The determination of suspended metals in coastal waters by different sampling and processing techniques (filtration, centrifugation)

doi:10.1016/0077-7579(79)90007-3

Netherlands Journal of Sea Research

Volume 13, Issue 2, November 1979, Pages 282-297

https://doi.org/10.1016/0077-7579(79)90007-3 Get rights and content

Abstract

The concentrations, on a sediment weight basis, of several metals in coastal suspended matter show a marked dependence on the amount of particulate matter per litre. The effects of filtration and centrifugation are compared. The resulting data are interpreted in terms of varying contributions of larger and denser bottom derived particles with higher concentrations of K, Fe, Mn, and Al and of smaller and less dense, continuously suspended particles with higher concentrations of Cu, Cd, Pb and Zn. No dependence on size or density was found for Cr, Si, Mg and Ca.

Filtration results in higher concentrations of Cu, Cd, Pb, and Zn. For the other elements, centrifugation results in concentrations that are at least similar to those in particulates obtained by filtration, or even larger for elements with relatively large difference between the concentrations in the different fractions, such as K. Leaching particulates, obtained by filtration and centrifugation, with 0.1 N HCl leads to differences in the leached fractions for Cd, Cr, K and Mg at lower suspended loads, and for Fe at higher loads, while no differences are observed for Cu, Pb, Zn, Si, Mn, Al and Ca.

Accurate particulate metal concentration data were obtained by measuring in each individual sample, the amount of both metal and particulate matter. This results in more accurate data than can be obtained by measuring each of the properties in separate samples. Another source of errors is eliminated by analyzing the entire content of a sampler in stead of part of it, because of sample inhomogeneity introduced by settling of particles in the sampler.

In order to get accurate sediment weight data at low suspended matter concentrations, sea salt was removed from the particulate matter by a rinsing procedure with distilled water. No loss of the metals investigated (Cu, Cd, Zn, Cr, Si, Fe, Mn, and Al) was evident with a possible exception for Cd.

References (4)

J.C. Duinker et al.
On the behaviour of copper, zinc, iron and manganese and evidence for mobilization processes in the Dutch Wadden Sea
Neth. J. Sea Res.
(1974)
J.D. Burton
Basic properties and processes in estuarine chemistry

