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BRITISH GEOLOGICAL SURVEY

TECHNICAL REPORT WC/96/61/R Overseas Geology Series

Mercury and other heavy-metal contamination associated with gold mining in the Agusan river catchment, Mindanao, the Philippines

N.Breward British Geological Survey, Minerals and Geochemical Surveys Division, Keyworth, Nottingham, UK.

A report prepared for the Overseas Development Administration under the ODA/BGS Technology Development and Research Programme, Project R6226.

ODA classification Subsector: Geoscience Theme: Identify and ameliorate minerals-related and other geochemical toxic hazards Project title: Mitigation of mining-related mercury pollution hazards. Project Reference: R6226

Bibliographic reference: Breward, N. 1996. Mercury and other heavy- metal contamination associated with gold mining in the Agusan river catchment, Mindanao, the Philippines. British Geological Survey, Overseas Geology Series Technical Report WC/96/6 l/R, Keyworth, Nottingham, UK.

Key words: gold mining, mercury, Mindanao, Philippines

Cover illustration: Small-scale amalgamation with incrcury i n pan. (T.M.W illiams)

Synopsis

An assessment of mercury (Hg) contamination and possible human exposure and environmental damage associated with artisanal gold mining in the catchment of the Agusan River in eastern Mindanao, the Philippines, was undertaken by the British Geological Survey (BGS) in collaboration with the Philippines Mines and Geosciences Bureau (MGB). Funding was provided by the UK Overseas Development Administration (ODA) under Technology Development and Research (TDR) programme R6226: Mitigation of Mining- Related Mercury Pollution Hazards.

The study aimed to ascertain the mercury contents of stream water and stream sediment in the Agusan catchment especially in those areas which have been subject to very rapid and largely unregulated growth in small-scale artisanal gold mining over the last ten years following the discovery of rich gold deposits in the area. The typical low-tech. mining and extraction methods, using amalgamation with liquid mercury as a means of concentrating fine gold, are hazardous both to the health of the miners and the general environment. Several cases of severe mercury poisoning and a number of fatalities have been recorded, mostly from the inhalation of Hg vapour during ‘torching’. i.e. evaporation of Hg amalgam to recover the gold. The wider environmental and long-term consequences of the use of Hg in the area are not so well characterised.

In this study, samples of stream water and sediment were taken from a large number of sites in the Agusan catchment, both from known mining sites such as Oiwalwal and areas well away from these to establish peak and background levels, and downstream dispersion patterns. High levels of Hg were found near some of the mining sites, and the dispersion patterns suggest that although dissolved Hg is fairly rapidly lost from solution, a ‘reservoir’ of Hg may build up in the stream sediments causing a potential long-term pollution problem. However, much of the severe contamination is localised and the main Agusan river is relatively little affected. The growth of more highly-organised mining using cyanidation rather than amalgamation and the relative decline of the larger ad-hoc mining operations may indicate that the overall level of Hg contamination is on the decline, though it is recommended that Hg contents in some streams should be regularly monitored.

Contents

Introduction

Background

BGS involvement

Field Work

Sampling and Analysis

Results P

Conclusions

Acknowledgements and References

Appendix - Sample lists, Figures and Analytical data tables

- 1 -

page 2 2 3

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5

6

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Introduction

Funding for a new BGS-led technology development and research (TDR) programme,

Mitigation of Mining Related Mercury Pollution Hazards, was approved by the UK Overseas

Development Administration (ODA) with effect from April 1 st 1995. The three year study

aims to formulate and test mercury pollution monitoring strategies appropriate for use in

areas of artisanal mining world-wide, with detailed case-studies in the Philippines and

Ecuador. The work described in this report was carried out in collaboration with the

Philippines Mines and Geoscience Bureau (MGB). Similar work has also been carried out

under the project in the Palawan Islands (see Williams et al., 1996).

Background to the Philippines work (from the initial MGB Project proposal)

“The discovery of alluvial gold deposits in Eastern Mindanao in the early 80s triggered the

influx of people from all walks of life to the river beds and mountain slopes of the gold areas.

The sudden entry of thousands of people in the gold areas resulted in disorganised and illegal

operations using primitive and unsafe mining and processing methods. These gave rise to

significant accident rates, brutal working conditions and an unhealthy environment.

One alarming environmental problem brought about by these uncontrolled activities in the

gold rush areas is the reported mercury poisoning which had already afflicted a number of

the workers in the areas. Mercury (Hg), is found on the earth’s crust in the form of sulfide

ores such cinnabar (HgS) and occasionally as the native metal. It is also encountered in the

atmosphere from the natural degassing of the earth’s crust such as release of volcanic gases

and evaporation from the oceans. Many activities of man also account for substantial releases

of mercury into the environment. One of these is the mining and smelting of mercury. It is

estimated that losses into the atmosphere during smelting operations are about 2 to 3

percent. The dumping of mine tailings or process wastes into lakes and rivers has resulted in

the high levels of mercury in these bodies of water.

