Abstracts from September Issue of ASCE Journal of Cold Regions Engineering

ABSTRACT: Literature on the effects of lowered temperature on the toughness of random short fibre composites have neither offered a clear trend nor explained the mechanisms of failure. In this work, unnotched and notched strengths at room temperature and -30°C of two glass mat polypropylenes with different fibre architectures are investigated. Observations are explained based on models for Young's modulus and notch sensitivity. Increases in strength and stiffness with lowered temperature are caused by increased matrix modulus and yield stress. Fibre bridging operating in a damage zone of substantial length was the major toughening mechanism and forms the basis for the modelling approach for notch sensitivity. Increased notch toughness at low temperature is caused by increased work of fracture in the damage zone. The increased matrix modulus and yield stress led to an increased toughening efficiency of short fibres.

By J.H. Lever, G. Gooch, A. Tuthill and C. Clark

ABSTRACT: Communities located on small, northern rivers can experience severe breakup ice jams. While flood damages may be significant locally, they are often insufficient to justify the cost of conventional flood-control structures. Environmental concerns also tend to render these structures unattractive. A new, low-cost structure appears to be well suited to control breakup ice jams on small rivers. It consists of massive sloped blocks, partially buried in riprap, placed across the river adjacent to a natural floodplain. The blocks will arrest a breakup ice run and form a stable, partially grounded ice jam. Trees or boulders on the floodplain retain ice pieces in the river channel while allowing flow to bypass the structure. Large gaps between blocks allow easy fish and canoe passage. Refrigerated hydraulic model tests indicate that the structure should perform well even during severe breakup events. A prototype built in Hardwick, Vt., has performed well during the four mild breakup events experienced to date. Its cost of $3,600/m of river width represents about an order-of-magnitude reduction compared with previous ice-control structures.

By Mark A. Tumeo, Member, ASCE and David A. Guinn

ABSTRACT: Biological treatment has become increasingly popular as a remediation method for soils and groundwater contaminated with petroleum hydrocarbon, chlorinated solvents, and pesticides. Bioremediation has been considered for application in cold regions such as Arctic and subarctic climates and Antarctica. Studies to date suggest that indigenous microbes suitable for bioremediation exist in soils in these regions. This paper reports on two case studies, one in Antarctica and one in the subarctic, in which indigenous bacteria were found that were capable of mineralizing petroleum hydrocarbons in soil contaminated with jet fuel and polychlorinated biphenyls (PCBs) in Antarctica and pentachlorophenol (PCP) and diesel in contaminated soil in the subarctic southwestern Alaska. However, in both instances, ex-situ treatment allows greater control over soil temperature, a limiting factor in cold climates.

By Andrew Tuthill, Member, ASCE and Gordon Gooch

ABSTRACT: Ice conditions hamper winter navigation on major US waterways. Accumulations of broken ice in the upstream approaches to locks and dams can interfere with lock operations and hydropower production. Conveying this ice downstream through dam gates can be difficult because of the low water velocities found in pool areas, and the limited available discharge for ice passage during winter low-flow periods. A physical hydraulic model study, using real ice, investigated the design and operation of submergible gates for ice passage at the US Army Corps of Engineers Starved Rock Lock and Dam on the Illinois Waterway. Alternative gate locations were tested for a range of gate discharges and ice conditions. The effects of hydropower diversions, navigation, and high-flow air screens on ice passage were examined. The study found that, under some ice conditions, submergible gates alone may not be adequate for ice passage. During these times, tow and barge transits through the lock and deflector bubbler operation would need to be coordinated with submergible gate operation to pass ice.

By Philip J. Parker, Student Member, ASCE and Anthony G. Collins, Member, ASCE

ABSTRACT: A preliminary investigation has been performed to determine the feasibility of conditioning a sulfite pulp mill waste activated sludge (WAS) by freezing and thawing. A series of experiments quantifying dewaterability was performed on the frozen and thawed sludge ("conditioned") and compared to sludge that had not been treated by freezing ("unconditioned"). These experiments consisted of quantifying the change in settling rates, filterability, and maximum attainable solids content, and were performed at -5°C, -10°C and -25°C. As a result of freeze/thaw treatment, dewaterability improved dramatically for the conditioned sludges, with the greatest improvement noted for samples frozen at higher temperatures.

