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Assessment of the effects of Acid Mine Drainage on Mogpog River Ecosystem,Marinduque, Philippines, and Possible Impacts on Human Communities
INTRODUCTION
Mogpog River is located in the island of Marinduque, Philippines. It used to be a relativelyhealthy river where local communities dotting its banks from Barangay Taluntunan down toBarangay Janagdong obtained fishes, crustaceans and other aquatic organisms. Harvestingthese resources were either for local consumption or for cash. The river also served as a placefor bathing, swimming, washing clothes and for farm use.
In the year 1967, Marcopper Mining Corporation, a subsidiary of Placer Dome which owns39.9% of the corporation in the Philippines (Philippine Indigenous Peoples Links, 2003),started the construction of the copper mine. The company commissioned Tapian Pit in 1979.Later, the San Antonio Pit was also opened in the 80’s to contain mine wastes. This pit served as the waste rock dump while the former pit as the tailings dump (Oxfam Australia, 2003).However, villagers complained of fish-kills and foul smells being emitted from the riverespecially after a heavy rainfall (Coumans and Nettleton, 2000).
In 1991, an earthen dam was built at the Maguila-guila Creek, the headwater of MogpogRiver to hold back the tailings which is accumulating fast in Tapian Pit. In December 6,1993, Maguila-guila dam collapsed, causing floodwater and contaminated silt to race downthe Mogpog River. Then, in the year 2001 Placer Dome left the Philippines (OxfamAustralia, 2003).
During the 1993 dam collapsed, about twenty-one (21) barangays in the Municipality ofMogpog were buried in mud and toxic floodwaters. Agricultural crops and various householditems and merchandise were swept away by the swiftly moving mud (Asuncion, 2001). Theraging water also swept away aquatic organisms and destroyed human habitations along itspath. Farms were also covered by mud (Coumans and Nettleton, 2000).
On August, 2000, researchers of INECAR visited Mogpog and confirmed the phenomenon ofAcid Mine Drainage (AMD) occurring in the river. It was also observed that contaminatedwater drips from the dam into a tunnel just below the dam and allowed to flow into a canalconnected to Mogpog River. Because of the acidic condition of the river, the localgovernment provided a footbridge where the people can safely cross.
The damage to Mogpog River and the local communities within the vicinity of the river washuge and its impacts are still being felt even ten years after the dam collapsed. For instance, aformer productive ricefield in Mogpog was abandoned after the dam collapsed in 1993because it could not anymore grow crops after it was covered with silt coming from the dam.Only few patches of grasses dot some parts of the land. Figures 1a and 1b show thecondition of the abandoned ricefield in Mogpog.
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On June, 2004, a study on the sediments and biological indicators of pollution was conductedin Mogpog River by a team from the Institute for Environmental Conservation and Research(INECAR) of Ateneo de Naga University. Another team for the water quality analyses,organized by Dr. Alan Tinggay from Australia, joined INECAR. Funds were provided byOxfam Australia. This report however will only deal with the INECAR study. A separatereport for the water quality was also prepared by Dr. Tinggay (2004).
Objectives
The purpose of the present study is to find out the extent of the damage resulting from the pastmining operations of Marcopper Mining Corporation. The researcher intends to relate acidmine drainage (AMD) already occurring in the area with the biophysical condition of MogpogRiver. Specifically, the study focuses on a) heavy metal contamination of soil along theriverbanks; and the b) effects of AMD on living organisms through indicator species.
Figure 1a. Abandoned ricefield (left) in Mogpog after the dam collapsed and mud(silt) covered it in 1993. Figure 1b. A close-up picture of the reddish orange siltishown at right. (Photo by E.G.Regis, 2004)
1a 1b
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METHODS
Data gathering was done in June 18 to 21, 2004. A second trip was also conducted inSeptember 12 - 14 of the same year to validate some of the results obtained from pollen grainanalysis of an indicator species Stachytarpheta jamaicensis. In addition, phytoplanktondiversity was included in the study due to the presence of some species in the acidic portion ofMogpog River.
In this research, two study sites were covered: a) Mogpog River and b) Dawis River. Thelatter served as a reference river and considered as the control site to ascertain that heavymetal pollution did not happen naturally but as a result of mining activities. It also providedthe bases for determining impacts on soil and on two biological indicators. Figure 2 showsthe location of the two Study Sites in the Island of Marinduque.
Site 1
Site 2
Figure 2. Sampling Stations (Stn) in Study Sites 1 (Mogpog River) and 2 (Dawis River).Note the steep terrain of the island clearly shown in the PCGS map from NAMRIA.A legendis provided at the lower left of the map. A location map of Marinduque is shown at the left.
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A. Determining the Control/Reference Site
This portion was made through vegetational analysis involving weeds. Weeds are gooddeterminers of similarities between two or more areas because these plants are cosmopolitanin nature and they have the ability to thrive in a variety of environment including highlydisturbed ones.
In this method, the weed composition of two sites was compared in terms of speciesrichness using Sorensen’s Coefficient of Similarity (CCs) as published in Brower et al. (1990). A value of above 50% species similarity based on Regis and Lagunzad (2002)considered the sites as comparable. The 50% limit was applied in consideration for thelikely magnitude of the disturbance such as what happens in many mining sites wheredisappearance of species is a normal occurrence. In order to discount the possibility ofdeviating too much from the local conditions, the sites have to be located in the same island,facing the same cardinal point (north, south, east or west) and that normal human activitiesconducted are also similar except for the activity in question which is mining in this study.
Species determination is normally by the presence of flowers. In the absence of suchfeature, the gross structure becomes the basis and this includes leaf forms and type, stem(herbaceous or woody), clustering appearance, growth form, and other features that canshow that the plant is a different species from the others already identified.
The results of the vegetational analysis on weeds showed that Mogpog River and DawisRiver are comparable by 59.7%, thus, Dawis River could be used as a reference river for thestudy. It was also observed that more weed species are found in Station 1 (mouth) than inStation 3 (Barangay Bocboc) along the banks of Mogpog River. A table comparing theweeds thriving in the riparian habitats of Study Sites 1 and 2 are presented in Annex 1.
B. The sampling stations
There were 5 sampling stations (labeled Stations 1 –5) in Mogpog River and 3 samplingstations in the reference river which is Dawis River (Figure 2). Station 1 is located at themouth of the river. Subsequent stations are located progressively at higher elevation thanthe preceding. In these stations, three types of samples were collected:
a) Soil samples from two locations in each of the sampling stations: water edge and at 15–20 meters from the water edge;
b) Flower buds gathered only in Stations 1 –3 of both sites since there were noStachytarphetal jamaicensis encountered in Station 4 and 5 of the Mogpog River;
c) Phytoplankton samples from 1 sampling station (Station 3) within Mogpog river and 1sampling station at the mouth of a tributary for comparison.
