Course:EOSC270/2023/Toxic Substances in Arctic Ecosystems

What is the problem?

Introduction

The Arctic is a remote and sparsely populated area, with little industry. Despite minimal industrial emissions, chemical pollution is a serious threat to ecosystems and populations of the area. The most prominent contaminants found in the Arctic include persistent organic pollutants (POPs), such as DDT, PCBs, and dioxins, and heavy metals, such as mercury and lead.  Both are harmful as they accumulate in the environment and pose a threat to ecological and human health.

Toxic Substances found in the Arctic

Persistent Organic Pollutants (POPs)

Persistent organic pollutants (POPs) incorporate a multitude of toxic substances and their byproducts that are caused by anthropogenic inputs. In the Arctic, POPs classified as organohalogen contaminants are particularly detrimental due to their stable chemical makeup and long half-life. These characteristics, along with being fat-soluble, cause them to be persistent in the environment, be transported by wind and ocean currents, and build up in food webs. Persistent organic pollutants enter the environment through their use in industrial applications, pesticides/insecticides, and can be generated as by-products of many industrial processes. Some of the most prominent in the Arctic include DDT (dichloro-diphenyl-trichloroethane), the first modern synthetic insecticide produced, and PCBs (polychlorinated biphenyls), used in many industrial applications from electrical, heat transfer, and hydraulic equipment to plasticizers in paints, plastics, and rubber products.

Heavy Metals

Metals occur naturally in the environment in different forms. They can appear as ions dissolved in water, as vapours, salts, or minerals, and can be bound in molecules or attached to particles in the air. Natural and anthropogenic processes and sources emit heavy metals into air and water. Despite the fact that many plants and animals depend on metals for micronutrients, certain forms can be toxic and harmful to the ecosystem. In the Arctic, heavy metals are released into the environment from natural sources (rock weathering and permafrost thawing) and anthropogenic factors (mining, industrial processes, and burning of fossil fuels). Metals are elements, meaning that they cannot degrade, only change form. Once they are released, they can persist in soil, air, and water for extended periods of time (how long find a research article of degradation rate). The most prominent in nature are mercury, cadmium, arsenic, chromium, nickel, copper, and lead. When mixed with water, mercury converts into methylmercury, which is highly toxic.  Mercury can also cause Minamata disease. Heavy metals that are of the most concern to the AMAP are mercury, cadmium, and lead. This is because these metals are already found in some regions of the Arctic, and transport from other regions adds to the already naturally high levels.

How do these toxic substances get to the Arctic?

The Arctic is a sparsely populated region with very little large-scale industrial development, meaning that the area inputs minimal amounts of toxic substances, like POPs and heavy metals, into the environment. Most of the toxic substances that build up in the Arctic originate in more southern regions. In lower latitudes, toxic substances are released into the environment through industrial processes such as wastewater disposal, atmospheric deposition, and runoff. After these toxins are released into the atmosphere, they migrate north towards the Arctic by way of atmospheric circulation, ocean currents, river input, and some migratory species.

Atmospheric Circulation

Although the atmosphere contains a small amount of contaminants compared to other sources, its rapid movement makes it an important pathway for transporting contaminants to the Arctic. The transport of contaminants from mid-latitudes to the Arctic can occur as quickly as from days to weeks.

Winds that carry contaminants to the Arctic are more frequent in the winter and spring than in the summer and fall. In the winter and spring months, the increased temperature difference between the Arctic and warmer mid-latitudes heightens the atmospheric pressure gradient and strengthens the strong westerly winds of the polar front. These strong westerly winds, reinforced by a high pressure system over Siberia that forms in the winter, push pollutants from mid-latitude North America, Europe, and Asia toward the Arctic. Additionally, contaminants such as sulfates and soot that can be broken down with the right amount of sunlight also accumulate in winter due to decreased sunlight. Similarly, particles like aerosols that are super small can remain in the atmosphere for 20-30 days in the winter due to the lack of precipitation that can ground them. In contrast, these same particles stay in the air for 2-5 days in the summer due to increased precipitation which plays a role in 'cleaning the air' and grounding the particles whether that's in the water, on the ice or on land. Particles like aerosols and soot are considered "one-hop contaminants" because they can travel long distances but once they are grounded they can't re-enter the atmosphere. This increase in atmospheric pollutant transport, along with decreased precipitation in the winter, causes pollutant build up in the Arctic atmosphere, also known as “Arctic Haze.”

