8 Environmental Organic Chemistry#
Introduction#
Organic chemicals are crucial in modern society, influencing everything from consumer goods to pharmaceuticals and household products. Over 9 million carbon-based natural and man-made compounds have been identified. Given this vast number, it is not surprising that organic contaminants are widespread in our environment. When an organic compound is introduced into the natural environment, its fate depends on its physical and chemical properties.
In this chapter, we will become familiar with the basic principles of organic chemistry and how organic chemicals behave in the environment.
Fossil Fuels#
Fossil fuels are composed of hydrocarbons, which are compounds made up of hydrogen and carbon atoms. The carbon in fossil fuels primarily takes the form of hydrocarbons such as methane, ethane, propane, butane, and octane. These hydrocarbons are created from the remains of dead plants and animals that have been buried and subjected to heat and pressure over millions of years.
Natural gas is mainly composed of methane (\(\ce{CH4}\)), a simple hydrocarbon, but it can also include other hydrocarbons such as ethane (\(\ce{C2H6}\)), propane (\(\ce{C3H8}\)), and butane (\(\ce{C4H10}\)).
Coal primarily consists of carbon but contains small amounts of other elements, such as hydrogen, sulfur, oxygen, and nitrogen. Coal is formed from the remains of plants that existed millions of years ago, and the carbon in coal originates from the carbon present in these plants. The characteristics of this carbon can vary depending on factors such as the type of plant, the environment in which it grew, and the period in which it existed.
The exploitation of fossil fuels has indelibly impacted many of Earth’s environments.
Natural Organic Matter#
Carbon is the primary element in natural organic matter (NOM), which remains complex and poorly understood. NOM consists of intricate molecules formed from carbon bonded with other elements such as hydrogen, oxygen, and nitrogen.
Organic matter is a crucial component of soil and is essential to soil fertility. It helps retain water and nutrients in the soil and provides a habitat for soil organisms. Additionally, organic matter is a fundamental part of living organisms and is vital for life. It is used to construct cell structures and plays a role in many metabolic processes. The carbon in soil organic matter serves as an essential carbon reservoir within the global carbon cycle.
The carbon in organic matter is unstable and can be decomposed by microorganisms through oxidation, releasing \(\ce{CO2}\). This decomposition process is vital as it recycles nutrients into the soil, making them available for plants.
Understanding the properties and cycling of carbon in organic matter is crucial, as this knowledge can assist us in managing our resources wisely and protecting the environment.
Organic Pollutants in the Environment#
Anthropogenic organic pollutants are chemicals from various sources, including industrial emissions, agricultural runoff, and consumer products. These pollutants can adversely affect the environment by contaminating water and soil, harming wildlife, and disrupting human health.
Organic pollutants are commonly released into the environment through several avenues: industrial emissions (such as volatile organic compounds and untreated waste discharges), agricultural runoff (including herbicides and pesticides), consumer products (like nonstick cookware, household cleaners, and personal care items), and human and animal waste (containing substances like caffeine and medications).
Once these pollutants enter the environment, they can degrade water and soil quality. For instance, some pollutants can cause fish mortality or increase their disease susceptibility. Additionally, exposure to certain pollutants may lead to serious health issues, including cancer.
Understanding organic pollutants’ chemical nature, sources, and effects is crucial for developing strategies to protect the environment and human health.
Learning Goals#
Learning Goals
The main goals for this chapter are to:
learn the basics of organic chemical nomenclature,
explain how organic chemicals behave in various geological environments and
apply basic thermodynamic principles to determine the partitioning of organic chemicals in geological environments.