Seasonal characteristics of haze observed by continuous visibility monitoring in the urban atmosphere of Kwangju, Korea

Continuous visibility monitoring has been carried out inKwangju, Korea since May 1999. The total light extinctioncoefficient b _ext measured by a transmissometer andreveals seasonal trends in urban visual air quality,especially under hazy conditions with a visual range of lessthan 15 km. Seasonal atmospheric visibility under lowrelative humidity during the winter was observed to be betterthan during any other seasons. Summertime visibility wasseverely degraded due to highly increased light scattering byhygroscopic particles under high humidity atmosphericconditions. Visibility during spring and fall was alsomoderate. However, yellow sand in spring caused the lowestvisibility conditions over the measurement area for a fewdays. With continuous monitoring using the transmissometer,the daily average seasonal visual range was measured to be13.1, 9.2, 11.0, and 13.9 km in spring, summer, falland winter, respectively. Under the atmospheric humiditycondition less than 60%, visual range was observed tobe 16.1, 13.9, 15.1, and 16.6 km in spring, summer,fall, and winter, respectively. The mean light extinctionbudget by sulfate and nitrate aerosols was determined to bethe highest value of 63.71% during the summer and thelowest value of 27.08% during spring. During the `yellow sand dust' period, a mean light extinction budget by soil particles was estimated to be at an unusually high value of 44.22%.     

A Watershed-based Cumulative Risk Impact Analysis: Environmental Vulnerability and Impact Criteria

Swine Concentrated Animal Feeding Operations (CAFOs) have received much attention in recent years. As a result, a watershed-based screening tool, the Cumulative Risk Index Analysis (CRIA), was developed to assess the cumulative impacts of multiple CAFO facilities in a watershedsubunit. The CRIA formula calculates an index number based on: 1) the area of one or more facilities compared to the area of the watershed subunit, 2) the average of the environmental vulnerability criteria, and 3) the average of the industry-specific impact criteria. Each vulnerability or impact criterion is ranked on a 1 to 5 scale, with a low rank indicating low environmental vulnerability or impact and a high rank indicating high environmental vulnerability or impact. The individual criterion ranks, as well as the total CRIA score, can be used to focus the environmental analysis and facilitate discussions with industry, public, and other stakeholders in the Agency decision-making process.     

Air pollution exposure monitoring and estimation. Part VI. Ambient exposure of adults in an industrialised region

This paper presents methodology and results of a dynamic individual air pollution exposure model (DINEX) that calculates the hourly exposure for each adult in a panel study. Each of over 260 participants, through the use of a diary, provided information used in the model to calculate his/her personal, individualised exposure. The participants filled out the diary daily, hour by hour, over two, two month periods. The exposure assessment model coupled the diary information and results of an indoor/outdoor measurement program, with the results of dispersion modelling on an hourly basis for an industrial area in Norway. The estimated air pollution concentrations from the dispersion model, based on continuous meteorological measurements, were calibrated with air pollutant concentrations measured continuously.     

Collaborative study to improve the quality control of rare earth element determinations in environmental matrices

In order to control the quality of rare earth determinations in environmental matrices, the Standards, Measurements and Testing Programme (formerly Community Bureau of Reference, BCR) of the European Commission has started a project, the final aim of which is to certify four types of matrices (tuna muscle, mussel tissue, aquatic plant and estuarine sediment) for their contents of a range of rare earth elements (Sc, Y and the lanthanides: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). The elements U and Th were added to the study. The first part of this project consisted of an interlaboratory study which aimed to test the feasibility of preparation of environmental reference materials and to detect and remove most of the pitfalls observed in rare earth determinations. This paper presents the preparation of the four matrices for the intercomparison study and for the candidate reference material. The main results are presented of the interlaboratory study that was carried out prior to the certification campaign. This collaborative trial is the first attempt ever carried out at this scale to evaluate the state-of-the-art of rare earth determinations in the environment. Its impact on the improvement of chemical measurements will have positive effects on the comparability of data necessary for environmental monitoring.     

Soil Lead and Other Metal Levels in Industrial, Residential and Nature Reserve Areas in Singapore

The use of pressure feedback microwave digestion technique has permitted rapid and efficient digestion of soil and sediment samples. The evaluation of different acid mixtures to digest soil samples were studied by mixed-level orthogonal array design. The selected acid mixture of HCl-HNO3-HF was employed in the survey of Pb, Zn, Cu, Cr and Mn in soil samples. Surface soil samples were collected from industrial, residential and nature reserve areas in Singapore. The five metal concentrations were determined by flame atomic absorption spectrometry and graphite furnace atomic absorption spectrometry. The lead and other metal contents in NBS SRM 1645, NIES CRM No. 2 and NRCC BCSS-1 sediment standard references were determined concurrently with the survey samples. Five measured metal loading on the surface soils was in the order: industrial area > residential area > nature reserve area. The trace metal concentrations in surface soil from areas of heavy traffic are higher than those from residential areas. The main sources of trace metal pollution are vehicular exhaust and industrial activities.     

