The impacts of a watershed CaCO3 treatment on stream and wetland biogeochemistry in the Adirondack Mountains

Temporal and longitudinal variations in the chemistry of two tributary streams of Woods Lake in the Adirondack Mountains of New York were monitored before and after a watershed CaCO₃ application. One subcatchment of the lake had a large beaver pond and wetland at its headwaters, while the second was free-flowing. Treatment of both subcatchments with CaCO₃ resulted in an immediate increase in acid neutralizing capacity (ANC) associated with Ca²⁺ release. The extent and duration of the response to the treatment were greater in the wetland-impacted stream. Aluminum was retained and complexed with organic solutes generated within the beaver-pond. In the free-flowing stream, NO ₃ ^– concentration increased significantly after the manipulation; this pattern was not evident in the wetland-impacted stream. Net retention of SOkinf4/sup2– was evident in the beaver pond prior to and following treatment, and this response was enhanced after the watershed liming. Comparisons of beaver pond inlet/outlet concentrations, mass balance calculations, and in-pond profiles of chemical parameters revealed patterns of retention of SO ₄ ^2– , NO ₃ ^– and Al, and release of Fe²⁺, dissolved organic carbon (DOC) and NH ₄ ⁺ in the wetland during the summer before CaCO₃ treatment. Post-treatment releases of Ca²⁺ from the near-sediment zone in the beaver pond corresponded to anoxic periods in mid- to late-summer and under ice in winter. These findings demonstrate the importance of increased microbial processing of organic matter, along with high partial pressure Of CO₂ (Pco₂) in facilitating the dissolution of the applied CaCO₃. Dissolved silica (H₄SiO₄) was retained in the wetland during the summer prior to treatment but was released after the manipulation. This phenomenon may reflect the dissolution of diatom frustules or silicate minerals in the wetland at higher pH and DOC concentrations. Within two years of the CaCO₃ treatment 60% of the CaCO₃ applied to the beaver pond and surrounding wetland was dissolved and transported from the pond, in contrast to only 2.2% of the CaCO₃ applied to the upland subcatchment draining into the wetland. These results, coupled with high quantities of exchangeable Ca²⁺ found in sediments and onSphagnums mosses in the pond, demonstrate the importance of hydrologic source areas and wetlands in facilitating the dissolution of added CaCO₃ and in regulating the production of chemical species important in ANC generation.     

Processes regulating temporal and longitudinal variations in the chemistry of a low-order woodland stream in the Adirondack region of New York

Watershed processes influence the acid neutralizing capacity of surface waters by mediating changes in concentration of ionic solutes. Acidification of surface waters by atmospheric deposition of mineral acids and the extent to which ecosystem transformations neutralize this acidity are of particular concern. Seasonal variations in flow paths of water through soil and biological processes result in short-term changes in chemistry that may be critical to surface water ecology. In this study, we assessed longitudinal and temporal variations in the chemistry of a low-order stream, Pancake-Hall Creek, located in the west-central Adirondack region of New York. By quantifying changes in ionic solute concentration (e.g. Ca²⁺, Al^a+, SO ₄ ^2– , NO ₃ ^– ) we were able to evaluate processes responsible for short-term fluctuations in acid/base chemistry.In the headwater sites, stream water was acidic; changes in pH, acid neutralizing capacity (ANC) and Al were primarily due to seasonal variations in basic cation and NO ₃ ^– concentrations. At the downstream sites, water migrated through a large beaver impoundment and thick till resulting in higher pH, acid neutralizing capacity and basic cation concentrations, and lower concentrations of Al. Neutralization of acidity was particularly evident during the low flow summer period and coincided with retention of SO ₄ ^2– in the beaver impoundment. During the high flow non-summer (October to June) period, depressed pH and ANC, and elevated Al concentrations were observed in the downstream sites. Acidic conditions during the non-summer period were not due to the oxidation of reduced sulfur deposits (e.g. SO ₄ ^2– events) but rather the resumption of conservative SO ₄ ^2– transport through the beaver impoundment (e.g. minimal SO ₄ ^2– retention) coupled with increases in NO ₃ ^– .     

