In this paper we present a new global multimedia fate model that considers the influence of temperature on the environmental transport, degradation, and partitioning of persistent organic pollutants. The model consists of a variable number of latitudinal zones with specific annual temperature courses; each zone contains soil, oceanic surface water, and tropospheric air. The chemicals' degradation rates and Henry's law constants (H) are implemented as functions of temperature and the concentrations in the soil, water, and air compartments of each latitudinal zone are calculated as functions of time. The resulting temporal and spatial concentration patterns are characterized by persistence and spatial range. Model calculations are carried out for tetrachloromethane, R-hexachlorocyclohexane (R-HCH), and mirex, and the specific distribution patterns of these three chemicals are discussed. The model results show that the soil and water concentrations of the polar zones are strongly sensitive to changes of the latitudinal gradient of H and of washout ratios, adsorption to aerosol particles, and deposition rates.
It is known from field and modeling studies that snowfall events and the presence of snow covering soil and vegetation affect the environmental distribution of chemicals.Therefore, it is essential to understand how chemicals interact with snow and ice and how they are transported to cold regions. The latter is especially important in the context of today's chemicals politics aiming to reduce trans-boundary pollution and to protect remote regions against chemical contamination. Persistent organic pollutants and other semi-volatile organic compounds (SOCs) that were measured in snow and ice samples include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs) as well as current-use pesticides such as dacthal, chlorpyrifos and endosulfan and historic-use pesticides including DDT, hexachlorobenzene (HCB) and α-hexachlorocyclohexane (α-HCH).Multi-media fate and transport models are a useful tool to investigate mechanisms and pathways of long-range transport (LRT) and environmental distribution of chemicals.They can thus be applied to investigate the fate of chemicals in snow and ice and the LRT of chemicals to cold environments. But so far, none of the existing global multi-media box models includes snow or ice compartments. In this work, we present a description of snow and ice implemented in the global multi-media model CliMoChem (Climate Zone Model for Chemicals). Processes describing the removal of chemicals from air to snow and surface ice include deposition of chemicals by wet and dry particle deposition, vapor scavenging by snow and dry gaseous deposition. Deposited chemicals are removed from snow and surface ice by re-volatilization, melt water runoff from surface ice or snow to soil and water, transfer from surface ice to deep ice and degradation in snow or surface ice. Investigated compounds include HCB, PCB28, PCB153, PCB180, PBDE47, PBDE209, α-HCH and dacthal.For snow, the relative importance of each deposition pathway depends on the chemical's affinity for snowflakes and particles in air whereas the chemical's affinity for bulk snow and melt water as well as the average air temperature are the main parameters influencing the removal pathways from snow. Investigated chemicals are mainly Abstract deposited to ice by vapor scavenging by snow or by particle deposition; transfer to deep
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