Contributions Of Source Regions Research Articles

Assessing the impacts of rice terraces and ponds on the sediment and phosphorus loads in a typical hilly watershed of three gorge reservoir, China

Phosphorus is the primary eutrophication cause of river, lake, reservoir and estuary and it may be one of the principal pollutants for the agricultural watershed with middle and small cities. The sediment and phosphorus loads, related migration paths and contribution of source regions to receiving waters at different sections of a river basin are not clear. The modified Soil and Water Assessment Tool (SWAT) model was utilized to investigate the phosphorus loads and the relationships among water resources, sediment, and phosphorus loads in one of the important tributaries of the Three Gorge Reservoir (TGR) of China, and to investigate the retention dynamics of phosphorus in the river continuum and the influencing factors. It showed that under the scenario of rice terraces and ponds, the annual sediment loss and total phosphorus load were 125t and 2.5t, being reduced by 40%–80% compared to the natural slope scenario; the daily peak value of suspended sediment load was reduced by 30%–75%, and the relationship between the rainfall and runoff was weakened slightly; the retention rate of phosphorus sources reached 40%–78%. The results confirm that the rice terraces and ponds have altered local hydrological conditions, enhanced a substantial water, sediment, and phosphorus retention capacity that is highly consistent over time and space scales, thereby altering the predominant forms of phosphorus and improving the environmental resilience in soil and nutrition loss for the hilly watershed of the TGR.

A Highly Homogeneous Airborne Fungal Community around a Copper Open Pit Mine Reveals the Poor Contribution Made by the Local Aerosolization of Particles.

Fungi are ubiquitous and metabolically versatile. Their dispersion has important scientific, environmental, health, and economic implications. They can be dispersed through the air by the aerosolization of near surfaces or transported from distant sources. Here, we tested the contribution of local (scale of meters) versus regional (kilometers) sources by analyzing an airborne fungal community by ITS sequencing around a copper mine in the North of Chile. The mine was the regional source, whereas the soil and vegetal detritus were the local sources at each point. The airborne community was highly homogeneous at ca. 2000 km2, impeding the detection of regional or local contributions. Ascomycota was the dominant phylum in the three communities. Soil and vegetal detritus communities had lower alpha diversity, but some taxa had abundance patterns related to the distance from the mine and altitude. On the contrary, the air was compositionally even and unrelated to environmental or spatial factors, except for altitude. The presence of plant pathogens in the air suggests that other distant sources contribute to this region's airborne fungal community and reinforces the complexity of tracking the sources of air microbial communities in a real world where several natural and human activities coexist.

Contribution of regional versus trans-regional anthropogenic sources to the particulate matter over western India derived from high-resolution modeling

Elevated concentrations of particulate matter (PM) significantly deteriorate the air quality; however, the contributions from regional versus remote anthropogenic sources have remained uncertain over the western Indian region. In this regard, we have performed high-resolution regional modeling (WRF-Chem v3.9.1) to quantify the contribution of regional versus trans-regional anthropogenic sources to PM2.5 (fine PM) and PM2.5-10 (coarse PM) concentrations in contrasting seasons. Seasonal variability in spatial mean Aerosol Optical Depth (AOD) derived from the WRF-Chem model (0.21-0.42) agreed reasonably with MERRA-2 reanalysis (0.29-0.54) and MODIS satellite (0.23-0.51) over western India. Variability in surface PM2.5 and PM10 concentrations were also reproduced as per the benchmarks (|Fractional Bias| ≤ 60% and |Fractional Error| ≤ 75%) at most of the stations in this region. Results from sensitivity simulations reveal the dominant contribution of both regional and trans-regional anthropogenic sources to PM2.5 concentrations over western India in winter and post-monsoon, when PM2.5 concentrations are generally high. On the other hand, contribution from background levels (due to domain-wide natural emissions, fire emissions and pollutant transport from beyond domain boundaries) is highest during pre-monsoon and monsoon with a significant contribution of mineral dust especially to PM2.5-10 (coarse PM). Analysis of PM spatial distribution at ∼900hpa pressure level reveals greater relative contributions of trans-regional emissions and background levels compared to that near the surface. Our study highlights key roles of trans-regional anthropogenic emissions and mineral dust, besides the local and regional emissions, in air pollution over western India. The quantitative analyses presented here would be useful for designing measures to minimize health and environmental impacts in line with the objectives of the National Clean Air Programme (NCAP) in India.

