Anthropogenic influences on the chemical and physical properties of aerosols in the Atlantic subtropical region during July 1994 and July 1995

Elevated pollution levels have been observed at marine boundary layer (MBL) and free troposphere (FT) sites on the island of Tenerife. These have been linked to air mass transport fr om continental areas, with over 40% of the measurements being directly influenced by continental sources. The influence of different meteorological patterns on this transport has been examined. Saharan dust was an important component of the FT aerosol. In the MBL, modification of aerosol light scattering and cloud nucleating properties correlated strongly with enhanced non-sea-salt (nss)SO42 levels, linked to transport from Europe. Regression analysis of cloud condensation nuclei (CCN) concentrations estimated at supersaturation levels of 0.15% and 0.75% gave CCN = 95 nssSO(4)(-2) + 139(0.15%) and CCN =142 nssSO(4)(-2) + 256(0.75%), respectively. Regression analysis of submicron aerosol scattering at 530 nm gave a sulfate mass scattering efficiency value of 6.3 m(2) g(-1). Sea salt was the dominant supermicron scattering species in the MBL. A mass scattering efficiency of 2.9 m(2) g(-1) is estimated for Na+.