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C. Heavy metals in soil
One composite sample from 30 randomly collected 1-kg soil samples were obtained fromeach sampling station in each study site. The samples were collected from two locations: a)at the water edge of the riverbank, and b) from about 15 –20 meters away from the wateredge. These samples were obtained from 20 cm below the soil surface. The compositeswere air-dried and then brought to the University of the Philippines Natural ScienceResearch Institute (UPNSRI), Diliman, Quezon City. Chemical analyses of the soils wereon arsenic, lead and cadmium content. The method of analysis was by Atomic AbsorptionSpectrophotometry (AAS).
The choice of heavy metals for chemical analyses of soil was guided by the following:
1) People complained of darkening of skin on toes when they regularly cross the riverand suspected that this may be due to the presence of arsenic (As).
2) Published literatures show lead (Pb) in blood samples taken from affected childrenresiding near Calancan Bay.
3) Cadmium (Cd) was chosen because it is a natural constituent of copper and gold oresin sulfide rocks and because of its property of being easily absorbed by plants.
Other metals were not included due to limited funds. The presence of Copper (Cu) at abovethe natural level was assessed based on other studies such as those of Dr. Alan Tinggay(2004), the USGS-Armed Forces Institute of Pathology report (May, 2000), an initialinvestigation conducted by INECAR of Ateneo de Naga University (Regis, 2002) and theresults of chemical analyses on arsenic, cadmium and copper for the indicator speciesStachytarpheta jamaicensis in this present study.
In the initial investigation conducted by INECAR earlier, an acidic blue water was observedin one of the braids of channels of Mogpog River. This indicates the presence of coppersulfate (Vugteveeen, http://www.elmshurst.edu/~chm/vchembook/334raymine.html).Tailings spills that happened in the area would possibly contaminate the soil and sedimentswith significant amount of this metal. The water quality assessment by Dr. Alan Tingaycontained in the Marinduque Scientific Report show elevated levels of copper in the damand some stations downstream. The USGS-Armed Forces report by Plumlee, et al. (2000)also mentioned high levels of copper in Mogpog River.
D. Other parameters measured were soil pH and characteristics such as soil color, soiltexture and drainage potential. Soil pH was determined using the method of Heckman(1994). An average of three readings were recorded for each sampling station per studysite. Soil type was determined by the Hand method (DeLuca & O’Herron, 2002).
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E. Impacts on living organisms through Biological Indicators of environmental pollution
E.1. Pollen Grain Analysis
Thirty flower buds were collected from an indicator species Stachytarpheta jamaicensis(Figure 3a) in each sampling stations of both study sites. Pollen grain analyses were doneto determine pollen abortiveness that quantifies heavy metal contamination in the methodsof Regis and Lagunzad (2002) and Micieta and Murin (1996). An example of the pollengrain of S. jamaicensis taken through a microscope camera is presented in Figure 3b. Cropplants were not anymore observed included in the study since these were not anymoreobserved in the sampling areas.
Pollen grain analysis comprised of processing and counting of normal and aborted pollengrains. The former included acidifying, squashing and staining. Then, the pollen grainsfrom the two anthers of each flower bud were counted under a compound microscope usinga prepared horizontal grid placed at the back of each prepared slide. Thirty flower buds persampling station per site were processed and their pollen grains counted.
E.2. Heavy metal pollution in plants
Whole plants were gathered, washed in distilled water and air-dried or oven dried at 50 -60°C in a drying oven. Homogenization through pounding and grinding followed, then thesamples were brought to the University of the Philippines Natural Science ResearchInstitute (UPNSRI). The samples were analyzed for arsenic, cadmium and copper usingAtomic Absorption Spectrophotometry (AAS).
Figure 3a. The indicator speciesStachytarpheta jamaicensis usedin pollen grain analyses. [Photo byE.G.Regis, 2004]
Figure 3c. Normalpollen grain of S.jamaicensis [Photo byE.G.Regis, 2004]
F lo w e r b u d
F lo w e r e tFigure 3b.Flower spike of S.jamaicensis [Photoby E.G.Regis, 2004]
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E.3. Phytoplankton study
Phytoplankton study was included because there are known resistant species in acidicwaters. The purpose of using the phytoplankton as indicator species was to determinespecies richness and the presence/absence of phytoplankton species thriving in MogpogRiver compared with one of its tributaries.
The phytoplankton samples were collected at Station 3 in Mogpog River and in one of thetributaries of the said river. Other stations were not included since station 1 is located at theriver mouth and marine phytoplankton mixes with freshwater types. Station 2 is located atlower elevation downstream and receives several tributaries that possibly increasebiodiversity. The method used for sample collection was adapted from Waterwatch (2003).
RESULTS
The results of the study are presented in three sections: A. Soil/sediment characteristics, B.Soil pollution, and C. Effects on living organisms through indicator species. Soil/sedimentcharacteristics have a bearing on the physico-chemical characteristic conditions of the soiland/or sediments that include acidity/alkalinity and drainage potential indicated by their colorand texture. Movement of toxic heavy metals is influenced by these characteristics.
A. Soil/sediment characteristics
A.1. Soil pH
Soil pH is the degree of acidity or alkalinity that measures reactivity of soil. Figure 4 aboveshows that soils in Mogpog riverbank become more acidic from Stations 1 to 5. Also, the pHof soil is also more acidic at locations 15 –20 meters from the water edge of the river thanalong the water edge. The increasing pH (becoming more alkaline) from Station 5 goingdownstream towards Station 1 is most likely due to dilution by fresh water from the differenttributaries received by Mogpog River. In addition, marine contribution during high tides alsoincreased the water pH, thus also the sediment and soil along the riverbanks. Nevertheless,this trend of decreasing pH (more acidic) from Station 1 to 5, can be attributed to acid minedrainage originating from the dam upstream.
Figure 4. Comparison of soil pH in 2locations along Mogpog riverbank
7.5
6.3
3.2 2.9 2.7
7.1
4.8
3
012345678
St 1 St 2 St 3 St 4 St 5Stations
pH
Near wateredge
15-20 m fromwater edge
8
Figure 5. Comparison of soil pH in 2 locationsalong Dawis riverbank
8 8 88 87.9
7
St 1 St 2 St 3
Station
pH
Water edge
15-20m fromwater edge
In the reference river (Figure 5), the pH of soil is alkaline which is the same in all stations forsediments near the water edge. The condition is also true for sediments obtained 15-20meters from the water edge except in Station 3, which has a slight decreased in pH value by0.1. Nevertheless, the value still shows alkaline condition, which is due to the presence ofcalcium carbonate in rocks as evidenced by the presence of remnants of fossilized corals andshells in the area. This is also confirmed by the study of Tinggay (2004) on the level ofcalcium in water. The slight decrease in the pH may have resulted from the presence ofvegetation and decomposing plant and animal remains in the area. Decomposition of organicmatter forms humic acid, a soil forming process.
