Mass balance is a research area in environmental science that involves evaluating the inputs, outputs, and changes in mass within a system. This can include tracking the movement of pollutants, nutrients, and other substances through various environmental compartments such as air, water, soil, and organisms. Mass balance studies are often used to assess the impact of human activities on the environment, to identify sources of pollution, and to develop strategies for managing and reducing environmental impacts. This research area is important for understanding the overall health and functioning of ecosystems and for informing environmental policy and decision-making.