Huan Feng

Adsorption Behavior of EDTA-Graphene Oxide for Pb (II) Removal

Chelating groups are successfully linked to graphene oxide (GO) surfaces through a silanization reaction between N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (EDTA-silane) and hydroxyl groups on GO surface. EDTA-GO was found to be an ideal adsorbent for Pb(II) removal with a higher adsorption capacity. EDTA-modification enhances the adsorption capacity of GO because of the chelating ability of ethylene diamine triacetic acid. This study investigates the adsorption and desorption behaviors of heavy metal cations and the effects of solution conditions such as pH on Pb(II) removal. The adsorption capacity for Pb(II) removal was found to be 479 ± 46) mg/g at pH 6.8, and the adsorption process was completed within 20 min. The Langmuir adsorption model agrees well with the experimental data. The experimental results suggest that EDTA-GO can be reused after washed with HCl, suggesting potential applications in the environmental cleanup.

Heavy metal contamination in surface sediments of Yangtze River intertidal zone: an assessment from different indexes.

Surface sediments (0-5 cm) from 59 stations within the Yangtze River intertidal zone (YRIZ) were sampled for metal contamination analysis in April and August 2005. The concentrations ranged (in mg kg(-1) dry weight): Al, 40,803-97,213; Fe, 20,538-49,627; Cd, 0.12-0.75; Cr, 36.9-173; Cu, 6.87-49.7; Mn, 413-1,112; Ni, 17.6-48.0; Pb, 18.3-44.1; and Zn, 47.6-154; respectively. Among the 59 sampling stations, enrichment factors (EF) indicate enrichment of Cd (52 stations), Cr (54 stations), Cu (5 stations), Ni (26 stations), Pb (5 stations) and Zn (5 stations). Geoaccumulation indexes (I(geo)) also suggest individual metal contamination in localized areas. This study indicates that Cd, Cr and Ni enrichment in the YRIZ sediment is widespread whereas Cu, Mn, Pb and Zn enrichment is localized or nonexistent. Factor and cluster analyses indicate that Cd is associated with total organic carbon whereas Cu, Cr, Ni, Pb and Zn have a close association with Mn.

DISTRIBUTION OF HEAVY METAL AND PCB CONTAMINANTS IN THE SEDIMENTS OF AN URBAN ESTUARY : THE HUDSON RIVER

Abstract Surficial sediments obtained from sediment cores were collected over 100km along the axis of the lower Hudson River in June 1994, November 1994, May 1995 and April 1996 and showed the presence of anthropogenic Ag, Cd, Cu, Pb, Zn, PCBs in all samples. Contaminant distributions in the Hudson River estuary show two types of trends: Ag, Cu and Pb show an increasing trend down-estuary with maximum values in New York Harbor sediments; in contrast, Cd, Zn and total PCBs display a decreasing trend toward New York Harbor where urban sources are also apparent. Silver is a useful tracer of urban sources of contaminants in the Hudson River estuary and polychlorinated biphenyls (PCBs) are useful source indicators of upriver sources. Correlations of Cu and Pb with Ag suggest that Ag, Cu and Pb are dominated by down-estuary sources such as wastewater effluent. The history of their inputs suggests that they have been progressively transported downstream. Correlations of Cd and Zn with total PCBs indicate that these contaminants are dominated by upriver sources, where they are removed and diluted downstream along with the sediment transport.

Metal contamination in sediments of the western Bohai Bay and adjacent estuaries, China.

Twelve sediment cores were collected in July 2007 in open waters of western Bohai Bay, the Port of Tianjin, and the adjacent estuaries of the Haihe and Yongding Rivers. While overall concentrations of trace metals at incremental depths in these cores met the Marine Sediment Quality (GB18668-2002) criteria of China, the magnitude of both metal enrichment factors (EF) and geoaccumulation indices (I(geo)) suggested that pollution with Ag, Cd, Cr, Cu and Zn was occurring in the estuaries and Port. Risk analysis also suggested that Ag and Ni concentrations were sufficiently elevated as to cause adverse biological effects in the study area. Although metal concentrations in western Bohai Bay were of less concern, a positive relationship between EF values and excess (210)Pb activity for several metals suggested that their concentrations were increasing over time.

A purview of waste management evolution: special emphasis on USA.

The generation of waste in urban regions over time is seen to impact the balance of anthropogenic and natural resources. Various national and international initiatives to manage urban solid waste are in place and has thus have evolved at present to form an assortment of different subcomponents involving environmental, administrative, regulatory, scientific, market, technology, and socio-economic factors, which has increasing bearing on the US due to its volume and nature of discards. This paper draws together the various aspects of municipal solid waste (MSW) management as it evolved, particularly in the American society through reviewing works and findings. In many parts of the country, waste management at present, primarily involves landfilling, incineration with and without energy recovery, recycling and composting. Legislation, nature of wastes and market trends continue to redefine management operations and its responsibilities and impacts. Complexities are added to it by the nature of urban development as well. New studies and concepts like 3Rs, cradle-to-cradle, industrial ecology, and integrated waste management are adding new dimensions for solving waste problems towards achieving sustainable resource use. Local initiatives, both public and private are in the forefront of adopting alternate waste management procedures. The assistance from various government and private bodies, supporting shifts in waste management approaches, have immense value, as according to the new paradigms, nothing goes to waste.

A system dynamic modeling approach for evaluating municipal solid waste generation, landfill capacity and related cost management issues.

