Sequential Chemical Extraction Procedure Research Articles

Localization of copper accumulated in Rhynchostegium riparioides using sequential chemical extraction

A sequential chemical extraction procedure has enabled three fractions to be distinguished within the total copper (Cu) accumulated by the aquatic moss Rhynchostegium riparioides. These are (1) an intercellular fraction (Cu int) located in the free-water space of the cell wall, (2) an exchangeable fraction (Cu exch) which corresponds to metal trapped by exchange sites of the cell wall, and (3) a residual fraction (Cu res) located within the cell itself. The procedure applied to this aquatic moss exposed to Cu under laboratory conditions showed the total Cu content of the moss at the end of the 21-day uptake phase to be 725 μg g −1. Fourteen percent of this was contributed by the Cu res fraction, 47% by the Cu int fraction and 39% by the Cu exch fraction. At the end of the depuration phase, with a total Cu content in the moss of 293 μg g −1, the relative contribution of Cu res reached 23% because the depuration of Cu concerned primarily the Cu exch and, to a lesser extent, the Cu int fractions. The fraction of the accumulated Cu that is not readily desorbed can be assumed to have penetrated the cytoplasm.

Effects of thermal and acid treatment on the distribution of heavy metals in sewage sludge

Anaerobically treated sludge from a wastewater treatment plant (Psittalia) was found to contain significant amounts of metals (Cr, Cu, Fe, Ni, Pb and Zn). The sludge samples were subjected to thermal drying at 105°C and acid treatment was applied before and after thermal drying. Different acid concentrations and contact times were used in order to find the combination that caused the highest metal removal. The metal distribution in raw sewage and in thermally dried sludge as well as the chemical forms of the remaining metal load after acid treatment were determined by the application of a sequential chemical extraction procedure. It was found that thermal drying causes a shift of the metal content to more stable phases. A sufficient metal amount was removed by acid treatment and the remaining metal content was further stabilized.

Accumulation of Contaminant Metals in the Amphipod Diporeia spp. in Western Lake Ontario

Sediment and amphipods ( Diporeia spp.) were collected in areas in western Lake Ontario suspected of containing a range of sediment metal contents. The total metal contents (Al, As, Cd, Cr, Cu, Ni, Fe, V, and Zn) of depurated Diporeia tissues were measured and compared to the total metal contents of the surrounding sediment. The fractional bioavailability of As, Cu, Fe, and Zn was determined in those same sediments using a sequential chemical extraction (SCE) procedure and correlated with depurated Diporeia tissue metal contents. Results of these analyses were then used to assess the ability of Diporeia to accumulate sediment metal contamination. A comparison of metal biota-sediment accumulation factors (BSAFs) and sediment metal enrichment factors (EFs) for each metal yielded separate metal groups showing different behavior for tissue accumulation. Aluminum, Cr, Fe, Ni, and V were not enriched in the sediments and were not accumulated in Diporeia tissues, while As, Cd, Cu, and Zn were enriched in the sediments and accumulated in Diporeia tissues. SCE results showed that Cu (3.2 to 8.4 %) and Zn (13 to 19 %) contents in the easily extractable sediment fractions (MgCl 2 and Na-acetate) were significantly correlated with Cu (r = 0.86; P<0.01) and Zn (r = 0.69; P<0.05) contents in depurated Diporeia tissue. In addition, Cu and Zn in Diporeia tissues are also correlated to the total sediment metal content for each respective metal (Cu: r = 0.67, P < 0.05; Zn: r = 0.66, P < 0.05). The high BSAFs for Cu and Zn, in combination with the association of tissue metal contents with easily extracted sediment metal fractions, suggest that Diporeia may be a potential bioindicator for Cu and Zn contamination in sediments.

Bioavailability of arsenic in soil and mine wastes of the Tamar valley, SW England

ABSTRACTThe southern part of the Tamar valley area in SW England is highly mineralised and mines in the region were the world's principal producers of tin, copper and arsenic during the mid nineteenth century. The Devon Great Consols Mine, covering 67.6 ha (167 acres) is situated in this area. Residues from the mining activity resulted in unvegetated spoil tips and local soils highly contaminated with As (range 120–52600 μg/g As). Sequential chemical extraction procedures were conducted on eight surface samples (0–15 cm) taken from a 2.0 km long transect from within the mine site to agricultural grassland. The proportion of water extractable As in agricultural top soils was lower (0.05–0.3%) than the values obtained for mine wastes (0.02–1.2%). Arsenic was found to be concentrated in the Fe-organic and residual fractions, which accounted for up 93 % of the total As in mine spoil and nearby soils.