Figure 6. Comparison of average soil pH ofMogpog and Dawis riverbanks
0
2
4
6
8
10
St 1 St 2 St 3 St 4 St 5Station
pH
MogpogDawis
Comparing the average pH of soil in the two study sites (Figure 6), Dawis riverbank isalkaline in all station whereas Mogpog riverbank shows decreasing trend (becoming moreacidic) from Station 1 to 5 towards the dam. Thus, acidity can be attributed to acid minedrainage generated in the siltation dam upstream.
A.2. Soil color
Soil color is the product of various chemical, biological and physical transformations thattakes place within a soil. Biological processes bring about the soil organic matter or (SOM)that imparts darkening of soil color to brown and black, thus, higher the organic matter, thedarker the soil. On the other hand, bright/light color indicates leaching of oxides of iron andaluminum, calcium, carbonates and/or clay minerals (Fanning and Fanning, 1989). Table 1below compares the color of soils obtained from the study sites.
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Table 1. Soil characteristics based on colorSampling Locations
Site I Mogpog Site 2 DawisStudy Site
and StationsWater Edge 15 –20 m from
water edgeWater Edge 15 –20 m from
water edgeStation 1 Brownish gray Dark Gray Gray to dark gray Dark grayStation 2 Yellowish brown Light brown Gray to dark gray Dark grayStation 3 Yellow to light orange
brownLight orangebrown
Gray to dark gray Dark gray
Station 4 Near Tunnel–Lightorange brown
* * *
Station 5 Dam–Light orangebrown
* * *
FormerRicefield
Open area–orangebrown
* * *
* no sampling station applicable
In the above Table, only the riverbanks of Dawis River and in Station 1 of Mogpog River atlocation farther from the water edge show dark soil color. The lighter color of soil meanswell-drained condition. Thus, in Mogpog River, carbonates and/or clay minerals have beenleached out due to the acidic condition of the soil whereas in Dawis River, the darker soilcondition indicates the presence of organic matter. This condition is confirmed by the studyof Tingay (2004) regarding the leaching of metals and minerals due to acid mine drainage. Inhis study, Calcium, Magnesium, Sulfates, Copper, Potassium, Iron and Zinc in water are highin the dam (Station 5 in this study) decreasing towards the lower elevation.
A.3. Soil Texture
The amount of sand, silt and clay in a soil provide the bases for textural classification of asoil/sediment sample (Fanning and Fanning, 1989). It can also be determined by a simplemethod known as Soil Texturing by Hand (DeLuca and O’Herron, 2002). Table 2 below presents the results of soil characteristics analysis of Mogpog and Dawis riverbanks.based ontexture.
Table 2. Soil characteristics based on texture.Sampling Location
Site I Mogpog Site 2 DawisStudy StationWater edge 15–20 m from
water edgeWater edge 15–20 m from
water edgeStation 1 Sand Sand Sand Loamy sandStation 2 Sand Fine sand Sand Loamy sandStation 3 Silty Fine sand Sand Sandy loamStation 4 Silty clayey * * *Station 5 Silt * * *Former Ricefield Mud/silty * * *
* no sampling station applicable
Stations 1 and 2 of Mogpog and Station 1 to 3 of Dawis along the water edge are sandy, thus,there is high drainage potential of soils in these locations. In contrast, Stations 4 and 5 ofMogpog showed silty and clayey soils which have low drainage potential but high adsorption
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capacity for minerals such as heavy metals. These areas are near the tunnel below the damand the dam itself respectively. Acidic condition tends to remobilize the heavy metals anddeposit them to lower levels. This is one of the problems of acid mine drainage.Nevertheless, the best texture for a balanced water retention and drainage potential is sandyloam and loamy sand found in Dawis River at 15–20 meters from the water edge.
Fine and medium-textured soils have high retention of water and exchangeable nutrients.Coarse-textured soils (large soil fragments) however have large pores, thus, percolation ishigh because they have very weak water-holding capacity. Thus, this type of soil have lowwater retention due to their rapid infiltration rates. On the other hand, when pores are fine,water is strongly adsorbed by forces that exceed gravity (Fanning and Fanning, 1989).Because it is retained in the soil, water becomes unavailable to plants. Medium-sized poreshowever have high water availability. In addition, the adsorption of cations (nutrients) andmicrobial activities are also dependent on surface area of soils.
B. Heavy metals in Soil
Annex 2 shows the level of heavy metals in soil/sediment samples obtained from variousstations at the banks of Mogpog River, the tunnel and the dam. These results are presented inbar graphs in Figures 7 through 12. Reference standards are also presented in Annex 3.
B.1. Arsenic in Soils
Figure 7. Comparison of Level of Arsenic inSediment in 2 locations along Mogpog
Riverbank
0
1
2
3
4
5
6
7
8
9
10
1 2 3 4 5
Station
mg
/kg
Water edge
15-20m fromwater edge
In the above Figure, Stations 1 and 2 of Mogpog River show higher values of arsenic insampling stations located away from the water edge. Lower value is however shown instation 3 at this location. At the water edge, only station 2 recorded higher value than theother stations. It is possible that arsenic is deposited in this station due to its lower elevationthan stations 3 to 5. The higher value in Station 2 at the water edge may be due tocontribution from other sources. In station 1, the lower value at the water edge may havebeen due to sediment deposited from the marine environment.
From stations 4 going downstream, acidic water and soil might have remobilized the arsenicand deposited it at lower elevation. Arsenic in sediments at location farther from the wateredge, also increases going downstream. This may be due to higher pH which is alkaline thatdecreases remobilization of heavy metals.
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In Station 5, which is the dam, the slight increase in level of arsenic may be due to the factthat arsenic in the tailings are still present in higher quantity. The acidic condition of thewater may have caused the movement of some arsenic to station 4 at the tunnel. Thus,sediments from the tunnel are only recipients of the metal carried by the acidic water.
There is also the possibility that the transfer of dissolved arsenic from station 5 to 4 through awater medium caused some of the metal to be released into the air. However, from stations 4to 2 towards the coast, there seems to be a gradual deposition of arsenic.
Another source of arsenic may be human activities such as the use of pesticides in farms andother sources due to the presence of human communities in stations 1 to 3. Nevertheless, thetrend between Stations 4 and 5 shows that the source of arsenic is the dam upstream.
Figure 8. Comparison of level of Arsenic insediments in 2 locations in Dawis riverbank
0
1
2
3
4
5
6
7
St 1 St 2 St 3
Station
mg
/kg
Near wateredge
15-20 m fromwater edge
In Dawis river, the trend among the stations, show higher arsenic level at locations away fromthe water edge. This shows that arsenic tend to remain in the same location. Since the pH ofsoil is alkaline, there is less remobilization of arsenic in this location, hence, arsenic content insediments are higher at locations away from the water edge. The higher level of soil arsenic instation 1 can also be due to other factors such as human activities that use products containingarsenic. At the water edge, the increasing trend towards the coast shows that arsenic is beingcarried by the acidic river downstream and deposited there. Nevertheless, the values aremuch lower than the critical values for arsenic which is 20 mg/kg.
