Concretion Bodies Research Articles

Macro- and microelements in Fe-Mn concretions of cryogenic soils

The role of iron-manganese concretions (IMC) in the processes of accumulation and migration of macro- and microelements in automorphic loamy soils of the southern tundra is estimated. The features of the profile distribution and properties of IMC in the natural tundra soil (Dystric Cambisols) and meadow cultivated soil (Epistagniс Gelic Cambisols) are identified. Differences in the composition of IMC properties of the studied soils are observed both in the upper part of the profile disturbed under anthropogenic impact, and in the lower part preserved the structural features of natural soil. In tundra soils an active redistribution and accumulation of Pb, Cd, Co, As, Mn, and Fe in IMC are specified. Agricultural reclamation of tundra soils makes to the activation of the concretion formation processes. In the cultivated soils, the total amount of IMC increases and a more expressive migration of Fe, Mn, Co down the soil profile and their adsorption in concretion bodies from lower horizons are observed. A decrease in the As content in the IMC of the cultivated tundra soils as compared to natural tundra soils are revealed. This is possible with the high biophilicity of As and its removal from the soil system with the biomass harvest.

Development and application of new composite grouting material for sealing groundwater inflow and reinforcing wall rock in deep mine

With cement, bentonite, water glass, J85 accelerator, retarder and water as raw materials, a new composite grouting material used to seal groundwater inflow and reinforce wall rock in deep fractured rock mass was developed in this paper. Based on the reaction mechanism of raw material, the pumpable time, stone rate, initial setting time, plastic strength and unconfined compressive strength of multi-group proportion grouts were tested by orthogonal experiment. Then, the optimum proportion of composite grouting material was selected and applied to the grouting engineering for sealing groundwater inflow and reinforcing wall rock in mine shaft lining. The results show the mixing proportion of the maximum pumpable time, maximum stone rate and minimum initial setting time of grout are AK4BK1CK4DK2, AK3BK1CK1DK4 and AK3BK3CK4DK1, respectively. The mixing proportion of the maximum plastic strength and unconfined compressive strength of grouts concretion bodies are AK1BK1CK1DK3 and AK1BK1CK1DK1, respectively. Balanced the above 5 indicators overall and determined the optimum proportion of grouts: bentonite-cement ratio of 1.0, water-solid ratio of 3.5, accelerator content of 2.9% and retarder content of 1.45%. This new composite grouting material had good effect on the grouting engineering for sealing groundwater inflow and reinforcing wall rock in deep fractured rock mass.

Microbially-mediated fossil-bearing carbonate concretions and their significance for palaeoenvironmental reconstructions: A multi-proxy organic and inorganic geochemical appraisal

Carbonate concretions are widespread within the geological record. However, the lack of recent known analogues creates a need for novel approaches to unravel the major microbial players involved in concretion formation and establish their suitability as palaeoenvironmental recorders. Here, we used a combination of geochemical and geological techniques to study two pyritiferous calcite concretions and compared the results with their host sediment (Toarcian “Posidonia Shale”, 183Ma, SW-Germany).The 13C-depleted nature of the concretion bodies, with average values of δ13Ccarb (−14.8‰), δ13Corg (−32.4‰), and δ13Cn-alkanes (−34.9‰), indicates that sulphate-reducing bacteria (SRB), played a major role in the concretion growth and preservation of the nucleus via the rapid decomposition of organic matter (OM). However, Rock-Eval analyses from both concretions revealed elevated hydrogen indices (HI) in the body and low HI values at the rim. These values suggest that most of the microbial activity did not occur in the concretion body but rather at the rim and at the surface of the nuclei, which generally supports the exceptional preservation of OM in carbonate concretions. Furthermore, enrichment in euhedral pyrite in the concretion rims suggests they were formed through increased activities of iron reducing (FeR) bacteria coupled to a decrease of SRB activity leading towards conditions more favourable to the direct precipitation of pyrite. Despite low δ13C values, the known lipid biomarkers such as acyclic extended isoprenoids or 3β-methyl-hopanes did not reveal evidence of an active methane cycling. The present study emphasises the crucial role of carbonate concretion in OM preservation and highlights their great potential as palaeoenvironmental recorders.