FOCUS ON ENVIRONMENTAL REMEDIATION

Abstracts from Proceedings of 8th International Conference on Cold Regions Engineering

Fairbanks, Alaska - August 12-16, 1996

To evaluate the potential use of spray freezing technology in removing inorganic and organic contaminants from recycled oil sands tailings pond water, a field study was carried out at the Syncrude Canada Ltd. mine site in February 1994. A plastic lined containment area was prepared to collect the spray ice.

A spray ice pile measuring 18 by 12 m in plan and 5 m high was produced after 15 hours of spraying. Various water samples and ice samples were collected. Parameters such as pH and electrical conductivity, Na+, C1- and total organic carbon (TOC) concentrations were measured on these samples.

The laboratory measurements of the ice cores showed a reduction in the average concentration of C1- of between 90.8% and 98.7% and a reduction of 97.8% in the melt water which drained downward through the spray ice mound. These reductions were based on the original concentration measured in the source water used during the spraying test. The lower reduction was measured using the ice cores retrieved in March and the greater reductions occurred in the ice core obtained in April 1994. Similar reductions were measured for the Na+ ion using the same samples. The total organic carbon (TOC) measurements on the ice core showed a reduction of between 89.3% and 98.9% while the melt water showed a reduction of 93.4%. The electrical conductivity's of the ice cores decreased by between 91.5% and 99.1% and the conductivity of the melt water decreased by 95.7%.

The field test results demonstrated that winter spraying of the recycle water with initial flush diversion for further treatment was effective in decreasing both organic and inorganic contaminants in this industrial recycle water.

By Paul Dworian

Naturally occurring organics may be reported as false positives during environmental testing, since they are often similar in molecular weight and chemical character to anthropogenic hydrocarbons. Background concentrations of diesel range organics (DRO) as high as 3,600 milligrams per kilogram (mg/kg) in soil and 0.62 milligrams per litre (mg/L) in groundwater have been reported in Alaska using EPA Method 8100 modified. In some cases, these background concentrations are above state regulatory cleanup levels for DRO.

Chromatograms for a diesel fuel sample generally show a range of hydrocarbons present between C-10 to C-24, with the highest concentrations around C-18. In contrast, chromatograms for background DRO appear to be dominated by compounds heavier than C-18, with the highest concentrations in the C-20 to C=24+ range.

There are four potential solutions to the problem of naturally occurring DRO in environmental samples. The first is to collect representative background samples from the site. Once an upper limit for the background DRO concentration is established, it could be subtracted from the reported DRO concentrations at the site to evaluate the anthropogenic diesel contribution. Another possible solution would be to focus the investigation on the overall toxicity of the DRO components reported.

It may be possible to utilize laboratory cleanup steps in conjunction with EPA Method 8100m to selectively remove the naturally occurring DRO from the sample prior to analyses. Several experiments with these techniques have shown them to be only partially effective (Brown and Whitsett, 1995).

Another approach is to evaluate and interpret the analytical results where interference by naturally occurring DRO is suspected. The DRO concentration between C-10 and C-18 can be computed, compared to the DRO concentration within that range for the fuel released, and the total anthropogenic DRO concentration estimated based on this comparison.

By Ron Johnson, Doug Kane, Larry Hinzman, Greg Light, and Ann Farris

The Water Research Center participated in a multi-year study to provide a quantitative description of the effects of discontinuous permafrost on contaminant transport in the groundwater at Fort Wainwright, Alaska. A critical part in formulating a remediation strategy is the development or adaptation of appropriate analytical and numerical models to predict the contaminant pathways. Primarily interested in the migration of contaminants dissolved in groundwater, we utilized solute transport models that incorporate both advection and dispersion and can also include the effects of retardation of the solute with respect to the local groundwater velocity. After collecting appropriate hydrologic and water quality data, we performed tracer tests to allow us to estimate several key aquifer parameters. We then performed both analytical and numerical plume modelling calculations to predict plume migration. The results show the possibility of a westward migration over a period of decades, with the permafrost distribution significantly affecting the direction of flow.

