Soluble Organic Nitrogen in Airborne Particles and Rains of La Gran Sabana, Canaima National Park, Venezuela.
Milexi
Pacheco, Instituto venezolano de Investigaciones cientificas, IVIC, mipachec@ivic.ve
(Presenting)
Loreto
Donoso, Instituto venezolano de Investigaciones cientificas, IVIC, edonoso@ivic.ve
Eugenio
Sanhueza, Instituto venezolano de Investigaciones cientificas, IVIC, esanhuez@ivic.ve
Soluble organic forms of nitrogen are widespread in the atmosphere and their deposition may constitute a substantive input of atmospheric N to terrestrial and aquatic ecosystems. However, only few studies on soluble organic nitrogen (SON) have been made in remote regions. SON was measured in airborne particles and in rainwater at La Gran Sabana, Canaima National Park, a remote place in Venezuela located nearby the northern border of the Amazon Forest. Precipitation was sampled by rain gauges and preserved with chloroform. Suspended particles were collected with a Hi Vol sampler and nitrogen soluble compounds extracted with deionized water using an ultrasonic method. Total soluble nitrogen (TSN) was analyzed in the water solution (particles and rain) as nitrate by the cadmium reduction method after wet chemical oxidation with persulfate. NH4+ and NO3-, were determined with a selective electrode and ion chromatography, respectively. SON was determined subtracting the inorganic fraction from TSN. In rainwater, the average volume weighted SON was 24 uM (as N), which represents ~90% of TSN. In aerosols ~60% of TSN is in the form of SON. In general, the low levels of the inorganic fraction are responsible for the high contribution of SON to the TSN in this pristine region. Therefore, SON is an important component of the nitrogen budget and its inclusion significantly increases the N nutrient input to the soil-vegetation reservoirs of La Gran Sabana ecosystems.