Figure 9. Comparison of average level of Arsenicin Mogpog and Dawis riverbanks
0
2
4
6
8
10
St 1 St 2 St 3 St 4 St 5Station
mg
/kg
Mogpog
DAwis
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In comparing the two rivers, Mogpog riverbank has higher average content of arsenic thanDawis riverbank. The trend shows increasing level of arsenic towards the coast due todeposition of the metal downstream. The exception is Station 5 of Mogpog which is the damand the most likely source of arsenic.
B.2. Lead in Soils
Figure 10. Comparison of level of Lead in 2locations in Mogpog riverbank
0
10
20
30
40
50
St 1 St 2 St 3 St 4 St 5Station
mg
/kg
Near wateredge
15-20 m fromwater edge
Very high level of lead was recorded for soils in Station1 of Mogpog River. There is also anincreasing trend of the level of lead in soils from Stations 2 to 5 near the water edge andStations 1 to 3 at 15–20 m from the water edge. This shows that the source of lead comesfrom the dam upstream. Higher content of lead in Station 3 at location farther from the wateredge than at the water edge indicates that lead is slowly being deposited in this area.
Lead (Pb) has been reported to be the least mobile among the heavy metals. It is alsoassociated mainly with clay minerals. This is probably the reason why Pb is high in the Damdue to the silty and clayey condition of the soil there. On the other hand, high soil pH canprecipitate Pb as hydroxide, phosphate or carbonate (Kabata-Pendias and Pendias, 1984p.155). Again, this explains why Pb content of soil is highest in Station 1 of Mogpog Riverbecause aside from the contribution from the siltation dam, the high level of lead in Station 1near the water edge may be due to human activities that use lead such as fuel used in vehiclesincluding motorized boats since this station is along the mouth of the river. True trend ofvalues is shown in sediments at location away from the riverbank wherein deposition is lessinfluenced by water contaminated with lead coming from anthropogenic activities.
Figure 11. Comparison of level of Lead in 2locations in Dawis riverbank
0.0
2.0
4.0
6.0
8.0
10.0
St 1 St 2 St 3
Station
mg
/kg
Near wateredge
15-20 m fromwater edge
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Dawis riverbank also shows the same trend as Mogpog River. There is higher level in Station1 than the other stations and increasing level of lead from Station 2 to 3, which is goingupstream in both locations - near the water edge and at 15-20 m away from the water edge.The high level of lead in Station 1 may be due to anthropogenic sources. Nevertheless, thelevel of lead in the reference river is much lower than Mogpog river.
Figure 12. Comparison of average level of Lead inMogpog and Dawis riverbanks
0.0
5.0
10.0
15.0
20.0
25.0
St 1 St 2 St 3 St 4 St 5
Station
mg
/kg
Mogpog
Dawis
Figure 12 compares the average level of lead in soil along Mogpog and Dawis riverbanks.The results show trend of increasing levels of lead from downstream to upstream in the damexcept for Station 1. Nevertheless, the trend shows that although lead is naturally occurring inthe area, its higher values in Mogpog means that lead content of sediments have beenremobilized by acidic water due to mining activities.
B.3. Cadmium in soils
Although cadmium was also measured in soil samples, its level is below the detection limit ofthe analytical laboratory (Annex 2). Water quality assessment by Tingay (2004) shows verylow level of cadmium in water in the dam, at the tunnel below the dam and some stationsdownstream. Thus, adsorption in soil particles is also low. Nevertheless, there is a decreasinglevel of cadmium in water from the tunnel below the dam towards station 3 downstream andthis indicates mobilization of cadmium due to the acidic water which may in time, causeincreased adsorption by soil particles enough to be detected later on.
C. Effects on living organisms through indicator species
When a certain living organism responds to a particular environmental condition, it is knownas a biological indicator or bioindicator. Kovacs (1992) listed several factors that elicit suchresponses and these are: a) genetic make-up, b) stage of development, c) changes inenvironmental conditions, and d) concentration of pollutants.
In this study, two bioindicators are considered: a) a stage of development in an indicatorspecies and b) changes in environmental conditions. In the former, the indicator speciesStachytarpheta jamaicensis was used because it has certain tolerance to pollution near miningsites and aborts its pollen grains in the presence of heavy metals (Regis, 1999; Regis et al.,2001). This species is an effective test organism because it is able to provide quantitative
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response to exposure to the pollutant. The second indicators are the phytoplankton (Kovacs,1992) because they are able to provide qualitative response to changes in environmentalconditions.
C. 1. Pollen grain abortiveness of Stachytarpheta jamaicensis
Pollen grain abortion above the natural abortive tendency of plants indicates impact on thecapacity of plants to produce fruits and for self-perpetuation. Table 3 and Figures 13 and 14below prove the effects of heavy metals on plant productivity.
Table 3. Comparison of percent pollen grain abortion of S. jamaicensisObtained along the banks of Mogpog River and Dawis River
% Pollen Grain AbortionStationSite 1 Mogpog Site 2 Dawis
Station 1 9.07 3.78Station 2 7.21 5.44Station 3 8.93 3.41
In terms of percent pollen grain abortion, Site 1 (Mogpog) has higher percentage of abortingpollen grains than Site 2 (Dawis) in all stations. ANOVA confirmed the significantdifferences in pollen grain abortion between Mogpog and Dawis study sites. In the former,Station 2 has lower mean pollen abortion than Stations 1 and 3 which are the mouth(connected to the sea) and upstream (nearer the dam) respectively. As noted in the soilanalysis, Station 1 may be influenced by other factors that originate from human settlements,thus, this station receives additional amounts of heavy metals such as lead from vehicularsources causing an increase in pollen abortion. Nevertheless, Stations 2 and 3 of Mogpogriver shows an increasing trend towards upstream in pollen abortiveness.
Figure 13 below presents various examples of aborted pollen grains of S. jamaicensis in thestudy sites.
a b t
n r m
abtnrm
nrm
abt
Figure 13. Aborted (abt)and normal (nrm) pollengrains of the bioindicatorspecies Stachytarphetajamaicensis collected fromthe banks of Mogpog River(Photo by E.G.Regis)
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The following Figures 14 to 19 also categorized the pollen abortiveness by groups accordingto a range in pollen abortion. This is a graphical presentation of the trend of pollen abortionin the indicator species found in both sites and in all stations. In each station, 30 flower budswere processed and counted. Figures 14 to 16 present the results from Mogpog River.
