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Zhang M.,Zhejiang University | Zhang M.,Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2010

Contaminated surface dust is a worldwide problem, and concentration and mobilization of contaminants in the surface dust are among the most critical issues in environmental risk assessment. Urban coach stations are one of the most important public places where surface dust has a direct effect on people's health as a result of respiration, because of the small size of the particles and the effect of heavy metals on biochemical mechanisms, and especially because the metals can be bio-accumulated. In order to investigate the accumulation, possible sources and availability of heavy metals in the surface dust at different types of urban coach stations, 73 surface dust samples were collected from each of 73 coach stations in Zhejiang Province for characterization of the particle composition and accumulation of Pb, Zn, Cu, Cd, Cr, Ni, Hg, As, Se, Al, Fe, Mn, and Co. Chemical forms of Pb, Zn, Cu, Cd, Cr, Ni, Hg, Fe, Mn, and Co in representative samples were also characterized by a sequential extraction technique. Multivariate statistical techniques, including correlation analysis, principal component analysis (PCA), and cluster analysis, were applied to identify possible sources of heavy metals in the surface dusts and classify the coach stations in term of chemical components of the surface dusts. The particle analysis showed that coarse particles with size of >100μm composed the majority of the surface dusts in the urban coach stations in Zhejiang Province, and suggested that the surface dusts mostly originated from soil, construction materials, and garbage near the coach stations, and atmospheric deposition made little contribution to the surface dusts. The mean total concentrations of Pb, Zn, Cu, Cd, Cr, Ni, Hg, As, and Se in the surface dusts were 287.1, 424.0, 172.8, 1.21, 122.3, 54.4, 0.71, 16.00, and 2.07 mg · kg-1, respectively, and were significantly higher than background values of the elements in the soils of the Zhejiang, indicating that the surface dusts were heavily contaminated with the heavy metals. Three significant components were extracted by PCA, explaining 89.77% of total variance of the 13 elements. Aluminium, Fe, Mn, and Co were associated with lithogenic components and originated from soil particles (natural source). Lead, Zn, Cu, Cd, Cr, and Ni were possibly related to traffic exhaust and industrial pollution. Mercury, As, and Se were originated from multiple activities including coal combustion, traffic exhaust, and industrial pollution. Based on the chemical components of the surface dusts, the 73 coach stations could be classified into 5 groups. Chemical speciation results showed that the chemical forms of the metals in surface dusts varied with the elements, and the potential availability of the metals decreased in the sequence Zn, Mn, and Cd > Cu, Ni, and Hg > Pb, Cr, and Fe.

Li J.,Zhejiang University | Li J.,Zhejiang Provincial Key Laboratory of Information Network Technology | Zeng L.,Zhejiang University | Zeng L.,Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition
Journal of Physics A: Mathematical and Theoretical | Year: 2010

We discuss in detail the effects of the multi-time-delayed feedback driven by an aperiodic signal on the output of a stochastic resonance (SR) system. The effective potential function and dynamical probability density function (PDF) are derived. To measure the performance of the SR system in the presence of a binary random signal, the bit error rate (BER) defined by the dynamical PDF is employed, as is commonly used in digital communications. We find that the delay time, strength of the feedback, and number of time-delayed terms can change the effective potential function and the effective amplitude of the signal, and then affect the BER of the SR system. The numerical simulations strongly support the theoretical results. The goal of this investigation is to explore the effects of the multi-time-delayed feedback on SR and give a guidance to nonlinear systems in the application of information processing. © 2010 IOP Publishing Ltd.

Shen Y.-N.,Zhejiang University | Lu J.,Zhejiang University | Chen J.-H.,Zhejiang University | Chen D.-J.,Zhejiang University | Shi Y.-M.,Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition
Huanjing Kexue/Environmental Science | Year: 2010

An inversion formula for the export loads of nonpoint sources pollution in headwater area was established based on one-dimensional water quality equation, and it was used to calculate the pollution loads for tributaries in the headwater catchment of Laohutan Reservoir, in Huzhou City, Zhejiang Province of China. Monte Carlo method was adopted to determine the sensitivity about each input parameter in the inversion formula. Because each sensitive parameter can be measured directly in the inversion formula, so that this approach can decreased calculation error, which is often caused by the parameter estimation. Furthermore, the inversion formula can be adopted to calculate pollution loading on any time scale. Monthly nonpoint sources pollution export loads in 2007 were calculated by the model in the research catchment. Results showed that pollution loads in stream were significantly positive related with flow rates (r>0.90, p<0.01), and the flow rate was the most sensitive factor in the model, followed by the nutrient concentration and background concentration at the stream end. While, comprehensive degradation coefficient and flow velocity contributed very little influence to the model uncertainty.

Zhang M.,Zhejiang University | Zhang M.,Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition | Zhang H.,Zhejiang University
Journal of Environmental Sciences | Year: 2010

To evaluate the effects of long-term applications of phosphorus fertilizers on mobility of dissolved organic matter (DOM) and heavy metals in agricultural soils, a sandy soil and a loamy soil were spiked with ammonium phosphate at application rates of 0, 25, 50, 100, 250, and 500 mg P per kilogram of soil. A series of 15-cm long soil columns were constructed by packing incubated soils of varying concentrations of P. The soil columns were consecutively leached by simulated rainfalls for six cycles. The contents of water extractable organic carbon in both sandy and loamy soils increased significantly with increasing rates of P applications. Relatively high rates of P applications could induce a marked increase in DOM concentrations in the leachates, the effects were larger with the sandy soil rather than with the loamy soil. Applications of P changed the partitioning of trace metals in the soil solids and the soil solutions. The increased P application rates also seemed to elevate the leaching of Cu, Cd, and Zn from soils. The concentrations of Cu, Cd, and Zn in the leachates were positively correlated with DOM, probably due to the formation of metal-DOM complexes. In contrast, Pb concentrations in the leachates were negatively correlated with DOM, and decreased with increasing rates of P applications. The boosted leaching of DOM induced by high rates of P applications was probably due to the added phosphate ions competing for adsorption sites in the soil solids with the indigenous DOM. © 2010 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.

Zhang M.-K.,Zhejiang University | Zhang M.-K.,Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition | Chang Y.-C.,Zhejiang University
Huanjing Kexue/Environmental Science | Year: 2013

By comparing the current quality investigation data of cultivated soils in Zhejiang province with the past data, changing characteristics of organic matter and pH value of the soils in this province over last 50 years were analyzed. The results showed that content of organic matter and pH value of the cultivated soils changed greatly during past 50 years, and the changes varied with historical periods and soil types. From 1958 to 1980s, accumulation of soil organic matter was obvious, soil organic matter increased averagely by 40.34%, and the mean pH increased slightly by 0.05 of pH unit. From 1980s to 2008, the mean content of organic matter in paddy soils decreased by 5.58%. The changes of soil organic matter varied with distribution zones of the paddy soils. The mean content of organic matter of paddy soils in valley plain increased with time, and those in plain with water network, hilly area and coastal plain decreased with time. The mean contents of organic matter in fluvio-aquic soil and coastal saline soil in the year 2008 were 29.48% and 14.60% respectively higher than those in 1980s. As compared with those obtained at 1980s, the cultivated soil in this province have been significantly acidified in the past thirty years, the mean pH value declined by 0.25 of pH unit, and the decline of pH value of paddy soils was greater than those of fluvio-aquic soil and saline soil. Changes in fertilization structure and conversion of paddy fields to upland were thought as main causes of the changes in both soil organic matter and pH value.

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