Characteristics and source identification study of ambient suspended particulates and ionic pollutants in an area abutting a highway

Ambient suspended particulates in an area abutting a highway were gathered using a Partisol Model 2300 Speciaton Sampler (RP2300). Major ionic species with different particle sizes and with possible sources close to the sampling site were evaluated using Principal Component Analysis (PCA). Observational results indicate that average PM_2.5 and PM₁₀ concentrations were 66.33 and 108.28 μg/m³, respectively. The average ratio of PM_2.5/PM₁₀ was 62% at this sampling site, whereas the average PM_2.5/PM₁₀ ratio in this study was less than those in urban (Seoul, Korea), suburban (Basel, Switzerland) and rural (Chaumont, Switzerland) settings. Average concentrations for ionic species of NO₃⁻, SO₄²⁻ and NH₄⁺ were 10.46, 12.63 and 7.87 μg/m³ in PM_2.5, respectively. Average concentrations for ionic species of NO₃⁻, SO₄²⁻ and NH₄⁺ were 17.28, 15.59 and 9.48 μg/m³ in PM₁₀, respectively. Principal component analysis identified soil, secondary aerosols and marine salt as possible major pollutant sources at this sampling site.     

Automated Low-Pressure Carbonate Eluent Ion Chromatography System with Postsuppressor Carbon Dioxide Removal for the Analysis of Atmospheric Gases and Particles

We present a low-pressure, automated, semi-continuous Gas-Particle Ion Chromatograph to measure soluble ionogenic gases and soluble ionic constituents of PM_2.5. The system utilizes a short separation column, an isocratic carbonate eluent and post suppressor CO₂ removal. Measured constituents include ammonium, nitrate, and sulfate in the particle fraction, and nitric acid, sulfur dioxide, and ammonia among soluble gases. Two independent sampling channels are used. In one channel, a wet denuder collects soluble gases. In the second channel, following removal of large particles by a cyclone and soluble gases by a wet denuder, a hydrophobic filter-based particle collector collects and extracts the soluble components of PM_2.5. The aqueous particle extract is aspirated by a peristaltic pump onto serial cation and anion preconcentrator columns. Gas samples are similarly loaded onto another set of serial cation and anion preconcentrator columns. The cation preconcentrator is eluted with NaOH and the evolved NH₃ is passed across a membrane device whence it diffuses substantially into a deionized water receptor stream; the conductivity of the latter provides a measure of NH₃ (NH₄ ⁺). The anion preconcentrator column(s) are subjected to automated periodic analysis by ion chromatography. This system provides data every 30 min for both particles (NO₃ ^?, SO₄ ^{2 ?} and NH₄ ⁺) and gases (HNO₃, SO₂ and NH₃). Gas and particle extract samples are each collected for 15 min. The analyses of the gas and particle samples are staggered 15 min apart. The limit of detection (S/N = 3) for NO₃ ^?, SO₄ ^2? and NH₄ ⁺ are 2.6, 5.3, and 2.1 ng/m³, respectively.     

Scavenging Ratios in an Urban Area in the Spanish Basque Country

For a period of six years (1995–2000) the scavenging ratio, which is the ratio of a pollutant's concentration in water to its concentration in air, collected at an urban site in the Spanish Basque Country was studied. The aerosol is characterized by SO₄ ^2? and NO₃? with 1.79 and 1.61 μg m^?3, respectively. Greater fractions of SO₄ ^2?, NO₃?, and NH₄+ ions were present in the fine particle range, while greater fractions of other ions appeared in the coarse range. The most important species found in the precipitation is SO₄ ^2? with 3.0 mg l^?1. NO₃?, Ca²⁺, and Cl^? are the second most important ions. The volume-weighted mean concentration of H⁺ is 4.6 μg l^?1 (pH = 5.3). The concentration of all analyzed ions (except H⁺) decreases throughout the rain event, showing the washout phenomenon of the rainwater. The scavenging ratio for the anthropogenic ions NO₃?, SO₄ ^2?, NH₄+, and K⁺ is lower than the scavenging ratio for the marine-terrigenous ions, Cl^?, Na⁺, and Ca²⁺.     

