Modern and paleolimnological evidence for accelerated leaching and metal accumulation in soils in New England, caused by atmospheric deposition

Abstract

Abstract. Empirical field evidence for changing chemical processes in soils caused by atmospheric deposition of pollutants consists of: (1) Long-term water quality data including total dissolved solids, concentrations of specific metals (e.g. Ca), and conductivity; (2) Cation exchange capacity and base saturation values for soils located on precipitation pH gradients; (3) Lysimeter studies; and (4) Chemical analysis of organic soils on precipitation pH and metal gradients. For well-drained organic soils, as precipitation pH decreases, metals are differentially leached at an accelerated rate (Mn > Ca > Mg >--Zn > Cd and Na > AI). Experimental field and laboratory lysimeter studies on soil columns yield similar results, with increases in leaching rates for soil solutions with pH = 3 up to 100 x values for soil solutions with pH = 5. Nearly 100% of the Pb from precipitation is accumulating in the organic soil layer or sediments. Zn is accumulating in soils and sediments where the pH's of precipitation, soil solutions, and surface waters are generally above 5 to 5.5. At lower pH values Zn and other chemically similar elements are desorbed/leached (net) at an accelerated rate.Chemical analyses of dated sediment cores from high and low altitude lakes, with drainage basins relatively undisturbed for the last 200 + yr, reveal that increased deposition of metals on a regional scale started in the northeastern United States as early as 1880, consistent with increased fossil fuel consumption. This suggests acidified precipitation as early as 1880. Cores from historically acidified lakes (pH < ~ 5.3 to 5.5) indicate that, as acidification of surface waters occurs (caused by acidic deposition), concentrations of Zn, Mn, and Ca decrease in the sediment. Apparently the metals are leached from the detritus prior to sedimentation. This conclusion results from data from experimental acidification of sediment cores and the general observation that precipitation pH is generally >--0.5 pH units lower than lake water pH. Accelerated leaching of soil in New England dates to earlier than 1900.

Changes in Concentrations of Major Elements and Trace Metals in Northeastern U.S.-Canadian Sub-Alpine Forest Floors

“…Concentrations of Ca, K, Mg, and Mn increased in forest floor litter (L) collected in 1978 from southern Vermont to Québec (Hanson et al, 1982). They implied that greater acidity and leaching to the southwest along this transect had caused lower concentrations of these elements.…”

“…Accumulations of trace metals in forest soils have frequently been utilized to assess spatial trends of pollutant deposition (Johnson et al, 1982;Hanson et al, 1982;Herrick and Friedland, 1990;Miller and Friedland, 1994). High elevation soils are particularly sensitive to changes in atmospheric chemistry due to higher deposition of pollutants by wet and dry deposition, interception of wet cloud moisture, the formation of rime ice, and the tenacity of highly organic soils to retain some metals.…”

“…The distribution and concentrations of major and trace metals in New England soils (Hanson et al, 1982;Friedland et al, 1992) and in lake and peat sediment (Norton et al, 1997) provide evidence for changing anthropogenic emissions of metals and acidic compounds to the atmosphere, deposition to the landscape, and subsequent acidification of soils and surface waters. The sources for much of the emissions deposited in the northeastern U.S. and eastern Canada lie principally to the southwest.…”

Hepatic mercury, cadmium, and lead in mink and otter from New York State: monitoring environmental contamination

“…Atmospheric deposition, predominately in the dry form, is an important source of Pb to forest systems (Lindberg et al 1982). Lead deposition in northeastern North America tends to be source-rather than elevationoriented, either locally or on a regional scale (Groet 1976;Hanson et al 1982). The mobility of Pb in soils is limited, controlled primarily by the solubility of bound organic material; therefore, although Pb has migrated from surface soil to mineral soil, transport to stream systems has been extremely limited and not related to elevation (Wang et al 1995).…”

Chemostratigraphy of the Holocene sediments of Lake Työtjärvi in southern Finland and its limnological significance

“…It has also been demonstrated that a fall in the pH of water greatly accelerates the passage of Ca into solution (e.g. Hanson et al 1982;Tolonen and Jaakkola 1983). A temporary increase noted in the content of calcium and magnesium in the pale grey gyttja layer in the lithostratigraphy of Lake Iidesjärvi (Vuorinen et al 1983, Fig.…”