Comparative Receptor Models Using Principal Component Analysis/Absolute Principal Component Scores and Positive Matrix Factorization to Assess Source Apportionment of PM2.5-10 and PM2.5 in Urban Cities

b Source apportionment of PM2.5-10 and PM2.5 was conducted using two receptor models: the principal component analysis/absolute principal component scores (PCA/APCS) and the positive matrix factorization (PMF). Methods: The PCA/APCS model resolved four sources, namely, mineral dust, sea salt/secondary sulfur, a mixed source, and traffic and industry emissions. PMF model also resolved four sources of the same origin based on the proportion of each component from the analysis. All models identified the main sources that contribute to PM2.5-10 and PM2.5 emissions and reconfirmed that the potential sources were the dominants in particulate matter in the Capital city. Findings: The first four extracted component accounted for nearly 88.3% of the variability of the data set. The running matrix elements used for data processing within collected air particulate matter was BC, Na, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Ba, and Pb. This discrimination of the area of Dakar cites according to the PCA/APCS results confirms the impact that the major activities have on the environment in the most appropriate way, and it verifies the results of previous studies about the influence of Industry emissions, mineral dust, traffic emissions and sea salt/secondary sulfur on the surrounding urban areas. Novelty: Continued collection of speciation data at the urban areas will enhance the understanding of local versus regional source contributions for air quality index in sub-Sahara region. Keywords: Aerosol, Particulate Matter, Source apportionment, receptor Modelling, XRF, heavy metals

Regional source apportionment of trace metals in fine particulate matter using an observation-constrained hybrid model

Trace metals in fine particulate matter (PM2.5) are of significant concern in environmental chemistry due to their toxicity and catalytic capability. An observation-constrained hybrid model is developed to resolve regional source contributions to trace metals and other primary species in PM2.5. In this method, source contributions to primary PM2.5 (PPM2.5) from the Community Multiscale Air Quality (CMAQ) Model at each monitoring location are improved to align better with the observation data by applying source-specific scaling factors estimated from a unique regression model. The adjusted PPM2.5 predictions and chemical speciation data are then used to generate observation-constrained source profiles of primary species. Finally, spatial distributions of their source contributions are produced by multiplying the improved CMAQ PPM2.5 contributions with the deduced source profiles. The model is applied to the Pearl River Delta (PRD) region, China using daily observation data collected at multiple stations in 2015 to resolve source contributions to 8 trace metals, elemental carbon, primary organic carbon, and 10 other primary species. Compared to three previous methods, the new model predicts 13 species with smaller model errors and 16 species with less model biases in 10-fold cross validation analysis. The source profiles determined in this study also show good agreement with those collected from the literature. The new model shows that during 2015 in the PRD region, Cu is mainly from the area sources (31%), industry sector (27%), and power generation (20%), with an annual average concentration as high as 50 ng m−3 in some districts. Meanwhile, major contributors to Mn are area sources (40%), emission from outside PRD (23%) and power generation (17%), leading to a mean level of around 10 ng m−3. Such information is essential in assessing the epidemiological impacts of trace metals as well as formulating effective control measures to protect public health.

Regional source contributions to fine particulate matter of less studied cities in Beijing-Tianjin-Hebei region in 2017