Humidity,density, and inlet aspiration efficiency correction improve accuracy of a low-cost sensor during field calibration at a suburban site in the North-Western Indo-Gangetic plain (NW-IGP)

Abstract

Low-cost particulate matter (PM) sensors are now widely used by concerned citizens to monitor PM exposure despite poor validation under field conditions. Here, we report the field calibration of a modified version of the Laser Egg (LE), against Class III US EPA Federal Equivalent Method PM₁₀ and PM_2.5 β-attenuation analyzers. The calibration was performed at a site in the north-western Indo-Gangetic Plain from 27 April 2016 to 25 July 2016. At ambient PM mass loadings ranging from <1–838?µg m^?3 and <1–228?µg m^?3 for PM₁₀ and PM_2.5, respectively, measurements of PM₁₀, PM_2.5 from the LE were precise, with a Pearson correlation coefficient (r) >0.9 and a percentage coefficient of variance (CV) <12%. The original Mean Bias Error (MBE) of ～?90?µg m^?3 decreased to ?30.9?µg m^?3 (Sensor 1) and ?23.2?µg m^?3 (Sensor 2) during the summer period (27 April–15 June 2016) after correcting for particle density and aspiration losses. During the monsoon period (16 June–25 July 2016) the MBE of the PM_2.5 measurements decreased from 19.1?µg m^?3 to 8.7?µg m^?3 and from 28.3?µg m^?3 to 16.5?µg m^?3 for Sensor 1 and Sensor 2, respectively, after correcting for particle density and hygroscopic growth. The corrections reduced the overall MBE to <20?µg m^?3 for PM₁₀ and <3?µg m^?3 for PM_2.5, indicating that modified version of the LE could be used for ambient PM monitoring with appropriate correction and meteorological observations. However, users of the original product may underestimate their PM₁₀ exposure.

Copyright © 2020 American Association for Aerosol Research     

Reconstructing Primary and Secondary Components of PM2.5 Composition for an Urban Atmosphere

Total 360 samples (of 8 h each) of PM_2.5 were collected from six sampling sites for summer and winter seasons in Kanpur city, India. The collected PM_2.5 mass was subjected to chemical speciation for: (1) ionic species (NH⁺ ₄, SO^2– ₄, NO^– ₃, and Cl^–), (2) carbon contents (EC and OC), and (3) elemental contents (Ca, Mg, Na, K, Al, Si, Fe, Ti, Mn, V, Cr, Ni, Zn, Cd, Pb, Cu, As, and Se). Primary and secondary components of PM_2.5 were assessed from speciation results. The influence of marine source to PM_2.5 was negligible, whereas the contribution of crustal dust was significant (10% in summer and 7% in winter). A mass reconstruction approach for PM_2.5 could distinctly establish primary and secondary components of measured PM_2.5 as: (1) Primary component (27% in summer and 24% in winter): crustal, elemental carbon, and organic mass, (2) Secondary component (45% in summer and 50% in winter): inorganic and organic mass, and (3) others: unidentified mass (27% in summer and 26% in winter). The secondary inorganic component was about 34% in summer (NH⁺ ₄: 9%; SO^2– ₄: 16%; NO^– ₃: 9%) and 32% in winter (NH⁺ ₄: 8%; SO²⁺ ₄: 13%; NO^– ₃: 11%). The secondary organic component was 12% in summer and 18% in winter. In conclusion, secondary aerosol formation (inorganic and organic) accounted for significant mass of PM _2.5 (about 50%) and any particulate control strategy should also include control of primary precursor gases.     