Figure 14. Percent pollen grain abortion ofStachytarpheta jamaicensis by category in
Station 1 Mogpog riverbank
53.33
30.00
10.00
6.67
0 20 40 60
Cat
ego
ry
% Pollen abortion
Above 45%
15.1-45%
5.1-15%
0-5%
Station 1 of Mogpog shows high percentage of pollen grain abortiveness within the naturalrange of 0 –5%. This findings is due to the low level of heavy metals found in soil in thisstation. Also, the plants in this place grow in an elevated area, thus receives less heavy metalcontaminants.
In Station 2 of Mogpog, the above figure shows a shift in the increase in pollen abortiontowards a higher range (5.1% to 10%) which is above the natural pollen abortiveness. Lowercategory (% at natural level) also decreased. There is also a decreased towards the highercategory. This findings indicate increase in the level of heavy metal contaminant, thus, higherpercent pollen abortion.
Figure 16. Percent pollen grain abortion ofStachytarpeta jamaicensis by category in
Station 3 Mogpog riverbank
13.33
76.67
10.00
0 20 40 60 80 100
Cat
eto
ry
% Pollen abortion
15.1-45%
5.1-15%
0-5%
Figure 17. Percent pollen grain abortion inStachytarpheta jamaicensis by category in
Station 1 Dawis riverbank
83.33
10.00
6.67
0 20 40 60 80 100
Cat
ego
ry
% Pollen abortion
15.1-45%
5.1-15%
0-5%
In Figure 16, Station 3 of Mogpog River shows highest pollen abortiveness at category 2(5.1-15%) which is above the natural pollen grain abortiveness. Natural pollen abortivenesshas decreased further. Note that Station 3 is located at higher elevation and nearest theMaguila-guila dam which is the source of the contaminant of Mogpog River. Figures 17 to19 presents the results from Dawis River, the reference/control site.
Figure 15. Percent pollen grain abortion ofStachytarpheta jamaicensis by category in
Station 2 Mogpog riverbank
43.33
46.67
10.00
0 20 40 60
Cat
ego
ry
% Pollen abortion
15.1-45%
5.1-15%
0-5%
16
Figure 19. Percent pollen grain abortion ofStachytarpeta jamaicensis by category in
Station 3 Dawis riverbank
73.68
10.53
15.79
0 20 40 60 80
Cat
ego
ry
%Pollen abortion
15.1-45%
5.1-15%
0-5%
In Figures 17, Dawis River, most of the samples showed natural pollen grain abortiveness.However, some samples exhibited very high abortive tendencies. This condition might be dueto contribution of pollutant from other sources such as vehicular exhaust, batteries andpesticides. The sampling area is also a very shallow river (Figure 4g). Thus, pollutants mayhave been concentrated here by clay particles in a predominantly sandy soil in this site.
The results presented in Figure 18 shows more than 50% of the samples are within the naturalabortive range. However, there are also more than 40% exhibiting higher than natural pollenabortiveness. Some values were even above 15%. These results may be attributed to thepresence of human habitations and farms near the sampling area, thus, some human activitiescould have contributed to heavy metal pollution.
On the other hand, Figure 19, Station 3, shows that pollen abortion is mostly within thenatural abortive range. Very few flower buds exhibited higher than natural and the valueswere not so high. The sampling area is in a peaceful place with crystal clear water flowingand not much disturbance from human activities. Farmlands are higher in elevation andmostly composed of coconut trees.
C.2. Heavy metal pollution in Stachytarpheta jamaicensis
The levels of arsenic, cadmium and copper in the indicator species Stachytarphetajamaicensis are presented in Table 4 below. The results of the chemical analyses done by theNatural Science Research Institute (NSRI) of the University of the Philippines are presentedin Annexes 4a and 4b.
Table 4. Values for natural and critical levels of arsenic, cadmium and copper inplants based on Pfeiffer et al. (1988)
Content in Stachytarphetajamaicensis (mg/kg)
Heavy metal
Mogpog Dawis
NaturalContent*
CriticalContent*
Arsenic (As) 0.0852 0.0620 1.0 20Cadmium (Cd) 1.17 0.49 0.4 5Copper (Cu) 11 9.0 30 >30
* Reference values based on Pfeiffer et al. (1988; Annex 5)
Figure 18. Percent pollen grain abortion ofStachytarpheta jamaicensis by category in
Station 2 Dawis riverbank
53.33
43.33
3.33
0 20 40 60
Cat
ego
ry
% Pollen abortion
15.1-45%
5.1-15%
0-5%
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The above results show that the levels of arsenic, cadmium and copper are higher in samplestaken from Mogpog River than those taken from Dawis River, the reference site. Among thethree metals, cadmium in Mogpog was detected higher than the natural content and onlyslightly higher in Dawis. Nevertheless, all results show lower than the critical level in plantsbased on Pfeiffer et al. (1988).
However, although the current level of cadmium in soil is very low (below detection limit;Annex 5), plant samples were able to sequester this metal and concentrate it in plant tissues.This is highly possible because plants could easily absorb cadmium. Thus, the results furthershow that the contamination of soil with cadmium is also occurring in Mogpog and mostlikely due to acid mine drainage.
C.3. Effects of AMD on freshwater phytoplankton communities
River ecosystems upstream normally have very low diversity and abundance ofphytoplankton. Exception to this is when the section of the river is relatively flat therebyallowing settlements of organic matter coming from plants and animals that provide algalnutrients for phytoplankton growth. Another source of algal nutrients is the existence ofmany human settlements along the riverbanks.
In mining areas with sulfide ores, a group known as cyanophyta or cyanobacteria includesspecies known to use sulfur for metabolic functions even in low level oxygen or its absence.These species are termed as chemolithautotrophic (Gray and Head, 1999). Species richness ofphytoplankton recorded for Mogpog River and one of its tributary are recorded as 29 and 31species respectively. Annex 6 presents the various species and compares the phytoplanktondiversity between Mogpog River and one of its tributaries in Station 3, Bocboc Area. Theresults show that there is not much difference in species richness between an acidic river(Mogpog) and its tributary. The only difference lies on the kind of species present in the sites.
There are 12 species that are exclusively found in Mogpog River and 14 species found only inthe tributary. Since the samples were collected from the mouth of this tributary, it is expectedthat the species in the tributary will be carried by the water current to Mogpog River. Inundisturbed state, such species would survive. However, disturbance in the river such as inacidic condition, intolerant species was not be able to survive. These findings therefore showthe destructive nature of acid water on biodiversity by replacement of species and ordisappearance of species. In aquatic ecosystems, phytoplankton are also considered the baseof the food chain.
DISCUSSION
Heavy metals are naturally occurring in Marinduque. Nevertheless, in areas with no miningactivities and river water is not acidic, heavy metals are not remobilized from its source (thehighly mineralized area) to lower slopes. The naturally occurring heavy metals are also foundin small quantities in soil at the upper layers within the tolerable level of plants and animals.