As planning for sustainable municipal solid waste management has to address several inter-connected issues such as landfill capacity, environmental impacts and financial expenditure, it becomes increasingly necessary to understand the dynamic nature of their interactions. A system dynamics approach designed here attempts to address some of these issues by fitting a model framework for Newark urban region in the US, and running a forecast simulation. The dynamic system developed in this study incorporates the complexity of the waste generation and management process to some extent which is achieved through a combination of simpler sub-processes that are linked together to form a whole. The impact of decision options on the generation of waste in the city, on the remaining landfill capacity of the state, and on the economic cost or benefit actualized by different waste processing options are explored through this approach, providing valuable insights into the urban waste-management process.

Assessment of heavy metal pollution in soil and their implications within and around mechanic villages

Analysis of nine composite soil samples, each made of three replicate core samples and their respective background samples collected from Okigwe, Nekede and Orji automobile mechanic villages were conducted. Metal concentrations (mg/kg) above the background levels in the top 100 cm soil profile ranges as follows: 748-70,606 (± 10114.3) for iron; 99-1090 +- 251.3 for lead; 186-600 ± 180 for manganese; 102–1001± 201.9 for copper; 8–23 ± 12.9 for cadmium; 4–27 ± 6.0 for chromium; and 3–10 ± 2.2 for nickel. The order of abundance is: iron > lead > manganese > copper> cadmium > chromium > nickel, with Okigwe > Nekede > Orji. Pollution indexes show that the metals have similar pollution trends in the three layers (L1–L3), with L1 (0–10 cm) > L2 (10–20 cm) > L3 (90–100 cm) in Okigwe, L3 >L1>L2 in Nekede, and L3 >L2 >L1 in Orji. In effect, the shaly Okigwe soil is more polluted in the top layer while the sandy Nekede and Orji are more polluted in the lower layers. Despite this order, metal bioavailability may be less in the Okigwe soil due to its high clay-silt content (47 %–64 %). Pollution factor for Okigwe is 0.8, Nekede is 0.7 and Orji is 0.5. Nekede is under severe to excessive pollution while Orji and Okigwe are under moderate to excessive pollution, with weathered depths 7.4m at Orji and Nekede and 4m at Okigwe as most implicated in the pollution process. Above provides the bases for introducing the innovative concepts of environmentally friendly mechanic village.

Distinguishing sediments from the Yangtze and Yellow Rivers, China: a mineral magnetic approach

The Yellow River and the Yangtze River contribute ~10% of the global fluvial sediment flux to the oceans. Proper characterization of the sediments of the two rivers is critical to the knowledge of their fate in the marginal seas of the west Pacific Ocean. Magnetic measurements have been made on bulk sediments as well as on separated particle size fractions of representative samples from the Yellow and Yangtze River estuaries, with the purpose of providing an efficient means of differentiating both groups of river sediments from each other. We found that on average the Yangtze River estuary sediments have relatively higher ferrimagnetic mineral contents and ferrimagnetic to antiferromagentic ratios compared with the Yellow River estuary sediments. A diagram of Saturated Isothermal Remanent Magnetization (SIRM) versus the demagnetization parameter S−100 can clearly distinguish sediments from the two rivers. Detailed magnetic measurements carried out on particle size fractions provide additional confirmation of magnetic contrasts between the two sets of river sediment samples. These contrasts reflect differences in lithology and weathering regimes in the catchments. To minimize possible biogenic and postdepositional diagenetic overprint in the marine environment, it is recommended that magnetic comparison on the coarser materials (eg, >4 µm) be carried out in addition to bulk measurements. This study shows that the magnetic approach can therefore provide a potentially efficient means of discriminating sediment sources in the Yellow Sea and East China Sea. In view of the rapid variations in sediment load carried by these two rivers in recent years, the present data set also provides a baseline against which possible future variations in sediment composition resulting from catchment changes can be assessed.

Direct observations of three dimensional growth of hydrates hosted in porous media

The visualization of time-resolved three-dimensional growth of tetrahydrofuran hydrates with glass spheres of uniform size as porous media using synchrotron x-ray computed microtomography is presented. The images of hydrate patches, formed from excess tetrahydrofuran in aqueous solution, show random nucleation and growth concomitant with grain movement but independent of container-wall effect. Away from grain surfaces, hydrate surface curvature was convex showing that liquid, not hydrate, was the wetting phase, similar to ice growth in porous media. The extension of the observed behavior to methane hydrates could have implications in understanding their role in seafloor stability and climate change.

Dynamics of sediment and contaminant transport in the Hudson River estuary: Evidence from sediment distributions of naturally occurring radionuclides

Near surface (<10 cm) sediment distributions of234Th sampled multiple times at five locations along the axis of the Hudson Estuary from the Upper Bay of New York to Haverstraw Bay are compared with210Pb data from longer cores at the same locations. The comparison indicates that while there is little net sediment accumulation anywhere except at one location in the Upper Bay, near surface sediment in this reach of the estuary is mobile on short (months) time scales. The sediment appears to be physically mixed rather than bioturbated. Comparison of the sediment inventories of234Th with calculated water column production indicates short time scale (months) variability in234Th deposition. Some parts of the bottom have234Th inventories in excess of local production but these appear to be balanced by234Th deficient areas, resulting in a general equilibrium. Sediment inventories of Pb, Cu, and Zn normalized to210Pb show no evidence of a uniquely urban source of these metals to the lower estuary. Silver distributions in sediment indicate a possible source of silver from New York City, probably related to sewage inputs.