Base cations such as calcium are important in the environment because deposition has an impact upon surface pH, causing an increase in alkalinity, thereby buffering or neutralizing the effects of acidity generated by sulphur and nitrogen. It is for this reason these emissions are of interest, rather than their negative impacts upon human health or ecosystems.
It was long assumed that the major source of base cations in the air was dust from soil erosion; however, patterns of concentrations in air and precipitation also suggest significant emissions from urban and industrial sources. The most significant contributors to calcium emissions are stationary combustion in the manufacturing industries, quarrying and mining of minerals, and residential combustion. Calcium emissions have decreased by 79% since 1990, due to changes in fuels used and decreasing production in some key sectors such as quarrying, though that sector was still the source of 49% of UK emissions of calcium in 2021. Some abatement of emissions is also likely through efforts to reduce particulate matter emissions from large industrial processes and power stations.