Phosphorus and nitrogen retention in five Precambrian shield wetlands

Phosphorus and nitrogen mass balances of five wetlands (two beaver ponds, two conifer-Sphagnum swamps and one sedge fen) situated in three catchments in central Ontario, Canada, were measured. Monthly and annual input-output budgets of total phosphorus (TP), total nitrogen (TN), total organic nitrogen (TON), total inorganic nitrogen (TIN), ammonium ion (NH₄ ⁺ -N), nitrate (NO ₃ ^– -N) and dissolved organic carbon (DOC) were estimated for the five wetlands during the 1982–83 and 1983–84 water years. Except for the deepest beaver pond (3.2 m) which had annual TP retention of –44% (–0.030 ± 0.015 g m^–2 yr^–1), the wetlands retained < 0.001 to 0.015 g M^–2 yr^–1 ; however, this wasless than 20% of the inputs and the estimated budget uncertainties were equal to or greater than the retention rates. Annual TN retentions ranged from –0.44 to 0.56 g m^–2 yr^–1 (–12 to 4%) but were not significantly different from zero. The wetlands transformed nitrogen by retaining TIN (16 to 80% RT) and exporting an equivalent amount as TON (–7 to 102% RT). The beaver ponds, however, retained NO ₃ ^– while NH ₄ ⁺ was passed through or the outputs exceeded the inputs. In contrast, the conifer swamps retained both NH ₄ ⁺ and NO ₃ ^– . DOC fluxes into and out of the beaver ponds were equal (–18 and 4% RT) but output from the conifer swamps exceeded input by > 90%. Marked seasonal trends in nutrient retention were observed. Nutrient retention coincided with low stream flow, increased evapotranspiration and biotic uptake during the summer. Net nutrient export occurred during the winter and spring when stream flows were highest and biotic uptake was low.     

Peat and solution chemistry responses to CaCO3 application in wetlands next to Woods Lake,New York

We studied the effect of a calcite (CaCO₃) treatment on peat and pore water chemistry in poor fen and conifer swamp wetlands next to Woods Lake and its tributaries to evaluate the role of wetlands in an Experimental Watershed Liming Study (EWLS). Peat was characteristically organic rich and nutrient poor, with exchangeable Ca concentrations of < 13 cmol_ckg^–1. We estimated that between 0.4 to 4 Mg (CaCO₃) ha^–1 fell directly on three study sites; however, one year after the treatment the increase in Ca concentration (0–8 cm depth) was equivalent to a (CaCO₃) dosage of 3 Mg ha^–1 with an additional 2–4 Mg ha^–1 of undissolved (CaCO₃) still present, suggesting the peat retained Ca supplied from uplands. Most aspects of peat chemistry including microbial respiration and SO₄ reduction did not respond to the treatment.Peat pore water (5 and 20 cm depths) had a mean pH of 4.82 before treatment with high concentrations of dissolved organic carbon (DOC mean of 790 mol C/l) and low Ca²⁺ concentration (mean of 32 mol/l). The (CaCO₃) treatment increased concentrations of Ca²⁺ to a mean of 87 mol/l and dissolved inorganic carbon (DIC) from 205 to a mean of 411 mol/l, whereas it decreased monomeric Al concentration from 19 to 10 mol/l. Otherwise, pore water chemistry showed little response to the treatment, at least within natural spatial and temporal variation of solute concentrations. The results suggest that liming watersheds with the relatively low (CaCO₃) dosage applied in this study can benefit acidic waters downstream by exporting more Ca and DIC and less monomeric Al, with otherwise little effect on the peat itself.     

The effects of liming an Adirondack lake watershed on downstream water chemistry

Calcite treatment of chronically acidic lakes has improved fish habitat, but the effects on downstream water quality have not previously been examined. In this study, the spatial and temporal effects of watershed CaCO₃ treatment on the chemistry of a lake outlet stream in the Adirondack Mountains of New York were examined. Before CaCO₃ treatment, the stream was chronically acidic. During spring snowmelt before treatment, pH and acid-neutralizing capacity (ANC) in the outlet stream declined, and NO ₃ ^– and inorganic monomeric aluminum (Al_IM) concentrations increased sharply. During that summer, SO ₄ ^– and NO ₃ ^– concentrations decreased downstream, and dissolved organic carbon (DOC) concentrations and ANC increased, in association with the seasonal increase in decomposition of organic matter and the attendant SO ₄ ^– -reduction process. A charge-balance ANC calculation closely matched measured downstream changes in ANC in the summer and indicated that SO ₄ ^– reduction was the major process contributing to summer increases in ANC. Increases in Ca²⁺ concentration and ANC began immediately after CaCO₃ application, and within 3 months, exceeded their pretreatment values by more than 130 eq/L. Within 2 months after treatment, downstream decreases in Ca²⁺ concentration, ANC, and pH, were noted. Stream mass balances between the lake and the sampling site 1.5 km downstream revealed that the transport of all chemical constituents was dominated by conservative mixing with tributaries and ground water; however, non-conservative processes resulted in significant Ca²⁺ losses during the 13-month period after CaCO₃ treatment. Comparison of substrate samples from the buffered outlet stream with those from its untreated tributaries showed that the percentage of cation-exchange sites occupied by Ca²⁺ as well as non-exchangeable Ca, were higher in the outlet-stream substrate than in tributary-stream substrate. Mass-balance data for Ca²⁺ H⁺, Al_IM, and DOC revealed net downstream losses of these constituents and indicated that a reasonable set of hypothesized reactions involving Al_IM, HCO ₃ ^– , Ca²⁺, SO ₄ ^– NO ₃ ^– , and DOC could have caused the measured changes in stream acid/base chemistry. In the summer, the sharp decrease in ANC continued despite significant downstream decreases in SO₄ ^2– concentrations. After CaCO₃ treatment, reduction of SO ₄ ^– was only a minor contributor to ANC changes relative to those caused by Ca²⁺ dilution from acidic tributaries and acidic ground water, and Ca²⁺ interactions with stream substrate.     

