Demonstration of long-term increases in tropospheric O3 levels: causes and potential impacts.

Ground-level ozone (O3) is a well-known atmospheric pollutant with its adverse impacts on the environment and human health. Here, the tropospheric O3 concentrations monitored in seven major cities in Korea at monthly intervals over a 22-year period (1989-2010) are presented, and their long-term variability examined. The analysis of annual mean values of O3 (in nmolmol(-1), or ppb) showed a noticeable increase of 118±69% in all seven cities over the two decades (p<0.01). Changes in O3 levels are closely associated with both environmental (e.g., NOx (NO+NO2), SO2, CO, and total suspended particles (TSPs) (p<0.01), temperature, and sunshine hours) and common anthropogenic variables (e.g., population density and number of vehicles). Evidence collected in this study suggests that the atmospheric conditions in most major cities of Korea should be volatile organic compounds (VOCs) sensitive or NOx saturated with respect to O3 formation. As such, establishment of a proper management strategy seems a sensible approach to control tropospheric ozone concentrations in densely populated cities.

Comprehensive monitoring of drinking well water quality in Seoul metropolitan city, Korea.

In this research, the quality of drinking well waters from 14 districts around Seoul metropolitan city, Korea was assessed by measuring a number of parameters with established guideline (e.g., arsenic, fluoride, nitrate nitrogen, benzene, 1,2-dichloroethene, dichloromethane, copper, and lead) and without such criteria (e.g., hardness, chloride ion, sulfate ion, ammonia nitrogen, aluminum, iron, manganese, and zinc). Physical parameters such as evaporation residue (or total dissolved solids) and turbidity were also measured. The importance of each parameter in well waters was examined in terms of the magnitude and exceedance frequency of guideline values established by international (and national) health agencies. The results of this study indicate that among the eight parameters with well-established guidelines (e.g., WHO), arsenic and lead (guideline value of 0.01 mg L(-1) for both) recorded the highest exceedance frequency of 18 and 16 well samples ranging in 0.06-136 and 2-9 mg L(-1), respectively. As such, a number of water quality parameters measured from many well waters in this urban area were in critical levels which require immediate attention for treatment and continuous monitoring.

The combined application of impinger system and permeation tube for the generation of volatile organic compound standard gas mixtures at varying diluent flow rates.

Commercial standard gas generators are often complex and expensive devices. The objective of this research was to assess the performance of a simplified glass impinger system for standard gas generation from a permeation tube (PT) device. The performance of the impinger standard gas generation system was assessed for four aromatic VOCs (benzene, toluene, ethylbenzene, and m-xylene; BTEX) at varying flow rates (FR) of 50 to 800 mL·min(-1). Because actual permeation rate (APR) values deviated from those computed by the manufacturer's formula (MPR), new empirical relationships were developed to derive the predicted PR (PPR) of the target components. Experimental results corrected by such a formula indicate that the compatibility between the APR and MPR generally increased with low FR, while the reproducibility was generally reduced with decreasing flow rate. Although compatibility between different PRs is at a relatively small and narrow FR range, the use of correction formula is recommendable for the accurate use of PT.

The controlling effect of temperature in the application of permeation tube devices in standard gas generation.

In this study, the performance of permeation tube (PT) devices for the generation of VOC calibration gas was examined by successively generating BTX gas at five temperatures (30, 50, 70, 80, and 100 °C) and two flow rates (400 and 800 mL min⁻¹). A distinct relationship was observed between temperatures and permeation rates (PR) (or generated BTX concentrations). We examined the reliability of the manufacturer's PR formula when operating at chamber temperatures different from the manufacturer reference temperatures for each PT device. Bias of the actual PR from the theoretical PR values became significant as PT devices were operated at temperatures beyond their optimum operating range (e.g., maximum bias of BTX as 141%, 87.2%, and 85%, respectively). Through a derivation of empirical formula, we were able to predict PR values of the target compounds more accurately as evidenced by significant bias reduction at all temperature points (e.g., maximum bias of BTX as 10.9%, 21.1% and 20.6%, respectively).

The use of permeation tube device and the development of empirical formula for accurate permeation rate.

A series of laboratory experiments were conducted to assess the accuracy of permeation tube (PT) devices using a calibration gas generator system to measure permeation rate (PR) of volatile organic compounds (VOCs). Calibration gas standards of benzene, toluene, and m-xylene (BTX) were produced from PTs at varying flow rates (FR) of 20-1200 mL min(-1) and constant temperature (30°C). Results indicate that changes in flow rate greatly affected the permeation rate of each VOC at this temperature. This paper presents experimental approaches to accurately measure actual permeation rate (APR) and the derivation of empirical equations for predicted permeation rate (PPR). If the magnitude of bias is defined as the difference between PPR and the manufacturer's permeation rate (MPR), the bias was typically 19-40% for toluene (T) and 31-54% for m-xylene (X). Benzene (B) exhibited the least bias of 1.4-18.8%, nevertheless our PPR values for benzene were more reliable at lower flow rates (0.75-1.20%). This study highlights the importance of flow rate and associated pressure changes as a key to accurate permeation rate estimation from permeation tube devices.

