Megacities and large urban agglomerations in the coastal zone: interactions between atmosphere, land, and marine ecosystems.

Megacities are not only important drivers for socio-economic development but also sources of environmental challenges. Many megacities and large urban agglomerations are located in the coastal zone where land, atmosphere, and ocean meet, posing multiple environmental challenges which we consider here. The atmospheric flow around megacities is complicated by urban heat island effects and topographic flows and sea breezes and influences air pollution and human health. The outflow of polluted air over the ocean perturbs biogeochemical processes. Contaminant inputs can damage downstream coastal zone ecosystem function and resources including fisheries, induce harmful algal blooms and feedback to the atmosphere via marine emissions. The scale of influence of megacities in the coastal zone is hundreds to thousands of kilometers in the atmosphere and tens to hundreds of kilometers in the ocean. We list research needs to further our understanding of coastal megacities with the ultimate aim to improve their environmental management.

An assessment of costs and benefits associated with mercury emission reductions from major anthropogenic sources.

Several measures are available for reducing mercury emissions; however, these measures differ with regard to emission control efficiency, cost, and environmental benefits obtained through their implementation. Measures that include the application of technology, such as technology to remove mercury from flue gases in electric power plants, waste incinerators, and smelters, are rather expensive compared with nontechnological measures. In general, dedicated mercury removal is considerably more expensive than a co-benefit strategy, using air pollution control equipment originally designed to limit emissions of criterion pollutants, such as particulate matter, sulfur dioxide, or oxides of nitrogen. Substantial benefits can be achieved globally by introducing mercury emission reduction measures because they reduce human and wildlife exposure to methyl mercury. Although the reduction potential is greatest with the technological measures, technological and nontechnological solutions for mercury emissions and exposure reductions can be carried out in parallel.

Global Sources and Pathways of Mercury in the Context of Human Health.

This paper reviews information from the existing literature and the EU GMOS (Global Mercury Observation System) project to assess the current scientific knowledge on global mercury releases into the atmosphere, on global atmospheric transport and deposition, and on the linkage between environmental contamination and potential impacts on human health. The review concludes that assessment of global sources and pathways of mercury in the context of human health is important for being able to monitor the effects from implementation of the Minamata Convention targets, although new research is needed on the improvement of emission inventory data, the chemical and physical behaviour of mercury in the atmosphere, the improvement of monitoring network data, predictions of future emissions and speciation, and on the subsequent effects on the environment, human health, as well as the economic costs and benefits of reducing these aspects.

Climate change impacts on environmental and human exposure to mercury in the arctic.

This paper reviews information from the literature and the EU ArcRisk project to assess whether climate change results in an increase or decrease in exposure to mercury (Hg) in the Arctic, and if this in turn will impact the risks related to its harmful effects. It presents the state-of-the art of knowledge on atmospheric mercury emissions from anthropogenic sources worldwide, the long-range transport to the Arctic, and it discusses the likely environmental fate and exposure effects on population groups in the Arctic under climate change conditions. The paper also includes information about the likely synergy effects (co-benefits) current and new climate change polices and mitigation options might have on mercury emissions reductions in the future. The review concludes that reductions of mercury emission from anthropogenic sources worldwide would need to be introduced as soon as possible in order to assure lowering the adverse impact of climate change on human health. Scientific information currently available, however, is not in the position to clearly answer whether climate change will increase or decrease the risk of exposure to mercury in the Arctic. New research should therefore be undertaken to model the relationships between climate change and mercury exposure.