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Sampling of suspended particulate matter using particle traps in the Rhône River: Relevance and representativeness for the monitoring of contaminants
2018, Science of the Total Environment
Citation Excerpt :
Suspended particulate matter sampling is preferred to bed material sampling as particle deposition is often spatially heterogeneous and includes bed materials. Various sampling techniques can be used to collect SPM including direct water sampling (manual grab sampling or use of automatic samplers) followed by filtration (Duinker et al., 1979; Mahler and Van Metre, 2003) or settling (Etcheber and Jouanneau, 1980), in-line filtration (Horowitz, 1986), continuous flow centrifugation (CFC; Burrus et al., 1989; Rees et al., 1991; Schäfer and Blanc, 2002) or the deployment of particle traps (PT; Gardner, 1980; Phillips et al., 2000; Pohlert et al., 2011). Under usual SPM concentrations in rivers (1–100 mg L−1 typically), direct water sampling requires collecting too huge volumes of water, in order to provide enough material (>2 g dry weight, d.w.) for the analysis of a set of elements and contaminants including major parameters, metals, organic contaminants and radioelements.
Monitoring hydrophobic contaminants in surface freshwaters requires measuring contaminant concentrations in the particulate fraction (sediment or suspended particulate matter, SPM) of the water column. Particle traps (PTs) have been recently developed to sample SPM as cost-efficient, easy to operate and time-integrative tools. But the representativeness of SPM collected with PTs is not fully understood, notably in terms of grain size distribution and particulate organic carbon (POC) content, which could both skew particulate contaminant concentrations. The aim of this study was to evaluate the representativeness of SPM characteristics (i.e. grain size distribution and POC content) and associated contaminants (i.e. polychlorinated biphenyls, PCBs; mercury, Hg) in samples collected in a large river using PTs for differing hydrological conditions. Samples collected using PTs (n = 74) were compared with samples collected during the same time period by continuous flow centrifugation (CFC).
The grain size distribution of PT samples shifted with increasing water discharge: the proportion of very fine silts (2–6 μm) decreased while that of coarse silts (27–74 μm) increased. Regardless of water discharge, POC contents were different likely due to integration by PT of high POC-content phytoplankton blooms or low POC-content flood events. Differences in PCBs and Hg concentrations were usually within the range of analytical uncertainties and could not be related to grain size or POC content shifts. Occasional Hg-enriched inputs may have led to higher Hg concentrations in a few PT samples (n = 4) which highlights the time-integrative capacity of the PTs. The differences of annual Hg and PCB fluxes calculated either from PT samples or CFC samples were generally below 20%. Despite some inherent limitations (e.g. grain size distribution bias), our findings suggest that PT sampling is a valuable technique to assess reliable spatial and temporal trends of particulate contaminants such as PCBs and Hg within a river monitoring network.
Forms of phosphorus in suspended particulate matter in agriculture-dominated lowland catchments: Iron as phosphorus carrier
2018, Science of the Total Environment
Citation Excerpt :
This was due to lower contents from all PP fractions other than the Fe-P pool (Table 3). From literature is it known that the recovery efficiency of centrifugation samples is generally lower than that of filtration samples (Duinker et al., 1979; Horowitz et al., 1989; Van Eck, 1982), largely because the finer and less dense particles may not be included in particulate matter obtained by centrifugation (Duinker et al., 1979). Van Eck (1982) reported the recovery efficiency of a continuous-flow centrifugation was 85–95% of 0.45 μm filtration.
The fate and environmental effects of phosphorus (P) in natural waters depend on its chemical forms. The particulate P (PP) concentration is dominant over the dissolved P concentration in agriculture-dominated headwaters in the Netherlands. Routine water quality monitoring programmes do not include the chemical fractionation of PP. To quantify the chemical forms of PP under various conditions in six agriculture-dominated lowland catchments in the Netherlands, a sequential chemical extraction method was applied to suspended particulate matter (SPM) samples collected by centrifugation or filtration. Centrifuge samples had lower values for the sum of the PP fractions compared with the filtration samples due to lower contents from PP fractions other than the Fe-P pool. With an average value of 8.8 mg g⁻¹, internationally high P contents of the SPM were found. Ferric iron-bound P was the most important PP fraction in SPM samples (38–95%; median 74%), followed by organic P (2–38%; median 15%). Exchangeable P ranged from 0.2 to 27%, with a median of 4.4%, Ca-P ranged from 0.1 to 11% with a median of 3.9% and detrital P was present in only a small fraction (0–6%; median 1.1%). Ferric iron-bound P was the dominant PP pool throughout the entire range of watercourses (from headwater ditches to catchment outlets) and in samples taken during winter months as well as those taken during summer months. Furthermore, the PP fraction distribution did not change markedly when flow conditions were altered from low to high discharge. The dominance of the Fe-P pool denotes the presence of Fe(III) precipitates in SPM that originate from exfiltration of anoxic Fe-bearing groundwater. These Fe(III) precipitates are a major fraction of the total SPM concentration (4 to 67% as Fe(OH)₃; median 18%). Although not measured directly, our results suggest that formation of authigenic Fe(III) precipitates causes a rapid transformation of dissolved P in groundwater to PP in surface water. We advise including sequential chemical extraction of SPM monitoring programmes because the composition of particles is critical for P bioavailability, which is a key driving factor for eutrophication.
Chemical contaminants in the Wadden Sea: Sources, transport, fate and effects
2013, Journal of Sea Research
Citation Excerpt :
They expressed their concentrations in relation to the whole sediment. As a result, little information was given on the geological origin of various metals in the sediments, as the fraction of small particles varies and most contaminants have great affinity for the smaller particles (e.g., silt and clay) and less or none for sand (Duinker et al., 1974; Duinker et al., 1979; Förstner et al., 1982; Salomons and Eysink, 1983; Salomons and Förstner, 1984). It became clear that in order to study the temporal and spatial characteristics of contaminants in sediments properly, the contaminant concentrations should be expressed in a certain fraction of the sediments, i.e., standardized.
The Wadden Sea receives contaminants from various sources and via various transport routes. The contaminants described in this overview are various metals (Cd, Cu, Hg, Pb and Zn) and various organic contaminants (polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and lindane (hexachlorocyclohexane, γ-HCH)). In addition, information is presented about other and emerging contaminants such as antifouling biocides (e.g. TBT and Irgarol), brominated flame retardants (BFRs), poly- and perfluorinated compounds (PFCs) and pharmaceutical and personal care products (PPCPs).
