First report of phytoliths in the air of Argentina

Abstract

A first analysis of airborne phytoliths was carried out in Mar del Plata, Argentina. Its primary aims were to characterize the phytolith morphotypes present in the atmosphere, to quantify their abundance and to detect whether seasonal variations exist throughout the year. The standard method was used for monitoring airborne particulate matter applying a Hirst-type suction bioaerosol sampler. The mean daily phytoliths concentrations (p/m3) were calculated for eight selected days from the driest year, 1993, bearing in mind that its atmospheric conditions could favour the presence of biomineralizations in the air. The amount of phytoliths reached was of 1,543. It was composed of 61% isolated and 1% articulated types. The rest were unknown or unidentified phytoliths (38%). The most abundant morphotypes (72.1% of those identified) were elongates, followed by rondels (16.1%) already described for Poaceae subfamilies, such as Pooideae and Stipoideae. Finally, trapeziform and point shaped were identified with 3.8 and 3.4%, respectively. A lower abundance of silica particles was detected on high wind speed days from the south (sea coast) and under wetter conditions. Maximum phytoliths concentrations were recorded in winter when pasture burning is carried out alongside ploughing; this also coincides with the period in which soils were not covered by vegetation. These results shed light on the importance of considering the potential ways of phytoliths dispersion and the factors that could be affecting their aerial transport, especially when they are applied to the interpretation of paleovegetation from phytolith fossil records.