Another important process that brings chemical pollutants to the Arctic is known as the “grasshopper effect”. This happens when volatile substances, like POPs and heavy metals, evaporate in the warmer mid-latitudes, and are carried north by prevailing atmospheric winds. These substances “hop”, meaning they can re-enter the atmosphere after landing on the ground, ice, or dissolving in a body of water. When they reach cooler temperatures, they condense and settle. This process continues until pollutants generated in mid-latitudes ultimately accumulate in the Arctic where once they condense into solid particles/aerosols or dissolve into the ocean, they are unlikely to convert back to a gaseous state.  

Terrestrial Input

Chemicals in terrestrial environments have two main fates, depending on whether they are soluble or insoluble in water. Pollutants that are water soluble dissolve into water and are carried to the ocean via snow melt, surface water, ground water, and rivers where they are distributed via ocean currents. Pollutants that are insoluble get absorbed into particles in soil or sediment, with which they can erode into waterways and possibly be transported to the ocean.

Rivers play a large role in long distance transport to the Arctic of pollutants that are generated in terrestrial environments in lower latitudes. Catchment areas of rivers accumulate contaminants from agricultural runoff such as pesticides/insecticides, municipal and industrial sewage, and inputs from mining, oil, and gas exploitation.

Peak flow of rivers into the Arctic occurs in June and July, coinciding with the greatest transport of river ice. This combination of high ice and water flow can cause jams, which lead to flooding of terrestrial areas. This is especially harmful in flat landscapes, like the Russian tundra, where flooding can cover vast areas. These kinds of floods typically leave contaminant-filled sediments on the flood surface. Although this removes contaminants from the river flow initially, sequential flooding can pick up previously deposited contaminants and contaminants that were previously not in the river pathway and transport them to the ocean.

What happens once the toxic substances reach the Arctic?

Due to the region's extremely cold temperatures and unique atmospheric and oceanic circulation patterns, the Arctic acts as a semi-isolated sink for chemical pollutants. Once pollutants travel northward and reach the Arctic, they become more stable and unlikely to decompose in the cold conditions. On top of this, they are unlikely to migrate back south.

Atmospheric Circulation in the Arctic

The polar vortex is a large low-pressure system that circulates air in the Arctic. This, along with the polar jet stream, a high-altitude fast-moving wind current that flows around the polar vortex, creates a barrier between the cold atmosphere of the Arctic and the air in the warmer lower latitudes. These circulation patterns that isolate the air in the Arctic, also trap chemical pollutants in the atmosphere.

Oceanic Circulation in the Arctic

The strong clockwise circulation of water and minimal efflux of surface water in the Arctic Ocean also traps chemical pollutants. The converging flow of water in the Beaufort gyre, the large downwelling gyre in the Arctic, traps pollutants accumulated in the water for years. These pollutants circulate in the Arctic, and are not dispersed. The only major outflows of water from the Arctic Ocean are from the Fram Strait or the Canadian Arctic Archipelagos. The large efflux of Arctic Bottom Water that flows out of the Arctic Ocean through the Fram Strait is well known for contributing to the formation of North Atlantic Deep Water and being a key component of global ocean circulation. However, chemical pollutants do not leave with this large efflux of water. This is mainly because the majority of water transport out of the Arctic is deep, dense water, and pollutants remain in surface layers that circulate the Arctic Ocean. Likewise, the flow of water to the North Atlantic through the Canadian Arctic Archipelagos and the East Greenland Current also transport mainly deep, dense water, while the pollutants remain primarily in the surface water trapped in sea ice or sediments.

Sea Ice Formation in the Arctic

Toxic pollutants in the air and ocean can get physically trapped in sea ice during formation. When ice forms from ocean water, contaminants like heavy metals and POPs that are bound to the water molecules become encapsulated in the ice structure. Chemical pollutants also deposit onto snow and ice through wet deposition (falling with precipitation) and dry deposition (settling from atmosphere). As toxic substances like POPs and heavy metal do not degrade, they can be trapped in ice for decades, or until they get released due to degradation of the ice itself. Seasonal melting, and melting caused by warming global temperatures, releases these pollutants into the ocean, where they can be redistributed into local ecosystems.

