Pollution

Causes, Effects and Control

R M Harrison, R M Harrison

• Éditeur: Royal Society of Chemistry
• Année: 2015
• ISBN:
  9781782625605
• Édition: 5
• Sujet: Scienze biologiche
• Sous-sujet: Scienze ambientali

Twenty years on from the first edition of Pollution and the topic remains high in the public awareness. Environmental pollution is now a major area of research, consultancy and technological development and is a priority for the political agendas of both the developed and developing worlds.

The fifth edition of this book is fully updated, and includes an entirely new chapter on Climate Change, presenting an authoritative view on this topic. Chapters in fast moving areas have been completely revised and several newcomers have joined the original set of authors.

This popular book has proved invaluable as a teaching resource for two decades and is frequently used as a reference by practitioners in the field. Readers of earlier editions will benefit from updates on technologies such as nanoscience, and the legislative changes that have occurred since the fourth edition in 2001.

CHAPTER 1

Chemical Pollution of the Aquatic Environment by Priority Pollutants and its Control^†

OLIVER A.H. JONES^*a AND RACHEL L. GOMES,^b

^aSchool of Applied Sciences, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia; ^bDepartment of Chemical and Environmental Engineering, Faculty of Engineering University of Nottingham, University Park, Nottingham, NG7 2RD, UK

^*Email: [email protected]

1.1 INTRODUCTION

It is difficult to imagine the modern 21^st century lifestyle without the mobile phones, tablet PCs and social media that the majority of the general public have become accustomed to. Such technology is heavily reliant on chemicals and chemical technology. For example, solvents are widely used in electronics as solders and for cleansing, stripping, and degreasing operations and encapsulations. Solvents are also the cause of a significant portion of workplace hazards and exposure problems in not only the electronics industry but many others as well, for example agriculture, biotechnology and pharmaceuticals. The chemical industry is an important pillar of the modern world economy and the chemical industry affects nearly every part of our daily life.

Biological and physico-chemical processes operating in aquatic systems can remove pollutants from circulation, fix them more or less indefinitely, or degrade them to less harmful compounds. The self-purification capacity of many aquatic systems has led to their use for the indiscriminate disposal of society’s waste in the past. While the pollutants themselves are often invisible to the naked eye, their impact on water resources and aquatic life is often quite conspicuous. Pollutant discharges may cause fish kill events, noxious smells or even change the colour of the water, all of which are easily perceptible to the casual observer. However, there are also many chemical pollutants that may cause harm to the health of a watercourse while not affecting its outward appearance. It can be both difficult and expensive to remediate water pollution, and the future use of the water may be affected by the presence of chemicals.

Awareness of the issues involved with the presence of chemicals in the environment has been high since Rachel Carson drew attention to the negative effects of the indiscriminate use of pesticides in the early 1960’s.¹ Since that time, a growing environmental movement and the wide-ranging impact of social and digital media means that the public is often bombarded with sensational headlines and stories about pollution by both the scientific and mainstream press: from the greenhouse gas emissions generated by shipping food around the globe through to heavy metals from waste electrical and electronic equipment, and, most recently, nanoparticles and the other emerging environmental contaminants such as disinfection by-products, pharmaceuticals and hydraulic fracturing or fracking substances (see section 1.5.4).² In many such articles, terms such as “contamination” and “pollution” are often used somewhat interchangeably. It is important however, to make the distinction between them.

Contamination is simply the presence of a substance in a given sample where there is no evidence of harm. Pollution is contamination that results in, or can result in, adverse biological effects to individuals or communities.³ All pollutants are therefore contaminants but not all contaminants are pollutants. This means that differentiating pollution from contamination cannot be done on the basis of chemical analyses alone because such analyses provide no information on factors such as bioavailability or toxicity which influence whether a chemical presence actually causes harm.³ In addition, not all contaminants or pollutants are chemical in origin. Many different forms of pollution in the aquatic environment exist. These can be summarised as:

Chemical

• – Toxicity: acute or chronic toxicity causing severe damage (including death) to aquatic or human life.
• – Sub-lethal toxicity: such as endocrine disruption, physical impairment, reduction of immunological/biochemical function or changes in biodiversity.⁴
• – Deoxygenation: lack of oxygen in the water reducing biodiversity.

Biological

• – Spread of non-native and or invasive species to new systems.
• – Eutrophication: excess nutrients giving rise to excessive growths of some organisms.