Located in the central area of the North China Plain, the Beijing-Tianjin-Hebei region experiences severe air pollution, especially for Hebei province with five cities among the top 10 cities with the worst air quality nationwide. However, less studies have investigated local and regional contributions to cities in Hebei in comparison to Beijing and Tianjin. In this study, a source-oriented version of the Community Multiscale Air Quality (CMAQ) model is used to quantify inter- and intra-province transport of PM2.5 in 11 cities within Hebei in 2017. PM2.5 and its components vary seasonally with high levels in winter and low levels in summer. Local contributions to total PM2.5 within cities are 23%–61%, while intra-province transport contributes 10%–30%, and inter-province transport contributes 23%–46%, with top contributors of Shandong (4%–22%), Henan (3%–15%) and Shanxi (2%–11%). The primary components in most cities are mainly from local sources (30%–80%), and the secondary components are mainly from inter-province contributions (30%–66%). Local sources have the highest contributions to total PM2.5 in Shijiazhuang (∼49%), followed by Shanxi (∼12%) and Xingtai (∼7%). Secondary components from local and intra-province emissions are the major cause of heavy pollution events. These results suggest that both local and regional joint control measures with neighboring cities and provinces are necessary for pollution reduction in Hebei cities.

Local and regional sources of urban ambient PM2.5 exposures in Calgary, Canada

Ambient fine size fraction particulate matter (PM2.5) sources in the western Canada city of Calgary, Alberta were identified and their contributions quantified for 2015–2019 based on elemental and ion composition data from sampling at a central monitoring site and the US Environmental Protection Agency Positive Matrix Factorization (v5.0) receptor model. Meaningful source apportionment results were obtained by using reconstructed PM2.5 mass and an estimated unmeasured mass in absence of carbonaceous component measurements. Auxiliary analyses identified source regions. Identified source types and average contribution to PM2.5 were secondary organic aerosol (24%), wood smoke (16%), soil/crustal matter (15%), traffic/rail (14%), particulate sulfate (13%), particulate nitrate (10%), and road salt/aged road salt (9% combined). Calgary PM2.5 contributions of secondary organic aerosol, particulate sulfate, and traffic/rail sources were similar to the next-nearest western city of Edmonton while particulate nitrate contributions were lower, wood smoke impacts greater and other factors showed greater inter-city differences. Secondary PM2.5 contributions in Calgary were consistent with estimates for medium and large cities in central Canada for SOA and particulate nitrate but lower for particulate sulfate. Primary wood smoke PM2.5 contributions were consistent with other Canadian cities and confirmed strong influence of winter season biomass burning. Combined on-road vehicle and rail transportation activity were found to contribute comparably more to ambient PM2.5 in Calgary than in central Canadian cities. Soil/crustal re-suspension/transport and intensive winter-time use of road salts were also important local PM2.5 sources. Several factors were characterized by local sources (traffic/rail, soil/crustal matter, road salt, aged road salt, wood smoke) with episodic regional source contributions (wood smoke, soil/crustal matter) and secondary aerosol factors (SOA, particulate sulfate, particulate nitrate) also demonstrated influence from local sources alongside regional source contributions, indicating that Calgary ambient PM2.5 concentrations are likely strongly influenced by local source emissions. These findings present positive opportunities for multiple air quality management and source mitigation strategies, including at the local/municipal level.

Enhancements in Ammonia and Methane from Agricultural Sources in the Northeastern Colorado Front Range Using Observations from a Small Research Aircraft.

Quantifying ammonia (NH3) to methane (CH4) enhancement ratios from agricultural sources is important for understanding air pollution and nitrogen deposition. The northeastern Colorado Front Range is home to concentrated animal feeding operations (CAFOs) that produce large emissions of NH3 and CH4. Isolating enhancements of NH3 and CH4 in this region due to agriculture is complicated because CAFOs are often located within regions of oil and natural gas (O&NG) extraction that are a major source of CH4 and other alkanes. Here, we utilize a small research aircraft to collect in situ 1 Hz measurements of gas-phase NH3, CH4, and ethane (C2H6) downwind of CAFOs during three flights conducted in November 2019. Enhancements in NH3 and CH4 are distinguishable up to 10 km downwind of CAFOs with the most concentrated portions of the plumes typically below 0.25 km AGL. We demonstrate that NH3 and C2H6 can be jointly used to separate near-source enhancements in CH4 from agriculture and O&NG. Molar enhancement ratios of NH3 to CH4 are quantified for individual CAFOs in this region, and they range from 0.8 to 2.7 ppbv ppbv-1. A multivariate regression model produces enhancement ratios and quantitative regional source contributions that are consistent with prior studies.

