Sources of pollution
Most sources of pollution around the world are due to human interaction with the environment surrounding them. The Sonoran Desert is no special case either. There are various types of pollution in the Sonoran Desert, such as gas from vehicles, construction-related dust, power plant waste, exhaust from gas-powered lawn mowers, and exhaust from leaf blowers, which all contribute to the "brown cloud," a cloud literally made brown from pollution.
However, the primary reason for the majority of the pollution in the Sonoran Desert would be the seemingly endless amount of trash and waste. The majority of these items are: back-backs, water bottles or cans, food rappers, dirty clothing, human feces, and thousands of soiled baby diapers.