By Paul C. Ramert and Wayne L. Eberhardt

The Alaska Department of Environmental Conservation (ADEC) has established cleanup levels for contaminated soil generated by releases and spills from fuel storage tanks (FSTs). In the process of decommissioning and replacing its current inventory of FSTs, the Federal Aviation Administration (FAA), Alaska Region, has encountered varying degrees of contaminated soil requiring treatment. This paper presents treatment results for two biocells operating at the McGrath Station; specifically, it describes biocell treatment system design and operating parameters, and tracks demonstrated hydrocarbon removal rates and trends for gasoline-range and diesel-range organics.

By Timothy F. Gould and Mark Wallace

The establishment and enforcement of cleanup standards for hydrocarbon-contaminated soil and groundwater has led to the rapid evolution of remedial technologies in Alaska. A pilot-scale treatability study was performed at Fort Wainwright, Alaska, to investigate the feasibility of using air injection/soil vapour extraction (AI/SVE) for remediation of contaminated soil and groundwater. The study focused on monitoring remediation rates resulting from volatilization and biodegradation in the vadose and saturated zones. Study objectives included the assessment of contaminant removal rates for each identified treatment process and the estimation of the treatment time required for site remediation. This paper summarizes the results of hydrocarbon removal rate measurements and presents a method for estimating the time required for site remediation.

By K.W. Biggar and J.C.R. Neufeld

A laboratory experimental program was conducted on 30 cm high, wet tamped soil columns of silty sand with a layer of diesel contaminated soil placed on the surface. The soil was cyclically thawed then frozen from the upper surface to approximately half way down the column, maintaining the lower portion of the soil column in a frozen state for the duration of the test program. The results showed considerable migration of diesel into the saturated uncontaminated soil which was subjected to cyclic freezing and thawing, however, no contamination was observed in the permanently frozen soil after up to 8 freeze-thaw cycles.

FOCUS ON TRANSPORTATION - PAVEMENTS

Abstracts from Proceedings of 8th International Conference on Cold Regions Engineering in Fairbanks, Alaska - August 12-16, 1996

Paving in cold climate, particularly in permafrost areas, requires special technical and engineering considerations. This is because under such conditions not only the properties of asphalt concrete at low temperature but also thaw settlement and frost heaving distresses have to be considered in pavement design, construction and maintenance. This paper first presents a general description of the Qinghai-Tibet Plateau Highway, which is the highest highway in the world in terms of elevation. It then discusses the main factors causing pavement surface distresses such as thaw settlement and frost heaving of the pavements in this permafrost region, and finally presents a practical assessment of asphalt pavement design, construction, maintenance and performance prediction. The case study includes: variation analysis of the upper boundary of the permafrost table movement under seasonally changeable environmental conditions, discussion of pavement distresses based on the observed data and field experiments taken from the case study, and evaluation of some empirical methods used for the determination of pavement thaw settlement and frost heaving in this particular permafrost area.

By Maureen A. Kestler

Open Graded Bases (OGB) and Rapid Draining Material (RDM) to promote horizontal drainage of water from pavement systems have not been used extensively in the United States until recently. Drainage layers are now required beneath most Army and Air Force pavements, whether rigid or flexible. To assess the effectiveness of an OGB within a flexible pavement in areas of seasonal freezing and to ultimately evaluate the optimum OGB location within a pavement structure, three test sections with an OGB layer at different depths within the pavement structure were constructed on a USDA Forest Service Road in Berlin, NH. The sections were monitored for surface and subsurface temperature, moisture content, frost heave, pavement stiffness, and meltwater (water introduced by freeze-thaw cycles) collected in the drainage layer. Compilation of field data from these sections constitutes the first in a series of steps to determine the optimum location within a pavement system (in areas of seasonal frost) for OGB placement. This paper discusses drainage test section design, construction, instrumentation, observations to date, and overall strategy for determining the optimal OGB location.

