Abstract. The analysis of gaseous criteria pollutants in the Bangkok
Metropolitan Region (BMR), Thailand, from 2010 to 2014 reveals that while the
hourly concentrations of CO, SO2 and NO2 were mostly
within the National Ambient Air Quality Standards (NAAQs) of Thailand, the
hourly concentrations of O3 frequently exceeded the standard. The
results reveal that the problem of high O3 concentration
continuously persisted in this area. The O3 photolytic rate
constant (j1) for BMR calculated based on assuming a photostationary
state ranged from 0.008 to 0.013 s−1, which is similar to the
calculated j1 using the NCAR TUV model (0.021±0.0024 s−1).
Interconversion between O3, NO and NO2 indicates that
crossover points between the species occur when the concentration of
NOx (= NO + NO2) is ∼60 ppb. Under a
low-NOx regime ([NOx] < 60 ppb),
O3 is the dominant species, while, under a
high-NOx regime ([NOx]
> 60 ppb), NO dominates. Linear regression analysis between the
concentrations of Ox (= O3 + NO2)
and NOx provides the role of local and regional
contributions to Ox. During O3 episodes
([O3]hourly > 100 ppb), the values of the
local and regional contributions were nearly double of those during
non-episodes. Ratio analysis suggests that the major contributors of primary
pollutants over BMR are mobile sources. The air quality index (AQI) for BMR
was predominantly good to moderate; however, unhealthy O3
categories were observed during episode conditions in the region.
Abstract. Analysis of gaseous criteria pollutants in Bangkok Metropolitangood to moderate. Unhealthy O3 categories were observed during episode conditions in the region.
Ambient concentrations of both fine particulate matter (PM 2.5 ) and particulate matter with an aerodynamic diameter less than 10 micron (PM 10 ) were measured from 10 June 2015 to 13 July 2015 at three locations surrounding the Cheswick Power Plant, which is located between the boroughs of Springdale and Cheswick, Pennsylvania. The average concentrations of PM 10 observed during the periods were 20.5 ± 10.2 µg m −3 (Station 1), 16.1 ± 4.9 µg m −3 (Station 2) and 16.5 ± 7.1 µg m −3 (Station 3). The average concentrations of PM 2.5 observed at the stations were 9.1 ± 5.1 µg m −3 (Station 1), 0.2 ± 0.4 µg m −3 (Station 2) and 11.6 ± 4.8 µg m −3 (Station 3). In addition, concentrations of PM 2.5 measured by four Pennsylvania Department of Environmental Protection air quality monitors (all within a radius of 40 miles) were also analyzed. The observed average concentrations at these sites were 12.7 ± 6.9 µg m −3 (Beaver Falls), 11.2 ± 4.7 µg m −3 (Florence), 12.2 ± 5.3 µg m −3 (Greensburg) and 12.2 ± 5.5 µg m −3 (Washington). Elemental analysis for samples (blank -corrected) revealed the presence of metals that are present in coal (i.e., antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel and selenium).
Biogenic volatile organic compounds (BVOC), which are mainly emitted from plants, are a major precursor for the formation of ground-level ozone (O3) and secondary organic aerosols (SOA). In the northern region of Thailand, 63.8% of the land area is covered by forests. Herein we investigated the effects of biogenic volatile organic compounds (BVOC) emitted from plants and anthropogenic NOx emissions on ground-level ozone (O3) and fine particulate matters (PM2.5) formation. The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem Model) was applied to simulate three scenarios including baseline, noBio and modiAntho simulations. The modeling results over the northern region of Thailand indicate that BVOC emissions over the northern region of Thailand contributed only 5.3%–5.6% of the total concentrations of PM2.5 and BVOC had a direct relationship to glyoxal and SOA of glyoxal. The comparison between the observed and the modeled isoprene over the study site showed an underestimation (3- to 4-folds) of the simulated concentrations during the study period (June and November 2021). In June, decreases in anthropogenic NOx emissions by 40% led to PM2.5 reductions (5.3%), which corresponded to a zero BVOC emission scenario. While higher PM2.5 reductions (5.6%) were found to be caused by anthropogenic NOx reductions in November, small increases in PM2.5 were observed over the area near a power plant located in Lampang Province. Therefore, both VOC and NOx emission controls may be necessary for areas near the lignite mine and power plant. Since the areas within the vicinity of the power plant were under VOC-limited regimes, while the other areas were determined to be NOx-limited.
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