Seasonal Variation of Airborne Particle Deposition Efficiency in the Human Respiratory System

Particulate matter (PM) is associated with human health effects but the apparent toxicity of PM in epidemiological studies varies with season. PM toxicity may change due to seasonal shifts in composition or particle size distributions that in turn affect respiratory deposition efficiencies. In the current study, size-resolved PM composition was measured in the largest city (Fresno) in California's heavily polluted San Joaquin Valley during the summer (30 days) and winter (20 days) between 2006 and 2009 for 21 metals, organic carbon, elemental carbon, and 7 water-soluble ions. The Multiple-Path Particle Dosimetry model was applied to determine if seasonal variation in size-resolved composition influences respiratory deposition patterns. Mg, Al, S, V, Mn, Fe, Ni, Ba, SO₄ ^2-, Na⁺, and Ca²⁺ had larger total deposition efficiencies (p < 0.004) during the summer versus the winter in all three regions of the respiratory tract. This trend results from increased relative concentrations of the target analytes per μg m^?3 ambient PM_1.8 concentration and would be detected with routine PM_2.5 filter samples. V, Zn, Se, NO₃ ^-, SO₄ ^2-, and NH₄ ⁺ also experienced seasonal size distribution shifts that enhanced the specific deposition efficiency in the tracheobronchial and pulmonary regions during the summer months (p < 0.05). This enhanced deposition would not be detected by routine filter samples because all of the size distribution changes occur at particle diameters <2.5 μm. This study demonstrates that changes to the particle size distributions (<2.5 μm) can enhance respiratory deposition efficiencies for trace metals and/or water-soluble ions and this may contribute to seasonal shifts in PM toxicity.     

Development and application of a simultaneous measurement method for gaseous ammonia and particulate ammonium in ambient air

Ammonia gas is one of the precursors contributing to the formation of secondary particulate ammonium via reactions with atmospheric acids, such as sulfuric and/or nitric acids, which are present in ambient air. In this study, a new instrument that is suitable for measuring ammonia gas and fine particulate ammonium (PM_2.5 NH₄⁺) concentrations simultaneously under ambient conditions was developed. A wetted frit sampler was connected in the back of a counter-current flow tube (CCFT) sampler, and the NH₃ gas and PM_2.5 NH₄⁺ samples were collected by CCFT and wetted frit samplers, respectively. An air sample was drawn through the samplers at a flow rate of 1.0 dm³ min^?1 and an absorption water flow rate of 120 mm³ min^?1. Then, the ammonium that formed in the absorption solution was detected by the indophenol method using a continuous flow analysis system. The estimated detection limits were 43 and 49 ng m^?3 for ammonia gas and PM_2.5 NH₄⁺, respectively. Notably, the ammonia gas was collected on the CCFT sampler with a collection efficiency of 98.5%, but most of the PM_2.5 NH₄⁺ passed through it and was captured on the wetted frit sampler with a collection efficiency of approximately 100%. The present method was applied to measure NH₃ gas and PM_2.5 NH₄⁺ at two urban sites: Osaka, Japan and Ho Chi Minh City, Vietnam. It was found that the simultaneous measurement method performed very well and that the measured concentrations were comparable with those obtained with the annular denuder method.

Copyright © 2016 American Association for Aerosol Research     

Analysis of Aerosolized Particulates of Feedyards Located in the Southern High Plains of Texas

The objective of this study was to quantify, size, and examine the composition of particulates found in ambient aerosolized dust of four large feedyards in the Southern High Plains. Ambient air samples (concentration of dust) were collected upwind (background) and downwind of the feedyards. Aerosolized particulate samples were collected using high volume sequential reference ambient air samplers, PM ₁₀ and PM _2.5 , laser strategic aerosol monitors, cyclone air samplers, and biological cascade impactors. Weather parameters were monitored at each feedyard. The overall (main effects and estimable interactions) statistical (P < 0.0001) general linear model statement (GLM) for PM ₁₀ data showed more concentration of dust (μg/m ³ of air) downwind than upwind and more concentration of dust in the summer than in the winter. PM _2.5 concentrations of dust were comparable for 3 of 4 feedyards upwind and downwind, and PM _2.5 concentrations of dust were lower in the winter than in the summer. GLM (P < 0.0001) data for cascade impactor (all aerobic bacteria, Enterococcus spp, and fungi) mean respirable and non-respirable colony forming units (CFU) were 676 ± 74 CFU/m ³ , and 880 ± 119 CFU/m ³ , respectively. The PM ₁₀ geometric mean size (±GSD) of particles were analyzed in aerosols of the feedyards (range 1.782 ± 1.7 μm to 2.02 ± 1.74μm) and PM _2.5 geometric mean size particles were determined (range 0.66 ± 1.76 μm to 0.71 ± 1.71 μm). Three of 4 feedyards were non-compliant for the Environmental Protection Agency (EPA) concentration standard (150 μg/m ³ /24 h) for PM ₁₀ particles. This may be significant because excess dust may have a negative impact on respiratory disease.     