By Seppo Saarelainen

Frost heaving of roads is one of the reasons causing pavement damage in cold regions. In this paper, an approach to the design of pavement structures on frost-susceptible subgrades is presented. The frost susceptibility is described by segregation potential of the freezing subgrade. Design charts are presented both for mineral embankments and for insulated embankments. The thickness of the non frost-susceptible pavement structure or the necessary thermal resistance of the frost insulation can be determined as a function of the desired frost heave level and freezing index of the location at two degrees of frost susceptibility (segregation potential) of the subgrade. This design approach has been applied in the design of streets and car-parks in Finland from the late 80's.

By Robert L. Scher

In cold regions, the orientation and timing of movements along longitudinal pavement cracks are direct functions of two general conditions; seasonal frost action and/or thaw-unstable permafrost foundations. Each category can be characterized by different crack patterns, magnitudes and rates of movement, and boundary processes. Understanding these differences are prerequisites to designing economical new embankments or repairs. Simplified models are presented to qualify the potential boundary processes causing longitudinal cracks in cold regions. A limited review of techniques for mitigating this type cracking is also provided.

By Josten S. Berg and Per M. Noss

In 1979, the field research project "Economical Concrete Pavements" was started. The goal with the project was to get reliable information in order to determine where and how to use concrete road pavements.

The concrete pavement in the 500 metres long Saetre tunnel in the City of Bergen, Norway was part of the entire project, which this paper will present, comparing and emphasizing the concrete slab variables versus the pavement wear and tear after 12 years of use.

The Saetre tunnel pavement consisted of 11 variable concrete sections cast on a 50 mm insulation board or directly on a prepared base course of rocks. The subgrade of rocks was the same throughout the entire road-tunnel. Other slab variables were the concrete thickness and the slabs were reinforced or not reinforced. Results from the pavement registration and comparison between the various slab variables will be presented. Of particular interest is the registrations of the slabs with an insulation board versus comparable slabs without any insulation.

The conclusions of this full scale test project are based on the pavement condition of the final registration in 1991 and the entire life span of the pavement of 12 years.

By Rupert G. Tart, Jr., Mark R. Musial, and Michael E. Krueger

In 1989, the authors of this paper were asked by the Municipality of Anchorage, Alaska (MOA) to conduct a study to determine why some of the recently completed pavements in the Municipality were showing signs of significant distress and cracking. Later in 1992, a follow up study was conducted. Since that time many of the original recommendations have been implemented by the Municipality and the results of these implementations have been monitored. This paper will summarize the findings of the two studies and will report on the performance of some of the pavements which have incorporated the recommendations presented in the two reports.

By Donaldson R. MacLeod and Robin Walsh

Bituminous Surface Treatments (BSTs) have been used in Northwestern British Columbia and the Yukon for the past 15 years. The area is characterized by remote locations with a harsh climate, bog and fen complexes and permafrost.

BST uses range from a form of dust palliative on very low volume roads to an affordable alternative to asphalt concrete on mainline highway systems which have traffic volumes of up to 1,000 AADT. Many of these roads have a high percentage of trucks associated with primary resource development.

There are differences between the management of BSTs and conventional pavements. In contrast to pavement overlays, overlays of BST surfaces do not restore the surface condition to that of a newly constructed BST because of the BST overlay's inability to correct distresses such as rutting and minor distortions. Consequently ride smoothness is not maximized unless other measures are taken.

The development of regression and Markov modelling techniques for BST performance makes possible a comparison of different road surfacing options on a life cycle cost basis taking into account capital, maintenance and user costs. Such cost analyses of BST relative to dust treated gravel and conventional asphalt concrete surfaces indicate that it is a suitable surfacing alternative for northern roads.

