Robert M. Newton

Chemical characteristics of Adirondack lakes

This paper discussed the role of atmospheric deposition of mineral acids in the acidification of low-ionic-strength (dilute) surface waters in remote regions. Surface water acidification has been attributed to the atmospheric deposition of sulfuric acid, sulfur dioxide, and nitric acid, the oxidation of organic nitrogen from the soil, the production of soluble organic acids through the decay of dead plants and animals in soil, the oxidation of naturally occurring sulfide minerals, and the changes in land use. The research reported here was conducted as part of the Regionalized Integrated Lake-Watershed Acidification Study (RILWAS). The intent was to evaluate the general chemical characteristics of lakes in the Adirondack region of New York and to access the mechanisms that regulate the acid-base chemistry of these waters. 36 references, 5 figures, 3 tables.

Chemical weathering in two Adirondack watersheds: Past and present-day rates

Rates of chemical weathering in two forested Adirondack watersheds were determined from mineral and elemental depletion trends in soil profiles and from input/output budgets based on precipitation and surface-water chemistry. Long-term rates of weathering have averaged about 500 to 600 eq/ha·yr for both watersheds since the glaciers retreated from the region about 14,000 yr ago. Present-day denudation rates average 1679 eq/ha·yr in the Panther Lake watershed and only 198 eq/ha·yr in the Woods Lake watershed. Mineral weathering reactions in both watersheds involve primarily the dissolution of plagioclase, potassium feldspar, and hornblende. Mass balance calculations, however, indicate that hornblende weathers in disproportionately large amounts in the Panther Lake watershed relative to its abundance in soils and till. Cation exchange in the glacial till mantling the Panther Lake watershed may also play an important role in controlling surface-water chemistry in the basin. In the Panther Lake watershed, the current rate of weathering, which is about a factor of 3 greater than the long-term average, may reflect a recent adjustment for higher hydrogen ion fluxes brought about by acid deposition. The capacity of the thick till deposits in the Panther Lake watershed to neutralize acidity is ultimately reflected by the circum-neutrality of Panther Lake. In the Woods Lake watershed, the soils and thin till deposits cannot effectively neutralize current acid loadings and, therefore, Woods Lake is acidic with a pH below 5.

The relationship between surface water chemistry and geology in the North Branch of the Moose River

The chemistry of lakes and streams within the North Branch of the Moose River is strongly correlated with the nature and distrubution of geologic materials in the watershed. The dominance of thin glacial till and granitic gneiss bedrock in the region north and east of Big Moose Lake results in a geologically sensitive terrain that is characterized by surface water with low alkalinity and chemical compositions only slightly modified from ambient precipitation. In contrast, extensive deposits of thick glacial till and stratified drift in the lower part of the system (e.g. Moss-Cascade valley) allow for much infiltration of precipitation to the groundwater system where weathering reactions increase alkalinity and significantly alter water chemistry.The hypothesis that surficial geology controls the chemistry of surface waters in the Adirondacks holds true for 70 percent of the Moose River watershed. Exceptions include the Windfall Pond subcatchment which is predominantly covered by thin till, yet has a high surface water alkalinity due to the presence of carbonate-bearing bedrock. The rapid reaction rates of carbonate minerals allow for complete acid neutralization to occur despite the short residence time of water moving through the system. Another important source of alkalinity in at least one of the subcatchments is sulfate reduction. This process appears to be most important in systems containing extensive peat deposits.An analysis of only those subcatchments controlled by the thickness of surficial sediments indicates that under current atmospheric loadings watersheds containing less than 3 percent thick surficial sediments will be acidic while those with up to 12 percent will be extremely sensitive to acidification and only those with over 50 percent will have a low sensitivity.

The nature of vermiculite in Adirondack soils and till

The clay and bulk mineralogy of soil and till from 26 Adirondack watersheds was studied. The materials consist typically of quartz, K-feldspar, plagioclase, mica, vermiculite, and kaolinite. Talc, smectite, halloysite, and hornblende are present in some samples. The clay fraction of the soils is composed predominantly of vermiculite, likely derived from the transformation of a mica precursor, and kaolinite. The soil vermiculite commonly contains hydroxy-Al interlayers which are especially prevalent in the B-horizon samples. Despite significant variation in the type of bedrock and the composition of heavy mineral assemblages in these watersheds, the clay mineralogy is remarkably uniform. This finding supports earlier suggestions that the occurrence of vermiculite in soils is more dependent on climate than on the nature of the parent material.

