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Earthworms as a Bioindicator of Mercury Pollution in an Artisanal Gold Mining Community: Cachoeira do Piriá, Brazil Jennifer J. Hinton B.A.Sc. Geological.

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Presentation on theme: "Earthworms as a Bioindicator of Mercury Pollution in an Artisanal Gold Mining Community: Cachoeira do Piriá, Brazil Jennifer J. Hinton B.A.Sc. Geological."— Presentation transcript:

1 Earthworms as a Bioindicator of Mercury Pollution in an Artisanal Gold Mining Community: Cachoeira do Piriá, Brazil Jennifer J. Hinton B.A.Sc. Geological Engineering The University of British Columbia Dept. of Mining Engineering Marcello Veiga Professor of Mining Engineering

2 Outline of Discussion Mercury and Artisanal Gold Mining Mercury in the Environment Mercury in Cachoeira do Piriá The Earthworm Protocol Results Implications

3  Worldwide: 13 million artisanal miners in 55 countries. Continent Number of Miners (million) Asia/Pacific Africa Latin America Developed countries Total Source: International Labour Organization (1999) Gold is the main substance extracted: ~ 6 million people extracting tonnes Au/year.  80 to 100 million people worldwide depend on this activity for their livelihood. Mercury and Artisanal Gold Mining Mercury (Hg) Emissions: Discharged as tailings, vapour, pure Hg o 3000 – 4000 tonnes of Hg emitted in the Brazilian Amazon

4 Exposure Pathways 1. Inhalation

5 Fish may be contaminated several years after mining activities have ceased Exposure Pathways 2. Ingestion

6 Mercury Transformations Hg(II) Hg o CH 3 Hg + (CH 3 ) 2 Hg CH 3 SHgCH 3 [HgS, HgS 2- HgS 2 H -...] Hg-humates, Hg-tannates, Hg-fulvates [HgCl 2, HgOHCl Hg(OH) 2...] CH 3 HgCl CH 3 HgOH ?

7 After Veiga et al. (1999 ) Bioaccumulation and Biomagnification Mercury Transformations 70 to 90% of Hg is methylated Bacteria Metallic Hg Organic Acids Bacteria Soluble complexes Colloids CH 3 Hg + ? Thesis

8 Cachoeira do Piriá, Brazil BRAZIL BELÉM Capanema Cachoeira Atlantic Ocean Pará State BR-316

9 Gold Rush: 1980 – attracted 10,000 people (5000 miners) - extracted around 4 tonnes of gold “An island of prosperity in a sea of poverty” (Veiga, 1999) Cachoeira do Piriá, Brazil

10  More than 4 tonnes of Hg emitted to the environment  Elevated Hg levels in biota (fish, pigs, cattle, humans) Cachoeira do Piriá, Brazil

11 Wetland Zones Cachoeira do Piriá Approx. 1 km Two Main Mining Areas Rio Macaco N Bela Vista Downstream ~2.5 km Important Fishing Areas Soil/Sediment/Tailings Samples (collected ) Cachoeira do Piriá, Brazil

12 Cachoeira – Mercury Distribution Mercury Concentration (ppb) Approx. 1 km Currutela Creek Barriquinha Creek Lake Cachoeira Cachoeira Tailings Soil/Sediment/Tailings Samples (collected )

13 Cachoeira – Mercury Distribution (cont…) Tailings – Revegetation in progress

14 Effluent from active mining area entering Barriquinha Creek Cachoeira – Mercury Distribution (cont…)

15 Cachoeira – Mercury Distribution Mercury Concentration (ppb) Approx. 1 km Currutela Creek Barriquinha Creek Lake Cachoeira Cachoeira

16 Cachoeira – Mercury in Fish Traíra 925 ppb 68% Jejú 1274 ppb 100% Mãe Rosa 667 ppb 63% Mandi* 108 ppb 0% Acará 347 ppb 21% Piaba 215 ppb 0% FISH Hg (ppb) % > 500 ppb Herbivorous Carnivorous * Mandi omnivorous Cachoeira Adult Male 2 Adult Female 4 Child (1-4 yrs) 14 Bela Vista Adult Male 6 Adult Female 17 Child (1-4 yrs) 56 ExposureTimes above GroupSafe Limit

17 A Comparative Methodology  How do materials influence bioavailability?  How to identify/prioritize “hot spots”? Simple, Low-Cost Methodology Using Earthworms: Accumulate Heavy Metals from soil and other media Ingest large quantities of soil and are in full contact with the substrate they consume Participate in many food chains Constitute up to 92% of Invertebrate Biomass in soils Eisenia foetida species recognized for toxicity testing by several international organizations (Including: European Economic Community, U.S. EPA, ASTM, etc.)  Can bioavailability be reduced?