Clumped-Isotope Constraints On Cement Paragenesis In Septarian Concretions

Septarian concretions exhibit multiple generations of cements that include body, fringe, and spar phases. Classic paragenetic interpretations include initial precipitation of the body followed by fringe(s) and then by spar in more or less discrete events. Traditional approaches (e.g., carbon and oxygen isotope analyses) are generally unable to distinguish paragenetic trends as they relate to specific formation environments (e.g., precipitation during burial or with meteoric influx). Here we present carbonate clumped-isotope, δ13C (δ13Ccarb), and δ18O (δ18Ocarb) values for septarian concretions taken from four host units in order to assess cement paragenesis and overcome traditional shortcomings. Clumped-isotope and δ18Ofluid data exhibit a wide range of values, with carbonate precipitation temperatures between ∼ 20 and 50°C and δ18Ofluid compositions of ∼ −14 to +4‰ (VSMOW). In stable-isotope cross-plots, specific cement phases group together and confirm the paragenesis indicated by superposition. In some cases, samples analyzed from concretion bodies yield temperature and δ18Ofluid values that indicate formation at shallow depths, consistent with independent data (e.g., high minus-cement porosity, external laminae deflection). In contrast, other concretion-body analyses indicate relatively high body temperatures that conflict with shallow-formation indices. Petrographic and backscatter scanning electron microscopy (SEM) reveal that concretion bodies partially consist of a secondary, replacement phase, which could explain the higher temperatures expressed in bulk body samples. Based on data for different phases in these septarian concretions, we suggest that initial body-cement precipitation occurred at relatively shallow depths from unmodified seawater, followed by fringe formation at elevated temperatures that likely coincided with the emplacement of the secondary body phase. When considered together, late-stage spar phases exhibit temperatures and δ18Ofluid values supportive of spar precipitation from fluids with a significant meteoric component, possibly during uplift.

Experimental study on anti-seepage grout made of leachate contaminated clay in landfill

Leachate-contaminated clay was used as the base material, where cement and the self-developed clay curing agent were added to form an anti-seepage grout that can repair the leachate-contaminated clay in landfills, exhibit low permeability, and retard pollutants in the leachate. The effect of grout formula on the concentration of leaching pollutants, concretion rate, compressive strength, and permeability coefficient of concretion bodies was studied through a series of laboratory experiments. The efficiency of concretion bodies in retarding the leachate pollutants was investigated through a permeability test. The results indicated that the pollutants in the leachate-contaminated clay were controlled effectively. At 20% cement, 2% clay curing agent, and 1:1 water–soil ratio, the permeability coefficient of the concretion bodies after 7days is ~10−7cm/s, with >1 concretion rate and >1.2MPa unconfined compressive strength. In addition, the concretion bodies reached >85% retardation rate for COD in the leachate and >99.8% for NH3-N (including heavy metals such as Pb and Cd, among others). The retardation rate of the concretion bodies for the heavy metals is proportional to the ionic radius. As the cement content increased (clay curing agent=10% cement), the concretion rate and permeability of the concretion bodies decreased, whereas its compressive strength increased.

Jurassic septarian concretions from NW Scotland record interdependent bacterial, physical and chemical processes of marine mudrock diagenesis

AbstractSeptarian concretions in the Staffin Shales Formation (Kimmeridgian, Isle of Skye) allow controls on concretion rheology and septarian cracking to be investigated. Stratabound concretions consist of anhedral ferroan calcite microspar enclosing clay and minor pyrite. Intergranular volumes range from 77% to 88%, and calcite δ13C and δ18O values in most concretion bodies range from −10·0‰ to −17·3‰ and +0·3‰ to −0·6‰ respectively, consistent with rapid and pervasive cementation in marine pore fluids. Septarian rupture occurred during incipient cementation, with a sediment volume reduction of up to 43%. Crack‐lining brown fibrous calcite records pore fluid re‐oxygenation during a depositional hiatus, followed by increasing Fe content and δ13C related to bacterial methanogenesis. Brown colouration results from an included gel‐like polar organic fraction that probably represents bacterially degraded biomass. A new hypothesis for concretion growth and septarian cracking argues that quasi‐rigid ‘proto‐concretions’ formed via binding of flocculated clays by bacterial extracellular polysaccharide substances (EPS). This provided rheological and chemical conditions for tensional failure, subcritical crack growth, volume contraction, calcite nucleation, and incorporation of degraded products into crack‐lining cements. Bacterial decay of EPS and syneresis of host muds provided internal stresses to initiate rupture at shallow burial. Development of septarian (shrinkage) cracks in muds is envisaged to require pervasive in situ bacterial colonization, and to depend on rates of carbonate precipitation versus EPS degradation and syneresis. Subsequent modification of septarian concretions included envelopment by siderite and calcite microspar, hydraulic fracturing associated with Cretaceous shallow burial or Palaeogene uplift; and cementation by strongly ferroan, yellow sparry calcite that records meteoric water invasion of the host mudrocks. An abundance of fatty acids in these spars indicates aqueous transport of organic breakdown products, and δ13C data suggest a predominantly methanogenic bicarbonate source. However, the wide δ18O range for petrographically identical cement (−1·3‰ to −15·6‰) is difficult to explain.