Hong Kong vehicle emission changes from 2003 to 2015 in the Shing Mun Tunnel

ABSTRACT

This study characterized motor vehicle emission rates and compositions in Hong Kong's Shing Mun tunnel (SMT) during 2015 and compared them to similar measurements from the same tunnel in 2003. Average PM_2.5 concentrations in the SMT decreased by ～70% from 229.1 ± 22.1 µg/m³ in 2003 to 74.2 ± 2.1 µg/m³ in 2015. Both PM_2.5 and sulfur dioxide (SO₂) emission factors (EF_D) were reduced by ～80% and total non-methane (NMHC) hydrocarbons EF_D were reduced by 44%. These reductions are consistent with long-term trends of roadside ambient concentrations and emission inventory estimates, indicating the effectiveness of emission control measures. EF_D changes between 2003 and 2015 were not statistically significant for carbon monoxide (CO), ammonia (NH₃), and nitrogen oxides (NO_x). Tunnel nitrogen dioxide (NO₂) concentrations and NO₂/NO_x volume ratios increased, indicating an increased NO₂ fraction in the primary vehicle exhaust emissions. Elemental carbon (EC) and organic matter (OM) were the most abundant PM_2.5 constituents, with EC and OM, respectively, contributing to 51 and 31% of PM_2.5 in 2003, and 35 and 28% of PM_2.5 in 2015. Average EC and OM EF_D decreased by ～80% from 2003 to 2015. The sulfate EF_D decreased to a lesser degree (55%) and its contribution to PM_2.5 increased from 10% in 2003 to 18% in 2015, due to influences from ambient background sulfate concentrations. The contribution of geological materials to PM_2.5 increased from 2% in 2003 to 5% in 2015, signifying the importance of non-tailpipe emissions.

© 2018 American Association for Aerosol Research     

Characteristics of PM2.5 Episodes Revealed by Semi-Continuous Measurements at the Baltimore Supersite at Ponca St

Highly time-resolved measurements of PM_2.5, its major constituents, particle size distributions (9 nm to 20 μ m), CO, NO/NO₂, and O₃, and meteorological parameters were made from February through November 2002, at the Baltimore Supersite at Ponca St. using commercial and prototype semi-continuous instruments. The average PM_2.5 mass concentration during the study period was 16.9 μ g/m³ and a total of 29 PM_2.5 pollution episodes, each in which 24-h averaged PM_2.5 mass concentrations exceeded 30.0 μ g/m³ for one or more days, were observed. Herein, 6 of the worst episodes are discussed. During these events, PM_2.5 excursions were often largely due to elevations in the concentration of one or two of the major species. In addition, numerous short-term excursions were observed and were generally attributable to local sources. Those in OC, EC, nitrate, CO, and NO_x levels were often observed in the morning traffic hours, particularly before breakdown of nocturnal inversions. Moreover, fresh accumulation aerosols from local stationary combustion sources were observed on several occasions, as evidenced by elevations in elemental markers when winds were aligned with sources resulting in PM_2.5 increments of ～ 17 μ g/m³. Overall, the results described herein show that concentrations of PM_2.5 and its major constituents vary enormously on time scales ranging from < 1 hr to several days, thus imposing a more highly complex pattern of pollutant exposure than can be captured by 24-hr integrated methods, alone. The data suggest that control of a limited number of local sources might achieve compliance with daily and annual PM_2.5 standards.     

