Search results for "Organic carbon"
showing 10 items of 319 documents
Effects of eutrophication and organic loading on the occurrence of profundal harpacticoids in a lake in southern Finland.
1992
Harpacticoids made up 19 and 30% of the meiobenthos proper by number and 39 and 55% by biomass at maximum depths and a depth of 20 m, respectively, in Lake Paijanne. Harpacticoids accounted for higher proportions of the total meiobenthos in oligotrophic and unpolluted areas than in polluted areas. Seven species were identified, with Canthocamptus staphylinus confined to semi-lotic areas influenced by organic pollution from a pulp mill. Other species exhibited somewhat different distributions in oligotrophic and mesotrophic areas. Harpacticoid densities were most closely correlated with oxygen content and phytoplankton biomass, and correlations with environmental values were closer at maximu…
Responses of microbial food web to increased allochthonous DOM in an oligotrophic subarctic lake
2013
Climate-induced changes in catchment area vegetation and runoff alter the quality and quantity of carbon that enters lakes, with implications for food webs in recipient water bodies. The effect of dissolved organic matter (DOM) on the ratio between heterotrophic and autotrophic biomass and productivity was studied in a subarctic, clear water lake in northern Finland. In a mesocosm experiment, natural DOM from a subarctic bog and a boreal lake was added to the lake water, doubling the initial dissolved organic carbon (DOC) concentration. Optical indices sug- gested that the subarctic DOM addition was more bioavailable, which was in line with the greater increase in bacterial biomass and prod…
Chemical evolution of dissolved inorganic carbon species flowing in thin water films and its implications for (rapid) degassing of CO2 during speleot…
2013
Abstract Rapid degassing of CO2 from a thin film of drip water on the surface of stalagmites is often considered to have a large effect on both speleothem growth and stable isotope values and is offered as an explanation for higher δ13C and δ18O values than expected under conditions of stable isotope equilibrium. However, the time constant for degassing of CO2 from the solution only depends on film thickness and the coefficient of molecular diffusion for CO2. Thus, for thin films, the time for degassing of CO2 is much shorter than the time for subsequent equilibration of the dissolved carbon species and precipitation of CaCO3. In this context, degassing of CO2 is always fast. Here we presen…
Processes affecting the stable isotope composition of calcite during precipitation on the surface of stalagmites: Laboratory experiments investigatin…
2016
Abstract We present a theoretical derivation of the exchange time, τex, needed to establish isotopic equilibrium between atmospheric CO2 in a cave and HCO3− dissolved in a thin water film covering the surface of a speleothem. The result is τ ex = τ red ex · [ HCO 3 - ] K H · p CO 2 cave , where τ red ex depends on the depth, a, of the water film and on temperature. [ HCO 3 - ] is the concentration of bicarbonate, p CO 2 cave the partial pressure of CO2, and KH is Henry’s constant. To test the theory we prepared stagnant or flowing thin films of a NaHCO3 solution and exposed them at 20 °C to an CO2 containing atmosphere of p CO 2 500, 12,500, or 25,000 ppmV and defined isotope composition. T…
Modelling carbon isotopes of carbonates in cave drip water
2011
Abstract C isotopes in cave drip water are affected by both the C isotope composition of soil air and host rock carbonate. Furthermore, the C isotope composition of cave drip water strongly depends on the calcite dissolution system, i.e., open, closed and intermediate conditions. Here, we present a calcite dissolution model, which calculates the 14C activity and δ13C value of the dissolved inorganic carbon of the drip water. The model is based on the chemical equations describing calcite dissolution ( H 2 O + CaCO 3 + CO 2 ⇔ Ca 2 + + 2HCO 3 - ). The most important improvement, relative to previous models, is the combination of the open and closed system conditions in order to simulate the C…
Short-term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions
2013
The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara-dust inputs particularly increasing Ca deposition. We added CaCl2 to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 x 5kg ha(-1) Ca annually as CaCl2) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions…
Soil carbon and soil physical properties under land use change in a protected area of Sicily
2010
This work investigated the role of land cover and land use change as a soil’s ability to store carbon and reduce carbon dioxide emission in a Mediterranean area. Using both historic records and land cover crop maps we estimated the effect of land cover change on the carbon stock from 1972 to 2008 in a natural reserve (Grotta di S. Ninfa) in the West of Sicily. Five paired sites in different soil types were selected and five land use classes (arable land, vineyard, olivegrove, gariga, eucalyptus afforestation) were analyzed. We studied the effect of land use on soil organic carbon (SOC) content in bulk soil and 1000-2000 m, 500-1000 m, 250-500 m, 63-250 m, 25-63 m and <25 m size fractions. F…
Origin and significance of the production of carbon dioxide during the ozonization of 13C-labeled D-glucose at different pH values.
2001
Abstract [1- 13 C], [2- 13 C] and [6- 13 C] d -glucose were, respectively, ozonized in a semi-batch reactor in acidic and basic conditions. The composition of the gas phase was evaluated by on-line mass spectrometry measurements. The quantitative and isotopic analyses of the carbon dioxide formed during ozonization are presented and discussed. The data, correlated with previous literature results, clearly show that at pH 2.5 the production of carbon dioxide from C-6 and C-1 carbon atoms is nearly equivalent. Conversely, at higher pH values, CO 2 is released with a greater selectivity from the reducing end. The importance of the decarboxylation reaction in the formation of by-products with f…
Effect of the conversion of mangroves into shrimp farms on carbon stock in the sediment along the southern Red Sea coast, Saudi Arabia
2019
The conservation of coastal ecosystems and specially mangroves ‘‘blue carbon’’ is receiving more attention as consequence of their recognition as high ecosystem carbon stocks and for the fact that these areas are undergoing land conversion. The aim of the present study is to evaluate the impact of land use changes due to conversion of mangroves to shrimp farms on the bulk density (SBD), organic carbon (SOC) concentration, and SOC stock in the sediments along the southern Saudi Arabian Red Sea coast. Shrimp farms and mangrove locations showed significant (P < 0.001) differences in SBD with high mean values in the sediments of shrimp farms. Shrimp farms and mangrove locations showed significa…
CHARACTERISATION OF DISSOLVED ORGANIC CARBON (DOC) LEACHED FROM LEAVES IN WATER
2008
<p>Penelitian ini bertujuan untuk menentukan senyawa organik khususnya organic karbon terlarut (DOC) dari dua spesies daun tumbuhan (<em>wandoo eucalyptus </em>and <em>pinus radiate, conifer</em>) yang larut dalam air selama periode 5 bulan leaching eksperimen. Kecepatan melarutnya senyawa organic ditentukan secara kuantitatif dan kualitatif menggunakan kombinasi dari beberapa teknik diantaranya Total Organic Carbon (TOC) analyser, Ultraviolet-Visible (UV-VIS) spektrokopi dan pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS).</p><p>Hasil analisis DOC dan UV menunjukkan peningkatan yang tajam dari kelarutan senyawa organic di awal periode pen…