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Mercury Management along the Chain from Remediation to
Final Storage: Principles Facilitating the Development ofBeneficial Mercury Thresholds
Andreas GÖSSNITZER*
Federal Office for the Environment (FOEN)
Worblentalstrasse 68, CH-3003 Berne, Switzerland*E-mail: andreas.goessnitzer@bafu.admin.ch

Abstract
Beneficial management of mercury can be achieved by applying certain logical, technically oriented
principles. Swiss environmental provisions for soil, site remediation and waste have been developed using
these strategic, long-term-oriented rules. Describing the historical development of state-of-the-art techniques
might help others shorten their own pathway to development. This paper reviews development of these rules
and gives practical guidance and a comparison of data in the specific matter of mercury. Special attention ispaid to the design of a threshold system within the chain starting from observation, proceeding to remediation,
followed by treatment and ending with final storage. Thresholds are shown not necessarily to be rigid borders,
but beneficial frameworks, which can even be flexible to local circumstances if designed well. The overalltarget of the demonstrated strategy is to keep the anthroposphere safe from hazards and at the same time
maintain the lithosphere in a way that does not add new risks of environmental damage. Finally, for a few
holistic cases, keeping in mind the targets of the Minamata Convention, practically proven elements of atransparent and lucid management system for mercury are suggested. As in many processes, involving all
stakeholders in a transparent and integrative way is crucial for success.
Key words :	clarke values, mercury, remediation, soil, threshold, waste

1. Introduction
Following preceding agreements such as the Aarhus
Convention and the Genève Air Emission Reduction
Protocol from 1972, the Minamata Convention enteredinto force in August 2017 with a clear mandate to protect
human health and the environment from the adverse
effects of mercury. Amongst other countries like Norway,
Switzerland played the role of facilitator for theconvention from the start. The basis for this engagement
is twofold: on the one hand, the long-term engagement
and rich experience of the Swiss in several international
environmental treaties such as the Basel, Stockholm andRotterdam conventions were brought in to facilitate theprocess to establish this new Convention. The otheraspect is the historical and still growing expertise of
Swiss industry in chemicals and pharmaceuticals,
including their treatment and disposal. The latter haveincluded the use and treatment of mercury in different
processes, applications and products. Although most ofthese applications are no longer legal, the technicalknowledge for treating mercury still exists and is used byseveral corporations. Last but not least, the uses of
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mercury in Switzerland described herein have resulted incontamination of sites. Most of these are undergoing
remediation nowadays or have been cleaned up already,using a national fund to support these activities througheffective funding from a landfilling fee. Again even theseprojects create expertise and capacity, as well as establish
regulations in their specific domain. This paper reviews
the milestones of Switzerland’s development of a stateof-the-art mercury management system starting in the
1970s. Retracing this pathway may help others facilitate
their own processes to improve environmental conditions.
Additionally this paper aims to provide hints on specificchallenges of the Convention, e.g., the process ofestablishing thresholds for mercury waste.

2. Development of Environmental Law
Environmental law in Switzerland was notestablished on the basis of a uniform concept, but as acontinuous reaction to specific problems that were
occurring. Following changes to the country’s economy
from mainly agricultural to that with a strong second
industrial leg in the last century, the first environmental©2020 AIRES

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Fig. 1 Emission and Deposition of mercury in Switzerland (kg/year). (FOEN (2017), MSC-E (2017), Ritscher et.al. (2018))

regulations aimed to improve the quality of water and air(FOEN, 2013).
Today environmental regulation is still problemoriented but much more specific (e.g., biogenetics, climatechange, mercury). As a cornerstone, the Swiss
Environmental Protection Act (EPA) was established in
1985. The economic boom in these decades laid the groundfor a strong increase in the amount of waste, which wasthen tackled by the internationally well-perceived
Technical Ordinance on Waste (TOW), according to whichwaste had to be recycled after treatment or deposited in asuitable landfill site in an environmentally sound manner.
The effectiveness of the TOW provisions had a positiveenvironmental effect, for example, mercury emissions to
air have shown a reduction by 90% since 1990. Side note:
In the same period, deposition did not drop by the same
percentage, suggesting global transport mechanisms for
mercury and its compounds (Fig.1). TOW in its current
format as the Ordinance on the Avoidance and the
Disposal of Waste (ADWO, in force from 2016) is again
a ground-breaking instrument as it settles new issues suchas phosphorus recycling and handling waste fromconstruction and demolition works (SFC, 2015) whilestill respecting proven basic principles.
Several additional Swiss environmental ordinances
provide rules with respect to mercury (particularly forsoil and remediation of contaminated sites). Nevertheless,
if treatment of these materials is intended, the materials
derived have to be handled as waste. This lays the groundfor further consideration in this paper, examining the roleand design of mercury waste management.

