Volume 9, Number 4 (July 2022):3621-3633, doi:10.15243/jdmlm.2022.094.3621 ISSN: 2339-076X (p); 2502-2458 (e), www.jdmlm.ub.ac.id
Open Access 3621 Research Article
Pollution and radiological risk assessments of mine wastes from selected legacy and active mines in the Philippines
Cris Reven L. Gibaga*, Jessie O. Samaniego, Alexandria M. Tanciongco, Rico Neil M.
Quierrez, Mariel O. Montano, John Henry C. Gervasio, Rachelle Clien G. Reyes, Monica Joyce V. Peralta
Department of Science and Technology-Philippine Nuclear Research Institute (DOST-PNRI), Commonwealth Avenue, Diliman, Quezon City, Philippines
*corresponding author: [email protected]
Abstract Article history:
Received 15 March 2022 Accepted 30 April 2022 Published 1 July 2022
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.
Keywords:
legacy mine mine waste
potentially toxic element pollution assessment radiological risk assessment tailing
To cite this article: Gibaga, C.R., Samaniego, J., Tanciongco, A., Quierrez, R.N., Montano, M., Gervasio, J.H., Reyes, R.C.
and Peralta, M.J. 2022. Pollution and radiological risk assessments of mine wastes from selected legacy and active mines in the Philippines. Journal of Degraded and Mining Lands Management 9(4):3621-3633, doi:10.15243/jdmlm.2022.094.3621.
Introduction
Legacy mine land, defined by Worrall et al. (2009), is a land which has been mined and is now being used for another purpose, or is orphaned, abandoned or derelict and in need of remedial work. One of the issues faced by legacy mines is the persistent environmental impacts that pose potential threats to the natural environment and to human health (Samaniego et al.
2020a). Mine wastes, which include tailings and low- grade waste rocks that were accumulated during the mine operation in these legacy mines, contain elevated potentially toxic elements (PTEs) values (e.g., Lanot et al., 2020; Samaniego et al., 2020b; Uugwanga et al., 2020; Samaniego et al., 2021; Zhao et al., 2021) and high natural radioactivity (e.g. Isinkaye, 2013;
Nikolov et al., 2014; Wapwera et al., 2015). These unvegetated mine wastes are exposed to weathering,
Open Access 3622 surface runoff, and infiltration which will discharge
the PTE and natural radionuclides through different channels. This may result in the pollution of agricultural soil and various health problems in the nearby residents (Zhao et al., 2021).
In the Philippines, the Mines and Geosciences Bureau (MGB) listed twenty-seven (27) abandoned and inactive mines (Aggangan et al., 2019; Samaniego et al., 2020a). The list includes different gold, copper, chromite, marble, mercury, iron, pyrite, and silica mines which ceased operation due to low metal prices.
Most of these mines were abandoned before the passage of the Philippine Mining Act of 1995 and some are unremediated until now (Samaniego et al., 2020a). In this study, representative samples from three legacy mines in Camarines Norte, Pangasinan, and Albay (Figure 1) were collected and subjected to geochemical and radiometric analyses to determine the PTE concentrations and natural radioactivity of their mine wastes. These were also compared to the PTE and natural radioactivity concentrations of mine tailings from an active mine in Benguet. Several quantitative risk indicators and radiological health risk parameters were utilized in this study to determine the potential effects of these mine wastes to the natural environment and to human health.
Figure 1. Sample Location Map of the selected legacy and active mines in the Philippines. Base map from
Google Earth.
The abandoned iron mine in Jose Panganiban, Camarines Norte was operated by the Philippine Iron Mine (PIM) from 1925 to 1975 and it used to be the biggest iron mine in Asia during its operation. The mine operation left two pit lakes in the area, the Main Pit Lake, and the Bessemer Pit Lake (Figure 2a). The Bessemer deposit, which was mined by the PIM, is a Fe-Cu-Mo skarn deposit associated mainly with pyrite and magnetite mineralization, with minor molybdenite and chalcopyrite disseminated in the host rock localized in calcareous sediments (Aurelio and Peña, 2004). The estimated resource of the deposit is around 12.59 million metric tons with 10% Fe and 0.291% Cu (Aurelio and Peña, 2004). A stockpile of PIM waste rock is located around 500 meters west of the Main Pit Lake and consists of pebble to boulder-sized rocks (Figure 3a). The community landfill of Jose Panganiban and the Larap airport were constructed in the former mine tailing ponds of the abandoned mine.
The abandoned copper mine in Mabini, Pangasinan was operated by Barlo Mining Corporation until 1981 and it left mine wastes rich in massive sulfide minerals (Figure 3b). The copper-zinc geologic deposit mined in Barlo Mine (BM) is a Cyprus-type volcanogenic massive sulfide (VMS) deposit, in which base metal sulfide ores are associated with rocks of mafic-ultramafic association of ophiolitic affinity (Aurelio and Peña, 2004). The mineralization in the deposit is related to chalcopyrite, sphalerite, pyrite, chalcocite and traces of galena, gold, and silver (Aurelio and Peña, 2004). Some of the sulfide-rich mine wastes of BM are in the abandoned processing plant (Figure 2b) located around 2.5 kilometers northwest of the abandoned mine.
