A. Van Put

Chemical composition of sediments, suspended matter, river water and ground water of the Nile (Aswan-Sohag traverse)

Sediment, suspended matter, river water and ground water samples were collected at twelve sites in the drainage valley of the Nile River, around Sohag (Central Egypt) and close to the Aswan High Dam. Elemental composition of the river water (27 elements), ground water (eight elements), suspended matter (12 elements) and sediments (12 elements) was studied. Aswan High Dam construction, agricultural and industrial human activities have led to dramatic changes in the Nile River chemistry. Nowadays, the Nile River has the highest dissolved salt content among the major African rivers. Dissolved transport is a major process for Ca, K, Sr, Zn, Cu, Ni and V. Manganese, Fe and Cr are mainly carried by suspended matter. The Nile suspended matter is exhausted in almost all elements studied (except for Mn) compared to the world average river suspended matter. Along the course of the river, the distribution of elements in the suspended matter and sediments is generally controlled by natural processes: the relative importance of elemental transport phases; and the oxidation, precipitation and sedimentation of mineral species through the varying physico-chemical conditions of the environment. Pollution input in the Nile particulate load is not major, as compared to the natural inputs. Eight genetic particle types describe the composition of the Nile suspended matter and sediments: (1) biogenous-aeolian (or silica); (2) terrigenous (Fe-aluminosilicate); (3) authigenic (calcium carbonate); (4) biogenous (apatite); (5) authigenous-terrigenous (Fe-oxyhydroxide-montmorillonite); (6) diagenetic (iron-sulfide); (7) terrigenous (titanium oxide); (8) authigenous (Mn-Fe-oxyhydroxide).

Suspended-matter particle size in some west-European estuaries; part I: Particle-size distribution

Abstract Particle size of suspended matter was measured in five Northwest-European estuaries by Coulter counter and pipette analysis, and in situ with a suspension camera. Particle sizes measured by Coulter counter and pipette analysis became finer at the saltwater contact, but the in situ particle (floc) sizes did not show this. It is concluded that the particle size measured by Coulter counter and pipette analysis indicates the fragility (or firmness) of the flocs. The in situ particle size is variable, and is not related to changes in salinity, the content of organic matter in the flocs or the bulk composition of the organic matter. There is no consistent evidence that salt flocculation is an important factor in river mouths.

Suspended-matter particle-size in some West-European estuaries : part II. A review on floc formation and break-up

Abstract The results of particle size measurements in several estuaries with a Coulter counter, by pipette analysis and with a Plankton camera that gives the in situ size are discussed. The in situ size distribution of flocs is probably the result of a complex interaction of processes that induce flocculation. In estuaries, the kinetics of the processes in relation to the tidal cycle are particularly important. There is no evidence for an influence of salinity on in situ floc size distributions. In situ flocs are smaller than the turbulent whirls and probably do not break up after their formation. The floc break-up that occurs during sampling and analysis is an indication of the firmness (strength) of the flocs. The salinity increase at the fresh-saline water contact reduces the floc strength by mobilizing natural polymers (polysaccharides).

Dispersal of suspended matter in Makasar Strait and the Flores Basin

Abstract In November 1984 in Makasar and the Flores Basin water samples were collected (T, S, dissolved O 2 , total CO 2 ), bottom samples (sediment composition) and suspended matter (particle composition, particle size). A sediment trap was moored in the Flores Basin at 4600 m depth for nearly four months, covering the dry season. In the Flores Basin there are indications for bottom flow resuspending bottom material or preventing suspended material from settling; in Makasar Strait there is probably inflow of deep water both from the south and from the north, resulting in a very slow bottom water flor. Bottom deposits in Makasar Strait and the Flores Basin are predominantly terrigenous, with an admixture of organic carbonate and silica (mostly coccoliths). Volcanic material is primarily present near to the volcanoes in the south and reaches the deeper basins by slumping. In the suspended matter no volcanic particles and little planktonic material were found, although the latter form 10 to 15% of the top sediment and of the material deposited in the sediment trap. In suspension particles with a large concentration of tin (Sn) were found associated mainly with iron. They probably come from northern Kalimantan or northern Sulawesi. Suspended matter concentrations were mainly less than 0.5 mg·dm −3 , only off the Mahakam river mouth were concentrations higher than 1 mg·dm −3 . Particle size was erratic because of the variable composition of the coarser particles in suspension. Organic matter concentrations in suspension (in mg·dm −3 ) roughly follow the distribution of total suspended matter but organic content (in %) of the suspended matter does not show any trends. All organic matter in suspension is of marine origin except in the Mahakam river and estuary. Deposition rates, as estimated from the sediment trap results, are 150 mg·cm −2 ·a −1 for the total sediment, 26 mg·cm −2 ·a −1 for carbonate and 13 mg·cm −2 ·a −1 for organic matter. Flocs and fibres in suspension were only found in and below the Mahakam river plume that reaches ca 400 km from the river mouth to the southeast, and in surface waters associated with plankton (diatoms). The formation of these flocs (broken-up macroflocs or marine snow) is primarily related to particle concentration, turbulence, and the presence of organisms that produce sticky material or glue particles together.

