Advanced Materials Research Vol. 878

Abstract: With the rapid economic development, China is experiencing increased land contamination and lead poisoning problem in recent years, which is no longer restricted to isolated incidents and locations. There is an urgent need to remediate the lead contaminated soils to protect the publics health. However, contaminated land remediation and determination of remediation target value has been neglected for years. In order to accommodate uncertainties within the conservative point estimation of remediation target value for lead contaminated soils, Monte Carlo simulation technique is integrated into the traditional calculation model from a probabilistic perspective. Risk-based remediation target values for lead contaminated soils of different land use types (including school/hospital, residential, business and industrial use) are developed preliminarily. Furthermore, this study highlights the necessity to determine the remediation target value on the basis of actual (i.e. site-specific) risks to humans and, besides, actual risks due to contaminant migration.

Abstract: Contamination control and remediation of groundwater is one of the hotness points in environmental protection field. Groundwater contamination numerical simulation is widely used for groundwater contamination transportation. In this paper, we constructed an indoor sandbox to conduct hydraulic control experiment and tracer experiment. We also set up groundwater flow model and solute transport model by computer and chose the model's key parameters for sensitivity analysis. The results indicated that the sensitivity of hydraulic conductivity was highest, which was the key parameter in the groundwater flow model. The sensitivity analysis of solute transport model parameters showed that sensitivity from large to small was: longitudinal dispersion, porosity and hydraulic conductivity. This study can obtain the main parameters in groundwater simulation model and is helpful for the construction of groundwater contamination migration model.

Abstract: Contaminated sites remediation is one of the hot points in environmental protection fields. Therefore, an important research project is how to expediently determine the bound and level of pollution of contaminated sites. This may help to decide on a timely and accurate rescue plan so as to minimize the costs and to improve the effect of restoration. This is also the basis of contaminated sites remediation acceptance. There are many influencing factors to confirm the remediation areas on contaminated sites. Studies show that three-dimensional interpolation method is effective tool to delimit the pollution scope. Different three-dimensional interpolation methods have different results in contaminate distribution prediction and directly affect the boundary of contamination. This paper selects one specific case with heavy metal lead contamination to study three-dimensional interpolation methods. The three-dimensional stratigraphic model is established for uncertainty analysis and error analysis in the grid through KrigingIDW(Shepard) and nearest neighbor interpolation method. Results show that 40m*40m grids have the highest accuracy of stratigraphic simulation. Nearest neighbor interpolation method is most suitable for stratigraphic model building. Kriging interpolation method is more suitable for constructing three-dimensional pollutant prediction model. On the basis of above, this text established one distribution prediction model of soil lead contamination, and calculated the contaminated earthwork quantity under different remediation goals. Finally, the paper achieved three-dimensional visualization of the site soil contamination. This study can be directly applied to the actual site remediation decision process, and is helpful for the contaminated sites evaluation and restoration in the future.

Abstract: Remediation of hydrophobic organic contaminants (HOCs) in soils and groundwater has becoming an issue of extensive concern around the world. Surfactant enhanced remediation has been suggested as a promising technology for abating such contaminants, and the nonionic surfactants have often been employed based on their high solubilization capabilities and comparatively low critical micelle concentrations (CMCs). A major problem arises after soil washing because the collected surfactant-containing wastes must be properly disposed or treated. In this study, 13 different soil with different basic properties were artificially contaminated with pentachlorophenol (PCP) and washed with TX100, a widely used nonionic surfactant. The properites of the as-required 13 washing effluents were test, and photocatalystic degradation of PCP using commercial P25 TiO₂ was carried out. The degradation curves were fitted to the pseudo-first-order kinetic law, and simple correlation coefficients were obtained between the first-order rate constants k and washing effluents properties. The results obtained indicated that the degradation rate of PCP mainly depended on the concentration of PCP and TX100 in the wasted effluents, while othe substances washed out from soil showed very limited impact on the photocatalysis procedure.

Abstract: A total of 2668 surface soil samples (-0.5 m ~ 0 m) and 637 sub-layer soil samples (-1.0 m ~ -0.5 m) were collected from a contaminated site with an area of 26.19 hectares and analyzed the concentration of arsenic, so as to get the spatial distribution of arsenic concentrations in the soil contaminated by highly toxic As-chemicals. The results indicated that spatial correlation of arsenic content in surface soil was moderate. The optimal semivariogram model was the exponential model, and the best interpolation model was simple Kriging interpolation. The arsenic content of sub-layer was similar to that of surface soil in space structure, but weakly correlated. Analysis on the arsenic content in vertical sections showed that contamination was mainly concentrated in surface soil. The arsenic content in most of the collected samples reduced as the soil layer depth increased. Spatial variability of arsenic could be significantly affected by anthropogenic factors such as excavation & destruction of highly toxic As-chemicals and farming.