The Experimental Watershed Liming Study: Comparison of lake and watershed neutralization strategies

The Experimental Watershed Liming Study (EWLS) was initiated to evaluate the application of CaCO3 to a forested watershed in an effort to mitigate the acidification of surface water. The objective of the EWLS was to assess the response of the Woods Lake watershed to an experimental addition of CaCO3. During October 1989,6.89 Mg CaCO3/ha was applied by helicopter to two subcatchments comprising about 50% (102.5 ha) of the watershed area. The EWLS involved individual investigations of the response of soil and soil water chemistry, forest and wetland vegetation, soil microbial processes, wetland, stream and lake chemistry, and phytoplankton and fish to the CaCO3 treatment. In addition, the Integrated Lake/Watershed Acidification (ILWAS) model was applied to the site to evaluate model performance and duration of the treatment. The results of these studies are detailed in this volume. The purposes of this introduction and synthesis paper are to: 1) present the overall design of the EWLS, 2) discuss the linkages between the individual studies that comprise the EWLS, and 3) summarize the response of the lakewater chemistry to watershed addition of CaCO3 and compare these results to previous studies of direct lake addition. An analysis of lake chemistry revealed the watershed treatment resulted in a gradual change in pH, acid neutralizing capacity (ANC) and Ca2+ in the water column. This pattern was in contrast to direct lake additions of CaCO3 , which were characterized by abrupt changes following base addition and subsequent rapid reacidification. Over the three-year study period, the supply of ANC to drainage waters was largely derived from dissolution of CaCO3 in wetlands. Relatively little dissolution of CaCO3 occurred in freely draining upland soils. The watershed treatment had only minor effects on forest vegetation. The watershed treatment eliminated the episodic acidification of streamwater and the near-shore region of the lake during snowmelt, a phenomenon that occurred during direct lake treatments. Positive ANC water in the near-shore area may improve chemical conditions for fish reproduction, and allow for the development of a viable fish population. The watershed CaCO3 treatment also decreased the transport of A1 from the watershed to the lake, and increased the concentrations of dissolved organic carbon (DOC) and dissolved silica (H4SiO4) in stream and lakewater. The watershed treatment appeared to enhance soil nitrification, increasing concentrations of NO3 - in soilwater and surface waters. However, the acidity associated with this NO3 - release was small compared to the increase in ANC due to CaCO3 addition and did not alter the acid-base status of Woods Lake. Acid neutralizing capacity (ANC) budgets for 12-month periods before and after the watershed treatment showed that the lake shifted from a large source of ANC to a minor source due to retention of SO4 2-, NO3 -, Al and the elevated inputs of Ca2+ associated with the watershed CaCO3 application. In contrast to the direct lake treatments, Ca2+ inputs from the watershed application were largely transported from the lake.

Mineralogy and Mineral Weathering

Elements such as Ca, Mg, and K, which are required for plant growth, are important components of the nutrient cycle in forested ecosystems, and by far the largest store of these elements in North American and European forests is within the minerals constituting the forest soil. Although external inputs from the atmosphere in both the dissolved and particulate load can provide a portion of these elements to a growing forest, the ultimate source of most inorganic elemental nutrients is provided through cation exchange and mineral weathering reactions that take place in the soil profile. Mineral inventories and determinations of the physical characteristics, mineralogy and chemistry of soil components, and mineral weathering reactions that occur in soils must be an integral part of any study that attempts to document the nutrient status of a forested ecosystem.

