Which of the following anions is most likely to leach?

Nitrate (NO3-) is highly soluble in water, which makes it particularly susceptible to leaching. This characteristic is a result of its negative charge, which prevents binding to soil particles that typically retain other nutrients or ions. In well-drained soils or during periods of heavy rainfall, nitrate can be easily washed away from the root zone of plants, potentially leading to water quality issues in nearby waterways.

While sulfate (SO4) and chloride (Cl) can also leach, the nitrate ion's affinity for mobility in water and its common fertilizer application make it a more significant concern regarding leaching. Phosphate (PO4), on the other hand, tends to bind tightly to soil particles and is much less likely to leach.