Roaring forties: An analysis of a decadal series of data of dust in Northern Patagonia

摘要

The objective of this study is to analyze the daily variation of aeolian 'dust in Puerto Madryn, Patagonia,, Argentina, based on a series of data of more than 11 years (from December 2004 to April 2016). In order to accomplish it, atmospheric dust was collected by means of a high volume sampler placed at the El Tehuelche airport located at 10 km westward from Puerto Madryn. A correlation between aeolian dust and wind intensity was studied. An elemental and mineral composition and granulometry analyses of dust particles were performed. Monthly aeolian dust concentration ranged between mu g*m-3 and 2700ug*m-3. Volcanic eruptions ocurred throughout the study. The effects of volcanoes activities were evident and signifincatly increased the concentration of dust by the massive emission of ashes into the atmosphere. Thus, the mean monthly variation of dust concentration was analyzed considering the full data set and a sub-set of those years without volcanic eruptions. In the first case, the variation did not presents a pattern of variation, whereas, in the second case, a clear seassonal pattern was observed. Minimum dust concentration was recorded in Winter (20 mu g*m-3) and maximum in Summer (60 mu g*m-3). The correlation between dust concentration and wind intensity was lower than 0.5, suggesting that other factors (e.g. soil moisture and vegetation coverage) may play an important role on the suspension of mineral particles in the study region. The elemental composition was characterized by a high proportion of Si and 0, whereas Fe, S, K, Mg, and P were present in a lower proportion. Clasts were mostly silicates such as quartz, horblende, and plagioclase. The granulometry was studied using a subset of 10 filters. The mean size of dust particles was 11 pm and ranged form 0.5 pm to 120 pm. These results suggest that dust transported from Patagonia to the Southern Atlantic Ocean is permanent and highly variable and may represent and important input of Fe into the sea.