State of energy consumption and CO2 emission in Bangladesh

Carbon dioxide (CO2) is one of the most important gases in the atmosphere, and is necessary for sustaining life on Earth. It is also considered to be a major greenhouse gas contributing to global warming and climate change. In this article, energy consumption in Bangladesh is analyzed and estimates are made of CO2 emission from combustion of fossil fuel (coal, gas, petroleum products) for the period 1977 to 1995. International Panel for Climate Change guidelines for national greenhouse gas inventories were used in estimating CO2 emission. An analysis of energy data shows that the consumption of fossil fuels in Bangladesh is growing by more than 5% per year. The proportion of natural gas in total energy consumption is increasing, while that of petroleum products and coal is decreasing. The estimated total CO2 release from all primary fossil fuels used in Bangladesh amounted to 5072 Gigagram (Gg) in 1977, and 14 423 Gg in 1995. The total amounts of CO2 released from petroleum products, natural gas, and coal in the period 1977-1995 were 83 026 Gg (50% of CO2 emission), 72 541 Gg (44% of CO2 emission), and 9545 Gg (6% CO2 emission), respectively. A trend in CO2 emission with projections to 2070 is generated. In 2070, total estimated CO2 emission will be 293 260 Gg with a current growth rate of 6.34% y . CO2 emission from fossil fuels is increasing. Petroleum products contribute the majority of CO2 emission load, and although the use of natural gas is increasing rapidly, its contribution to CO2 emission is less than that of petroleum products. The use of coal as well as CO2 emission from coal is expected to gradually decrease.     

Phytostabilization of a metal contaminated sandy soil. I: Influence of compost and/or inorganic metal immobilizing soil amendments on phytotoxicity and plant availability of metals

In a lysimeter set-up, compost addition to an industrial contaminated soil slightly reduced phytotoxicity to bean seedlings. The "Phytotoxicity Index" (on a scale from 1 to 4) decreased from 3.5 to 2.8. The same treatment also reduced metal accumulation in grasses: mean Zn, Cd and Pb concentrations decreased respectively from 623 to 135, from 6.2 to 1.3 and from 10.7 to <6 mg kg-1 dry weight. When combined with inorganic metal immobilizing amendments, compost had a beneficial effect on plant responses additional to the inorganic amendments alone. Best results were obtained when using compost (C)+cyclonic ashes (CA)+steel shots (SS). The "Phytotoxicity Index" decreased to 1.7, highest diversity of spontaneously colonizing plants occurred, and metal accumulation in grasses reduced to values for uncontaminated soils. Based on the first year evaluation, C+CA+SS showed to be an efficient treatment for amendment assisted phytostabilization of the contaminated Overpelt soil.     

Influences of macroalga-derived dissolved organic carbon on the aquatic toxicity of copper and cadmium

In this study, the effect of dissolved organic carbon (DOC) derived from macroalga (Sargassum) on the acute toxicity of copper (Cu) and cadmium (Cd) to a freshwater cladoceran (Daphnia magna) was investigated. Potassium-loaded macroalga was incubated with ultrapure water to extract macroalgal DOC, which was then spiked with the constituents of the Elendt M7 hard water media. The 48 h median lethal concentration of Cu increased linearly with DOC levels but that of Cd was relatively independent of DOC levels (0-44 mg l(-1)). The independence of Cd toxicity on DOC level might be due to the competitive effect of high calcium concentrations in the media with Cd for the binding sites of DOC. The decreased Cu toxicity was a result of reduced Cu uptake as evidenced in a separate accumulation test. Also, the capability of the macroalgal DOC on reducing Cu toxicity was found to be comparable to DOC tested in other studies. Therefore, the present study suggested that the biosorption treatment process using macroalgae should consider the effect of DOC release from the biomass as a step of modifying the metal toxicity as well as influencing metal biosorption capacity.     

