Evaluation of the potential of benchmarking to facilitate the measurement of chemical persistence in lakes
The persistence of chemicals in the environment is rarely measured in the field due to a paucity of suitable
methods. Here we explore the potential of chemical benchmarking to facilitate the measurement of
persistence in lake systems using a multimedia chemical fate model. The model results show that persistence
in a lake can be assessed by quantifying the ratio of test chemical and benchmark chemical at as
few as two locations: the point of emission and the outlet of the lake. Appropriate selection of benchmark
chemicals also allows pseudo-first-order rate constants for physical removal processes such as volatilization
and sediment burial to be quantified. We use the model to explore how the maximum persistence
that can be measured in a particular lake depends on the partitioning properties of the test chemical
of interest and the characteristics of the lake. Our model experiments demonstrate that combining
benchmarking techniques with good experimental design and sensitive environmental analytical chemistry
may open new opportunities for quantifying chemical persistence, particularly for relatively slowly
degradable chemicals for which current methods do not perform well.
Identifying chemicals that are planetary boundary threats.
Enhanced Elimination of Perfluorooctane Sulfonate by Menstruating Women: Evidence from Population-based Pharmacokinetic Modeling
Equilibrium Sampling to Determine the Thermodynamic Potential for Bioaccumulation of Persistent Organic Pollutants from Sediment
Equilibrium partitioning (EqP) theory is currently the most widely used approach for linking sediment pollution by persistent hydrophobic organic chemicals to bioaccumulation. Most applications of the EqP approach assume (I) a generic relationship between organic carbon-normalized chemical concentrations in sediments and lipid-normalized concentrations in biota and (II) that bioaccumulation does not induce levels exceeding those expected from equilibrium partitioning. Here, we demonstrate that assumption I can be obviated by equilibrating a silicone sampler with chemicals in sediment, measuring chemical concentrations in the silicone, and applying lipid/silicone partition ratios to yield concentrations in lipid at thermodynamic equilibrium with the sediment (CLip⇌Sed). Furthermore, we evaluated the validity of assumption II by comparing CLip⇌Sed of selected persistent, bioaccumulative and toxic pollutants (polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB)) to lipid-normalized concentrations for a range of biota from a Swedish background lake. PCBs in duck mussels, roach, eel, pikeperch, perch and pike were mostly below the equilibrium partitioning level relative to the sediment, i.e., lipid-normalized concentrations were ≤CLip⇌Sed, whereas HCB was near equilibrium between biota and sediment. Equilibrium sampling allows straightforward, sensitive and precise measurement of CLip⇌Sed. We propose CLip⇌Sed as a metric of the thermodynamic potential for bioaccumulation of persistent organic chemicals from sediment useful to prioritize management actions to remediate contaminated sites.
Long-term temporal trends of persistent organic pollutants (POPs) at global atmospheric monitoring stations including in the Arctic: effectiveness of control strategies and possible influence of climate change.
Emissions, fate and transport of persistent organic pollutants to the Arctic in a changing global climate
Climate change is expected to alter patterns of human economic activity and the associated emissions of chemicals, and also to affect the transport and fate of persistent organic pollutants (POPs). Here, we use a global-scale multimedia chemical fate model to analyze and quantify the impact of climate change on emissions and fate of POPs, and their transport to the Arctic. First, climate change effects under the SRES-A2 scenario are illustrated using case-studies for two well-characterized POPs, PCB153, and α-HCH. Then, we model the combined impact of altered emission patterns and climatic conditions on environmental concentrations of potential future-use substances with a broad range of chemical properties. Starting from base-case generic emission scenarios, we postulate changes in emission patterns that may occur in response to climate change: enhanced usage of industrial chemicals in an ice-free Arctic, and intensified application of agrochemicals due to higher crop production and poleward expansion of potential arable land. We find both increases and decreases in concentrations of POP-like chemicals in the Arctic in the climate change scenario compared to the base-case climate. During the phase of ongoing primary emissions, modeled increases in Arctic contamination are up to a factor of 2 in air and water, and are driven mostly by changes in emission patterns. After phase-out, increases are up to a factor of 2 in air and 4 in water, and are mostly attributable to changes in transport and fate of chemicals under the climate change scenario.
Mountain cold-trapping increases transfer of persistent organic pollutants from atmosphere to cows’ milk
Concentrations of long-lived organic contaminants in snow, soil, lake water and vegetation have been observed to increase with altitude along mountain slopes. Such enrichment, called “mountain cold-trapping”, is attributed to a transition from the atmospheric gas phase to particles, rain droplets, snowflakes and Earth’s surface at the lower temperatures prevailing at higher elevations. Milk sampled repeatedly from cows that had grazed at three different altitudes in Switzerland during one summer was analyzed for a range of persistent organic pollutants. Mountain cold-trapping significantly increased air-to-milk transfer factors of most analytes. As a result the milk of cows grazing at higher altitudes was more contaminated with substances that have regionally uniform air concentrations (hexachlorobenzene, alpha-hexachlorocyclohexane, endosulfan sulfate). For substances that have sources, and therefore higher air concentrations, at lower altitudes (polychlorinated biphenyls, gamma-hexachlorocyclohexane), alpine milk has lower concentrations, but not as low as would be expected without mountain cold-trapping. Differences in the elevational gradients in soil concentrations and air-to-milk transfer factors highlight that cold trapping of POPs in pastures is mostly due to increased gas phase deposition as a result of lower temperatures causing higher uptake capacity of plant foliage, whereas cold trapping in soils more strongly depends on wet and dry particle deposition. Climatic influences on air-to-milk transfer of POPs needs to be accounted for when using contamination of milk lipids to infer contamination of the atmosphere.