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Liang X.,Key Laboratory for Water Pollution Control and Environmental Safety | Liu J.,Source Point | Liu J.,Zhejiang University | Chen Y.,Key Laboratory for Water Pollution Control and Environmental Safety | And 5 more authors.
Journal of Soils and Sediments | Year: 2010

Purpose: Colloid-facilitated phosphorus (P) has been proved as a significant contributor to eutrophication. Release of colloidal phosphorus (Pcoll) depends on the released soil colloids and their P adsorption abilities, both of which are greatly affected by pH. The aim of the study was to assess the effect of pH in a wide range on Pcoll loss of the top silt loamy soil rich in organic matter and P for the successful description and prediction of P transport. Materials and methods: In batch experiment, soil samples were shaken with deionized water in a wide range of pH from 1.4 to 9.9 for 24 h. Then water-dispersible colloids (WDCs) were extracted by pre-centrifugation, microfiltration, and ultracentrifugation processes orderly and determined gravimetrically. The Pcoll values at each pH were calculated as the difference between the concentration of total P in non-ultracentrifuged and ultracentrifuged samples. The same method was applied for the released colloidal mineral elements (Al, Fe, Ca, Si, Mg, Mn). Colloid morphology and P distribution on colloid surface were directly illustrated by transmission electron microscope (TEM) and scanning electron microscope-energy-dispersive X-ray spectroscopy (SEM-EDS) mapping scanning analyses. Results and discussion: Over pH 4.6-6.0, the released Pcoll was below 5.5 mgkg-1 soil, while up to 66.8 mgkg-1 soil and 28.5 mgkg-1 soil at pH 1.4 and 9.9, respectively, indicating that both high and low pH values enhanced the mobilization of Pcoll. At the low pH, the potential loss of Pcoll mainly resulted from the dissolution of inorganic encasing cement such as Al oxides and clay mineral. However, besides electrostatic repulsion, dissolution of organic coating at high pH enhanced the Pcoll release as revealed by the SEM-EDS results. The P was heterogeneously distributed on the WDCs and might be associated with soil organic matter, Al oxides, Fe oxides (oxyhydroxide), and clay mineral at the low pH, while mainly with Fe oxides and less clay mineral at the high pH. Conclusions: Both high and low pH enhanced colloid and Pcoll releases. This study first visually revealed that the dissolution of organic cement at high pH enhanced the release of WDCs and their facilitated Pcoll release. The exceptional loss risk of Pcoll may be caused by soil acidification due to the dissolution of inorganic cements, especially in Al-rich soils, and by the enhanced high soil pH due to the dissolution of organic coating in the organic matter-rich soils. © 2010 Springer-Verlag.

Li L.,Zhejiang University | Liang X.-Q.,Zhejiang University | Li H.,Zhejiang Academy of Agricultural Sciences | Ji Y.-J.,Key Laboratory for Water Pollution Control and Environmental Safety | And 5 more authors.
Pedosphere | Year: 2015

Soil phosphomonoesterase plays a critical role in controlling phosphorus (P) cycling for crop nutrition, especially in P-deficient soils. A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activities, kinetics and thermodynamics during rice growth stages after consistent swine manure application, to understand the impacts of swine manure amendment rates on soil chemical and enzymatic properties, and to investigate the correlations between soil enzymatic and chemical variables. The experiment was set out in a randomized complete block design with three replicates and five treatments including three swine manure rates (26, 39, and 52 kg P ha-1, representing low, middle, and high application rates, respectively) and two controls (no-fertilizer and superphosphate at 26 kg P ha-1). The results indicated that the grain yield and soil chemical properties were significantly improved with the application of P-based swine manure from 0 to 39 kg P ha-1; however, the differences between the 39 (M39) and 52 kg P ha-1 treatments (M52) were not significant. The enzymatic property analysis indicated that acid phosphomonoesterase was the predominant phosphomonoesterase in the tested soil. The M39 and M52 treatments had relatively high initial velocity (V0), maximal velocity (Vmax), and activation grade (lgNa) but low Michaelis constant (Km), temperature coefficient (Q10), activation energy (Ea), and activation enthalpy (δH), implying that the M39 and M52 treatments could stimulate the enzyme-catalyzed reactions more easily than all other treatments. The correlation analysis showed that the distribution of soil phosphomonoesterase activities mainly followed the distributions of total C and total N. Based on these results, 39 kg P ha-1 could be recommended as the most appropriate rate of swine manure amendment. © 2015 Soil Science Society of China.

Chen L.,Zhejiang University | Chen L.,Source Point | Yu C.,Hangzhou Normal University | Shen C.,Zhejiang University | And 8 more authors.
Journal of Soils and Sediments | Year: 2010

Purpose: The primitive recycling of electronic waste (e-waste) in developing countries is causing serious environmental pollution. The objective of this study was to determine the contamination and toxicity of surface sediment of Nanguan River, which runs through the e-waste recycling area of Taizhou, East China. Materials and methods: Surface sediments were collected from Nanguan River, including one from the control site, four near the household workshops, and two near the industrial parks. Levels of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals/metalloid (Ni, Pb, Cd, Cr, Zn, Cu, Hg, and As), which are most widely detected in e-waste contaminated surroundings, were determined. Acute toxicity and genetic toxicity were evaluated by luminescence inhibition assay in luminescent bacterium Vibrio qingaiensis sp. nov. (Q67) and Vicia faba roots tip micronucleus assay, respectively. Results and discussion: The surface sediment has been seriously contaminated by PCBs, PAHs, and heavy metals/metalloid due to the e-waste disassembly process. Significant acute and genetic toxicity of the sediments presented a big threat to the aquatic life and human health through food chain, as the river is an extent water source for local residents. Conclusions: The environmental issue of e-waste recycling is emergent and measures should be taken to mitigate the adverse impacts of e-waste disassembly. © Springer-Verlag 2010.

Chen L.,Zhejiang University | Chen L.,Key Laboratory for Water Pollution Control and Environmental Safety | Shen C.,Zhejiang University | Shen C.,Source Point | And 4 more authors.
Environmental Science and Pollution Research | Year: 2012

Background and purpose: The ubiquitous dissolved organic matter (DOM) is actually not inert as we always think, and the hormone-like effects of DOM have been reported. The objective of this study was to investigate the estrogenic effects of DOM and its impact on the activity of the natural estrogen 17β-estradiol (E2). Materials and methods: DOM of three different sources, HA sodium salt, Suwannee River natural organic matter (NOM), and Nordic Reservoir NOM, were used. The estrogenic activity was detected by using the yeast estrogen screen (YES) assay. Estrogenic effects of DOM without and after solar irradiation were tested. Influences on the action of E2 by DOM were also investigated. Results: No direct estrogenic effects of the DOM used were observed in the YES assay. However, the estrogenic activities after 24 h of irradiation increased to 0. 0288, 0. 0178, and 0. 0195 μM of E2 equivalents for HA sodium salt, Suwannee River NOM, and Nordic Reservoir NOM, respectively. After incubation of DOM, the estrogenic activity of E2 was increased by low concentrations (8. 33 and 83. 3 μM) of DOM while decreased by higher concentrations (8. 33 × 102 and 8. 33 × 103 μM) of DOM. Conclusions: Though direct estrogenic effects of DOM were not observed, increase in the estrogenic activity of DOM after irradiation was significant. DOM shows amphoteric influence on the natural estrogen E2, which depends on the concentration of DOM used. Because of its ubiquity, DOM may be of great ecological significance, playing an important role in regulating the reproduction of aquatic organisms. © 2011 Springer-Verlag.

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