Mercury in Drilling Fluids

Presented by

Dr. Richard Prentki

MMS Alaska OCS Region

At the North Aleutian Basin Energy-Fisheries

Workshop held March 18-19, 2008, in

Anchorage, AK

This talk is modified for this NSB

workshop from a presentation

developed by Dr. Mary C. Boatman,

MMS Environmental Sciences

Branch on “Issues Regarding

Mercury in the Gulf of Mexico”

Overview

• Mercury in the Environment

• Mercury in Drilling Fluids

• MMS Studies on Mercury

Mercury in the Environment

• Elemental Mercury - liquid or gas - Hg0

– Silvery liquid in a thermometer

– Gas in the atmosphere

• Inorganic mercury - salt or mineral - Hg2+

– Dissolved in water

– Mineral Cinnabar - HgS

• Organic mercury - methylmercury - CH3Hg+

Mercury to Methylmercury

• Natural process

• Converted to methylmercury by bacteria

• Only a few types (species) of bacteria

• Can occur without bacteria but rarely

• Possibly occurs in some plants

Mercury in an Industrialized

Society

• Pre-industrial - Mirrors and felt

– “Mad as a Hatter”

• Gold Mining

• Chlor-alkali plants

• Paper plants, agriculture

• Latex paints

• Dental amalgam

• Household products

US Mercury Emissions 1994-95

(metric t/y)

EPA(1997); "Mercury Study Report to Congress Volume 1 Executive Summary" EPA-452/R-97-003 December 1997" Table 3-1

Dental Preparations (0.6)

Laboratory use (1)

Miscellaneous sources (1)

Lamp breakage (1)

Manufacturing (14)

Non-Coal

Combustion Sources (59)

Coal Combustion

Sources (66) Total EPA Estimated

Emissions = 144 t/y

Should be blue as of

2/26/08

U.S Industrial Reported Consumption of Hg (1970-1997)

Schuster et al. 2002 Atmospheric Mercury Deposition During the Last

270 Years: A Glacial Ice Core Record of Natural and Anthropogenic

Sources, Environ. Sci. Technol. April, 2002

• U. S. Geological Survey - total Hg in 97 ice-core samples from upperFremont Glacier, Wyoming

• Regional and global contributions – remote & high elevation

• Over past 100 years

– 20 fold increase in Hg deposition

– 70% from anthropogenic sources

• Over past 10 years

– Deposition has declined – currently a 11 fold increase overpre-industrial levels

Mercury and Other Metals in Sediment Cores

from Lower Cook Inlet and Shelikof StraitHomer Boat Harbor (Z0F1)

Northern Shelikof Strait (Z1F1)

Sediment Quality in Depositional Areas of Shelikof Strait and Outermost Cook Inlet, Principal Investigator P. D. Boehm.

OCS Study MMS 2000-024.

Mercury in Drilling Fluids

• Present in Barite as trace contaminant

• Barite used as weighting agent

• Barite composes 40% of fluid on average

• Mercury concentrations less than 1 ppm

– Regulated by EPA through NPDES permit

Mercury: Barite Fish

Step 1: Mercury must be released from barite

Step 2: Mercury must be in form that is bioavailable

Step 3: Bacteria that methylate must be present

Step 4: Mercury must cross cell wall

Step 5: Mercury must be methylated

Step 6: Methylmercury must be bioavailable

Step 7: Methylmercury is incorporated into food chain

Step 8: Mercury is biomagnified up food chain to fish

Total Mercury in the Sediment

Total Hg Biological

(ppm, dry wt) Effects

< 0.15 Rarely

0.15 - 0.71 Occasionally

> 0.71 Frequently

Source: Long et al. 1995

Gulf of Mexico Offshore Operations

Monitoring Experiment (GOOMEX)

• Conducted by Texas A&M University

• 5 platforms surveyed, 3 studied in detail

• 5 distances from the platform

– 50, 100, 200, 500, 3000 meters

• 5 replicate radii

• 4 sampling periods

– 2 years x 2 seasons (winter and summer)

GOOMEX Results

• Total mercury at 2 of the 50-m locations at 1 of 5platforms ranged above the 0.71 ppm (1.0, 3.5ppm)

• Mercury was from drilling mud

• Drilling occurred between 1975 and 1983, prior to1 ppm Hg limit imposed on barite used in drillingmud

• Drilling mud/cuttings shunted to within 10 metersof the bottom

Total Mercury in Tissues

• Identify chronic, sublethal effects of

offshore oil and gas production activities on

marine organisms

• Samples collected near (< 100 m) and

far (> 3000 m) using nets

• Analyzed invertebrate (shrimp, crabs), fish

liver samples, and fish stomach contents

Total Mercury in Tissues

• Results indicated that there was no

statistical difference between near and far

samples

• Concluded that platforms do not support

enhancement of mercury in marine

organisms

Fates and Effects of Mercury from Oil

and Gas Exploration and Production

Operations in the Marine Environment

• Report by Dr. Jerry Neff

• Reviews wide range of literature

• Hg in the Gulf primarily from natural

sources (0.3% from discharges)

• No evidence that Hg in discharges is getting

into seafood

Concentrations of Total Mercury and

Methylmercury in Sediment

Adjacent to Offshore Drilling Sites

in the Gulf of Mexico

• Report by Dr. Trefry et al.

• Direct measurements of Total Hg and

Methylmercury

• Estimated that 99.9% of Methylmercury is

generated from natural Hg

Study of Barite Solubility and the

Release of Trace Components to the

Marine Environment

• Evaluated whether mercury could be

solubilized from barite under various

conditions

• Concluded that mercury is probably present

in barite as a sulfide and it cannot be

leached out of the barite under standard

environmental conditions

Minerals Management Service

Mercury Studies in Alaska

• A workshop and two studies related to gold

mining off the Nome coast

• Sediment Quality in Depositional Areas of

Shelikof Strait and Outermost Cook Inlet

• Arctic Nearshore Impact Monitoring in the

Development Area (ANIMIDA) and

cANIMIDA

• Coastal Marine Institute, UAF Studies of the

Anthropogenic Contaminants in the Nearshore

Beaufort Sea

Summary

• Mercury is a global pollutant

• Many sources of mercury to coastalmarine waters

• Drilling discharges contain smallamounts of mercury

• Thus far, there is no evidence that oil andgas activities contribute to mercury infish