Contribution of contaminated sites to the global mercury budget

Milena Horvat1, David Kocman1, Nicola Pirrone2, Sergio Cinnirella 2

1Jožef Stefan Institute, Ljubljana, Slovenia2CNR-Institute of Atmospheric Pollution Research, Rome and Rende, Italy

3rd session of the INC on a Hg instrumentNairobi, 2nd November, 2011

Content

• The extent and global distribution of Hg contaminated sites (by Hg source category; by continents)

• Contribution of contaminated sites to the global mercury budget– Quantification of Hg emissions– Hg spreading through hydrological cycles 

Mercury Transformations in Atmosphere & at the air/water/snow/soil Interfaces

(I) Water/lakes/Ocean

(II) Soil and vegetation

Long-range

transport

Local

deposition

Soil

Emission/

Biomass burning

Wet/Dry

Deposition

(III) Sea Ice/

snow

Hg(0)

Hg(II)Hg(0)

Hg(0)

hv

Hg(II)/

aerosols

Cl2/Br2

hv

Hgp

Hg(II) Reduction

hv

Hg(0)

food web XHgCH3

BrCl + hv Br/ClBr2 + hv 2BrBr/Cl + O3 BrO/ClO + O2

BrO/ClO + Hg0 Br/Cl + HgOBrOH/ClOH + Hg0 HBr/HCl + HgO2Br/2Cl + Hg0 HgBr2/HgCl2

Surface microbeshvhv

zooplankton

fish

Industry

What is a contaminated site?

• "A site at which hazardous substances occur at concentrations above background levels and where assessment indicates it poses, or is likely to pose an immediate or long-term hazard to human health or the environment."

ANZECC (1992)

What is a hot spot?

“The definition of hot spots depends upon the medium that is contaminated. Generally, for water, a hot spot exists if contamination results in a significant adverse effect on the beneficial use of that resource and if restoration or protection of the beneficial use can occur within a reasonable amount of time. For media other than water, a hot spot exists if the site presents an unacceptable risk and if the contamination is highly concentrated, highly mobile or cannot be reliably contained.”

DEQ, 1998

The extent of contaminated sites

• CONCENTRATED “HOT SPOTS”– Active

• Intentional (use of Hg in processes and products)

• Non intentional (Hg as by-product)

– Historical • (mining, industrial waste,

sludge…)

• DISPERSED– Catchments impacted by Hg– Coastal areas impacted by Hg

Inventory of contaminated sites by source category• Mercury mining and smelting• Chlor-alkali industry• Precious metal processing: large scale• Artisanal and small-scale gold mining• Non-ferrous metal production• Other industrial and urban sites

– Acetaldehyde production– Vinyl chloride and vinyl acetate– Oil refineries– Urban landfilds

Mercury contaminated sites

GLOBAL PRESPECTIVE:• 70% of CS concentrated in industrial regions of Europe and N America• Asia, India: number of CS increasing due to rising use of Hg in various

products and processes

CSs vs. meteorological and land cover conditions

New IdriaProduction: 17.000 tPrecipitation: 330 mmReleases: 1.5 kg/yr**

IdrijaProduction: 120.000 tPrecipitation: 2000 mmReleases: 1000 kg/yr

New AlmadenReleases: 4-30 kg/yr*

* Thomas et al., Geochem (2002), **Ganguli et al., ES&T (2000)

Quantification of Hg emissions from contaminated sites – data needs

Characterization and identification of CS:• Extent and spatial distribution of contamination (Hg

content in soils, delineation of “hot spots”…)• Transport between compartments (erosion rates,

surface/air exchange)• Differential absorption lidar technique, portable

instruments (e. Lumex), flux chamber experiments…

Hg releases into the hydrosphere - data availability

Releases of Hg from CSs – literature overview: • Poorly documented• Short observation periods not adopted to meteorological

conditions• Difficult to determine relative contribution of the contaminated

part of the catchment• Coexistence of various types of Hg contaminated sites

Case studies - lessons learned:• Variability in releases (production, Hg content, control

equipment, mitigation, process…) • Releases are significant: up to hundreds of kg/yr/site • Meteorological conditions the most important factor controlling

releases – majority of transport occurs during flood events

Quantification of Hg emissions and releases – modeling approach

Hg atmospheric emission

Emissions depend on substrate, Hg content, soil temperature, solar radiation, soil moisture