A new mobile monitoring approach to characterize community-scale air pollution patterns and identify local high pollution zones

Urban air pollution is quite complex and exhibits significant spatial variability within communities. Traditional centralized monitoring captures temporal variability as well as the long-term trends of air pollution very well, but mapping spatial variability of air pollution in communities at high resolution would require large number of air quality monitors distributed across the community. Mobile monitoring complements stationary monitoring approaches by measuring pollution levels on accessible road networks in urban communities. This paper presents the application of an integrated mobile measurement and data analysis approach to study community-level air pollution patterns, separate the regional background and local contributions, and identify high pollution zones for black carbon (BC), ultrafine particles (UFP), and fine particulate matter (PM2.5). This study was conducted during different periods from 2017 to 2019 in three California cities (Richmond, Stockton, and Commerce) with diverse community and source characteristics.The study found that traffic was the dominant primary source of air pollution in both urban and suburban settings. Urban areas adjacent to large area sources, such as ports and railyards had increased pollutant enhancements due to either direct or indirect emissions, while suburban areas containing unpaved roads were observed to have large PM2.5 enhancement due to the resuspended dust. The analysis disaggregated the contribution of regional and local sources to local air pollution and found that regional background sources contributed up to 75% of the PM2.5 concentrations, while local sources contributed more than half of BC and UFP. The study suggests that 15–30 repeated measurements may be sufficient to map the general air pollution patterns within the community, while some extreme high pollution zones can be identified with fewer repeats (5–10). These techniques can be used for initial screening of air pollution variability within the community, and help identify priority areas for conducting follow-up long-term air quality measurements. The techniques also informs the relative importance of regional and local actions to reduce community pollutant levels.

Impacts of Chemical Initial Conditions in the WRF-CMAQ Model on the Ozone Forecasts in Eastern China

Ozone (O3) has become the major factor for exceeding air pollution standards in many Chinese cities, especially in the more economically developed and densely populated regions, such as eastern China. In this study, we applied the Weather Research and Forecasting/Community Multiscale Air Quality (WRF/CMAQ) model to predict the air quality, and evaluated the influences of different chemical initial conditions on the O3 forecasts with observations in Tai’an and other 13 cities in eastern China in June 2021. The influences of different chemical initial conditions on the O3 forecasts are presented by using two sets of meteorological data (NCEP Final Operational Global Analysis [FNL] and Global Forecast System [GFS]) as initial conditions (IC) and boundary conditions (BC) to drive the WRF/CMAQ model. It was found that the O3 concentrations forecasted by FNL-GFS, in which the chemical IC derived from the CMAQ simulation results by using the FNL data as IC and BC, were closer to observations in all cities than GFS-GFS, in which the chemical IC derived from the CMAQ simulation results by using the GFS data as IC and BC. The normalized mean bias (NMB) values of FNL-GFS for O3 met the benchmark (±15%), while the NMB values of GFS-GFS in Hangzhou and Shijiazhuang did not meet the benchmark. The model performances in Tai’an city were similar to those in 13 cities with better results for FNL-GFS than GFS-GFS. The comparisons of contributions of source regions to O3 in the receptor Tai’an city indicate that different episodes had different relative contributions of source regions and that the simulations of FNL-GFS were more similar to the retrospective simulations than GFS-GFS. The comparisons of contributions of different source sectors to O3 in Tai’an city show that industry emissions are the largest contributor, followed by transportation, power plants and residential emissions.

An estimation method for regional transport contributions from emission sources based on a high-mountain site: a case study in Zhumadian, China

