M.Sc. Thesis 2000

CONCENTRATION, SPECIATION, PROVENANCE AND POLLUTION LEVELS OF HEAVY METALS IN THE BOTTOM SEDIMENTS OF THE

Roderick R. Amores

National Institute of Geological Sciences, College of Science, University of the , Diliman, 1101

Abstract The Pasig River System covers a total catchment area of approximately 4,150 sq. km. encompassing almost the entire Metro and portions of Province. Bottom sediment samples were collected from the mouth of the Pasig River in , to the upper fringes of the River, which defines the 40-kilometer length of the study area. Quantitative measure of heavy metal pollution was done using the Index of Geoaccumulation (Igeo) which standardizes metal concentration from background sources, and corrects for possible lithogenic variations. This index consists of seven grades (0-6) where the highest grade (6) reflects a 100- fold enrichment of metal levels from the background values. Three zones of extraneous heavy metal accumulation in sediments were defined in the Pasig River system. These are (1) the discharge of the Pasig River near the South Harbor, (2) the stretch of the Pasig River from its mouth to Vergara (- boundary), and (3) the Lower from Napinadan to the City of Pasig. The sediment quality near the South Harbor is defined by Igeo classes equivalent to 6 for Ni; 3 for Zn and Cu; 2-3 for Pb; 2 for Mn and Co; and 1-2 for Fe. The entire length of the Lower Pasig River and a portion of the Upper Pasig to Vergara is characterized by Igeo class ranges of 0-6 for Cd, 1-4 Zn, 0-4 Pb, 0 and 3 Ni, 1-2 Cu, 0-3 for Mn, and 0-1 for both Fe and Co. Maximum pollution classes for Cd (6), Pb (3), Zn (4), and Mn (2) occur at the of the San Juan and Pasig . The section of the Marikina River from the Napindan Hydraulic Control Structure going upstream to Pasig City, manifests Igeo classes 1-3 for Zn, 0-1 for Fe and Co, 0-2 for Mn, 1-2 for Cu, 0-3 for Pb and 0-6 for Cd. The moderately reducible phase (Fe and Mn-oxides) is the dominant matrix of heavy metal distribution in the Pasig River sediments. In decreasing order, the general occurrence of metal species trends as follows: residual > moderately reducible > exchangeable > organic fraction and sulfides > carbonates and easily reducible. The residual fraction comprises lattice-bound metals and is not a significant matrix of heavy metal pollutants. The conspicuous spatial correlation of sectors of metal pollution with specific industrial land utilities along the Pasig River affirms a strong anthropogenic provenance for these pollutants. Metal pollution in Manila Bay area represents the compounded effects of both river discharge and shipping/transportation (South Harbor) activities into the bay. Metal-specific pollution in the Pasig River is closely associated with esteros and other feeder channels that serve as conduits for direct metal-laden discharges (effluents); and as pathways for metals derived from run-off in areas farther from the river.