The record of global pollution in polar snow and ice

Global Atmospheric Transport and Source-Receptor Relationships for Arsenic

Arsenic and many of its compounds are toxic pollutants in the global environment. They can be transported long distances in the atmosphere before depositing to the surface, but the global source-receptor relationships between various regions have not yet been assessed. We develop the first global model for atmospheric arsenic to better understand and quantify its intercontinental transport. Our model reproduces the observed arsenic concentrations in surface air over various sites around the world. Arsenic emissions from Asia and South America are found to be the dominant sources for atmospheric arsenic in the Northern and Southern Hemispheres, respectively. Asian emissions are found to contribute 39% and 38% of the total arsenic deposition over the Arctic and Northern America, respectively. Another 14% of the arsenic deposition to the Arctic region is attributed to European emissions. Our results indicate that the reduction of anthropogenic arsenic emissions in Asia and South America can significantly reduce arsenic pollution not only locally but also globally.

Ice Sheets and the Anthropocene

Ice could play a role in identifying and defining the Anthropocene. The recurrence of northern hemisphere glaciation and the stability of the Greenland Ice Sheet are both potentially vulnerable to human impact on the environment. However, only a very long hiatus in either would be unusual in the context of the Quaternary Period, requiring the definition of a geological boundary. Human influence can clearly be discerned in several ice-core measurements. These include a sharp boundary in radioactivity due to atmospheric nuclear testing; increases, unprecedented at least in the Holocene, in Greenland concentrations of sulphate, nitrate and metals such as lead; the appearance in ice-core air bubbles of previously undetectable compounds such as SF6; and the rise, unprecedented in the last 800 ka, in concentrations of carbon dioxide and methane. Some combination of these changes could be used by future generations to clearly identify the onset of a new epoch defined at a particular calendar date. However, it is not yet clear what the character of the fully developed Anthropocene will be, and it might be wise to let future generations decide, with hindsight, when the Anthropocene started, acknowledging only that we are in the transition towards it.

Rapid release and changing sources of Pb in a mountainous watershed during extreme rainfall events

Although atmospheric Pb is known to accumulate in forest soils over time, little is known about the hydrologic Pb export from mountain forest soils. Short-term changes in Pb release and its sources during monsoon rainfall events were investigated in a mountainous watershed in the northern extreme of South Korea by combining intensive storm sampling with measurements of Pb concentrations and isotope ratios in soils and size-fractionated sediments. Biweekly monitoring of forest and agricultural streams showed relatively low dissolved Pb concentrations compared to those found in precipitation. Particulate Pb concentrations in both streams were higher than the dissolved concentrations and increased rapidly during rainfall events. Particulate Pb concentrations were substantially higher in the agricultural stream; the highest concentrations were associated with silt-size sediment followed by sand. A comparison of (206)Pb/(207)Pb and (208)Pb/(206)Pb among sediment fractions and source soils indicated that major sources for silt- and sand-associated Pb in the agricultural stream change between streambank and cropland soils, whereas Pb in the forest stream is primarily derived from forest floors. The results suggest that Pb isotopes can be efficiently applied to tracing short-term changes in sediment and Pb sources and that extreme rainfall events can significantly increase Pb mobilization from erosion-prone mountain soils.

Tracing the anthropogenic lead sources in coastal sediments of SE-pacific (36 degrees Lat. S) using stable lead isotopes

This study evaluates the main sources of antropogenic Pb in one of the most industrialized centers of the southern Chilean coast (36 degrees S). Stable lead isotopes ((206)Pb/(207)Pb, (208)Pb/(207)Pb) were used to trace main Pb sources to coastal sediments, considering the suspended particulate matter (SPM) from marine (traps), continental (rivers) and industrial effluents, sediments and leaded gasoline samples. The atmospheric input was evaluated through natural collectors; i.e. Raqui-Tubul salt marsh. Results show that marine samples lie on a trend between industrial effluents ( approximately 1.16, 2.44) and natural sources (1.20, 2.50), not related to gasoline consumption. Salt marsh sediments show comparable isotopic composition to marine samples, suggesting the importance of the atmospheric input in the coastal sediments, not related to the leaded gasoline composition either. The continental input (1.18, 2.48) is highly influenced by precipitation, being difficult to separate both sources (atmosphere and continental runoff), showing also similar isotopic ratio to marine sediments. The signal of industrial emissions is masked with the introduction of Pb with higher isotopic ratios, compared to the values observed in the material collected from traps (SPM approximately 1.19, 2.48). The contribution of more radiogenic Pb by the upwelling is suggested.

Genetic manipulations of microorganisms for the degradation of hexachlorocyclohexane

Hexachlorocyclohexane (HCH) is an organochlorine insecticide which has been banned in technologically advanced countries. However, it is still in use in tropical countries for mosquito control and thus new areas continue to be contaminated. Anaerobic degradation of HCH isomers have been well documented but until recently there have been only a few reports on aerobic microbial degradation of HCH isomers. The isolation of these microbes made it possible to design experiments for the cloning of the catabolic genes responsible for degradation. We review the microbial degradation of HCH isomers coupled with the genetic manipulations of the catabolic genes. The first part discusses the persistence of residues in the environment and microbial degradation while the second part gives an account of the genetic manipulations of catabolic genes involved in the degradation.

Determination of PAH in atmospheric particulates in the area of the Italian base in Antarctica: report on monitoring activities during the last three scientific expeditions

Concentrations of polycyclic aromatic hydrocarbons (PAH) in atmospheric particulates have been determined in the frame of the control activities for environmental protection during the VI (1990-1991), VII (1991-1992) and VIII (1992-1993) Italian expeditions in Antarctica. Samples were collected at the four cardinal points at about 200 m from the central area of the Italian scientific base. Data show low levels of the individual PAH (95% in the range 1-50 pg m(-3)) confirming the absence, up to now, of significant contamination from the base. These results could be used as a reference for the assessment of the air pollution due to combustion sources present in the base. Any possible variation in the base's activities in the future should be analysed and evaluated with respect to these findings.

Arctic Research in the National Interest

The Arctic Research and Policy Act of 1984 was designed to advance arctic research in the national interest. Some of the research fields that require attention are weather and climate; national defense; renewable and nonrenewable resources; transportation; communications and spacedisturbance effects; environmental protection; health, culture, and socioeconomics; and international cooperation. A research framework recommended by the Arctic Research Commission includes, in order of priority, integrated investigations to understand: (i) the Arctic Ocean (including the marginal seas, sea ice, and seabed) and how the ocean and atmosphere operate as coupled components of the arctic system; (ii) the coupled atmosphere and land components and how their interaction governs the terrestrial environment; and (iii) the high-latitude upper atmosphere and its extension into the magnetosphere with emphasis on predicting and mitigating effects on communications and defense systems. A separate recommendation is for high priority research to resolve the major health, behavioral, and cultural problems related to the arctic environment. Recommendations are also made concerning support services and management.