Adsorption characteristics of Ni(II) on gamma-type alumina particles and its determination of overall adsorption rate by a differential bed reactor

The adsorption experiment of nickel ion [Ni(II)] on gamma-type alumina by a differential bed reactor in aqueous solutions was investigated to determine the adsorption characteristics and overall adsorption rate. The adsorbed amount increased rapidly with pH from pH 2 to 6 and kept constant over pH 6. The adsorbed amount of Ni(II) increased with temperature from 20 to 50 degrees C. Correlation coefficients (R2) of Langmuir and Freundlich adsorption isotherms were 0.9268 and 0.9489, respectively, and Freundlich isotherm was more suitable for adsorption on gamma-type alumina than Langmuir isotherm.The overall adsorption rate of Ni(II) on gamma-type alumina at pH 6 by a differential bed rector was determined as follows: r = 68.77Ce(1.61) - 17.60qe(0.36). Al(III) ions in solutions were away from the alumina surface during the adsorption of Ni(II) and Al(III) concentration increased with an increasing Ni(II) adsorbed amount on alumina.     

Levels of organochlorine pesticides in human milk from central Taiwan

The present study determined the residues of organochlorine pesticides (OCPs) in human milk collected in central Taiwan between December 2000 and November 2001. The OCPs were analyzed by GC/MS for 36 human milk samples from healthy women ranging between 20 and 36 years of age. The predominant OCPs were p,p′-DDE, p,p′-DDT, -CHL, heptachlor epoxide, heptachlor, β-HCH, and γ-HCH, with median levels of 228, 19, 7.4, 4.0, 2.3, 1.2, and 0.8 ng/g lipid, respectively. The residues of OCPs in human milk from central Taiwan were comparable to those described in results from Sweden, the United Kingdom, and Japan, and were significantly lower than those from investigations in Asian countries, including China, Thailand, Indonesia, and Vietnam. Low DDE/DDT ratio (mean = 13.6, SD = 6.54) indicated that residual OCPs in human milk mainly originate from past exposure. A notable decrease in DDT levels (∑ DDT = 333 ng/g lipid) in human milk was found in this study compared to results from the previous two decades (∑ DDT = 3595 ng/g lipid). Hypothetically, the level of -CHL was significantly associated with total TEQ levels in Taiwanese human milk because of the sources of food contaminant, i.e. animal fat. Based on low OCP levels in Taiwanese human milk and low estimated median daily intake of total DDTs for a breastfed infant (1358 ng/kg/day) with the assumption of an infant weighting 4 kg and consuming 699 g milk per day in the first month after birth, the Taiwanese policy of breast-feeding promotion was supported.     

Climatology,Trend Analysis and Prediction of Sandstorms and their Associated Dustfall in China

Based on statistical data about Sand and Dust Storms (SDS) and their associated dustfall, features of temporal and spatialdistribution were studied first in this article. SDS and associateddustfalls occurred most often in northern China, especiallynorthwestern China. However, in the last two years, they have atendency to occur on the central and western parts of the Inner Mongolia Autonomous Region. As a result, Beijing is now among the impact areas, and the Chinese government is paying greaterattention to the matter. The changing trends of SDS and associated dustfalls were subsequently analyzed. Occurrences were seen to be decreasing with the feature of fluctuation duringthe period of 1954–2001, but they have slightly increased since 2000. Also, climate factors related to SDS and associated dustfalls were discussed. Finally, it was recommended that methods to predict SDS in China be further studied in the future.     

Local waste management constraints and waste administrators in China

Local level waste authorities and their officials directly interact and serve the people on behalf of higher governments. Given the influential positions they have on the quality of life of the citizens, these local waste authorities deserve more attention from researchers. This study throws light on the factors related to local waste management and administrators that have caused waste management failures in three mainland Chinese cities. Based on a survey conducted in 2002-2003, it was found that waste administrators in these cities are not professionally competent in their jobs and they are also not confident in using economic instruments to address waste management issues in their cities. These local waste authorities are generally under-funded, and funding politics has to some extent eroded the incentives to carry out the instructions of higher waste authorities. The community at large also does not respect local waste management work. The residents frequently litter, are unobservant of waste collection times and are unwilling to pay for waste collection service. All of these are handicapping environmentally sound waste management.     

Spatial Analysis of Volatile Organic Compounds from a Community-Based Air Toxics Monitoring Network in Deer Park,Texas, USA

In the summer of 2003, ambient air concentrations of volatile organic compounds (VOCs) were measured at 12 sites within a 3-km radius in Deer Park, Texas near Houston. The purpose of the study was to assess local spatial influence of traffic and other urban sources and was part of a larger investigation of VOC spatial and temporal heterogeneity influences in selected areas of Houston. Seventy 2-h samples were collected using passive organic vapor monitors. Most measurements of 13 VOC species were greater than the method detection limits. Samplers were located at 10 residential sites, a regulatory air monitoring station, and a site located at the centroid of the census tract in which the regulatory station was located. For residential sites, sampler placement locations (e. g., covered porch vs. house eaves) had no effect on concentration with the exception of methyl tertiary-butyl ether (MTBE). Relatively high correlations (Pearson r > 0.8) were found between toluene, ethylbenzene, and o,m,p-xylenes suggesting petroleum-related influence. Chloroform was not correlated with these species or benzene (Pearson r < 0.35) suggesting a different source influence, possibly from process-related activities. As shown in other spatial studies, wind direction relative to source location had an effect on VOC concentrations.     

