Science 2.

pH and Alkalinity Patterns in GLOBE Data Worldwide

Martha Conklin, Roger Bales & Josh Clemons

Department of Hydrology & Water Resources, University of Arizona

Over 1200 GLOBE schools from 45 countries have reported pH measurements, and over 100 schools have also reported alkalinity. This is a large population of sites, and can be used to give a snapshot in time of the acid-base status of surface waters in various parts of the world. However, because of differing frequency and duration of sampling at each school, a detailed analysis is needed in order to aggregate the measurements into a regional or global assessment. Using only data from GLOBE schools with multiple, reproducible pH and alkalinity values gives a distribution that is slightly lower than from a comparable large data set from a professional monitoring program in the U.S. GLOBE data also suggest that even within the U.S., surface waters exhibit more natural variability than is captured by the government-supported professional water-quality monitoring programs.