Wildfires burn at different temperatures, and the resulting smoke can have different effects on the soil. Cold wildfires, which burn at lower temperatures, produce more smoke that contains organic compounds. These compounds can condense on the soil surface and form a water-repellent layer. This layer can prevent water from infiltrating the soil, leading to flooding, erosion, and landslides.

The water-repellent layer formed by cold wildfire smoke can persist for several years. This can make it difficult for vegetation to reestablish after a fire, and can also lead to increased runoff and flooding.

In addition, cold wildfire smoke can also contain harmful pollutants, such as particulate matter, carbon monoxide, and nitrogen dioxide. These pollutants can have negative effects on human health, including respiratory problems, heart disease, and cancer.

Here are some specific examples of how cold wildfire smoke can contribute to water repellent soils in burned areas:

* In 2017, wildfires burned over 10 million acres in the western United States. The smoke from these fires produced a water-repellent layer on the soil in many areas, leading to flooding and erosion.

* In 2018, wildfires burned over 2 million acres in California. The smoke from these fires produced a water-repellent layer on the soil in many areas, leading to flooding and landslides.

* In 2019, wildfires burned over 4 million acres in Australia. The smoke from these fires produced a water-repellent layer on the soil in many areas, leading to flooding and erosion.

These are just a few examples of how cold wildfire smoke can contribute to water repellent soils in burned areas. This is a serious problem that can have a negative impact on human health and the environment.