Rapu-Rapu Mine (RRM) is a polymetallic legacy mine located in Rapu-Rapu Island, Albay (Figure 2b) where Au, Ag, Cu, and Zn were extracted. The Ungay- Malobago deposit of RRM is a Besshi-type VMS deposit, in which the deformed and dismembered massive sulfide ore body are hosted by altered dacitic layers and intercalated quartzo-feldspathic schists (Aurelio and Peña, 2004). The massive sulfide body is dominantly pyrite with chalcopyrite, sphalerite, and galena, while the occurrences of chalcocite, covellite, tetrahedrite, bornite, and visible gold have also been recognized (Sherlock et al., 2003; Aurelio and Peña, 2004). The estimated resource for the Ungay- Malobago deposit is 7.02 million metric tons at 2.61 g/t Au, 28.14 g/t Ag, 1.24% Cu, and 2.06% Zn (Sherlock et al., 2003). The mine operation started in 2005 while the rehabilitation work for the RRM began in 2013 (Dumangas, 2008; Gonzales, 2018).
Padcal Mine (PM) is a copper mine in Benguet province that has been operational since 1958 (Minerva, 2018). Sto. Tomas II deposit of PM is a cylindrical/pipe-like porphyry-Cu ore body with an estimated total ore reserve of 370 million metric tons at 0.31% Cu and 0.63 g/t Au (Imai, 2001; Aurelio and Peña, 2004).
Open Access 3623 Figure 2. Sample Location Map of the mine wastes from the selected abandoned mines in the study. (a) Abandoned Fe mine of the Philippine Iron Mine in Jose Panganiban, Camarines Norte. (B) Abandoned Barlo Cu Mine in Mabini, Pangasinan. (C) Rapu-Rapu Mine, a polymetallic legacy mine in Rapu-Rapu Island, Albay. (C)
Padcal Cu-Au Mine in Itogon, Benguet. Satellite imagery from Google, Maxar Technologies, CNES/Airbus The principal ore minerals are chalcopyrite, bornite,
and magnetite with traces of molybdenite, Au, Ag, and Pd-bearing minerals (Imai, 2001). Since 1992, mine tailings of PM are stored in the third tailings storage facility (TSF 3) located around 3 kilometers southeast of the mine site (Figure 2b) (Minerva, 2018). PM mine tailings consist of silt- to very fine sand-sized sediments.
Materials and Methods Mine tailing sampling
A total of eleven (11) representative mine waste samples from selected legacy mines and three (3) representative mine tailings from the active Padcal mine were collected in 2021 for pollution and radiological risk assessments. Five (5) mine waste samples from abandoned PIM were collected in July 2021, 3 mine waste samples were collected from abandoned BM in September 2021, and 3 mine waste samples from abandoned RRM were collected in November 2021. Tailing samples from active PM were collected in June 2021. Samples were collected using a plastic trowel, from the top 10 cm of the tailing soil surface and were placed in polyethylene resealable plastic bags. All samples were prepared by air-drying
and sieving up to U.S. Standard 230 mesh (63 μm), to separate the silt-clay (<63 μm) size particles from the sand fraction. To minimize sediment size bias, only the
<63 μm fractions were analyzed for geochemical analysis.
Geochemical analysis
To determine the concentrations of the 15 potentially toxic elements (PTE) (As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Sn, Tl, V, and Zn), samples were sent to Intertek Minerals Philippines Laboratory for Inductively Coupled Plasma-Mass Spectrometry (ICP- MS) analysis using Agilent 7000x machine. Before the analysis, around ten (10) grams of sample underwent aqua regia digestion procedure that included dissolution using nitric acid (HNO3) and hydrochloric acid (HCl) at a 1:3 ratio. Multi-element certified reference materials (OREAS 600, 623, 920, and 923) were digested and analyzed along with samples to serve as quality control.
Radiometric analysis
In situ radiometric measurements were conducted in each sample location in the selected legacy and active mines to determine the concentrations of natural radionuclides 40K, 232U, and 238Th using a handheld BGO gamma-ray spectrometer (Radiation Solutions
Open Access 3624 RS-230). RS-230 gamma-ray spectrometer has
Bismuth Germanate Oxide (BGO) detector and auto- stabilizing on the natural radionuclides. The concentration of natural radionuclides 40K was
calculated based on its gamma rays at 1461 KeV, 238U at 1765 KeV emitted by 214Bi, and 232Th at 2615 KeV emitted by 208Tl. K (%), U (ppm), and Th (ppm) values were determined at 300-seconds assay measurements.
Figure 3. Mine wastes of the selected legacy and active mines in the Philippines. (a) Waste rocks of the abandoned Philippine Iron Mine in Jose Panganiban, Camarines Norte. (b) Sulfide-rich waste rocks of the abandoned Barlo Mine in Mabini, Pangasinan. (c) Massive sulfide waste rocks of the Rapu-Rapu Mine in Albay.
(d) Mine tailings of Padcal Mine in Benguet.
