What are the primary contaminants found in groundwater?

Groundwater can be impacted by a variety of contaminants, but the primary concerns typically include bacteria, nitrates, pesticides, and heavy metals. These contaminants are of particular importance because they can originate from various anthropogenic (human-made) activities and natural processes, posing serious health risks and environmental concerns.

Bacteria are a significant issue because they can indicate fecal contamination, which may lead to waterborne diseases. Nitrates often enter groundwater from agricultural runoff and wastewater, leading to issues such as methemoglobinemia, commonly known as "blue baby syndrome,” in infants. Pesticides, also prevalent in agricultural settings, can leach into groundwater, affecting both human and environmental health. Heavy metals, such as lead and arsenic, can occur naturally or as a result of industrial activities and can be toxic even at low concentrations.

Other options, while they include some contaminants found in water systems, do not capture the prevalent issues related to groundwater pollution as effectively as the correct choice. Microplastics and heavy metals, for example, while they are contaminants, microplastics are more commonly associated with surface water and ecosystems. Chlorine and salts are often byproducts of sanitation and industrial processes, respectively, but they are not primary contaminants in groundwater.