Sandstone-hosted concretions record evidence for syn-lithification seismicity, cavitation processes, and Palaeocene rapid burial of Lower Cretaceous deep-marine sandstones (Outer Moray Firth, UK North Sea)

Syn- and post-lithification cemented fractures are abundant in concretions formed during shallow burial of Hauterivian turbidites in the Outer Moray Firth. Early fractures are irregular, bifurcating, and contain entrained sand grains. They are confined to the concretion bodies, but commonly splay into narrower fracture swarms at the margins. Multiple, cross-cutting fills of calcite microspar have similar isotopic composition to adjacent concretionary cements, suggesting that rupture and cementation cycles occurred as host concretions lithified. Expulsion of cementing pore fluids from the fractures produced cement protrusions at concretion margins. A hydraulic fracture mechanism resulting from localized permeability heterogeneity and episodic seismic activity is proposed. Rapid seismic loading created high pore fluid pressures for fracture dilation in lithifying concretions and, through cavitation and CO 2 degassing, a trigger for rapid homogeneous nucleation of calcite. Many of the early structures were subsequently reactivated as brittle tensile fractures, and host a variety of mesogenetic cements. Reactivation probably occurred in response to stress amplification during rapid Palaeocene burial. By this time lithification of the concretions had dramatically changed their rheology and failure style. Minor permeability remained in the concretion cements adjacent to reactivated fractures, permitting invasion of intercrystalline voids by late diagenetic fluids.

Organic geochemistry and stable isotope composition of New Zealand carbonate concretions and calcite fracture fills

Carbonate concretion bodies, representing a number of morphological types, and associated calcite fracture fills, mainly from New Zealand, have been studied both organically and inorganically. Extracted organic material is dominated by a complex polymeric dark brown highly polar fraction with a subordinate less polar and lighter coloured lipid fraction. The relative proportion of the two fractions is the principal control on the colour of fracture fill calcites. Concretions are classified mainly by reference to their carbonate stable carbon and oxygen isotope and cation composition. Typical subspherical calcitic septarian concretions, such as those in the Paleocene Moeraki and the Eocene Rotowaro Siltstones, contain carbon derived mainly by bacterial sulfate reduction in marine strata during early diagenesis. Other concretions, including a septarian calcitic type from the Northland Allochthon, have a later diagenetic origin. Siderite concretions, abundant in the non‐marine Waikato Coal Measures, are typically dominated by methanogenic carbon, whereas paramoudra‐like structures from the Taranaki Miocene have the most extreme carbon isotope compositions, probably resulting from methane formation or oxidation in fluid escape conduits. Lipids from concretion bodies and most fracture fill calcites contain significant concentrations of fatty acids. Concretion bodies dominated by bimodally distributed n‐fatty acids with strong even‐over‐odd preference, in which long chain n‐acids are of terrestrial origin, have very low hydrocarbon biomarker maturities. Concretion bodies that lack long chain n‐acids often have higher apparent biomarker maturity and prominent α‐ω diacids. Such diacids are abundant in fracture fill calcites at Rotowaro, especially where calcite infills the septaria of a siderite concretion in the non‐marine Waikato Coal Measures, and support the view that fluid transport resulted in carbonate entrapment of the fracture‐hosted acids. Diacids also occur in Northland calcite concretion bodies, but not in their septarian fracture fill. Release from kerogen into migrating pore fluid during an early organic maturation stage is suggested as a plausible origin of the diacids. Their site of entrapment may have been serendipitous, depending on the timing of concretion body and fracture fill carbonate precipitation.

