Several large rivers in the U.S. are less acidic now, due to decreasing acidic inputs, such as industrial waste, acid mine drainage, and atmospheric deposition, according to new research from the U.S. Geological Survey (USGS).
The study showed that alkalinity, a measurement of a river’s capacity to neutralize acid inputs, has increased over the past 65 years in 14 of the 23 rivers assessed in the U.S.
Reduced acidity levels were especially common in rivers in the Northeast, such as the Delaware and Schuylkill Rivers; the Midwest, such as the Illinois and Ohio Rivers; and the Missouri River in the Great Plains.
Acidification of U.S. rivers in the early part of the 20th century was mostly associated with these acid inputs, which reduced the alkalinity of some rivers and caused them to become more acidic.
Increased alkalinity concentrations in large rivers draining a variety of climate and land-use types in this country are an indicator of recovery from acidification.
By looking at changes in multiple chemicals, scientists conducting the study found that the alkalinity increases were due to decreasing acidic inputs. The reasons for decreased acidic inputs have been diverse and include greater regulation of industrial emissions and waste treatment and increased use of agricultural lime.
The study was published in the journal Science for the Total Environment.
source: U.S. Geological Survey