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The enrichment levels of potentially toxic elements (PTEs) have recently attracted global concerns due to their associated environmental risks and threats to human health. This study, therefore, aims to assess the pollution impacts of these PTEs from 53 marine sediment samples from Puerto Princesa Bay, Palawan, the Philippines. The concentrations of eight PTEs (As, Co, Cr, Cu, Hg, Mn, Ni, and Zn) were determined using portable X-ray fluorescence spectroscopy and direct mercury analyzer. Spatial distribution maps of the bay revealed similar trends for Cr, Co, Cu, Mn, Ni, As, and Zn, with higher concentrations found at the north-western side of Puerto Princesa Bay. Factor analysis revealed that this trend can be attributed to natural provenance. Moreover, a higher concentration of As was concentrated in the southern part of the bay adjacent to the built-up areas of Puerto Princesa City, whereas Hg had higher concentrations in the northern part. Their distribution can be attributed to anthropogenic influence: Hg transport exacerbated by historical mercury mining upstream and industrial activities in the built-up bay that lead to the enrichment of As. Further assessment using the enrichment factor and index of geoaccumulation indices support the mentioned factors of PTEs based on their enrichment and contamination levels. Lastly, the total potential ecological risk index revealed Co, Hg, and Ni - which are most likely to be the main pollutants - particularly in the northern part of the bay. Based on the evaluated indices, these PTEs are potential sources of ecological risks to the environment, as well as to the inhabitants of the area. The results are significant inputs in baselining the current PTE pollution caused in Puerto Princesa Bay, Palawan, as well as for decisions regarding mixed-use planning of the bay area. [ABSTRACT FROM AUTHOR]

Critical minerals (CMs) such as nickel (Ni), cobalt (Co) Co, chromium (Cr), manganese (Mn), and zinc (Zn) are materials essential to the economy, but the supply is vulnerable to disruption. Ni laterite deposits are considered potential sources of these CMs. In this study, the Ni, Co, Cr, Mn, and Zn contents of 15 Ni laterite samples from Zambales and Surigao were determined using handheld laser-induced breakdown spectroscopy (hLIBS) and handheld X-ray fluorescence (hXRF) analyzers. The samples were also analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to compare the handheld analyzers with the established laboratory technique. The two-sided t-tests show no significant differences between the average Ni, Cr, Mn, and Zn results of hLIBS and hXRF with respect to ICP-MS. The average hXRF result of Co significantly differs from ICP-MS, whereas hLIBS has no significant difference from ICPMS. Therefore, hLIBS and hXRF can be used to determine the Ni, Cr, Mn, and Zn contents in laterites, whereas hLIBS can be utilized to determine the Co values of laterites. Both hLIBS and hXRF analyzers can be for CM exploration of Ni laterite deposits. [ABSTRACT FROM AUTHOR]

Hot springs in the Philippines are found mostly near volcanic regions and are the least places with possibly high background radiation. However, Makinit hot spring in El Nido, Palawan exists not only on the tectonically stable northern Palawan Microcontinental Block but also records anomalously high natural radioactivity. To quantify and determine the nature of radioactivity, this study conducted a preliminary radiological and geochemical study in the vicinity of this hot spring. The measured average specific activities of uranium and thorium were 1528.62 and 920.96 Bq/kg, and these exceed world median values on terrestrial radionuclides in the soil of 35 and 30 Bq/kg by 44 and 31 times higher, respectively. The average values of all seven calculated radiological risk parameters -- namely, dose rate with an amount of 13.77 mSv/y, radium equivalent of 2862.10 Bq/kg, external and internal hazard indices of 7.73 and 11.86, respectively, absorbed gamma dose rate of 1271.42 nGy/h, annual effective dose equivalent of 1.56 mSv/y, and excess lifetime cancer risk of 5.46 x 10-3 -- go beyond reference limits set by the UNSCEAR. The preliminary assessment of spring water physicochemical properties showed that the water temperature is greater than 55 °C and the pH averages around 6.62, indicating weak acid-neutral hot waters and a low to moderate temperature geothermal system. The sediments surrounding the Makinit hot spring were analyzed to be travertine, composed only of calcite, suggesting that the uranium and thorium ions are potentially bonded or are associated with the Ca-bearing mineral. This study can serve as a baseline for further research regarding the source of radioactivity and geothermal heat source and as a consideration for the development of the Makinit hot spring area. [ABSTRACT FROM AUTHOR]