Prior to the in situ measurements, the reliability of the handheld gamma-ray spectrometer was validated using the sets of 1m × 1m × 30 cm concrete standard calibration pads in the Philippine Nuclear Research Institute (PNRI). The radiometric measurements were converted from content (% or ppm) to activity concentrations (Bq kg-1) using the conversion factors of Erdi-Krausz et al. (2003).
Pollution assessment
To assess the enrichment of PTEs and the degree of contamination in mine wastes, quantitative risk indicators such as enrichment factor, geoaccumulation index, and pollution load index were calculated. The average upper continental crust (UCC) values of
Rudnick and Gao (2014) were used as background values for all the calculations.
Enrichment Factor
The enrichment factor (EF) was calculated using the formula introduced by Buat-Menard and Chesselet (1979) and used by Zhao et al. (2021):
EF =( ) / ( )
( ) / ( ) (1)
where (Xi)sample is the measured concentration of the PTE in the sample, (RE)sample is the measured concentration of the reference element (e.g., Sc, Ti, Al, Zr) in the sample, (Xi)crust is the average concentration of the PTE in the crust and (RE)crust is the average
Open Access 3625 concentration of the reference element in the crust. In
this study, Sc was used as a reference element to calculate the enrichment factor. Five (5) contamination categories are defined by Sutherland et al. (2000) based on EF value, as shown in Table 1.
Table 1. Categories of enrichment factor.
Category Description
EF < 2 Deficiently to minimal enrichment 2 ≤ EF < 5 Moderate enrichment 5 ≤ EF < 20 Significant enrichment 20 ≤ EF < 40 Very high enrichment
EF ≥ 40 Extremely high enrichment The enrichment factor can also be used to differentiate crustal from non-crustal origins of a given element. An EF value close to 1 suggests a crustal origin while EF values >10 could indicate that the PTEs have non- crustal origin (Gałuszka and Migaszewski, 2011).
Index of geoaccumulation
The index of geoaccumulation enables the assessment of contamination by comparing the current PTE concentrations and the background concentration. This was calculated using the formula introduced by Müller (1969):
I = log
. ∗ (2)
where Cn is the measured concentration of PTE in the sample and Bn is the geochemical background values.
The factor 1.5 is introduced in Eq. (2) to minimize the effect of possible variations in the background data, Bn, which may be attributed to lithogenic variations in soils. Table 2 shows the seven (7) descriptive classes for increasing Igeo values as proposed by Müller (1969).
Table 2. Categories of index of geoaccumulation.
Igeo value Igeoclass Description
Igeo≤ 0 0 Uncontaminated
0<Igeo≤1 1 Uncontaminated to moderately contaminated 1 <Igeo ≤ 2 2 Moderately contaminated 2 <Igeo ≤ 3 3 Moderately to strongly
contaminated 3 <Igeo ≤ 4 4 Strongly contaminated 4 <Igeo ≤ 5 5 Strongly to extremely
contaminated Igeo> 5 6 Extremely contaminated
Radiological risk assessment
To assess the radiological risks related to the natural radionuclides 40K, 232U, and 238Th in the mine wastes, several radiological health risk parameters such as radium equivalent activity, absorbed gamma dose rate,
annual effective dose equivalent, gamma representative level index, external hazard index, and internal hazard index were calculated.
Radium equivalent activity (Raeq)
Radium equivalent activity is an index that represents the specific activities of 40K, 238U, and 232Th by a single quantity, which considers the radiation hazards associated with them (Beretka and Matthew, 1985).
The radium equivalent activities of the tailings were calculated using the equation:
Ra (Bq kg ) = 0.077A + A + 1.43A (4) where AK, AU, and ATh are the specific activities of
40K, 238U, and 232Th (Bq kg-1), respectively. The formula assumes that 4810 Bq kg-1 of 40K, 370 Bq kg-
1 of 238U, and 259 Bq kg-1 of 232Th emit the same gamma dose rate (UNSCEAR, 2000). This index is related to the external gamma dose and internal dose due to radon and its daughters (Beretka and Matthew, 1985).
Absorbed gamma dose rate (DR)
To assess the external terrestrial gamma-ray exposure at 1 m above the ground surface, the absorbed gamma dose rate was calculated using the equation:
D (nGy h ) = 0.042A + 0.462A + 0.604A (5) where AK, AU, and ATh are the specific activities of
40K, 238U, and 232Th (Bq kg-1), respectively (UNSCEAR, 2000). This assumes that other radionuclides like 137Cs, 90Sr, and 235U decay series can be neglected since they have very little contribution to the total dose from the environmental background.
Annual effective dose equivalent (AEDE)
To assess the public radiation hazard exposure due to natural radioactivity in the tailings, the annual effective dose equivalent was determined using the equation:
AEDE (mSv y-1) = DR(nGy h-1) x 8760 h x 0.2 x 0.7 (SvG y-1) x 10-6 (6) where DR is the absorbed gamma dose rate, 0.7 SvG y-
1 is the conversion factor for the effective dose received by adults and 0.2 is the outdoor occupancy factor (UNSCEAR, 2000).