Solution chemistry profiles of mixed-conifer forests before and after fire

Solution chemistry profiles of mixed-conifer forests in granitic catchments of the Sierra Nevada were measured for three years before (1987–1990) and three years after (1990–1993) prescribed fire. Wet deposition, throughfall and soil solution samplers were installed in both white-fir and giant-sequoia dominated forest stands underlain by poorly developed inceptisols. Stream water chemistry was monitored as part of an ongoing study of catchment outputs. Calcium, NO ₃ ^– and Cl^– were the major ions in precipitation. Canopy leaching increased mean concentrations of all major ions, especially K⁺ and Ca²⁺. Water flux through the soil occurred largely during spring snowmelt. Forest floor leachate represented the most concentrated solutions of major ions. Interaction with the mineral soil decreased mean concentrations of most species and the average composition of soil solutions closely resembled stream water at baseflow. Bicarbonate alkalinity, Ca²⁺, Mg²⁺, and Na⁺ were enriched in stream water relative to precipitation whereas inputs of H⁺, NH ₄ ⁺ , NO ₃ ^– and SO ₄ ^2– were retained within the catchments.Burning of the forest understory and litter layer increased solute concentrations in soil solution and stream water. Mean soil solution Ca²⁺, Mg²⁺ and K⁺ concentrations increased more than 10 fold, but the relative predominance of these cations was not affected by burning. Sulfate concentration, which was very low in soil solutions of undisturbed stands (<25 mmol_c m^–3), increased more than 100 times following fire. Ammonium concentration exhibited a rapid, short-term increase and then a decrease below pre-burn levels. Changes in soil solution chemistry were reflected in catchment outputs.Corresponding author.     

Fluxes and transformations of nitrogen in a high-elevation catchment,Sierra Nevada

The fluxes and transformations of nitrogen (N) were investigated from 1985 through 1987 at the Emerald Lake watershed (ELW), a 120 ha high-elevation catchment located in the southern Sierra Nevada, California, USA. Up to 90% of annual wet deposition of N was stored in the seasonal snowpack; NO ₃ ^– and NH ₄ ⁺ were released from storage in the form of an ionic pulse, where the first fraction of meltwater draining from the snowpack had concentrations of NO ₃ ^– and NH ₄ ⁺ as high as 28 eq L^–1 compared to bulk concentrations of <5 eq L^–1 in the snowpack. The soil reservoir of organic N (81 keq ha^–1) was about ten times the N storage in litter and biomass (12 keq ha^–1). Assimilation of N by vegetation was balanced by the release of N from soil mineralization, nitrification, and litter decay. Mineralization and nitrification processes produced 1.1 keq ha^–1 yr^–1 of inorganic N, about 3 1/2 times the loading of N from wet and dry deposition. Less than 1% of the NH ₄ ⁺ in wet and dry deposition was exported from the basin as NH ₄ ⁺ . Biological assimilation was primarily responsible for retention of NH ₄ ⁺ in the basin, releasing one mode of H⁺ for every mole of NH ₄ ⁺ retained and neutralizing about 25% of the annual acid neutralizing capacity produced by mineral weathering in the basin. Nitrate concentrations in stream waters reached an annual peak during the first part of snowmelt runoff, with maximum concentrations in stream water of 20 eq L^–1, more than 4 times the volume-weighted mean annual concentrations of NO ₃ ^– in wet deposition. This annual peak in stream water NO ₃ ^– was consistent with the release of NO ₃ ^– from the snowpack in the form of an ionic pulse; however soil processes occurring underneath the winter snowpack were another potential source of this NO ₃ ^– . Concentrations of stream water NO ₃ ^– during the summer growing season were always near or below detection limits (0.5 eq L^–1).     

