Judith A. Perlinger

Past, Present, and Future Controls on Levels of Persistent Organic Pollutants in the Global Environment

Understanding the legacy of persistent organic pollutants requires studying the transition from primary to secondary source control.

Morphology and mixing state of aged soot particles at a remote marine free troposphere site: Implications for optical properties

The radiative properties of soot particles depend on their morphology and mixing state, but their evolution during transport is still elusive. Here we report observations from an electron microscopy analysis of individual particles transported in the free troposphere over long distances to the remote Pico Mountain Observatory in the Azores in the North Atlantic. Approximately 70% of the soot particles were highly compact and of those 26% were thinly coated. Discrete dipole approximation simulations indicate that this compaction results in an increase in soot single scattering albedo by a factor of ≤2.17. The top of the atmosphere direct radiative forcing is typically smaller for highly compact than mass-equivalent lacy soot. The forcing estimated using Mie theory is within 12% of the forcing estimated using the discrete dipole approximation for a high surface albedo, implying that Mie calculations may provide a reasonable approximation for compact soot above remote marine clouds.

Kinetics models for trichloroethylene transformation by zero-valent iron

Abstract Five models that account for experimental observations of kinetics and surface properties during trichloroethylene (TCE) transformation by iron were compared in terms of accuracy in fitting sixteen TCE concentration versus time profiles obtained from the literature. The models were based on Henri–Michaelis–Menten/Langmuir–Hinshelwood–Hougen–Watson (HMM/LHHW) kinetics and considered sorption to inactive sites, sorption and reaction at multiple binding energy sites, and catalyst deactivation in increasing order of complexity. The internal and overall effectiveness factors for all datasets were one, indicating that TCE transformation kinetics were not mass transfer limited during the initial stages of the reaction. At low TCE loading, model results suggest that the overall transformation is reaction limited. At high TCE loading however, the overall transformation appears to be sorption limited due to competitive self-inhibition of TCE on the iron surface. Model results suggest that the addition of an exponential decay term that describes catalytic deactivation best described reaction kinetics under widely different experimental conditions. Model results also suggest that TCE adsorbs to two adjacent sites, and that concentrations of active and inactive sites and TCE loading (TCE concentration per active site) are the dominant factors that control TCE transformation kinetics. The results also suggest that in experiments initiated in the zero-order region, the order of the reaction may change to first-order and then back to zero-order as the reaction progresses due to a decrease in active site concentration as the catalytic surface is deactivated. Comparisons of fitted and reported model parameters suggest that specific surface area of iron from BET isotherms may not provide a true representation of the actual number of sites on the iron surface.

Climatic, biological, and land cover controls on the exchange of gas-phase semivolatile chemical pollutants between forest canopies and the atmosphere.

An ecophysiological model of a structured broadleaved forest canopy was coupled to a chemical fate model of the air-canopy exchange of gaseous semivolatile chemicals to dynamically assess the short-term (hours) and medium term (days to season) air-canopy exchange and the influence of biological, climatic, and land cover drivers on the dynamics of the air-canopy exchange and on the canopy storage for airborne semivolatile pollutants. The chemical fate model accounts for effects of short-term variations in air temperature, wind speed, stomatal opening, and leaf energy balance, all as a function of layer in the canopy. Simulations showed the potential occurrence of intense short/medium term re-emission of pollutants having log K(OA) up to 10.7 from the canopy as a result of environmental forcing. In addition, relatively small interannual variations in seasonally averaged air temperature, canopy biomass, and precipitation can produce relevant changes in the canopy storage capacity for the chemicals. It was estimated that possible climate change related variability in environmental parameters (e.g., an increase of 2 °C in seasonally averaged air temperature in combination with a 10% reduction in canopy biomass due to, e.g., disturbance or acclimatization) may cause a reduction in canopy storage capacity of up to 15-25%, favoring re-emission and potential for long-range atmospheric transport. On the other hand, an increase of 300% in yearly precipitation can increase canopy sequestration by 2-7% for the less hydrophobic compounds.

Prediction of gas collection efficiency and particle collection artifact for atmospheric semivolatile organic compounds in multicapillary denuders.

A modeling approach is presented to predict the sorptive sampling collection efficiency of gaseous semivolatile organic compounds (SOCs) and the artifact caused by collection of particle-associated SOCs in multicapillary diffusion denuders containing polydimethylsiloxane (PDMS) stationary phase. Approaches are presented to estimate the equilibrium PDMS-gas partition coefficient (K(pdms)) from a solvation parameter model for any compound, and, for nonpolar compounds, from the octanol-air partition coefficient (K(oa)) if measured K(pdms) values are not available. These estimated K(pdms) values are compared with K(pdms) measured by gas chromatography. Breakthrough fraction was measured for SOCs collected from ambient air using high-flow (300 L min(-1)) and low-flow (13 L min(-1)) denuders under a range of sampling conditions (-10 to 25 degrees C; 11-100% relative humidity). Measured breakthrough fraction agreed with predictions based on frontal chromatography theory using K(pdms) and equations of Golay, Lövkvist and Jönsson within measurement precision. Analytes included hexachlorobenzene, 144 polychlorinated biphenyl congeners, and polybrominated diphenyl ethers 47 and 99. Atmospheric particle transmission efficiency was measured for the high-flow denuder (0.037-6.3 microm diameter), and low-flow denuder (0.015-3.1 microm diameter). Particle transmission predicted using equations of Gormley and Kennedy, Pich, and a modified filter model, agreed within measurement precision (high-flow denuder) or were slightly greater than (low-flow denuder) measured particle transmission. As an example application of the model, breakthrough volume and particle collection artifact for the two denuder designs were predicted as a function of K(oa) for nonpolar SOCs. The modeling approach is a necessary tool for the design and use of denuders for sorptive sampling with PDMS stationary phase.