Gamma representative level index (Iγ)
To evaluate the degree of gamma radiation hazards associated with the natural radionuclides in construction materials, the gamma representative level index was calculated using the equation:
I = A 3000+ A
300+A
200 (7)
Open Access 3626 where AK, AU, and ATh are the specific activities of
40K, 238U, and 232Th (Bq kg-1), respectively (Beretka and Matthew, 1985).
External hazard index (Hex)
To determine the external exposure risk of an individual due to gamma-rays, the external hazard index was calculated using the equation:
H = A
4810 + A 370+A
259 (8) where AK, AU, and ATh are the specific activities of
40K, 238U, and 232Th (Bq kg-1), respectively (Beretka and Matthew, 1985).
Internal hazard index (Hin)
For the determination of internal exposure risk due to the inhalation of radon and its daughter products, the internal hazard index was calculated using the equation:
H = A
4810 + A 185+A
259 (9)
where AK, AU, and ATh are the specific activities of
40K, 238U, and 232Th (Bq kg-1), respectively (Beretka and Matthew, 1985).
Results and Discussion
The concentrations of the potentially toxic elements (PTEs) in mine wastes of the Philippine Iron Mine, Barlo Mine, Rapu-Rapu Mine, and Padcal mine are presented in Table 3. The average concentrations of the PTEs such as As, Cd, Co, Cu, Mo, Ni, Pb, Sb, Sn, and Zn in mine wastes of the legacy mines in the study are relatively higher compared to mine tailings from the active Padcal mine. Average BM and RRM mine wastes, both from massive sulfide deposits, have greater levels of Cd, Cu, Pb, Sb, Sn, Tl, and Zn compared to average PIM mine waste since these elements are considered as chalcophile elements and usually concentrated in sulfide minerals (Lee, 2018).
Mine wastes from PIM have higher average Co, Cr, Mo, Ni, and V contents than BM and RRM mine wastes since these PTEs are considered as siderophile elements which have an affinity for metallic phases (Lee, 2018).
The average As, Cu, Mo, and Ni contents of mine wastes from selected legacy mines are higher with respect to the average upper continental crust (UCC) composition of Rudnick and Gao (2014) and to the Canadian soil quality standards for industrial soil (CCME, 2007) as shown in Table 4. Compared to the average UCC composition and the Canadian soil quality standard, BM and RRM mine wastes have higher average Cd, Pb, Tl, and Zn contents, while PIM mine wastes have higher average Co, Cr, and V concentrations. The PTEs contents of PM tailings are lower with respect to average UCC composition and
Canadian soil quality standards except for Cu, Mo, and V.
With respect to the PTE contents of other mine wastes in the world, the As and Cu contents of average PIM mine waste are higher while the Co, Cr, Mn, Pb, and Zn values are much lower compared to average worldwide Fe ore mine wastes (Sahoo et al., 2021). For the massive sulfide-rich mine wastes of BM and RRM, their average As, Ni, Pb, Sb, and Zn contents are almost similar and their Cd and Sn levels are lower than the mine wastes from different sulfide mines in Spain (Martín-Crespo et al., 2019). The average As, Cu, Mo, Ni, Pb, and Zn contents of PM tailings are lower compared to the fresh mine tailings from porphyry mines in Chile (Rubinos et al., 2021).
The enrichment factors (EF) of legacy mine wastes and active mine tailings samples are shown in Table 4. The average EF values of PIM, BM, and RRM wastes suggest the extremely high enrichment of As, Cu, and Mo in the mine wastes. Both BM and RRM wastes also have extremely high enrichment of Cd, Pb, Sb, and Zn. PIM wastes have significant enrichment of Cd, Co, and V, and very high enrichment of Ni. BM wastes have extremely high Tl enrichment and significant Co enrichment. RRM wastes have significant Ni enrichment and very high enrichment of Co and Tl. The significant to extremely high enrichment of these PTEs in the mine wastes could also indicate the non-crustal and anthropogenic origin of PTEs (Gałuszka and Migaszewski, 2011). Other PTEs have minimal and moderate enrichment in the legacy mine wastes. For Padcal mine tailings, average EF values indicate the minimal and moderate enrichment of the PTEs, except for Cu which is significantly enriched in tailings. Legacy mine wastes have more PTEs that have very high and extremely high EF values compared to active mine tailings as shown in Table 5. Mine wastes from the legacy VMS mines (BM and RRM) also have more PTEs than legacy Fe mine (PIM).
The geoaccumulated index (Igeo) of legacy mine wastes and active mine tailings samples are shown in Table 6. The average Igeo values of legacy mine wastes indicate that PIM, BM, and RRM wastes are moderately to extremely contaminated (Igeo > 1) by As, Cu, Cd, and Mo. Both BM and RRM mine wastes are strongly to extremely contaminated by Pb, Sb, and Zn (Igeo > 3). PIM mine wastes are also moderately to strongly contaminated (1< Igeo < 3) by Ni, Co, and V.
On the other hand, the legacy mine wastes are uncontaminated by Ba, Cr, Mn, and Sn. Active mine tailings of Padcal are moderately to strongly contaminated by Cu and Mo (1< Igeo < 3) and uncontaminated by other potentially toxic elements.
