The Impact of African Dust on PM10 Air Quality in the Caribbean Basin

Abstract:

Decades of aerosol measurements on Barbados and Miami have yielded a broad picture of African mineral dust transport to the Caribbean Basin. These measurements show that in summer the aerosol mass is often dominated by dust. At such times over 90% of the dust mass is comprised of particles less than 10 µm aerodynamic diameter and thus fits the EPA criteria for PM₁₀. A number of sites in the Caribbean monitor PM₁₀ using the same instrumentation commonly deployed in European and United States networks. By comparing data from individual islands that have multiple monitoring sites (e.g., Puerto Rico, Martinique, Guadeloupe), it is shown that during dust events PM₁₀ concentrations track very closely and that local sources have a minor impact on PM₁₀ above about 15 to 20 µg m^-3. Moreover the PM₁₀ measurements are coherent with the movement of dust clouds over the islands as observed by satellites. In this way dust movement can be tracked at PM₁₀ sites along the Gulf and southeast coasts of the United States. To assess the specific impact of African dust on PM₁₀ in the region, I compare the daily records of dust measurements at Miami and Barbados with concurrent measurements made at proximate PM₁₀ sites. I then use these relationships and the long term dust measurements at Barbados and Miami to assess the long-term variability of PM₁₀ across the region. At Barbados the record goes back 50 years and provides a basis of assessing the effects of climate variability on PM₁₀ transport. This study shows that there is great variability on scales ranging from daily to decadal. The impact of the droughts in the 1970s and 1980s was particularly significant. Across the Caribbean, the rates of exceedances of the WHO PM₁₀ guideline is comparable to those observed in many major urban areas in Europe and the US. The dominance of dust in large PM₁₀ events and the absence of major pollution sources on many islands offers the opportunity to study the health impacts of desert dust in local populations with a minimal affects from confounding aerosol sources.