A study on the concentration, distribution, and behavior of metals in atmospheric particulate matter over the North Pacific Ocean by using inductively coupled plasma mass spectrometry equipped with laser ablation

The concentrations and distribution of 11 metal elements (Al, Ti, V, Mn, Ni, Zn, As, Se, Cd, Sb, and Pb) in marine atmospheric particulate matter collected daily over the North Pacific Ocean during the 14 separate cruises of M/V Skaugran from Japan to the west coast of the American continent and back to Japan from March 1995 to October 1996 have been investigated in order to clarify their behavior. A total of 223 samples were collected and analyzed by laser ablation inductively coupled plasma mass spectrometry (LA/ICP-MS). For crustal elements such as Al and Mn, their concentrations decreased from the western to central and then only slightly increased in the eastern North Pacific Ocean. The concentrations of anthropogenically derived elements such as Zn and Pb were also significantly higher in the western than in the central and eastern North Pacific Ocean. Both crustal and anthropogenic elements displayed high concentrations in the commonly known dust season (March to May) and low concentrations in the summer (June to August). In winter (November to December), however, only anthropogenic elements showed significantly high concentrations. The high concentrations for crustal elements in the dust season are suggested as resulting from the input of mineral particulate matter transported from the Asian continent by westerly winds. This input does not occur in winter because the land surface is frozen. The westerly winds also distribute anthropogenic elements to the North Pacific Ocean. However, in summer the westerly wind is replaced by the oceanic wind that dilutes both crustal and anthropogenic elements in the marine atmosphere, and therefore their concentrations were significantly lower in summer.