3. Basic Principles
In the years during development of TOW some basic
principles were established as a beneficial framework andtouchstone for this policy. These rules have provenhelpful and are still applied today in updated versions of
the environmental provisions. Chapter 2.2 of Bundesamt
für Umweltschutz (BUS, 1986) gives a set of scientificand technical guidelines that can facilitate the setup of anenvironmentally safe management system for mercury.

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3.1 Treatment and Recovery
Anticipating the now widespread rules of the circular
economy, the following notion for tackling waste
treatment was presented for the first time: “All waste
treatment systems shall produce only two types ofmaterials: reusable material and material suitable for final
landfilling.” With respect to mercury, this principle today
is a core consideration of the Minamata Convention. The
now evident toxicity of mercury makes the removal of
the element from economic cycles to the utmost degree
desirable. As mentioned above in the Introduction, Swisscompanies have developed vast experience in thetreatment of mercury waste to fulfill this task. The
diminishing usage of mercury products on the other hand
generates a continuous flow of recovered mercury forstocks or landfilling, so clear rules and procedures for the
final disposal of mercury will be crucial to fulfilling thegoals of the Convention.
3.2 Landfilling
Both the aforementioned TOW and ADWO containdetailed provisions for landfilling of wastes, including
thresholds for mercury. The main long-term consideration
for landfilling is that landfilling shall be considered atransition of the material from the anthroposphere to thelithosphere without incurring environmental damage toeither of them.
Substances are suitable for final storage if they canbe kept long-term in an appropriate environment (in geophysical and geo-chemical terms) in a way so that they
are releasing only substances which cause no harm to air,water or soil. At the site, final disposal shall be substancespecific: only solids are considered appropriate for final
disposal.
3.3 Petrologic Approach
The petrological approach (Zeltner, 2002) was
initially used to evaluate and project the behavior ofresidues derived from waste melting processes. It
combines geological modelling, petrographic evaluation,material flux analysis and long-term experience withalteration and erosion. As a result, technical processes

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Mercury management from remediation to final storage
shall be steered in a dedicated way to gain materials of
so-called “final storage quality,” which in most cases
result in a chemical and specifically mineralogicalcomposition similar to the Earth’s crust.
The guidance from BUS (1986) explains the same
circumstances as follows: “Waste treatment processes
shall be designed in a way that environmentally harmful
substances, can be derived in a concentrated form, andenvironmentally harmless substances shall be in a form
similar to soil or the Earth’s crust.” As Switzerland has arange of contaminated sites and some of the sites have tobe remediated, the lesson learned was to avoid thebuildup of new landfills that produce harmful emissions
to the three environmental compartments of air, water andsoil.

4. Threshold Systems and Levels
Prior to specification of a material as a waste,decisions have to be made, in most cases using chemical
analyses and applying national legislation or guidelines.
To facilitate triage of mercury contaminated sites or soils,
ART (2013) recommends three levels of thresholds:
background, observation and remediation levels (Fig.2).
The Swiss guideline to derive threshold values (ifthey are not present in existing policies) sets a stepwise
approach to effectively assess the whole chain frominvestigation to remediation and finally, waste
management procedures, keeping in mind human health61

and environmental soundness. (BAFU, 2013)
The guideline uses US-EPA Regional Screening
Levels (RSL) and the slope factor to evaluate toxicity andcombines these with an exposure scenario defined by
SFC (2017) to establish remediation thresholds.
Derivation of landfilling thresholds starts with anassessment of the local geogenic background levels. Thisapproach enables concentration levels to be differentiateddepending on the genesis of the rock on-site, which canbe remarkably different (e.g., mining areas with highnaturally occurring mercury minerals) (Fig.3).
As a core element for evaluating the landfilling
threshold, a so-called virtual leaching test is used as
represented in equation (1).
ct = cw·(Kd+(W/S·1/ρw)・・・(1)ct = threshold (total solid concentration) [mg/kg]
cw = conc. of constituent in pore solution (leachate)[mg/l]
Kd = solid/water distribution coefficient [liter/kg]
W/S = solid/water ratio [1]ρw = density of pore-water [kg/liter]
4.1 Background Mercury Levels
As a definition, if the mercury concentration remains
under the so-called background level, it produces no risk
to human health, animals or the environment.
As deduced above in Section 3.3, Earth-crust values
build a logical basis for development of backgroundlevels. Various sources in literature show the abundanceof mercury in Earth's continental crust to be between 0.05
and 5 mg/kg, also known as clarke values. Table 1 (ART,

Table 1 Mercury background level in different countries. (ART,2013, SFC 1998)

Country

Fig. 2 Schematic diagram of levels to differentiate measures inmanagement of mercury of soil or contaminated sites.

