The impact of organochlorines cycling in the cryosphere on their global distribution and fate--1. Sea ice

Polychlorinated biphenyls (PCBs) as sentinels for the elucidation of Arctic environmental change processes: a comprehensive review combined with ArcRisk project results

Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropogenic influences on Arctic environmental change. We present an overview of studies on PCBs in the Arctic and combine these with the findings from ArcRisk-a major European Union-funded project aimed at examining the effects of climate change on the transport of contaminants to and their behaviour of in the Arctic-to provide a case study on the behaviour and impact of PCBs over time in the Arctic. PCBs in the Arctic have shown declining trends in the environment over the last few decades. Atmospheric long-range transport from secondary and primary sources is the major input of PCBs to the Arctic region. Modelling of the atmospheric PCB composition and behaviour showed some increases in environmental concentrations in a warmer Arctic, but the general decline in PCB levels is still the most prominent feature. 'Within-Arctic' processing of PCBs will be affected by climate change-related processes such as changing wet deposition. These in turn will influence biological exposure and uptake of PCBs. The pan-Arctic rivers draining large Arctic/sub-Arctic catchments provide a significant source of PCBs to the Arctic Ocean, although changes in hydrology/sediment transport combined with a changing marine environment remain areas of uncertainty with regard to PCB fate. Indirect effects of climate change on human exposure, such as a changing diet will influence and possibly reduce PCB exposure for indigenous peoples. Body burdens of PCBs have declined since the 1980s and are predicted to decline further.

A numerical study on the seasonal variability of polychlorinated biphenyls from the atmosphere in the East China Sea

A three-dimensional/high-resolution transport model for persistent organic pollutants (POPs) has been developed for the East China Sea (ECS). The POPs model has four compartments (gaseous, dissolved, phytoplankton-bound, and detritus-bound phases) and includes processes for diffusive air-water exchange, phytoplankton uptake/depuration to POPs, decomposition of dissolved phase, vertical sinking of phytoplankton, detritus production by phytoplankton mortality, and vertical sinking and decomposition of detritus. The POPs model is coupled with an ocean circulation model that can reproduce the seasonal variation in physical variables to represent the advection and diffusion of POPs. We applied the POPs model to the polychlorinated biphenyl congener 153 (PCB 153) from the atmosphere and examined the behavior of PCB 153 in the ocean. The model showed a remarkable seasonal variability of PCB 153. Concentrations in the dissolved and particulate phases are high in winter (January-March) and low in summer (July-September). In coastal regions, where chlorophyll a concentration is high, horizontal and vertical distributions in the dissolved and particulate PCB 153 concentrations are strongly affected by phytoplankton uptake. The sensitivity experiments on the dynamics of PCB 153 suggested that a change of Henry's law constant associated with water temperature is the major factor controlling the seasonal variability of PCB 153. The model-based yearly mass balance of PCB 153 in the ECS indicated that most of the atmospheric input (35.5 kg year(-1)) is removed by the horizontal advection outside the ECS (19.0 kg year(-1)) and accumulates to the sea bottom by vertical sinking (15.7 kg year(-1)). For comparison with PCB 153, we also conducted simulations for PCB 52, 101, and 180. The seasonal variations are similar to that of PCB 153. The mass balance of PCB 52 that has short half-life time and less hydrophobic property shows the different results compared with PCB 101, 153, and 180.

The impact of organochlorines cycling in the cryosphere on global distributions and fate--2. Land ice and temporary snow cover

Global fate and transport of γ-HCH and DDT was studied using a global multicompartment chemistry-transport model, MPI-MCTM, with and without inclusion of land ice (in Antarctica and Greenland) or snow cover (dynamic). MPI-MCTM is based on coupled ocean and atmosphere general circulation models. After a decade of simulation 4.2% γ-HCH and 2.3% DDT are stored in land ice and snow. Neglection of land ice and snow in modelling would underestimate the total environmental residence time, τ(ov), of γ-HCH and overestimate τ(ov) for DDT, both on the order of 1% and depending on actual compartmental distribution. Volatilisation of DDT from boreal, seasonally snow covered land is enhanced throughout the year, while volatilisation of γ-HCH is only enhanced during the snow-free season. Including land ice and snow cover in modelling matters in particular for the Arctic, where higher burdens are predicted to be stored.