How does land pollution relate to water pollution?
A land polluter can become a water polluter
If the contaminant is soluble in water, it is a water pollutant. Think about a case, there is no water (July in some northern countries) as soil water and someone has been putting contaminants on land. When water (as rain, snow, etc.) is available some time later, such contaminants will be in water as water pollutants.
The important parameters (when we talk about water and soil pollution) are solubility of contaminant in water, adsorption capacity, soil organic carbon, temperature, etc.