Nitrate formation mechanisms causing high concentration of PM2.5 in a residential city with low anthropogenic emissions during cold season.

During the cold season in South Korea, NO3- concentrations are known to significantly increase, often causing PM2.5 to exceed air quality standards. This study investigated the formation mechanisms of NO3- in a suburban area with low anthropogenic emissions. The average PM2.5 was 25.3 µg m-3, with NO3- identified as the largest contributor. Ammonium-rich conditions prevailed throughout the study period, coupled with low atmospheric temperature facilitating the transfer of gaseous HNO3 into the particulate phase. This result indicates that the formation of HNO3 played a crucial role in determining particulate NO3- concentration. Nocturnal increases in NO3- were observed alongside increasing ozone (O3) and relative humidity (RH), emphasizing the significance of heterogeneous reactions involving N2O5. NO3- concentrations at the study site were notably higher than in Seoul, the upwind metropolitan area, during a high concentration episode. This difference could potentially attributed to lower local NO concentrations, which enhanced the reaction between O3 and NO2, to produce NO3 radicals. High concentrations of Cl- and dust were also identified as contributors to the elevated NO3- concentrations.

Variations of oxidative potential of PM2.5 in a medium-sized residential city in South Korea measured using three different chemical assays.

Although it is evident that PM2.5 has serious adverse health effects, there is no consensus on what the biologically effective dose is. In this study, the intrinsic oxidative potential (OPm) and the extrinsic oxidative potential (OPv) of PM2.5 were measured using three chemical assays including dithiothreitol (DTT), ascorbic acid (AA), and reduced glutathione (GSH), along with chemical compositions of PM2.5 in South Korea. Among the three chemical assays, only OPmAA showed a statistically significant correlation with PM2.5 while OPmGSH and OPmDTT were not correlated with PM2.5 mass concentration. When the samples were categorized by PM2.5 mass concentrations, the variations in the proportion of Ni, As, Mn, Cd, Pb, and Se to PM2.5 mass closely coincided with changes in OPm across all three assays, suggesting a potential association between these elements and PM2.5 OP. Multiple linear regression analysis identified the significant PM components affecting the variability in extrinsic OPv. OPvAA was determined to be significantly influenced by EC, K+, and Ba while OC and Al were common significant factors for OPvGSH and OPvDTT. It was also found that primary OC was an important variable for OPvDTT while secondary OC significantly affected the variability of OPvGSH.

Long-term exposure to PM10 and NO2 in relation to lung function and imaging phenotypes in a COPD cohort.

BACKGROUND: Ambient air pollution can contribute to the development and exacerbation of COPD. However, the influence of air pollution on objective COPD phenotypes, especially from imaging, is not well studied. We investigated the influence of long-term exposure to air pollution on lung function and quantitative imaging measurements in a Korean cohort of participants with and without COPD diagnosis. METHODS: Study participants (N = 457 including 296 COPD cases) were obtained from the COPD in Dusty Areas (CODA) cohort. Annual average concentrations of particulate matter less than or equal to 10 µm in diameter (PM10) and nitrogen dioxide (NO2) were estimated at the participants' residential addresses using a spatial air pollution prediction model. All the participants underwent volumetric computerized tomography (CT) and spirometry measurements and completed survey questionnaires. We examined the associations of PM10 and NO2 with FVC, FEV1, emphysema index, and wall area percent, using linear regression models adjusting for age, gender, education, smoking, height, weight, and COPD medication. RESULTS: The age of study participants averaged 71.7 years. An interquartile range difference in annual PM10 exposure of 4.4 µg/m3 was associated with 0.13 L lower FVC (95% confidence interval (CI), - 0.22- -0.05, p = 0.003). Emphysema index (mean = 6.36) was higher by 1.13 (95% CI, 0.25-2.02, p = 0.012) and wall area percent (mean = 68.8) was higher by 1.04 (95% CI, 0.27-1.80, p = 0.008). Associations with imaging phenotypes  were not observed with NO2. CONCLUSIONS: Long-term exposure to PM10 correlated with both lung function and COPD-relevant imaging phenotypes in a Korean cohort.