Elemental mercury is liquid at room temperature. When left unsealed or in the open, it

escapes in the air as vapour either alone or attached to other substances. Because it has a

high vapour pressure, it can stay and concentrate in the atmosphere until rains bring it back

down to the earth into bodies of water. This ability to remain in the air either as aerosol or

as vapour is considered as the major health risk to man. The high concentration of mercury

in the environment and food chain can gain access into the human system through inhalation

and absorption from gastro-intestinal tract and skin. Once trapped inside the human cell,

mercury brings havoc to the affected organs of the system.

- 2 -

In the gold rush areas, gold processing necessitates the use of mercury hand in hand with

ballmills and blow torch units in the recovery of gold (amalgamation). This process has

alarmed environmentalists and concerned groups due to the improper use of mercury in gold

smelting and the uncontrolled disposal of mercury wastes into the environment. At the height

of the gold rush in 1986 to 1988 alone, it had been estimated that about 140 tons of

mercury were dumped into the environment, not to mention another estimate of 26 tons

being disposed annually into bodies of water that ultimately drain towards Agusan River to

Butuan Bay in the north and to the Davao Gulf in the southern part of Mindanao.

In May 1987, the first mercury poisoning incident was reported in Tagum, Davao del Norte.

Eleven (1 1) persons were reported ill and one died in this incident where relatively large

quantities of amalgam yielded almost 2 kilos of gold after 8 hours of torching. The number of

fatalities had increased and more people were treated in hospitals allegedly due to over

exposure to mercury. Fishes taken along Ngan River also showed high mercury level

reaching 2.598 pg/g which started the so-called fish scare during that period.

It is on this light of environmental hazard in the gold mining and processing areas in eastern

Mindanao that an environmental geochemical study of the area has been proposed to establish

baseline data on the extent of mercury contamination, not only in the immediate gold rush

areas, but also in the affected environs around its major drainage system. This information

would lay the foundation for a comprehensive environmental and health control programme

which can be integrated to the refinement of legislation concerning the activities/licensing of

large and small scale mining operations.

Earlier studies on mercury contamination in eastern Maintain were conducted by the Small

Scale Mining Unit of Mines and Geosciences Bureau in 1989 due to persistent reports of

mercury poisoning in the gold rush areas. Region XI, where the concentration of the gold

rush is located was first to be monitored. During that period, 53 gold and panning areas in

24 municipalities used mercury to process and recover gold. Samples of water and sediments

from the streams draining the areas were collected and analysed to determine the mercury

disposal pattern, and areas were selected and subjected for detailed survey. Their results

showed that about 28.6% of the total mercury disposed came from mining companies and

71.4% came from small scale processors. The greatest contributors which account for more

than 90% of the total mercury disposed in the region came from the gold rush areas in

Diwalwal, Compostela, Boringot, Tagum and Masara, all in Davao Province. The studies,

however, were short-lived and were terminated in the early part of 1990 due to insufficient

funding from the government. From then on, mercury pollution monitoring has stopped.

Although the number of small scale miners has significantly decreased compared to that at

the height of the gold rush, small-scale operations still continue and dumping of mercury

still poses danger to the environment”.

- 3 -

BGS involvement

A preliminary visit to the Philippines was undertaken in July 1995 to assess the logistic

requirements for a systematic geochemical and hydrochemical study of the Agusan Basin,

Eastern Mindanao (Williams et al., 1995). The region has been subject to a substantial

gold-rush during the past decade, with initially small-scale mining operations accompanied

by the widespread use of mercury as an amalgamation agent for gold recovery from high-

grade ores. More recently, mining co-operatives have formed and the technology has

developed with the use of CIP systems (Carbon-in-pulp: lime-cyanide leaching) to treat the

lower-grade ores now being worked.

The CIP gold extraction process used at Diwalwal, for example, is of a fairly standard modern

type. The crushed ore is milled in ball mills and fed into a sequence of four or five pillar vats

where it is mixed with a sodium cyanide-slaked lime (calcium hydroxide) mixture held at a

pH value about 10-1 1. The gold-cyanide complex formed is then passed to a ‘carbon pulp’

cell. This acts rather like an activated charcoal system, adsorbing the gold complex from

solution. The ‘charged’ carbon is not stripped on site, but sent to the factory site in Tagum

for further processing. Here, the gold is stripped from the carbon with hot alkali and passed

to an electrolysis plant, where the gold is separated from silver and other impurities and

plated onto steel cathodes. The cathodes are then smelted to recover high-purity gold. The

extraction-plant’s efficiency was claimed to give better than 95% recovery. Mercury, often

present in older discarded tailings which are now being bought in and reprocessed by the CIP

operators, is recovered at various stages in the processing and sold back to the miners for

re-use. The recovery efficiency for mercury is not known.