How does this problem impact marine ecosystems?

How toxic substances enter Arctic food webs

Bioconcentration:

Contaminants are directly acquired by plants and animals from sources like the air, water and soil.  “For example, many organic compounds dissolve well in lipids and will preferentially end up in the lipid components of the biota. Water-soluble contaminants can enter aquatic organisms through the gills or membranes in the gut.”

Bioaccumulation:

Includes bioconcentration as well as the intake of contaminants via food sources. The effects on the body will be determined by the concentration of the contaminants from the source and the organisms ability to get rid of these contaminants. Because of the mechanisms that some organisms have, there are contaminants that will be broken down and excreted and others that will accumulate.

Biomagnification:

Experienced by organisms if the contaminant in question cannot be broken down and excreted. Instead these contaminants get passed up the trophic levels. “Biomagnification is the major reason that persistent environmental contaminants reach high concentrations in top predators even when levels in air, soil, and water are low. The Arctic marine environment has long food chains compared with many ecosystems, making it especially vulnerable to biomagnification. The role of fat in the diet of many Arctic animals further promotes biomagnification of lipid-soluble organic contaminants.”

Adaptation of Arctic species that make them vulnerable to pollutants

Organisms in the Arctic face the challenges of seasonal food-shortage, extreme cold, and living in an ice-covered environment. In order to survive, they have evolved to have specific adaptations for this harsh environment. However, most of these adaptations listed below also make them highly vulnerable to chemical pollutants, especially POPs and heavy metals.

Energy Stored as Fat

Due to the low productive seasons that are present in the arctic arctic organisms have adaptations that allow them to produce and accumulate more fat than what would have been done in organisms at lower latitudes. This adaptation isnt without trade offs, many toxins are fat soluble which means they can accumulate in the fat of animals. In the winter when food is limited the fat that has been accumulated throughout the productive season is used but the contaminants that have been accumulating in these fat reserves remain in the body of the organism. The entrance of both nutrients and contaminants into bodies of water in the spring via runoff and ice melt allows for easy access to the food web.

Life History of Arctic species (k-selected)

Many of the species in the Arctic are K selected species meaning they have a slow growth rate, late maturation, and long lives. This is a great adaptation to have when recourses are limited but this increases the amount of time contaminants have to accumulate in these organisms. K selected lichen and mosses have an increases ability to acquire materials from the air as they depend on their above ground surface area to obtain nutrients rather than roots. This would be consequential to organisms that eat these types of plants as they contain more contaminants than other plants. Additionally, due to these longer life spans of animals in the arctic there are significantly more contaminants moving from one trophic level to the next.

Isolated regions of high species richness

Due to the lack of nutrients in the arctic organisms will accumulate where nutrients is “readily available”. For example there is “high phytoplankton productivity at the ice edge, which supports large populations of animals,” such as sea birds. Additionally sea mammals and birds will gather at large gaps within the pack ice. Having a large portion of the food web in close proximity allows for easy entry of contaminants into the food web.

Given the impact, what are the solutions?

·      What are the local solutions, if any?

·      What are the global solutions, if any?

In 1991 there was an introduction of the Arctic Environmental Protection Strategy (AEPS) which was adopted by the 8 circumpolar countries (Canada, Denmark/Greenland, Iceland, Norway, Sweden, the Soviet Union and the United States)

The objectives of this strategy include:

• protect arctic ecosystems and humans
• “Providing for the protection, enhancement, and restoration of environmental quality and sustainable utilization of natural resources, including their use by local populations and indigenous peoples in the Arctic”
• “Recognize and seek to accommodate the traditional and cultural needs, values and practices of indigenous peoples as determined by themselves, related to the protection of the Arctic environment”
• Consistently review the state of the Arctic environment
• Identify, reduce and eventually “eliminate pollution”

Five groups were created to implement the AEPS

• Arctic Monitoring and Assessment Programme (AMAP)
  • Monitor and assess the levels and impact of anthropogenic pollutants in the Arctic environment
  • Focuses on 3 pollutants (POP, heavy metals, and radioactivity)
  • “Also requested to monitor hydrocarbons to …better [document] oil pollution in the Arctic.”