NORTHERN EXPOSURE: SOLID WASTE DEVELOPMENTS IN ALASKA

Edited article from "Waste Age", January 1998

As Anchorage grows, so do the demands placed on Anchorage Regional Landfill, owned and operated by the city. This year, the city published a request for proposals (RFP) for the evaluation of future cell sequencing for the landfill. The RFP focused particularly on the design and construction of the next cell. The project has been broken into three phases: planning for future cells, now taking place; designing the next cell, to be completed this winter; and constructing the new cell, scheduled to begin in summer 1998.

Currently, the landfill has four active cells, over about 75 acres, that accept waste. Each new cell adds about five years of capacity within an existing 270 acre area. The landfill, which opened in 1987 and serves the entire municipality of Anchorage, has a planned capacity through about 2050.

Existing cells employ an 80 mil high density polyethylene liner, and a geosynthetic clay liner. Estimates the cost of the construction project to be about $8.5 million.

Currently the landfill takes in about 300,000 tons per year of waste, with about 60% hauled in from commercial hauling companies such as Anchorage Refuse. About 10% is "haul your own," with the rest coming from businesses.

A unique feature of the Anchorage landfill is that they have eliminated a seagull problem that they had at former landfills. They use a net system, like a very large fishnet, over the active portion of the landfill."

Life in the small rural villages of Alaska is a far cry from the urban bustle of Anchorage. Whenever one talks about waste in rural villages, it usually refers to sewage, rather than solid waste. A large percentage of rural Alaskans don't have sewage systems, therefore solid waste improvements are usually on the back burner.

Improving rural sanitation, and eliminating use of the "honey bucket," is a major initiative for Alaska government. But with millions of dollars appropriated to improve rural sanitation, solid waste management is often left behind. It is "very common" in rural villages for solid waste to be dumped on top of the ground.

Funding is a major issue; Anchorage has about half of the population of the state of Alaska, so the Legislature takes care of Anchorage first. Add in the fact that isolation drives up the cost of living, and solid waste management falls pretty low on the priority list in some rural villages.

But the picture is not as bleak as it may appear. Two of the most remote villages in Alaska are about to get new landfills.

The village of Scammon Bay is located on the Yukon-Kuskokwim Delta, one mile from the Bering Sea. It is a wholly Eskimo community, with only about 425 residents, that relies on subsistence activities for survival. Employment is dependent upon commercial fishing, fire-fighting for the U.S. Bureau of Land Management, and various construction projects. The city is accessible only by air and water.

Scammon Bay does have a small landfill, but it has reached capacity. In addition, the current landfill is sited too close to the Scammon Bay airstrip, and it has other operational deficiencies. The new facility is expected to be a one-acre, unlined, Class 3 landfill. A burn box for incineration of materials will likely be included as well.

The project is expected to cost $1 million to $2 million, and the city will own and operate the landfill, although it is not expected to be a "moneymaker. The design will be completed by mid-year 1998 and actual construction will take place in 1999.

The new project will not include any mechanism for recycling, and it may be quite some time before recycling can take place in such an isolated area.

The community of Sand Point is located on Popof Island, in the Aleutian Chain off the Alaska Peninsula. The community is 570 air miles from Anchorage, and has a new state-owned airport with a 4,000 foot runway. It is a mixed Native and non-Native community of about 870 people, with commercial fishing at the heart of local culture. Sand Point is home to the largest fishing fleet in the Aleutian Chain.

Sand Point has a landfill that is also at capacity. A conceptual design for a two to three acre landfill has been completed, and estimates for the cost of construction run about $1 million to $2 million.

The new landfill will have positive economic impacts on the community. In the past the community contracted out its waste collection, but now will bring the operation "in-house," hiring a certified landfill operator. Sand Point recently purchased a new compactor machine for steel cans. The community also collects old corrugated containers, and even has offered technical assistance to local fishermen on how to recycle fishing nets.

Sand Point also conducts a litter prevention program in conjunction with Alaskans for Litter Prevention and Recycling (ALPAR, Anchorage). ALPAR is an organization comprising industry, business, and community representatives that conducts public information campaigns and litter prevention initiatives, with a focus on economic feasibility. ALPAR also coordinates the backhauling of waste and recyclables to the Lower 48.

