P absorption and removal mechanism of new Salix clone (A42)on eutrophic water with different P concentrations.

Phosphorus is the necessary element for plant growth, and its concentration is one of the main indices for water eutrophication. Hence, it is significant to understand how woody plants purify phosphorus in eutrophic water. The purpose of this study is to reveal the P absorption and removal mechanism of Salix matsudana in eutrophic water with different P concentration. We selected new S. matsudana clone (A42) as experimental material and set three levels of P concentration (low P: 0.1, 0.2 mg·L-1; medium P: 1.0, 2.0 mg·L-1, high P: 10.0 mg·L-1), and the floating bed hydroponic experiment was conducted at the greenhouse from July to September, 2017. We found that S. matsudana efficiently removed P in water (removal rate >79% in 21 days). There was a positive correlation between the removal quantity and P concentration in the water. The removal ratio rose at first and then fell with increasing P. Owing to the purification of S. matsudana, the P concentrations ranging from 0.1 mg·L-1 to 1.0 mg·L-1 were reduced to minimum threshold concentration of eutrophication (0.016-0.032 mg·L-1) in seven days. The percentage of phosphorus input in water that assimilated by S. matsudana ranged from 29.0% to 66.9%. The quantity and ratio of assimilated P were respectively positive and negative relation with P concentration. Salix matsudana adapted to eutrophic water with different P concentrations and normally grew during experiment period, with root-shoot ratio being significantly increased with decreases of water P concentrations. The characteristic of phosphorus distribution in plant organs was: stem> leave>root, while the translocation factors (TF) of nitrogen and phosphorus were both greater than 3. When S. matsudana grew in eutrophic water with high phosphorus concentration, the TF of nitrogen and phosphorus significantly increased to 4.53±0.24 and 4.92±0.62 respectively. Our results indicated that S. matsudanais could purify the eutrophic water and it could normally grow. New clone of S. matsudana could effectively absorb phosphorus in the water and accumulated it in the stem, which could reduce secondary pollution. In conclusion, S. matsudana could be used for a short-term treatment on the eutrophic water with low P concentration, while for the long-term treatment it is adapted to eutrophic water with high phosphorus concentrations.

[Characteristics of nitrogen transportation in Castanea mollissima forest around the Fushi Reservoir watershed in north Zhejiang Province, China.] / æµ™æ±Ÿèµ‹çŸ³æ°´åº“é›†æ°´åŒºæ¿æ —æž—åœŸå£¤æ°®ç´ è¿ç§»ç‰¹å¾.

In this study, through setting runoff plots in Chinese chestnut (Castanea mollissima) fo-rest, the runoff water samples were collected and tested from January to October, 2013. Combining with soil nitrogen data before and after the rainy season, we analyzed the characteristics of soil nitrogen transportation in chestnut forest around the Fushi Reservoir watershed in north Zhejiang Pro-vince, China. The results showed that among the 10 surface runoff events of Chinese chestnut fo-rest, there exhibited a significant difference in runoff water volume of each runoff plot, and the maximum amount was 0.51 m3. Nitrogen was the major element associated with nutrient loss in the study region. The concentrations of nitrate nitrogen (NO3--N), ammonium nitrogen (NH4+-N), total nitrogen (TN) andchemical oxygen demend (CODMn) in the runoff water ranged from 0.02-1.87, 0.04-3.53, 1.69-5.33 and 5.30-14.07 mg·L-1, respectively. The water quality indexes were greatly affected by the runoff volume, and the relationship between the amount of nitrogen loss and runoff could be well fitted by using a linear equation. The difference in nitrogen contents of the soil in the upper, middle and lower part of the runoff plots was evident both before and after the rainy season. Moreover, the nitrogen content increased with the increasing altitude, but this trend decreased with increasing soil depth. Comparison of the difference between the four forms of soil nitrogen (NO3--N, NH4+-N, TN and hydrolyzable nitrogen Hydro-N of soil) before and after the rainy season showed that there existed significant differences in Hydro-N and TN, and the average diffe-rence values were 20.21 and 307.49 mg·kg-1, respectively. In this area, there was a great risk of nitrogen loss with runoff, and the potential non-point source pollution in Fushi Reservoir should be concerned.

