Persistent Pollution – Past, Present and Future

Persistent pollutants remain in the environment for a long time. This obvious statement makes historical analysis important. Such analysis can be useful at times for even very practical issues such as the record of the activity at old industrial sites, which are planned for redevelopment. Because the atmosphere has a relatively rapid turnover, persistent materials are frequently found as deposits on the earth’s surface. This means there is a transition in the way we approach air pollution in comparison to earlier concerns over the pollutants smoke and sulphur dioxide from coal burning. These have relatively short lives in the atmosphere. There are long-lived pollutants such as nitrous oxide or carbonyl sulphide from aluminium production, that account for an increasing interest in such pollutants and their potential impact on the stratosphere. The best known example of persistence among the long-lived gases is the issue of CFCs and their relation to the widespread concern over the impacts they have on global climate and stratospheric ozone depletion.

As part of the workshop the students were presented with an exercise concerned with estimating the concentration and deposition of air pollutants around the salt works of Lüneburg during the sixteenth century.

In this chapter, we give an overview of some of the most interesting results which have been obtained by studying the changing occurrence of heavy metals in Antarctic and Greenland snow and ice cores. After recalling the pioneering role of Clair Patterson in this field, we describe first briefly the conditions which must be fulfilled to obtain fully reliable data, especially regarding the cleanliness of the samples and the use of specially designed clean laboratories. We present then some of the most interesting data which have been obtained on man induced changes during the past millennia/centuries. They show clear evidence of a global pollution of the atmosphere of our planet for heavy metals, which can be detected even in the most remote areas of the Southern Hemisphere and can be traced back to Roman times in the Northern Hemisphere. Finally, we present some recent data on past natural changes in heavy metals in ice dated back to 670 kyr BP, with pronounced variations during the successive interglacial/glacial climatic cycles.

Persistent Organic Pollutants (POPs) are chemicals that are recognized as persistent, bio-accumulative, toxic and susceptible to long-range atmospheric transport (PBT-LRT). POPs generally fall into two classes dependent on their origin; intentionally produced chemicals (typically organo-chlorinated pesticides and industrial chemicals, such as hexachlorobenzene – HCB) and unwanted by-products of combustion (such as, polycyclic aromatic hydrocarbons – PAHs, and dioxins – PCDD/Fs).

For the foreseeable future, the atmosphere and the environment in general will remain to serve as a dump for various anthropogenic substances. Some substances will have negative properties so that society will sooner or later begin regulating their emissions. To that end, science must provide society with the tools for the retrospective evaluation of the physical and economical impacts of past regulations, and for the predictive evaluation of alternative scenarios of future regulations.

Heavy metals and trace elements are ubiquitous throughout the environment, some are essential for life (e.g., Fe), others are micronutrients (e.g., Se) and others are considered as toxic elements (e.g., Hg). Levels of these elements in the environment are determined by the local geochemistry and anthropogenic emissions, with implications for human and environmental health. Records from Alpine ice cores have demonstrated to be among the best tools in paleoenvironmental studies to reconstruct past emissions of heavy metals and persistent organic pollutants. From the comparison of trace element records in the snow and ice with the emission inventories compiled in recent years it is also possible to reconstruct the past trends in the emission of these compounds. We present here some trace elements records from the European Alps and in particular from the Mont Blanc and Monte Rosa regions. The study of levels of these elements in alpine regions allows us to begin to understand their biogeochemistry and their effects on a global and regional scale. However, without advances in clean working techniques and the outstanding improvement in instrument sensitivity that have occurred over the last two decades, none of these studies would have been possible.