Through its "Flying Cans" program, ALPAR has helped Alaskan communities to recycle aluminum cans. For the program, ALPAR works with the Alaska Air Carriers Association and smaller air operations to backhaul aluminum cans collected from rural communities. Once at the Anchorage Recycling Center, the value of the materials is recorded before shipment to the Lower 48, and ALPAR signs a check for the recyclables - sometimes for as little as 75 cents - that is sent back to the rural communities.

In Anchorage, a household hazardous waste facility takes care of another part of the Alaska waste stream. Anchorage has one of the first permanent household/hazardous waste collection facilities constructed in the U.S. About 1.2 million pounds of household hazardous waste are collected annually at the 6,000 square foot facility and transfer station.

Anchorage has limited recycling opportunities. . . primarily due to economics, because of our remoteness from the secondary material markets.

Organizations such as ALPAR, as well as the Green Star program, are pushing Alaska to the next level of waste management. In the future, success will be measured not only by whether a landfill is in compliance with standards the Lower 48 has adhered to for years, but also by how well Alaska diverts waste from landfills in the first place.

ABSTRACTS FROM CONFERENCE ON COLD REGIONS ENGINEERING

APRIL 1994

Septage, the waste sludge resulting from septic tanks, has in recent times become a recognized but difficult waste to process. It is estimated that some 20 million septic tanks serve about 80 million people in the United States. A great deal of attention has been devoted to the design, construction and operation of septic tanks themselves and properly so. However, it is equally important to realize that unless the septage is periodically removed from the tank, the system will indeed be doomed to failure. Only during the past decade has septage received the attention it deserves.

This article reports on studies and research conducted by the University of Alaska and the City of Fairbanks, Alaska. Included are definitions, characterization studies, treatability evaluations, and recommendations for alternative processing.

By J.A. Heroux

Located at 82.3N 62.0W, Canadian Forces Station Alert is the most northern permanent settlement in North America.

The wastewater produced by the 250 annual residents is currently discharged, without any form of treatment, into a small lagoon, open to the Arctic Ocean. The goal of this ongoing project is to evaluate such aspects as water quality, benthos sediments, plankton, fisheries, organic matter biodegradability relative to the ecosystem concerned.

The present paper discusses the first phase of the project. A characterization of the wastewater demonstrated that, to a certain extent, it could be classified as domestic sewage. This indicated that it was easily biodegradable and that few toxic effects could be expected from its discharge.

A physical study of the receiving body of water was also undertaken. Water samples were obtained throughout the lagoon and evaluated for physical, chemical and biological characteristics. Benthos and sediment samples showed the dispersion pattern of the wastewater and its effect on the bottom biota. A dye tracer study confirmed the trends shown by the distribution of the water quality.

This preliminary work tends to demonstrate that the impact of the wastes in Alert Inlet is relatively small and even somewhat beneficial to micro-ecosystems of the bay.

By J. Penel, D.W. Smith, G. Putz

A numerical transverse mixing model was applied to study the mixing of the Whitehorse sewage lagoons effluent within the Yukon River.

Transverse mixing was simulated downstream of the outfall at various water discharges for open water and ice cover conditions.

Municipal wastewater management guidelines in the Yukon Territory established two sets of water quality requirements: 1) an effluent quality requirement and 2) a receiving water standard outside of an initial mixing zone which is defined as a volume of water extending some distance downstream from the point of discharge.

The diffusion model was applied to the Whitehorse wastewater. The mixing results were compared with the draft license water quality requirements associated with the two most critical parameters of this study, namely the maximum permissible faecal coliform count, and the maximum permissible ammonia concentration related to fish toxicity. The environmental impact of a potential relaxation in requirements relating to fish toxicity were also evaluated. The transverse mixing model was shown to be a powerful and flexible tool for assisting in sizing a cost effective treatment facility.

The report has been prepared as a reference document for front-line community professionals who deal with contaminants issues and information in their communities. It highlights information from the Canadian Arctic Contaminants Assessment Report (CACAR), which is a major scientific report that summarizes the results of research conducted by the Arctic Environmental Strategy (AES) Northern Contaminants Program (NCP) from 1991 to 1997.