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However, when mining activities open up an area exposing sulfide rocks to oxygen and water,chemical reactions naturally occur and produces sulfuric acid and iron sulfate, the latterappear as red deposits that coat rocks and sediments. This is the phenomenon of acid minedrainage or AMD. This is shown by the chemical reaction (Jackson and Jackson, 1996)below:
2 FeS2 + 7 O2 + 2 H2O 2 FeSO4 + 1 H2SO4
FeSO4 is the one responsible for the red-orange precipitate that coats rocks and sediments in ariver. The resulting sulfuric acid (H2SO4) is the substance that causes the leaching of heavymetals to the surroundings and creating a very low pH in water and soil such as whathappened in Mogpog River. The process is hastened by sulfur bacteria such as Thiobacillusthiooxidans and Thiobacillus ferrooxidans through bacterial oxidation processes (Allan, 1988in Salomons et al., 1995).
Acidic water releases and remobilizes toxic heavy metals such as copper, lead, arsenic,cadmium, zinc and others that are naturally occurring in sulfide ores. Moreover, the resultingacidic water kills aquatic organisms as well as soil organisms in the riparian habitat of theriverbank. These metals may be adsorbed by clay particles and/or deposited along the way asacidic water flows downstream. Thus, in the study of Tingay (2004) on the water of MogpogRiver, and in this study for soils and plants, although the levels of heavy metal pollution arestill low since most of the metals are still below the critical level, the deposition of suchmetals in soil particles is a grave concern. Proof of increasing deposition is shown in theincreasing level of heavy metal such as lead and arsenic from the source (dam) to lowerelevation. Even in acidic water, arsenic is even higher at the water edge than farther from thewater edge. Lead is highest at the source decreasing downslope except at the lowest elevationwhich is affected by human activities. Hence, such deposition will continue to impact livingorganisms within the vicinity of the river as well as agricultural productivity downslope.
A similar case of heavy metal deposition in sediments occurred in an abandoned mine in theIsland of Rapu-Rapu, province of Albay, Philippines. Past mining activities (from 1950s andabandoned in 1976) in one river (Pulang Salog, local translation of Red River) showed veryhigh levels of arsenic in a species of grass and a brown seaweed. This is also true for arsenicin sediments. Compared with another river (Pagcolbon) in the same island about 2 km away,although the area was mined and abandoned in the 1990s, the level of heavy metals is muchlower (Regis et al., 2001). Heavy metals were probably gradually deposited in the area overtime. Thus, it is highly probable that this phenomenon will also occur in Mogpog River in thecoming years.
In this study, the following findings show that,
a) the levels of arsenic and copper are higher in Mogpog River than in Dawis river
b) the levels of arsenic, cadmium and copper in indicator plants are higher in MogpogRiver than those from Dawis River. Cadmium was also found to exceed the naturalcontent in plants in Mogpog river.
c) acid mine drainage caused the leaching and remobilization of heavy metals from thedam to riverbanks in the lower slopes.
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d) there is gradual deposition of heavy metals in soils along the banks of Mogpog River
e) soils and plants in the riparian habitats of Mogpog River are contaminated with heavymetals. Although the present concentrations of the contaminants are still low, in timethe gradual deposition of heavy metals will cause their accumulation to concentrationsabove the critical levels that will threaten the survival of whatever is left of the livingorganisms
A. Impacts of heavy metals
Heavy metals cause a variety of physiological abnormalities in many plants. One of these isthe reduction in the uptake of water by the plants due to copper toxicity (Panou-Filotheou etal., 2001). The consequence of this is decrease rate of transpiration due to the followingeffects of copper and other heavy metals: a) reduction in the transpiring surface area Lanaras,et al., 1988, Barcelo and Poschenrieder, 1990; b) cadmium in bush bean caused reduction inthe mesophyll intercellular spaces resulting in less water diffusing to the stomata (Barcelo etal., 1988).
Leaf chlorosis is also associated with changes in structure and physiology in chloroplasts suchas reduction in the volume and number of mesophyll chloroplasts (Panou-Filotheou et al.,2001; Ouzounidou et al., 1992). The shape of chloroplast is also affected by cadmium(Barcelo et al., 1988; Ouzounidou et al., 1997) and lead (Heumann, 1987).
Heavy metals such as cadmium also cause loss of starch grains in chloroplast. Coppertoxicity damages the chloroplast limiting membrane (Taylor, 1988).
In all the above observations, the ultimate impacts of heavy metal toxicity results to reductionin the capacity to produce food by photosynthesis by plants. Thus, in soils laden with heavymetals, plant productivity suffers so that crop production becomes low. This is the reasonperhaps why in mining areas, plant growth is reduced, some plants do not thrive and only alimited number of species (only the tolerant ones) survive.
In terms of health effects, the following heavy metals have been documented to causeillnesses:
A.1. Arsenic
Based on the reports of the US Agency for Toxic Substances and Disease Registry, arsenic isknown to cause cancer that attacks the lungs, skin, liver, kidney, bladder and other organs ofthe body. Its entry into the human body is through contaminated drinking water and byingestion of contaminated food. It passes out slowly through hairs and nails. The inorganicform of arsenic in food and water is more problematic because it is also a human poison, fatalat concentration of 60 parts per million (ppm) because it damages the nerves, stomachintestines and skin. It can also decrease production of the red and white blood cells and itsknown to induce abnormal heart rhythm.(http://www.environment.about.com/library/weekly/blchem.htm?terms=arsenic; Arsenic
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Project, http://www.hvr.se/nov97/arsenic.html). In combination with other factors, such asmalnutrition and Hepatits B of affected person, the effects of arsenic poisoning becomesworse (The World Health Organization [WHO], http://www.who.int/inf-fs/en/fact210.html).
Other health effects include: thickening and discoloration of the skin, stomach pain, hearingimpairment, effects on the heart and circulatory system including the gastrointestinal systemand liver, diabetes, developmental effects, damage to the nervous system which is manifestedby tingling or loss of sensation in some parts of the body such as the limbs (EPA Office ofWater Management, http://www.epa.gov/OGWDW/ars/ars10.html; Arsenic Project,http://www.hvr.se/nov97/arsenic.html)
A.2. Cadmium
This metal has no known biological function, yet, it is readily absorbed by plants through theroot pathway which eventually reach the leaves, fruits and seeds (Johnson, BT., 1997,http://ace.orst.edu/info/extonet/faqs/foodcon/cadmium.htm). Humans become contaminatedthrough ingestion of contaminated food. In humans, cadmium has a tendency for chronicaccumulation in the kidneys wherein, at 200 mg/kg fresh weight concentration in the kidneycortex, causes kidney dysfunction (Alloway, 1995). Likewise, it is also deposited in liver. Inthe blood, cadmium binds to the erythrocytes (red blood cells). Since cadmium in the body iseliminated slowly due to its biological half-life which is 10-30 years), its impact on the bodyis metabolic dysfunction of organs affected. Diet that are low in calcium, iron or proteinenhance the absorption of cadmium in the body.