Legacy mine wastes are strongly to extremely contaminated by up to 8 PTEs, in comparison to active mine tailing that has not reported strong to extreme contamination of PTEs (Table 7).
Open Access 3627 Table 3. Potentially toxic elements (PTEs) concentrations in representative mine waste samples from selected legacy and active mines in the Philippines.
Sample Name As
ppm Ba
ppm Cd
ppm Co
ppm Cr
ppm Cu
ppm Mn
ppm Mo
ppm Ni
ppm Pb
ppm Sb
ppm Sn
ppm Tl
ppm V
ppm Zn
ppm Sc
ppm Philippine Iron Mine
0727-07 45 54 1.07 26.8 4 148.3 362 62.9 21.1 14.1 0.24 0.79 0.20 43 61 2.4
0727-08 164 26 0.13 95.2 53 840.9 402 86.8 61 22.9 0.82 1.66 0.24 259 62 6.3
0727-09 199 10 0.19 74.9 39 926.2 390 83.8 53.7 14.5 1.1 1.11 0.23 259 43 3.9
0729-13 95 31 0.07 148.2 408 472.9 1,283 22.7 1,894 10.6 0.31 1.5 0.07 243 92 9.4
0729-16 48 12 0.15 82.9 155 378.3 725 27.4 391.8 11.1 0.76 1.82 0.03 771 59 3.7
Average 110 27 0.32 85.6 132 553.3 632 56.7 484.4 14.6 0.65 1.38 0.15 315 63 5.1
Barlo Mine
0912-01 564 6 13.05 22.5 15 10,000 123 17.7 13.9 113.1 22.36 1.55 18.50 19 3,133 1.9
0912-03 476 7 12.93 17.7 40 7,327 215 20.8 22.1 162.2 18.78 1.50 18.30 44 3,487 5.3
0912-11 707 7 4.98 35.6 8 10,000 88 50.9 20.9 519.1 49.14 2.57 45.01 8 1,095 0.7
Average 582 7 10.32 25.3 21 9,109 142 29.8 19.0 264.8 30.1 1.87 27.27 24 2,572 2.6
Rapu-Rapu Mine
1123-04 25 3 0.11 62.0 42 332.8 74 2.5 21.5 154 5.70 0.13 0.48 4 23 0.9
1123-05 236 30 30.3 23.9 31 3,641 146 5.8 34.7 1,381 8.78 0.35 4.20 20 6,187 2.1
1123-08 48 7 3.34 0.9 6 331.2 50 23.4 18.0 5,000 32.03 1.26 0.43 4 1,161 0.1
Average 103 13 11.25 28.9 26 1,435 90 10.6 24.7 2,178 15.50 0.58 1.70 9 2,457 1.0
Philex Mine
TSF3-A 1 42 0.05 16.3 71 266.0 711 3.5 7.7 2.6 0.02 0.76 0.20 161 42 22.2
TSF3-B 1 41 0.04 15.7 64 254.3 672 3.2 6.9 2.8 0.02 0.38 0.19 156 41 20.3
TSF3-C 1 29 0.04 12.0 47 381.6 589 4.3 6 2.4 0.02 0.53 0.13 183 35 15.5
Average 1 37 0.04 14.7 61 300.6 657 3.7 6.9 2.6 0.02 0.56 0.17 167 39 19.3
Avg. UCC 1 4.8 628 0.09 17.3 92 28 775 1.1 47 17 0.4 2.1 0.9 97 67 14
Soil Quality
Standards 2 12 750 1.4 40 64 63 - 5 50 70 20 5 1 130 200 -
1 average values for Upper Continental Crust (UCC) from Rudnick and Gao, 2014.
2 Canadian soil quality standards for industrial soil from CCME, 2007.
Open Access 3628 Table 4. Enrichment Factor (EF) values of PTEs in representative mine waste samples from selected legacy and active mines in the Philippines.
