Heavy Metals Still Found in Pagatban River
Thirty years after a copper mine stopped operating and dumping its tailings on the Pagatban River in southern Negros Island, Silliman researchers have found that the water quality of the river has generally improved, but heavy metals (copper and zinc) are still found in the river bottoms at concentrations 200 to 5,000 times higher than acceptable levels, posing an environmental threat.
“Although the general water quality of Pagatban River can be classified as Class C, which is suited for aquaculture use, the amount of heavy metals in its bottom sediments is not compatible with any fishery activities in the area,” according to an article in the latest issue of the Silliman Journal (Vol. 56, No. 1, 2015) by Dr. Robert S. Guino-o II, Michael Lawton R. Alcala and Jocelyn Elise P. Basa-Inocencio, of the Center for Tropical Conservation Studies (CENTROP) at Silliman University.
Pagatban River in Southern Negros Island is 25-km long, 70-meter wide river that separates the towns of Basay and Bayawan, Negros Oriental.
National Scientist Angel Alcala said it is one of the largest rivers draining a big portion of the southern plateau of Negros Island into the Sulu Sea, a major fishing ground.
In 1979, a copper mine was opened near the river, which dumped its effluents directly into it.
Pagatban River experienced massive fish kills in 1979-1983, which prompted the local government to ask Silliman scientists to look at the problem.
They found the river to be heavily degraded (heavy siltation, low biodiversity, presence of heavy metals copper and zinc in the water way above standard limits).
In 1984, the copper mine was closed, but no rehabilitation work was recorded since then.
The CENTROP group in 2011 went to the river to study its water quality “after three decades of post-mining activity,” using 17 measures for physical, chemical and biological characteristics of the water and standards set by the World Health Organization, the U.S. Environmental Protection Agency, and the Philippine Department of Environment and Natural Resources.
Here are some of the group’s findings:
• Heavy metals such as lead, copper and zinc in the waters of Pagatban River were below the detectable limit of 0.01 mg/L. This reflected a -87% variance from previous level, indicating that heavy metals in the Pagatban waters have been diluted after three decades without mining.
• However, heavy metals in the sediments of Pagatban River, particularly those at the river banks, showed high levels of heavy metals (more than 1 mg/kg to 242 mg/kg) compared to the EPA standard (0.025 to 0.090 mg/kg). This poses an environmental threat, because heavy metal contaminaton affects all levels in the food chain.
• In an earlier study, Alcala said corals and plankton are both very sensitive to copper and zinc pollution. Since plankton are the base of the food chain, effects on them may be very crucial. He added that zinc and copper have a synergistic effect, the combination being as much as five times more toxic than its additive effect.
• Severe flooding is another problem during the wet season causing drowning incidents of farm animals and people, destruction of houses along river banks, and damage to agricultural crops. Negros Island primary forest cover is four per cent of its land area.
• Pagatban River was contaminated with coliform bacteria at a level above maximum permissible limit during the dry season.
To improve the quality of Pagatban River, the researchers recommended the following:
• Implement the Clean Water Act of 2004 which prohibits the dumping of wastewater into creeks, rivers and marine waters without undergoing treatment
• Put up a flood warning system plan of action
• Stop clandestine operation of small-scale mining in Basay
• Stabilize the river banks with dikes and similar structures; plant mangroves in estuaries; continuing reforestation of the Bayawan-Basay watershed
• Provide adequate communal toilets in the area; provide access to sanitary landfill, compost area and regulated communal dumpsite
• Linkage between local government and NGOs to address environmental issues such as river biodiversity, conservation and management to sustain a healthy freshwater ecosystem. – Celia E. Acedo, SU Research and Environmental News Service