The rare earth elements (REEs) are crucial components of green technology and are now considered critical raw materials. One of the emerging tools in mineral exploration, laser-induced breakdown spectroscopy (LIBS), was used by several studies to determine the REE contents of different geological materials. In this study, the concentrations of selected REEs (La, Ce, Pr, Nd, Sm, Gd, Dy, and Yb) in 11 ion adsorption clays (IACs) from El Nido, Palawan, Philippines were determined using a handheld LIBS analyzer. The REE contents of the samples were also determined using inductively coupled plasma mass spectrometry (ICP-MS) to compare LIBS with the established laboratory technique. The two-sided t-test shows no significant differences for the average La, Ce, Pr, Nd, Sm, and Gd results of LIBS and ICP-MS, whereas Dy and Yb have significant differences. Based on these results, it can be concluded that LIBS can be an alternative to ICP-MS for the rapid determination of some REE in IACs. [ABSTRACT FROM AUTHOR]

In the Philippines, legacy mines and active mine wastes pose potential threats since these may contain elevated concentrations of potentially toxic elements (PTEs) and high natural radioactivity. In this study, legacy mine wastes from the Philippine Iron Mine (PIM), Barlo Mine (BM), and Rapu-Rapu Mine (RRM) and active mine tailing from Padcal Mine (PM) were analyzed to determine the concentrations of fifteen (15) PTEs and the activity concentrations of natural radionuclides. Several quantitative risk indicators and radiological health risk parameters were utilized to determine the potential effects of these mine wastes to the natural environment and to human health. Legacy mine wastes have higher contents of PTEs and are more polluted by PTEs than PM tailing. Both enrichment factor (EF) and geoaccumulation index (Igeo) values suggest that legacy mine wastes are strongly polluted by As, Cd, Cu, and Mo. BM and RM wastes are also polluted by Pb, Sb, and Zn; PIM waste is polluted by Ni and V; and BM waste is polluted by Tl. Padcal mine tailing is only moderately polluted by Cu and Mo. The natural radionuclide activity concentrations of legacy and active mine wastes are below the global background values and the radiological hazard indices are also all lower than their permissible limits, except for 40K, 238U, and absorbed gamma dose rate in PIM due to a geogenic source. Unlike the PTEs, radioactivity in the legacy and active mine wastes are not enhanced by mining activities and is not a significant risk factor to human health. [ABSTRACT FROM AUTHOR]

Abandoned mines pose high risks to human health and the environment due to the disturbed and exposed metal-laden soils and sediments. In this study, soils and sediments in an abandoned mercury (Hg) mine in Puerto Princesa City, Philippines were analyzed to assess the potential adverse health effects of the exposure to trace metals associated with the mine wastes. A total of 63 soil and sediment samples were collected in the area and analyzed for Hg concentration using a direct Hg analyzer and inductively coupled plasma--mass spectrometry (ICP-MS) for other trace metals. Analysis results showed that aside from Hg, there are anomalous concentrations of Ni (nickel), Cr (chromium), and Mn (manganese) in the area brought by the value of the mineralogy of the ores that were mined. The measured trace metal concentrations, together with the United States (US) Environmental Protection Agency's (EPA) exposure parameters and the US Department of Energy's (DOE) toxicity values were used to calculate the dose contacted from different exposure pathways. The result of the health risk assessment showed that Hg was considered as the main contributor of non-carcinogenic risk in the area with a hazard index of > 1 for both children and adults. Inhalation of Hg vapor from the soils and sediments is found to be a significant addition to the health risks in the area. Other trace metals such as Co (cobalt), Fe (iron), Ni (nickel), and Tl (thallium) were calculated with a hazard index greater than 1, which poses a health risk to children due to the ingestion pathway. All carcinogenic trace metals assessed were below the guidance value, indicating no significant carcinogenic health risks for both adults and children in the area. This work serves as an initial step of the country in the assessment of the risks to human health and the environment brought by Hg contaminated areas, as stated in the Minamata Convention on Mercury. [ABSTRACT FROM AUTHOR]

This study was part of an ongoing research project aimed to trace the pathways of possible mercury (Hg) contamination in an abandoned Hg mine site formerly operated by Palawan Quicksilver Mines, Inc. (PQMI) in Puerto Princesa City, Palawan. This mined-out area has been identified as the possible cause for the recent reported Hg poisoning cases among the residents living near the vicinity. To evaluate the water quality in the area, water samples collected from pit lake, river, coast, other nearby streams, leachate from landfill, and hot spring were analyzed for physicochemical parameters and heavy metal concentrations. Results showed that the physicochemical characteristics of freshwater (pit lake and river) and coastal water were generally within the water quality guidelines. Heavy metals in pit lake and river – except for Mn and Ni, Fe, and Mn – were measured within the guidelines, respectively. Hg concentrations in pit lake and river were not detected while low Hg concentrations were measured in coastal water near the jetty (0.001 mg/L) and in hot spring (≤0.0004 mg/L). A landfill near the pit lake was releasing partially-treated leachate with high total suspended solids (TSS) and heavy metal concentrations that contribute to the pollution in the area. [ABSTRACT FROM AUTHOR]