In terms of concentrations, what is commonly used to express herbicide concentration in water?

Herbicide concentration in water is commonly expressed in parts per million (ppm) because this unit provides a clear and practical way to indicate very low concentrations typical in aquatic environments. PPM denotes how many parts of the herbicide are present in one million parts of the water. This is especially useful in aquatics, where the effective and safe levels of herbicides must be managed carefully to avoid harm to non-target organisms and maintain ecological balance.

Using ppm allows for precise communication between pesticide applicators and regulators, ensuring that concentrations remain within the safety limits established for various aquatic species. This precision is crucial in aquatic environments, where even small amounts of herbicide can have significant ecological impacts.

Other units like percent volume and parts per thousand (ppt) are less common in this context, as they are better suited for more concentrated solutions. Additionally, milligrams per liter (mg/L) is another valid unit of measurement for concentration in water, but parts per million is more universally understood and directly correlates to mg/L in the context of water, considering the density of water is close to 1,000 mg per liter.