• Conservation of Arctic Flora and Fauna (CAFF)
  • Exchange information and coordinate research on Arctic flora and fauna including habitats and species

• Emergency Prevention, Prepardness and Response (EPPR)
  • Create a plan as to how to cooperate in order to respond to threats of  “Arctic environmental emergencies”

• Protection of the Arctic Marine Environment (PAME)
  • Takes preventative measures in regards to marine pollution in the Arctic, no matter the origin of the pollution
• Sustainable Development and Utilization (SDU)
  • Proposes actionable items for governments to take to meet goals for “sustainable development of the Arctic, including the sustainable use of renewable resources by indigenous peoples.”

DDT and the Fight Against Malaria

• DDT, the most prominent POP that has been used as an insecticide since 1939, has been banned almost entirely around the world - with the exception of countries suffering from severe malaria outbreaks with limited access to healthcare and preventative medicine.
• Indoor Residual Spraying (IRS) is a method that has been used historically to repel mosquitoes by spraying DDT on interior surfaces as a chemical irritant.
• Female mosquitoes act as vectors of disease transport, most commonly known for the spread of the malaria parasite (most deadly of the parasites is P. falciparum), causing devastation in tropical and subtropical regions.
• African regions are most affected, accounting for 94% of global cases and 95% of global malaria deaths.
• India and China were the last two countries to continue manufacturing DDT for usage against malaria up until 2007, when China stopped DDT production. Now, India is the only country still producing DDT, and along with seven countries in Africa, is the only location still using it in any form.

The Stockholm Convention

The United Nations Environment Program (UNEP) manages the Stockholm Convention treaty that went into effect on May 17, 2004. This is a global treaty involving all 193 countries that are permanent representatives to both the United Nations (UN) and the UNEP - it was developed with the aim to reduce and limit POPs worldwide.

Since it was created, the Stockholm Convention formalized the global ban of DDT in agricultural use, but it has yet to completely eradicate DDT associated with fighting the spread of malaria (still used in India and Africa).

The treaty called for India to cease production of DDT by 2024, but the deadline was not met and the deadline to comply was extended by five years.

In order to prevent more damage to the Arctic ecosystem,

Alternatives to DDT Usage Against Spread of Malaria

• Modern medicine has developed vaccines and methods to prevent the spread of malaria, without the environmental damage and harm to human/wildlife health that DDT causes.

• WHO recommends implementation of the RTS,S/AS01 (Mosquirix) and R21/Matrix-M malaria vaccines in children under two years of age in areas where the spread of malaria is rampant.

Alternatives to Pesticide Usage in Agriculture

Neem Tree (Azadirachta indica) based Products as Biopesticides

• Azadirachtin is a chemical extract from the plant that interrupts normal insect reproductive processes, feeding habits, and normal development.
• One hesitation from this biopesticide is that Azadirachtin-A shows evidence of immediate degradation when exposed to sunlight, so future research needs to find solutions/further explore this setback. Since sunlight is a fundamental component of agriculture, it is crucial that the pesticide can withstand it.
• However, the benefits of implementing neem based pesticides would be extensive since they are non toxic and will not harm the Arctic.

Bacillus thuringiensis as a Microbial Biopesticide

• The bacteria can be used to develop genetically modified crops (Bt-GM crops) which have intense insecticidal properties but do not harm human health or damage the environment in the way traditional pesticides do.
• One hesitation that needs more research before this can be implemented as a solution is the idea that genetically modified plants may lead to antibody-resistant diseases. Therefore, this solution to limit pesticide pollution in the Arctic requires future research.
• Other than the harm reduction, another benefit from this biopesticide is that it is much more cost effective and is produced continuously for a much longer amount of time.

Bioindicators to Monitor Progress

In combination with preventative and restorative efforts, establishing monitoring systems for the Arctic can help ensure solutions are delivered in an efficient manner.

• Fish and invertebrates
  • These species are widely exposed to POPs through sediments, water, and diet, making them helpful in identifying all around pollution levels in the Arctic environment.
  • As primary consumers, these species are consumed by and will have their own pollution concentrations transferred onto the majority of the remaining species of higher trophic levels. This includes humans (especially Inuit populations). This is another reason why they are good bioindicators.
• Ringed Seals and Polar Bears
  • The especially harmful POPs known as organohalogen contaminants (OHCs) affect Ringed Seals and Polar Bears to an extreme degree.