Three sediment cores (MNL1, MNL2, and MNL3) were collected
on 26 May 2006 from the central to southern side of Manila Bay
(Fig. 1) using a gravity core sampler (Kajak–Brinkhurst type gravity
corer). The sample properties are summarized in Table 1. Sample
MNL1 was collected at the extension of the Pasig River, where sediments
are largely transported by river flow. Samples MNL2 and
MNL3 were collected from the southern part of Manila Bay. We
suggest that these cores retain average information on the pollution
of a wide area of the bay. An acrylic core sampler, 50 cm in
length and 5 cm in diameter, was used to obtain sediment cores
of 22–45 cm at each site (Table 1). The sediment cores were sectioned
at 1 cm intervals using a thin plastic cutter. The samples
were immediately stored in plastic bags, frozen, and then transported
to the laboratory where they were stored in a freezer at
30 C. The frozen sediments were freeze-dried and water contents
were measured. Sediment fragments larger than 1 mm and
seashells were carefully removed by hand. Grain sizes were
analyzed using a laser diffraction particle analyzer (LS13 320, Beckman
Coulter). Samples for heavy metal concentration determination
and Pb isotope analysis were pulverized in a tungsten
carbide vessel using a Herzog HP–MS.