Although the use of cyanide leaching does carry some environmental risk, and its use tends to

raise somewhat emotive opposition because cyanides are such well-known poisons, in fact its

use is more environmentally benign than that of mercury. This is because although cyanides

are highly toxic, they have a very limited survival time in natural waters where they are

very quickly oxidised to harmless compounds such as bicarbonates, nitrates and nitrogen gas.

Thus a cyanide spill may have an immediate and dramatic toxic effect on river life, but the

toxin will be completely removed by natural processes within a matter of a few days.

Mercury, however, is a very persistent poison. In the metallic form it may persist in

sediments for a number& of years, while small amounts will be methylated by bacterial

activity and may enter the food chain in this organic form, or even as inorganic Hg*+ salts.

Mercury also accumulates in the food chain and so can be concentrated in higher organisms,

especially in fish which may be an important human food source.

- 4 -

This report is based on data from a joint BGS-MGB field visit carried out in November 1995

in the southern part of the Agusan basin, and on a survey of the northern part of the Agusan

basin which was sampled independently by MGB staff in February 1996. The field work

involved the systematic sampling of the Agusan catchment for water and stream sediments,

which includes the gold-rush areas of Diwalwal, Bango, Pasian and Mainit in the Upper

Agusan, and the lower reaches of the river down to the sea at Butuan. The November field

work was carried out by the principal author(BGS), two MGB geologists, an MGB mining

engineer with a good knowledge of the mine areas, and MGB driver. Local guides were

occasionally employed on a daily basis where local knowledge was required.

Field work

The field sampling programme was carried out by a joint BGS-MGB field party operating

from a prospecting company’s currently disused base at Montevista. Access to the mining

areas, which may have been problematic, was relatively trouble-free thanks mainly to the

contacts previously made and consequent good relations between the mining operators and the

MGB mining engineer in the field party. Physical access to some of the proposed sites on the

original plan proved impossible, mainly in the steep sections of the rivers below Diwalwal.

We were also advised not to enter the area of the Ngan river immediately below Bango, or the

upper parts of the Pasian system, due to the risk of problems with ‘bandits’. Fortunately we

were able to modify the sampling plan to compensate for these difficulties, and our use of

local guides in some areas enabled us also to compensate for the outdated series of maps

available. Many of these maps date from the 1940’s and are now hopelessly inaccurate with

regards to roads and settlements. (The gold rush of the last ten years has funded the growth of

roads and several major towns such as Monkayo, Compostela and New Bataan on the Agusan

floodplain, in addition to the short-lived mining towns such as Diwalwal).

Diwalwal itself is now almost certainly on the decline as a mining centre as the grade of

workable gold ores falls near to the cut-off level for ‘individual’ mining. The town, having

peaked at a population of probably 100,000+, has now fallen to nearer 40,000. Sanitation

remains non-existent and the local river systems are highly contaminated with domestic

refuse, in addition to the products of mining. The same comments apply to the other mining

centres at Pasian, Bango and Inupuan, though on a smaller scale. The most obvious indicator

of mining activity is the grey, highly turbid nature of the rivers draining the mining areas,

in contrast to the clear waters of undisturbed streams. Logging and other physical

disturbance also causes turbidity, though this is usually buff-brown in colour due to eroded

soil. As the sediment load of the disturbed rivers was so high, this did cause severe problems

with filtration at some sites. Coarse prefilters were used, ahead of the normal 0.45 pm

cellulose disks, on all obviously turbid samples and the filters retained for analysis in these

cases.

A feature of the region, most notably in the Manat river system in the Mainit area, is the

number of hot saline springs characteristic of late-stage volcanic activity. The effect of

these on the natural geochemical background and the behaviour of any pollutants may be of

particular interest.

Sampling and analysis

The sampling techniques used are based on the standard BGS Geochemical Survey Programme

routines, collecting a sub-150 pm stream sediment by wet sieving, a panned heavy-mineral

concentrate, and a suite of water samples filtered through Millipore 0.45 pm filters held in

Swinex carriers into Sterilin storage tubes. These were to be analysed for a range of cationic

and anionic elements plus total and organic mercury. The water samples for cation anaysis

were stabilised by the addition of 0.3 ml concentrated HNO3 (Aristar grade), those for total

Hg stabilised by adding 0.6 ml acidified potassium dichromate solution, and those for anion

analysis reatined unacidified. The sediments were retained moist in plastic securitainers,

rather than allowed to dry in paper bags, to retain volatile mercury. Filters were also

retained to give an indication of suspended contaminant load at sites where this was

significant. At each site a set of water parameter measurements were made (pH, Eh,

conductivity and temperature) using Orion and Hanna Instruments meters, and the location

logged where possible by the use of a hand-held GPS unit (Silva GPS Compass).