The NCP focuses on the types of contaminants that may be found in traditional/country foods across a wide area of the Canadian north (mainly organochlorines and metals, as well as radionuclides).

The NCP works to:

1. measure contaminant levels in the Canadian north;
2. find out where contaminants are coming from, how they get to the north, and what happens when they arrive;
3. assess effects of contaminants on health of the northern environment, including humans;
4. provide information to assist northerners' decision-making and encourage their involvement in the NCP; and
5. pursue international agreements and cooperation to control contamination at a global level.

Northern fish and wildlife play a critical role in the nutrition, as well as social, cultural, and economic well-being of northern aboriginal peoples. The need to protect these traditional food sources and the benefits and way of life they represent, is a driving force behind Canada's leadership role in demanding international action on contaminants.

Contamination levels of wildlife are largely related to the animals' feeding habits, with predatory animals having higher levels than those which feed directly on plants. Age, quantity of fatty tissues, reproduction, and migration to contaminated areas outside the Arctic are other important factors that may influence contaminant levels in wildlife.

The main contaminants found throughout the northern food chain are organochlorines (OCs), metals, and radionuclides. The key OCs of concern in northern food chains are pesticides (e.g. toxaphene, chlordane, and DDT), and the industrial chemical PCB's. The primary source of OCs to the north is other countries, and the primary route of transport is the atmosphere. OCs are mainly found in fatty tissues of predatory animals high in the food chain, and have been found at elevated levels in marine mammal fat and burbot liver. Levels of OCs are very low in land animals and most fish. There are no major differences in OC concentrations in wildlife across the Arctic, however, slight regional differences have been observed and are attributed to the pathways of the major air currents which carry contaminants into the north. OC levels in Canadian Arctic wildlife are lower than levels in comparable species from industrial and agricultural regions of the world.

The key metals of concern in northern food chains are cadmium and mercury. There are natural sources of mercury and cadmium in northern rocks and soils, and levels in wildlife are thought to reflect these natural levels.

Mercury levels in flesh of fish from certain lakes in the north may be elevated due to natural sources. Mercury levels in marine mammals may also be elevated due to natural sources. Although research is scarce, results now under debate are beginning to suggest that certain marine mammals and possibly humans may have natural defences that enable them to change mercury to non-toxic forms in their bodies. Human-made inputs are however thought to be the cause of increases in general environmental levels of mercury in recent years.

Cadmium has been found at somewhat elevated levels in caribou organs (liver and kidney), however the major source of human exposure to cadmium is smoking.

Levels of human-made radionuclides are quite low in northern people and wildlife, and have declined over 10-fold since atmospheric testing of nuclear weapons was stopped in the 1960s. Levels of natural radionuclides in northern wildlife and people are higher than in the south, and this is thought to be related to the nature of the food chains in the north. In general, radionuclides are not considered a health concern for northern people and animals.

Following release from the source, organochlorines may travel to the Arctic in multiple cycles of i) evaporation, ii) transport by air, iii) condensation. This is called the grasshopper effect and can allow these types of contaminants to travel great distances in a short time. Methylmercury may also travel in this manner. Metals and the radionuclides are thought to travel only by a single "hop" of i) release from the source, ii) transport by winds, iii) deposition. Therefore, they do not travel as far as OCs. Transport by atmosphere can occur in a matter of days and air is the major way that contaminants are carried into the Arctic.

Movement of contaminants via oceans is much slower than by air, however oceans play an important role in cycling of contaminants through the environment.

Results from health risk assessments of contaminants in food should be handed differently for traditional/country food than for storebought food. Benefits of traditional/country food must be factored into the assessment, and the risks of not consuming these foods must be weighed against the risks that may exist due to current contaminant levels. In contrast, specific commercial products on store shelves do not have the same lifestyle/nutrition/economic importance as do traditional/country food, and a decision to remove a specific product from the marketplace is made more easily because it is unlikely to have major consequences on people's nutrition, lifestyle, or culture.