Sample Name As Ba Cd Co Cr Cu Mn Mo Ni Pb Sb Sn Tl V Zn
Philippine Iron Mine
0727-07 54.69 0.50 69.35 9.04 0.25 30.90 2.72 333.6 2.62 4.84 3.50 2.19 1.30 2.59 5.31
0727-08 75.93 0.09 3.21 12.23 1.28 66.74 1.15 175.4 2.88 2.99 4.56 1.76 0.59 5.93 2.06
0727-09 148.8 0.06 7.58 15.54 1.52 118.7 1.81 273.5 4.10 3.06 9.87 1.90 0.92 9.58 2.30
0729-13 29.48 0.07 1.16 12.76 6.60 25.15 2.47 30.7 60.03 0.93 1.15 1.06 0.12 3.73 2.05
0729-16 37.84 0.07 6.31 18.13 6.37 51.12 3.54 94.3 31.54 2.47 7.19 3.28 0.13 30.08 3.33
Average 62.53 0.12 9.74 13.48 3.90 53.82 2.22 140.5 28.07 2.35 4.40 1.78 0.47 8.85 2.58
Barlo Mine
0912-01 865.8 0.07 1,068 9.58 1.20 2,632 1.17 118.6 2.18 49.02 411.9 5.44 151.5 1.44 344.6
0912-03 262.0 0.03 379.5 2.70 1.15 691.2 0.73 50.0 1.24 25.20 124.0 1.89 53.71 1.20 137.5
0912-11 2,946 0.22 1,107 41.16 1.74 7,143 2.27 925.5 8.89 610.7 2,457 24.48 1,000 1.65 326.9
Average 645.0 0.06 609.6 7.76 1.21 1,730 0.97 144.0 2.15 82.81 400.0 4.74 161.1 1.30 204.1
Rapu-Rapu Mine
1123-04 81.02 0.07 19.01 55.75 7.10 184.9 1.49 35.35 7.12 140.9 221.7 0.96 8.30 0.64 5.34
1123-05 327.8 0.32 2,244 9.21 2.25 867.0 1.26 35.15 4.92 541.7 146.3 1.11 31.11 1.37 615.6
1123-08 1,400 1.56 5,196 7.28 9.13 1,656 9.03 2,978 53.62 41,176 11,211 84.00 66.89 5.77 2,426
Average 290.7 0.29 1,694 22.66 3.88 694.4 1.57 130.2 7.13 1,736 525.1 3.74 25.64 1.30 496.8
Philex Mine
TSF3-A 0.13 0.04 0.35 0.59 0.49 5.99 0.58 2.01 0.10 0.10 0.03 0.23 0.14 1.05 0.40
TSF3-B 0.14 0.05 0.31 0.63 0.48 6.26 0.60 2.01 0.10 0.11 0.03 0.12 0.15 1.11 0.42
TSF3-C 0.19 0.04 0.40 0.63 0.46 12.31 0.69 3.53 0.12 0.13 0.05 0.23 0.13 1.70 0.47
Average 0.15 0.04 0.35 0.61 0.48 7.78 0.61 2.41 0.11 0.11 0.04 0.19 0.14 1.24 0.43
Table 5. Enrichment Factor (EF) categories of PTEs in representative mine waste samples from selected legacy and active mines in the Philippines.
EF EF Category Philippine Iron Mine Barlo Mine Rapu-Rapu Mine Philex Mine
> 40 Extremely high enrichment As, Cu, Mo As, Cd, Cu, Mo, Pb, Sb, Tl, Zn As, Cd, Cu, Mo, Pb, Sb, Zn -
20 - 40 Very high enrichment Ni - Tl, Co -
5 - 20 Significant enrichment Cd, Co, V Co Ni Cu
2 - 5 Moderate enrichment Cr, Pb, Sb, Zn, Mn Ni, Sn Cr, Sn Mo
< 2 Deficiently to minimal enrichment Ba, Sn, Tl Ba, Cr, Mn, V Ba, Mn, V As, Ba, Cd, Co, Cr, Mn, Ni,
Pb, Sb, Sn, Tl, V, Zn
Open Access 3629 Table 6. Index of geoaccumulation (Igeo) values of PTEs in representative mine waste samples from selected legacy and active mines in the Philippines.
Sample Name As Ba Cd Co Cr Cu Mn Mo Ni Pb Sb Sn Tl V Zn
Philippine Iron Mine
0727-07 2.64 -4.12 2.99 0.05 -5.11 1.82 -1.68 5.25 -1.74 -0.85 -1.32 -2.00 -2.75 -1.76 -0.72 0727-08 4.51 -5.18 -0.05 1.88 -1.38 4.32 -1.53 5.72 -0.21 -0.16 0.45 -0.92 -2.49 0.83 -0.70 0727-09 4.79 -6.56 0.49 1.53 -1.82 4.46 -1.58 5.67 -0.39 -0.81 0.87 -1.50 -2.55 0.83 -1.22 0729-13 3.72 -4.93 -0.95 2.51 1.56 3.49 0.14 3.78 4.75 -1.27 -0.95 -1.07 -4.27 0.74 -0.13 0729-16 2.74 -6.29 0.15 1.68 0.17 3.17 -0.68 4.05 2.47 -1.20 0.34 -0.79 -5.49 2.41 -0.77 Average 3.94 -5.15 1.25 1.72 -0.07 3.72 -0.88 5.10 2.78 -0.80 0.11 -1.19 -3.13 1.11 -0.66 Barlo Mine
0912-01 6.29 -7.29 6.59 -0.21 -3.20 7.90 -3.24 3.42 -2.34 2.15 5.22 -1.02 3.78 -2.94 4.96 0912-03 6.05 -7.07 6.58 -0.55 -1.79 7.45 -2.43 3.66 -1.67 2.67 4.97 -1.07 3.76 -1.73 5.12 0912-11 6.62 -7.07 5.21 0.46 -4.11 7.90 -3.72 4.95 -1.75 4.35 6.36 -0.29 5.06 -4.18 3.45 Average 6.34 -7.14 6.26 -0.04 -2.72 7.76 -3.03 4.17 -1.89 3.38 5.65 -0.75 4.34 -2.62 4.68 Rapu-Rapu Mine
1123-04 1.80 -8.29 -0.30 1.26 -1.72 2.99 -3.97 0.60 -1.71 2.59 3.25 -4.60 -1.49 -5.18 -2.13 1123-05 5.03 -4.97 7.81 -0.12 -2.15 6.44 -2.99 1.81 -1.02 5.76 3.87 -3.17 1.64 -2.86 5.94 1123-08 2.74 -7.07 4.63 -4.85 -4.52 2.98 -4.54 3.83 -1.97 7.62 5.74 -1.32 -1.65 -5.18 3.53 Average 3.84 -6.14 6.38 0.16 -2.39 5.09 -3.69 2.68 -1.51 6.42 4.69 -2.44 0.34 -3.96 4.61 Philex Mine
TSF3-A -2.85 -4.49 -1.43 -0.67 -0.96 2.66 -0.71 1.08 -3.19 -3.29 -4.91 -2.05 -2.75 0.15 -1.26 TSF3-B -2.85 -4.52 -1.75 -0.72 -1.11 2.60 -0.79 0.96 -3.35 -3.19 -4.91 -3.05 -2.83 0.10 -1.29 TSF3-C -2.85 -5.02 -1.75 -1.11 -1.55 3.18 -0.98 1.38 -3.55 -3.41 -4.91 -2.57 -3.38 0.33 -1.52 Average -2.85 -4.66 -1.64 -0.82 -1.19 2.84 -0.82 1.15 -3.36 -3.29 -4.91 -2.50 -2.96 0.20 -1.35
