Revista Chilena de Historia Natural 75 (1): 233-243, 2002
RESEARCH ARTICLE
Atmospheric deposition of nitrogen in a transect from the Central Valley to Cordillera de Los
Andes, south-central Chile
Agricultural-livestock activities in south-central Chile, could result in elevated emissions of
inorganic N (mainly NH<sub>3</sub>) compounds into the atmosphere. Ammonia can be transported via air currents and
deposited on the vegetation and soil. The present study evaluates the atmospheric deposition of nitrogen compounds
(NO<sub>3</sub><sup>-</sup> y NH<sub>4</sub><sup>+</sup>) in the precipitation, in an
altitudinal transect of 66 km long, from the vicinity of Osorno (40º 35’ S, 72º 57’ W, 55 m of altitude) to Puyehue National Park,
Cordillera de Los Andes (40º 46’ S, 72º 11’ W, 1,120 m of altitude). In seven sites, from June-1999 to May-2000, precipitation was
recorded and water samples were collected monthly, for to determine pH, conductivity and NO<sub>3</sub><sup>-
</sup> and NH<sub>4</sub><sup>+</sup> concentrations. Annual precipitation increased from 1,103 mm
near Osorno to 6,799 mm in Antillanca, Puyehue National Park. Annual mean values of pH showed little change from 6.3 in the central
valley to 5.8 in the Cordillera de Los Andes. Conductivity showed the maximum values near Osorno (22.9 µS cm<sup>-
1</sup>), intermediate values in transitional sites, and 11.3 µS cm<sup>-1</sup> in the Cordillera de Los Andes. The
annual mean concentrations of NO<sub>3</sub>- N changed between 52.3 µg L<sup>-1</sup> in the agriculture-
cattle area and 6.9 µg L<sup>-1</sup> in temperate rainforests in Puyehue National Park.
NH<sub>4</sub><sup>+</sup> concentrations changed between 699.4 µg L<sup>-1</sup> in the Osorno
sector to 37.8 µg L<sup>-1</sup> in Cordillera de Los Andes. Inorganic-N values have a marked seasonal variation in the
agricultural region with the maximum values in spring-summer and minimum in wintertime. Annual rates of atmospheric deposition of
NO<sub>3</sub>-N fluctuated between 0.53 and 0.57 kg ha<sup>-1</sup> yr<sup>-1</sup>, and the
NH<sub>4</sub>-N between 6.4 and 2.8 kg ha<sup>-1</sup> yr<sup>-1</sup> for the agricultural region
of Osorno and Puyehue National Park, respectively. These results are discussed in relation to the potential environmental effects of the
increasing atmospheric deposition of nitrogen on the acidification and eutrophication of the soil and groundwater and runoff in the
central valley of south-central Chile.
Key words:
atmospheric
deposition, NO<sub>3</sub><sup>-</sup>, NH<sub>4</sub><sup>+</sup> , water chemistry, agriculture-cattle, temperate rainforest, Nothofagus