Evaluation of a particle trap laser desorption mass spectrometer (PT-LDMS) for the quantification of sulfate aerosols

A particle trap laser desorption mass spectrometer (PT-LDMS) has been developed for the online measurements of the chemical composition of submicron aerosol particles. The PT-LDMS was evaluated by both laboratory and ambient measurements, with the focus being the quantification of sulfate aerosols. Ammonium sulfate ((NH₄)₂SO₄) is generally the predominant form of sulfate aerosols in urban air; hence, it is used as a material for laboratory experiments and calibration. Major fragments of (NH₄)₂SO₄ were observed at mass-to-charge ratios (m/z) of 48 (SO⁺) and 64 (SO₂⁺). The dependence of sensitivity (expressed as the ratio of m/z 48 signal to sulfate mass) on laser power and cell temperature was investigated. An intercomparison of PT-LDMS with a commercial sulfate particle analyzer (SPA) and filter sampling was performed in Tokyo. Good agreement was observed between SPA and filter analysis (slope = 0.98, r² = 0.99). Although the mass concentration of sulfate measured by PT-LDMS exhibited a tight correlation with that measured by SPA, the mass concentration measured by PT-LDMS tended to underestimate that measured by SPA (slope = 0.70, r² = 0.96). While the discrepancy can be mainly attributed to the difference in size cut between PT-LDMS (approximately PM₁) and SPA (PM_2.5), differences in vaporization efficiency were also found to be important.

Copyright © 2016 American Association for Aerosol Research     

Characterization of size-resolved aerosol components using proton induced X-ray emission, inductively coupled plasma optical emission spectrometry and ion chromatography

Size-resolved aerosol monitoring for PM₁₀, PM_2.5, and PM_1.0 was performed to qualify and quantify the elements and ions by using proton induced X-ray emission (PIXE), inductively coupled plasma optical emission spectrometry (ICP-OES), and ion chromatography (IC) analysis. Time-resolved aerosol samplings based on 2-hour and 14-hour intervals were carried out during daytime and nighttime, respectively. Physical and chemical properties of size-resolved aerosols were investigated to characterize air quality in the national park area of Gyeongju, Korea. The PIXE and ICPOES methods made elemental mass of Al, Si, S, K, Ca, Ti, Cr, Fe, Sr, and Pb. And ions of Na⁺, NH₄ ⁺, Ca²⁺, Cl^?, NO ₃ ^? , and SO ₄ ^2? were analyzed by the IC method. The mass concentrations of Si, S, Ti, and Pb determined by PIXE showed relatively good correlation with those determined by ICP-OES. But Fe and Sr had worse correlations with an average R² of 0.4703 and 0.4825, respectively. The PIXE method was a good alternative to measure chemical species of Al, Si, S, K, Ca, Ti, Cr, and Pb for size-resolved aerosols except Fe and Sr in this study. The average relative errors of sizeresolved elements for 2-hour and 14-hour interval collections were 10.1±5.7% (0.1–28.3%) and 9.9±7.7% (1.3–38.4%). Ammonium sulfates (AS), mineral dust (MD), and sea salt (SS) aerosols were reconstructed from the elements determined by PIXE and ICP-OES and ions obtained by IC. The mass concentration of MD was calculated with crustal elements of Al, Si, Ca, Ti, and Fe, which are associated with soil erosion. The average relative error of MD was the lowest value of 0.8% in the PM₁₀ regime and the highest value of 10.0% in the PM_1.0 regime. The average relative errors of AS for PM₁₀, PM_2.5, and PM_1.0 determined by PIXE, ICP-OES, and IC showed relatively lower values of 0.8–5.7%, 1.7–5.9%, and 3.3–8.3%, respectively. The average mass concentrations of AS, MD, and SS of PM₁₀, PM_2.5, and PM_1.0 except submicron SS determined by PIXE were comparable to those determined by ICP-OES and IC within the acceptable relative errors.     

