Increases in PM2.5 levels in Houston are associated with a highly recirculating sea breeze

Local land-sea breezes play an important role in coastal air quality because they circulate air between coastal/urban and marine areas, potentially causing the accumulation of pollutants. This has been observed for the secondary photochemical pollutant ozone. However, particulate matter (PM) also warrants investigation. To understand the complicated interactions between coastal urban air quality and a local land-sea breeze, we analyzed historical monitoring data from Houston, Texas, which is the fourth most populous city in the United States. Using k-means clustering algorithms to analyze wind data from Houston, we successfully identified a sea breeze recirculation cluster. Additionally, we performed positive matrix factorization on PM2.5 (2.5 μm in diameter or smaller) composition data for 2010-2018 from Houston Deer Park #2 monitoring site, 5 km south of the industrialized Houston Ship Channel. The resulting eight factors indicated a variety of anthropogenic, natural, primary and secondary sources. Emphasizing the PM2.5 sources in each of the wind clusters for June, July, and August, we discovered that on southernly wind and sea breeze recirculation days, the PM2.5 concentrations are ∼30% higher than those under other wind patterns. Under southerly wind, 53% of PM2.5 was attributed to long-range transport of soil and 15% to aged and fresh sea salt. In contrast, on days identified as being impacted by a sea breeze, 60% of PM2.5 was attributed to anthropogenic emissions and only 15% to soil sources. Secondary organic aerosol from multiple sources also appeared to be important on sea breeze days.

Marine Submicron Aerosols from the Gulf of Mexico: Polluted and Acidic with Rapid Production of Sulfate and Organosulfates

We measured submicron aerosols (PM₁) at a beachfront site in Texas in Spring 2021 to characterize the "background" aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine "background" aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM₁ mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf "background" aerosols were much more polluted; the average non-refractory (NR-) PM₁ mass concentration was 3-70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured "background" sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

Sources, Occurrence and Characteristics of Fluorescent Biological Aerosol Particles Measured Over the Pristine Southern Ocean

In this study, we investigate the occurrence of primary biological aerosol particles (PBAP) over all sectors of the Southern Ocean (SO) based on a 90-day data set collected during the Antarctic Circumnavigation Expedition (ACE) in austral summer 2016-2017. Super-micrometer PBAP (1-16 µm diameter) were measured by a wide band integrated bioaerosol sensor (WIBS-4). Low (3σ) and high (9σ) fluorescence thresholds are used to obtain statistics on fluorescent and hyper-fluorescent PBAP, respectively. Our focus is on data obtained over the pristine ocean, that is, more than 200 km away from land. The results indicate that (hyper-)fluorescent PBAP are correlated to atmospheric variables associated with sea spray aerosol (SSA) particles (wind speed, total super-micrometer aerosol number concentration, chloride and sodium concentrations). This suggests that a main source of PBAP over the SO is SSA. The median percentage contribution of fluorescent and hyper-fluorescent PBAP to super-micrometer SSA was 1.6% and 0.13%, respectively. We demonstrate that the fraction of (hyper-)fluorescent PBAP to total super-micrometer particles positively correlates with concentrations of bacteria and several taxa of pythoplankton measured in seawater, indicating that marine biota concentrations modulate the PBAP source flux. We investigate the fluorescent properties of (hyper-)fluorescent PBAP for several events that occurred near land masses. We find that the fluorescence signal characteristics of particles near land is much more variable than over the pristine ocean. We conclude that the source and concentration of fluorescent PBAP over the open ocean is similar across all sampled sectors of the SO.

