R. L. Thomas

GNS Science

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A.L.W. Kemp

GDG Environnement

Jean-Pierre Vernet

Iscte – Instituto Universitário de Lisboa

P. G. Sly

Children's Medical Research Institute

Janusz Dominik

Institute of Marine Science

J.‐M. Jaquet

University of Geneva

Bernard Pelletier

Institut de Recherche pour le Développement

Michel Pardos

Forel Klinik

D. Burrus

Innovative Scientific Solutions (United States)

Christophe Benninghoff

University of Geneva

Sérgio Lima Santiago

Universidade Federal do Ceará

Cooperative Institutions

University of Geneva

Forel Klinik

Environment and Climate Change Canada

GNS Science

University of Guelph

National Water Research Institute

Ministry of Agriculture, Food and Rural Affairs

United States Geological Survey

Agriculture and Agri-Food Canada

Université Laval

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Nitrogen and C/N ratios in the sediments of Lakes Superior, Huron, St. Clair, Erie, and Ontario

Canadian Journal of Earth Sciences (1977)

A.L.W. Kemp R. L. Thomas Henry K. Wong L. M. Johnston

The distribution of nitrogen (N) was determined on 1238 surface sediment samples (0–3 cm) and 24 cores from Lakes Superior, Huron, St. Clair, Erie, and Ontario. The concentration of N was greatest in the depositional basins of the lakes. The N concentrations decreased sharply from high values at the sediment–water interface to uniformly lower N values at the base of the cores. The surface enrichment was related to increased inputs of N to the lakes since settlement of the region in the order: Lake Ontario > Lake Erie [Formula: see text] Lake Superior > Lake Huron > Georgian Bay.The organic carbon: total nitrogen (C/N) ratios averaged 10.2 in the surface sediments with a range of 5.1 to 66.0. The lowest ratios were found in the depositional basins, with the exception of Lake St. Clair. The magnitude of the C/N ratios was related to the source of the organic matter. Plankton, which are the main source of Org-N in the lakes, accounted for C/N ratios between 7 and 9. Dilution of the modern sediment with organic matter from glacial deposits yielded the higher ratios and low Org-C contents in the nondepositional zones. The high C/N ratios and Org-C contents in Lake St. Clair were believed to be due to a large component of macrophytes in the inputs of organic matter to the lake sediments.

10.1139/e77-205

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Citations (35)

Availability to Scenedesmus quadricauda of different forms of phosphorus in sedimentary materials from the Great Lakes1

Limnology and Oceanography (1980)

Jake Williams Harvey Shear R. L. Thomas

Sedimentary materials from eroding bluffs, suspended solids in streams, and lake bottom sediments from Lakes Ontario and Erie were cultured with the alga Scenedesmus quadricauda (Turp.) de Brébisson in modified Rodhe’s medium with the sediments as the sole source of P. P uptake by the algae was related to the amount of nonapatite inorganic phosphorus in the sediments. Apatite phosphorus was not used, and the bluff samples, in which over 90% of total P was in this form, did not support algal growth. The nonapatite inorganic P fraction was highly correlated with the amounts of inorganic phosphorus extracted by three standard techniques for estimating “available P” (extraction by NaOH and nitrilotriacetic acid solutions and by H‐resin) and cell uptake equaled NaOH‐extractable inorganic P in several instances. Uptake of P by the cells varied from 8 to 50% of total P and from 38 to 83% of nonapatite inorganic P when measured directly. Organic phosphorus in the sediments was not utilized by the algae. Percentage utilization of total P was in general highest when total P concentration in the sediments was itself high.