Mineralogy and geochemistry of Terra Rossa soils, western Sicily: insights into heavy metal fractionation and mobility

The distribution of heavy metals in typical Terra Rossa soils and their partitioning in specific soil phases are estimated on the basis of the comparative evaluation of bulk contents, results from sequential chemical extraction procedure (SEP) and scanning electron microscopy/energy dispersive X-ray analysis (SEMEDX). A general natural enrichment of heavy metals with respect to average soil is observed. Cadmium proves to be remarkably high (up to 2.4 ppm). Large amounts of Fe, Cr, Cu, Ni, Pb, and Zn occur in the ‘residual’ fraction. The results indicate selective accumulation of the heavy metals in Fe oxides, present as hematite, goethite and maghemite. There is good evidence that Mn and Cd are subjected to similar influences, both elements mainly occurring in the ‘easily reducible’ fraction. The affinity of Cd for poorly crystallized Mn oxides governs its behaviour and mobility, which may significantly increase in moderate reducing conditions in relation to Mn phases stability.

Transport of Anthropogenic Uranium from Sediments to Surface Waters During Episodic Storm Events

AbstractRemobilization of sediment‐associated uranium (U) from contaminated floodplain sediments to a stream adjacent to a nuclear weapons processing facility during episodic rain events was investigated. In addition, U solid phase associations in suspended sediments were assessed by a sequential chemical extraction procedure to gauge U chemical lability. Mass flux estimates determined from base flow measurements potentially underestimate the amount of U transported from contaminated terrestrial sources to surface water systems. Erosional processes can effectively mobilize sediment‐associated contaminants during storms or flooding. During the various storm events measured, approximately 1500 to 2800% more U was exported to Upper Three Runs Creek (UTRC) relative to base flow measurements. Sequential extraction results suggest the suspended sediment load transports the bulk of U in labile forms predominantly as acid soluble (specifically adsorbed), MnO2 occluded and organically bound phases. This implies that U may be available to the ecosystem under a range of environmental conditions likely to be encountered within depositional environments (e.g., Eh and pH) or as a result of industrial processes. This study demonstrates the need to evaluate contaminant transport during storm events from exposed contaminated sediments, or from industrial waste stockpiles subject to erosion.

Geochemical phases of metals in Hudson River estuary sediments

Bottom sediment samples were collected from six locations along a section of the Hudson River Estuary, 5.3 to 82.7 km from the ocean. These samples were analyzed for particle size and, due to the bimodal distribution of the sediment, were separated into two size fractions, fine (<7.8 um) and coarse (7.8–62 um). These fractions were subject to a sequential chemical phase extraction procedure to differentiate the ion exchangeable, carbonate, metallic oxide coating, and organic phases. The extracted phases were analyzed with an inductively coupled plasma atomic emission spectrophotometer for Cd, Co, Cc, Cu, Fe, Ni, Pb, and Zn. Metals were found to be associated largely with the fine particle-size fraction. The concentration of fine particles (especially the <2 um size mode within the fine fraction) is crucial in influencing overall metal content. This is evidenced by strong correlations between the <2 μm or clay mode and concentrations in the metallic-oxide coating phase. Various metal/metal relationships exist among the phases and fractions studied and are highlighted by strong correlations, such as Ni and Zn, and Cu and Cd. The trends associated among the metal and mud concentrations are significant in terms of assessing the bioavailability of heavy metals within the river and estuary system, and, as a result, provide valuable insight into the ultimate fate of pollutants which are introduced to this unique environment.

Scanning electron microscopy with energy-dispersive electron probe X-ray analysis investigation of a sequential extraction scheme for copper, chromium, iron and aluminium speciation in marine suspended particulate matter

In a wider context of solid speciation studies and with a view to future application to real marine suspended particulate matter, a sequential chemical extraction procedure was tested on a plankton reference standard and checked with scanning electron microscopy with energy-dispersive electron probe X-ray analysis, and with atomic absorption and emission spectroscopic techniques. The results indicate that the procedure has a limited efficiency and needs further improvement. To increase the accuracy of the entire procedure, some steps, such as separation of the particulate matter from the filter and weighing of the particulate, have been optimized.