Special attention is given to biogeochemical processes that contribute to the mobilization of contaminants in the surface sediments of the Wadden Sea. Finally, the effects on organisms of contaminants are reviewed and discussed.
The main source of contaminants in the Wadden Sea are the rivers Rhine (via de Dutch coastal zone), Elbe and Weser. The Wadden Sea is not a sink for contaminants and adsorbed contaminants are transported from east to west. The surface sediments of the Wadden Sea are an important source for contaminants to the water above. The input and concentration of most contaminants have significantly decreased in water, sediments, organisms (e.g., mussel, flounder and bird eggs) in various parts of the Wadden Sea in the last three decades. Remarkably, the Cd concentration in mussels is increasing the last decades.
In recent decades, the effects of contaminants on organisms (e.g., flounder, seal) have fallen markedly. Most of the affected populations have recovered, except for TBT induced effects in snails. Little is known about the concentration and effects of most emerging contaminants and the complex environmental mixtures of contaminants.
It is recommended to install an international coordinated monitoring programme for contaminants and their effects in the whole Wadden Sea and to identify the chemical contaminants that really cause the effect.
Relationship between ore deposits in river catchments and geochemistry of suspended particulate matter from six rivers in southwest France
2002, Science of the Total Environment
Here we present original data on the geochemical composition of fluvial particulate matter transported by the rivers of the Adour/Garonne basin, which drains one-fifth of the French land surface. Suspended particulate matter from the six main rivers in the basin, sampled at ‘normal’ flow and during a flood, is compared in terms of: grain size; particulate organic carbon; Fe; Mn; and trace element concentrations (e.g. Zn, Cd, Pb, Cu, Mo, Sn, Ni, Co, Cr, V, As, Hg, U, Th, W, Au, Ag, Ta). Three of the six studied rivers (Garonne, Dordogne and Isle Rivers) are the main tributaries of the Gironde estuary (southwest France), known for Cd pollution. The Adour and Gaves Rivers enter the Adour Estuary and the Charente River reaches the ocean by the Charente Estuary. Our data show, that Cd (and Zn) are not the only trace elements of eco-toxicological relevance transported into the Gulf of Biscay by these six rivers. Potentially toxic elements (e.g. As, Sn, U, Cu, Ag) show elevated concentrations in river particulates entering the estuaries, compared to world average concentrations [Martin and Whitfield, 1983, The significance of the river input of chemical elements to the oceans. In: C.S. Wong, E. Boyle, K.W. Bruland, J.D. Burton, E.D. Goldberg (editors), Trace Metals in Sea Water, Plenum, New York: pp. 265–296]. Comparing SPM sampled during ‘normal’ discharge and flood, the basin shows a distinct trace element composition of SPM mostly related to ore deposits in the upper basins (Massif Central and Pyreneans). This geochemical signal is partly masked during floods due to changes in grain size, but also due to increased erosion of the lower parts of the basins. This study proves pumping/centrifugation to be the most appropriate sampling/separation technique (recovery, representativity, contamination) by comparing different methods of SPM recovery.
Contrasting behaviour of trace metals in the Scheldt estuary in 1978 compared to recent years
1999, Journal of Sea Research
Dissolved and particulate trace metals (Cu, Cd, Pb, Zn, Ni, Fe and Mn) measured at six stations along the Scheldt estuary in October/November 1978 are compared with more recent data. Based on Ca content in the suspended matter, three distinct geochemical regions could be distinguished: the upper estuary (salinity 1–7) dominated by fluvial mud, mid-estuary (salinity 7–17) where the composition of the suspended matter remained relatively constant, and the lower estuary where marine mud prevailed. Re-suspension of sediments is the major factor controlling the composition of the particles in the upstream region. Anoxic conditions prevailed in the upper part of the estuary extending to a salinity of 15 in 1978, while at present the seaward boundary of the anoxic water body is located at less saline waters. Furthermore, the present-day metal load is much lower than in 1978. As a consequence of the changed situation, maxima in dissolved concentrations of redox-sensitive metals in the mid/lower estuary have moved as well, which affects the trace metal re-distribution pattern. In the anoxic zone, exchange processes between dissolved and particulate metal fractions were strongly redox regulated, with Fe and Mn as excellent examples. Iron was removed from the dissolved phase in the early stages of mixing resulting in an increase in the suspended particulate matter of the leachable `non-residual' Fe fraction from 2 to 3.5%. Due to its slower kinetics, removal of Mn from solution occurred in mid-estuary where oxygen concentrations increased. Cu, Cd and Zn on the contrary were mobilised from the suspended particles during estuarine mixing. External inputs of Pb, and to a lesser extent of Cu, in the lower estuary resulted in the increase of their particulate and the dissolved concentrations. Calculated K_d (distribution coefficient) values were used to assess the redistribution between the dissolved and particulate phase of the investigated metals. Due to the existence of the anoxic water body in the upper estuary, the importance of redox processes in determining the K_d values could be demonstrated. The sequence of K_d values in the upper estuary (Fe, Cd, Zn, Pb > Cu > Ni, Mn) is significantly different from that in the lower estuary (Fe > Mn > Pb, Ni, Zn, Cu, Cd). Thus, in such a dynamic estuary single metal-specific K_d values cannot be used to describe redistribution processes.
What about quality assurance before the laboratory analysis?
1994, Marine Pollution Bulletin
Nowadays, intercalibrations, availability of certified reference materials (CRMs), clean room techniques, etc., have resulted in a situation where many laboratories seem to provide acceptable data for nutrients, trace metals and/or organic micro-pollutants, whether analysed in water, sediment or biota. There is a tendency that, provided certain measures have been taken within the laboratory, everything seems to be under control.
Unfortunately, laboratory performance has, so far, only been tested through the analysis of well defined samples, provided from outside the laboratory (for example, by the organization of an intercalibration exercise, the use of CRMs).
It should be realized, however, that sampling, sample pre-treatment, transport and storage, are an integral part of the analysis. These sample handling procedures have not received much attention in terms of quality assurance (QA) and good measuring practice (GMP).
It is recommended that attention is focused not only on the laboratory analysis but on developing/including QA and GMP/GLP procedures for that part of the analysis that relates to the samples before they reach the (clean) laboratory.

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The determination of suspended metals in coastal waters by different sampling and processing techniques (filtration, centrifugation)

Abstract

Neth. J. Sea Res.

Basic properties and processes in estuarine chemistry