The effect of tissue structure and soil chemistry on trace element uptake in fossils

Trace element profiles for common divalent cations (Sr, Zn, Ba), rare-earth elements (REE), Y, U, and Th were measured in fossil bones and teeth from the c. 25 ka Merrell locality, Montana, USA, by using laser-ablation ICP-MS. Multiple traverses in teeth were transformed into 2-D trace element maps for visualizing structural influences on trace element uptake. Trace element compositions of different soils from the fossil site were also analyzed by solution ICP-MS, employing progressive leaches that included distilled H₂O, 0.1 M acetic acid, and microwave digestion in concentrated HCl-HNO₃. In teeth, trace element uptake in enamel is 2-4 orders of magnitude slower than in dentine, forming an effective trace element barrier. Uptake in dentine parallel to the dentine-enamel interface is enhanced by at least 2 orders of magnitude compared to transverse, causing trace element “plumes” down the tooth core. In bone, U, Ba and Sr are nearly homogeneous, implying diffusivities ∼5 orders of magnitude faster than in enamel and virtually complete equilibration with host soils. In contrast all REE show strong depletions inward, with stepwise linear segments in log-normal or inverse complementary error function plots; these data require a multi-medium diffusion model, with about 2 orders of magnitude difference in slowest vs. fastest diffusivities. Differences in REE diffusivities in bone (slow) vs. dentine (fast) reflect different partition coefficients (K_d’s). Although acid leaches and bulk digestion of soils yield comparable fossil-soil K_d’s among different elements, natural solutions are expected to be neutral to slightly basic. Distilled H₂O leachates instead reveal radically different K_d’s in bone for REE than for U-Sr-Ba, suggest orders of magnitude lower effective diffusivities for REE, and readily explain steep vs. flat profiles for REE vs. U-Sr-Ba, respectively. Differences among REE K_d’s and diffusivities may explain inward changes in Ce anomalies. Acid washes and bulk soil compositions yield misleading K_d’s for many trace elements, especially the REE, and H₂O-leaches are preferred. Patterns of trace element distributions indicate diagenetic alteration at all scales, including enamel, and challenge the use of trace elements in paleodietary studies.     

Meteorological impacts on the water quality in the Pajuluoma acid sulphate area,W. Finland

Water samples (n = 354) from a small catchment (7.4 km²) covered by acid sulphate soils (pH < 4) were collected during all seasons and all types of hydrological conditions in 1990–2001. The electric conductivity (EC) and pH, i.e. the key indicators of acid sulphate soil impact in the current setting, were determined. Representative daily runoff and precipitation data was available for the whole study period. The 10th and 90th percentiles for EC and pH were 29–140 mS/m and 3.8–4.6, respectively. While the water quality varied remarkably from year to year, and even within seasons, some regularity was found. The water quality was generally worst in late autumn (water temperature < 5 °C) and in spring. Of all seasons the variations were clearly smallest in spring, indicating that most representative samples can be obtained in this season. There were significant correlations between autumn, early winter and spring water quality within hydrological years. Thus acid and metal surges in spring are somewhat predictable. At base flow conditions (runoff about 1 L/s km² or less), the water quality was relatively good in all seasons. Above base flow conditions, the impact of acid sulphate soils tended to slightly increase with increasing runoff and precipitation, especially in early summer, but not in late summer. No significant signs of dilution during flood conditions (up to 100 L/s km²) were found and neither were there any correlations to rising or falling limbs. The severity of individual summer droughts, which in theory should increase the oxidation of S and acidity in the soils, had little or no impact on the water quality in subsequent autumn and spring. On the other hand, there was a remarkable long-term increase in EC and a corresponding decrease in pH (starting in 1995) after a suite of several very dry summers. After that the water quality did not improve even if the dry summers were followed by some wet summers. This indicates that the temporary pool of readily leachable acidity in the soils is fairly large. Moreover, it indicates that the potential shift towards more extreme global weather conditions (with more severe dry spells) may have significant impacts on the water quality in midwestern Finland, a region that is heavily affected by acidity and metals from acid sulphate soils.     

Spatial trends and losses of major and trace elements in agricultural acid sulphate soils distributed in the artificially drained Rintala area,W. Finland