Analysis was carried out at BGS using a variety of instrumental techniques. The acidified

filtered water samples were analysed for 12 cations plus total sulphur as sulphate by

Inductively Coupled Plasma Atomic Emission Spectrometry, the unacidified waters by Ion

Chromatography for Nog- and CI- and Total lnorganic/Total Organic carbon by means of a

TIC/TOC analyser. Free cyanide (CN’) was searched for, but not found at detectable levels, in

the most contaminated samples. The stream sediments and panned concentrates, specially

‘cool ground’ prepared to avoid Hg vapour loss, were analysed by X-Ray Fluorescence

Spectrometry for a selection of major and trace metals. Total mercury in waters, preserved

from elemental Hg vapour loss by the field addition of acid potassium dichromate, was

determined by Cold-vapour Atomic Fluorescence Spectrometry following a conventional

stannous chloride reduction stage (CVAFS), and in stream sediments by CVAFS following an

aqua regia digestion. Organic mercury was determined by difference, using a brominating

agent to oxidise any organomercury compound to Hg2+ and re-analysing by CVAFS. The

‘suspended load’ Hg held on the filter papers was estimated by digesting the papers in aqua

regia and determining the Hg in solution by CVAFS.

- 6 -

Results.

Data for Hg in stream waters, filter residues, stream sediments and panned concentrates,

plus a range of cations and anions, inorganic and organic carbon in the stream waters are

shown in the various tables (1-10) in the Appendix at the back of this report. For ease of

interpretation much of this data is treated graphically both in terms of the full data set and

as local studies in downstream sequence order. Maps showing the sample locations are given

in Figs.1 and 2, and a description of the sample sites in the Upper Agusan is given in Tables

(1 and 2).

The data show high levels of mercury in solution (Fig. 3) in the headwaters of the Mamunga

River near to the Diwalwal mining camp area, with a maximum of 1539 ppb Hg in stream

water noted from one site. Much lower values were found in waters at the other mining areas

of Bango and Mainit. Samples from the Mamunga River below the Diwalwal mines (Fig. 4)

show levels of inorganic and ‘total’ dissolved Hg to be very similar for most sites, within the

usual margins of error, suggesting that most of the Hg in solution is in inorganic forms.

Significantly, the mercury levels in the stream waters fall rapidly downstream from the

Diwalwal site, following a near-logarithmic decline curve, due probably to a combination of

the effects of dilution, sorption by sediment and volatilisation. As a result, by the time the

Mamunga River leaves the mountain front, its dissolved Hg load has fallen to 7 ppb, and

another few km downstream near its confluence with the Agusan has declined further to 0.1

ppb. Although this value is still marginally above the local background it has little

toxicological significance. In the streams and rivers sampled in the Lower Agusan basin, only

three values above the 0.02 ppb analytical detection limit were found, with a maximum

value of 0.09 ppb (Fig. 5).

High Hg levels (up to 40 ppm relative to filter weight) were found in the suspended matter

trapped on coarse filters at Diwalwal, with 5 ppm on the 0.45 pm fine filters at the same

sites (Figs. 6 and 7). Much smaller amounts of Hg were found at the other mining centres of

Bango and Mainit, despite similar levels of suspended sediment in the streams. The

significance of the high values at Diwalwal is that the bulk of the Hg load is being held on

material which can be trapped on a coarse prefilter, so is present as either fine particulate

metallic Hg. or is bound by sorption to silt and clay particles. Taking and analysing samples

of 0.45 pm-filtered water alone would therefore underestimate the amount of Hg being

transported in the river by a large factor.

Mercury levels in the stream sediments and panned concentrates from the Upper Agusan can

be seen in Fig. 8. As with the stream waters, high Hg levels were detected at Diwalwal,

Bango and Mainit; with the highest values (>60 ppm in panned concentrates) at Diwalwal. At

some sites, values in pans are higher than in sediments while at others the reverse is true.

- 7 -

This may indicate a variable proportion of free metallic Hg, which is likely to concentrate in

the pans, relative to the Hg bound to the finer silt and clay particles.