Electrical tolerance (breakdown) of theChara corallina plasmalemma: I. Necessity of Ca2+

Summary The relationship between the external Ca²⁺ concentrations [Ca²⁺]₀ and the electrical tolerance (breakdown) in theChara plasmalemma was investigated. When the membrane potential was negative beyond –350–400 mV (breakdown potential, BP), a marked inward current was observed, which corresponds to the so-called punch-through (H.G.L. Coster,Biophys. J. 5:669–686, 1965). The electrical tolerance of theChara plasmalemma depended highly on [Ca²⁺]₀. Increasing [Ca²⁺]₀ caused a more negative and decreasing it caused a more positive shift of BP. BP was at about –700 mV in 200 M La³⁺ solution. [Mg²⁺]₀ depressed the membrane electrical tolerance which was supposed to be due to competition with Ca²⁺ at the Ca²⁺ binding site of the membrane. Such a depressive effect of Mg²⁺ was almost masked when the [Ca²⁺]₀/[Mg²⁺]₀ ratio was roughly beyond 2.     

Concentration and flux of solutes from snow and forest floor during snowmelt in the West-Central Adirondack region of New York

Decreases in pH and increases in the concentration of Al and NO ₃ ^– have been observed in surface waters draining acid-sensitive regions in the northeastern U.S. during spring snowmelt. To assess the source of this acidity, we evaluated solute concentrations in snowpack, and in meltwater collected from snow and forest floor lysimeters in the west-central Adirondack Mountains of New York during the spring snowmelt period, 29 March through 15 April 1984.During the initial phase of snowmelt, ions were preferentially leached from the snowpack resulting in elevated concentrations in snowmelt water (e.g. H⁺ = 140 eq.l^–1; NO ₄ ^2– = 123 eq.l^–1; SO ₃ ^– = 160 eq.l^–1). Solute concentrations decreased dramatically within a few days of the initial melt (< 50 eq.l^–1). The concentrations of SO ₄ ^2– and NO ₃ ^– in snowpack and snowmelt water were similar, whereas NO^– ₃ in the forest floor leachate was at least two times the concentration of SO ₄ ^2– .Study results suggest that the forest floor was a sink for snowmelt inputs of alkalinity, and a net source of H⁺, NO ₃ ^– , dissolved organic carbon, K⁺ and Al inputs to the mineral soil. The forest floor was relatively conservative with respect to snowmelt inputs of Ca²⁺, SO ₄ ^2– and Cl^–. These results indicate that mineralization of N, followed by nitrification in the forest floor may be an important process contributing to elevated concentrations of H⁺ and NO ₃ ^– in streams during the snowmelt period.     

Mechanisms of low Na+-induced increase in intracellular calcium in KCl-depolarized rat cardiomyocytes

Although low Na⁺ is known to increase the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in cardiac muscle, the exact mechanisms of low Na⁺-induced increases in [Ca²⁺]_i are not completely defined. To gain information in this regard, we examined the effects of low Na⁺ (35 mM) on freshly isolated cardiomyocytes from rat heart in the absence and presence of different interventions. The [Ca²⁺]_i in cardiomyocytes was measured fluorometrically with Fura-2 AM. Following a 10 min incubation, the low Na⁺-induced increase in [Ca²⁺]_i was only observed in cardiomyocytes depolarized with 30 mM KCl, but not in quiescent cardiomyocytes. In contrast, low Na⁺ did not alter the ATP-induced increase in [Ca²⁺]_i in the cardiomyocytes. This increase in [Ca²⁺]_i due to low Na⁺ and elevated KCl was dependent on the extracellular concentration of Ca²⁺ (0.25–2.0 mM). The L-type Ca²⁺-channel blockers, verapamil and diltiazem, at low concentrations (1 M) depressed the low Na⁺, KCl-induced increase in [Ca²⁺]_i without significantly affecting the response to low Na⁺ alone. The low Na⁺, high KCl-induced increase in [Ca²⁺]_i was attenuated by treatments of cardiomyocytes with high concentrations of both verapamil (5 and 10 M), and diltiazem (5 and 10 M) as well as with amiloride (5–20 M), nickel (1.25–5.0 mM), cyclopiazonic acid (25 and 50 M) and thapsigargin (10 and 20 M). On the other hand, this response was augmented by ouabain (1 and 2 mM) and unaltered by 5-(N-methyl-N-isobutyl) amiloride (5 and 10 M). These data suggest that in addition to the sarcolemmal Na⁺–Ca²⁺ exchanger, both sarcolemmal Na⁺–K⁺ATPase, as well as the sarcoplasmic reticulum Ca²⁺-pump play prominent roles in the low Na⁺-induced increase in [Ca²⁺]_i. (Mol Cell Biochem 263: 151–162, 2004)     