The modern paradox of unregulated cooking activities and indoor air quality.

Pollutant emission from domestic and commercial cooking activities is a previously neglected area of concern with respect to human health worldwide. Its health effects are relevant to people across the globe, not only those using low quality food materials in lesser-developed countries but also to more affluent people enjoying higher quality food in developed countries. Based on the available database of pollutant emissions derived from fire-based cooking, its environmental significance is explored in a number of ways, especially with respect to the exposure to hazardous vapors and particulate pollutants. Discussion is extended to describe the risk in relation to cooking methods, cooking materials, fuels, etc. The observed pollutant levels are also evaluated against the current regulations and guidelines established in national and international legislation. The limitations and future prospects for the control of cooking hazards are discussed.

The impact of mining activities in alteration of As levels in the surrounding ecosystems: an encompassing risk assessment and evaluation of remediation strategies.

A comprehensive field survey was conducted to explore the status of arsenic (As) contamination in soil and water systems surrounding numerous abandoned mine sites in Korea, which were previously applied with soil-topping (15 cm deep) and lime treatment for remediation purposes. This survey also aimed to assess the environmental stability of those reservoirs in relation to their established guidelines for As. To this end, a total of 5837 target soils (TS) were analyzed along with 305 control soils (CS) and 74 tailing (TA) samples. In addition, analyses were also extended to cover 1066 water and 329 sediment samples. Substantial evidence (e.g., differences in the mean As levels between TS (12.7 mg kg(-1)) and CS (0.69 mg kg(-1)) and the strong correlation between TS and TA) suggests a strong effect of previous mining activities. Soil-topping method was successful in confining As at the subsurface soil and restraining its dispersal. Although soil pH level also dropped with increasing As, it was restored to near neutrality by liming treatment. The mean values of As in water samples are comparable between dry (22.2) and wet seasons (21.2 mg L(-1)), while its values frequently exceeded various guideline limits. The pollution status of the current land and water systems needs to be assessed properly along with a removal plan for mine wastes/tailings to limit the dispersion of As in the study area.

Quantifying nickel in soils and plants in an ultramafic area in Philippines.

In this study, concentrations of nickel (Ni) were quantified in the soils and plants in the agricultural areas of Salcedo watershed in Eastern Samar Island, Philippines. The quantity of total Ni in soils (TS-Ni) was significantly high with a mean of 1,409 mg kg(-1), while the soil available Ni (SA-Ni) was low with a mean of 8.66 mg kg(-1). As the levels of TS-Ni in the Salcedo watershed greatly exceeded the maximum allowable concentrations for agricultural soils, the site is not suitable for agricultural purposes. Despite significant TS-Ni levels, SA-Ni levels were very low due to tight binding between Ni and soil components. Consequently, all plants investigated did not meet the criterion for a Ni hyperaccumulator plant with low Ni contents (mean TP-Ni of 14.7 mg kg(-1)). Comparison of Ni levels between food plants and its recommended daily intake (RDI) suggests that consumption of food-plants grown in the study area is unlikely to pose health risks. However, caution must be taken against combined consumption of food plants with high Ni levels or their prolonged consumption, as it can induce accumulation of Ni above RDI.

BBQ charcoal combustion as an important source of trace metal exposure to humans.

To provide information about charcoal combustion as an important source of atmospheric trace metal pollution, 11 charcoal products were combusted and PM(10) filter samples were collected. The PM-bound metal elements were extracted by microwave acid digestion and analyzed by ICP-AES. The concentrations of trace metal elements ranged from a few to 10(5)ng m(-3) in the following order of magnitude: Zn>Pb>Mg>Ba>Cu>V>Cr>Co>Cd>Ni>Mn>Se>As. Emissions of most elements from charcoal combustion were high compared to other sources. In case of Cd, Co, and Ni, their concentrations exceeded the inhalation minimum risk levels (MRLs) of the United States Agency for Toxic Substances and Disease Registry (US-ATSDR) for chronic duration exposure by a factor of 30, 3.9, and 2.2, respectively. Likewise, Cd levels exceeded the US-ATSDR MRLs for acute-duration exposure by a factor of 10, while those of Pb and Cd exceeded air quality guideline (AQG) of the World Health Organization (WHO) by a factor of 29 and 59, respectively. Mn levels also exceeded the United States Environmental Protection Agency (US EPA) Reference Air Concentrations (RfCs) by a factor of 2.7. This study shows that barbecue charcoal combustion can be an important source of trace metal emissions to the atmosphere with potential health risks.