Several points can be made from this data: Firstly that site 4, which is a relatively clean,

non-turbid stream despite its proximity to Diwalwal, showing little Hg in solution and

nothing in the suspended fractions, has a high Hg value in the sediments (but low in the

panned concentrates) suggesting that this is a ‘historic’ but recent contamination signature

in a stream which is no longer affected by current mining activity. Second, the rate of

downstream decline in Hg content is less marked than for the stream waters, with relatively

high values (-20 ppm) in the sediments at sites PMC 12 and 13 on the plain several

kilometres from the Diwalwal source. However, there is a dramatic fall in sediment values

between sites PMC 12 and PMC11 (less than l k m apart) suggesting that either a high

proportion of the suspended sediment drops out within this area on the alluvial plain, or

perhaps that the pollution front has not yet reached the lower site. As the sources for the Hg

in the sediments include direct sorbtion from solution and the physical sedimentation of

suspended sediment containing sorbed Hg, the difference between the water and sediment

patterns is consistent with the expected Hg behaviour. However, the relatively high levels of

Hg in the stream sediments in this area may be a long-term source of contamination,

perhaps for a number of years. In the Mainit area, a relatively high Hg level in panned

concentrates at site PMC 35 also generates a ‘tail’ downstream (sites 40-43) possibly with

historic inputs from the other workings in the Mainit area. In the Lower Agusan, only two

sites (1 16 and 117) at 0.75 and 1.5 ppm stand out above a background with values

generally ~ 0 . 2 5 ppm (Fig. 9).

Levels of the heavy metals Cu, Zn and MO in stream waters are shown in Fig. 10. Diwalwal

again stands out as the most contaminated site, with 350 ppb Cu in solution at site PMW2

along with 80 ppb Zn and surprisingly high MO levels, with maximum of 40 ppb at site

PMW 3. Copper levels remain high downstream and are still detectable at the mountain front

(site PMW13) although MO has dropped below the detection limit by this time. Zinc values

are at relatively steady ‘background’ levels throughout much of the the catchment.

The levels of the major elements Si, Mg and Ca in the Upper Agusan stream waters are shown

in Fig. 11. Consistent with the alkaline pH of the waters, the levels of Si, Ca and Mg are

relatively high and fairly steady, except for the saline spring water input at site PMW 39. Figure 12 shows levels for Na, SO4 and CI, and again the most significant feature is the input

from the hot saline spring at site PMW 39, and its effects on the river downstream. Sulphate

levels are somewhat above the local background at Diwalwal, but this is unlikely to have

much significance with respect to the mobility of Hg or the other trace metals. Levels of

nitrate (Nog) and of total inorganic carbon (TIC) and total organic carbon (TOC) are shown

in Fig. 13. The highest nitrate levels are present at Diwalwal, with up to 10 mg/l in solution

- 8 -

derived from the township, as is the near 40 mg/l of organic carbon here. Site PMW 17

(Bango) also shows high TOC probably for the same reason. For the most part, the TIC values

are fairly steady, with only the saline spring at site PMW 39 showing an anomalously high

value. Nitrate levels are above background at sites PMW 40 and 42, though for less obvious

reasons. In the Lower Agusan basin, levels of CI, NO3 and SO4 show very little variation

(Fig.14). Iron and manganese levels in solution (Fig. 15) show some differences, with a

high Fe value at site PMW 5 below Diwalwal, and high Mn values in the Manat river system

at Mainit derived from the saline spring at site PMW 39. The source for the high Fe level at

Diwalwal is unclear, but the precipitation of iron oxides downstream may help to co-

precipitate some Hg and other heavy metals and thereby reduce their toxicity in solution.

Conclusions

The high levels of Hg in the upper reaches of the Mamunga River below Diwalwal must be of

some concern, though whether the greater health risk to the human population comes from

the mercury or from the generally poor sanitary conditions is debatable. The level of

pollution in the river from ordinary domestic waste and the high suspended mud load would

by themselves have a deleterious effect on the life of the river. Although the levels of Hg in

solution in the river fall quickly downstream, the persistence of relatively high Hg levels in

the stream sediments could be a long-term problem and really requires longer-term

monitoring, especially to note the rate of natural Hg removal when/if the use of liquid

mercury at Diwalwal ceases. Similar arguments apply to the other mining sites, notably

Bango and Mainit, though the apparent problems here are less acute. Direct evidence for

environmental and health risks from the presence of Hg from the mining operations was not

sought in this project, but it would be wise to regard the Mamunga river water as a potential

health risk and advise against its use for domestic purposes, and with some suspicion for

agricultural purposes. It is also recommended that the water be tested for its faecal bacteria

load, as this may be potentially a greater health risk than the mercury content. With the

decline in the use of Hg by the artisanal miners, and its more cautious handling where it is

still used, it is expected that the Hg content of the river waters in the Agusan basin will

steadily decline over a period of time through natural processes, though the reserves of Hg in

the stream sediment will make this a slow process. The authorities should continue their

current policy of monitoring environmental mercury levels in both the mining areas and the

processing areas such as Tagum, and continue to discourage the use of mercury and encourage

the use of other, less damaging, gold extraction methods where possible.

- 9 -

Acknowledgements.

Thanks are due to all the MGB staff who participated in the work programme, especially

Juliet Miguel, Resty Gomez and Dr. Fernandez; to the mine and processing-plant owners and

operators for permission to examine the mining operations and carry out the sampling, and

the local people who acted as guides to some of the more obscure areas.