Epidemiological study of PM2.5 and risk of COPD-related hospital visits in association with particle constituents in Chuncheon, Korea.

Background and objective: Aside from smoking, which is already recognized as a strong risk factor for COPD, interest in the impact of particulate matter (PM) on COPD is increasing. This study aimed to investigate the effect of PM, especially with an aerodynamic diameter ≤2.5 µm (PM2.5), and its chemical constituents on the exacerbation of COPD. Methods: Data on hospital visits including admission and outpatient clinic visits for exacerbation of COPD in Chuncheon, Korea, between 2006 and 2012 were extracted from the National Health Insurance Service database. PM2.5 and its chemical constituents were measured on the roof of the four-story Kangwon National University Natural Sciences building once every 3 days. Meteorological data were provided by the Korean Meteorological Administration. Results: During the study period, the mean level of PM2.5 was 35.0±25.2 µg/m3, and the number of daily hospital visits were 6.42±4.28 and 2.07±1.93 for males and females, respectively. The number of COPD-related hospital visits increased with increasing PM2.5 after adjusting for meteorological covariates and females tended to be more affected sooner than males. Among the PM2.5 constituents, Al, Si, and elemental carbon were associated with increased hospital visits and there was a difference according to sex. In males, some constituents of PM2.5 were related to an increased risk of a hospital visit, mainly on the first and second days of measurement (Lag1 and Lag2). In contrast, there was no significant increase in the risk of hospital visits due to any of the PM2.5 constituents in females. Conclusion: Concentrations of PM2.5 mass and some of the PM2.5 constituents were associated with increased COPD-related hospital visits in Chuncheon.

Emergency Department Visits for Asthma Exacerbation due to Weather Conditions and Air Pollution in Chuncheon, Korea: A Case-Crossover Analysis.

PURPOSE: This retrospective study was conducted to estimate the effects of climate factors and air pollution on asthma exacerbations using a case-crossover analysis. METHODS: Patients who visited the emergency department (ED) of 2 university hospitals in Chuncheon for asthma exacerbations from January 1, 2006, to December 31, 2011, were enrolled. Daily average data for meteorological factors (temperature, daily temperature range, relative humidity, wind speed, atmospheric pressure, presence of rain, solar irradiation, and presence of fog) and the daily average levels of gaseous air pollutants (SO2, NO2, O3, CO, and PM10) were obtained. A case-crossover analysis was performed using variables about the weather and air pollution at 1-week intervals between cases and controls before and after ED visits. RESULTS: There were 660 ED visits by 583 patients with asthma exacerbations. Low relative humidity (lag 1 and 2) and high wind speed (lag 1, 2, and 3) were associated with ED visits for asthma. Fog (lag 2) showed protective effects against asthma exacerbations in Chuncheon (risk increase: -29.4% [95% CI=-46.3% to -7.2%], P=0.013). These relationships were stronger in patients ≤19 years old than in those >60 years old. High levels of ambient CO (lag 1, 2, and 3) and NO2 (lag 2 and 3) were associated with decreased ED visits for asthma. However, there were no significant relationships among levels of ambient CO or NO2 and asthma exacerbations after adjusting for wind speed and relative humidity. CONCLUSIONS: High wind speed and low humidity were associated with an increased risk of asthma ED visits. Fog was associated with a decreased risk of asthma ED visits after controlling for seasonal variations in weather and air pollution.

A Mixture of Ethanol Extracts of Persimmon Leaf and Citrus junos Sieb Improves Blood Coagulation Parameters and Ameliorates Lipid Metabolism Disturbances Caused by Diet-Induced Obesity in C57BL/6J Mice.

