Deposition of semi-volatile organochlorine compounds in the free troposphere of the eastern north Atlantic ocean

Deposition samples were taken at a height of 2367 m above sea level (m.a.s. l.) on the Island of Tenerife from May 1999 until July 2000 and analysed fo r 19 polychlorinated biphenyl (PCB) congeners, hexachlorobenzene (HCB), hex achlorocyclohexanes (HCH) and DDTs. This site is located above the inversio n layer, so samples represent background concentrations of the free troposp here. The average deposition fluxes of HCB, total HCH, DDTs and PCBs were 8 6, 400, 110 and 780 ng m(-2) yr(-1), respectively, being lower than those r eported at sea level in continental or marine areas. All compounds are gene rally found in higher abundance in the wet precipitation samples. However, these samples only represent a fraction, e.g. 33%, of the total deposition load. Annual mass balance calculations show that wet precipitation is essen tially responsible for the deposition of the low molecular weight OC wherea s dry deposition accounts for more than 50% of the higher molecular weight PCBs. (C) 2001 Elsevier Science Ltd. All rights reserved.