PM1.0 and PM2.5 Characteristics in the Roadside Environment of Hong Kong

Daily mass concentrations of PM _1.0 (particles less than 1.0 μm in diameter), PM _2.5 (particles less than 2.5 μm in diameter), organic carbon (OC), and elemental carbon (EC) were measured from January through May 2004 at a heavily trafficked sampling site in Hong Kong (PU). The average concentrations for PM _1.0 and PM _2.5 were 35.9 ± 12.4 μ g cm ^{? 3} and 52.3 ± 18.3 μ g cm ^{? 3} . Carbonaceous aerosols were the dominant species in fine particles, accounting for ～ 45.7% of PM _1.0 and ～ 44.4% of PM _2.5 . During the study period, seven fine-particle episodes occurred, due to the influence of long-range transport of air masses from mainland China. PM _1.0 and PM _2.5 responded in similar ways; i.e., with elevated mass and OC concentrations in those episode days. During the sampling period, PM _1.0 OC and EC generally behaved similarly to the carbonaceous aerosols in PM _2.5 , regardless of seasonal variations and influence by regional pollutions. The low and relatively constant OC/EC ratios in PM _1.0 and PM _2.5 indicated that vehicular emissions were major sources of carbonaceous aerosols. PM _1.0 and PM _2.5 had the same dominant sources of vehicular emissions in winter, while in spring PM _2.5 was more influenced by PM _{1 ? 2.5} (particles 1–2.5 μ m in diameter) that did not form from vehicle exhausts. Therefore, PM _1.0 was a better indicator for vehicular emissions at the Roadside Station.     

Dominant Mechanisms that Shape the Airborne Particle Size and Composition Distribution in Central California

The size and composition of ambient airborne particulate matter is reported for winter conditions at five locations in (or near) the San Joaquin Valley in central California. Two distinct types of airborne particles were identified based on diurnal patterns and size distribution similarity: hygroscopic sulfate/ammonium/nitrate particles and less hygroscopic particles composed of mostly organic carbon with smaller amounts of elemental carbon. Daytime PM₁₀ concentrations for sulfate/ammonium/nitrate particles were measured to be 10.1 μ g m^?3, 28.3 μ g m^?3, and 52.8 μ g m^?3 at Sacramento, Modesto and Bakersfield, California, respectively. Nighttime concentrations were 10–30% lower, suggesting that these particles are dominated by secondary production. Simulation of the data with a box model suggests that these particles were formed by the condensation of ammonia and nitric acid onto background or primary sulfate particles. These hygroscopic particles had a mass distribution peak in the accumulation mode (0.56–1.0 μ m) at all times. Daytime PM₁₀ carbon particle concentrations were measured to be 9.5 μ g m^?3, 15.1 μ g m^?3, and 16.2 μ g m^?3 at Sacramento, Modesto, and Bakersfield, respectively. Corresponding nighttime concentrations were 200–300% higher, suggesting that these particles are dominated by primary emissions. The peak in the carbon particle mass distribution varied between 0.2–1.0 μ m. Carbon particles emitted directly from combustion sources typically have a mass distribution peak diameter between 0.1–0.32 μ m. Box model calculations suggest that the formation of secondary organic aerosol is negligible under cool winter conditions, and that the observed shift in the carbon particle mass distribution results from coagulation in the heavily polluted concentrations experienced during the current study. The analysis suggests that carbon particles and sulfate/ammonium/nitrate particles exist separately in the atmosphere of the San Joaquin Valley until coagulation mixes them in the accumulation mode.     

Source Identification of Size-Segregated Aerosol in Münster,Germany, by Factor Analysis

Sources of size-segregated PM ₁₀ , as collected with a five stage Berner type impactor during six intensive measurement campaigns between January 2006 and August 2007 in Münster, NW Germany, were studied by applying factor analysis. PM samples were collected twice a day, each with a sampling duration of 5 to 7.5 hours. Samples were analyzed for water soluble ions, Ca²⁺, Cl^?, Mg²⁺, Na⁺, NH⁺ ₄ , NO^? ₃ , SO^2? ₄, and elemental and organic carbon. Positive matrix factorization (PMF) was used for source apportionment where each size class accounted for a single variable. Five factors were identified of which at least four could be found during each season. Traffic, ammonium nitrate, and long distance transport showed a weekly cycle, whereas the factor representing power generation and industrial products seemed to be relatively stable through the week. Sea salt particles were independent of the day of week. The five factors do not only have a similar composition, but also a similar size distribution, throughout all seasons of the year. Particles from long-distance transport were identified in the accumulation mode while PM originating from power generation were characterized by a larger diameter. Sea salt aerosol consisted mainly of coarse particles, ammonium nitrate is mainly found in the largest size fraction. Even without a detailed chemical trace elements analysis, precise PM source apportionment was accomplished.     