A Global Overview of Atmospheric Acid Deposition Fluxes

This paper presents a summary of globalacid deposition flux data taken from a globalassessment report on acid deposition prepared forUNEP/WMO (Whelpdale and Kaiser, 1996). There is a largevariation in the spacial coverage and reliability ofmonitoring around the world. Many more stationsmeasure wet deposition than collect appropriate datafor estimating dry deposition. The widespread regionswith highest precipitation concentrations anddeposition fluxes of sulphate and nitrate coincideclosely with the regions of highest density ofSO₂ and NO_x precursor emissions occurringprimarily in the mid-latitude, northern hemispherebelt where a large fraction of the worlds fossilfuels is consumed. Organic acids in precipitation makea minor contribution to acidity (<20%) inindustrial regions, but in the rest of the world theyare of same order, or even exceed, inorganic acids.Less is known about dry deposition, but it appears topredominate near strong emission sources with wetdeposition predominating farther downwind. The molarratio of the N/S contribution to acidic deposition isclose to 1.0 over large areas of Europe and NorthAmerica, but is highly variable elsewhere, beinghighest in equatorial regions due to biomass burningand lowest near smelters and other large sources of SO₂.     

Degradation of Pesticides on Plant Surfaces and its Prediction - A Case Study on Tea Plant

The degradative kinetics of pesticides on plant surface are characterized by an initial rapid degradation which follows a first-order kinetics, then transferred to a more slower degradative rate. The degradative process mainly consists of photodegradation, evaporation, rainfall elution and growth dilution. The influencing parameters of these processes were investigated by using the tea plant as a case study. The predictive model of the initial concentration, photodegradation rate constant, evaporation rate constant, rainfall elution rate, growth dilution rate and the total degradation rate was discussed and verified in four locations situated in the range of 25°-30°N latitude, and acceptable results were obtained.     

Modeling photocatalytic destruction of the organic contaminants in continuous stir flow reactor

Thin-film technique is becoming an industry standard for the preparation of TiO₂-based photocatalyst for organic destruction. The catalyst provides several advantages over the conventional powder TiO₂ in the treatment of wastewater and groundwater. In this study, a continuous stir flow reactor model is developed capable of describing the photocatalytic process. The model incorporates the following fundamental mechanisms: adsorption, diffusion, liquid-film transfer, UV attenuation, and photocatalytic reaction. All of the simulation results indicate that there exists a highly nonlinear relation between each of these parameters and the destruction rate. Various incident light intensities also are incorporated to simulate the energy efficiency. The simulations illustrate that the photocatalytic model can be used to elucidate the effect of process variables. It is also possible to “custom-design” a catalyst for the treatment of a particular waste stream.     

Trends in motor-vehicle related air pollutants in central London

Results of intermittent monitoring of six aromatic hydrocarbons (benzene, toluene, ethyl-benzene, m-xylene, p-xylene and o-xylene), carbon monoxide and oxides of nitrogen over a thirteen year period at a site in central London (Exhibition Road) are presented. Four monitoring regimes were undertaken; namely, 1979, 1982/83, 1986/87 and 1991/92. The summertime daytime mean ambient concentrations of the measured parameters at this site are presented. The reported concentrations show a reduction from 1979 to 1992 by approximately a factor of two, despite national increases in motor fuel consumption and the volume of traffic. Relevant European Community legislation covering emissions from motor-vehicles are outlined and comparisons are made with emissions from motor vehicles predicted from the UK national inventory. The importance of the frequency of measurements was also noted.     

Chlorobiphenyl contaminants at Pladda and Garroch Head in the Firth of Clyde in relation to sewage sludge input

Sewage sludge dumped at Garroch Head in the Firth of Clyde contains significant quantities of chlorinated hydrocarbons, such as polychlorinated biphenyls (CBs). These compounds are lipophilic and resistant to degradation. They accumulate in the biota either from the water column or through the food chain, particularly in tissue with a high lipid content. Bottom dwelling fish, such as plaice, in the vicinity of the dump site will accumulate CBs from their environment. Eighteen of the 209 CBs were measured in plaice livers from the Garroch Head dump site and from Pladda, a site reasonably remote from the dump site but also in the Clyde, over a 7 year period prior to the cessation of dumping in December 1998. Concentrations of the congeners in the liver of fish caught at the dump site were, in general, higher than those in the liver of fish caught at Pladda. Concentrations in the plaice livers for the sum of 18 CBs ranged from 1611 to 8471 micrograms kg-1 lipid for Garroch Head samples and from 336.9 to 2635 micrograms kg-1 lipid for samples from Pladda. The data were evaluated using principal component analysis (PCA). Pattern analysis was undertaken by normalising to the recalcitrant CB 153. Livers from the dump site were found to have a higher proportion of the lower chlorinated CBs. CB patterns were similar at the Garroch Head dump site from year to year, but multivariate techniques showed that there were differences in pattern when normalised to CB 153.