Nitrate removal in a first-order stream: reconciling laboratory and field measurements

A combination of laboratory and field experiments were carried out to evaluate nitrate(NO ₃ ^t- ) removal during stream transport in a first-order agricultural drainage stream. Intact stream sediment cores overlain with stream and NO ₃ ^– -amended stream water indicated NO ₃ ^– losses averaging 93 — 353 mg m^–2 day^–1, with NO ₃ ^– concentration exerting a primary control on loss rate. Isotopic data indicated enrichment of NO ₃ ^– - ¹⁵N over time as NO ₃ ^– concentrations decreased, indicating a denitrification loss. Field experiments were designed to evaluate dilution of streamwater with low-NO ₃ ^– groundwater in addition to other NO ₃ ^– removal processes during transport. A series of bromide tracer and NO ₃ ^– - addition experiments were carried out in the field; groundwater dilution dominated the downstream NO ₃ ^– concentration trends, accounting for all observed decreases in NO ₃ ^– concentration. Isotopic data did not point to denitrification downstream as a major NO ₃ ^– removal process. This apparent disparity between simulated laboratory and in-situ stream removal rates appears to be a function of the hydrological processes controlling exchanges between stream bottom sediments and the overlying water. These results suggest that caution must be exercised in extrapolating potentials for NO ₃ ^– removal measured in laboratory experiments to the field, as these rates could be overestimated in some watersheds.     

Electrogenic calcium transport in plasma membrane of rat pancreatic acinar cells

Summary ATP-dependent⁴⁵Ca²⁺ uptake was investigated in purified plasma membranes from rat pancreatic acinar cells. Plasma membranes were purified by four subsequent precipitations with MgCl₂ and characterized by marker enzyme distribution. When compared to the total homogenate, typical marker enzymes for the plasma membrane, (Na⁺,K⁺)-ATPase, basal adenylate cyclase and CCK-OP-stimulated adenylate cyclase were enriched by 43-fold, 44-fold, and 45-fold, respectively. The marker for the rough endoplasmic reticulum was decreased by fourfold compared to the total homogenate. Comparing plasma membranes with rough endoplasmic reticulum, Ca²⁺ uptake was maximal with 10 and 2 mol/liter free Ca²⁺, and half-maximal with 0.9 and 0.5 mol/liter free Ca²⁺. It was maximal at 3 and 0.2 mmol/liter free Mg²⁺ concentration, at an ATP concentration of 5 and 1 mmol/liter, respectively, and at pH 7 for both preparations. When Mg²⁺ was replaced by Mn²⁺ or Zn²⁺ ATP-dependent Ca²⁺ uptake was 63 and 11%, respectively, in plasma membranes; in rough endoplasmic reticulum only Mn²⁺ could replace Mg²⁺ for Ca²⁺ uptake by 20%. Other divalent cations such as Ba²⁺ and Sr²⁺ could not replace Mg²⁺ in Ca²⁺ uptake. Ca²⁺ uptake into plasma membranes was not enhanced by oxalate in contrast to Ca²⁺ uptake in rough endoplasmic reticulum which was stimulated by 7.3-fold. Both plasma membranes and rough endoplasmic reticulum showed cation and anion dependencies of Ca²⁺ uptake. The sequence was K⁺>Rb⁺>Na⁺>Li⁺>choline⁺ in plasma membranes and Rb⁺K⁺Na⁺>Li⁺>choline⁺ for rough endoplasmic reticulum. The anion sequence was Cl^–Br^–I^–>SCN^–>NO ₃ ^– >isethionate^– >cyclamate^–>gluconate^–>SO ₄ ^2– glutarate^– and Cl^–>Br>gluconate>SO ₄ ^2– >NO ₃ ^– >I^–>cyclamate^–SCN^–, respectively. Ca²⁺ uptake into plasma membranes appeared to be electrogenic since it was stimulated by an inside-negative K⁺ and SCN diffusion potential and inhibited by an inside-positive diffusion potential. Ca²⁺ uptake into rough endoplasmic reticulum was not affected by diffusion potentials. We assume that the Ca²⁺ transport mechanism in plasma membranes as characterized in this study represents the extrusion system for Ca²⁺ from the cell that might be involved in the regulation of the cytosolic Ca²⁺ level.     