18 Invertebrate Protocols ASTM Standard Guide for conducting laboratory soil toxicity tests for the Earthworm Eisenia foetida US EPA 600R94024 Methods for measuring the Toxicity and Bioaccumulation of Sediment-Associated Contaminants with Freshwater Invertebrates ASTM A Standard Guide for Conducting Sediment Toxicity Tests with Freshwater Invertebrates Lockheed Martin Environmental Restoration Program: Development and Validation of Bioaccumulation Models for Earthworms Goats and Edwards (1988) – Prediction of Field Toxicity of Chemicals to Earthworms by Laboratory Methods Hazardous Materials Assessment Team (HMAT) – 14-Day Soil Test using Earthworms

19 { } Jars 20 Worms 60g Soil/sand + 80 ml 20 g. cellulose #1 Distilled Water Organic Acids { } Earthworm Methodology 28d Exposure CVAA Digested tissues analyzed #4 Depuration Worms removed, cleaned, weighed and starved for 24 hrs. #2 Acid Digestion Worms cleaned, weighed and tissues dissolved in 0.7M HNO 3 #3

20 Experimental Program Earthworm Protocol SolutionsSoils / Sediments / Tailings 1.Evaluate the efficacy of the methodology. 6 Series of Tests 2.Determine influence of specific variables. 3.Assess the bioavailability of Hg-organic complexes. 1.Evaluate the efficacy of the methodology. 7 Series of Tests 2.Compare the effectiveness of different soils in inhibiting Hg bioavailability. 3.Assess the influence of organic acids on Hg bioavailability. B-1 B-2 B-3 B-4 B-5 B-6 B-7 Moisture content assessment Organic-rich soil and tailings Humic acid (3) and tailings 3 different soils mixed w. tailings Humic and tannic acid  tailing and lateritic soil Soils, seds and tails of Cachoeira Tannic acid  tailing / lateritic soil / tails-lat mix A-1 A-2 A-3 A-4 A-5 A-6 Exposure time / depuration time / experimental design { Verify A-2 / Hg dose vs. uptake Humic acid habitability Hg uptake in humic, tannic acid MeHg in worms exposed to Hg in humic, fulvic and tannic acid 1.Organic acids and Hg Bioaccumulation 2.Hg Bioaccumulation in Cachoeira 3.Reducing Hg Bioaccumulation in Cachoeira

21 Solution Tests – Effect of Organic Acids Metallic Hg Solubility: 0.56 ng g -1 in water After 24 hr stirring (1-6 g of metallic Hg – excess removed):  g L -1 in tannic acid 3780  g L -1 in humic acid Solubility directly linked to bioaccumulation

22 Series A (sd 244) (sd 1041) 828 Series A (sd 875) (sd 1625) 828 Series A (sd 1463)1424 Control worms178 (sd 15) 7 Test DescriptionHg in Tissues* Hg Substrate ppbppb * Average of replicates shown Solution Tests – Effect of Organic Acids

23 Solution Tests - Methylation and Organic Acids Description WormsSubstrate MeHg (ppb) % of Total Hg MeHg (ppb) % of Total Hg HA + Hg x HA + Hg x TA + Hg x TA + Hg x TA + Hg x FA + Hg x FA + Hg x Average x TA = tannic acid; HA = humic acid; FA = fulvic acid

24 Methylation Potential of Earthworms CONTROLSWORMS (with Hg) WORMS (no Hg) WORMS (TA, no Hg) WORMS (HA, no Hg) WORMS (culture bin) SRB Innoculant ++ SRB- SRB + SRB ++ SRB + SRB ++ SRB - No SRBs + SRBs probable ++ SRBs present The potential for intestinal methylation of Hg (or direct bioaccumulation of Hg-organic complexes) warrants further study!!

