Adianto P. Simamora, Jakarta – Nine of Indonesia's main rivers are contaminated with dangerously high levels of carbon dioxide (CO2) due to the dumping of industrial chemicals and agriculture and domestic waste, a four-year study shows.

There is a far higher percentage of CO2 in the nine rivers than in the atmosphere, the survey shows.

"The rivers are far more polluted than the atmosphere," said Elvin Alrian, director of the climate change and air quality unit at the Meteorology, Climatology and Geophysics Agency, during an international workshop on climate change Monday.

The survey, conducted from 2005 to 2009, studied nine rivers: Cisadane in Tangerang; Citanduy and Serayu in Cilacap; Bengawan Solo in Gresik; Cimanuk in Indramayu; Citarum in Bekasi; Brantas in Surabaya; Ciujung in Cibinong and Musi in Palembang.

The study reveals that carbon emission levels in the river Brantas stand at about 9,000 parts per million (ppm) and emissions are at 7,500 ppm in the river Musi. Carbon levels in the atmosphere are estimated at 387 ppm, the study says.

Elvin said it was possible the rivers would not be able to hold higher levels of carbon, meaning they would begin to emit CO2 into the atmosphere.

"But we can't predict yet how much of the dissolved emissions in rivers evaporates into the atmosphere," he said. "However, we believe that most of the carbon in the rivers is flushed into the ocean."

Polluted rivers that emit CO2 would undermine the government's move to promote its surrounding seas as a giant carbon sink.

Elvin, who is one of Indonesia's negotiators in the climate talks, said that the major contributor to increased carbon levels in rivers was human waste.

Indonesia is the world's third-largest carbon emitter, due in large part to carbon emissions from forest fires and deforestation.

The Intergovernmental Panel on Climate Change has yet to include river emissions in its calculations of global greenhouse gas emissions.

Activists from the People's Coalition for Justice in Fisheries have warned the government not to promote Indonesian waters as a carbon sink. A 2009 study by the United Nations Environment Programme shows that oceans absorb about one-quarter of all CO2 emitted into the atmosphere from the burning of fossil fuels, deforestation and other human activities.

However, absorption of atmospheric CO2 has increased the acidity of the world's oceans. The study shows that ocean acidity levels could double by 2050, leading to wide-scale coral bleaching, and diminishing oceanic fish feeding grounds.