Emissions, fate and transport of persistent organic pollutants to the Arctic in a changing global climate.

Climate change is expected to alter patterns of human economic activity and the associated emissions of chemicals, and also to affect the transport and fate of persistent organic pollutants (POPs). Here, we use a global-scale multimedia chemical fate model to analyze and quantify the impact of climate change on emissions and fate of POPs, and their transport to the Arctic. First, climate change effects under the SRES-A2 scenario are illustrated using case-studies for two well-characterized POPs, PCB153, and α-HCH. Then, we model the combined impact of altered emission patterns and climatic conditions on environmental concentrations of potential future-use substances with a broad range of chemical properties. Starting from base-case generic emission scenarios, we postulate changes in emission patterns that may occur in response to climate change: enhanced usage of industrial chemicals in an ice-free Arctic, and intensified application of agrochemicals due to higher crop production and poleward expansion of potential arable land. We find both increases and decreases in concentrations of POP-like chemicals in the Arctic in the climate change scenario compared to the base-case climate. During the phase of ongoing primary emissions, modeled increases in Arctic contamination are up to a factor of 2 in air and water, and are driven mostly by changes in emission patterns. After phase-out, increases are up to a factor of 2 in air and 4 in water, and are mostly attributable to changes in transport and fate of chemicals under the climate change scenario.

Comparative assessment of the global fate of α- and ß-hexachlorocyclohexane before and after phase-out.

Technical hexachlorocyclohexane (HCH) was one of the most widely used pesticides during the 20th century. Although production and use were phased-out during the 1990s, two of its major components, α- and ß-HCH, are still ubiquitous in the environment. Here, we have collected and analyzed data on concentrations of α- and ß-HCH in the atmosphere and oceans, including spatial and temporal trends and seasonalities. We apply a global fate and transport model to both isomers over the period 1950 to 2050 to rationalize current levels and trends at remote locations with estimated emissions and to forecast into the near future. Our model results indicate that secondary emissions from soils and oceans are currently controlling the observed rates of decline in the atmosphere. ß-HCH is declining more slowly than α-HCH due to its higher persistence, and we hypothesize that it will eventually become the predominant isomer of HCH in the environment. The model reproduces over 70% of measured concentrations of α-HCH in air and ocean water within factors of 3 and 5, respectively, and over 70% of measured concentrations of ß-HCH within factors of 8 and 20, respectively. The model results are only weakly sensitive to climate change-induced trends in Arctic sea-ice cover and temperature.

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.

Ten years after entry into force of the Stockholm Convention: What do air monitoring data tell about its effectiveness?

More than a decade ago, the Stockholm Convention on Persistent Organic Pollutants (POPs), one of the multilateral environmental agreements administered by the United Nations Environment Programme (UNEP), entered into force. The objective of this Convention is to protect human health and the environment by controlling the releases of POPs. According to its Article 16, the effectiveness of the Stockholm Convention shall be evaluated using comparable monitoring data on the presence of POPs as well as their regional and global environmental transport. Here, we present a time series analysis on atmospheric POP concentrations from 15 monitoring stations in North America and Europe that provide long-term data and have started operations between 1990 and 2003. We systematically searched for temporal trends and significant structural changes in temporal trends that might result from the provisions of the Stockholm Convention. We find that such structural changes do occur, but they are related mostly to effects of national regulations enforced prior to the implementation of the Stockholm Convention, rather than to the enforcement of the provisions laid out in the Convention. One example is that concentrations of polychlorinated biphenyls, many of which started to decrease rapidly during the 1990s. Also effects of chemical transport and fate, for instance the re-volatilization of POPs from secondary sources, are thought to be a cause of some of the observed structural changes. We conclude that a decade of air monitoring data has not been sufficient for detecting general and statistically significant effects of the Stockholm Convention. Based on these lessons, we present recommendations for the future operation of existing monitoring programs and advocate for a stricter enforcement of the provisions of the Stockholm Convention, in the current absence of proof for its effectiveness.

BETR global--a geographically-explicit global-scale multimedia contaminant fate model.

We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15°×15° grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5).

Vehicle traffic as a source of particulate polycyclic aromatic hydrocarbon exposure in the Mexico City metropolitan area.

Surface properties of aerosols in the Mexico City metropolitan area have been measured in a variety of exposure scenarios related to vehicle emissions in 2002, using continuous, real-time instruments. The objective of these experiments is to describe ambient and occupational particulate polycyclic aromatic hydrocarbon (PAH) concentrations associated with vehicular traffic and facilities using diesel vehicles. Median total particulate PAH concentrations along Mexico City's roadways range from 60 to 910 ng m(-3), averaged over a minimum of 1 h. These levels are approximately 5 times higher than concentrations measured in the United States and among the highest measured ambient values reported in the literature. The ratio of particulate PAH concentration to aerosol active surface area is much higher along roadways and in other areas of fresh vehicle emissions, compared to ratios measured at sites influenced more by aged emissions or noncombustion sources. For particles freshly emitted by vehicles, PAH and elemental carbon (EC) concentrations are correlated because they both originate during the combustion process. Comparison of PAH versus EC and active surface area concentrations at different locations suggests that surface PAH concentrations may diminish with particle aging. These results indicate that exposure to vehicle-related PAH emissions on Mexico City's roadways may present an important public health risk.