Forest soil solutions: Acid/base chemistry and response to calcite treatment

Soil solution chemistry was investigated at a forested watershed draining into Woods Lake. N.Y. as part of the Experimental Watershed Liming Study (EWLS). The objective of this study was to assess the response of soil water to watershed treatment of calcite (CaCO₃). This material was applied in an effort to mitigate the effects of acidic atmospheric deposition. Soil solutions draining Oa and Bs horizons in reference subcatchments were characterized by low pH and acid neutralizing capacity (ANC) due to elevated concentrations of SO ₄ ^2– , NO ₃ ^– and organic anions relative to the sum of base cation (C_B Ca²⁺, Mg²⁺, Na⁺, K⁺) concentrations. Seasonal and spatial variation of pH andANC in soil solutions appeared to belargely controlled by variations in the concentrations of dissolved organic acids which, in turn, were regulated by reactions of Al with soil organic matter. Nitrate was positively correlated and SO²⁺ was negatively correlated with Ca²⁺ and Al concentrations in reference soil solutions, indicating that changes in NO ₃ ^– influences spatial and seasonal variations in Ca²⁺ and Al concentrations. On this basis, NO ₃ ^– appears to be important in soil acidification and the dynamics of drainage water acidity. Comparison of our results with historical data for the site showed declines in concentrations of SO ₄ ^2– , which are consistent with decreases in emissions of SO₄, in the eastern U.S. and atmospheric deposition of SO ₄ ^2– , to the Adirondack region. Mineral soil solutions have shown large increases in concentrations of NO ₃ ^– . Declines in concentrations of C_B and increases in concentrations of Al have occurred over the last ten years, suggesting depletion of soil pools of exchangeable basic cations and increased sensitivity to acidic deposition. Calcite (CaCO₃) treatment of 6.89 Mg/ha resulted in a significant increase of Ca²⁺, ANC and pH in both Oa and Bs horizon soil solutions. Soil water response to CaCO₃ addition was most evident during the first year after treatment, apparently due to macropore transport of particulate and dissolved CaCO₃ However, increases in ANC and pH in the mineral soil waters were not sustained and appeared insufficient to result in substantial improvement in surface water quality over the 43 month study period.     

Atmospheric deposition and solute export in giant sequoia — mixed conifer watersheds in the Sierra Nevada,California

Atmospheric depostion and stream discharge and solutes were measured for three years (September 1984 — August 1987) in two mixed conifer watersheds in Sequoia National Park, in the southern Sierra Nevada of California. The Log Creek watershed (50 ha, 2067–2397 m elev.) is drained by a perennial stream, while Tharp's Creek watershed (13 ha, 2067–2255 m elev.) contains an intermittent stream. Dominant trees in the area include Abies concolor (white fir), Sequoiadendron giganteum (giant sequoia), A. magnifica (red fir), and Pinus lambertiana (sugar pine). Bedrock is predominantly granite and granodiorite, and the soils are mostly Pachic Xerumbrepts. Over the three year period, sulfate (SO₄ ^2–), nitrate (NO₃ ^–), and chloride (Cl^–1) were the major anions in bulk precipitation with volume-weighted average concentrations of 12.6, 12.3 and 10.0 eq/1, respectively. Annual inputs of NO₃-N, NH₄-N and SO₄-S from wet deposition were about 60 to 75% of those reported from bulk deposition collectors. Discharge from the two watersheds occurs primarily during spring snowmelt. Solute exports from Log and Tharp's Creeks were dominated by HCO₃ ^–, Ca²⁺ and Na⁺, while H⁺, NO₃ ^–, NH₄ ⁺ and PO₄ ^3– outputs were relatively small. Solute concentrations were weakly correlated with instantaneous stream flow for all solutes (r² <0.2) except HCO₃ ^– (Log Cr. r² = 0.72; Tharp's Cr. r² = 0.38), Na⁺ (Log Cr. r² = 0.56; Tharp's Cr. r² = 0.47), and silicate (Log Cr. r² = 0.71; Tharp's Cr. r² = 0.49). Mean annual atmospheric contributions of NO₃-N (1.6 kg ha^–1), NH₄-N (1.7 kg ha^–1), and SO₄-S (1.8 kg ha^–1), which are associated with acidic deposition, greatly exceed hydrologic losses. Annual watershed yields (expressed as eq ha^–1) of HCO₃ ^– exceeded by factors of 2.5 to 37 the annual atmospheric deposition of H⁺.     