PM2.5 measurements in wildfire smoke plumes from fire seasons 2005–2008 in the Northwestern United States

PM_2.5 surface concentrations were measured in smoke emitted by four wildfire events during fire seasons 2005–2008. These measurements fill a gap in the existing scientific PM_2.5 observation database by providing a targeted wildfire-specific observation dataset. Four deployments occurred during various fire types including a managed-for-fuel-treatment wildfire complex, a wildfire complex, and two regional fire events. The maximum 24-h averaged values for each case were: 94.5 μg/m³ (2005), 425 μg/m³ (2006), 118 μg/m³ (2007), and 247 μg/m³ (2008). While these values are high, the diurnal concentration median and first quartile values remain below 35 and 10 μg/m³, respectively. For all cases, the hourly diurnal patterns exhibit peak concentrations in the mid-morning and low concentrations in the mid-afternoon. Correlations between daily area actively burning and observed PM_2.5 concentrations were significant for all cases and concentration patterns were found to be similar by geographic location rather than by type of fire (single vs. region-wide). Multiple co-located monitor types, the Environmental Proof Beta Attenuation Monitor, which measures PM_2.5 concentrations using a beta-beam aimed at particulates collected on filter tape, and the E-SAMPLER and DataRAM, which both use nephelometry to measure PM_2.5 concentrations, showed statistically good agreement.     

Twenty Four-Hour PC-BOSS Air-Monitoring Results from the NETL Fine-Particulate Sampling Site in Pittsburgh,Pennsylvania: An Annual Perspective

The concentration and composition of PM _2.5 from May to September of 2000 and monthly trends in ambient fine-particulate material concentrations from October 1999 through December 2000 at the National Energy Technology Laboratory's airmonitoring site in Pittsburgh are reported. Twenty four-hour integrated samples were collected using the Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS), a multichannel integrated diffusion denuder sampler designed for routine determination of the chemical composition of ambient particulate matter. The fine-particulate pollutants determined were sulfate estimated as ammonium sulfate, nonvolatile organic material, semivolatile organic material lost from particles during sampling, elemental carbon, nitrate estimated as ammonium nitrate, including ammonium nitrate lost from particles during sampling and elemental content determined by PIXE (for a limited number of samples). Episodes with elevated sulfate and organic material (both semivolatile and nonvolatile) concentrations were seen throughout this period. For the purpose of this discussion, an episode was defined as all times when 3 h average TEOM monitor PM _2.5 concentrations exceeded 30 μg/m³. The use of estimated back-trajectories indicated that during the periods for which these elevated concentrations were observed, pollutants were transported predominantly from the Southwest from the Ohio River Valley to the sampling site. For days when fine particulate episodes occurred, back-trajectory computations were derived for time intervals for which PM _2.5 TEOM concentrations exceeded 30 μg/m³. However, for nonepisode days, back trajectories were computed over a 24 h period. Average PC-BOSS–constructed PM _2.5 concentration (including semivolatile components lost from particles during sampling) for the period from October 1999 through December 2000 was 19 μg/m ³ , excluding crustal material concentration.     

ALIPHATIC,POLYCYCLIC AROMATIC HYDROCARBONS AND NITRATED-POLYCYCLIC AROMATIC HYDROCARBONS IN PM 10 IN SOUTHWESTERN MEXICO CITY

