Environmental chemistry

Environmental chemistry is the scientific study of chemical and biochemical phenomena in natural places. It focuses on the sources, reactions, transport, effects, and fates of chemical species. These species move through the air, soil, and water environments. Scientists also examine how human activity and biological activity influence these systems. This field is interdisciplinary, meaning it combines many different scientific areas. It relies heavily on analytical chemistry and includes atmospheric, aquatic, and soil chemistry.

To study environmental changes, chemists must first understand a clean, uncontaminated environment. They determine which chemicals are present naturally and in what concentrations. This baseline knowledge is essential for measuring human impact. Without it, scientists could not accurately judge the effects of released chemicals. They use traditional chemical concepts alongside specialized sampling and analytical techniques. This allows them to distinguish between natural cycles and human-caused changes.

Chemists often look for substances called contaminants. A contaminant is a substance present at levels higher than fixed natural levels. It might also be a substance that would not otherwise be there. If a contaminant detrimentally impacts the surrounding environment, it is called a pollutant. Sometimes a contaminant is present due to human activity but does not cause immediate harm. However, toxic or harmful effects from such contamination may only become apparent much later.

In these studies, scientists use specific terms to describe how chemicals interact with the world. The medium or organism affected by a pollutant is called a receptor. For example, a fish in a river might act as a receptor. A sink is a chemical medium or species that retains and interacts with a pollutant. A common example is a carbon sink. Scientists also monitor environmental indicators to check quality. These include dissolved oxygen (DO), pH levels, and nutrients like nitrates and phosphorus. They also measure heavy metals, such as copper, zinc, cadmium, lead, and mercury.

Pollutants can enter the environment through many different pathways. Industrial activity can cause heavy metal contamination of land. These metals can then be transported into water bodies and taken up by plants and animals. Oil spills or leaks can introduce polycyclic aromatic hydrocarbons (PAHs) into large bodies of water. Many PAHs are carcinogens and are extremely toxic. Scientists regulate these by concentration, often measured in parts per billion (ppb). On farms, nutrients can leach from land into water courses. This process can lead to eutrophication, which causes algal blooms.

Urban environments also contribute to chemical changes through runoff. During rainstorms, water washes off impervious surfaces like roads, rooftops, and parking lots. This urban runoff carries gasoline, motor oil, hydrocarbons, metals, nutrients, and sediment into the environment. To detect these, chemists use quantitative chemical analysis. Classical wet chemistry methods include gravimetric, titrimetric, and electrochemical techniques. For more complex tasks, they use sophisticated tools to find trace metals and organic compounds.

Advanced laboratory technology allows for incredibly precise measurements. Metals are often measured using atomic spectroscopy or mass spectrometry. Specific techniques include Atomic Absorption Spectrophotometry (AAS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Organic compounds like PAHs are measured using Gas chromatography-mass spectrometry (GC/MS). Some methods, like Tandem Mass spectrometry (MS/MS), can detect substances at sub part per trillion levels. For radioactive materials, scientists use particle counters and scintillation counters. Even biology helps through Polymerase Chain Reaction (PCR), which identifies microbial contamination by isolating DNA and RNA genes.

Many notable scientists have shaped this field through their research. Paul Crutzen, Mario Molina, and Sherry Roland all received the Nobel Prize in Chemistry in 1995. Other important figures include researchers like Susan Solomon, Werner Stumm, and Ellen Swallow Richards. Their work helps us understand the complex connections between chemistry and the Earth's systems. By studying these chemical processes, we gain a better understanding of how to manage our global environment.