Open Access 3630 Both EF and Igeo values suggest that the selected legacy
mine wastes in this study are polluted by As, Cd, Cu, and Mo while pollution of Pb, Sb, and Zn are also present in BM and RRM wastes. PIM wastes also have Ni and V pollution, and BM mine wastes have Tl pollution. The active mine tailings from Padcal are less polluted compared to the mine wastes from legacy mines, whereas Cu and Mo are the only polluting PTEs in the tailings. High concentrations of Cu and Mo in PM tailings could be due to the presence of ore minerals, chalcopyrite, bornite and molybdenite in the tailings. Poor ore classification and mine/metallurgical management together with low technological efficiency before could be some of the reasons for the elevated concentrations of PTEs in the legacy mine wastes (Nwaila et al., 2021). Immediate remediation of the legacy mine wastes is needed to prevent the further discharge of the potentially toxic elements in the
environment and may pose health problems in the residents living at the vicinity of these mine wastes.
The radionuclide activity concentrations of legacy mine wastes and active mine tailing samples are presented in Table 8. The activity concentrations of natural radionuclides, 40K, 238U, and 232Th in legacy mine wastes and active mine tailings are below the worldwide average (UNSCEAR, 2010) except for the
40K and 238U in PIM wastes which are almost twice the global average. The average activity concentrations of
40K, 238U, and 232Th in PIM wastes are also higher by up to 5 times compared to the activity concentrations of natural radionuclides in Itakpe Iron-Ore Mine, Nigeria (Isinkaye, 2013). The average activity concentrations of 238U, and 232Th in mine waste of legacy Cu (BM and RRM) and active Cu (PM) mines are lower compared to the soil mine wastes of Kapan Cu mine in Armenia (Belyaeva et al., 2019).
Table 7. Index of geoaccumulation (Igeo) classification of PTEs in representative mine waste samples from selected legacy and active mines in the Philippines.
Igeo Igeo
Class Igeo Description Philippine
Iron Mine Barlo Mine Rapu-Rapu
Mine Philex Mine
> 5 6 Extremely contaminated Mo As, Cd, Cu,
Sb Cd, Cu, Pb -
4 - 5 5 Strongly to extremely
contaminated - Mo, Tl, Zn Sb, Zn -
3 - 4 4 Strongly contaminated As, Cu Pb As -
2 - 3 3 Moderately to strongly contaminated
Ni - Mo -
1 - 2 2 Moderately contaminated Cd, Co, V - - Cu, Mo
0 - 1 1 Uncontaminated to
moderately contaminated Sb - Co, Tl V
< 0 0 Uncontaminated Ba, Cr, Mn, Pb, Sn, Tl, Zn
Ba, Co, Cr, Mn, Ni, Sn, V
Ba, Cr, Mn, Ni, Sn, V
As, Ba, Cd, Co, Cr, Mn, Ni, Pb, Sb,
Sn, Tl, Zn
Table 8 also reports the calculated radiological health risk parameters of the mine wastes from selected legacy and active mines. The Raeq values of the mine wastes and tailing samples range from 13.5 to 159.3 Bq kg-1, which are lower than the recommended value 370 Bq kg-1 (NEA-OECD, 1979). The calculated DR
values of the BM and RRM waste, and Padcal mine tailing samples varies from 6.4 to 36.1 nGy h-1, which are below the world average value of 59 nGy h-1 (UNSCEAR, 2000). The average DR value of PIM waste is 71.5 nGy h-1, higher relative to the world average value. The AEDE values obtained for the mine wastes and tailing samples ranges from 0.01 to 0.10 mSv y-1, lower than the worldwide average value of 0.46 mSv y-1 (UNSCEAR, 1993). The calculated Iγ values of the mine wastes and tailing samples are less than 1 and vary from 0.09 to 0.60, indicating that there
will be no problem if these mine wastes are used as construction materials (UNSCEAR, 2000). Both the Hex and Hin values of the mine wastes and tailing samples are also less than 1, the recommended values of UNSCEAR (2000) for Hex and Hin. The slightly elevated 40K activity concentration in PM tailing is probably due to the presence of potassic alteration gangue minerals like biotite in the tailings (Imai, 2001). High activity concentration of 40K in PIM wastes could be associated to the presence of gangue minerals like amphibole while high 238U activity concentration and high DR values could be attributed to the reported presence of uraninite and pitchblende in the Bessemer deposit (Aurelio and Peña, 2004).