Overview of surface measurements and spatial characterization of submicrometer particulate matter during the DISCOVER-AQ 2013 campaign in Houston, TX

The sources of submicrometer particulate matter (PM₁) remain poorly characterized in the industrialized city of Houston, TX. A mobile sampling approach was used to characterize PM₁ composition and concentration across Houston based on high-time-resolution measurements of nonrefractory PM₁ and trace gases during the DISCOVER-AQ Texas 2013 campaign. Two pollution zones with marked differences in PM₁ levels, character, and dynamics were established based on cluster analysis of organic aerosol mass loadings sampled at 16 sites. The highest PM₁ mass concentrations (average 11.6 ± 5.7 µg/m³) were observed to the northwest of Houston (zone 1), dominated by secondary organic aerosol (SOA) mass likely driven by nighttime biogenic organonitrate formation. Zone 2, an industrial/urban area south/east of Houston, exhibited lower concentrations of PM₁ (average 4.4 ± 3.3 µg/m³), significant organic aerosol (OA) aging, and evidence of primary sulfate emissions. Diurnal patterns and backward-trajectory analyses enable the classification of airmass clusters characterized by distinct PM sources: biogenic SOA, photochemical aged SOA, and primary sulfate emissions from the Houston Ship Channel. Principal component analysis (PCA) indicates that secondary biogenic organonitrates primarily related with monoterpenes are predominant in zone 1 (accounting for 34% of the variability in the data set). The relevance of photochemical processes and industrial and traffic emission sources in zone 2 also is highlighted by PCA, which identifies three factors related with these processes/sources (~50% of the aerosol/trace gas concentration variability). PCA reveals a relatively minor contribution of isoprene to SOA formation in zone 1 and the absence of isoprene-derived aerosol in zone 2. The relevance of industrial amine emissions and the likely contribution of chloride-displaced sea salt aerosol to the observed variability in pollution levels in zone 2 also are captured by PCA.

IMPLICATIONS

This article describes an urban-scale mobile study to characterize spatial variations in submicrometer particulate matter (PM₁) in greater Houston. The data set indicates substantial spatial variations in PM₁ sources/chemistry and elucidates the importance of photochemistry and nighttime oxidant chemistry in producing secondary PM₁. These results emphasize the potential benefits of effective control strategies throughout the region, not only to reduce primary emissions of PM₁ from automobiles and industry but also to reduce the emissions of important secondary PM₁ precursors, including sulfur oxides, nitrogen oxides, ammonia, and volatile organic compounds. Such efforts also could aid in efforts to reduce mixing ratios of ozone.

More surprises in the global greenhouse: Human health impacts from recent toxic marine aerosol formations, due to centennial alterations of world-wide coastal food webs

Reductions of zooplankton biomasses and grazing pressures were observed during overfishing-induced trophic cascades and concurrent oil spills at global scales. Recent phytoplankton increments followed, once Fe-, P-, and N-nutrient limitations of commensal diazotrophs and dinoflagellates were also eliminated by respective human desertification, deforestation, and eutrophication during climate changes. Si-limitation of diatoms instead ensued during these last anthropogenic perturbations of agricultural effluents and sewage loadings. Consequently, ~15% of total world-wide annual asthma trigger responses, i.e. amounting to ~45 million adjacent humans during 2004, resulted from brevetoxin and palytoxin poisons in aerosol forms of western boundary current origins. They were denoted by greater global harmful algal bloom [HAB] abundances and breathing attacks among sea-side children during prior decadal surveys of asthma prevalence, compiled here in ten paired shelf ecosystems of western and eutrophied boundary currents. Since 1965, such inferred onshore fluxes of aerosolized DOC poisons of HABs may have served as additional wind-borne organic carriers of toxic marine MeHg, phthalate, and DDT/DDE vectors, traced by radio-iodine isotopes to potentially elicit carcinomas. During these exchanges, as much as 40% of mercury poisonings may instead have been effected by inhalation of collateral HAB-carried marine neurotoxic aerosols of MeHg, not just from eating marine fish. Health impacts in some areas were additional asthma and pneumonia episodes, as well as endocrine disruptions among the same adjacent humans, with known large local rates of thyroid cancers, physician-diagnosed pulmonary problems, and ubiquitous high indices of mercury in hair, pesticides in breast milk, and phthalates in urine.