The influence of near surface local emissions on the air quality at a high-mountain measurement site is generally extremely low. A novel approach was developed using observation from a high-mountain background site to quantitatively locate regional source contributions from different transport directions. Source contributions were apportioned by positive matrix factorization (PMF) and the air mass backward trajectories arrived at different times were calculated using the Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT). The source contributions from different transport directions were estimated by coupling backward trajectories in different directions with different source contributions in terms of time. Combined the PMF results with potential source contribution function (PSCF)/concentration weighted trajectory (CWT) methods, the potential influence regions of multiple emission sources from different directions were located. The proposed method was applied to Baiyun Mountain in Zhumadian, China. Results show that the primary directions of regional transport were from the east and southeast by south in summer (Northern Anhui, Southern Henan, and Central and Mid-Northern Hubei Province). Contribution from the southeast by south direction was the largest regional source for secondary sulphate (15.53%) with the primary contributing regions being Western Anhui, Southeastern Henan, and Central Hubei. While in autumn, the main transport directions were from the southeast and northeast, with Mid-Eastern Henan, Southwestern and Southeastern Shandong, and Northern Anhui Province being the major contributing regions. Transport contributions for secondary nitrate and coal combustion were dominated from southeaster (24.34%) and northeaster (22.17%), where the potential contribution regions were located in Mid-Eastern Henan, Southwest Shandong, and Northern Anhui Province.

Origin of regional springtime ozone episodes in the Sichuan Basin, China: Role of synoptic forcing and regional transport.

The Sichuan Basin (SCB) located in southwestern China has long been considered the most polluted city cluster with exposure to unhealthy levels of ozone (O3) at times. However, the features of O3 regional transport and source contributions in SCB are poorly understood. In this study, ambient measurements, ERA5 reanalysis dataset, IASI O3 column, and the Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) modeling system coupled with the Integrated Source Apportionment Method (ISAM) module were used to investigate the formation mechanism and sources of a severe O3 episode in spring 2020 over the SCB. In the first stage of the O3 episode, a high-pressure system persisted over the western SCB and caused northeasterly wind fields, leading to enhanced regional transport from the northern boundary with the O3 contribution from the boundary exceeding 50% across the SCB. As the synoptic pattern evolved, southeasterly winds dominated the SCB and the stagnant zone over the Chengdu Plain confined O3 originating from the southern SCB and Chongqing city, leading to the accumulation of precursors and elevated O3 levels. During the O3 episode, transportation and industrial sources were major contributors to O3 formation especially for the Chengdu Plain and Chongqing city. In addition, the O3-rich air mass in the nocturnal residual layer that formed over Chongqing city was transported to the Chengdu Plain through southeastern corridor at 400-1600m above ground-level under the prevailing southeasterly winds. With sunrise and the development of the atmospheric boundary layer, the O3-rich air mass in the residual layer (RL) was entrained to the ground-level via vertical mixing, which further enhanced O3 pollution across the Chengdu Plain. Our results revealed the mechanism of regional transport via northeastern and southeastern corridors during an O3 episode and demonstrated the need for joint emission regulation across the SCB to mitigate O3 pollution.

Assessing Multiple Pollutants’ Impacts on Multiple Health Outcomes in New York City

Background: Although air pollution is a mixture that includes local and regional emissions sources, local governments currently rely on single-pollutant-based U.S. national ambient air quality standards (NAAQS) to protect health. We developed a framework to assess multi-pollutants’ impacts on health outcomes in New York City (NYC) using time-series analyses. Methods: Single- and multi-pollutant Poisson models for ozone, nitrogen dioxide (NO2), and fine particles (PM2.5) were evaluated for multiple outcomes (morbidity models: 2005-2014; mortality models: 2004-2016): (1) asthma-related emergency department visits (ages 6-18); (2) cardiovascular-related hospitalizations (ages 40+); (3) hospitalizations for chronic lung diseases (ages 20+); and (4) cardiovascular (CVD) and all-natural-cause mortality (all ages). Seasonal models were adjusted for within-season trend, temperature, and day-of-week, and considered up to 3-day lagged effects. Attributable fractions (AFs) were estimated considering single and multiple pollutants when associations were found. Results: All outcomes were associated with one or more pollutants at levels below their current NAAQS. Individual pollutants’ estimates were sometimes sensitive (e.g., attenuation of risk estimates by 50%) to the addition of another pollutant, and total AFs in multi-pollutant models were typically smaller than the sum of those from single pollutant models. For hospitalization outcomes, AFs from NO2-only models were generally closest to those from corresponding multi-pollutant models (e.g., cold-season NO2-only models for lung diseases and CVD AFs (95% CI): 2.2% (-0.6, 5.0) and 3.3% (1.0, 5.6); NO2 + PM2.5: 2.2% (-1.9, 6.3) and 3.2% (-0.1, 6.5). Mortality outcomes were associated with all three pollutants in the warm season, with ozone-only models most indicative of multi-pollutant effects (e.g. all-cause mortality AFs: ozone only: 1.6% (0.1, 3.7); ozone + PM2.5 + NO2: 1.8% (-1.1, 5.1)).Conclusions: Given the substantial regional source contributions to PM2.5 and ozone, reducing local NO2 emissions (i.e., traffic and buildings) may be most impactful in reducing pollution-associated illness exacerbations in NYC.