Industrial, agricultural and other anthropogenic activities have lead to the introduction of thousands of pollutants, most of them synthetic organic compounds to the marine environment (Dachs and Méjanelle 2010). A fraction of these organic compounds, called persistent organic pollutants (POPs), are chemicals that have become a major concern because of their toxicity, persistence, bioaccumulation tendency, and susceptibility to undergo long-range atmospheric transport. Traditionally, much attention have been given to a few families of POPs, such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) such as DDT and hexachlorobenzene (HCB) and other byproducts of industrial processes or combustion such as dioxins and furans (PCDD/Fs) and polynuclear aromatic hydrocarbons (PAHs). However, these chemicals are a small fraction of the total known pollutants in the marine environment (Dachs and Méjanelle 2010) and presumably of the total potential pollutants occurring in the environment (Muir and Howard 2006). In any case, these few families of POPs have been detected everywhere on earth in abiotic and biotic matrices (Gioia et al. 2006, 2008a; Gilman et al. 1997; Jaward et al. 2004). Today, compounds with similar or different physical chemical properties (such as the polybrominated diphenyl ethers, PBDE and other fluorinated compounds, PFs) are being manufactured and widely used, potentially entering the environment and providing new challenges for the maintenance of its quality. Our current knowledge indicates that the cycling of these chemicals in the environment is highly complex; indeed their local, regional and global cycle is controlled by repeated air-surface exchange and interactions with the carbon cycle, especially the organic and soot carbon fractions. Because, a fraction of these chemicals are hydrophobic, they have the potential to accumulate in all the trophic levels of ecosystems, including those far away from sources. The number of known organic pollutants in marine waters, and other environmental compartments, has increased dramatically during the last decade, in part due to important analytical developments. Nowadays, even though much of our knowledge on organic pollutants is centered on a few chemical families (PCBs, HCHs, DDT, PAHs, etc.), these families should be viewed as markers or “surrogates” of other pollutants in marine waters with similar physical–chemical properties. In addition, other chemicals with different physical–chemical properties (i.e., greater water solubility, low volatility) may reach coastal and open oceans via rivers and undergo different environmental behavior, due to their ionic character. In fact, some of newly emerging compounds have been suggested to behave as passive tracers in waters (Yamashita et al. 2008), a behavior quite different from that shown by legacy POPs such as PCBs or HCHs.

The discovery of the insecticidal properties of DDT by Paul Müller (Läuger et al. 1944; DDT was synthesized more than 50 years ago (Zeidler 1874) can be deemed as one of the starting points of intensive search of organic compounds to be used as pesticides. These organic compounds were – and are – used and applied deliberately especially in the environment due to their properties as poisons against plants, fungi or insects. However, already in the beginning of the 1950s of the last century the persistence (i.e., high lifetime) of these compounds in the environment was realized and culminated 1962 in the publication of ‘Silent Spring’ by Carson (2000; Marco et al. 1987). Besides these highly chlorinated pesticides of the first generation, high amounts of chemically bad characterized mixtures such as polychlorinated biphenyls (PCB) were often used. Although these substances and further byproducts, such as chlorinated dibenzodioxins and dibenzofurans (as far as we know never used commercially), are from a chemical point of view not a homogenous group, besides other general properties, they are man-made and known to be at least persistent in the environment. As a consequence, these organic compounds were termed Persistent Organic Pollutants (POP).

Volatile organic compounds (VOCs) are normally present in the vapor phase at room temperature (vapor pressure greater than 0.1 mmHg [0.0133 kPa] at 25°C). Compounds less volatile are known as semi-volatile organic compounds (SVOCs). SVOCs may be present in the atmosphere in the vapor phase, but are more normally associated with aerosol, either as dusts or liquid droplets (Lodge 1991; Kouimtzis and Samara 1995; Harper 2000). There is growing concern over the VOCs/SVOCs present in the atmosphere. Some of them play a major role in defining atmospheric chemistry and processes. Several short chain hydrocarbons affect the formation of ozone and other photochemical oxidants. Other VOCs/SVOCs play a role in stratospheric ozone depletion, tropospheric photochemical ozone formation and enhancement of the “greenhouse effect.” Further, many of VOCs/SVOCs are known for their carcinogenic and mutagenic properties (Ravindra et al. 2001, 2008a). The World Health Organization has estimated that urban air pollution contributes each year to approximately 800,000 death and 4.6 million lost life-years worldwide (World Health Organization 2002). These consequences require a priority to identify and chemically characterize the atmospheric pollutants and especially those attached to the fine and ultra fine fraction of airborne particles (Ravindra et al. 2008b). This will help us to understand their possible implications for human health and also their environmental distribution and fate.