Speciation of particulate-bound Cadmium of soils and its bioavailability

A modified sequential chemical extraction procedure was developed for partitioning particulate Cd into eight fractions: exchangeable, carbonate-bound, metal–organic complex-bound, easily reducible metal oxide-bound, organic-bound, amorphous mineral colloid-bound, crystalline Fe oxide-bound, and residual. Results of experimental data on 16 surface soils of Saskatchewan, widely varying in physico-chemical properties, indicate the presence of little exchangeable Cd. Cadmium in these soils was predominantly in the form metal–organic complex-bound, accounting for 31–55%, with an average of 40%, of the total Cd present in the soils. The average relative abundance of the different forms of Cd present in these soils is in the order: metal–organic complex-bound (0.107 mg kg–1) > carbonate-bound (0.052 mg kg–1) > residual (0.042 mg kg–1) > organic-bound (0.035 mg kg–1) > crystalline Fe oxide-bound (0.016 mg kg–1) > easily reducible metal oxide-bound (0.010 mg kg–1) > amorphous mineral colloid-bound (0.002 mg kg–1). Statistical treatment of the Cd availability index, measured as ammonium hydrogencarbonate–diethylenetriaminepentaacetic acid (ABDTPA)-extractable Cd, with different particulate-bound Cd species showed high correlation (r= 0.916, p= 6 × 10–7) of the Cd availability index with the metal–organic complex-bound Cd. The beta coefficients obtained from the multiple regression analyses have given an insight into the importance of Al–organic complex-bound Cd species in estimating the bioavailability of Cd in these soils. The relationship of the metal–organic complex-bound Cd and the mobility and bioavailability of soil Cd merits in-depth research in explaining the toxicity and food chain contamination of Cd in the environment.

Chemical association of lead in auto shredder residue

Abstract The chemical distribution of lead in two samples of a unique solid waste stream, Auto Shredder Residue (ASR), is investigated employing a variety of chemical and physical analytical procedures. The results of the analysis suggest that the major source of lead contamination in this particular solid waste stream can be attributed to accumulated road dirt which contains particulate lead and amorphous lead oxide associated with the combustion of leaded gasoline. Although some lead oxides are detected as small paint chips associated with electro‐coated paint primers, used to provide corrosion resistance in automobiles, the actual quantities detected are small. The results of a sequential chemical extraction procedure indicate that the environmental mobility of the lead present in ASR is very sensitive to pH conditions. These results have important implications on the classification of the material as a “Hazardous”; or “Non Hazardous”; solid waste.

The chemical phase changes in heavy metals with drying and oxidation of the lake sediments

In order to understand the effects of oxidation on heavy metal behavior in sediments, the changes in chemical phase distributions of heavy metals with oxidation of sediments from Lake Teganuma were investigated using a sequential chemical extraction procedure for heavy metals. The exposure of sediments from the lake bottom to atmosphere caused the increase of Eh and the decrease of acid volatile-S in sediments. Most of the cadmium is expected to exist as relatively stable forms such as sulfides in original reduced sediments prior to exposure to the atmosphere. With the oxidation of sediments, Cd in the sulfidic/organic fraction were transformed to forms in the exchangeable and the reducible fractions which are easily dissolved. The chemical phase changes of Cu, Pb and Zn in sediments were less drastic than the case of Cd. Cadmium distinctly affected by the change in redox potential in sediments, and its behavior in the oxidized state is most mobile. Compared to Cd, the behavior of Cu and Pb are not so remarkably affected by the change in redox condition of sediments.

Trace Element Speciation in Soils and Sediments Using Sequential Chemical Extraction Methods

Abstract Several commonly used sequential chemical extraction procedures of heavy metals in soils and sediments are compared, and their advantages and disadvantages are discussed focusing on selected case studies. In particular, problems caused by handling of anoxic samples, and of specific phases (e.g. organic fractions and sulfides) are addressed. Eventually, recommendations for the improvement of extraction selectivity as well as the reduction of readsorption effects are given.

Heavy Metal Leachability From Solid Waste Incinerator Ashes

The leachability of heavy metals in municipal solid waste (MSW) incinerator residues was evaluated using equilibrium leach tests and the sequential chemical extraction procedure. Incinerator bottom ash, boiler and economizer fly ashes were sampled from a full-scale two-stage combustion facility without pollution-control devices. Fly ashes were also collected from a pilot-plant scale, lime-based flue-gas scrubber system, connected to a mass burning incinerator facility. Generally, bottom ashes contained low to moderate concentrations of cadmium, copper, lead and zinc which are relatively insoluble under normal landfill leaching conditions. Fly ashes contained relatively moderate concentrations of cadmium and copper and much higher concentrations of lead and zinc which are readily available for leaching under normal landfill conditions. Metal leachability appears to be dependent upon metal speciation, the pH of the leaching medium and ash particle size.

