Organic pollutants have been on the decline in most natural areas in recent years, due to stricter regulations and improvements to products including the contaminants, such as certain pesticides. But a new study in the journal Environmental Science and Technology shows that these pollutants are showing a spike in some natural lakes, regardless of their tighter restrictions in the marketplace.
The answer to this mysterious reappearance, says first author Christian Bogdal of ETH Zurich, is the melting of glaciers that feed into these lakes. He and his coauthors studied Lake Oberaar, a glacier-fed lake in the Bernese Alps of Switzerland. They found that contamination was low in the 1980s and 1990s, but since the late 1990s, flow of pollutants into the lake has increased drastically. Levels of organochlorines — commonly found in pesticides and PVC piping — flowing into the lake at present are similar to or higher than peak levels in the 1960s and 1970s, before regulations took effect. The pollutants are preserved in the glaciers over time and redeposited upon melting.
The authors state that the 1500 glaciers in the Swiss Alps have reduced by 12 percent since 1999. If this decrease continues, they write, there could be “dire environmental impacts” to mountainous areas.
Bogdal, C., Schmid, P., Zennegg, M., Anselmetti, F., Scheringer, M., & Hungerbühler, K. (2009). Blast from the Past: Melting Glaciers as a Relevant Source for Persistent Organic Pollutants Environmental Science & Technology DOI: 10.1021/es901628x