Abstract
This essay deals with the inter-relationship between two aspects of the earths sulphur cycle and its affect on the biosphere environment/ecosystem, in particular the phenomena of acidic precipitation and the leaching of important nutrients and chemicals from the extractive mining industries.
Introduction
The biosphere is one of the main components of the Earth system and is directly involved in almost all the processes that occur on the shallow surface of the Earth. It is inherently linked to the other three sub-systems, the geosphere (upon which the biosphere “sits”), the atmosphere (beneath which the biosphere rests) and the hydrosphere (to which the biosphere abuts or is surrounded).
The biosphere supports all known living organisms and is therefore the most familiar, important and life-critical component of the Earth system upon which humans depend. And yet this critical interdependency is often not considered by many of the actions and processes of human development in the modern age.
The human impact on the biosphere occurs in all regions of the globe, is caused by every society in a host of minute or dramatic and significant ways. These impacts can cut across all levels and classes of society. The two examples outlined here of human impacts on the biosphere, amply demonstrate the fragile state of equilibrium within the ecosystems of the biosphere and just how inter-connected the web of relationships can be. These relationships, known as flows or cycles, relate to the transfer of energy or materials within the Earth system.
On a global scale, the energy and biogeochemical cycles are “closed” because heat that escapes from the earths atmosphere is replenished by the suns energy, and materials are transferred from one store or reservoir in the spheres during biogeochemical cycles, but the material itself does not escape the Earth into space, it “flows” from one system into another. This transfer from one cycle and/or system is a key concept when we consider the harmful effects of human activities within the biosphere, in particular the sulphur cycle.
Acid rain and human activity
The sulphur cycle occurs naturally within the biosphere environment and over the millennia has suffered singular, sharp shocks to its state of equilibrium in the form of volcanic eruptions. Other natural processes such as marine phytoplankton or terrestrial bacteria contribute to the slow release of sulphurous compounds. These compounds are converted in the atmosphere and return to the earths surface in the form of precipitation with a highly acidic content. This wet deposition is commonly referred to as “acid rain” and it was first identified in around 1872 in Sweden by Robert Angus Smith and reported further by Oden (1967) in a Swedish newspaper article on acidification of lakes in Sweden which was linked to pollution from the United Kingdom and central Europe. The same chemical compounds can also be dry-deposited as particulates and gases falling to the ground.
The far reaching implications of acidic precipitation continue to affect a number of wilderness ecosystems such as forests, streams and lakes and also man-made environments such as agricultural crops and plants, field systems and nature reserves, fisheries and man-made structures, buildings and objects.
By describing it as acid rain, we should be mindful that the normal value of rain is already 5.6 on the pH scale and considered acidic because of residual chemical interactions in the atmosphere. Any pH level of 0 to 7 is determined acidic; 7 is neutral pH; and a level above 7 is defined as alkaline. A lower pH number equates to increasing acidity levels.
The ecological effects of acid rain are seen in aquatic environments where it is harmful to fish and other wildlife : at pH 5 many fish cannot hatch eggs ; frogs and their food sources will die in water of pH 4. Acid rain in forest ecosystems weakens trees and bushes by damaging their leaves, leaching the nutrients in the soil around their root systems denying them the nutrients necessary for growth and survival. In some cases, it can result in poisoning by chemical reactions that release toxic substances in the soil. Toxic substances also wash away in the runoff towards streams, rivers, and lakes. Food crops and fields in developed countries are not usually affected as obviously because farmers add fertilizers to the soil and so this replaces any nutrients washed away by acid rain processes.
The effects of acid rain can be dramatically significant. An extreme case of the harmful effects of SO2 on organic areas was caused by a natural process, the sulphur dioxide (SO2) emissions from the Kīlauea volcano in Hawai. Eruptions lead regularly to high concentrations of sulfur dioxide being carried by prominent trade winds to created a volcanic “smog” which was, and still is, subsequently precipitated as acid rain downwind into the Kau Desert region. The pH of surface material is measured at <4.0 there and accounts for the fact that no vegetation now exists in this area, yet the opposite side of the volcano remains lush and green.
The effects of human derived SO2 emission maybe less obvious, but nonetheless are still a significant influence on ecosystem operations. Our industrial processes are a constant producer of sulphurous compounds into the atmosphere and power generation using fossil fuels in particular is a major factor in the release of SO2 to the environment. Menz and Seip (2004) stated in their paper on regulation measures for control of SO2 production that “regions that have been most affected by acidic deposition include Europe, eastern North America, and Southeast Asia, especially central and southern China (Kuylenstierna et al., 2001). Sulphur emissions have played the dominant role in acidic deposition in these regions.”
It is therefore no surprise to see the correlation of cause and effect between industrialised countries and the areas of deposition. The fact that the site of production can be thousands of miles from the location of deposition has often caused tensions between different countries governments over issues of responsibility and remedy of damage, as in the case of Sweden and Norway from 1960s through to 1980s, and Canada and USA in the 1980s.
Management options to alleviate or reduce the human activity that causes acid rain tends to fall into prevention (processes at the beginning of the cycle), mitigation (attempts to reduce the impact) and repair (ways to undo the damage caused).
One method of prevention is through the political and legislatory management of SO2 polluting processes. This has gone through a number of stages to reach its present day status and not all efforts have been truly effective. In 1985 in Helsinki, the Sulphur Protocol was signed by twenty one countries in an effort to reduce their emissions by 30% from 1980 to 1994. It was well intentioned but in practice none of the twenty one “planned to use the instrument as a guide to sulphur reductions.” (Levy, 1995).