This study investigated the effects of a flavonoid-rich ethanol extract of persimmon leaf (PL), an ethanol extract of Citrus junos Sieb (CJS), and a PL-CJS mixture (MPC) on mice fed a highfat diet (HFD). We sought to elucidate the mechanisms of biological activity of these substances using measurements of blood coagulation indices and lipid metabolism parameters. C57BL/6J mice were fed a HFD with PL (0.5% (w/w)), CJS (0.1% (w/w)), or MPC (PL 0.5%, CJS 0.1% (w/w)) for 10 weeks. In comparison with data obtained for mice in the untreated HFD group, consumption of MPC remarkably prolonged the activated partial thromboplastin time (aPTT) and prothrombin time (PT), whereas exposure to PL prolonged aPTT only. Lower levels of plasma total cholesterol, hepatic cholesterol, and erythrocyte thiobarbituric acid-reactive substances, hepatic HMG-CoA reductase, and decreased SREBP-1c gene expression were observed in mice that received PL and MPC supplements compared with the respective values detected in the untreated HFD animals. Our results indicate that PL and MPC may have beneficial effects on blood circulation and lipid metabolism in obese mice.

Mercury wet deposition in the eastern United States: characteristics and scavenging ratios.

Wet deposition is an important atmospheric mercury (Hg) pathway between air and terrestrial ecosystems. It is measured at numerous locations in the United States (U. S.) as part of the Mercury Deposition Network (MDN). The annual Hg wet deposition flux in 2009 at four locations in the northeastern U. S. (MDN sites MD08, VT99, NY20, and NY43) ranged from 6.4 to 13.4 µg per m(2) year which is higher than modeled reactive Hg (RM) dry deposition for this region. The highest ambient RM concentrations were seen at MD08, which is closest to significant anthropogenic sources; however, the volume-weighted mean Hg concentrations in precipitation were similar at these four sites. Mass based scavenging ratios (SC) of RM ranged from 1700 to 4500. Differences in SCs were likely a result of differences in meteorological conditions, the forms of RM in the atmosphere, vertical concentration variations, and measurement uncertainties, including precipitation depth and RM concentrations. RM SCs were higher than those reported for other soluble species. Multiple linear regression suggests that gaseous oxidized Hg is responsible for the majority of the scavenged RM.

Mercury wet deposition in rural Korea: concentrations and fluxes.

The characteristics of Hg wet deposition were investigated in a rural area of Korea from August 2006 to July 2008. The volume weighted mean (VWM) Hg(T) concentration and cumulative Hg(T) flux were 8.8 ng L(-1) and 9.4 µg m(-2) per year, respectively. The VWM Hg(T) concentration varied seasonally, similar to the seasonal pattern in atmospheric Hg(p) concentration. The enhancement of both VWM Hg(T) and atmospheric Hg(p) concentrations in spring and winter was likely caused by the long-range transport of Hg from China. Monthly VWM Hg(T) and atmospheric Hg(p) concentrations were well correlated (R(2) = 0.36); however, there was no correlation between VWM Hg(T) and RGM (reactive gaseous mercury) concentrations, suggesting that Hg(p) was responsible for the majority of the Hg in wet deposition at this site. The VWM Hg(T) concentration in snow was statistically higher than in rain. In addition, the atmospheric Hg(p) concentration appeared to be elevated for snow events as well. This suggests that both elevated Hg(p) concentrations and the enhanced scavenging efficiency of snow for Hg(p) were responsible for the elevated VWM Hg(T) concentrations measured during snow events.

Factors influencing concentrations of dissolved gaseous mercury (DGM) and total mercury (TM) in an artificial reservoir.

The effects of various factors including turbidity, pH, DOC, temperature, and solar radiation on the concentrations of total mercury (TM) and dissolved gaseous mercury (DGM) were investigated in an artificial reservoir in Korea. Episodic total mercury accumulation events occurred during the rainy season as turbidity increased, indicating that the TM concentration was not controlled by direct atmospheric deposition. The DGM concentration in surface water ranged from 3.6 to 160 pg/L, having a maximum in summer and minimum in winter. While in most previous studies DGM was controlled primarily by a photo-reduction process, DGM concentrations tracked the amount of solar radiation only in winter when the water temperature was fairly low in this study. During the other seasons microbial transformation seemed to play an important role in reducing Hg(II) to Hg(0). DGM increased as dissolved organic carbon (DOC) concentration increased (p-value < 0.01) while it increased with a decrease of pH (p-value < 0.01).