Fatty acids in sparry calcite fracture fills and microsparite cement of septarian diagenetic concretions

Sparry calcite fracture fills and concretion body cements in concretions from the Flodigarry Shale Member of the Staffin Shale Formation, Isle of Skye, Scotland, entrap and preserve mineral and organic materials of sedimentary and diagenetic origin. Fatty acids are a major component of the lipids recovered by decarbonation and comprise mainly n-alkanoic and α-ω dicarboxylic acids. Two generations of fracture-fill calcite (early brown and later yellow) and the concretion body microspar yield significantly different fatty acid profiles. Early brown calcites yield mainly medium-chain n-alkanoic acids with strong even predominance; later yellow calcites are dominated by α-ω dicarboxylic acids with no even predominance. Both fracture fills lack the long-chain n-alkanoic and α-ω dicarboxylic acids additionally recovered from the concretion bodies. The absence of longer chain acids in the calcite spar fracture fills is inferred to result from the transport of fatty acids by septarian mineralising fluids whereby low-aqueous solubility of longer chain acids or their salts accounts for their relative immobility. Comparative experiments have been carried out using conventional solvent extraction on the concretion body and associated shales, both decarbonated and untreated. Extracted lipid yields are higher, but the fatty acids probably derive from mixed locations in the rock including both kerogen- and carbonate-associated lipid pools. Only experiments involving decarbonation yielded α-ω dicarboxylic acids in molecular distributions probably controlled mainly by fluid transport. Alkane biomarker ratios indicate very low thermal maturity has been experienced by the concretions and their host sediments. Septarian cracks lined by brown calcite formed during early burial. Microbial CO 2 from sulphate-reducing bacteria was probably the main source of mineralising carbonate. Emplacement of the later septarian fills probably involved at least one episode of fluid invasion.

Basin-scale dolomite cementation of shoreface sandstones in response to sea-level fall

Research Article| October 01, 2003 Basin-scale dolomite cementation of shoreface sandstones in response to sea-level fall Kevin G. Taylor; Kevin G. Taylor 1Department of Environmental and Geographical Sciences, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, UK Search for other works by this author on: GSW Google Scholar Rob. L. Gawthorpe Rob. L. Gawthorpe 2Department of Earth Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK Search for other works by this author on: GSW Google Scholar GSA Bulletin (2003) 115 (10): 1218–1229. https://doi.org/10.1130/B25227.1 Article history received: 01 Aug 2002 rev-recd: 15 Jan 2003 accepted: 12 Mar 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Kevin G. Taylor, Rob. L. Gawthorpe; Basin-scale dolomite cementation of shoreface sandstones in response to sea-level fall. GSA Bulletin 2003;; 115 (10): 1218–1229. doi: https://doi.org/10.1130/B25227.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract This study documents a link between sea-level fall and basin-scale dolomite cementation of shoreface sandstones in the Upper Cretaceous Desert Member, Book Cliffs, Utah, by integrating sedimentology, sequence stratigraphy, and sedimentary geochemistry. Within the Desert Member shoreface sandstones, a number of high- frequency sequence boundaries formed as a result of relative sea-level falls that led to localized incised valley formation, subaerial exposure, and meteoric leaching of upper shoreface sandstones. Shoreface sandstones up to 10 km downdip from these subaerial exposure surfaces contain ferroan dolomite concretion bodies as much as 8 m thick. Basinward of this smaller (as much as 1 m in size), less abundant dolomite, concretions can be traced at the same horizons. Some δ18O data suggest that cement precipitated from porewater with a significant meteoric component, although reequilibration and recyrstallization cannot be eliminated. Some δ13C data suggest carbonate derivation from detrital dolomite leached from beneath organic-rich coastal plain strata deposited during high-frequency sequence boundary development. We propose that during high-frequency sequence boundary formation, meteoric fluids migrated basinward into shoreface sandstones as a result of the relative fall in sea level. The precipitation of dolomite cement in the shoreface sandstones was promoted by the updip dissolution and remobilization of detrital dolomite by the meteroic fluids, mixing with marine pore fluids, and the presence of detrital dolomite in the shoreface sandstones, which acted as nucleation sites for dolomite precipitation. This study illustrates the impact of stratigraphic development upon basin-scale early diagenetic cementation of siliciclastic succcesions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Septarian concretions from the Oxford Clay (Jurassic, England, UK): involvement of original marine and multiple external pore fluids