25 Soils Tests – Effect of Organic Acids Hg Solubility - Shake Flasks: Tailing (10500 ppb)Tannic Acid210  g/L Humic Acid110  g/L Distilled Water 12  g/L Tailing (10500 ppb) Lateritic Soil (150 ppb) SubstrateTannic Acid Humic AcidWater *Average of replicates shown Concentrations shown are Hg in worm tissues in ppb (  g/kg) Hg Bioavailability – Earthworm Experiments*:

26 Soils Tests – Effect of Organic Acids Hg Bioavailability in association with Tannic Acid (TA): Tailing (3180 ppb), Lateritic Soil (135 ppb), and Tail/Lat Mixture (1933 ppb) Tailing + TA > Lateritic Soil + TA > Tailing:Lat Soil + TA Increasing bioaccumulation Tailing (1180 ppb) Humic Acid Distilled Substrate 0.25 g/L g/L 0.05 g/L Water *Average of replicates shown Concentrations shown are Hg in worm tissues in ppb (  g/kg) Hg Bioavailability in association with Humic Acid *: 1.Organic acids and Hg Bioaccumulation 2.Hg Bioaccumulation in Cachoeira 3.Reducing Hg Bioaccumulation in Cachoeira

27 Bioaccumulation in Cachoeira Tailings Lateritic Soil Organic-rich Soil Clayey Sediment Test DescriptionHg in Worm Tissues* Hg in Soil ppbppb *Average of replicates shown Distilled water applied to Jars

28 Wetland Zones Cachoeira do Piriá Rio Macaco N Downstream ~2.5 km Important Fishing Areas Bioaccumulation in Cachoeira Mining Areas Bela Vista Moderate Vegetation Dense Vegetation 150 (120) 270 (1630) 3730 (380) 2925 (710) 1180 (1370) 315 (190) (1373) 90 (120) 205 (330) 20 (430) 440 (250) 70 (37) 70 (37) clay 20 (430) organic soil 270 (1630) lateritic soil 315 (190) tailings Hg (ppb) in Soil Hg (ppb) in Worms

29 Options for Mitigation  Information-Based Measures - Communication of health risks  Wetland Remediation? May exacerbate problem  Permeable or Impermeable walls? Costly; maintenance/monitoring  Phytoremediation/Phytoextraction? Promising but not yet proven  Appropriate Technical Measures - Use of local materials to cap “hot spots” - ‘Clean’ lateritic soils or clayey sediments

30 Reduction of Hg Bioaccumulation Hg in Tissues * (ppb) Tailing Org-rich soil Lateritic SoilClayey Sediment + tails + tails + tails *Average of replicates shown Hg Bioavailability – Earthworm Experiments*: Rel. Influence on Hg uptake ++ Relatively strong, positive influence on Hg Bioaccumulation + Positive influence on Hg Bioaccumulation - Negative influence on Hg Bioaccumulation

31 Hg-organic acid complexation definitely important pathway for Hg bioavailability:  Tailings: % more uptake in association with humic and tannic acids than with distilled water. Conclusions:  Lateritic Soil: % more uptake in association with humic and tannic acids than distilled water.  Solutions: Concentrations in Worm Tissues of ppb following exposure to Hg in tannic acid. Significant in terms of current understanding of biogeochemical cycling of Hg in darkwater systems!  Intestinal Methylation? Methylmercury bioccumulation orders of magnitude higher in worms than substrate. Also presence of SRBs.

32 Hg pollution in Cachoeira presents hazards to area residents:  Tailings-associated Hg: Mobilizing from mining areas into organic-acid rich watercourses. Conclusions:  Fish Consumption: Residents of Cachoeira – 2 to 14 times safe ingestion levels Residents of Bela Vista – 6 to 56 times safe ingestion levels  Soils, Sediments and Tailings: Hg concentrations range from 5 ppb to ppb (ave. 695 ppb) How can Hg pollution in artisanal mining communities be mitigated?

33 Appropriate responses to effectively mitigate impacts from artisanal mining activities are critically needed:  Capping using Local Materials: Clayey sediments highly effective; Lateritic soils also effective (except in the presence of organic acids) Conclusions:  Non-technical Measures also needed: - Educational campaigns - Consumption advisories  Earthworm Methodology: Low cost, simple method to assess hazards and mitigation measures Integrated approaches are the most effective!

34 Recommendations:  Replicate earthworm experiments – statistical confidence in results.  Assess the methylation potential of earthworms.  Explore mechanisms influencing Hg uptake from lateritic soils in conjunction with organic acids.  Conduct Risk Assessment in Cachoeira and Bela Vista.  Develop remediation technologies appropriate to artisanal mining communities.  Develop educational programs and consumption advisories. Artisanal Mining is an essential economic activity… concrete solutions must be developed!

35  Dr. Ken Hall – Civil Engineering Many Thanks:  NSERC Operating Grant #  Dr. Malcolm Scoble – Mining Engineering  Dr. Kevin Telmer – University of Victoria  Dr. Marcello Veiga – Mining Engineering  Colleagues and Faculty in the Mining Department Research Committee:  My Family and Friends


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