Genotypic variations in the accumulation of Cd, Cu, Pb and Zn exhibited by six commonly grown vegetables

Metal contaminants in garden and allotment soils could possibly affect human health through a variety of pathways. This study focused on the potential pathway of consumption of vegetables grown on contaminated soil. Five cultivars each of six common vegetables were grown in a control and in a soil spiked with Cd, Cu, Pb and Zn. Highly significant differences in metal content were evident between cultivars of a number of vegetables for several of the contaminants. Carrot and pea cultivars exhibited significant differences in accumulated concentrations of Cd and Cu with carrot cultivars also exhibiting significant differences in Zn. Distinctive differences were also identified when comparing one vegetable to another, legumes (Leguminosae) tending to be low accumulators, root vegetables (Umbelliferae and Liliaceae) tending to be moderate accumulators and leafy vegetables (Compositae and Chenopodiaceae) being high accumulators.     

Evaluation of diffusive gradients in thin film (DGT) samplers for measuring contaminants in the Antarctic marine environment

This work has been the first application of DGT samplers for measuring metals in water and sediment porewater in the Antarctic environment, and whilst DGT water sampling was restricted to quantification of Cd, Fe and Ni, preconcentration using Empore chelating disks provided results for an additional nine elements (Sn, Pb, Al, Cr, Mn, Co, Cu, Zn, As). Although higher concentrations were measured for some metals (Cd, Ni, Pb) using the Empore technique, most likely due to particulate-bound or colloidal species becoming entrapped in the Empore chelating disks, heavy metal concentrations in the impacted Brown Bay were found to be comparable with the non-impacted O'Brien Bay. Sediment porewater sampling using DGT also indicated little difference between Brown Bay and O'Brien Bay for many metals (Cd, Al, Cr, Co, Ni, Cu), however, greater amounts of Pb, Mn, Fe and As were accumulated in DGT probes deployed in Brown Bay compared with O'Brien Bay, and a higher accumulation of Sn was observed in Brown Bay inner than any of the other three sites sampled. Comparison of DGT derived porewater concentrations with actual porewater concentrations showed limited resupply of Cd, Pb, Al, Cr, Mn, Co, Ni, Cu, Zn and As from the solid phase to porewater, with these metals appearing to be strongly bound to the sediment, however, resupply of Fe and Sn was apparent. Based upon our observations here, we suggest that Sn, and to a lesser extent Pb, are critical contaminants.     

Source and persistence of pesticides in a semi-confined chalk aquifer of southeast England

Pesticide contamination in groundwater is an increasing problem that poses a significant long-term threat to water quality. Following the detection of elevated concentrations of diuron in boreholes in a semi-confined chalk aquifer from southeast England, a sampling programme was undertaken. Between 2003 and 2004 diuron was observed in 90% of groundwaters analysed. In 60% of groundwater samples metabolites of diuron were more prevalent than the parent compound. Longer-term (1989-2005) monitoring shows that pollution of the aquifer by atrazine, simazine, and more recently diuron, shows a positive correlation with periods of high groundwater levels. Results from groundwater residence time indicators suggest that the highest diuron concentrations are associated with waters containing the greatest proportion of recent recharge. There is some evidence to indicate that diuron occurrence can be spatially related to areas of urban and industrial development and is probably correlated with amenity usage.     

Assessment of soil lead exposure in children in Shenyang, China

Soil lead pollution is serious in Shenyang, China. The paper brings together the soil work, the bioaccessibility, and the blood lead data to assess the soil lead exposure in children in Shenyang, China. Approximately 15.25% of the samples were above China Environment Protection Agency guideline concentration for soil Pb to protect human from health risk (350 mgkg(-1)). Pb concentrations varied among use scenarios. The main lead contamination sources are industry emission and automobile exhaust. Bioaccessibility also varied among use scenarios. Children, who ingested soil from industrial area, public parks, kindergarten playground, and commercial area, are more susceptible to soil lead toxicity. The industrial area soil samples presented higher bioaccessibility compared to the other use scenario soil samples contaminated by automobile exhaust. The result also suggested a most significant linear relationship between the level of Pb contamination and the amount of Pb mobilized from soil into ingestion juice. Soil pH seemed to have insignificant influence on bioaccessibility in the present study. Bioaccessibility was mainly controlled by other factors that are not investigated in this study. A linear relationship between children blood lead and soil intestinal bioaccessibility was present in the study. Children who are 4-5 years old are more likely to demonstrate the significant relationship between soil lead bioaccessibility and blood lead as their behaviors place them at greatest risk of soil lead toxicity, and their blood lead levels are more likely to represent recent exposure.     

