Quantifying source apportionment for ambient haze: An image haze extraction approach with air quality monitoring data.

The annual average concentration of fine particles (PM2.5) in Taiwan has been decreasing yearly. However, ambient haze has not abated and visibility is still poor. This study proposes a method for quantifying the source apportionment of ambient haze from various constituents, namely measured PM2.5, moisture, and secondary organic aerosols (SOA, represented by the sum of measured O3 and NO2 levels). This study's model-based demisting technology integrated image haze extracting technology with air quality monitoring data. The images for haze extraction were from the instant cameras of the Taiwan Environmental Protection Agency's air quality monitoring stations (AQMSs). Results indicate that haze constituents with the product of light extinction and scene depth have very high correlation (R2 ≥ 0.8452), which demonstrate that this quantification approach was successful. The contributions of ambient haze from various constituents had quarterly and regional variations in the eastern, northern, central, and southern regions of Taiwan, which are slightly, lowly, moderately, and heavily contaminated areas, respectively. Each area was assigned a selected representative AQMS to represent its ambient haze characteristics. Cases where the dominant contributors to haze were PM2.5, moisture, and SOA were studied, in addition to the event days of PM2.5 and ozone. We detail the limits of this approach, especially with regard to the use of images. This approach can help administrators understand the composition of ambient haze to generate effective haze strategies and policies. Residents can use this method to determine the health effects of daily haze.

Environmental health risks perception, attitude, and avoidance behaviour toward municipal solid waste incinerator.

This study aims to assess the relationship between risk perception, attitude, and avoidance among residents toward an urban incinerator in Taichung, Taiwan. A cross-sectional study was conducted and three schools were enrolled. The case group was composed of 514 residents who live near an incinerator. The control group was composed of 264 people nearly the same age and who have lived in that area basically the same period of time. All participants were interviewed using a structured questionnaire. Results of this study showed that there was no significant difference between the exposure group and the control group in risk perception and attitude regarding the incinerator. However, the exposure group showed a significantly higher desire to move within one year or move sometime in the future than the control group. Therefore, these people should encourage the Environmental Protection Administration (EPA) to do everything it can to make sure that the incinerator operates safely.

A new scale-free network model for simulating and predicting epidemics.

The course of epidemics often resembles a scale-free network, but some specific elements should be considered in developing a new model. This study introduces a time-shifting and discontinuous forcing function H into the scale-free network model to fit the specific period and intensity of the infection, and redefines the probability p as abortive infection rate. For the non-human vectors or hosts, three new factors (new connectivity K(i)(t), new links M, and time delay τ) were introduced in the proposed model of this study. The simulation results of six types of epidemic transmissions show that the proposed Scale-Free Epidemic Models, SFE-1 and SFE-2, are accurate. SFE-1 model and SFE-2 model are useful for the transmission categories from human and insects/vertebrates, respectively. Further comparisons of different races/ethnicities and different transmission categories of AIDS cases in the United States were also analyzed. Both SFE models can be used to predict epidemics and can suggest the results more clearly, irrespective of whether the epidemics are under control. Therefore, the proposed SFE models can help the government determine the level of caution required and predict the results of policy decisions, thus helping to balance socioeconomic and health concerns.

The impacts of air quality and secondary organic aerosols formation on traffic accidents in heavy fog-haze weather.

This study estimated changes in the levels of three components of regional haze, namely fine particulate matter (PM2.5), relative humidity (RH), and secondary organic aerosols (SOAs), at the time of two severe traffic accidents on a coastal expressway and a freeway in the Jianan Plain in southwestern Taiwan to understand the impact of weather and air quality factors on the low visibility. Monitoring data and surveillance images from four nearby air quality monitoring stations were collected to determine the precise causes of the poor visibility-related accidents. The study applied a haze extraction method to the images to achieve demisting, and the processed data were used to assess the relationship between the haze components and visibility during the accidents. The correlation between visibility and the haze components was assessed. The results revealed that the RH levels dropped significantly at the time of the accidents, signifying that moisture was not the main haze-fog component. The haze components can be ordered as follows in terms of their correlation with (and thus effect on) local visibility: PM2.5 > SOAs > RH. The spatial distributions and evolutions of the three components indicated that the PM2.5 concentrations remained high from midnight until early morning but decreased slightly at the time of both accidents. By contrast, the concentration of ultrafine SOA particles, which can scatter and absorb light to reduce road visibility, increased rapidly before both accidents. Therefore, PM2.5 and SOAs were two non-negligible factors of low visibility during the accidents, especially SOAs.