Contaminants in the food chain are not thought to pose a direct threat to the health of adult humans. Contaminant levels in traditional/country food are low enough that a single serving, or even many servings, will not make someone sick. However, lifetime stores of contaminants in people may be at a level where an unborn child may be at risk of subtle effects related to learning ability, memory, and resistance to infection.

The benefits of consuming traditional/country food are vital to the health, nutrition, and culture of northerners. At present, the short-term effects of not consuming traditional/country food are considered to be a more serious risk than the possible risk of long-term, subtle effects that may be associated with current levels of contaminants in Arctic food. People who wish to lower their contaminant intake can do so by placing more emphasis in their diet on traditional/country food species that are lower in fat, but still high in nutritional content (e.g. caribou and fish) while moderating their intake of marine mammal fats.

Contaminant levels in people vary according to their diet. People whose diets include animals higher up in the food chain, tend to have higher contaminant levels than people whose diets consist mainly of plants and plant-eating animals. People who consume high quantities of marine mammal tissue tend to have relatively higher levels of OCs and mercury than people who eat land animals and fish. For these reasons, people in southern Canada generally have lower contaminant levels in their bodies than northerners with a traditional/country food diet. Little is known about the potential for effects from the concentration of contaminants currently found in northern foods and people. The levels are not thought to pose a direct risk to the health of the adult, but some people are in a range where there is concern about the potential for effects on the unborn child.

Reduction of contaminant levels in the north requires international action because most of the contaminants entering the Arctic come from other countries. The quantities of these chemicals that have already been released to the environment, and the long time it takes for them to break-down, mean that it will take some time before levels in the Arctic are significantly reduced. However, results from elsewhere show that international controls can result in improvements to environmental levels of contamination.

Ultimately, to eliminate food chain contaminants in the north, release of contaminants throughout the world needs to be stopped. This can only be done through international cooperation.

Within the north, we also have to find and eliminate local sources. Although their contribution relative to the total input of contaminants to the north as a whole, may not be large, they still play a role. Furthermore, they are a concern at the local level and therefore need to be addressed.

Canada has taken a leadership role at the international level to demand controls on the release of persistent organic pollutants (POP's), most of which are OCs. We are in the process of negotiating international laws that will apply across the northern hemisphere and are aimed at controlling at least 15 POP's, including OC pesticides, industrial chemicals and wastes (including the OCs of key concern in the northern food chains), with the possibility of adding more to the list in coming years. It is hoped that an agreement will be signed, by the end of 1998, by the countries that are in the region which includes Europe, Canada and the United States. A similar process, also targeted for 1998, is underway for controls on the heavy metals, mercury, cadmium, and lead.

Canada has also worked with countries in the southern hemisphere, to find ways that they can stop using POPs without endangering the health of their own people. This type of work will also be combined with international laws at the global level. Negotiations will begin in 1998 and should take about three years to complete.

The eight Arctic countries (Canada, Denmark, (Greenland), Iceland, Norway, Sweden, Finland, Russia, and the USA) have an agreement, the Arctic Environmental Protection Strategy (AEPS), through which they cooperate to examine and act on environmental issues in the north. The Arctic Monitoring and Assessment Program (AMAP) is the part of the AEPS that deals with contaminants. In 1996, the Arctic Council was formed as a way for the eight Arctic countries to work together on many issues of common concern in addition to the environment. These include: economics, development, community health, culture, communications, and transportation. The AEPS plays an important role in the Council's activities on the environment.

Within Canada, federal policies have recently been developed by Environment Canada to deal specifically with toxic substances, among them the contaminants of concern in the Arctic. These policies are intended to prevent releases within Canada of contaminants of concern, they also call for clean-up of sites, and encourage Canadian leadership in calling for international action.

Finally, within the Canadian north, the Arctic Environmental Strategy (including the NCP) was developed. The importance of the work done under this program to addressing concerns in the north has been recognized, and action on contaminants and waste is expected to continue into the future.