References

Wiliams, T.M., Apostol, A. and Miguel, J. 1995: Mercury contamination in artisanal gold

mining areas of eastern Mindanao, Philippines: A preliminary assessment. BGS Overseas

Geology Series Technical Report WC/95/72/R

Wiliams, T.M., Weeks, J. M., Apostol, A and Miranda, C. 1996: Assessment of mercury

toxicity hazard associated with former cinnabar mining and tailings disposal in Honda Bay,

Palawan, Philippines. BGS Overseas Geology Series Technical Report WC/96/31/R

- 1 0 -

Appendix

Table 1. Upper Agusan Sample Site List and description

Samole NQ, PM1 PM2 PM3 PM4 PM5 PM6 PM7 PM8 PM9 PMlO PM1 1 PM12 PM1 3 PM14 PM15 PM1 6 PM17 PM1 8 PM1 9 PM20 PM2 1 PM22 PM23 PM24 PM25 PM26 PM27 PM28 PM29 PM30 PM31 PM32 PM33 PM34 PM35 PM36 PM37 PM38 PM39

PM40 PM4 1

PM42 PM43 PM44 PM45 PM46 PM47

Diwalwal. Martin’s site DW4, now with extended mining. Turbid 8 smelly! North of previous site. Currently being mined. Very turbid, grey 8 smelly! Main stream draining Diwalwal, upstrm. of fork. very turbid, much debris. Tributary from northwest, above fork. Much cleaner, little suspended load. About 300m downstream of confluence. Very turbid, grey-buff. West-flowing trib. to Mamunga river. Clean, little suspended load. Main river just above confluence with trib. at PM6. Very turbid, buff-grey S-flowing trib. to Mamaunga river. Clean and fresh. West-flowing river at Hulip, fairly clean. As above, some 1.3km downstream. Fairly clean. Mamunga river, well down on floodplain. Turbid, but less so than higher up. Mamunga river, about 3km upstream of PM1 1. Stony bed, very turbid. Mamunga river, ca. 1 km upstream of PM12. Irrigation weir, very turbid. Ngan river, Bango. At mining area, very turbid, buff-orange. Tributary to Ngan, some mining upstream. Muddy tributary to main river. Hydraulic mining upstream, hence turbid. Main river above ford and confluence with tributary at PM16. Tributary near road bridge, muddy and brown. Main Ngan river near mountain front: wide, brown and turbid. Ngan river, further downstream by old sawmill. Wide, brown and turbid. Tributary to Agusan (Batutu river), just outside Compostela. Very turbid. Lowest point on Ngan, near confluence with Agusan. Very turbid. Pasian river, right-hand (S) fork, within coconut plantation. Clear. Pasian river, left-hand (N) fork. Slightly turbid. Pasian river 200m below road bridge. Wide stony bed, turbid but has fish. Haguimitan river u/s of road bridge. Pt. of comm. irrigation system. Clean. Manat river, just above confluence with Agusan. Wide, deep and muddy. Manat river, upstream of site PM27, by ferry. Streams north of Compostela: southern member. Fairly clean. As above: central member. Clean. As above: northern member. Clean, but algae & brown deposits. South of Compostela. Stream S. of New Bataan, north-flowing. Clean. N-flowing stream north of New Bataan. Clean 8 rich in tadpoles & fish. Stream above Mainit: western fork, smaller of two. Muddy, sandy 8 turbid. Eastern fork of above. Also muddy, turbid and WARM. Hot springs upstream! Main river, upstream of hot springs at Saravan. Grey 8 turbid, mining u/s. Tributary of above, flowing NW, just above confluence. Clean 8 fresh. The HOT SPRINGS at Saravan. Algae matts in hot, saline water. Adjacent steep normal stream is being panned, disturbance giving brown, turbid water lower down. River at Payawan. Wide, brown and muddy. River at Mainit, east of village. Long concrete road bridge 8 alluvial flats. Water brown and turbid. East river at Mainit, by second ‘fallen’ bridge. Smaller than W branch. Manat river at Santa Cruz. Wide, brown and turbid. River at New Daius bridge. Muddy. Manat river at bridge between New Daius and Santa Cruz. Sluggish lowland river at Magsasay in area of rice padis & banana plantns. Manat river at Montevista. Strong flow, wide & muddy.