The effect of boromycin on the Ca2+ homeostasis

A boron-containing antibiotic, boromycin (BM), was found to influence the Ca²⁺ homeostasis in both excitable and non-excitable cells. In non-excitable cells (human erythrocytes and leucocytes) it inhibited the resting passive⁴⁵Ca²⁺ transport in 10^–6–10^–5 mol/L concentrations. In human erythrocytes, the passive ⁴⁵Ca²⁺ transport induced by the presence of 1 mmol/L NaVO₃ was inhibited by boromycin (90% inhibition) as well. The inhibitory effect of BM on the NaVO₃-induced passive ⁴⁵Ca²⁺ transport was diminished in the presence of inhibitory concentrations of nifedipine (10 mol/L – 60% inhibition) or of those of K⁺ _o (75 mmol/L – 20% inhibition). On the other hand, in rat brain synaptosomes, and rat cardiomyocytes, BM stimulated the passive ⁴⁵Ca²⁺ transport in resting cells at similar concentrations. In rat cardiomyocytes the stimulation was transient. The stimulatory effect on the passive ⁴⁵Ca²⁺ transport in rat brain synaptosomes was accompanied with the increase of cytoplasmic Ca²⁺ concentration measured by means of the entrapped fluorescent Ca²⁺ chelator fura-2. The stimulatory effect of BM was diminished when synaptosomes were pre-treated with veratridine (10 mol/L) which itself stimulated the passive ⁴⁵Ca²⁺ transport. At saturating concentrations of veratridine, no stimulatory effect of BM was observed. These results could be explained by the indirect interaction of BM with both Ca²⁺ and Na⁺ transport systems via transmembrane ionic gradients of monovalent cations and could be useful in determining whether the cells belong to excitable, or non-excitable cells.     

Intracellular Calcium Changes in Neuronal Cells Induced by Alzheimer's ß-Amyloid Protein Are Blocked by Estradiol and Cholesterol

1. The elevation of intracellular Ca²⁺ levels ([Ca²⁺]_i) in immortalized hypothalamic neurons (GT1–7 cells) after exposure to Alzheimer's ß-amyloid protein (AßP[25–35]) was investigated using a multisite fluorometry system.2. The marked rise in [Ca²⁺]_i appeared afterexposure to 5–20-M AßP[25–35]. Analysis of the spatiotemporal patterns of [Ca²⁺]_i changes revealed that the magnitude and the latency of the response to AßP in each cell werehighly heterogeneous.3. The preadministration of 17ß-estradiol, 17-estradiol, phloretin and cholesterol, which influence the properties of membranes, such as membrane fluidity or membrane potential, significantly decreased the rise in [Ca²⁺]_i.4. These findings support the idea that disruption of calcium homeostasis by AßP channels may be the molecular basis of the neurotoxicity of AßP and of the pathogenesis of Alzheimer's disease. It is also suggested that membrane properties may play key roles in the expression of neurotoxicity.     

Epidermal solute concentrations and osmolality in barley leaves studied at the single-cell level

The solute relations of the upper epidermis of the third leaf of barley (Hordeum vulgare L. cv. Klaxon) were studied by analysing vacuolar saps extracted from individual cells. Their osmolality (nanolitre osmometry) and the concentrations of K, Na, Ca, Cl, P, S (energy dispersive X-ray analysis) and NO ₃ ^– (microfluorometry) were measured. All of the osmotically important solutes were accounted for. These were K⁺, NO ₃ ^– , Cl^–, and Ca²⁺. The concentration of each solute varied along the leaf blade and changed with leaf age. Calcium in particular increased during leaf ageing, exceeding concentrations of 50 mM. Plants starved of Ca²⁺ during this period accumulated epidermal K⁺ instead of Ca²⁺. Leaf ageing was accompanied by an increase in epidermal osmolalities by about 100 mosmol · kg^–1. When compared to the bulk leaf extract, epidermal cell extracts exhibited significantly higher concentrations of NO ₃ ^– , Cl^– and Ca²⁺, similar concentrations of K⁺ and Na⁺, and lower concentrations of P. In plants subjected to various levels of NaCl stress (up to 200 mM), epidermal concentrations of Cl^– always exceeded those of the bulk extract, while Na⁺ concentrations were similar. Epidermal cells osmotically adjusted to the increase in the external salt concentration.Abbreviations EDX analysis energy dispersive X-ray analysis We wish to thank Paul Richardson, Jeremy Pritchard, Peter Hinde, Eirion Owen and Andrew Davies (Banger) for their helpfull discussion and technical advice. This work was financed by a grant (UR5/ 521) from the Agricultural and Food Research Council.     