A Numerical and Experimental Study of Pollutant Dispersion in a Traffic Tunnel

Three-dimensional turbulent flow and dispersion of gaseous pollutants carbon monoxide (CO) and nitrogen oxides (NOx) in a road tunnel was modeled using the standard k–ε turbulence model and solved numerically using the finite volume method. Vehicle emissions were estimated from the measured traffic flow rates and modeled as banded line sources along the tunnel floor. The effects of fan ventilation and piston effect of moving vehicles on the airflow and pollutant dilution were examined. The numerical results reveal that a peak velocity exists near the tunnel floor due to the piston effect of vehicles. The cross-sectional concentrations of air pollutants are non-uniformly distributed and concentrations rise with downstream distance. The piston effect of vehicles can alone provide 25%–34% dilution of air pollutants in the tunnel, compounded 43%–70% dilution effect according to the ventilation condition.     

Impacts of methanol fuel on vehicular emissions: A review

● Methanol effectively reduces CO, HC, CO₂, PM, and PN emissions of gasoline vehicles. ● Elemental composition of methanol directly affects the reduction of emissions. ● Several physicochemical properties of methanol help reduce vehicle emissions. The transport sector is a significant energy consumer and a major contributor to urban air pollution. At present, the substitution of cleaner fuel is one feasible way to deal with the growing energy demand and environmental pollution. Methanol has been recognized as a good alternative to gasoline due to its good combustion performance. In the past decades, many studies have investigated exhaust emissions using methanol-gasoline blends. However, the conclusions derived from different studies vary significantly, and the explanations for the effects of methanol blending on exhaust emissions are also inconsistent. This review summarizes the characteristics of CO, HC, NO_x, CO₂, and particulate emissions from methanol-gasoline blended fuels and pure methanol fuel. CO, HC, CO₂, particle mass (PM), and particle number (PN) emissions decrease when methanol-blended fuel is used in place of gasoline fuel. NO_x emission either decreases or increases depending on the test conditions, i.e., methanol content. Furthermore, this review synthesizes the mechanisms by which methanol-blended fuel influences pollutant emissions. This review provides insight into the pollutant emissions from methanol-blended fuel, which will aid policymakers in making energy strategy decisions that take urban air pollution, climate change, and energy security into account.     

Environmental monitoring of the role of phosphate compounds in enhancing immobilization and reducing bioavailability of lead in contaminated soils

Lead is a highly toxic element and forms stable compounds with phosphate, which is commonly used to immobilize Pb in soils. However, few studies have monitored the long-term stability of immobilized Pb, which is a critical factor in determining the effectiveness of the in situ stabilization technique. Both soluble and insoluble phosphate compounds were tested for Pb immobilization, and its subsequent mobility and bioavailability in a contaminated soil from a shooting range. Adding tricalcium phosphate, hydroxyapatite, rock phosphate and potassium dihydrogen phosphate reduced the concentration of ammonium-nitrate-extractable Pb in the contaminated soil by 78.6%, 48.3%, 40.5% and 80.1%, respectively. Insoluble phosphate amendments significantly reduced leached Pb concentration from the column while soluble potassium dihydrogen phosphate compound increased P and Pb concentrations in the leachate. Rock phosphate reduced Pb accumulation in earthworms by 21.9% compared to earthworms in the control treatment. The long-term stability of immobilized Pb was evaluated after 2 years' incubation of the contaminated soil with rock phosphate or soluble phosphate compounds. Bioavailable Pb concentration as measured by simple bioavailability extraction test (SBET) showed the long-term stability of immobilized Pb by P amendments. Therefore, Pb immobilization using phosphate compounds is an effective remediation technique for Pb-contaminated soils.     

Degradation of azo dye reactive violet 5 by TiO2 photocatalysis

The photocatalytic degradation of hydrolyzed reactive violet 5 (RV5) using titanium dioxide (TiO₂) was investigated in this study. The effects of various factors including the amount of photocatalyst, RV5 concentration, light intensity, and pH on photocatalytic degradation were evaluated. The photodegradation efficiency was 90% after 20 min of irradiation and reached nearly 100% after 80 min under the condition of pH 4 and temperature of 25°C. The decolorization rate typically followed first-order reaction, and increased markedly with increasing amount of photocatalyst, pH as well as light intensity. The total mineralization, based on total organic carbon (TOC) concentration was 53% after 20 min of UV light exposure and approached nearly 100% after 140 min. The final mineralization product was formylformamide. The photodegradation was faster than the mineralization, indicating that the intermediate products of decolorization were resistant to photodegradation. In this study, we found that toxicity of RV5 significantly decreased after decolorization. Our study suggests that the photocatalytic degradation treatment of RV5 with TiO₂ in wastewater is a simple and fast method.     

Linear alkylbenzenesulfonates (LAS) of an urban stream in Korea

Profiles of alkyl homologues and isomers of LAS were monitored for an urban stream polluted with municipal wastewaters in Korea. Alkylchains of the stream LAS were shorter than commercial standards and higher I/E ratios were associated with lower LAS concentrations. These suggested a partial biodegradation of LAS in the stream. Higher LAS concentrations were observed in the upper stream. LAS levels were at their lowest during summer probably due to high precipitation and faster biodegradation rates. LAS contributed to about 29% of MBAS and could be used to roughly estimate BOD concentration of the stream.