Assessing the contribution of regional sources to urban air pollution by applying 3D-PSCF modeling

A three dimensional (3D) variant of the Potential Source Contribution Function (PSCF) model was used in this study, aiming to identify the source areas and altitudinal atmospheric layers associated with PM10 exceedances of the daily EU limit value (>50 μg/m3) during the different seasons in Athens (Greece). The analysis covers the period 1 May 2015 to 31 December 2018, during which direct Saharan dust intrusions from North Africa and especially Libya and Egypt, occurred mainly within the 0-1000 m a.g.l. layer, and were identified as a significant source of PM10 exceedances during all seasons. The maximum probability of dust events was detected in spring, when the dust transport pathways were also vertically extended. Additionally, an increased probability of PM10 exceedances in winter was linked to northerly airflows within both the 0-1000 m a.g.l. and 1000-2000 m a.g.l. layers, indicating regional transport from the Balkans and Northern Greece. To delineate the emission origin of winter PM10 exceedances, the 3D-PSCF model was also applied on concentrations of Black Carbon (BC), its wood burning related fraction (BCwb) and CO, recognized as markers of incomplete combustion processes. A synoptic analysis showed that the accumulation of local emissions due to stagnant anticyclonic conditions is the primary cause of the PM10, CO, BC and BCwb episodes in Athens during winter, however 3D-PSCF model also clearly demonstrated supplementary contributions from regional combustion sources located in the Balkans and Northern Greece.

High PM10 concentrations in the city of Buenos Aires and their relationship with meteorological conditions

Abstract In this work, the first long-term (eight years) record of hourly concentrations of carbon monoxide (CO), nitrogen dioxide (NO2) and particulate matter with diameter less than 10 μm (PM10) from three sites in the city of Buenos Aires is analysed. Considering the short-term guidelines suggested by the WHO, the daily mean PM10 concentrations present a relatively large number of exceedances at the three sites. Different statistical techniques are combined to study the relationship between these relatively high PM10 concentrations and relevant surface meteorological variables. For all pollutants and sites, wind speed shows the largest differences between the lowest and highest concentration quartiles. To further explore its role on daily mean PM10 concentration, a k-means algorithm is applied, grouping days with similar surface 1h-wind sequences. Five wind sequence clusters are found, presenting distinctive air quality data features. Two clusters (1 and 2) show that PM10 exceedances occurring with winds entering the city from the river represent between 10 and 21% of total events at the three sites. The frequency of exceedance under these conditions decreases with the distance to the coast. For cluster 1, the hourly PM10 concentration profile and its associated daily wind sequence suggest an important contribution to exceedance events from the city's southernmost power plant. Two clusters (3 and 4), exhibiting continental winds, account for 49–59% of the exceedances and co-occur with relatively drier air conditions. The correlation between CO and PM10 for days belonging to cluster 3 supports the hypothesis of a potential remote or distributed source contribution with SW winds. For cluster 4, differences among sites in the number of events under NNW winds suggest an important contribution from the city's widest avenue to the PM10 levels at the most coastal site. A large contribution coming from urban sources is also indicated for these winds. Finally, cluster 5, exhibiting low wind speed sequences, accounts for 23–33% of the exceedances at the three sites. The average PM10 concentration increases with persistence of this cluster, which could be a driver for exceedances. These results contribute to show the importance of simple methods such as clustering analysis to obtain insights into air quality features such as exceedances and their potential drivers. They also suggest that further efforts in monitoring, modelling and emission estimates may help to better understand local, urban and regional source contributions to these events in the city of Buenos Aires.