Hg release to aquatic systems

Erosion and runoff depend on land cover/use, geology, pedology, topography, precipitation…

Mercury atmospheric and terrestrial flux from contaminated sites

Name Flux in air(kg yr-1)

Terrestrial*

(kg yr-1) Reference

New Idria (USA) 2.7 (from 0.6 km2) and 15 (from 229 km2) 1.5 Gustin et al., 2002

Ganguli et al., 2000Sulphur Bank (USA) 17 (3.8 km2) Gustin, 2003Ivanoe District, Nevada (USA) 78 (586 km2) Engle et al., 2001

Wanshan (China) 1-5 Wang et al., 2006Lanmuchang (China) 3.5 (3 km2) Wang et al., 2005Almaden (Spain) 1750 Ferrara et al., 1998bIdrija (Slovenia) 60-80 (from 640 km2) 900 Kocman (2008)Mt. Amiata (Italy) 876-964 Ferrara et al.,1998aNew Almaden (USA) 4-30 Thomas et al., 2002San Francisco Bay 50-600 David et al., 2006

Contaminated sites vs. meteorological and land cover conditions

Temperature

Precipitation

Vegetation cover

Total mercury emissions from contaminated sites

Atmosphere(t yr-1)

Hydrosphere(t yr-1)*

Mercury mining 5-20 10-50

Chlor-alkali industry 1-3 2-5

Non-ferrous metal processing 1-5 -

Precious metal processing (large scale)

2-10 5-10

Artisanal and small scale gold mining (ASGM)

50 50-100

Other industrial and urban sites 10-20 -

Total 70-110 70-165Total (A+H) 140-275

Global Mercury EmissionsNatural

5207

Forest fires675

Oceans2778

Forest & agriculture1664

Anthropogenic2320

Global Emission (2008):7438 Mg yr-1

Source: Pirrone et al. ACP, 2010

Volcanoes90

Global Mercury Emissions in Mg yr-1

Natural5207

Global Emission (2008):7438 Mg yr-1

Sources: Pirrone et al. ACP, 2010 Sunderland and Mason, 2007

(~ 4 %)

Rivers to estuaries

(1320 -2760)

(70 -165)

Rivers to open waters

(280-480) (7-16)

Redistribution by currents

(5-10)

Historic accumulation(5000 – 10 000)

(~ 5 %)

Anthropogenic2320

70 - 110

Conclusions (I)

• Total Hg emissions and releases from contaminated sites are between 140 - 275 tons per year.

• Hg releases to the hydrosphere are in the same order of magnitude as the atmospheric emissions.

• >40% of contaminated sites are located at the coast and have for decades introduced waste containing mercury directly into local estuaries (5000 to 10000 tons accumulated).

Conclusions (II)

• Mercury emissions and releases from contaminated depend strongly on the climatic conditions and the topography of the site in question.

• Comparability of data reported in different studies is also questionable due to different approaches used – standardization is needed.

What needs to done?

• Standardized tools to identify and characterise contaminated sites and quantify Hg emissions and releases

• Training and capacity building at a country level

• Improved inventories of contaminated sites

To remember

• Releases and emission from contaminated sites are less than 10 % of the total global anthropogenic Hg release. However, contaminated sites will release Hg for a very long time, if not managed properly and/or remediated.

• Inappropriate management of contaminated sites may further increase Hg releases resulting in an increased risk for local populations and ecosystem.

• Remediation of such sites can be expensive, and the decisions are difficult to take because the issue is complex.