title: Mountain cold-trapping increases transfer of persistent organic pollutants from atmosphere to cows' milk.
abstract: 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, α-hexachlorocyclohexane, endosulfan sulfate). For substances that have sources, and therefore higher air concentrations, at lower altitudes (polychlorinated biphenyls, γ-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.
authors.affiliation: Department of Physical & Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada M1C1A4.
authors.forename: Chubashini
authors.initials: C
authors.lastname: Shunthirasingham
authors.forename: Frank
authors.initials: F
authors.lastname: Wania
authors.forename: Matthew
authors.initials: M
authors.lastname: MacLeod
authors.forename: Ying Duan
authors.initials: YD
authors.lastname: Lei
authors.forename: Cristina L
authors.initials: CL
authors.lastname: Quinn
authors.forename: Xianming
authors.initials: X
authors.lastname: Zhang
authors.forename: Martin
authors.initials: M
authors.lastname: Scheringer
authors.forename: Fabio
authors.initials: F
authors.lastname: Wegmann
authors.forename: Konrad
authors.initials: K
authors.lastname: Hungerbühler
authors.forename: Silvia
authors.initials: S
authors.lastname: Ivemeyer
authors.forename: Fritz
authors.initials: F
authors.lastname: Heil
authors.forename: Peter
authors.initials: P
authors.lastname: Klocke
authors.forename: Grazina
authors.initials: G
authors.lastname: Pacepavicius
authors.forename: Mehran
authors.initials: M
authors.lastname: Alaee
mesh_terms: D000388:Air / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis* / Q000737:chemistry; D000531:Altitude; D000818:Animals; D002417:Cattle; D003080:Cold Temperature; D008892:Milk / Q000737:chemistry*; D012987:Soil / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D012987:Soil