Reduced mercury deposition in New Hampshire from 1996 to 2002 due to changes in local sources.

Changes in deposition of gaseous divalent mercury (Hg(II)) and particulate mercury (Hg(p)) in New Hampshire due to changes in local sources from 1996 to 2002 were assessed using the Industrial Source Complex Short Term (ISCST3) model (regional and global sources and Hg atmospheric reactions were not considered). Mercury (Hg) emissions in New Hampshire and adjacent areas decreased significantly (from 1540 to 880 kg yr(-1)) during this period, and the average annual modeled deposition of total Hg also declined from 17 to 7.0 microg m(-2) yr(-1) for the same period. In 2002, the maximum amount of Hg deposition was modeled to be in southern New Hampshire, while for 1996 the maximum deposition occurred farther north and east. The ISCST3 was also used to evaluate two future scenarios. The average percent difference in deposition across all cells was 5% for the 50% reduction scenario and 9% for the 90% reduction scenario.

Comparison between back-trajectory based modeling and Lagrangian backward dispersion modeling for locating sources of reactive gaseous mercury.

Reactive gaseous mercury (RGM) was measured using an annular denuder coated with potassium chloride at three rural sites (Potsdam, Stockton, and Sterling) in New York State from April 2002 to April 2003. Concentrations of RGM ranged from 0.1 to 84.6 pg m(-3) with large spatial and temporal variation. Potential source contribution function (PSCF), a common receptor modeling tool, was used with these measurements, and source-receptor relationships were calculated using back-dispersion and deposition as well as back-trajectories. Modeling results were compared with the RGM emissions inventory, and Spearman rank-order correlation coefficients were calculated. PSCF results incorporating backward dispersion and deposition were better correlated with the emissions inventory than PSCF based on back-trajectories alone. This difference was determined to be mainly due to the inclusion of dispersion rather than deposition. The main sources of RGM were suggested to be coal-fired power plants in New York and Pennsylvania, the large copper smelter in Quebec, and the taconite mining areas around the Great Lakes.

Measured summertime concentrations of particulate components, Hg0, and speciated polycyclic aromatic hydrocarbons at rural sites in New York State.

Daily PM2.5 samples, Hg0 and speciated polycyclic aromatic hydrocarbon (PAH) were simultaneously collected at Potsdam and Stockton site in NY during the summers of 2000 and 2001. Samples for determination of the mass concentration and chemical composition of the PM2.5 were obtained with a speciation network PM2.5 sampler. Chemical composition including trace elemental composition, water-soluble ions, and elemental carbon were analyzed. Elemental mercury and PAHs were sampled separately. Daily PM2.5 concentrations ranged from 0.47 to 53.7 microg m(-3) at the Potsdam site, and from 0.82 to 47.23 microg m(-3) at the Stockton site with large daily differences between the two sites. Potsdam consistently had lower mass values than Stockton. The greatest contributors to the PM2.5 mass (generally >0.1 microg/m(3)) were sulfate, nitrate, ammonium, and BC at both sites. Seventeen PAHs were identified at each site in 2000 and the average total concentrations were 3.2 ng/m(3) and 2.9 ng/m(3) at the Potsdam and Stockton sites, respectively. The mean vapor phase mercury concentration at the Potsdam site (2.4 +/-1.2 ng m(-3), n=93) was higher than that at the Stockton site (1.2 +/- 1.0 ng m(-3), n=60) in 2000, whereas in 2001, the average concentrations were 1.1 ng m(-3) and 1.6 ng m(-3) at the Potsdam and Stockton sites, respectively. In general, vapor phase mercury concentrations increased with increasing ambient temperature at the Stockton site in 2000. These differences in values between 2000 and 2001 can be largely explained by distinct differences in the meteorological regimes that dominated in the different years.