Estimating the air quality and health impacts of biomass burning in northern South America using a chemical transport model

Biomass burning (BB) emissions significantly deteriorate air quality in many regions worldwide, impact human health and perturbing Earth's radiation budget and climate. South America is one of largest contributors to BB emissions globally. After Amazonia, BB emissions from open and agricultural fires of Northern South America (NSA) are the most significant. Recent evidence shows a strong correlation between fire counts in NSA and Brown Carbon in some Colombian cities, suggesting a substantial seasonal contribution of regional BB sources to air pollution levels in the densely populated areas of NSA. In this work we use the atmospheric regional chemical transport model WRF-Chem to assess the contribution of open BB events to pollutant concentration and to estimate potential health impacts associated with wildfire events in NSA. Three nested domains are used to simulate atmospheric composition in the Northern part of South America and the Caribbean. Simulations included biogenic and anthropogenic emissions from a global emission inventory merged with local emissions for the city of Bogotá. Two modelling scenarios were considered, a base case without BB emissions (NO_FIRE) and a sensitivity scenario with BB emissions. Simulations were carried out for periods of strong BB activity in NSA. In the NO_FIRE scenario, aerosol concentrations are unrealistically low. When BB emissions are is included background PM2.5 concentrations increase 80%. The increment in aerosol concentrations is mainly driven by Secondary Organic Aerosols. In the case of Bogotá, the most densely populated city in the domain, monthly mean increase in PM2.5 is 3.3 μg m−3 and 4.3 ppb for O3. Modeled meteorological and air pollution fields are in better agreement with observations when high spatial resolution (3 × 3 km) is used in the simulations. The total estimated short-term all-cause mortality associated to BB during February in the region is 171 cases, 88 PM2.5-related and 83 O3-related mortality.

Air quality monitoring using mobile low-cost sensors mounted on trash-trucks: Methods development and lessons learned

Air quality monitoring (AQM) is crucial for cities to develop management plans supporting population health. However, there is a dearth of measurements due to the high cost of standard reference instruments. Mobile AQM using low-cost sensors deployed on routine fleets of vehicles can enable the continuous detection of fine-scale pollutant variations in cities at a lower cost. New methods need to be developed to interpret these measurements. This paper presents three such methods. First, we propose a technique to identify aerosol hotspots. Second, we employ techniques published previously to assess the generalizable map of fine and coarse particle number concentrations, to understand qualitatively the contribution of local and regional sources across the region sampled. By using the raw number concentration of differently sized particles from the Optical Particle Counters (OPCs) instead of the noisier mass concentrations, we obtain more robust results. Third, in order to evaluate source signatures in cities, we propose another technique, in which we cluster the entire range of aerosol size-distribution measurements acquired. The properties of each cluster provide insight into the aerosol source characteristics in the sampling environment. We test these methods using a dataset we collected by mounting OPCs on two trash-trucks in Cambridge, Massachusetts.

Transport Pathways and Potential Source Region Contributions of PM2.5 in Weifang: Seasonal Variations

As air pollution becomes progressively more serious, accurate identification of urban air pollution characteristics and associated pollutant transport mechanisms helps to effectively control and alleviate air pollution. This paper investigates the pollution characteristics, transport pathways, and potential sources of PM2.5 in Weifang based on PM2.5 monitoring data from 2015 to 2016 using three methods: Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), the potential source contribution function (PSCF), and concentration weighted trajectory (CWT). The results show the following: (1) Air pollution in Weifang was severe from 2015 to 2016, and the annual average PM2.5 concentration was more than twice the national air quality second-level standard (35 μg/m3). (2) Seasonal transport pathways of PM2.5 vary significantly: in winter, spring and autumn, airflow from the northwest and north directions accounts for a large proportion; in contrast, in summer, warm-humid airflows from the ocean in the southeastern direction dominate with scattered characteristics. (3) The PSCF and CWT results share generally similar characteristics in the seasonal distributions of source areas, which demonstrate the credibility and accuracy of the analysis results. (4) More attention should be paid to short-distance transport from the surrounding areas of Weifang, and a joint pollution prevention and control mechanism is critical for controlling regional pollution.