Assessment of the long-term impacts of PM10 and PM2.5 particles from construction works on surrounding areas

Construction activities are common across cities; however, the studies assessing their contribution to airborne PM10 (≤10 μm) and PM2.5 (≤2.5 μm) particles on the surrounding air quality are limited. Herein, we assessed the impact of PM10 and PM2.5 arising from construction works in and around London. Measurements were carried out at 17 different monitoring stations around three construction sites between January 2002 and December 2013. Tapered element oscillating microbalance (TEOM 1400) and OSIRIS (2315) particle monitors were used to measure the PM10 and PM2.5 fractions in the 0.1-10 μm size range along with the ambient meteorological data. The data was analysed using bivariate concentration polar plots and k-means clustering techniques. Daily mean concentrations of PM10 were found to exceed the European Union target limit value of 50 μg m(-3) at 11 monitoring stations but remained within the allowable 35 exceedences per year, except at two monitoring stations. In general, construction works were found to influence the downwind concentrations of PM10 relatively more than PM2.5. Splitting of the data between working (0800-1800 h; local time) and non-working (1800-0800 h) periods showed about 2.2-fold higher concentrations of PM10 during working hours when compared with non-working hours. However, these observations did not allow to conclude that this increase was from the construction site emissions. Together, the polar concentration plots and the k-means cluster analysis applied to a pair of monitoring stations across the construction sites (i.e. one in upwind and the other in downwind) confirmed the contribution of construction sources on the measured concentrations. Furthermore, pairing the monitoring stations downwind of the construction sites showed a logarithmic decrease (with R(2) about 0.9) in the PM10 and PM2.5 concentration with distance. Our findings clearly indicate an impact of construction activities on the nearby downwind areas and a need for developing mitigation measures to limit their escape from the construction sites.

Fine particulate matter components and mortality in Greater Houston: Did the risk reduce from 2000 to 2011?

Fine particulate matter (less than 2.5μm in aerodynamic diameter; PM2.5) pollution poses a major environmental threat in Greater Houston due to rapid economic growth and the numerous PM2.5 sources including ports, vehicles, and the largest petrochemical industry in the United States (U.S.). Our objectives were to estimate the short-term associations between the PM2.5 components and mortality during 2000-2011, and evaluate whether these associations have changed over time. A total of 333,317 deaths were included in our assessment, with an average of 76 deaths per day. We selected 17 PM2.5 components from the U.S. Environmental Protection Agency's Chemical Speciation Network, and then applied Poisson regression models to assess the associations between the PM2.5 components and mortality. Additionally, we repeated our analysis for two consecutive periods: 2000-2005 and 2006-2011. Interquartile range increases in ammonium (0.881μg/m(3)), nitrate (0.487μg/m(3)), sulfate (2.245μg/m(3)), and vanadium (0.004μg/m(3)) were associated with an increased risk in mortality of 0.69% (95% confidence interval (CI): 0.26, 1.12%), 0.38% (95% CI: 0.11, 0.66%), 0.61% (95% CI: 0.15, 1.06%), and 0.58% (95% CI: 0.12, 1.04%), respectively. Seasonal analysis suggested that the associations were strongest during the winter months. The association between PM2.5 mass and mortality decreased during 2000-2011, however, the PM2.5 components showed no notable changes in mortality risk over time. Our study indicates that the short-term associations between PM2.5 and mortality differ across the PM2.5 components and suggests that future air pollution control measures should not only focus on mass but also pollutant sources.

