L(-1). NO3(-) was the dominant form of total nitrogen (TN) and was the main surface water contaminant in the West Lake watershed. The δ(15)NNO3 and δ(18)ONO3 values indicated that the dominant NO3(-) sources in surface water were soil nitrogen (soil N) and chemical fertilizers, while the main NO3(-) sources in groundwater were soil N from the forest, chemical fertilizers and manure in the tea garden, domestic sewage from the small, old residential area in the forest as well as urban areas. The distribution of NO3(-) in groundwater was strongly influenced by land use. Results also suggest that there was significant nitrification in surface water and groundwater in the West Lake watershed, and that there were also denitrification processes in groundwater. The annual net fluxes of TN, NO3(-), and NH4(+) into the West Lake were 2.0×10(4), 4.0×10(3), and 1.31×10(4) kg as N, respectively.

Water transfer from the Qiantang River to the West Lake, Hangzhou City, China, has been performed since 1985 to improve the lake water quality. This study was conducted to assess the water quality and estimate the pollutant fluxes from different sources into the lake to enable better water quality management. Monthly variations in water quality variables, namely chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), total phosphorus (TP), total nitrogen (TN), ammonium nitrogen (NH4 +-N), and nitrate nitrogen (NO3 −-N), and flow were analyzed for 1-year period from April 2012 to March 2013. The pollutant fluxes into the lake were mainly contributed by the water transferred from the Qiantang River, followed by runoff and rainfall. The results showed that the annual influxes of COD, BOD5, TP, TN, NO3 −-N, and NH4 +-N into the lake were 1,595.3, 255.8, 8.2, 576.0, 360.3, and 84.2 t, respectively, while the annual fluxes out of the lake were 2,204.6, 301.8, 7.1, 336.5, 191.6, and 36.1 t, respectively. The annual net flux of pollutants in decreasing order was TN > NO3 −-N > NH4 +-N > TP > BOD5 > COD, and nitrogen was found to be the major pollutant in the West Lake. It is recommended that the water transferred from the Qiantang River should be treated by chemical precipitation as well as denitrification technology to reduce the nitrogen concentration.

Effect of natural nontoxic biopolymer chitosan on seed germination, seedling growth and clubroot control in Chinese cabbage were evaluated. Results showed that seed germination of Chinese cabbage was unaffected while seed germination of rape and the seedling growth of Chinese cabbage were differentially affected by the two kind of chitosan at different concentrations. However, chitosan significantly inhibited the resting spores' germination of the clubroot pathogen, and reduced the disease index of clubroot of Chinese cabbage and the number of the resting spores in soil compared to the control regardless of chitosan type and concentration as well as the application method. In general. the inhibitory effect in the resting spores' germination and the number in soil increased with the increase of chitosan concentration regardless of chitosan type. Overall, the results indicated that the two kinds of chitosan solutions had a potential in controlling clubroot on Chinese cabbage.

Influences of carbon adaptation on antagonistic activities of three Pseudomonas aeruginosa strains V-4, V-7 and V-10 against Fusarium oxysporum f. sp. melonis were determined in this study. Results from this study showed that the P. aeruginosa strains and their adapted strains significantly inhibited the growth of mycelium of F. oxysporum f. sp. Melonis, while in vitro inhibition of P. aeruginosa on the mycelial growth was unaffected by carbon adaptation. In general, the growth of strain V-4 and its antagonistic ability was unaffected by carbon adaptation. However, the growth of the adapted strains V-7-C and V-10-C was superior to the corresponding parental strains when root exudates were used as a sole carbon source. In addition, the adapted strains V-7-C and V-10-C caused a more decrease in Fusarium infection of melon compared with the corresponding parental strains. Overall, this study revealed that adaptation culture of P. aeruginosa strains on carbon-limited media may play an important role in the inhibition of Fusarium wilt of melon seedlings although the effect of carbon adaptation may depend on the test strain.

The potential of biofilm formation of 16 Paenibacillus strains and their inhibitory effect against bacterial wilt of tomato seedlings were examined in this study. The crystal violet assay indicated that all strains of Paenibacillus except strain MB02-1202 formed biofilm after 96 and 144 h of incubation while there was not significant difference in biofilm formation between strains of Paenibacillus polymyxa and strains of Paenibacillus macerans. However, the increase level of biofilm formation was associated with the increase of the incubation time and the initial inoculum density. In addition, all Paenibacillus strains except strain MB02-428 reduced wilt incidence in tomato seedlings inoculated with Ralstonia solanacearum while the cell numbers of R. solanacearum in rhizosphere soil was reduced by all Paenibacillus strains compared to the pathogen control. In general, most strains of Paenibacillus were able to both form biofilm and protect tomato seedlings from bacterial wilt, indicating that biofilm formation may play an important role in the biocontrol of Paenibacillus. This is first study regarding the relationship between in vitro biofilm formation ability of Paenibacillus strains and their inhibitory activity against R. solanacearum.

The in vitro antibacterial properties of chitosan solution and its effect in protecting silkworms from bacterial septicemia disease were evaluated. The results showed that chitosan solution at concentrations of 0.01, 0.05 and 0.10 mg/ml exhibited strong antibacterial activity against two strains of Serratia marcescens. The antibacterial activity of chitosan solution against strain ZJS0801 of S. marcescens increased with the increase of chitosan concentration, while the antibacterial activity against strain ZJS0802 of S. marcescens was unaffected by chitosan concentration. The antibacterial activity of 0.10 mg/ml chitosan solution against S. marcescens increased with the increase of incubation time regardless of the tested strains. The mortality of larvae inoculated with the mixture of S. marcescens ZJS0801 and chitosan solution was significantly reduced compared to bacteria alone. In addition, the larvae mortality of silkworms inoculated with S. marcescens ZJS0801 was significantly reduced when silkworm larvae were fed on mulberry leaves treated with chitosan solution. Overall, the results indicated that chitosan solution had the potential for control of bacterial septicemia disease of silkworms.