Regional source apportionment of summertime ozone and its precursors in the megacities of Beijing and Shanghai using a source-oriented chemical transport model

The Community Multiscale Air Quality (CMAQ) model with a source-oriented SAPRC-11 photochemical mechanism is developed in this study to quantify the source region contributions to surface O3 in Beijing and Shanghai in August 2013. Non-background O3 attributed to NOx (O3_NOx) and volatile organic compounds (O3_VOC) emitted from different source regions is determined using a three-regime approach that correctly attributes O3 to NOx and VOC precursors throughout the entire range of NOx-VOC-O3 formation sensitivity. Averaged over the entire month and all grid cells, local emissions (51%) and emissions from Hebei (31%) are the two major contributors to non-background daily maximum 8-h (DM8H) O3 in Beijing. In Shanghai, local, Zhejiang and Jiangsu emissions account for 53%, 19% and 14% of the non-background DM8H O3. Significant variations in local emission contributions are predicted among different model grid cells for both cities (Beijing, 6–80%; Shanghai, 3–76%). On high O3 days in Beijing, the wind is persistently from the south with high wind speed (~5 m s−1) in the evening and night. This leads to significant regional contributions of O3 from Hebei, along with regional transport of VOCs and NOx. In Shanghai, high O3 days are associated with southwesterly/westerly wind in the morning, rotating to southeast in the early afternoon in a counter-clockwise direction. The surface wind then gradually turns back to southwest in the afternoon until the next morning, along with reduced wind speed. In Shanghai, daytime O3 at the urban center is almost entirely due to local emissions. Low wind speed in the evening and night time allows local NOx emissions to efficiently titrate regional O3. In both cities, NOx emissions are not transported regionally as efficiently as VOCs. Source region contribution analysis of the concentration weighted maximum incremental reactivity (CWMIR) shows that VOCs from other regions are less reactive than locally emitted VOCs. HCHO and acetaldehyde (CCHO) generated from the oxidation of other VOCs are important contributors to regionally transported reactive VOCs. In both regions, the overall CWMIR in both cities is quite similar (~4 mol O3 per mole of VOC).

Regional sources of airborne ultrafine particle number and mass concentrations in California

Abstract. Regional concentrations and source contributions are calculated for airborne particle number concentration (Nx) and ultrafine particle mass concentration (PM0.1) in the San Francisco Bay Area (SFBA) and the South Coast Air Basin (SoCAB) surrounding Los Angeles with 4 km spatial resolution and daily time resolution for selected months in the years 2012, 2015, and 2016. Performance statistics for daily predictions of N10 concentrations meet the goals typically used for modeling of PM2.5 (mean fractional bias (MFB) < ±0.5 and mean fractional error (MFE) < 0.75). The relative ranking and concentration range of source contributions to PM0.1 predicted by regional calculations agree with results from receptor-based studies that use molecular markers for source apportionment at four locations in California. Different sources dominated regional concentrations of N10 and PM0.1 because of the different emitted particle size distributions and different choices for heating fuels. Nucleation (24 %–57 %) made the largest single contribution to N10 concentrations at the 10 regional monitoring locations, followed by natural gas combustion (28 %–45 %), aircraft (2 %–10 %), mobile sources (1 %–5 %), food cooking (1 %–2 %), and wood smoke (0 %–1 %). In contrast, natural gas combustion (22 %–52 %) was the largest source of PM0.1 followed by mobile sources (15 %–42 %), food cooking (4 %–14 %), wood combustion (1 %–12 %), and aircraft (2 %–6 %). The study region encompassed in this project is home to more than 25 million residents, which should provide sufficient power for future epidemiological studies on the health effects of airborne ultrafine particles. All of the PM0.1 and N10 outdoor exposure fields produced in the current study are available free of charge at http://webwolf.engr.ucdavis.edu/data/soa_v3/hourly_avg/ (last access: 20 November 2019).