Scenedesmus

10.4319/lo.1980.25.1.0001

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Citations (209)

Recovery and concentration of suspended solids in the upper rhone river by continuous flow centrifugation

Hydrological Processes (1989)

D. Burrus R. L. Thomas Janusz Dominik Jean-Pierre Vernet

Abstract Six stations along the Rhône River from the Rhône Glacier to Lake Geneva were sampled by continuous flow centrifuge for recovery of suspended sediment. The samples were taken four times in the year in both 1982 and 1983. In addition, the mouth of the river was sampled in a like manner every two weeks during 1982 until August 1983. Concentration of sediment and composition did not vary as a function of depth or location across the river. Concentrations varied in time and as a function of flow and samples showed both increasing concentration in suspension and an increase in the proportion of finer particles moving downstream from source to mouth. Only slight variations in texture could be observed down the river as a function of time and appeared to relate to freezing and melting of the Rhône and other headwater glaciers as the primary sediment source. Little variation was observed annually in the texture and composition of the sediment at the river mouth despite large changes in concentration between the high flow summer and low flow winter discharges. These findings are consistent with a well‐mixed system in which the suspended sediments are directly related to the primary supply of material from the glaciers.

River mouth

Sedimentation

Centrifuge

Suspension

10.1002/hyp.3360030107

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Citations (41)

DETERMINATION OF Na-DITHIONITE AND NH₄-OXALATE EXTRACTABLE Fe, Al AND Mn IN SOILS BY ATOMIC ABSORPTION SPECTROSCOPY

Canadian Journal of Soil Science (1969)

A. T. Raad R. Protz R. L. Thomas

Fe, Al and Mn in distilled warer, NH 4 -oxaIate, and Na-dithionite solutions were determined by atomic absorption spectroscopy. Concentration ranges for sensitive absorption by Fe, Al, and Mn were 2.5 to 20, 25 to 125 and 2 to 10 ppm, respectively. Concentration ranges of extracting solutions for the determination of Fe, Al and Mn were 0.01 M, 0.20 M and 0.04 M, respectively. Accurate and rapid determinations of Fe, Al, and Mn in NH 4 -oxalate and Na-dithionite solutions are obtained by atomic absorption spectroscopy without the destruction of the organic extractants.

Dithionite

Sodium dithionite

10.4141/cjss69-010

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Citations (16)

Impact of man's activities on the chemical composition of the sediments of lakes superior and Huron

Water Air & Soil Pollution (1978)

A.L.W. Kemp J. D. H. Williams R. L. Thomas M.L. Gregory

Sedimentation

Trace element

10.1007/bf00250005

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Citations (158)

The Distribution of Mercury in the Sediments of Lake Ontario

Canadian Journal of Earth Sciences (1972)

R. L. Thomas

Total mercury has been analysed in the surface 3 cm of sediment taken from 287 sample stations on an 8 km grid on Lake Ontario during 1968. The mercury distribution shows well-defined trends which can be related to sediment type; the concentration of mercury increasing from the shallow nearshore coarse sediments outwards, into the central, deep-water basin sediments composed of fine silty clays and clays. The average concentration of mercury in the nearshore sediments is 355 ppb, in the basin sediments 997 ppb and the average for the whole lake is 651 ppb. Regions of high mercury concentration (in the order of 2000 ppb) occur along the southern margin of the main lake basin and in the western (Niagara) basin of the lake. The dispersion pathways of these two regions point to the Niagara River as the prime source of mercury input to Lake Ontario. Most of this mercury is believed to be of industrial origin. An additional area of high mercury concentration with values up to 20 000 ppb, occurs at the eastern end of Lake Ontario (Kingston Basin) in the region of the lake close to the outlet to the St. Lawrence River. These high values in organic-rich, fine sediments are likely related to processes of biological concentration. The concentrations of mercury observed in the recent sediments of Lake Ontario can be accounted for by an average minimum daily input of 125 lb (56.7 kg) of mercury of which an estimated 42 lb (19.0 kg) is of natural origin and the remaining 83 lb (37.6 kg) is from industrial sources. The vertical distribution of mercury in a selected sediment core suggests that industrial mercury input commenced about the turn of the century, rose rapidly to circa 1943 and, since then, has shown a slow but continued rise to the time of core retrieval in 1970.

Mercury

10.1139/e72-054

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Citations (160)

AGCL, a FORTRAN IV program for agglomerative, nonhierarchical Q-mode classification of large data sets

Computers & Geosciences (1977)

R. Froidevaux J.‐M. Jaquet R. L. Thomas

Fortran

Hierarchical clustering

Classification scheme

Computer program

Mode (computer interface)