A.3. Lead
Lead contamination is brought about by inhalation of contaminated dust particles in the airand by ingestion of contaminated food. Once it enters the body, it affects the organ systemespecially the central nervous system. In children, it has been reported to cause permanentdevelopmental problems at low dose. At higher concentration, lead could interfere with theformation of red blood cells in humans as well as cause neurological disorder. Other diseasesassociated with lead include anemia, learning difficulty, decreased mental ability, anddamages to the kidney and immune system (Northwestern University,http://www.chem.northwestern.edu/~hagodwin/toxicity.html; US Agency for ToxicSubstances and Diseases Registry,http://www.environment.about.com/library/weekly/blchem2.chtm).
A.4. Copper
Copper is a trace element essential for human health. However, too much copper also causehealth problems. When there is high copper in the air at the workplace, people suffer frommetal fever that manifest as flu-like (http://www.lenntech.com/Periodic-chart-elements/Cu-en.htm). In addition, long-term exposure can cause irritation of nose, mouth and eyes,suspected to result to lowered intelligence in adolescents. Headaches, stomachaches,dizziness, vomiting and diarrhea are also experienced. High uptakes of copper may cause
21
liver and kidney damage, hepatic cirrhosis, brain damage, renal disease and copper depositionin the cornea of the eyes.
B. The causes of the problem on human health
The reality of the above findings can be explained by the geochemical-physical condition ofthe island of Marinduque. These are: a) Presence of sulfide rocks capable of generating acidin the presence of oxygen and water. This is a natural process that last for hundred of yearsuntil the sulfide rocks in the area have been dissolved. Since sulfide rocks contain otherheavy metals aside from copper in this case, the acid will remobilize the heavy metals anddeposit them in soil particles; b) Steep slope, so that even in Type III climate, rainwaterfacilitates the movement of contaminated water and erosion of sediments during the rainyseason. Type III climate is described by PAGASA as having “seasons not very pronounced, relatively dry from November to April and wet for the rest of the year”. c) Marinduque is a small island ecosystem with steep slope so that pollutants such as those coming from tailingsdump of the mines can easily be carried by runoff, river water, and flood water into themarine environment thereby affecting the fishery resources.
The danger to humans becomes highly probable because some plants are able to toleraterelatively high concentration of heavy metals. Some animals are also able to accumulateheavy metals in their tissues without causing immediate death. Thus, these realities posedanger to the unsuspecting persons because heavy metals can be transferred from soil toplants, then to animals and eventually to humans.
C. Contamination of Mogpog River
The contamination of Mogpog river was apparently a result of irresponsible method of wastedisposal. The following pictures (Figures 20 - 25) provide proofs of this observation:
Figure 20. Physical filter of the Maguila-guilasiltation dam set up by the mining company
Figure 21. A blasted portion of the damwhere overflow water from the contaminatedmine tailings flows through
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The apparent use of Mogpog River as a disposal site for the acidic liquid of the mine tailingscaused the contamination of the soil along the riverbank and its vegetation. The acidgenerated through the process of acid mine drainage leached out the heavy metals from thewaste rocks of the mines and tailings deposited in the siltation dams. Such heavy metals arecarried by the acidic water and deposited to the soil and sediments and are also carrieddownstream where they accumulate in the lower portion of the river. The deposition of heavymetals in the soil resulted in their entry to the plant bodies and affected the productivity ofplants. Moreover, the acid and the toxic metals killed most of the aquatic organisms exceptsome tolerant species of phytoplankton.
Figure 23. The lower part of the blastedportion shown in Figure 22 above. Residueof the flowing contaminated water is shownby the black coating on the rocks (redarrow) which is due to sulfur bacteria
Figure 22. Tunnel (white arrow) wherecontaminated water from the dam abovedrips into a canal which is connected to theMogpog River (yellow arrow)
Figure 24 (left). White arrow points to tunnel below the dam where contaminated wateris collected and conveyed into Mogpog River (blue arrow). Green arrow is the drainagecanal originating from the overflow of blasted portion of the dam in pictures 2 and 4above. Figure 25 (right) picture is the appearance of the red orange acidic andcontaminated water that flows from the dam.
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D. Impacts of Acid Mine Drainage
Acid mine drainage (AMD) due to mining activities releases heavy metals in the environmentwith increasing (decreasing pH) acidity. The current condition of the said river with regardsto decreasing pH of soils from the coast to the dam and the red iron deposits (including huesof orange) at the bottom and sides of the river channel show that the river is manifesting thephenomenon of Acid Mine Drainage (AMD). In the report of Dr. Alan Tingay (2004), heavymetals in Mogpog river such as cadmium, copper, iron, and zinc show trends of decreasinglevel from the dam upstream to the coast downstream indicating that heavy metals originatedfrom the mine. The values are also higher in this river than in the reference river (DawisRiver).
Likewise, there is also increasing acidity in soil from the coast to the dam. Mobility of heavymetals is facilitated by acidic condition. Arsenic for instance is remobilized from the source(dam) and deposited in soils at lower elevation. Lead in soil along Mogpog riverbank wasalso detected in the dam upstream and in other areas downstream with levels higher than thereference river. The deposition of lead and arsenic is also occurring in areas farther from thewater edge. The same occurrence is probably happening with other heavy metals such ascopper and zinc since elevated levels of these metals in water were reported in the study ofTinggay (2004) in the same river.
E. Impacts on living organisms
E. 1. Effects on Microorganisms
Microorganisms in soils are ecologically important because they are involved in energy flowand geochemical cycling of nutrients. Among the functions of these organisms in soil, thedecomposition of plant and animal tissues is the most important because their activities returnnutrients to the soil. Once degraded, the released minerals are taken up by plants and later,by consumer animals through the food chain.
In the case of phytoplankton, changing conditions in a river could cause a change in diversityof organisms. Since phytoplankton are also at the base of the food chain in aquatic habitats,this kind of change in diversity would influence the kind of organism that could thrive in thewater even if acidity has been reduced as in Station 2 of Mogpog River. In this river, thereare also species that thrive at the mouth of a tributary (non-acidic freshwater), yet were notfound in the receiving acidic water of Mogpog. This confirms the destructive nature of acidmine drainage to aquatic plants in disturbed rivers.
Aside from phytoplankton, acid mine drainage kills microorganisms except those that areresistant to acid. These resistant strains however such as sulfur bacteria may continue tothrive in the soil in the absence of other living organisms as food source and survive by usingsulfur and other minerals for metabolic activities. Such bacteria are also capable ofmethylating heavy metals. This kind of transformation makes methylated heavy metals tobecome soluble in water thereby facilitating their entry into living cells (Jackson and Jackson,1996). Once the methylated metals are inside the organism’s body, they are able to create a variety of metabolic disorders.