Septarian concretions occur at several horizons within the Oxford Clay Formation, a marine mudstone containing pristine aragonite and immature biomarker molecules. They record the passage of at least four generations of pore fluids, the first of marine origin and the last still present in cavities. Concretion bodies formed, cracked, and calcite and pyrite precipitated in and around the cracks within the sulphate reduction zone, as demonstrated by C, O, S and Sr isotopic composition (Pore fluid 1). Before major compaction, sandstone dykes were intruded locally, and baryte precipitated, followed by coarse calcite cements with isotopically light oxygen and radiogenic strontium, indicating the introduction of meteoric‐derived water (Pore fluid 2). Later, coarse celestine within concretions has distinct sulphur‐isotopic composition and requires a further, geographically restricted, water source (Pore fluid 3). Celestine‐bearing concretions contain water in tight cavities whose isotopic composition is close to that of modern precipitation. Its chemistry shows that it is equilibrating with pre‐existing minerals implying a relatively recent origin (Pore fluid 4). The mineralogy of the Oxford Clay concretions shows that complex results can follow from a simple burial and uplift history, and that multiple generations of pore fluids can pass through a low‐permeability clay.

Oxygen and carbon isotopic composition of marine carbonate concretions; an overview; discussion and reply

In their review of isotopic data from marine carbonate concretions, Mozley and Burns (1993, p. 8 i) incorrectly associate our work (Dix and Mullins 1987) with their interpretation of the effects of recrystallization on isotopic compositions in concretions. Mozley and Burns (1993, p. 81) state, Late-stage calcite and siderite concretions are characterized by a combination of 'normal marine' 6~3C values and depleted 6~sO values. Such isotopic values have been interpreted by some authors as indicating recrystallization (i.e., that the concretion initially had normal marine carbon and oxygen isotopic compositions and that the oxygen isotopic compositions were reset at higher temperatures; Dix and Mullins 1987 . . . . ). The association of our work with this statement is incorrect because we illustrated that: (1) the bulk of the concretions in the Middle Devonian Hamilton Group appear to have formed during very early stages of burial within the upper 10 m (p. 147); (2) the very negative 5~3C values of most concretion samples and systematic shifts with concretion growth illustrate the role of organic diagenesis within the zone of sulfate reduction, and transitional into the upper zone of methanogenesis (our Fig. II); and (3) the only late-stage concretions (containing ferroan calcite) have 6'3C values ranging between 0 and 2%, and this due to a subsurface shift in porewater 6'3C related to organic diagenesis (our Fig. 11), not recrystallization (p. 150). In their discussion of causes for consistently depleted 5'80 values in shallow-burial calcite concretions, Mozley and Bums (1993, p. 77) appear to dismiss the effect of recrystallization partly through their assumption that the original composition of concretions must be stable low-magnesium calcite. They cite, however, only three studies of concretions that unequivocally remove any possibility for recrystallization. Are these the exceptions or the rule? Combined petrographic and isotopic observations still lead us to the interpretation that recrystallization of Hamilton Group concretions (excluding late-stage concretions) was very important. 6180 data fall within the middle of an isotopic group defined by late-stage septarian calcites, and our samples of septarian calcites also fall within this group with ~laO values that are not too dissimilar to the bulk of concretion calcite (our Fig. 12). We presented petrographic evidence illustrating that two stages of septafian calcite have been replaced by subsequent calcite, including ferroan calcite (our Fig. 7), and that replacement calcite is associated with silica diagenesis in the concretion bodies and migration of petroleum-bearing fluids. If septarian calcite can be replaced, why not the concretion-body calcite too? With so many calcite concretions appearing to form under near-surface burial conditions, could the mineral-water interaction that Mozley and Burns (1993) call upon to account for net shifts in ~aO include very shallow recrystallization ofa metastable magnesium-beating carbonate? Given the diverse mechanisms for causing a shift in 6'80 (Mozley and Burns 1993), recrystallization seems to be a plausible factor (see Desrochers and AI-Aasm 1993) that should not be discarded so readily.