Prediction of particulate loading in exhaust from fabric filter baghouses with one or more failed bags

Loss of filtration efficiency in a fabric filter baghouse is typically caused by bag failure, in one form or another. The degree of such failure can be as minor as a pinhole leak or as major as a fully involved baghouse fire. In some cases, local air pollution regulations or federal hazardous waste laws may require estimation of the total quantity of particulate matter released to the environment as a result of such failures. In this paper, a technique is presented for computing the dust loading in the baghouse exhaust when one or more bags have failed. The algorithm developed is shown to be an improvement over a previously published result, which requires empirical knowledge of the variation in baghouse pressure differential with bag failures. An example calculation is presented for a baghouse equipped with 200 bags. The prediction shows that a small percentage of failed bags can cause a relatively large proportion of the gas flow to bypass the active bags, which, in turn, leads to high outlet dust loading and low overall collection efficiency from the baghouse.     

Probabilistic study of well capture zones distribution at the Lauswiesen field site

The delineation of well capture zones is of utmost environmental and engineering relevance as pumping wells are commonly used both for drinking water supply needs, where protection zones have to be defined, and for investigation and remediation of contaminated aquifers. We analyze the probabilistic nature of well capture zones within the well field located at the "Lauswiesen" experimental site. The test site is part of an alluvial heterogeneous aquifer located in the Neckar river valley, close to the city of Tübingen in South-West Germany. We explore the effect of different conceptual models of the structure of aquifer heterogeneities on the delineation of three-dimensional probabilistic well catchment and time-related capture zones, in the presence of migration of conservative solutes. The aquifer is modeled as a three-dimensional, doubly stochastic composite medium, where distributions of geo-materials and hydraulic properties are uncertain. We study the relative importance of uncertain facies geometry and uncertain hydraulic conductivity and porosity on predictions of catchment and solute time of travel to the pumping well by focusing on cases in which (1) the facies distribution is random, but the hydraulic properties of each material are fixed, and (2) both facies geometry and material properties vary stochastically. The problem is tackled within a conditional numerical Monte Carlo framework. Results are provided in terms of probabilistic demarcations of the three-dimensional well catchment and time-related capture zones. Our findings suggest that the uncertainty associated with the prediction of the location of the outer boundary of well catchment at the "Lauswiesen" site is significantly affected by the conceptual model adopted to incorporate the heterogeneous nature of the aquifer domain in a predictive framework. Taking into account randomness of both lithofacies distribution and materials hydraulic conductivity allows recognizing the existence of preferential flow paths that influence the extent of the well catchment and the solute travel time distribution at the site.     

Quality assured measurements of animal building emissions: gas concentrations

Comprehensive field studies were initiated in 2002 to measure emissions of ammonia (NH3), hydrogen sulfide (H2S), carbon dioxide (CO2), methane (CH4), nonmethane hydrocarbons (NMHC), particulate matter <10 microm in diameter, and total suspended particulate from swine and poultry production buildings in the United States. This paper focuses on the quasicontinuous gas concentration measurement at multiple locations among paired barns in seven states. Documented principles, used in air pollution monitoring at industrial sources, were applied in developing quality assurance (QA) project plans for these studies. Air was sampled from multiple locations with each gas analyzed with one high quality commercial gas analyzer that was located in an environmentally controlled on-farm instrument shelter. A nominal 4 L/min gas sampling system was designed and constructed with Teflon wetted surfaces, bypass pumping, and sample line flow and pressure sensors. Three-way solenoids were used to automatically switch between multiple gas sampling lines with > or =10 min sampling intervals. Inside and outside gas sampling probes were between 10 and 115 m away from the analyzers. Analyzers used chemiluminescence, fluorescence, photoacoustic infrared, and photoionization detectors for NH3, H2S, CO2, CH4, and NMHC, respectively. Data were collected using personal computer-based data acquisition hardware and software. This paper discusses the methodology of gas concentration measurements and the unique challenges that livestock barns pose for achieving desired accuracy and precision, data representativeness, comparability and completeness, and instrument calibration and maintenance.