A Study of Headspace Solid-Phase Microextraction in the Analysis of 54 Hydrophobic Pollutants in Remote Alpine Lake Waters with an Emphasis on Analyte Recovery and Storage Time.

Commercially available headspace solid-phase microextraction (HS-SPME) fibers have been used for years to extract pesticides and polychlorinated biphenyls from aqueous samples at the expected ultratrace levels (picograms per liter or parts per quadrillion) in alpine lakes. Several variables of the HS-SPME technique have been adequately evaluated, including water temperature, pH, salt content, fiber type and coating thickness, length of fiber-sample exposure, and liquid immersion versus headspace exposure; but surprisingly, analyte recovery as a function of analyte concentration and storage time has not been included in previous studies, which can be important for remote sampling sites. Seven hydrophobic chlorinated pollutants were identified in alpine lake water (out of 54 analyzed); but recovery using the common SPME technique was found to be inconsistent as the analyte concentration decreases, and the recovery trend as a function of concentration varies on a compound-to-compound basis that could result in a large underestimation of analyte concentrations in field samples. Of the 54 compounds surveyed, o,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-DDT, p,p'-dichlorodiphenyldichloroethylene (DDE), o,p'-DDE, chlorthal-dimethyl, endosulfan I, γ-hexachlorocyclohexane, heptachlor, and trans-nonachlor were generally measured at concentrations between 1 and 150 pg/L (parts per quadrillion). No study to date has evaluated this commonly used but unstandardized technique for analyte recovery as a function of analyte concentration or storage time of aqueous samples. Environ Toxicol Chem 2023;42:1199-1211. © 2023 SETAC.

Spatial Distribution and Location of Natural Organic Matter on Sediment Particles by Scanning Electron Microscopic Analysis and the Development of a New Persistent Organic Pollutant-Sediment Kinetic Desorption Model.

Natural organic matter (NOM) has long been shown to be the dominant factor in determining equilibrium and kinetic processes during sorption and desorption phenomena in sediment and soil experiments. Although several models have been suggested for predicting these processes, few offer mechanistic interpretations because the spatial location of organic matter on sediment particles is unknown. This investigation manually examined sediment particles from multiple locations, containing varying concentrations of NOM, using scanning electron microscopy with energy dispersive X-ray spectroscopy to determine the types of particles present by categorizing them as individual particles, aggregates, and "other" (detritus, algae, etc.). These types of particles were subsequently analyzed for their elemental composition, specifically the spatial location of carbon. By creating a carbon map of each particle, this investigation has determined that organic matter tends to occur in 2 forms: large aggregates or dispersed across individual sediment particles. These findings were then used to propose a more mechanistically sound mathematical model for pollutant desorption phenomena, assigning the traditional labile kinetic release component to the dispersed NOM spread randomly across sediment particles and the nonlabile kinetic release component to diffusion from densely packed NOM aggregates. Environ Toxicol Chem 2021;40:323-332. © 2020 SETAC.

Atmospheric Deposition of Coal-Related Pollutants in the Pacific Northwest of the United States from 1950 to 2016.

Coal-related elements are toxic and persistent pollutants that have spread globally since the industrial revolution, mainly from point-source emissions. A sediment core was collected from Deep Lake in northeastern Washington State (USA) by the Washington State Department of Ecology, with the aim of assessing recent changes in atmospheric deposition in the US Pacific Northwest. The core was divided into depth intervals and dated by lead-210. A sample from each cross section was digested and analyzed for toxic metals and metalloids using inductively coupled plasma-mass spectrometry. Data show recent increases in the concentrations of arsenic, barium, selenium, and mercury. Comparison with 1993 US Geological Survey ice core data from the Upper Fremont Glacier in Wyoming (USA), Asian coal consumption data, and weather patterns suggests that pollutant inputs to Deep Lake sediments are the result of coal-burning activities in the Asia-Pacific region. Most notably, mercury deposition in Deep Lake has increased from approximately 20 ppb in 1996 to 9470 ppb in 2014 (an ~400-fold increase), and since 1993 when the ice core was analyzed. Environ Toxicol Chem 2020;39:335-342. © 2019 SETAC.

