Monitoring and profiling of artisanal and small scale mining at Rogongon: effects on the physicochemical and biological characteristics of surface water and mercury concentration in sediments of Mandulog River system

摘要

Small scale and artisanal mining are everywhere in the Philippines which made people think ofit as dirty and dangerous, thus should be discouraged due to its negative environmental and socialimpacts. Mining inventory at Rogongon, Iligan City, and along the Mandulog River system wasconducted. There were seven abandoned, one legal, and one unregistered small scale mining entitiesfound in the area; and five groups and 15 individuals of artisanal riverbed miners were found activeduring the investigations. The effects of these mining activities were analysed through the physicochemical and biological characteristics such as: pH, temperature, dissolved oxygen, biological oxygendemand, total dissolved solids, total suspended solids of surface water including mercury concentration insediments of Mandulog River. Water samples were collected during wet and dry weather at nine (9)sampling points located near small scale mining area, tributaries and down to the mouth of the river andthe sea of Iligan Bay. The results of the physico-chemical and biological parameters of the surface watersuggest that the Mandulog River system conforms to the classification as Class C. The river was classifiedas Class D by the Department of Environment and Natural Resources Region X due to the mercuryconcentrations in sediments of the river even if it is lower than the standard which is 200 μg kg-1 (0.2 μgkg-1); thus implies mining wastes being flushed to it.