According to the International Panel on Climate Change the greatest uncertainties in climate change is the role of particulates (aerosols) in the atmosphere. Aerosols effect the solar radiation coming in and IR out of the atmosphere in a fashion that is inadequately understood. A major weakness in quantifying the role of aerosols is that their chemical composition determines these properties and is difficult to measure appropriately. The chemical properties of their surfaces will determine how particles transform during their transport which may be hemispheric. These chemical alterations are extraordinarily difficult to determine by conventional concentration measurements. Furthermore, resolving the source of aerosols is another facet that is difficult to assign.

   In this project, we used a new tracer of these processes, multi stable isotope ratio measurements. The composition and alteration of isotope ratios coupled with knowledge of the quantum chemical control of them allows chemical alterations to be determined in a completely unique way. In addition, source recognition may be achieved.

   Two of the most abundant and important atmospheric aerosols are nitrate and sulfate. They intersect with climate, human health, agriculture, and materials degradation, hence understanding these features has a very significant societal component. Their transport is also important because the issues become international and mediation complex. Any enhancement in understanding these properties may significantly impact the ability to make political and social decisions, as well as advance basic understanding of global atmospheric chemical science.

In a previously funded NSF grant, this lab excavated a snow pit at the South Pole. This type of sampling as compared to conventional coring provides a high time resolution (6 month vs. years) and we were able to examine a 20 year record of aerosol sulfate for all oxygen and sulfur isotopes that was transported to the South Pole. This inclusion of all isotopes had never been done anywhere, and the time evolution was a key component.

The basis for the proposal was to determine how the sulfate aerosols were created via oxidation and, to determine if we may evaluate global properties of oxidation processes as they are an important component of the Earths totals chemical system. The observations far exceeded our expectations. We were able to establish our chronology quite precisely as we were able to recognize the Pinatubo and Cerro Hudson volcanic debris and their associated perturbation of the upper atmospheric (stratospheric) perturbation. This gave us a benchmark for both time for hemispheric transport and magnitude because the output from these volcanic events is well characterized. What we also found and had not been noted before, was that during El Nino years, there exists a conveyor belt arising in the equatorial region of sulfur species that impinge on the ozone chemistry of the equatorial region and are then transported to the South Pole (Fig. 1a and b). This correlated well with the ozone measurements made be various satellites and we now have a means to measure sources at the equatorial region, define their chemical change over distance, and the time scale.

   A greater surprise was that in the sulfur record, following the largest El Nino in 200 years (1998/1999) we found a massive stratospheric transport of sulfur that exceeded the size of effect produced by the Pinatubo eruption. We have resolved that this derives from the massive wildfires that occurred in Indonesia and South America. The wildfires injected massive quantities of material to the stratosphere where the photochemical reaction of sulfur dioxide and subsequent reaction with ozone occurred along its transit to the South Pole. This process had not been recognized and it fully exploited the new isotope ...

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