High-density element concentrations in fish from subtidal to hadal zones of the Pacific Ocean.

Anthropogenic use of high density, toxic elements results in marine pollution which is bio-accumulating throughout marine food webs. While there have been several studies in various locations analyzing such elements in fish, few have investigated patterns in these elements and their isotopes in terms of ocean depth, and none have studied the greatest depth zones. We used a flame atomic absorption spectrophotometer-hydride system and an inductively coupled plasma-mass spectrometer to determine concentrations of the high-density elements arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni), selenium (Se), plus the light-metal barium (Ba), in fish ranging from bathyal (1000 m in Monterey Bay) to upper hadal zones (6500-7626 m in the Kermadec and Mariana Trenches) in the Pacific Ocean. Five species of fish-including the Mariana Trench snailfish, the world's deepest known fish newly discovered-were analyzed for patterns in total element concentration, depth of occurrence, Se:Hg ratio, plus mercury isotopes in the deepest species. Co and As levels decreased with depth. In the Mariana Trench, Pb, Hg, Cd, and Cu were higher than in all other samples, and higher in those plus Ba than in the Kermadec Trench. The latter samples had far higher Ni and Cr levels than all others. Mercury relative isotope analysis showed no depth trends in the deepest species. Se:Hg showed a large molar excess of Se in bathyal flatfish species. These patterns indicate that exposures to pollutants differ greatly between habitats including trenches of similar depths.

Fraction of organic carbon predicts labile desorption rates of chlorinated organic pollutants in laboratory-spiked geosorbents.

The resuspension of large volumes of sediments that are contaminated with chlorinated pollutants continues to threaten environmental quality and human health. Whereas kinetic models are more accurate for estimating the environmental impact of these events, their widespread use is substantially hampered by the need for costly, time-consuming, site-specific kinetics experiments. The present study investigated the development of a predictive model for desorption rates from easily measurable sorbent and pollutant properties by examining the relationship between the fraction of organic carbon (fOC) and labile release rates. Duplicate desorption measurements were performed on 46 unique combinations of pollutants and sorbents with fOC values ranging from 0.001 to 0.150. Labile desorption rate constants indicate that release rates predominantly depend upon the fOC in the geosorbent. Previous theoretical models, such as the macro-mesopore and organic matter (MOM) diffusion model, have predicted such a relationship but could not accurately predict the experimental rate constants collected in the present study. An empirical model was successfully developed to correlate the labile desorption rate constant (krap) to the fraction of organic material where log(krap)=0.291-0.785 . log(fOC). These results provide the first experimental evidence that kinetic pollution releases during resuspension events are governed by the fOC content in natural geosorbents.

A comparison of two techniques for studying sediment desorption kinetics of hydrophobic pollutants.

A comparison of two techniques (gaseous purge and vial desorption) for studying the kinetics of desorption of hydrophobic pollutants from natural sediments was conducted using identical, pre-equilibrated pollutant-sediment suspensions. Desorption profiles for the two techniques [for Lindane, Aldrin, 2,2'-dichlorobiphenyl (2,2'-DCB), 4,4'-dichlorobiphenyl (4,4'-DCB), and 2,2',6,6'-tetrachlorobiphenyl (TCB)] were then compared, based on the distribution of pollutant mass between the labile (fast) and non-labile (slow) desorption phases and the release rate constants for each phase of release. The vial desorption technique shows many practical advantages over the gaseous purge technique, including its more realistic mixing conditions, the use of an independent sample for each data point (as opposed to a calculation of a cumulative mass purged at each time point), the fact that the vials constitute a closed system and are therefore less subject to ambient contamination, and the relatively low demands of time and money for the vial technique. No consistent trends in labile rate constants or in pollutant distribution between the labile and non-labile phase were observed between the two techniques. A comparison of kinetic parameters shows much faster non-labile rate constants for the gaseous purge technique, attributed to the violent, continuous agitation employed, which likely disrupted sediment aggregates and oxidized the natural organic matter associated with the sediment. Non-labile rate constants have implications for the long-term fate of compounds adsorbed to repetitively disturbed sediments. This study suggests that the traditionally less popular vial desorption technique may yield more realistic non-labile desorption rate constants.