Organochlorine compounds in soils and sediments of the mountain Andean Lakes.

Semi-volatile organochlorine compounds (OC) were analyzed in remote Andean soils and lake sediments. The sampling sites covered a wide latitudinal gradient from 18 degrees S to 46 degrees S along Chile and an altitudinal gradient (10-4500 m). The concentrations were in the order of background levels, involving absence of major pollution sources in the high mountain areas. Significant correlations were found between log-transformed concentrations of hexachlorobenzene, alpha- and gamma-hexachlorocyclohexane in soils and total organic content (TOC). In addition, TOC-normalized concentrations of the most volatile OC showed a significant linear dependence with air temperature. This good agreement points to temperature as a significant factor for the retention of long range transported OC in remote ecosystems such as the Andean mountains, although other variables should not be totally excluded. The highest concentrations of OCs were achieved in the sites located at highest altitude and lowest temperature of the dataset.

Temperature dependence of the distribution of organochlorine compounds in the mosses of the Andean mountains.

Organochlorine compounds (OC), namely pentachlorobenzene, hexachlorobenzene, hexachlorocyclohexanes, polychlorobiphenyls (PCBs), and DDTs, have been studied in mosses distributed over three altitude gradients of the Andean mountains in Chile at 18 degrees S (3200-4500 m above sea level), 37 degrees S (345-1330 m), and 45 degrees S (10-700 m). The observed concentrations range among the lowestvalues ever reported in remote sites, but they are still higher than those found in previously studied Antarctic areas. The log transformed OC concentrations show a significant linear dependence from reciprocal of temperature independently of the origin of the compounds, e.g. industrial, agricultural, or mixed. In the case of the more volatile OC these correlations involve variance percentages higher than 50%. This good agreement gives further ground to temperature as the driving factor for the retention of long-range transported OC in remote ecosystems, including those in the southern hemisphere such as the Andean mountains. In the context of the samples selected for study, the temperature dependences in the areas of similar latitude are related to altitude. Thus, all OC in the highest altitude gradient (18 degrees S) and most compounds in the other two profiles (37 degrees S and 45 degrees S) exhibit higher concentrations with decreasing annual average temperature and thus increase with elevation above sea level. However, theoretical examination of the exponential equation relating OC concentrations to reciprocal of absolute temperatures shows that besides the temperature differences between highest and lowest elevation, the most relevant factor determining the OC concentration gradients is the lowest temperature value of each altitudinal series. That is, the point at highest elevation.