About 30 volunteers took part in the pickup organized by Caterpillar Inc. in partnership with Tucson Clean and Beautiful and the Sonoran Institute. In addition, several employees worked with the Sonoran Institute on riverbed litter quantification studies. These simple surveys identify and categorize trash found with in 10 meter by 10 meter square areas with the goal of learning ways to control pollution at its source and coming up with strategies to better capture trash once it has reached the riverbed. Here, Luke Cole with the Sonoran Institute explains more about the surveys. (Josh Galemore/Arizona Daily Star)