Abstract: Persistent organic pollutants (POPs) has the typical features of persistence, long-range transport, biological accumulation and high toxicity, so that POPs contaminated sites have posed much risk to human health and environment, which is in urgent need of improvement. At present, there are many international advanced remediation methods and engineering practices, but it has not formed the mature remediation technology system in China. Through studying the international concrete examples of remediation technologies, the paper completely reviews the attributes and characteristics of various technology methods, puts forward preliminary technology management system for the remediation of POPs contaminated sites, then provides methodology process for screening the treatment technologies for POPs contaminated sites in China.

Abstract: Municipal solid waste (MSW) landfills are one of main sources of anthropogenic methane emissions in China, and methane has been predicted to be the most significant greenhouse gas after 2030. In landfills, oxidation can take place naturally with methane migrating through the landfill cover. The value of fraction of methane oxidation recommended by the US EPA is 10%, which, however, is being challenged with more and more field measurement data from the Europe and the US. The characteristic of MSW in China is extremely different from that in the US, probably resulting in distinct differences in both methane generation and oxidation. The objective of this study was to determine the fraction of methane oxidized at MSW landfills in China and its spatial and temporal variations. Stable isotope technique was applied to determine the fraction of methane oxidized. The results showed that the fraction of methane oxidized where MSW was covered by soil ranged from 6.3% to 100% in Northeast China and 31% to 100% in North China. Methane oxidation could hardly occur in the operating surface. Besides, soil cover always had a high methane oxidation efficiency in summer. The fractional oxidation of methane in summer was more than 2 times than that in winter. All over the year, with the sampling depth decreasing, the fraction of methane oxidation of soil cover increased.

Abstract: This research was conducted to understand the characteristics of arsenic (As) accumulation in Pteris vittata L. for remediation the soil contaminated by highly toxic As-chemicals. After Pteris vittata L. grown in different test soil for 3 months in the greenhouse, the determination result shown that the hyperaccumulator not only could accumulate large amounts inorganic arsenic and little organic arsenic, but also the majority of As was found in the fronds (over 90% of total As-content in the whole plants, average value, mg) .Furthermore, if the plants grown for different time in the same As-concentrations soil, the maximum As-concentrations (mg/kg) of pinnas, rachis and fronds all came forth at the end of the second month, but the maximum total As-content of fronds at the third month, so we could enhance the effects of remediation by harvested the fronds for per 3 months. The As-concentrations and the average total As-content of per plant and the As removal rate of the rhizosphere also could demonstrate the conclusion by comparing the harvested the plants per 3 months or not in 6 months.

Abstract: Waste separation bins that are mainly categorized into recyclable and non-recyclable are being installed almost everywhere in China. It is notable that China is pushing hard to get the public involved in garbage separation and recycling. As an ethnographic research, this paper provides social and cultural explanations of why the roles of these newly designed bins are extremely limited. Explanation of such limitation is deeply concerned with, first, the beliefs and knowledge about recycling of the general publics, and more importantly, the history and hard-to-be-changed culture of informal recycling involving garbage pickers in China. As a foreign Chinese, the author has been running around Beijing and other cities in China to explore into the behind the scene Chinese informal garbage collection system. Using a series of informative social surveys, interviewing the public and personal observation, the paper illustrates and discusses the social challenges and current dilemmas China is facing in attempts to formalize its garbage separation and recycling. The aim of the paper is to address the importance of integrating the existing culture and knowledge of the people with the making of future environmental technologies and policies.

Abstract: This paper aims to characterize the evolution of organic matter during the composting of municipal solid waste (MSW). During the 46-day composting process, six samples with different composting time were collected from Songjiang Solid Waste Biological Treatment Plant in Shanghai, China. Dissolved organic matter (DOM) was extracted by ultra-pure water, and the UV-Visible (UV-Vis) spectra of DOM were scanned and investigated. The results showed that, during the composting process, non-humus substances in DOM were gradually transformed into humus substances, the aromatization, molecular weight and humification of humus substances increased. Correlation analysis showed that the absorbance value at 280 nm (SUVA₂₈₀), and the area of 226~400 nm (A_226~400) correlated positively with each other. The dissolved organic carbon (DOC) concentration exhibited a negative correlation with the parameters S_275~295, SUVA₂₈₀ and A_200~226, and the correlation coefficients between the DOC content and the A_220~226 value was the best (r= -0.976, P=0.001). The absorbance ratio bewteen 465 and 665 nm (E₄₆₅/E₆₆₅) showed a significant correlation with SUVA₂₈₀ (r=-0.892, P=0.017), A_226~400 (r=-0.909, P=0.012) and DOC (r=0.840, P=0.036). The absorbance ratio of 250 to 365 nm (E₂₅₀/E₃₆₅) correlated significantly with DOC (r=-0.880, P=0.021), and showed no correlation with the other parameters. Absorption curve slope in the range of 275~295nm (S_275~295) showed a significantly positive correlation with the DOC content (r=0.961, P=0.002). Among all parameters, the A_200~226, A_226~400 and S_275~295 values reflected compost maturity best.