[Variations of soil microbial community composition and enzyme activities with different salinities on Yuyao coast, Zhejiang, China]. / ä½™å§šæ»¨æµ·ä¸åŒç›ç¢±åº¦åœŸå£¤å¾®ç”Ÿç‰©ç¾¤è½ç»„æˆåŠåœŸå£¤é ¶æ´»æ€§çš„å˜åŒ–.

In October 2015, soil samples with different salinity were collected in a coast area in Yuyao, Zhejiang, and soil microbial community composition, soil catalase, urease activities, as well as soil physical and chemical properties were studied. The results showed that Nitrospira took absolute advantage in the bacterial community, and showed good correlations to total potassium. Cladosporium and Fusarium were predominant in the fungal community. Meanwhile, Cladosporium was related to soil urease and total nitrogen, and same correlation was found between Fusarium and soil urease. Catalase activity ranged from 3.52 to 4.56 mL·g-1, 3.08 to 4.61 mL·g-1 and 5.81 to 6.91 mL·g-1 for soils with heavy, medium and weak salinity, respectively. Catalase activity increased with the soil layer deepening, which was directly related to soil total potassium, and indirectly related to pH, organic matter, total nitrogen and total phosphorus through total potassium. Soil urease activity ranged among 0.04 to 0.52 mg·g-1, 0.08 to 1.07 mg·g-1 and 0.27 to 8.21 mg·g-1 for each saline soil, respectively. Urease activity decreased with soil layer deepening which was directly related to soil total nitrogen, and was indirectly related to pH, organic matter and total potassium through total nitrogen. The total phosphorus was the largest effect factor on the bacterial community CCA ordination, and the urease was on fungal community.

Adsorption of diuron and dichlobenil on multiwalled carbon nanotubes as affected by lead.

The effect of lead on the adsorption of diuron and dichlobenil on multiwalled carbon nanotubes (MWCNTs) was investigated to explore the possible application of MWCNTs for removal of both herbicides from contaminated water. The adsorption of diuron and dichlobenil on MWCNTs at pH 6 was nonlinear and fit the Polanyi-Manes model well. The adsorption of diuron and dichlobenil was closely correlated with specific surface areas and micropore volumes of MWCNTs. An increase in oxygen content of MWCNTs with same diameters and similar surface areas decreased the adsorption of diuron and dichlobenil, while increased the adsorption of lead. Micro-Fourier transform infrared spectroscopic study indicated that hydrogen bonding is a main mechanism responsible for the adsorption of diuron or dichlobenil onto MWCNTs-O. Oxygen containing groups, mainly carboxylic groups, significantly increased the adsorption of lead through the formations of outer-sphere and inner-sphere complexes, which are verified by X-ray absorption spectroscopic measurements. Oxygen containing groups and the presence of lead diminished the adsorption of diuron and dichlobenil. The suppression mechanisms of lead were ascribed to hydration and complexation of lead with carboxylic groups, which may occupy part of surface of MWCNTs-O. The large hydration shell of lead cations may intrude or shield hydrophobic and hydrophilic sites, resulting in a decreased adsorption of diuron and dichlobenil at the lead-complexed moieties.

Effects of copper, lead, and cadmium on the sorption of 2,4,6-trichlorophenol onto and desorption from wheat ash and two commercial humic acids.

