Comparison of PoraPak Rxn RP and XAD-2 adsorbents for monitoring dissolved hydrophobic organic contaminants

Accurate determination of the levels of dissolved hydrophobic organic contaminants (HOCs) is an important step in estimating the dynamics of their inputs and losses in aqueous systems. This study explores an alternative method for efficiently sampling dissolved HOCs while mitigating a number of sampling artifacts associated with traditional methods. The adsorption characteristics of a new polymeric resin, PoraPak Rxn RP (PPR), were assessed using sorption isotherm experiments and fixed bed adsorption studies. The adsorption capacities and breakthrough times for four model contaminants (phenol, p-nitrophenol, naphthalene, and 2,4,6-tribromophenol) were proportional to the contaminant’s hydrophobicity. The ability of PPR to isolate dissolved polychlorinated biphenyls (PCBs) in real samples was compared with that of XAD-2, a well-known macroporous polymer that suffers from high background contamination. The results indicated that the PPR resin can be effectively used for monitoring HOCs, with low ∑PCB levels in blanks, decreasing solvent use, and reducing extraction times.     

Characterization of fine aerosol and its inorganic components at two rural locations in New York State

Samples of PM(2.5) were collected to measure the concentrations of its chemical constituents at two rural locations, Potsdam and Stockton, NY from November 2002 to August 2005. These samples were collected on multiple filters at both sites, every third day for a 24-h interval with a speciation network sampler. The Teflo(R) filters were analyzed for PM(2.5) mass by gravimetry, and elemental composition by X-ray fluorescence (XRF). Nylasorb(R) filters and Teflo(R) filters were leached with water and analyzed for anions and cations, respectively, by ion chromatography (IC). Fine particulate matter (PM(2.5)) mass and its inorganic component measurements were statistically characterized, and the temporal behavior of these species were assessed. Over the entire study period, PM(2.5) mass concentrations were lower at Potsdam (8.35 mug/m(3)) than at Stockton (10.24 mug/m(3)). At both locations, organic matter (OM) was the highest contributor to mass. Sulfate was the second highest contributor to mass at 27.0% at Potsdam, and 28.7% at Stockton. Nitrate contributions to mass of 8.9 and 9.5% at Potsdam and Stockton, respectively, were the third highest. At both locations, fine PM mass exhibited an annual cycle with a pronounced summer peak and indications of another peak during the winter, consistent with an overall increase in the rate of secondary aerosol formation during the summer, and increased partitioning of ammonium nitrate to the particle phase and condensation of other semi-volatiles during the winter, respectively. An ion-balance analysis indicated that at both locations, during the summers as well as in the winters, the aerosol was acidic. Lognormal frequency distribution fits to the measured mass concentrations on a seasonal basis indicated the overall increase in particle phase secondary aerosol (sulfate and SOA) concentrations during the summers compared to the winters at both locations.     

Source apportionment of ultrafine and fine particle concentrations in Brisbane, Australia

Purpose

To investigate the significance of sources around measurement sites, assist the development of control strategies for the important sources and mitigate the adverse effects of air pollution due to particle size.

Methods

In this study, sampling was conducted at two sites located in urban/industrial and residential areas situated at roadsides along the Brisbane Urban Corridor. Ultrafine and fine particle measurements obtained at the two sites in June?CJuly 2002 were analysed by positive matrix factorization.

Results

Six sources were present, including local traffic, two traffic sources, biomass burning and two currently unidentified sources. Secondary particles had a significant impact at site 1, while nitrates, peak traffic hours and main roads located close to the source also affected the results for both sites.

Conclusions

This significant traffic corridor exemplifies the type of sources present in heavily trafficked locations and future attempts to control pollution in this type of environment could focus on the sources that were identified.     

Designing ambient particulate matter monitoring program for source apportionment study by receptor modeling

Particulate matter (PM) receptor modeling requires specific intensive input data that is always a challenge to produce cost effectively. A well-designed monitoring program is important to collect such PM ambient data in urban areas with diverse and densely distributed sources. This paper presents a general framework for designing such a monitoring program while emphasizing appropriate quality assurance and quality control elements that are particularly applicable where limited resources are available. Topics for discussion include selection of monitoring sites, sampling and analytical techniques, and the uncertainty estimation for ambient concentration input data. The design framework is illustrated by a case study of a monitoring program for PM source apportionment in the Bangkok Metropolitan Region in which 24-h fine and coarse PM samples were collected using two collocated dichotomous samplers. Comparison between black carbon measurements by Smoke Stain reflectometry and Thermal Optical Transmittance method is highlighted.     