In 1994, the Sulphur Protocol was revised to account for a critical-loads system of measurement, defined as ‘the highest load that will not cause chemical changes leading to long-term harmful effects on the most sensitive ecological ecosystems’ in a designated area. This led to creation of a map with a sliding scale of reductions per country.
Yet this system of international political agreement, which filters through to Government regulation and industrial policy is not without its issues. From the moment of signature, politicians would battle to reduce their countries commitments and percentages of reductions. Lines were drawn and the United Kingdom, France, Belgium, Denmark, Spain and Ireland, who sought lower reduction targets, argued against the likes of Norway, Finland, Sweden, Germany, the Netherlands, Switzerland and Austria on the revised targets.
Once adopted, the measures to reduce the emissions would see legislation passed that would outlaw certain processes and businesses. Industry would be forced to find new ways to produce their goods and services without production and release of SO2. The automobile industry in particular would have to start the switch over from sulphur-rich fuels towards less pollutant versions. They would begin to increase research and development on alternative energies and fuels. The government would implement a closing down of coal fired energy plants and seek to increase solar, wind and nuclear energy programmes.
In the USA, a mitigation process of management was created by the amendment in 1990 to the Clean Air Act, Title IV-A – Acid Deposition Control, that outlined the Governments regulations to offer industries pollution control choices. This offered measures such as using low-sulphur coal and fitting of devices that would negate, dissipate or convert an amount of harmful emissions. It also closed down some failing and older power plants and factories to remove the dangerous chemicals from the production chain.
In both the above scenarios (international and national legislation) introduction of cost sharing schemes, new technology, permits and quotas for authorized production and release of SO2 are often considered on a cost-benefit analysis method, both by the individual businesses and by the political organisations. It is unfortunate that the financial aspects still heavily outweigh the environmental arguments whe looking for solutions. The pressure point is in finding the “acceptable” cost-benefit balance for producers when considering elimination, reduction or alleviation of SO2 human impacts.
As a repair and counter measure in Scandinavia for areas where acid rain has affected the trees and water courses, the liming of water bodies is carried out on a large scale. Every year in Sweden around 7500 lakes and 11,000 kilometres of waterways are treated to balance the acidity of the water and its surrounding intake. It is an expensive method and has to be done repeatedly to maintain its effectiveness. However, sometimes the lime that is distributed in the wetlands catchment area can result in damage to plants, killing off bog moss, yet the benefits are generally considered to outweigh the harm. This is an example of the complex inter-connection of the biosphere. What is carried out in one area with a specific objective can also negatively affect a system which borders on or is in a close relationship with that area.
Mineral extraction and human activity
Man is a voracious consumer of natural minerals from the biosphere and the extractive mining processes are a significant concern to environmentalists worldwide. As well as the obvious displacement of animals and destruction of plant and ground cover in the open pit mining methods, the by-products of the mine are a biosphere hazard.
Where material is excavated from an open pit, this is one of the most common forms of mining for strategic minerals. Open pit mining is extremely damaging to the environment as the desired minerals are usually only available in a small percentage, which therefore increases the amount of ore needed to be processed. Metallic ore is buried under layers of ordinary soil or rock (known as the overburden) that must be moved to allow access to the ore deposits. For most mining operations the overburden is an enormous quantity of material, often containing significant amounts of toxic substances. It is usually deposited on-site, left in piles on the surface (tailings) or as backfill in open pits.
The tailings and rock waste from mining, when left open to the elements further induces a leaching effect of chemical compounds and heavy metals. In combination with precipitation that is already affected by higher levels of SO2 from human industrial processes, this makes for an accelerated solution and process, leaching rapidly into watercourses and transporting them as dissolved species or granular sediments.
Modern mining techniques use significant amounts of water for extraction, processing, and its waste disposal processes. Wastewater from mining can pollute water sources nearby and deplete freshwater supplies in the regions surrounding the mine locations.
The chemical laden water may then seep into the underground water aquifers thereby contaminating water drawn from wells or merely rest in the sediment until floods or further activities dislodge them. Wells located near mining sites have been reported to contain heavy metals at levels that exceed drinking water criteria (Garbarino et al., 1995; Peplow, 1999).
Conclusion
Considering the image of a spiders web, it is perfect to describe the connected relationships within the sulphur cycle and biosphere. A small tug on one side of the web affects what happens in all other areas and directions of the web. The effect is felt more significantly when close to the tug point, yet less so the further away it is on the web.
When a factory produces every week an airborne contribution of SO2 that drifts and falls to the ground as acid rain, without doubt this constant deposition changes the biosphere in some way. The plant life is affected, the run off leaches to the water course, and it can remove aluminium from the soil as part of the chemical reaction. In a small and natural “dose” of acid rain, the environmental system can bounce back from the shock ; in a prolonged, repetitive and larger dosage, then attrition takes hold and degrades the system past its equilibrium point.
The same web analogy can apply to the complexity of human management procedures and processes which are in place to combat the pollution of the biosphere by mans activities. An initiative of one Government to prevent, mitigate or repair their actions in SO2 pollution may affect the activities of another and in ways that may not be forseen by the committee of persons involved in the initiative. There is no “one size fits all” solution to the problem as was seen by the original Sulphur Protocol cap of 30% reduction. The Clean Air Act amendment in 1990 did not suit all businesses and the continued liming of Scandinavia water courses is an action which is clearly unsustainable in the longer term.
The conclusion is that a combination of small, medium and large scale efforts across the globe are necessary to ensure that elements of the biosphere are protected from human development impacts. The scale is larger than one organization and body as a single “caretaker” role. Increasing education and media to highlight the individual responsibilities towards care of the biosphere in local environments is necessary. It is hoped that this may change thought processes and procedures at international, national, local, business and personal levels.