Fig. 3 Risk based scheme to derive threshold values for remediationand landfilling. (BAFU, 2013)

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Background mercury Comments
value (mg/kg)

0.05
Belgium(Flanders)
China
0.15
China
0.3 – 1China
1.5Czech Republic 0.4
Germany
0.1 – 1Finland
0.2
France3.5
Netherlands
0.3 – 0.5
Norway0.05 – 0.2
Slovakia
0.3
Switzerland
0.5
Sweden2.5

Nature reserve area
Agriculture
Forestry
Dependent upon soil type

Soil (SFC, 1998)
Industry

4.2 Mercury Levels Necessitating Observation

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Table 2 Range of mercury observation values for different
land-use categories. (ART, 2013)Land use category

Range: Mercury observation
values (mg/kg)

Agricultural

0.362 – 10

Industry2 – 4000

Gardening, sports, playgrounds 1 – 400
Housing

0.83 – 600

Other

0.1 – 36

Table 3 
Mercury remediation values for different land-use
categories. (ART, 2013, SFC, 2017)

Country

Category

Mercury remediation
value (mg/kg)

Belgium

Agriculture

2.9

CanadaAgriculture

6.6

FinlandIndustrial

5

FinlandNone Industrial

2

Germany

Agriculture

2

Switzerland

Children’s
Playgrounds,
Allotments22013) summarizes background levels in terms of mg/kg.
A total of 82 literature sources provided the basis forthe mercury observation levels in ART (2013). Table 2
displays these concentration values, recorded for several
land-use categories. The rather wide range of values
results from different definitions of the term “observationlevel” in most of the countries, for instance a given value
can trigger restriction of an intended land use or, at aminimum, the obligation to observe or investigate the onsite situation in more detail. The recommendation is to
apply the risk analysis approach.
4.3 Mercury Levels Necessitating Remediation
Similar to the sites under observation, regarding
remediation there are a wide ranges of definitions andmeasures to take if a given threshold is exceeded, e.g.,decontamination (removal of the contaminant),
containment (prevention, neutralization or reduction ofcontaminant diffusion) or restrictions on land use. The
latter can be an option if remediation costs exceed the
locally bearable level (Table3).
Switzerland applies a strict definition of its levels for
remediation. SFC (2017) defines the obligation to
remediate if the given values overshoot the limits. In therelated ordinance, the mercury level requiring
remediation of allotments (community gardens) andchildren’s playgrounds was lowered from a value of

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5 mg/kg to 2 mg/kg in 2015. The Swiss level for
remediation of lands for agricultural use and horticulture
was deduced in ART (2013) resulting in a level for
mercury remediation of 20 mg/kg.

5. Mercury Waste Management
The chain of sustainable management of mercury
ends with treatment and final disposal as a waste. In thepast Swiss industry with its strong focus and vast
experience on chemical and pharmaceutical products,
caused mercury contamination incidents which have been
remediated or still await remediation.
5.1 Mercury Waste Treatment
Swiss waste management firms play an importantand innovative role in the field of mercury waste
treatment.
One such firm, founded in 1989 with a state-cofunded operation, is dedicated to thermal treatment ofbatteries. The cooperative (which today is a subsidiary of
an international waste management company) became a
global player in the field of mercury treatment. Their
scope of activities has expanded over time, so today,
treatment of catalysts and activated carbon, in addition tobatteries and various types of mercury-containing
products, is their core expertise. Subsequently, in
accordance with the aims of the Minamata Convention,
the company developed a treatment plant to convert
metallic mercury into its sulfidic form (HgS, cinnabar).
This process provides the next-to-last step for producing
the aforementioned final storage quality of mercury.
Excavated salt mines provide the ultimate step today
through their final disposal services for mercury in its
stable, naturally occurring form as mercury sulfide(Fig.4).
To treat waste derived from mercury-contaminatedsites in the Swiss canton Valais, another treatment facility
started operation in 2019. The thermal process reclaims
mercury and enriches it for further processing. The
remaining matrix shall reach mercury levels suitable for astandard landfilling operation or even utilization inconstruction works.
5.2 Recovery and Landfilling Operations
As stated in Swiss Environmental Report 2018 (SFC,
2018), 84% of all waste falls under the categories of
excavation and demolition materials. Efforts are being
made to increase recovery of this high volume waste
stream. In the same logic as discussed above in Section 4
to reach qualities similar to the composition of the Earth’s
crust (or background levels), the provisions of the Waste
Ordinance (SFC, 2015) include mercury thresholds to beconsidered as unpolluted or to restrict landfilling withthresholds according to Table 4. Demolition andexcavation materials with mercury levels below 0.5 mg/

