Proton Cycling in Bogs: Geographic Variation in Northeastern North America

Abstract

A detailed hydrogen ion budget has been constructed for the Marcell bog in north-central Minnesota based on a 5-year, intensive study of element cycles. Major features of the acidity balance for this site include the following: (1) production of organic acids (263 meg.m⁻².y⁻¹) is the dominant source of acidity and serves to buffer the bog water at pH 4; (2) seguestering of elements in peat is also a significant source of acidity (42.9 meg.m⁻².y⁻¹); (3) weathering of dustfall inputs is an important source of alkalinity (<76 meg.m⁻².y⁻¹) at this site which is situated near the major agricultural area of the plains; (4) nitrate and sulphate reduction contribute little alkalinity (<39.2 meg.m⁻².y⁻¹) because inputs (NO₃ and SO₄) to this bog are low. Analysis of peat and surface water from bogs across northeastern North America (Manitoba to Newfoundland) reveals the following: (1) production of organic acids across this region varies between 104 and 263 meg.m⁻².y⁻¹; (2) acidity-generation associated with net biological uptake (NBU, excluding nitrogen = 20–117 meg.m⁻².y⁻¹) varies in proportion to the rate of peat accumulation; (3) NBU-acidity exhibits high values in maritime bogs and lower values in mid-continental bogs; (4) bogs have a large capacity for sulphate reduction, and sulphate reduction becomes an increasingly important source of alkalinity as rates of sulphate deposition increase. From 60 to 93% of annual sulphate loadings are retained as reduced sulphur in bogs across eastern North America.