- 1 1 -

Table 2: Upper Agusan: Sample Site List, Location and Water Parameters

SamDle No, PM1 PM2 PM3 PM4 PM5 PM6 PM7 PM8 PM9 PM1 0

PM1 1 PM12 PM1 3 PM1 4 PM15 PM1 6 PM17 PM18 PM1 9 PM20

PM21 PM22 PM23 PM24 PM25 PM26 PM27 PM28 PM29 PM30

PM31 PM32 PM33 PM34 PM35 PM36 PM37 PM38 PM39 PM40

PM4 1 PM42 PM43 PM44 PM45 PM46 PM47

a 126O 126O 126O 126O 126O 126O 09.87 126O 126O 08.97 126O 07.35 126O 03.23

126O 04.12 126O 05.78 126O 06.57 126O 126O 126O 126O 126O 10.54 126O 08.33 126O 07.67

126O 126O 06.37 126O 05.37 126O 05.06 126O 04.42 126O 04.71 126O 02.01 125O 59.89 126O 06.22 126O 06.34

126O 06.09 126O 06.77 126O 09.23 126O 07.80 126O 01 3 2 126O 126O 02.60 126O 02.65 126O 126O 01.33

126O 01.48 126O 01.64 126O 01.37 126O 02.27 126O 01.22 125O 59.51 126O 00.16

Northln_a 70 70 70 70 70 7O 46.43 70 70 46.19 70 49.45 70 48.51

7O 46.69 7O 45.40 7O 45.61 70 70 70 70 70 40.32 70 42.18 70 41.94

70 70 41.30 70 54.95 70 55.56 70 55.74 70 53.52 7O 48.92 70 44.43 7O 42.73 70 43.75

7O 44.20 7O 40.33 70 32.49 70 36.42 70 29.36 70 7O 27.87 7O 27.94 70 7O 30.55

7O 32.79 70 30.75 70 34.43 70 36.16 7O 36.39 7O 38.66 7O 42.46

RH 6.8 8.8 8.1 8.1 8.2 8.2 8.2 8.0 8.2 8.0

7.7 8.5 8.2 7.9 8.0 8.2 8.0 8.0 8.2 8.2

7.8 8.0 8.1 7.9 8.1 7.8 7.6 8.0 7.8 8.0

8.5 8.0 8.5 7.5 8.5 8.1 8.3 8.2 7.1 8.2

7.6 8.2 8.0 7.6 7.9 7.5 7.8

94 -1 30

-20 85 48

160 80

1 60 130 1 35

120 1 02

30 146 150 1 60 150 150 190 180

170 160 1 80 145 147 1 77 1 95 1 80 185 21 5

200 220 195 240 1 60 140 202 200 210 180

180 232 220 230 230 230 230

320 240 260 162 240 220 230 150 21 0 220

256 220 218 138 173 35

120 105 130 170

345 181 21 5 228 272 210 470 470 230 275

215 215 190 400 370

2470 240 285

81 00 2020

1750 250

1175 228

1100 525 400

TemDerature 23.5 24.0 26.0 26.1 24.8 24.0 24.1 24.7 24.7 31.2

32.2 27.5 24.7 24.6 25.0 23.4 23.5 25.0 25.2 26.0

25.0 24.5 24.8 26.4 29.4 29.4 29.6 27.9 26.7 26.7

26.5 26.5 23.2 26.6 24.2 34.4 24.6 24.5 78.8 31.4

31 -2 24.7 28.1 26.2 28.4 27.0 27.2

- 12-

Table 3. ICP Detection Limits

Lab. No 8932 - Water analysis - Philippines

Samples were run on a Fisons/ARL 3580 Inductively Coupled Plasma - Atomic Emission Spectrometer. Samples were run as recei\.ed

lypical Detection Limits Analyte LoD Sr 0.001 ppm

Ba 0.002 ppm Si 0.010 ppm Mn 0.001 ppm Fe 0.004 ppm P 0.061 ppm S 0.041 ppm B 0.01 1 ppm Mg 0.018 ppm

Na 0.012 ppm

Cd 4 PPb

V 6 PPb

MO 9 PPb AI 14 PPb Be 0.3 ppb Ca 0.013 ppm Zn 5 PPb cu 2 PPb

Li 1 PPb Zr 3 PPb

Ni 9 PPb Y 1 PPb La 7 PPb

Cr 16 PPb

Pb 25 ppb

C O 12 ppb

K 0.03s pprn

Note data belou. detection limit are reported as -DL e.g.. for Cd. -4

Analysts: L Ault & P H Starbuck 2211 2/95

UJ

m m "10, r d w

2 n o o o o o o o o o o 0-0-0-0 o 00 tn o o o o o o Q ~ - - - - - - - - - - - - ~ I n c v - T - T - - Q 7 v v v v v v v v v v v V V - ~ V V V V V V

- - . - ~ n ~ o o o o o o o o o o o o o o o o o t n o o o o ~

v v v v v v v v v v v v v v v v v v v v v v ~ ~ o o o m o m o m o m m o o o o m o d o o o 0 o

