Which of the following are indicators of groundwater quality that should be monitored?

Monitoring groundwater quality is crucial for ensuring the safety and sustainability of this vital resource. The indicators mentioned in the chosen response—nutrients, pathogens, heavy metals, and pH levels—are essential because they provide a comprehensive understanding of the groundwater's health and potential risks to human health and the environment.

Nutrients, such as nitrates and phosphates, can indicate agricultural runoff that may lead to nutrient pollution, which can harm aquatic ecosystems. Pathogens, including bacteria and viruses, are critical to monitor as they pose direct health risks to humans and animals if groundwater becomes contaminated. Heavy metals like lead, mercury, and arsenic are toxic and can have severe health impacts when these contaminants infiltrate groundwater supplies. Finally, pH levels are important because they influence the solubility of other contaminants and the overall chemistry of the water.

By monitoring these parameters, we can identify potential contamination sources, assess water quality, and safeguard public health. This comprehensive approach ensures that all significant threats to groundwater quality are being evaluated, unlike the other options, which either lack breadth in coverage or focus exclusively on isolated factors.