Quantification of the impact of the offshore petrochemical industrial park on ambient ozone using photochemical grid modeling and assessment monitoring.

This study integrated the results of photochemical grid modeling and assessment monitoring to quantify the impact of the offshore petrochemical industrial park (OPIP), with area of 26.03 km2, on ambient ozone in a coastal region of Taiwan. A highly repetitive ozone-spreading phenomenon in the adjacent OPIP area was observed, which shows that ozone spreading follows a clear cycle between offshore and inland areas during the prevailing periods of ozone events (≥ 120 ppb). The incremental ratio of ambient ozone for the OPIP on ozone event days during the southwest and northeast monsoons in 2011-2016 ranged from 1.05 to 1.25 (average = 1.15) and 1.04-1.27 (average = 1.17), respectively. Data from ten photochemical assessment monitoring stations surrounding the OPIP in 2016 showed that the ratio of monthly average concentrations of volatile organic compounds (VOCs) during the northeast monsoon to the southwest monsoon was approximately 1.5. The ratio of the monthly latent incremental amount of ozone to the total volatile organic amount in the same month during the northeast and southwest monsoons was in the ranges of approximately 0.84-0.97 and 1.01-1.12, respectively. Moreover, the latent incremental amount of ozone during the daytime was greater than that at night. The results indicate that the observed ozone concentration increases as the latent incremental amount of ozone or ambient VOCs decreases.

An evaluation approach for livable urban environments.

This study proposes a method for evaluating livable urban environments using the analytic hierarchy process, a survey of public opinions (n=1,075), and gray relational analysis with a pollutant standards index to estimate the weights of weather, air pollution, and environment aspects and each respective factor. This study investigates the positive or negative correlation of these factors and their effects on livable environment. A value of 100 was designated as the perfect living condition. Results show that the weights of weather, air pollution, and environment aspects were 0.288, 0.395, and 0.317, respectively. The weight ranges of three weather factors, five air pollution factors, and ten environmental factors were 0.311-0.358, 0.191-205, and 0.081-0.116, respectively. The monthly livable index of 28 districts in Taichung City and of 20 cities/counties in Taiwan ranged from 81.1 to 92.4 and from 83.1 to 90.8 in different months, respectively, showing that environmental aspect played a key role. These results demonstrate that the proposed method can provide a quantification index of living conditions in each region, thereby establishing the governmental improvement policy firmly. This study also presents a discussion on improvement strategies, especially on the apportionment rate of governmental construction funds for livable urban environments.

Integrated chemical species analysis with source-receptor modeling results to characterize the effects of terrain and monsoon on ambient aerosols in a basin.

This study integrated estimated oxidation ratio of sulfur (SOR) and oxidation ratio of nitrogen (NOR) with source-receptor modeling results to identify the effects of terrain and monsoons on ambient aerosols in an urban area (north basin) and a rural area (south basin) of the Taichung Basin. The estimated results indicate that the conversion of sulfur mainly occurs in fine particles (PM2.5), whereas the conversion of nitrogen occurs in approximately equal quantities of PM2.5 and coarse particles (PM2.5-10). The results show a direct relationship for PM2.5 between the modeling results with SOR and NOR. The high PM2.5 SOR, NOR, and secondary aerosol values all occurred in the upwind area during both monsoons; this shows that the photochemical reaction and the terrain effect on the pollutant transmission were significant in the basin. Additionally, the urban heat island effect on the urban area and the valley effect on the rural area were significant. The results show that secondary aerosol in PM2.5-10 contributed approximately 10 % during both monsoons, and the difference in the contribution from secondary aerosol between both areas was small. Vehicle exhaust emissions and wind-borne dust were two crucial PM2.5-10 contributors during both monsoons; their average contributions in both areas were higher than 34 and 32 %, respectively.