Per- and polyfluorinated compounds (PFCs) comprise a large group of chemicals, consisting of a hydrophobic alkyl chain and usually possessing a hydrophilic functional group. The alkyl chain is partly or fully fluorinated and typically contains between 4 and 18 carbon atoms (De Voogt and Saez 2006). Therefore, PFCs are both oleophobic and hydrophobic and form strong surfactants. PFCs comprise ionic compounds like perfluoroalkyl sulfonates (including perfluorooctane sulfonate, PFOS) and perfluoroalkyl carboxylates (PFCAs including perfluorooctanoate, PFOA, Table 11.1) as well as neutral, volatile PFCs like fluorotelomer alcohols (FTOHs), N-alkylated fluorooctane sulfonamides (FOSAs) and sulfonamidoethanols (FOSEs, Table 11.2).

A model in the here discussed form is first of all a description of complex processes in nature. This starts with a description by words or graphics (conceptual model) and goes up to complex mathematical or numerical simulation models that run on supercomputers. The complexity of a model is determined by several factors. It can be simply limited by computational resources which involves the questions if enough computer power or storage media for the data output is available or if there are appropriate tools available to make sure the data can be evaluated in a reasonable way. Developing a model can be seen as an interactive and iterative process. You can use a model to reproduce and understand experimental findings whereas at the same time experimental results are used to refine models. The most important point to consider before you build or acquire a model is the purpose the model should serve. Conceptual models e.g., could be used to describe physical or chemical processes in the atmosphere be it in lectures or for scientific discussions of processes. Mathematical models allow a more profound investigation of physical and chemical processes. Ultimately, models that are used to simulate the dispersion of substances over e.g., the European continent or to predict ambient air concentrations and deposition rates in a high spatial and temporal resolution can be very comprehensive. They often require a lot of input variables (e.g., meteorology, emissions) and parameters (e.g., physical–chemical constants). Insufficient knowledge of these inputs may lead to erroneous results or misleading interpretation of the results. The repertory of numerical simulation models ranges from simple box models that can e.g., represent a closed system and contain only one substance in one compartment and thus require little computer power to elaborate three-dimensional grid models containing plenty of substances involved in a number of physical and chemical processes. A scientist who develops or applies a model has to balance the complexity and expense of the model with the available input variables and parameters, the available computational resources and the demanded precision of the model results (Jacobson 2005).

Data assimilation and Inverse Modelling may serve various purposes by use of manifold techniques. A reasonable definition reads as follows: extracts the signal from noisy observations (filtering) interpolates in space and time (interpolation) and reconstructs state variables that are not sampled by the observation network (completeness).

Aerosol particles belong to the most important constituents of the Earth’s atmosphere. Cloud formation and cloud properties strongly depend on the amount and the type of atmospheric aerosol particles. By scattering and absorbing solar radiation they have a large impact on the global radiation budget and locally on the visibility. Finally, they consist of various chemical compounds including harmful or even toxic substances. The atmospheric lifetime of aerosols strongly depends on meteorological conditions. On the one hand, they are efficiently washed out during rain events. On the other hand they accumulate in the atmosphere under dry conditions and they can be transported over long distances, particularly if they have been mixed into higher altitudes before. Furthermore persistent pollutants like lead and other heavy metals, polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are often bound to these particles and are transported with them. Their regional distribution and deposition can only be understood together with the knowledge about atmospheric aerosol particles.

The radiation budget of planet Earth, given the solar irradiance at the top of the atmosphere, is to a large extent determined by minor constituents of the atmosphere. Less than three thousandths of its mass – including water vapour, cloud water and cloud ice – regulate how much solar radiation reaches the surface and from where in the atmosphere or on the surface the same amount of energy as absorbed globally from solar irradiance is radiated back to space in the thermal infrared. The least understood part of the Earth’s radiation budget and its changes is related to an extremely small fraction of the minor constituents, the aerosol particles, liquid or solid particles suspended in air in the size range from about a nanometer to a few micrometers. At a typical mass mixing ratio of 10 μg/m³ in the free troposphere aerosol particles constitute only about 10⁻¹⁰ of the mass or 10⁻¹³ of the volume fraction of tropospheric air.

