Time trends of Arctic contamination in relation to emission history and chemical persistence and partitioning properties.
How long does ittake for organic contaminant concentrations to decline in the Arctic after regulatory measures have succeeded in reducing emissions globally? This question is explored by using a zonally averaged global distribution model to estimate the lag-time between the period when emissions begin to decrease and when a decline in a chemical's Arctic Contamination Potential is observed. A long lag is problematic, as contaminant concentrations can continue to increase well after a potential hazard is recognized. Using three different emission scenarios, the chemical property combinations that are most likely to experience a lag on the order of decades were identifed among 96 hypothetical chemicals with different partitioning and reactivity properties. The first such property combination comprises the persistent "swimmers" that reach the Arctic by slow long-range oceanic transport. They require a half-life (t(1/2)) in water of more than 10 years for a significant lag to occur. The second group of compounds experiencing a long lag includes semivolatile chemicals that are in dynamic exchange between atmosphere and ocean. These "multihoppers", with air-water partition coefficients, K(AW) of approximately 0.01, need to be highly persistent in air (t(1/2) >3 years) and surface media (t(1/2) >10 years). Their lag depends both on the oceans' large storage capacity and relatively low stickiness, i.e., a high likelihood of return to the atmosphere. Notably, no lag is predicted for less water soluble multihoppers (K(AW) >1), which are more likely to distribute into soils and foliage, because the terrestrial environment is "stickier" than the oceans, greatly reducing the number of hops these chemical will experience. The oceans thus play a crucial role in facilitating delayed Arctic contamination, either by transporting dissolved contaminants slowly to higher latitudes, or by providing a relatively nonsticky temporary storage reservoir which is in constant exchange with the atmosphere. Precaution advises a swift regulatory response to increasing concentrations in remote marine organisms of substances that have property combinations that are predicted to result in a significant delay between emission reductions and concentration declines.
Gouin
Todd
T
Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, Canada.
Wania
Frank
F
D000388:Air; D001110:Arctic Regions; D017753:Ecosystem; D004784:Environmental Monitoring; D006207:Half-Life; D009792:Oceans and Seas; D018570:Risk Assessment; D013997:Time Factors; D014835:Volatilization; D014867:Water; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
D014874:Water Pollutants, Chemical; D014867:Water