scholarly journals Assessing the nonconservative fluvial fluxes of dissolved organic carbon in North America

2012 ◽  
Vol 117 (G1) ◽  
Author(s):  
Ronny Lauerwald ◽  
Jens Hartmann ◽  
Wolfgang Ludwig ◽  
Nils Moosdorf
Keyword(s):  
North America ◽  
Organic Carbon ◽  
Dissolved Organic Carbon

Water chemistry and dissolved organic carbon trends in lakes from Canada’s Atlantic Provinces: no recovery from acidification measured after 25 years of lake monitoring

2011 ◽  
Vol 68 (4) ◽  
pp. 663-674 ◽  
Author(s):  
Thomas A. Clair ◽  
Ian F. Dennis ◽  
Robert Vet
Keyword(s):  
North America ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Acid Deposition ◽  
Base Cations ◽  
Sampling Period ◽  
Lake Chemistry ◽  
Neutralization Capacity ◽  
Air Temperatures ◽  
Recovery From Acidification

We analyzed chemistry trends for 66 Atlantic Canada lakes using data collected from 1983 to 2007, as well as from 1990 to 2007 and 2000 to 2007 for the original 66 and a further 25 lakes that were later added to the network. Though receiving the lowest acid deposition in eastern North America, the region’s waters are seriously affected by acid rain because of poorly buffering soils and bedrock. Earlier work had shown that despite large decreases in sulfate deposition, lake pH and calculated acid neutralization capacity (ANCc) had not increased as they had elsewhere in North America and Europe. Despite a 50% decrease in acid deposition, a further 10 years of lake chemistry data showed a regional increase in ANCc only at the beginning of the sampling period but no increase since the early 1990s. There were also no increases in pH and base cations in the region’s lakes. We show a regional increase in Gran titration ANC (ANCG) from 2000 to the present, which we ascribe to increases in dissolved organic carbon that is probably due to a regional increase in annual air temperatures.

scholarly journals Ionic aluminium concentrations exceed thresholds for aquatic health in Nova Scotian rivers, even during conditions of high dissolved organic carbon and low flow

2020 ◽  
Vol 24 (10) ◽  
pp. 4763-4775 ◽  
Author(s):  
Shannon M. Sterling ◽  
Sarah MacLeod ◽  
Lobke Rotteveel ◽  
Kristin Hart ◽  
Thomas A. Clair ◽  
...  
Keyword(s):  
Nova Scotia ◽  
North America ◽  
Organic Carbon ◽  
Atlantic Salmon ◽  
Dissolved Organic Carbon ◽  
Acid Deposition ◽  
Linear Mixed Model ◽  
Aquatic Organisms ◽  
Base Flow ◽  
Low Flow

Abstract. Acid deposition released large amounts of aluminium into streams and lakes during the last century in northern Europe and eastern North America. Elevated aluminium concentrations caused major environmental concern due to aluminium's toxicity to terrestrial and aquatic organisms and led to the extirpation of wild Atlantic salmon populations. Air pollution reduction legislation that began in the 1990s in North America and Europe successfully reduced acid deposition, and the aluminium problem was widely considered solved. However, accumulating evidence indicates that freshwater systems still show delays in recovery from acidification, with poorly understood implications for aluminium concentrations. Here, we investigate spatial and temporal patterns of labile cationic forms of aluminium (Ali) from 2015 to 2018 in 10 catchments in Nova Scotia, Canada; this region was one of the hardest hit by acid deposition, although it was not considered to have an aluminium problem due to its high dissolved organic carbon (DOC) concentrations that were expected to reduce Ali concentrations. Surprisingly, our results show the widespread and frequent occurrences of Ali concentrations that exceed toxic thresholds in all sampled rivers despite high DOC concentrations. Generalized linear mixed model results reveal that DOC, instead of being inversely related to Ali, is the strongest predictor (positive) of Ali concentrations, suggesting that the recruitment properties of DOC in soils outweigh its protective properties in streams. Lastly, we find that, contrary to the common conceptualization that high Ali levels are associated with storm flow, high Ali concentrations are found during base flow. Our results demonstrate that elevated Ali concentrations in Nova Scotia continue to pose a threat to aquatic organisms, such as the biologically, economically, and culturally significant Atlantic salmon (Salmo salar).

scholarly journals Aspen Soils Retain More Dissolved Organic Carbon Than Conifer Soils in a Sorption Experiment

2020 ◽  
Vol 3 ◽  
Author(s):  
Antra Boča ◽  
Astrid R. Jacobson ◽  
Helga Van Miegroet
Keyword(s):  
North America ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Tree Species ◽  
Mineral Soil ◽  
Null Point ◽  
Conifer Forest ◽  
Sorption Experiment ◽  
Subalpine Fir ◽  
Doc Concentration

