Mountain Waters as Witnesses of Global Pollution

Abstract

Mountains lakes, streams, and rivers, collectively known as headwaters, are popularly seen as waters of the highest quality. However, human-related pollution has reached remote areas of the planet everywhere through atmospheric transportation. Mountain freshwater ecosystems are extreme environments for life and thus are particularly sensitive to some new stressors. This chapter begins by summarizing the main features of mountain freshwater ecosystems and then comments on the effects they have historically suffered. It focuses particularly on two environmental problems: (1) acidification and (2) contamination with persistent organic pollutants. These problems are at different stages of development and knowledge. Acidification mechanisms are well understood, and mitigation actions have been applied successfully. The pace of recovery and interaction with climate change are now focusing research interests. In contrast, the environmental problem of persistent organic pollutants in mountain waters has been unveiled only recently. Some initially unexpected findings, such as the increasing concentration of some pollutants with altitude, have stirred further investigations on bioaccumulation processes, which are summarized here.

Actions against contamination of sites far from the pollution sources, such as mountains, require the development of international protocols. The fight against acidification constitutes a successful example of such actions, and efforts against other atmospheric pollutants are following suit. These large-scale actions require adequate long-term monitoring networks, models for interpretating the results, and sound understanding of the mechanisms that underlie the observed patterns. Research may focus on: (1) increasing understanding of biotransformation of organic pollutants in natural conditions; (2) better evaluation of toxicological effects on both organisms and ecosystems as a whole; and (3) the ways that climate change influences the transport, accumulation, and toxicity of pollutants, a subject that cuts across all freshwater quality issues.

Glossary

Acidification

Ongoing decrease in the pH of soil and freshwater caused by acid rain.

Acid–base Balance

Equilibrium between acids and alkalis in a body of water.

Aerosols

Suspension of particles dispersed in air.

ANC (acid-neutralizing capacity)

Measures the buffering capacity against acidification in water. It is defined as the difference between cations of strong bases and anions of strong acids. ANC is often used in models to estimate acidification levels from acid rain pollution and as a basis for calculating critical loads for soils and freshwaters.

Bioaccumulation

Accumulation of some toxic substance in an organism’s body.

Biodiversity

General concept for the diversity of life. It is commonly used in a more restrictive way as numbers of different species of plants and animals in a habitat.

Biomagnification

Bioaccumulation of a toxic substance obtained via food intake.

Biotransformation Capacity

Ability of an organism to transform a toxic substance.

Cation and Anion

Ions with a positive or negative charge, respectively.

Critical Load

Quantitative estimate of exposure to one or more pollutants below which level significant harmful effects on specified sensitive elements of the ecosystems do not occur (according to our present knowledge).

Desorption

Release of an adsorbed substance from a surface to a gaseous or solution state.

Detritus

Debris of organic matter produced by erosion or decomposition.

Ecosystem

Biological community of interacting organisms and their environment.

Enzyme

Protein that accelerates a chemical reaction and remains unchanged by the process.

Exocrine Pancreatic Cancer

Disease in which malignant cells (cancer) form in the exocrine tissues of the pancreas, which produce digestive juice—in contrast to endocrine tissues, which produce hormones.

Eutrophication: Nutrient

enrichment, which eventually leads to dense populations of phytoplankton (microscopic algae) in aquatic systems.

Greenhouse Gases

Any of several gases that cause global warming.

Halogens

Any of several electronegative elements that form a salt when combined with metals.

Hydrophobic

Lacking attraction for water.

Hydrophilic

Having affinity for water.

Intrauterine Exposure

Fetal exposure to pollutants that occurs during intrauterine development because the mother has been contaminated.

Lipid Content

Amount of fats in a tissue or body.

Lipophilic

Having an affinity for lipids, usually in contrast to hydrophilic.

Littoral Biota

Organisms living close to the shores of lakes or seas, in contrast to those living in open waters.

μEq∙L⁻¹

Microequivalents per liter. In chemistry, an equivalent is the mass of a particular substance that can combine with or displace another substance in a reaction. It is used when expressing combining powers of elements and compounds.

Metabolic Rate

Amount of energy expended during a given period by chemical reactions that occur in living organisms to maintain life.

Methylation (demethylation)

Replacement of hydrogen atoms with a methyl group (or vice versa).

Natural Radionuclide

Naturally occurring atom with an unstable nucleus that undergoes radioactive decay.

Oligotrophic Waters

Aquatic ecosystems poor in nutrients and as a consequence having limited productivity.

Oncogene Mutation

Change in a gene that may result in the onset of cancer.

Organic Pollutants

Organic compound that contaminates the environment.

Organohalogen Compounds

Chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (chlorine, bromine, fluorine, or iodine).

pg∙L⁻¹

Picograms per liter: one-trillionth of a gram dissolved in a liter.

pH

Level of acidity evaluated as the concentration of hydrogen ions in a solution.

POPs (persistent organic pollutants)

Man-made organic compounds that persist in the environment because they are resistant to degradation through chemical, biological, and photolytic processes. They are capable of long-range transport, bioaccumulate in organisms, biomagnify in food webs, and have a potentially significant impact on human health and the environment. Many POPs are pesticides, but others are used in industrial processes and in the production of a range of goods.

Photo-Oxidative Degradation

Breaking down of a substance in the presence of oxygen or ozone, facilitated by radiant energy such as ultraviolet (UV).

Precipitation Chemistry

Changes that occur during formation of a solid in a solution or inside another solid during a chemical reaction, or by diffusion in a solid.

Reactive Gases

Gases that include surface ozone (O₃), carbon monoxide (CO), volatile organic compounds (VOCs), oxidized nitrogen compounds (NO_x, NO_y) and sulfur dioxide (SO₂). All of these compounds play a major role in the chemistry of the atmosphere and so are heavily involved in interrelations between atmospheric chemistry and climate either through control of ozone and the oxidizing capacity of the atmosphere or through the formation of aerosols.

Sedimentation

Tendency for particles in suspension to settle out of water and rest against a barrier (rock, sediment, plants).

Semi-Volatile

compound: Shows an intermediate tendency to evaporate.

Stenotherms

Organisms that do not tolerate large fluctuations in temperature. Cold-stenotherms require cold environments and do not survive with even relatively low warming.

Stratospheric Ozone

Ozone (O₃) located mainly in the lower portion of the stratosphere from approximately 13–20 km above Earth, although the thickness varies seasonally and geographically.

Thermodynamic Equilibrium

State when a system is in thermal equilibrium, mechanical equilibrium, radiative equilibrium, and chemical equilibrium. There are no unbalanced potentials, so the system does not experience changes if isolated from its surroundings.

Toxicological Susceptibility

Vulnerability to poisons.

Tropho-Dynamics

Dynamic aspects related to trophic relations in the ecosystems.

Troposphere

Lowest part of the Earth’s atmosphere. Most weather changes occur here, and temperature generally decreases rapidly with altitude.

UV Radiation

Electromagnetic radiation with a wavelength shorter than that of visible light (in the range 10–400 nm).

Visigothic Period

The Visigoths were one of two main branches of Goths, an East Germanic tribe that disturbed the late Roman Empire. Here, the Visigothic period refers to the centuries immediately after the Roman Empire.

Volatilization (revolatilization)

Process whereby a dissolved compound is vaporized.

Wet (dry) Deposition

Process by which aerosol particles collect on solid surfaces, decreasing their concentration in the air. It can be divided into wet deposition (particles are scavenged by rain or snow) and dry deposition (particles settle under dry conditions).