Single particle analysis of suspended matter in the Makasar Strait and Flores Sea with particular reference to tin-bearing particles

Abstract Suspended matter samples filtered from surface waters and two depth profiles from the Flores Sea and Makasar Strait were investigated by electron probe X-ray microanalysis (EPXMA) and laser microprobe mass analysis (LAMMA). EPXMA yielded discrete morphological and chemical analysis of the major particle types of suspended matter. Cluster analysis revealed that thirteen main particle types described the composition of suspended matter of the Flores Sea and Makasar Strait. Silicates, aluminosilicates and Fe-oxyhydroxides were the predominant particle types. Suspended matter of the basins studied contained high levels of tin-bearing particles. On the basis of their composition, tin particles can be divided into three groups: (1) tin oxide/hydroxides (cassiterite, romarchite, hydroromarchite); (2) iron-oxyhydroxides with adsorbed tin; and (3) mixed oxidation state tin hydroxysulphates. Only ultra-fine cassiterite particles enter the seawater in suspended state. Dissolved tin species entering the sea have three alternatives: (1) to be scavenged by Fe-oxyhydroxides; (2) to precipitate as tin oxide/hydroxides (romarchite, hydroromarchite); (3) to precipitate as tin hydroxysulphates. The conclusion is that dissolved and suspended tin originate from local sources in the land frame of the basins as well as from remote sources in the Indonesian Archipelago. Four different sectors of the waters studied have suspended matter with different composition: (1) the Mahakam River–Delta zone; (2) the open Flores Sea; (3) the landlocked Saleh Bay; (4) the Makasar Strait proper. The depth distribution of suspended particle types is mainly influenced by: (1) the bottom nepheloid layer and calcite lysocline in the Flores Sea; (2) the high bioproduction in the surface water layer and the vertical distribution of organic matter in the Makasar Strait.

Analytical study of the weathering of the Jeronimos Monastery in Lisbon

A variety of samples of the weathering crust and of rain runoff and washdown water were collected from the Jeronimos Monastery, Lisbon. Runoff and leaching samples were taken from upper walls, facing the north, the east and the west. For the crust samples, attention was focused on three points where the decay is more noticeable: the southern portal, the San Vicente portal and the cloister. The samples were analysed by different quantitative trace and micro-analytical techniques. The soluble fraction of the rain, runoff and leaching samples was analysed for major anions by ion chromatography. Multi-elemental analyses of the particles in suspension were carried out by energy-dispersive X-ray fluorescence spectrometry. Electron probe X-ray micro-analysis was applied to make line scans on petrographic sections across the weathered zone, and to analyse and classify individual suspended particles in samples of rain, runoff and washdown. A few thin sections have also been characterised petrographically and by X-ray diffraction analysis. The weathering crust is up to 400 μm thick and is enriched in S, K, Si, Fe and Mg. Large amounts of sulphate, and also phosphate and oxalate are detected in the runoff and leaching water. In the suspended fraction, high amounts of Fe and Ca are measured. The blank and rainwater samples have mainly Si-rich particles from quartz and feldspars in soil dust. The leaching and runoff samples are enriched in Ca-rich particles due to CaCO3 leached from the stone.

CHEMICAL CHARACTERISATION OF THE WEATHERING CRUST OF THE JERONIMOS MONASTERY

Summary Several samples of the weathering crust and of rain, runoff andwashdown water, taken at the Jeronimos monastery, Lisbon, Portugal were thoroughly analysed by different quantitative andmicroanalytical techniques. The soluble fraction of the rain, runoff and leaching samples was analysed for major anions by ionchromatography. Multi-elemental analyses of the particles insuspension were carried out by energy-dispersive X-ray fluorescencespectrometry. Electron probe X-ray micro-analysis was appliedto make line-scans on petrographical sections across the weatheredzone, surfaces of 1 by 1 1μm or 4 by 10 μm across being analysedone next to the other, and to analyse and classify individualsuspended particles in samples of rain, runoff and washdownsamples. The most important weathering product is sulfate, in the runoff and leaching samples as well as in the crustsamples. The crust also contains phosphate and oxalate. Thesuspensions of all the runoff, leaching and crust samples containa high amount of Fe and Ca. The blank and rainwater samples havemainly Si–rich particles from quartz and feldspars in soil dust.The leaching and runoff—samples are enriched in Ca–rich particlesdue to CaCO3leached from the stone.