Physical

• – Temperature: usually heat, for example from power station cooling systems.
• – pH level changes; changes in H⁺ levels in a water body may affect both chemical and biological processes; e.g. acid rain linked to reduced shell formation ability in molluscs.
• – Aesthetic: visual nuisance caused, e.g. litter, algal blooms, discoloration and smells.
• – Noise: seismic surveying, shipping, boat traffic, pile driving and navy sonars are all sources of marine noise pollution that can affect the health of marine mammals.^5,6
• – Light: increasing intentional and unintentional illumination of the coastal zone and near-shore (and increasing the deep sea) can interfere with the feeding, reproductive and migratory behaviour of some species.^7,8

It is important in pollution regulation to remember the “Source–Pathway–Receptor” model. Even the most potent toxin is harmless as long as it is isolated or contained and a compound designed to target a specific receptor is unlikely to have an effect in an organism that lacks such a receptor. It is also helpful to keep in mind one of the underlying principles of toxicology; namely that the dose makes the poison. All chemicals - even water and oxygen - can be toxic in certain amounts (although not all organisms respond the same way to chemicals at all stages of their life cycles). For example excessive heat will kill many species, either directly or by reducing the amount of O₂ than can be dissolved in the water body concerned. Many serious pollution incidents are caused by spills of seemingly harmless substance such as milk or sugar. These substances are not directly toxic in themselves; in fact they have the opposite effect. Their high organic content increases bacterial growth, which causes a concomitant decrease in dissolved oxygen levels.⁹ In some cases the milk itself could also be contaminated, for instance by radiation following a radiological accident¹⁰ such as the Chernobyl disaster which contaminated fields and animals across Europe in the late 1980 s¹¹ and the more recent Fukashima incident in Japan in March 2011; the impact and fallout of which was felt (albeit weakly) as far away as Western Europe.^12,13 Such incidents are of course thankfully, very rare.

So, in the 21^st century, society cannot function in the way in which it has become accustomed without producing pollution but left unchecked, such pollution will eventually undermine the functioning of said society. Consumers are currently encouraged to do their part, for example to reduce food miles by shopping locally, and to offset their carbon footprint by funding an equivalent carbon dioxide saving elsewhere (for example by investing in renewable energy projects). However, these are small savings. To ensure chemical pollution does not cause serious and irreparable damage to the environment there must be checks and balances in place to minimise the release of certain pollutants and the harm they could potentially cause. Such techniques may be economic and/or legal instruments. However, not everything can be regulated and it would not be economically or physically viable to do so. Thus, despite the fact that almost anything can be a pollutant, certain chemicals have been identified in regulations at a national, or increasingly international level, as being priority chemicals for control. Such pollutants generally meet one or more of the following criteria:¹⁴

• – They are frequently detected by environmental monitoring programs.
• – They are toxic at low concentrations.
• – They bioaccumulate.
• – They are persistent.
• – They are carcinogens.

For many of these substances the precautionary principle has been applied. Here the target is for no contamination to occur but there are different approaches and philosophies as to how to achieve the best environmental results.

1.2 POLLUTION CONTROL PHILOSOPHY

The public tend to think of pollution control in terms of mandatory regulations and there is no doubt that these are very important for environmental protection but they are only part of the solution. Other tools such as, environmental education, economic instruments, market forces and stricter enforcements all have roles to play in pollution control. Given the range of control measures available for environmental protection, preventing and controlling the release of priority chemicals to the aquatic environment can still be complex and challenging.

Controlling pollution to an environment has tended to rely on standards or objectives that are in some way measurable. The types of standards may be broadly divided into standards set by reference either to the target being protected, or the source of the pollution. The latter being further divided into standards covering emissions, process, product and use (see Table 1.1).

Table 1.1 Examples of standards utilised in pollution control. (Adapted from Ref. 15).

Type of standard	Description
Environmental quality standards	Concerned with the effect on a particular target. The degree of concentration in surface water for certain pollutants, substances or groups of substances identified as priority on account of the significant risk they pose to or via the aquatic environment.
	EU Directive in Environmental Quality Standards (Directive 2008/105/EC); Annex IX (Dangerous Substances Directive and associated Daughter Directives); Annex X (Water Framework Directive Priority List Substances).
Emission standards	Concerned with setting specific limits regarding the nature and volume of a pollutant present in a liquid discharged from a point source to a sewer or “controlled water”.
	Environmental Permitting (England and Wales) Regulations 2010 require environmental permits setting the maximum content of a...