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E.2. Effects on higher plants
The effects of heavy metal pollution on higher plants are associated with agriculturalproductivity. For instance, the phytotoxic effects of arsenic include: sudden decrease in watermobility as shown by root plasmolysis, necrosis of leaf tips and margins, and halting seedgermination (Alloway, 1995). The danger of arsenic contamination in areas affected byAMD is that its toxicity on plants increases as the soil becomes more acidic. Another effectis shown in the present study by the indicator species Stachytarpheta jamaicensis, that heavymetals cause abortion of its pollen grains (see Figure 17). This kind of disturbance is aproblem in crop production.
Pollen grains are plant structures that house the male gametophyte (sperm cells) of floweringplants and Gymnosperms. In order that they can fertilize the female gametophyte (egg cell) ofa flower, pollen grains must have tough, resistant walls and must be produced in largenumbers to facilitate finding their specific targets during pollination (Moore et al., 1991).Reduction in number of viable pollen grains decreases chances of pollination, consequentlyreduces the capability of plants to develop fruits and seeds to continue their generation. Thisis one of the reasons why heavy metal pollution causes decrease in productivity of agriculturalland.
Stachytarpheta jamaicensis as an indicator species, not only provides evidence ofenvironmental pollution, but also ascertain that other plants could behave in the same manner.In the study by Regis et al. (2001) in Rapu-Rapu and Regis (2004) in Jose Panganiban, pollengrains of Stachytarpheta jamaicensis exhibited abortion of its pollen grains. Likewise, thelatter’s study on “Gold mining as a cause of poverty of local communities in gold mining areas” provided evidences of pollen grain abortion of crop plants such as rice throughexperimentation (Maranan and Valisto, 2003). In mining areas in Jose Panganiban, Provinceof Camarines Norte, there are also mature coconut trees that do not bear fruits. Theseexamples show that the impact of mining on terrestrial plants reflect problems in agriculturalproductivity.
Moreover, the impacts of acid mine drainage (AMD) are not confined to the water in a river.The riparian zone along the riverbanks are unique habitats for plants and animals. Acidicwater seriously affects such habitats in terms of heavy metals deposition especially in areaswith clay particles. The resulting contamination of soil with metal-rich acidic water wouldnot only kill soil fauna and microorganisms but would have a detrimental effect on fruitbearing plants cultivated by the people.
If, before mining was conducted in Marinduque, the riparian habitat was a source of fertilesoil and sufficient supply of fresh water for raising short term crops, after mining, thedestruction of the river by AMD deposits toxic heavy metals and prevents the use of suchwater for the same purpose. For instance, copper can be absorbed by plants through activeand passive transports (Kabata-Pendias and Pendias, 1984). In passive absorption, the metalin solution may be more likely within the toxic range. Excess copper causes the followingphysiological problems in plants: 1) tissue damage and elongation of root cells; 2)permeability of cell member becomes altered causing leakage of ions such s potassium andphosporus in roots; and 3) inhibition of photosynthesis. Downstream, even with a reduced
25
acidity, high levels of heavy metals have been deposited since they are also detected at lowerelevation and near the coast.
F. Future Impacts
Based on the results of this study, the following scenario in the future can be expected inMogpog river ecosystem:
1. Contaminated tailings from the dam and beyond it will continue to be depositeddownstream during heavy rainfall and threaten human habitations and livelihood
2. The increased level of heavy metal pollution in soil and plants may reach above thecritical range. This situation will be brought about by continuous deposition of thepollutants through water transport downstream where human settlements areconcentrated, by wind as dust during the drier months, or by horizontal movement ofthe metals from the water edge spreading inward in the riparian zone where peopleplant their crops.
3. Reduction in agricultural productivity due to toxic effects of heavy metals in soil andplants. This event will likely occur because of increasing acidity of soil from thewater edge towards the riparian zone. Similarly, the increasing acidity will kill soilorganisms (micro and macro) that are responsible for facilitating the release ofnutrients from organic matter in the soil.
4. Reduction in the productivity of fishing grounds within the vicinity of the outfall ofMogpog River. Siltation is the major hazard that will cause fish kills by burial orchoking of aquatic organisms. Toxic level of heavy metal will finish off the rest of theorganisms that survived siltation and those that happen to visit the place.
5. Heavy metals in fishery resources will spread to other marine organisms via the foodchain. In time, major fishery resources will accumulate toxic metals in their bodiesand can also reach man through the food chain pathway.
6. The increased level of toxic heavy metals that might accumulate in people may causea variety of health problems experienced by people. Similarly animals, especiallylivestock and domestic non-food animals will show symptoms of health problems.Accumulation of heavy metals in the body will be brought about by the movement ofmetals through the food chain, or through regular drinking of contaminated water fromthe river or wells near Mogpog River. The increased concentration of metals in thebody is due to the fact that most metals such as cadmium, lead and mercury attach tothe sulfur of the protein cysteine, a natural constituent of the body (Fergusson, 1990).Although naturally low in concentration, Cadmium may pose another serious healthproblem because it is absorbed readily but is eliminated slowly in the body (Agencyfor Toxic Substances and Disease Registry Division of Toxicology, 1999)
Other observations in Mogpog river system show that silt and deposition of tailings comingfrom the dam will continue to happen during heavy rainfall due to the huge volume of tailingsthat have accumulated and continually fill up the Maguila-guila dam.
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V. CONCLUSION
Acid mine drainage (AMD) that is brought about by natural processes in the siltation dam, awaste dump of Placer Dome-Marcopper Mines, is the most possible cause of pollution anddestruction not only of the river water in Mogpog, but also of the soils in the riparian habitatsin the riverbank. Heavy metals leached out by AMD also caused loss of productivity of plantsthrough pollen grain abortion. It also altered the plankton composition of the river.
Acid water leached out heavy metals from the dam and deposited them into the lower reachesof Mogpog River. This fact cannot be denied because wastewater that drips into the tunnelbelow the Maguila-guila siltation dam and those that overflows from the siltation dam havebeen channeled into Mogpog River for disposal as well as to ease pressure build-up from thedam especially during the rainy season. Thus, heavy metals will continue to accumulate inthe river ecosystem unless remediation can successfully be implemented. To date however,there is still no remediation of AMD under the present technology. All recommendations arestill based on experimental procedures and no success stories have been shown under actualfield condition in affected mine sites in tropical countries like the Philippines. In additionexperimental remediation have not included the impacts on human communities in terms ofhealth and sustainable livelihood not connected with mining activities.
The future scenario therefore is bleak for the people of Mogpog and other villages that settledalong the riparian zone of the river unless rehabilitation of the river to its productive conditioncan by done by the company responsible for this mining disaster. With the destruction of theMogpog River ecosystem, and the impending disaster that looms ahead from the huge amountof tailings still waiting to go down from the waste dumps in the mining area, no amount ofmoney can compensate for the ecosystem destruction brought about by irresponsible miningand what the people will endure for a long long time.
Prepared by:
EMELINA G. REGIS, Ph.D.April 18, 2006
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