Why do pollution and smog often become trapped in los angeles and other similar urban areas?
there are no winds in los angeles.
the pollution that occurs there is heavier than the surrounding air, which leads to the buildup of smog.
increased electromagnetic radiation because of los angeles’s low altitude.
the combination of temperature inversions (because of being surrounded by mountains) and extended periods of sunlight result in the buildup of smog in los angeles.

The pollution that occurs there is heavier than the surrounding air, which leads to the buildup of smog

Explanation:

The large urban areas, such as Los Angels, are having big problems with controlling the pollution. These areas are large economic centers, with millions of people living in them. All the different economic sectors concentrated in such small space, plus the traffic, are causing lot of pollution of the air, filling it with particles of metal and toxic gases, which are heavier than the air itself. Because they are heavier, they tend to stay low and are much more static, causing buildup of them, resulting in smog.

answergeosphere;