Comparison of the results obtained by four receptor modelling methods in aerosol source apportionment studies

In this work the performance and theoretical background behind two of the most commonly used receptor modelling methods in aerosol science, principal components analysis (PCA) and positive matrix factorization (PMF), as well as multivariate curve resolution by alternating least squares (MCR-ALS) and weighted alternating least squares (MCR-WALS), are examined. The performance of the four methods was initially evaluated under standard operational conditions, and modifications regarding data pre-treatment were then included. The methods were applied using raw and scaled data, with and without uncertainty estimations. Strong similarities were found among the sources identified by PMF and MCR-WALS (weighted models), whereas discrepancies were obtained with MCR-ALS (unweighted model). Weighting of input data by means of uncertainty estimates was found to be essential to obtain robust and accurate factor identification. The use of scaled (as opposed to raw) data highlighted the contribution of trace elements to the compositional profiles, which was key to the correct interpretation of the nature of the sources. Our results validate the performance of MCR-WALS for aerosol pollution studies.     

A chamber study of secondary organic aerosol formation by linalool ozonolysis

The formation of secondary organic aerosol (SOA) produced from linalool ozonolysis was examined using a dynamic chamber system that allowed the simulation of ventilated indoor environments. Experiments were conducted under room temperature (22–23 °C) and air exchange rate of 0.67 h^?1. An effort was made to maintain the product of the concentrations of the two reagents constant. The results suggest that under the conditions when the product of the two reagent concentrations was constant, the relative concentrations play an important role in determining the total SOA formed. A combination of concentrations somewhere in ozone limiting region will produce the maximum SOA concentration. The measured reactive oxygen species (ROS) concentrations at linalool and ozone concentrations relevant to prevailing indoor concentrations ranged from 0.71 to 2.53 nmol m^?3 equivalents of H₂O₂. It was found that particle samples aged for 24 h lost a significant fraction of the ROS compared to fresh samples. The residual ROS concentrations were around 15–69%. Compared with other terpene species like α-pinene that has one endocyclic unsaturated carbon bond, linalool was less efficient in potential SOA formation yields.     

Translocal anti-fracking activism: an exploration of network structure and tie content

ABSTRACT

In order to develop conceptual models that reflect the realities of networked communicative processes scholars must examine both the underlying network structure and the content of these ties. Using mixed methods, I apply a relational perspective to the role of digital technologies in transnational organizing, using activism against high-volume hydraulic fracturing as a case study. In-depth interviews are combined with social network analysis of hyper-linkages between organizations supporting a day of action calling for a ban on fracking, Global Frackdown. Analysis shows that activism against unconventional fossil fuels brings together very localized concerns about environmental risks associated with extractive industries with more abstract global concerns. I apply the concept of translocal to examine environmental organizations and movements. This conceptual shift focuses on the brokerage role of global-minded local groups in mediating global issues back to the hyper-local scale. While international NGOs play a coordinating role, local groups with a global worldview can connect transnational movements to the hyper-local scale by networking with groups that are too small to appear in a transnational network.     

Identification of Sources of Phoenix Aerosol by Positive Matrix Factorization

ABSTRACT

Chemical composition data for fine and coarse particles collected in Phoenix, AZ, were analyzed using positive matrix factorization (PMF). The objective was to identify the possible aerosol sources at the sampling site. PMF uses estimates of the error in the data to provide optimum data point scaling and permits a better treatment of missing and below-detection-limit values. It also applies nonnegativity constraints to the factors. Two sets of fine particle samples were collected by different samplers. Each of the resulting fine particle data sets was analyzed separately. For each fine particle data set, eight factors were obtained, identified as (1) biomass burning characterized by high concentrations of organic carbon (OC), elemental carbon (EC), and K; (2) wood burning with high concentrations of Na, K, OC, and EC; (3) motor vehicles with high concentrations of OC and EC; (4) nonferrous smelting process characterized by Cu, Zn, As, and Pb; (5) heavy-duty diesel characterized by high EC, OC, and Mn; (6) sea-salt factor dominated by Na and Cl; (7) soil with high values for Al, Si, Ca, Ti, and Fe; and (8) secondary aerosol with SO₄ ^-2 and OC that may represent coal-fired power plant emissions.

For the coarse particle samples, a five-factor model gave source profiles that are attributed to be (1) sea salt, (2) soil, (3) Fe source/motor vehicle, (4) construction (high Ca), and (5) coal-fired power plant. Regression of the PM mass against the factor scores was performed to estimate the mass contributions of the resolved sources. The major sources for the fine particles were motor vehicles, vegetation burning factors (biomass and wood burning), and coal-fired power plants. These sources contributed most of the fine aerosol mass by emitting carbonaceous particles, and they have higher contributions in winter. For the coarse particles, the major source contributions were soil and construction (high Ca). These sources also peaked in winter.     

Discussion of “Sensitivity of a molecular marker based positive matrix factorization model to the number of receptor observations” by YuanXun Zhang,Rebecca J. Sheesley,Min-Suk Bae and James J. Schauer

There is no specific number of samples that ensure a satisfactory PMF analysis. The statement made in this paper with respect to a specific number of samples is only applicable to this data set and should not be applied to any other data set.