The Fate of Calcium in The Diet of Rhodnius Prolixus: Storage in Concretion Bodies in the Malpighian Tubules

We have investigated the fate of the large amounts of calcium ingested by Rhodnius prolixus in its meals of blood. 45Ca2+ injected into the haemolymph or fed to fifth-stage Rhodnius reared on rabbits is accumulated at high concentrations in the cells of the upper Malpighian tubules; very little is excreted from the body This 45Ca2+ accumulation goes on continuously for at least 12 days and the rate of uptake is increased several-fold within 3-4 days of a meal. The extent of calcium accumulation in tubule cells is correlated with the presence of intracellular membrane-bound concretion bodies, which are therefore likely sites of calcium deposition. X-ray diffraction showed that the calcium deposits are non-crystalline. Tubules from rabbit-fed fifth-stage Rhodnius contain 410 mmol l-1 calcium; in those from chicken-fed insects the calcium concentration is over 1 mol l-1; and in those fed in vitro on heparinised low-K+ sheep blood the calcium concentration is only 21 mmol l-1. The concentration of calcium in the haemolymph in all these insects was 8 mmol l-1 and its activity determined by an ion-selective electrode was 2.5 mmol l-1. 45Ca2+ deposited in the tubules is readily exchangeable, but the efflux preferentially passes to the haemolymph side of the tubule epithelium. The ability to sequester calcium in the Malpighian tubules may prevent calcium from interfering with reabsorptive processes in the rectum.

The Moeraki Boulders--Anatomy of Some Septarian Concretions

ABSTRACT The Moeraki boulders are large (to 2 m) calcite concretions with septarian veins of calcite and rare late-stage quartz and ferrous dolomite. The concretions are enclosed by Paleocene marine mudstones with vitrinite reflectance values of 0.29% R suggesting maximum burial temperatures of 25-30°C. Microprobe analyses of these concretions indicate a Ca enrichment-Mg depletion trend with growth. Calcite in the core contains about 88 mole % Ca and about 93 mole % Ca in the rim. Both rim and cores contain less than 1 mole % Fe and Mn. Septarian veins also show a systematic calcium enrichment with growth of the vein. The initial vein fills are similar in composition to the outer rim of concretionary bodies, suggesting septarian cracks form contemporaneously with attainment of final concretion size. The later-stage calcite vein-fills have less than 1.5 mole % Mg and up to 11 mole % Fe + Mn. These elements systematically decrease both into and outward along the vein, with increasing calcium substitution. The above compositional trends in veins suggest continued crystallization during propagation of the fractures. The carbonate composition trends reflect interaction between the growing concretion and the enclosing mudstone pore-fluid system. The observed Fe, Mn, Mg depletion trends probably reflect depletion of elements released by short-time-scale diagenetic events of finite size. The growth time of the larger concretions is estimated at about 4 million years based on published diffusion growth models. Extrapolation of compositional trends versus growth time from these concretion bodies suggests that septarian veins form on a time scale of several million years.

Effect of tetramethyl lead on freshwater green algae.

The toxicity of tetramethyl lead (Me4Pb) towards freshwater algae was studied by bubbling biologically generated Me4Pb from one flask containing 5 mg of Pb 1-1 as Me3PbOAc into the culture medium in another flask where a test alga Scenedesmus quadricauda was grown. As Me4Pb is not soluble in water and is volatile, the exposure of an alga to this lead compound was only momentary. It was estimated that less than 0.5 mg of Pb(Me4Pb) had passed through the culture medium. The primary productivity and cell growth (determined by dry weight), however, decreased by 85% and 32% respectively, as compared with the controls without exposure to Me4Pb. Furthermore, cells exposed to Me4Pb tended to clump together and striking alterations in cell fine-structure were observed. An electron microscopic analysis by an energy dispersive spectrometer revealed that Pb ions had penetrated the cell and were deposited within concretion bodies. Similar results were obtained with the green algae Ankistrodesmus falcatus and Chlorella pyrenoidosa.