Receptor capping in mouse T-lymphoma cells: A Ca2+ and calmodulin-stimulated ATP-dependent process

Summary The roles that Ca²⁺, calmodulin, and ATP play in the redistribution of conconavalin A (Con A) binding sites on the surface of mouse T-lymphoma cells were examined. Membranes of cells labeled with fluorescein-conjugated Con A (Fl-Con A) were made permeable (skinned) to ions and proteins by incubation in a solution containing no added Ca²⁺, 7mm EGTA, and ATP. The intracellular ionic and protein concentrations could then be varied, and the degree of Con A receptor capping monitored simultaneously. A graded increase (9.0 to 30%) was found in the number of capped cells with increasing Ca²⁺ concentration from 10^–6–10^–4.9 m. Increasing concentrations of trifluoperazine, chlorpromazine, and promethazine (1.5×10^–6 to 1.0×10^–4 m) in cell suspensions containing 10^–4 m Ca²⁺ produced graded inhibition of capping in the same order that the drugs bind to calmodulin. Removal of extracellular Ca²⁺ dissociated (reversed) some of the caps into patches, thus reducing their number (12%). ATP was required for either capping or cap dissociation to occur. Addition of calmodulin (3.9×10^–8–6.3×10^–7 m) to the cell suspension increased the Ca²⁺ sensitivity. These results provide direct evidence that capping of Con A receptors is a reversible process (i) regulated by intracellular Ca²⁺ concentration, (ii) requiring ATP as an energy source, and (iii) susceptible to the influence of calmodulin. These findings are consistent with the hypothesis that the collection of surface receptor patches into cap structures is controlled by the interaction of actomyosin filaments, which in turn is regulated by a Ca²⁺-calmodulin-activated control system.     

Characteristics of the Inhibitory Effect of Calmodulin on Specific [125I]Omega-Conotoxin GVIA Binding to Crude Membranes from Chick Brain

The characteristics of the inhibitory effect of calcium ion (Ca²⁺)/calmodulin (CaM) on specific [¹²⁵I]-omega-conotoxin GVIA (¹²⁵I--CTX) binding and on the labeling of ¹²⁵I--CTX to crude membranes from chick brain were investigated. The inhibitory effect of Ca²⁺/CaM depended on the concentrations of free Ca²⁺ and CaM. The IC₅₀ values for free Ca²⁺ and CaM were about 2.0 × 10^–8 M and 3.0 g protein/ml, respectively. The inhibitory effect of Ca²⁺/CaM was attenuated by the CaM antagonists W-7, prenylamine and CaM-kinase II fragment (290–309), but not by the calcineurin inhibitor FK506. Ca²⁺/CaM also inhibited the labeling of a 135-kDa band (which was considered to be part of N-type Ca²⁺ channel ₁ subunits) with ¹²⁵I--CTX using a cross-linker. These results suggest that Ca²⁺/CaM affects specific ¹²⁵I--CTX binding sites, probably N-type Ca²⁺ channel ₁ subunits, in crude membranes from chick whole brain.     

Fate of 15N labelled urine on four soil types

A field lysimeter experiment was conducted over a 406 day period to determine the effect of different soil types on the fate of synthetic urinary nitrogen (N). Soil types included a sandy loam, silty loam, clay and peat. Synthetic urine was applied at 1000 kg N ha^-1, during a winter season, to intact soil cores in lysimeters. Leaching losses, nitrous oxide (N₂O) emissions, and plant uptake of N were monitored, with soil ¹⁵N content determined upon destructive sampling of the lysimeters. Plant uptake of urine-N ranged from 21.6 to 31.4%. Soil type influenced timing and form of inorganic-N leaching. Macropore flow occurred in the structured silt and clay soils resulting in the leaching of urea. Ammonium (NH ₄ ⁺ –N), nitrite (NO ₂ ^- –N) and nitrate (NO₃ ^-–N) all occurred in the leachates with maximum concentrations, varying with soil type and ranging from 2.3–31.4 g NH ₄ ⁺ –N mL^-1, 2.4–35.6 g NO ₂ ^- –N mL^-1, and 62–102 g NO ₃ ^- –N mL^-1, respectively. Leachates from the peat and clay soils contained high concentrations of NO ₂ ^- –N. Gaseous losses of N₂O were low (<2% of N applied) over a 112 day measurement period. An associated experiment showed the ratio of N₂–N:N₂O–N ranged from 6.2 to 33.2. Unrecovered ¹⁵N was presumed to have been lost predominantly as gaseous N₂. It is postulated that the high levels of NO ₂ ^- –N could have contributed to chemodenitrification mechanisms in the peat soil.