Accumulation of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) in organic and mineral soil horizons from four U.S. remote forests

We characterized distributions of 23 polycyclic aromatic hydrocarbons (Σ23PAH) and nine oxygenated PAHs (Σ9OPAH) in four remote forests. We observed highest Σ23PAH and Σ9OPAH concentrations in a coniferous forest in Florida, particularly in organic layers which we attributed to frequent prescribed burning. Across sites, Σ23PAH and Σ9OPAH concentrations strongly increased from surface to humidified organic layers (+1626%) where concentrations reached up to 584 ng g(-1). Concentrations in mineral soils were lower (average 37 ± 8 ng g(-1)); but when standardized per unit organic carbon (OC), PAH/OC and OPAH/OC ratios were at or above levels observed in organic layers. Accumulation in litter and soils (i.e., enrichment factors with depth) negatively correlated with octanol-water partition coefficients (Kow) and therefore was linked to water solubility of compounds. Concentrations of Σ9OPAHs ranged from 6 ± 6 ng g(-1) to 39 ± 25 ng g(-1) in organic layers, and from 3 ± 1 ng g(-1) to 11 ± 3 ng g(-1) in mineral soils, and were significantly and positively correlated to Σ23PAHs concentrations (r(2) of 0.90) across sites and horizons. While OPAH concentrations generally decreased from organic layers to mineral soil horizons, OPAH/OC ratios increased more strongly with depth compared to PAHs, in particular for anthrone, anthraquinone, fluorenone, and acenaphthenequinone. The strong vertical accumulation of OPAH relative to OC was exponentially and negatively correlated to C/N ratios (r(2)=0.67), a measure that often is used for tissue age. In fact, C/N ratios alone explained two-thirds of the variability in OPAH/OC ratios suggesting particularly high retention, sorption, and persistency of OPAHs in old, decomposed carbon fractions.

Performance of a High Flow Rate, Thermally Extractable Multicapillary Denuder for Atmospheric Semivolatile Organic Compound Concentration Measurement

A high flow rate (300 L min(-1)) multicapillary denuder was designed to collect trace atmospheric semivolatile organic compounds (SOCs). The denuder is coated with a reusable, polydimethylsiloxane stationary phase as a nonselective absorbent for SOCs. A solvent-free thermal desorption method was developed, including sample cleanup, that is selective for nonpolar SOCs, and has low consumables cost per sample. The entire sample is transferred into the gas chromatograph to minimize the sampling time required to collect detectable analyte mass. Trace concentrations (0.1-100 pg m(-3)) of polychlorinated biphenyls and hexachlorobenzene were measured in the atmosphere near Lake Superior in sample times of 3.2-6.2 h. Overall method precision was determined using field duplicates and compared to the conventional high-volume sampler method. Method precision (coefficient of variation) of 16% was found for the high-flow denuder compared to 21% for the high-volume method. The relative difference between the two methods was 25%, with the high-flow denuder method giving generally lower concentrations. The high-flow denuder is an alternative to high-volume or passive samplers when it is desirable to separate gaseous from particle-associated SOCs upstream of a filter. The method is advantageous for studies that require high temporal resolution.

Gas-phase cleanup method for analysis of trace atmospheric semivolatile organic compounds by thermal desorption from diffusion denuders.

A novel gas-phase cleanup method was developed for use with a thermal desorption method for analysis of trace semivolatile organic compounds (SOCs) in the atmosphere using diffusion denuder samplers to separate gas-phase from particle-associated fractions. The cleanup selectively removed hydrogen-bonding chemicals from samples, including much of the background matrix of oxidized organic compounds that is present in ambient air samples. Abraham solvation parameters were found to be useful predictors of recovery of compounds through the cleanup method; most compounds with A+B<0.3 and L<or=12.3 were fully recovered through the cleanup method. Addition of the cleanup method successfully produced baseline resolution in air samples and improved method precision. The utility of the method was demonstrated in an investigation of the built environment as a continuing source of semivolatile persistent, bioaccumulative, and toxic chemicals (PBTs) to the atmosphere.

Measurement and Modeling of Atmosphere-Surface Exchangeable Pollutants (ASEPs) To Better Understand their Environmental Cycling and Planetary Boundaries

Pollutants (ASEPs) To Better Understand their Environmental Cycling and Planetary Boundaries Judith A. Perlinger,*,† Hugh S. Gorman, ‡ Emma S. Norman, Daniel Obrist, Noelle E. Selin, Noel R. Urban,† and Shiliang Wu#,† †Department of Civil & Environmental Engineering, Michigan Technological University, Houghton, Michigan 49931, United States ‡Department of Social Sciences, Michigan Technological University, Houghton, Michigan 49931, United States Department of Native Environmental Science, Northwest Indian College, Bellingham, Washington 98226, United States Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada 89512, United States Institute for Data, Systems, and Society and Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States Department of Geological & Mining Engineering & Sciences, Michigan Technological University, Houghton, Michigan 49931, United States