, Volume 18, Issue 1-2, pp 55-63

Extent and effect of acid precipitation in northeastern United States and eastern Canada

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Abstract

The alkalinity-to-Σ(base cations) (ABC) ratios and [Aln+ and H+]-versus-[SO4 2−/Σ(base cations)] (AHSBC) plots were used to assess acid precipitation (AP) in northeastern USA and eastern Canada. ABC ratios were used to study the extents when the AP was not severe, and AHSBC plots were used to study the effects when the AP was severe. The Appalachians with calcareous bedrocks were least affected by AP (ABC ratio, 0.65), three New England States were subject to intermediate AP (ABC ratios, 0.49), and the Canadian Shield, New Hampshire and certain Adirondack lakes showed the effects of advanced AP (ABC ratios, 0.29). Groundwater hydrology also affects ratios where highest ABC ratios were recorded for lowest groundwater velocities (largest residence time), and vice versa in Quabbin Reservation, Massachusetts. Lower ABC ratios and higher AHSBC acidic cations in spring compared to summer confirmed the fact the H+ ions were released from spring snowmelt. AHSBC plots had decreasing ABC ratios from left to right when the contribution from Aln+ and organic acids was minimal, ABC ratios were large(e.g., Appalachian and Massachusetts); when the contribution of acidic cations dominated, ABC ratios were small(e.g., certain Adirondack lakes). Limitations associated with the ratio and plot in making interpretations are discussed.