Bioavailable Cd, Pb and Zn in wet and dry deposition

Cadmium and lead have been determined in precipitation samples from nine rural sites in Canada and five in the United States. Samples from two precipitation events were analyzed from three of these sites. The average concentrations of cadmium and lead for the Canadian sites were 27.7 ngl −1 and 2.07 μgl −1 and for the U.S. sites, 48.8 ngl −1 and 2.08 μgl −1 respectively. The average amount of cadmium deposited in the precipitation events sampled at the U.S. sites was ten times the amount deposited at the Canadian sites. For lead, the U.S. to Canada ratio was 5.5. Atmospheric particulate filters from high-volume samplers located in south-central Ontario were subjected to a three-part sequential chemical extraction procedure to simulate environmental conditions during and after precipitation events to determine the biogeochemical availability of cadmium, lead and zinc. Water-soluble forms dominated the “particulate-speciation” of the three metals. The average percent water-soluble forms for the three metals for the six collection periods were Cd, 85% > Pb, 43% > Zn, 26%. The ease of solubility of the three metals on atmospheric particulate matter suggests that the greatest impact in terrestrial and aquatic systems will likely occur at interfaces, e.g. at forest canopies and at the air-water interface.

Multi-step sequential chemical extraction of heavy metals from urban soils

About 90 Glasglow surface soil samples (0–5 cm) were subjected to a six-step sequential chemical extraction procedure designed to establish the partitioning, mobility and availability of heavy metals lead, zinc, copper and cadmium in soils from a typical contaminated urban environment. The six fractions corresponding to the selected extractants were termed exchangeable, carbonate-bound, easily reducible, moderately reducible, organic and residual. Significant features of the average partitioning patterns were the association of 32% of cadmium (for total concentrations ≥ 0·6 mg kg −1) with the exchangeable + carbonate fractions, 51% of lead with the moderately reducible fraction and 41% of copper and 29% of zinc with the organic fraction. Only 17% of lead, compared with 42–46% of the other three elements, remained in the residual fraction. While total concentrations for the heavy metals suggested an order of contamination, lead > zinc > copper > cadmium, in Glasgow soils, the detailed sequential extraction data indicated an order of release or mobility of cadmium ⪢ lead > zinc > copper and an order of environmental concern, with respect to availability, of lead > cadmium > copper > zinc.

Notes. Availability of elements of environmental importance in incinerated sludge ash

An incinerated sludge ash from an industrialized urban area was analyzed by a sequential chemical extraction procedure to determine the chemical forms and potential availability of P, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. All 11 elements are relatively immobile with residual chemical forms comprising between 70% (P) and 97.7% (Pb) of the total elemental concentrations. The potentially toxic metals Cd, Cr, Cu, Ni, Pb, and Zn are ca. 90% in unavailable forms.

Sediment Fractionation of Cu, Ni, Zn, Cr, Mn, and Fe in One Experimental and Three Natural Marshes

AbstractDredged sediments from the Gulf Intracoastal Waterway near Galveston, Tex., were used as a substrate material in the construction of an experimental intertidal salt marsh. The objective of this research was to compare selected substrate properties of the experimental site with those of established marshes. Clay mineralogical properties of the experimental marsh were compared with those of three nearby natural marshes. A sequential chemical extraction procedure was used to obtain data on the partitioning of micronutrients and heavy metals among selected marsh substrate fractions.Clay minerals found in the sediments of the experimental marsh were equivalent to those identified in the natural marshes. Total elemental substrate concentrations of Cu, Ni, Cr, Zn, Mn, and Fe averaged 7.9, 8.6, 25.5, 25.2, 123, and 12,200 µg/g, respectively, over the four marsh sites. Copper, nickel, zinc, and chromium displayed only minor variations in substrate partitioning between the experimental and natural marsh samples. Micronutrients and heavy metal concentrations in the exchangeable and water‐soluble fraction were low compared with other fractions. Approximately 30% of the total substrate Cu, Ni, and Zn was associated with the organic matter fraction. Metals fixed within the lattice structures of clay and silicate minerals ranged from 20% Mn for experimental marsh samples to 90% Cr for one of the natural marshes. Major differences in Mn and Fe substrate partitioning were observed when the experimental marsh samples were compared with those of the natural marshes.