Urban impacts on regional carbonaceous aerosols: case study in central Texas

Rural and background sites provide valuable information on the concentration and optical properties of organic, elemental, and water-soluble organic carbon (OC, EC, and WSOC), which are relevant for understanding the climate forcing potential of regional atmospheric aerosols. To quantify climate- and air quality-relevant characteristics of carbonaceous aerosol in the central United States, a regional background site in central Texas was chosen for long-term measurement. Back trajectory (BT) analysis, ambient OC, EC, and WSOC concentrations and absorption parameters are reported for the first 15 months of a long-term campaign (May 2011-August 2012). BT analysis indicates consistent north-south airflow connecting central Texas to the Central Plains. Central Texas aerosols exhibited seasonal trends with increased fine particulate matter (< 2.5 microm aerodynamic diameter, PM2.5) and OC during the summer (PM2.5 = 10.9 microg m(-3) and OC = 3.0 microg m(-3)) and elevated EC during the winter (0.22 microg m(-3)). When compared to measurements in Dallas and Houston, TX, central Texas OC appears to have mixed urban and rural sources. However central Texas EC appears to be dominated by transport of urban emissions. WSOC averaged 63% of the annual OC, with little seasonal variability in this ratio. To monitor brown carbon (BrC), absorption was measured for the aqueous WSOC extracts. Light absorption coefficients for EC and BrC were highest during summer (EC MAC = 11 m2 g(-1) and BRC MAE365 = 0.15 m2 g(-1)). Results from optical analysis indicate that regional aerosol absorption is mostly due to EC with summertime peaks in BrC attenuation. This study represents the first reported values of WSOC absorption, MAE365, for the central United States. Implications: Background concentration and absorption measurements are essential in determining regional potential radiative forcing due to atmospheric aerosols. Back trajectory, chemical, and optical analysis of PM2.5 was used to determine climatic and air quality implications of urban outflow to a regional receptor site, representative of the central United States. Results indicate that central Texas organic carbon has mixed urban and rural sources, while elemental carbon is controlled by the transport of urban emissions. Analysis of aerosol absorption showed black carbon as the dominant absorber, with less brown carbon absorption than regional studies in California and the southeastern United States.

Field study and source attribution for PM2.5 and PM10 with resulting reduction in concentrations in the neighborhood north of the Houston Ship Channel based on voluntary efforts

When annual average PM2.5 (fine particulate matter sized 2.5 microns and less) data for 2005 became available in April 2006 and the 3-yr average PM2.5 concentration in an area just north of the Houston Ship Channel reached 15.0 microg/m3, the Texas Commission on Environmental Quality (TCEQ) initiated daily collection of quartz fiber as well as Teflon PM2.5 filter samples for chemical speciation analysis. The purpose of the chemical speciation analysis was to use the speciation data, together with meteorological data and hourly TEOM (tapered element oscillating microbalance) PM2.5 mass data, to identify the causes of the high PM2.5 concentrations affecting the monitoring site and the neighborhood. The ultimate purpose was to target emission reduction efforts to sources contributing to the high measured PM2.5 concentrations. After a year of data collection, it was recognized that a specific source, unpaved driveways and loading areas along the Ship Channel and dirt tracked onto Clinton Drive, the main artery running east-west north of the Ship Channel, were the primary cause for the Clinton Drive site's measuring PM2.5 concentrations significantly higher than other sites in Houston. The source characterization and remediation steps that have led to sustained reduced concentrations are described in this paper.

Mass spectrometry of atmospheric aerosols--recent developments and applications. Part II: On-line mass spectrometry techniques

Many of the significant advances in our understanding of atmospheric particles can be attributed to the application of mass spectrometry. Mass spectrometry provides high sensitivity with fast response time to probe chemically complex particles. This review focuses on recent developments and applications in the field of mass spectrometry of atmospheric aerosols. In Part II of this two-part review, we concentrate on real-time mass spectrometry techniques, which provide high time resolution for insight into brief events and diurnal changes while eliminating the potential artifacts acquired during long-term filter sampling. In particular, real-time mass spectrometry has been shown recently to provide the ability to probe the chemical composition of ambient individual particles <30 nm in diameter to further our understanding of how particles are formed through nucleation in the atmosphere. Further, transportable real-time mass spectrometry techniques are now used frequently on ground-, ship-, and aircraft-based studies around the globe to further our understanding of the spatial distribution of atmospheric aerosols. In addition, coupling aerosol mass spectrometry techniques with other measurements in series has allowed the in situ determination of chemically resolved particle effective density, refractive index, volatility, and cloud activation properties.