A sampling campaign of airborne particles ≤ 10 μ m (PM ₁₀ ) was carried out from February to April of 2004 at the Universidad Nacional Autónoma de México in southwestern Mexico City. The average PM ₁₀ mass concentration was 51 ± 14 μ g m^?3. Extracted organic matter was determined, with a mean of 6.5 ± 1.7 μ g m^?3, which represents 12.9% of PM ₁₀ mass concentration. The standard additions method was used on real samples at four concentration levels for 13 n-alkanes, 14 PAHs and 5 nitro-PAHs. The average concentration for the sum was 99.04 ng m^{? 3} for n-alkanes, 4.9 ng m^?3 for PAHs and 710 pg m^{? 3} for nitro-PAHs. Higher concentrations of n-alkanes > C ₂₄ were found, indicating biogenic emissions as the dominant source. Coronene, benzo[ghi]perylene, benzo[b+j+k]fluoranthenes and indeno[1,2,3-cd]pyrene were the most abundant PAHs, suggesting a strong contribution from incomplete combustion of gasoline. The PAHs considered for calculating BaPE represented 52% of the total PAHs analyzed. The presence of 9-nitroanthracene indicates direct emission from diesel combustion and heterogeneous nitrating reactions on sorbed particles, while 2-nitrofluoranthene, indicates gas-phase reactions with fluoranthene, hydroxyl (OH^?) and/or nitrate (NO ₃ ^?) radicals in the presence of nitrogen oxides (NOx).     

Hydrochemical and stable isotopic assessment of groundwater quality and its variations in rice-growing areas in East China

Agricultural activities are frequently associated with water contamination. Thus, the development of efficient strategies for groundwater protection in agricultural areas requires an assessment of the contaminants. Given this perspective, groundwater quality monitoring is carried out in a rice-growing area in Hangjiahu Plain, East China. Thirty-two piezometers are installed to measure physico-chemical parameters such as major ions, field-measured parameters (pH, electrical conductivity (EC), dissolved oxygen, and temperature), and δ¹⁵N isotopic ratios and their variations in space and time. The groundwater shows a variable chemical composition, e.g. EC ranged from 760 to 2,300 μS cm^?1. Most groundwater is weakly acidic, and is characterized as Ca²⁺ + Na⁺? HCO₃ ^? + SO₄ ^2? + Cl^? type. The results demonstrate NH₄ ⁺ coming from agricultural activities and SO₄ ^2? deriving from natural chemical inputs are the major contaminants in the groundwater at the study area. Correlations among NO₃ ^?, NH₄ ⁺ and K⁺ suggest that these ions come from the same source of fertilizer and indicate a significant degree of nitrification in the study area. The highly positive correlations among the variables of HCO₃ ^?, SO₄ ^2?, and Mg²⁺ indicated that these ions were derived from the same source of natural chemical inputs. Nitrate isotopic composition suggests that nitrate in groundwater originates from chemical fertilizers, manure, and soil organic matter.     

Charged Membrane Ultrafiltration of Toxic Metal Oxyanions and Cations from Single- and Multisalt Aqueous Solutions

Abstract

With application to the treatment of nonferrous metals production streams, the toxic metals As(V), Se(IV), As(III), and Cd(II) are separated from single-and multisalt aqueous solutions by continuous-flow, membrane ultrafiltration with charged, noncellulosic membranes. The single-salt aqueous solutions of As(V), Se(IV), As(III), or Cd(II) are investigated over pH 5 to 10, metal concentrations in the range 0.5 to 20.0 mM, and transmembrane pressure differences from 2.8 × 10⁵ to 5.6 × 10⁵ N/m², with the effects of these three independent variables established on the metal rejections. The rejections of the monovalent oxyanions H₂AsO₄ ^?, HSeO₃ ^?, and H₂AsO₃ ^? (with sodium as the counterion) are of the order 0.85, and those of the divalent HAsO₄ ^2?, SeO₃ ^2? (and SO₄ ^2?), and of Cd²⁺ are of the order 0.95 for 6.0 mM feed streams. Comparisons are made with the halides, NO₃ ^?, and ClO₄ ^?. The rejection behavior of multisalt solutions of H₂AsO₄ ^? and HSeO₃ ^? is not influenced by the presence of sulfate, but Cd²⁺ produces a decrease in the rejection of Se(IV). For feed streams 2.0 mM each in H₂AsO₄ ^?, HSeO₃ ^?, Cd²⁺, and Zn²⁺ at pH 5, the presence of a high sulfate concentration does not affect the metal rejections, except at greater than 14.0 mM where the Se(IV) rejection begins to decline sharply