The abandoned mercury (Hg) mine area in Puerto Princesa City, Palawan was included in the list of abandoned and inactive mines in the Philippines which pose a high risk to human health and the environment, and require rehabilitation. The mine site, operated by Palawan Quicksilver Mines, Inc. (PQMI) from 1953 to 1976, is located approximately 3 km inland from Honda Bay coast and within the catchment of the Tagburos River, which is a local fishery and recreational area. In this study, total Hg levels in soils and sediments were measured to assess the possible release of Hg from the site into the surrounding natural environment. Results showed that total Hg (THg) concentrations found in soils (0.04–67.5 mg kg−1), mine waste calcines (52.7–924.2 mg kg−1), river sediments (1.8–119 mg kg−1), and marine sediments (0.04–12.7 mg kg−1) were elevated compared to the global background of 0.045–0.16 mg kg−1. The high concentrations of Hg in soils and river sediments were influenced by the different pathways for the release of Hg from its mine operations; while Hg in marine sediments was caused by the erosion of mine waste calcines near the pit lake, and calcines used to construct a wharf at the nearby Honda Bay. Mine wastes represent the largest source of Hg contamination in the area, due to the low efficiency of the recovery process during calcination. This work corresponds with the Minamata Convention on Mercury on the updated environmental assessments of abandoned Hg mines as potential source sites of mercury contamination.

An abandoned mercury mine area in Puerto Princesa City, which was previously operated by Palawan Quicksilver Mines, Inc. (PQMI) from 1953 to 1976, is known for its unrehabilitated open-pit of mercury-rich rocks and exposed mine waste calcine stockpiles in the vicinity. In order to establish an understanding on the geology of the abandoned mercury mine deposit and to obtain clues in determining the possible metal pollutants in the area, measurement of trace element concentrations of soil and sediments collected from the PQMI vicinity were conducted. Soil and sediment samples were analyzed for heavy metals, rare-earth elements and naturally occurring radioactive elements and determined its contamination factor as part of risk assessment. Analytical results showed that aside from mercury, several heavy metals (nickel, chromium, manganese) were found to be anomalous due to the geology of the area. Statistical analyses show that chromium, nickel and antimony present the highest contamination factor among the sampling groups. Mercury is found to have negative bias with higher rare earth elements concentration but positively correlated with arsenic, antimony, and thallium. In general, there is low concentration of rare earth elements (except for scandium) in comparison with its respective average crustal concentration. Due to the nature of geology in the area, naturally occurring radioactive elements influence is also minimal. The results of this study, especially on the assessment of soil and sediment pollutants, are recommended as guidance to its mine rehabilitation.

Most abandoned and inactive mines in the Philippines pose high risks to human health and the environment due to the disturbed and exposed heavy metal-laden soils and sediments and water-filled open pit mines. Establishing these mines’ environmental conditions remains a challenge as it requires time, effort, resources, and faces a lack of funding as the economic phase of the mine has already ceased. In order to contribute to the solution on the assessment of abandoned and inactive mines, integrated methods with combined essential testing, sampling, and analyses of different environmental media present in the mine site are suggested in this paper. On-site and laboratory methods include analyses for water (surface water and groundwater characterization, quality assessment, and environmental isotope tracers), soils and sediments (heavy and trace metals, anomalous elements, erosion, and nutrient availability), air quality, and radiometric survey. These methods can be classified as rapid with complete data, and information can be gathered to support a health risk assessment in the area, as well as used as a guide for rehabilitation prioritization of the abandoned mines.

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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.