| Popis: |
A research cruise was conducted in the summer of 1986 by a group of scientist from the U.S.A. and Mexico to investigate air chemistry over the Gulf of Mexico. Chemical, physical, meteorological and oceanographic measurements were carried out to survey temporal and spatial variations of diverse parameters throughout the Gulf. Emphases were placed on air-sea-land exchange of gases and aerosols, natural air quality, transport of anthropogenic air pollution, and acid rain deposition to the Gulf. Although the prevailing winds were easterly from the sea during the cruise, the air was highly polluted with continental aerosols, probably caused by local shifting winds and the oscillation between sea breeze and land breeze. Aerosol number concentrations were measured from 10 5 cm −3 at ports to 10 3 cm −3 in the open Gulf. The average aerosol mass concentration was ∼25 μ g M −3 , consisting of 60% insoluble crustal particles that contained Si, Al, Fe; 30% seasalt particles that contained Na + and Cl − ; and 10% anthropogenic sulfate and nitrate particles. Samples of rain water collected near the coast were acidic (pH ∼4). The concentrations of dimethyl sulfide correlated with bio-particle concentrations in surface seawater and could be a significant precursor of atmospheric SO 4 2− particles. The life cycles of the aerosols in the Gulf, including sources, transport, transformation, and wet and dry deposition are discussed. |
