Water Facts

Water has three natural states: solid (ice); liquid; and, gas (vapor); and moves freely between these states. In its liquid form water has the ability to interact with solid matter (minerals, plant residues), dissolve minerals (chemicals), and carry particulates and microorganisms as it runs off and seeps into the ground. But, it is water vapor that completes the water cycle as it evaporates and condenses to form rain. This process distills water to its purest form and moves it across vast distances over the earth’s surface. Cycling through this natural distillation process is what makes rain and snow-melt fed “fresh water” rivers and streams an important resource.

Common Minerals Found in Water

Figure 9: Bottled water
label conforming to
USDA requirements
and non-US bottled
water (insert)
showing mineral
constituents

Fresh water in contact with soils and aquifer material typically contains common minerals including gypsum, calcite, and dolomite. Such minerals are the sources of common elements (ions) like calcium, magnesium, carbonates and sulfate. These ions together with potassium and salt (NaCl) account for 95% (by weight) of the total dissolved solids (TDS) found in natural fresh water. The amount and proportions of minerals in water affect its taste and can often be used to identify the origin of a water source. For example, popular brands of bottled water add specific proportions of minerals to distlled water to control water taste, as shown on Figure 9.

Numerous other chemicals found in soil and rock are also found in water in trace amounts. These include nutritionally beneficial elements like trace concentrations of copper, zinc, and iron and undesirable elements like arsenic, mercury, and radon gas. Waters that come into contact with minerals rich in these chemicals may contain elevated and potentially toxic concentrations to human health.

Contaminants in Water

Contaminants are divided into three categories: those of natural origin, those of natural origin but concentrated by human activities, and those human-made and introduced into the environment. Water sources also have unwanted but naturally occurring toxic elements like arsenic that may naturally concentrate to toxic levels in certain geologic setting. When naturally occurring arsenic is found in a drinking water source at concentrations above National Primary Drinking Water Standards (NPDWS), the water is considered to be “contaminated” with arsenic.

Human activities can also contaminate natural waters with excessive levels of minerals or pollutants. These activities include agricultural and industrial release of pollutants; improper disposal of municipal and animal wastes into air, soil, surface, and ground waters; and transportation and recreation on air, land, and water. The types and concentrations of contaminants that can be tolerated in drinking water without harm to human health are set by the US Environmental Protection Agency (EPA).

Human-made contaminants are also commonly referred to as pollutants. These include synthetic organic chemicals such as agricultural pesticides, industrial solvents, fuel additives, petroleum products, plastics and many other chemicals. Unfortunately, many of these chemicals are ubiquitous (present everywhere) in our environment due to their extensive use in modern society. Also, microbial pathogens derived from human and animal waste become pollutants when improperly disposed of, and can adversely impact the quality of water resources.