Effect of whole catchment liming on the episodic acidification of two adirondack streams

During the fall of 1989 7.7Mg/ha of calcium carbonate was applied on two tributary catchments (40 ha and 60 ha) to Woods Lake, a small (25 ha) acidic headwater lake in the western Adirondack region of New York. Stream-water chemistry in both catchment tributaries responded immediately. Ac id-neutralizing capacity (ANC) increased by more than 200 μeq/L in one of the streams and more than 1000 μeq/L in the other, from pre-liming values which ranged from -25 to +40 μeq/L. The increase in ANC was primarily due to increases in dissolved Ca2+ concentrations. Most of the initial response of the streams was due to the dissolution of calcite that fell directly into the stream channels and adjacent wetlands. A small beaver impoundment and associated wetlands were probably responsible for the greater response observed in one of the streams.

MINERALOGY AND CHEMISTRY OF SOME ADIRONDACK SPODOSOLS

We determined the mineralogy and chemistry of spodosols in three Adirondack lake-watersheds by x-ray and electron microprobe analysis and by optical microscopy. The major minerals present in the soils are quartz, K-feldspar, plagioclase feldspar, and hornblende. Accessory minerals identified with the petrographic microscope include magnetite, ilmenite, hypersthene, garnet, tourmaline, epidote, and zircon. Vermiculite is the dominant clay mineral in the <2-μm fraction. Illite, kaolinite, mixed-layer illite/ vermiculite, smectite, and chlorite are also present, but are less abundant. Vermiculite in the soil profiles contains aluminum interlayer contaminants that prevent the mineral from collapsing to 10 A upon K-saturation. The data suggest that vermiculite in the soil horizons is derived mainly from the weathering of hornblende. The high content of extractable iron in these Adirondack soils (up to 6 wt% Fe) results from the chemical dissolution of iron-rich (ferrohastingsitic) hornblende.

Liming effects on some chemical and biological parameters of soil (spodosols and histosols) in a hardwood forest watershed

Acidic lakes and streams can be restored with base application (usually limestone) provided that the base does not wash out before the benefits of alkalization can be realized; liming soils of the adjoining watershed may be an alternative approach. This study was conducted to provide a scientific basis for soil liming. Plots (50 m2) with different limestone dosages (e.g. 0, 5, 10 or 15 Mg CaCO3 ha−1) were established on each of two different soils (a Spodosol and a Histosol) in the Woods Lake watershed of the Adirondack Park Region of New York, USA. Six months after soil liming much of the added limestone was still present in both the Spodosol and in the Histosol. Ten months after soil liming results indicated that: (1) soil pH increased (>1 unit) but mostly in the top 1 cm; (2) net N mineralization increased from 9.6 to ca. 15 µg N g−1 d−1 and nitrification increased from 2.8 to ca. 8 µg N g−1 d−1; (3) denitrification was not affected (98 µg N g−1 d−1); (4) CO2 production potential decreased in the surface soil and as a function of limestone dosage (60 to 6 µmol g−1 d−1); and (5) soluble SO42− concentrations in the Histosol were not affected (105 µmol L−1). Liming acidic forest soils with >5 Mg CaCO3 ha−1 may increase the soils acid neutralizing capacity, which could provide long-term benefits for surface water acidification.

Application of the Integrated Lake-Watershed Acidification Study model to watershed liming at Woods Lake, New York

Woods Lake, in the Adirondack Mountains of New York, was the site of the Experimental Watershed Liming Study (EWLS) in which base addition was investigated as a method for mitigation of lake acidity. In an effort to predict the duration of effects, the treatment was simulated using the Integrated Lake-Watershed Acidification Study (ILWAS) model. To simulate terrestrial liming, calcite was applied to treated subcatchments as a rapidly weathering mineral in the upper horizon. Soil solution and lake outlet chemistry showed a response to calcite addition within four months of the start of the simulation. Calcium concentrations, acid neutralizing capacities (ANC), and pH increased in the upper soil layer and aluminum concentrations decreased in the upper three soil layers (0–70 cm). The response of ANC was delayed in lower soil layers due to proton production associated with aluminum hydrolysis. Moreover, soil water pH in the third soil layer decreased in response to calcite treatment due to the displacement of hydrogen ions by calcium added to the exchange complex. Calcium concentrations, ANC and pH increased and aluminum concentrations decreased in the simulated lake outlet.