The effects of copper (Cu2+), lead (Pb2+), and cadmium (Cd2+) on the sorption of 2,4,6-trichlorophenol (TCP) to and desorption from wheat ash and two commercial humic acids were studied. Copper and Pb2+ diminished the sorption of TCP onto all adsorbents, and made desorption of TCP less hysteretic from ash and German humic acids (GeHA), but more hysteretic from Tianjin humic acids (TJHA). Cadmium had little effect on TCP sorption and desorption. Fourier-transform infra red (FTIR) and X-ray absorption spectroscopy (XAS) in conjunction with fluorescence quenching studies provided insights into the mechanisms of TCP sorption and desorption as affected by Cu2+ and Pb2+, indicating that complexation of Cu2+ and Pb2+ was likely via carboxylic, hydroxylic and phenolic groups of ash, TJHA and GeHA, and that theses same functional groups also reacted with TCP during sorption. In contrast, Cd, a "soft acid", had no effect on the adsorption of TCP. Hydration shells of dense water around adsorbed Cu2+ and Pb2+ ions may also compete with TCP for available surface area. Fluorescence quenching of pyrene verified that for TJHA, Cu2+ and Pb2+ promoted the formation of supramolecular associations with interior hydrophobic regions separated from aqueous surroundings by exterior hydrophilic layers.

Adsorption kinetics, isotherms and thermodynamics of atrazine on surface oxidized multiwalled carbon nanotubes.

The adsorption kinetics, isotherms and thermodynamic of atrazine on multiwalled carbon nanotubes (MWCNTs) containing 0.85%, 2.16%, and 7.07% oxygen was studied. Kinetic analyses were performed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The regression results showed that the pseudo-second-order law fit the adsorption kinetics. The calculated thermodynamic parameters indicated that adsorption of atrazine on MWCNTs was spontaneous and exothermic. Standard free energy (DeltaG(0)) became less negative when the oxygen content of MWCNTs increased from 0.85% to 7.07% which is consistent with the low adsorption affinity of MWCNTs for atrazine.

Adsorption of 2,4,6-trichlorophenol by multi-walled carbon nanotubes as affected by Cu(II).

Adsorption equilibrium of 2,4,6-trichlorophenol (TCP) on multi-walled carbon nanotubes (MWCNTs) was investigated to explore the possibility of using MWCNTs for concentration, detection and removal of TCP from contaminated water. The adsorption of TCP on MWCNTs at pH 4 was nonlinear, reversible and best fit by a Polanyi-Manes model. Oxidation treatment increased surface area and introduced hydrophilic carboxylic groups to the defect sites of MWCNTs, hence increased the sorption of TCP and Cu(II) individually. Cu(II) suppressed the sorption of TCP on oxidized MWCNTs15A, but had little effect on as-grown MWCNTs15. TCP had no influence on Cu(II) sorption to either. The mechanisms of Cu(II) suppression effect on TCP adsorption are ascribed to the formation of surface complexes of Cu(II), which was verified by X-ray absorption spectroscopy. Cu(II) exerts a cross-linking effect of functional groups on adjacent tubes, creating a more tightly knit bundle and suppressing the condensation of TCP in the pore spaces between the tubes. The large hydration sphere around surface complexes of Cu(II) may also intrude or shield hydrophilic sites, leading to the "crowding out" of TCP around the Cu(II)-complexed sites.

Effects of copper, lead, and cadmium on the sorption and desorption of atrazine onto and from carbon nanotubes.

There are currently few studies on the dual effects of metal ions on the sorption of atrazine and conversely of atrazine on metal adsorption on multiwalled carbon nanotubes (MWCNTs). While a number of sorption models were considered to describe the sorption of atrazine on MWCNTs, the Polanyi-Manes model (PMM) fit the sorption isotherms well with the lowest mean weighted square errors. Atrazine was mainly adsorbed onto the surface and micropores of MWCNTs bundles or aggregates. Hydrogen bonding between azo and amino nitrogen of atrazine and functional groups on MWCNTs also occurred. Oxygenated functionalities, mainly carboxylic groups on MWCNTs surface, decreased the sorption of atrazine. Metal cations Cu2+, Pb2+, and Cd2+ diminished the sorption of atrazine depending on the oxygenated functionalities densities. The mechanisms ascribed were due to the formation of surface or inner-sphere complexes of Cu2+, Pb2+, and Cd2+ through carboxylic groups and hydration, which may occupy part of the surface of MWCNTs-O. The large hydration shell of metal cations may intrude or shield the hydrophobic and hydrophilic sites and indirectly compete with atrazine for surface sites, leading to the inhibition of atrazine adsorption around the metal-complexed moieties.