Clouds are ubiquitous in the Earth’s atmosphere. They are important for a multitude of reasons. By intervening with the radiation and energy budget of our planet clouds play a major role in climate and global change (Kiehl and Trenberth 1997; Quante 2004). Furthermore, they possess a key role in the global and regional water cycles (Quante and Matthias 2006). Besides these prominent influences on weather, climate and water availability, clouds are involved in several ways in the distribution and transformation of pollutants in the atmosphere. That clouds play an active role in the processing and cycling of atmospheric substances has long been recognized.

The marine environment covers more than 70% of the earth surface and is one of the richest biospheres of the world. Biological and chemical investigations of marine ecosystems have provided insights into a fascinating and complex world underwater. The biological and chemical diversity is very high due to the array of natural conditions. It encompasses a high thermal range from −1.5°C to 350°C and a pressure range of 1–1,000 atm. The food conditions vary between nutrient rich and nutritionally sparse regions and photic and non-photic zones. Marine organisms have to adapt to these wide variety of living conditions. The adaptation capabilities are different from those of land-based organisms (Lindequist and Schweder 2001). Marine organisms live in close associations and therefore in nutrition and substrate competition (Ianora et al. 2006). In order to ensure survival and fitness it is necessary to produce secondary metabolites. The variety of secondary metabolites provides a biochemical reflection of the biotic interactions. The function of secondary metabolites is manifold. Allelochemicals are used for intra- and interspecies signaling and communication, for the deterrence of predators and herbivores or the suppression of competing neighbors. Bacterial and fungal invasion can be inhibited. Secondary metabolites can also be used for protection against UV radiation.

This contribution is intended to give an impression of various aspects of the effects of persistent pollutants on marine mammals with a special emphasis on the challenges and methods to confirm cause–effect relationships and biomarker reactions as well as to monitor contaminant levels and biological effects of persistent pollutants in marine mammals. The intention is not to present a comprehensive review with complete citation, but to establish an understanding of the context. Illustrating examples are primarily chosen from research and studies on seal species from the North and Baltic Sea.

At present, more than 18 million organic compounds are known. Consequently, even if only a small portion of these substances exhibit properties leading to environmental problems, the number of organic contaminants is high and, in principle seams unlimited, as the development of new substances continues. Approximately 2,000 substances are presently estimated to be environmentally relevant, of which 100–300 compounds are summarised in lists of substances to be treated with priority by various international organisations, such as the EU (EU-Water Framework Directive: EU-WFD), OSPAR Commission (for the protection of the Marine Environment of the North-East Atlantic, (OSPAR 2005, 2009) and HELCOM Commission (Baltic Marine Environment Protection Commission).

Emerging organic contaminants (EOCs) include several groups of organic compounds that have been wildly distributed in the environment and attracted tremendous attention over the past decades. Analyses of EOCs in water have been reviewed in several special issues of Analytical Chemistry (Richardson and Ternes 2005; Richardson 2007). These important articles highlighted the current issues in the developments of instrumental technologies related to the detection of EOCs. In another important issue, Environmental Science and Technology published an excellent perspective in “what is emerging?” (Muir et al. 2006). This article pointed out that the longevity of a contaminant’s emerging status is typically determined by whether the contaminants are persistent or have potentially harmful human or ecological effects. The EOCs discussed in this paper are selected on the basis of the reviews made for emerging contaminants in water analysis (Richardson and Ternes 2005; Richardson 2007) and review for potential candidates of persistent organic pollutants (Muir et al. 2006). The EOCs include polyfluorinated alkyl substances (PFASs), (perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS) and others), brominated flame retardants (BFRs) and their degradation products, polybrominated dibenzo-p-dioxins (PBDDs), and polybrominated dibenzofurans (PBDFs), synthetic musk fragrances, organophosphate esters, alkylphenols (APs) and bisphenol A (BPA). The acronyms of individual compounds are listed in Table 20.1.