The effect tree species have on soil organic carbon (SOC) has been hotly debated but, so far, few clear patterns have emerged. One example of a differing tree species effect on SOC are aspen forests in North America, which have been found to have more stable SOC than adjacent conifer forest stands. An important source for the formation of stable organo-mineral complexes in soil is dissolved organic carbon (DOC). DOC concentrations in mineral soil are often higher under the thick O-horizons of conifer forests than under aspen forests, but this does not correspond to more stable mineral SOC. This suggests that, instead of DOC concentration, DOC quality could be driving the observed differences in SOC. Therefore, we quantified the retention of contrasting forest detritus DOC in soils. Using a batch sorption experiment approach, we compared the retention of detritus leachates from four sources – aspen leaves (AL), aspen roots (AR), conifer (subalpine fir) needles (CN), and conifer (subalpine fir) roots (CR) – on soils sampled under aspen and conifer (subalpine fir and Douglas fir) overstories. The calculated sorption isotherms showed a higher retention of AL DOC than AR DOC, as indicated by all four sorption parameters – k and n (curve-fitting parameters), null point concentration (NPC; net sorption = net desorption), and endpoint (EP, retention at the highest initial DOC concentration). Leachates from CN and CR showed very similar retention behavior, and between the two species the retention of root leachates was more similar than the retention of foliage leachates. Soils sampled from aspen forests showed higher affinity for new DOC than conifer soils [higher sorption rate (n), lower NPC, and higher EP] regardless of the DOC source. The findings suggest that the higher DOC sorption on aspen soils might be a major driver for more stable SOC under aspen stands in North America.

Dissolved organic carbon reconstructions from diatom assemblages in PIRLA project lakes, North America

1990 ◽  
Vol 327 (1240) ◽  
pp. 279-288 ◽  
Keyword(s):  
Maximum Likelihood ◽  
North America ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Weighted Averaging ◽  
Data Sets ◽  
Regional Data ◽  
Diatom Assemblages ◽  
The North ◽  
Good Agreement

Diatom-based palaeolimnological reconstructions of dissolved organic carbon (DOC) are presented for four regional data sets of the North American ‘Paleoecological Investigation of Recent Lake Acidification (PIRLA)’ project, and for a combined, three-region set. Species optima and tolerances along the DOC gradient were estimated by using maximum likelihood and weighted-averaging regression. Weighted-averaging regression appears to be the most robust and tractable technique for estimating optima, and the apparent error (mean standard error of the relation) was as good for weighted-averaging calibration as for maximum likelihood calibration. Calculated species optima are not entirely consistent among regions and the best ‘indicators’ for DOC in the PIRLA data-sets are not in good agreement with those found in the literature. Example reconstructions demonstrate that DOC changes are often less than 100 µmol l -1 , and that the DOC declines in some recently acidified lakes parallel reconstructed pH declines.

scholarly journals Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America

2013 ◽  
Vol 27 (2) ◽  
pp. 492-504 ◽  
Author(s):  
Kevin W. Hanley ◽  
Wilfred M. Wollheim ◽  
Joseph Salisbury ◽  
Thomas Huntington ◽  
George Aiken
Keyword(s):  
North America ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Chemical Character

CHARACTERISATION OF DISSOLVED ORGANIC CARBON (DOC) LEACHED FROM LEAVES IN WATER

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Markus Heryanto Langsa
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Total Organic Carbon ◽  
Gas Chromatography Mass Spectrometry ◽  
Pyrolysis Gas ◽  
Pyrolysis Gas Chromatography ◽  
Chromatography Mass Spectrometry ◽  
Pinus Radiate

<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 pengamatan yang selanjutnya berkurang seiring dengan waktu secara eksponensial. Jumlah relatif senyawa organic yang terlarut tergantung pada luas permukaan, aktifitas mikrobiologi dan jenis sampel tumbuhan (segar atau kering) yang digunakan. Fluktuasi profil DOC dan UV<sub>254</sub> disebabkan oleh aktifitas mikrobiologi. Diperoleh bahwa daun kering lebih mudah terdegradasi menghasilkan senyawa organic dalam air dibandingkan dengan daun segar. Hasil pyrolysis secara umum menunjukkan bahwa senyawa hidrokarbon aromatic dan fenol (dan turunannya) lebih banyak ditemukan pada residue sampel setelah proses leaching kemungkinan karena adanya senyawa lignin atau aktifitas humifikasi mikrobiologi membuktikan bahwa senyawa-senyawa tersebut merupakan komponen penting dalam proses karakterisasi DOC.</p>

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