Radionuclides in the mine wastes originated in a natural and geogenic source and not from the mining activities.
Open Access 3631 Table 8. Activity concentrations of natural radionuclides and calculated radiological risk parameters for
representative mine waste samples from selected legacy and active mines in the Philippines.
Sample Name K U Th Radiological Risk Indicators
(Bq kg-1) (Bq kg-1) (Bq kg-1) Raeq
(Bq kg-1) DR
(nGy h-1)
AEDE (mSv y-1)
Iγ Hex Hin
Philippine Iron Mine
0727-07 939.0 64.2 14.2 156.8 77.7 0.10 0.60 0.42 0.60
0727-08 626.0 81.5 20.3 158.7 76.2 0.09 0.58 0.43 0.65
0727-09 657.3 80.3 19.9 159.3 76.7 0.09 0.59 0.43 0.65
0729-13 782.5 44.5 10.2 119.2 59.5 0.07 0.46 0.32 0.44
0729-16 1,033 42.0 7.7 132.6 67.4 0.08 0.52 0.36 0.47
Average 807.5 62.5 14.5 145.3 71.5 0.09 0.55 0.39 0.56
Barlo Mine
0912-01 156.5 19.8 1.6 34.1 16.7 0.02 0.13 0.09 0.15
0912-03 31.3 18.5 3.7 26.2 12.1 0.01 0.09 0.07 0.12
0912-11 31.3 9.9 0.8 13.5 6.4 0.01 0.05 0.04 0.06
Average 73.0 16.1 2.0 24.6 11.7 0.01 0.09 0.07 0.11
Rapu-Rapu Mine
1123-04 594.7 16.1 6.1 70.6 36.1 0.04 0.28 0.19 0.23
1123-05 344.3 14.8 5.7 49.5 24.7 0.03 0.19 0.13 0.17
1123-08 350.6 19.8 9.3 60.1 29.5 0.04 0.23 0.16 0.22
Average 429.9 16.9 7.0 60.0 30.1 0.04 0.23 0.16 0.21
Philex Mine
TSF3-A 250.4 27.2 9.3 59.8 28.7 0.04 0.22 0.16 0.23
TSF3-B 281.7 19.8 11.0 57.1 27.6 0.03 0.21 0.15 0.21
TSF3-C 281.7 24.7 11.4 62.6 30.1 0.04 0.23 0.17 0.24
Average 271.3 23.9 10.6 59.9 28.8 0.04 0.22 0.16 0.23
Worldwide Average 1
412 33 45 - - - -
1 worldwide radionuclide average from UNSCEAR, 2010.
Conclusions
In this study, the concentrations of 15 PTEs (As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Sn, Tl, V, and Zn) and the concentration activities of natural radionuclides (40K, 238U, and 232Th) were determined in the representative mine waste samples from selected legacy and active mines in the Philippines to assess the potential effects of these mine wastes to the natural environment and to the human health. The main findings of the study were:
Mine wastes from selected legacy mines (PIM, BM, RRM) have higher concentrations of PTEs than the mine tailings from an active mine (PM).
Several PTEs contents of legacy mine wastes are higher than the average UCC composition and the Canadian soil quality standard.
Legacy mine wastes are more polluted by PTEs than active PM tailing. Based on the EF and Igeo
values, legacy mine wastes are strongly polluted by As, Cd, Cu, and Mo. Aside from that, BM and RM wastes are polluted by Pb, Sb, and Zn, PIM waste is polluted by Ni and V, and BM waste is polluted by Tl. PM tailing is only moderately polluted by Cu and Mo.
The radionuclide activity concentrations of the legacy mine wastes and active mine tailing are
below the background values except for the 40K and 238U in PIM. Radiological hazard indices are also all lower than their permissible limits except for the DR value of PIM waste. The presence of uranium-bearing minerals in the deposit could explain the high radioactivity in PIM waste.
Acknowledgements
This work was supported by the Department of Science and Technology-Philippine Council for Industry, Energy and Emerging Technology Research and Development (DOST- PCIEERD) and the Department of Science and Technology- Grants-in-Aid Program (DOST-GIA). We like to thank the Municipal Environment and Natural Resources Office (MENRO) of Jose Panganiban, Camarines Norte, the Mines and Geosciences Bureau-Regional Office No. V (MGB-V), and Philex Mining Corporation for their support to the study.
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