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63kg are considered unpolluted and therefore can be kept in
the economic cycle continuously to fulfil the goals of thecircular economy.

environmental issues, as well as to reported issues. The
following elements have helped to establish best practice,specifically in the field of mercury:

5.3 State of Techniques and ProceduresManagement of mercury has improved even in the
short period of time since the Minamata Convention went
into effect. Its guidelines, as well as corresponding
corporate innovation, have brought progress in fulfilling
national provisions as well as the Convention’s
objectives. Swiss best-practice in that respect is strong
cooperation between industrial associations, enforcement
bodies (cantons) and governmental authorities. Swissauthorities have had very positive experience establishinga state-of-the-art technique working group involving the
aforementioned stakeholders. It enables exchanges andquick action in response to new provisions and acute• Transparent, well-documented sampling procedures (ifneeded by third parties)• Complete mercury mass balances of treatment facilities• Tracking of the value chain• Verification of intended mercury uses if not brought tofinal disposal

Fig. 4 Final storage of drums in a excavated salt mine deposit.

6. Conclusions
A holistic approach and view on the management of
mercury is helpful toward achieving the goals of the
Minamata Convention. Considering the whole value
chain of this metal and its substances and applying bestpractice for each of the steps is important.
Mercury thresholds provide clarity and transparency
along the cycle from products to waste and final disposal.
This survey shows that thresholds can be handled with acertain flexibility, recognizing the needs of local
circumstances, e.g., the mining industry. As a firstpriority, treated materials should reach a degree of qualitythat will enable them to be used in the economic cycle
without damaging human health or the environment.
Secondly, residues from treatment should be broughtback into the geological cycle in a form which is stablelong-term and the degradation of which does not create
the need for remediation.

Table 4 Mercury threshold in the Waste Ordinance (SFC, 2015)

Annex 3 (ref. in Article 17) Criterion for demolition and excavation material 0.5 mg mercury/kg dry matter(unpolluted)
Annex 3 (ref. in Article 17) Criterion for demolition and excavation material 1 mg mercury/kg dry matter(subject to further use in construction materials)
Annex 4 (ref. in Article 24) Criteria for waste, used as raw material in
1 mg mercury/kg dry matter
cement and concrete production
1 mg mercury/kg dry matter
1) Use of waste as raw material and raw
mix corrective in cement clinker production2) Use of waste as alternative fuel in cementclinker production
Annex 52 mg mercury/kg dry matter
Criteria for landfilled waste
0.01 mg mercury/liter dry matter (leaching)1) Type B landfills (inert waste)2) Type C landfills (solidified MSWI1fly ash) The total content of mercury may not exceed
5 mg/kg dry matter for metal-containing,
inorganic and badly soluble waste
3) Type D landfills (MSWI slag)
5 mg mercury/kg dry matter4) Type E landfills (other wastes, slightly reactive) 5 mg mercury/kg dry matter

Reference measurement methods for total mercury concentration: For sample preparation, microwave pressure digestion with aqua regia or conc. HNO3 or
HNO3/H2O2 with a 0.5 to 2 g sample of material; measurement by cold-vapour AAS, AAS, ICP-MS, AFS (ISO 12846).

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Andreas GÖSSNITZER
Andreas Gössnitzer currently works for the Swiss
Federal Office for the Environement (FOEN). He
heads a section, which deals with the circular
aspects of raw materials including all types ofwaste. His enthusiasm for the management of
mercury waste streams started at his former
position, leading a team for the Swisstransboundary movement of waste and today continues in the field ofdefinitions of best available techniques (BAT). He has long-time experiencein cement industry, with special focus on waste streams in the mining, metal
and waste sector. His educational basis is a master of the University of
Leoben / Austria and a MBA of the University of St. Gallen / Switzerland.

(Received 14 December 2019, Accepted 8 June 2020)

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