Concentration, speciation, provenance and pollution levels of heavy metals in the bottom sediments of the Pasig River [Philippines]
2000
Amores, R.R.
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 (Mandaluyong-Makati boundary), and (3) the Lower Marikina river from Napindan to the City of Pasig. The sediment quality near the South Harbor is defined by 1 sub geo 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 l sub geo 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 confluence of the San Juan and Pasig Rivers. The section of the Marikina river from the Napindan Hydraulic Control Structure going upstream to Pasig City, manifest l sub geo 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 conspicous 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 further from the river
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