Y

0 0 - 0 0 0 ~ 0 0 0 0 0 0 0 0 0 0 - 0 0 0 0 0

- 0 0 0 0 0 0 0 0 0 0 0 ' 0 0 0 0 0 0 0 0 0 0 0 0

Table 6

.S. 7953-i

I

7975 'PMW023 1 4 t -

Upper Agusan Anions and TlC/TOC data

' 7982 !PMW030 0.88 I <0.101 9.80! 31.2 7983 ,PMW031 0.94 I <0.101 9.65 I 28.7 7984 lPMW032 I 5.63 I <0.101 6.771 38.2 7985 jPMW033 I 0.63 I <0.101 7.041 21.1 7986 lPMW034 I 1.11 I co.20 I 4.73 1 45.7 7987 IPMW035 I 1.64; <0.101 9.501 39.7

7989 lPMW037 I 104' eo 101 3 171 18 8 7990 lPMW038 , 0.96 ~ <O.lOI 4.94 ~ 22.1

7988 1 PMW036 384 <2.00 I 9.09 I 38.8

I

7991 ;PMW039 ~ 16901 4 0.0 1 9.35 I 70.1 7992 'PMW040 282 5.391 7.06! 28.7 7993 PMWO41 284 I <1.001 5.53 c 37.0

7995 ,PMW043 1601 ~0.50 i 6.58 1 33.6

I

, 7994 PMW042 18.2, 0.44 I 4.65 I 22.2

BGSCode j Samplecode I Cl I NO3 i TOC I TIC I__

I--.--- I -_t_----- --- -1 I

~-~ ~

1.321 <0.101 8.36' 25.1 I '976- -1PMW024 I 1.53' <0.101 8.45 23.81 I

7977 jPMW025 I 1.581 <0.10) 4.75 i 31 .O 7978 IPMW026 ~ 1.66! <O.lOi 5.64 1 24.8 7979 ! PMW027 j 37.5 1 <0.20; 8.46 I 31.8

41.5; co.20 I 10.4 1 29.7 7980 iPMW028 7981 :PMW029 1 1.16i <O.IOj 8.84 23.8

N. Breward Philipine Waters. Page 1

Table 7. Upper Agusan Hg in waters data

AGG LAB. NO. 8932 Neil Breward - Philippine water samples

MERCURY DATA

SAMPLE

PW1 PW2 PW3 PW4 PW5 PW6 PW7 PW8 PW9 PWlO PWll PW12 PW13 PW14 PW15 PW16 PW17 PW18 PW19 PW20 PW21 PW22 PW23 PW24

Hg PPb

0.87 315 1539 10 60 0.03 103 4 0.09 0.18 0.10 0.17 7 0.11 0.07 0.07 0.04 0.07 0.09 0.06 0.04 0.06 0.05 0.03

SAMPLE

PW25 PW26 PW27 PW28 PW29 PW30 PW31 PW32 PW33 PW34 PW35 PW36 PW37 PW38 PW39 P W40 PW41 PW42 PW43 PW44 PW45 P W46 PW47

Hg PPb

0.04 0.03 0.03 0.03 0.02 0.02

<0.02 <0.02 <0.02 <0.02 0.03 0.02

<0.02 0.02

<0.02 0.04

<0.02 <0.02 0.02 0.04

<0.02 c0.02 0.02

Note: Results are on samples preserved in acidic dichromate solution. This will not break down any organornercury compounds present.

B P VICKERSK D HUGHES 20.12.95.

Table 8.

AGG LAB NO. 8939

Upper Agusan Hg in filters

FILTER PAPERS

P

Page 1

Table 9. Lower Agusan Hg in waters data

SAMPLE PMW 101

AGG LAB NO. 5086 INORGANIC MERCURY ANALYSIS

PPb Hg <0.02

PMW 102 PMW 103

<0.02 <0.02

IPMW 104 1<0.02

PMW 106 PMW 107 PMW 108 PMW 109

t

<0.02 <0.02 <0.02 <0.02

IPMW 105 (0.07/0.07

PMW 110 PMW 111

I

<0.02 <0.02

PMW 113 PMW 114 PMW 115 PMW 116 PMW 117 PMW 118 PMW 119 PMW 120 PMW 121

<0.02 <0.02 <0.02 0.09/0.1 o * 0.04/0.04* <0.02 <0.02 <0.02 <0.02

IPMW 112 )<0.02 1

PMW 123 C0.02 IPMW 122 1<0.02 1

1' = duplicate analysis 1

PHILIPPINE WATERS

B P VICKERS 1.5.96. Page 1

Table 10. Lower Agusan Anions data

PMWl22

Version 3

2.87 1 <O.lO 1 12.1 PMWl23

co.10

PMWlO3 3.94 eo. 10 PMWlO4 1.84 I ~0.10,

6.56 I <0.10) 9.37

PMWl18 1 2.171 9.08 PMWll9 3.11 i 0.121 15.3

N. Breward Philippine Waters. Page 1

25/06/96