Using a source-receptor approach to characterize the volatile organic compounds from control device exhaust in a science park.

The science parks have helped shape Taiwan as a high-tech island with a good reputation worldwide. But some complaints on air pollution from the science parks have recently risen. To better understand the environmental effects of volatile organic compounds (VOCs) emitted from various high-tech factories in a science park, this study uses a source-receptor approach to characterize the environmental effects of VOCs from control device exhaust in Taichung Science Park. The chemical mass balance model (CMB8.2) of field measurements of 30 stacks and ambient air at nine sites was used to identify the source and relative contribution of ambient VOCs. The exhaust gas of various pollution control devices was also sampled by drawing a stream of the gases from the exhaust duct at its sampling port. The VOC source profile of each control device exhaust was determined using a database of noncharacteristic compounds. Monthly ambient concentrations of 167 VOCs were divided into monsoon datasets to investigate the effect of monsoon conditions on the emission of VOCs in the science park. This study also suggests a method for determining the optimum source profile in source-receptor modeling, and identifies and analyzes the sources of ambient VOCs at nine sites during southwest and northeast monsoons. Results show a direct relationship between the relative contribution of each source and its control device efficiency. The proposed source-receptor approach can characterize the environmental effect of air pollutants from various factories and successfully assess the efficiency of various control devices.

The scale-free network behavior of ambient volatile organic compounds.

A scale-free network model with surface and vertical field measurements was used to identify the connectivity distribution of the scale-free network behavior of ambient volatile organic compounds (VOCs). The results show that the carbon number (C(n)) with the total amount of C(n) compounds (P(C(n))) possesses an explicit relationship with the scale-free network behavior. The proportionate coefficient (α) and exponent (γ) of the scale-free network model with spatial and temporal variations are estimated and discussed. The analytical results demonstrate that although photochemical reactions cause the VOCs fraction variation, they do not alter the fraction of C(n) compounds observably. Therefore, the values of α and of γ did not vary with time, but with local regional characteristics. The results indicate that the influence of local VOCs emissions occurs at a height of 100 m, but becomes insufficient at a height of 300 m. Air mass mixing increases with greater height; thus, the influence of regional characteristics at a height of 700 m is low. Finally, a successful empirical model was established to evaluate the distribution of surface VOCs in various regions.

Effects of basin topography and monsoon conditions on transport and occurrence of atmospheric PCDD/Fs in the Taichung Basin.

BACKGROUND, AIM, AND SCOPE: Topographical and meteorological factors, such as monsoons, can drastically affect ambient dioxin levels. In order to better understand these phenomena, four sampling lines (comprising 16 sampling sites) were selected in accordance with the topographical characteristics and the transport paths of the Taichung Basin. MATERIALS AND METHODS: The ambient air samples were simultaneously collected according to US EPA TO-9A. Seventeen polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed by a high-resolution gas chromatograph/high-resolution mass spectrometer. RESULTS: Field measurements indicated that, during monsoons, PCDD/Fs concentrations varied from 128 to 4,230 fg m(-3). Two locations, the pass between two tablelands and the valley in front of a mountain, had the highest PCDD/Fs concentrations; those concentrations were about two to five times greater than the average concentration. There were 189 analyses of 11 kinds of PCDD/Fs emission sources used to develop emission fingerprints for a CMB8.2 simulation. Chemical mass balance (CMB8.2) model simulation with PCDD/Fs and surface wind field measurements were performed. Results of CMB8.2 modeling indicated that the major source of most sites was secondary copper smelting. CONCLUSIONS: The CMB8.2 model indicated the effects of hills and river valleys on pollutant transport. Results indicated that secondary copper smelting must be controlled to reduce the ambient concentrations of PCDD/Fs in the Taichung Basin.