Acid sulphate soils, common in the coastal areas of Finland, contribute strongly to high acid, S and metal loadings on adjacent surface waters. This, in turn, is causing significant harm to the aquatic ecology. There is, however, limited knowledge on the total amounts of acidity and chemical elements leached from these soils. The overall objective of this study was to determine geochemical patterns in acid sulphate soils and their parent sediments and, based on the identified patterns assess the extent, mechanisms and present state of leaching of major and trace elements from these soils. The distribution of pH, aqua regia extractable concentrations of P and metals (Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Mg, Mn, Na, Ni, Sr, Th, Ti, V, Zn) and total concentrations of S and C were determined in 30 vertical profiles collected in the 23 km² large Rintala agricultural area (mid-western Finland) underlain largely with S-rich sediments. It was found that approximately 70% of the area consists of acid sulphate soils with a minimum pH<4.0, an average depth of 1.8 m, and S concentrations in the parent sediments varying from 0.24 to 1.04%. Acid sulphate soils have not developed where the S concentrations in the sediments are ⩽0.10% or where the concentrations of organic C in the soil zones are >4%. Four different methods were used to estimate the losses of chemical elements from the acid sulphate soils: (1) the concentrations in the soil were compared with those in the parent sediments, (2) due to indicated heterogeneities in several profiles, the vertical changes of the immobile Ti was used to re-calculate element losses, (3) element depletions in the acid sulphate soils (as compared to those in the parent sediments) were compared to the corresponding depletions in the non acid sulphate soils, (4) element concentrations in drainage waters were compared with those in the parent sediments. Based on these calculations, it was assessed that the percentual leaching of the aqua regia extractable fraction (total for S) has been as follows: S (40–50%), Na (30–50%), Mn (25–35%), Sr (15–20%), Ca–Ni–Co (approximately 10%), Mg–K–Zn (5–10%), Th–La–Cu–Al–P–Ti–Fe (<5%), and Ba–Cr–V (<1%). While it was possible to quite accurately estimate the percentages and thus the amounts of elements lost, it was not possible to estimate the rate of leaching as there is no available detailed information on dates when ditching activities and thus oxidation-acidification processes started. Other calculations indicated that the mobile S reservoir is still some 15 ton/hectare, which is huge but still smaller than the losses that have occurred since the area was drained (23–28 ton/hectare).     

Major and trace element anomalies in stream sediments of the Teign Valley Orefield

A detailed geochemical and sedimentological study of twenty-two bulk stream sediments in the Teign Valley of southwest Devon shows the influence of lithology, mineralization and contamination on such cumulative samples. K, Cu and Ni in stream sediments emerge as potential indicators of lithology. Ba and S values, as well as barytes concentrations, demonstrate the contribution of Ba, Zn and Pb mineral lodes, whilst Fe, S and heavy-mineral percentages emphasize that of Fe lodes and contamination. As, Pb and Zn anomalies are observed within Fe-oxide crusts giving evidence of Fe in the role of scavenger. High Mn values are attributed to precipitations of the metal derived largely from impregnations of the Culm.     

The impact of acid rain on phosphorus leaching from a sandy loam calcareous soil of western Iran

Simulated acidic precipitation (1:1 equivalent basis H₂SO₄:HNO₃) at pH values of 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 7.0 were conducted using column leaching to determine impacts of simulated acid rain on phosphorus (P) leaching from a calcareous sandy loam soil over a 40-day period. Soil columns were irrigated every day to make a total of 1,061 mm, equivalent to 3.5 years of rainfall (based on average annual rainfall). Leachates were collected and analyzed for anions and cations. There was significant nonlinear correlation between the amount of P leached and the simulated acid rain (R ² = 0.61). Losses of P from the pH 2.5 and 7.0 treatments were 1.23, and 1.32 mg kg⁻¹, respectively. The results showed that the amount of P leached from pH 4 (1.46 mg kg⁻¹) and 5 treatments (1.52 mg⁻¹ kg⁻¹) were significantly larger than other treatments. Linear equation adequately described leaching of P in different treatments. The slope (mg kg⁻¹ day⁻¹) in the linear equation was defined as the leaching rate and for the pH 2.5 was 0.0354, and 0.0382 and 0.0406 for pH 4.5 and 7.0, respectively. The geochemical code Visual MINTEQ was used to calculate saturation indices. Leaching of P in different treatments was controlled by rate-limited dissolution of hydroxyapatite, β-tricalcium phosphate and to some extent octacalcium phosphate. The results indicate that acid rain in calcareous sandy loam soils may pose a risk in terms of groundwater contamination with P.     

Elevated stream trace and minor element concentrations in the foreland of receding tropical glaciers

Globally, the ongoing retreat of mountain glaciers will ultimately diminish fresh water supplies. This has already begun in watersheds with greatly reduced glacial coverage. Still unknown are the affects of glacial retreat on downstream water quality, including the threats to human and ecosystem health. In the Cordillera Blanca, retreating glaciers have exposed sulfide-rich rock outcrops, negatively affecting the quality of the glacial meltwater. This study has evaluated glacial melt stream hydrogeochemistry in the sulfide-bearing Rio Quilcay watershed (∼9°27′S, ∼77°22′W) during the 2008 dry season. Surface water samples were collected from the upper 12 km of the watershed during the 2008 dry season. Dissolved (0.4 μm) and unfiltered acidified (pH < 2) Al, Co, Cu, Fe, Ni, Mn, Pb, Zn and dissolved major ions and organic C (DOC) concentrations were quantified and pH and temperature were measured in the field. Twenty of 22 stream samples had pH values below 4, generating significantly (p < 0.01, α = 0.05) greater cation denudation normalized to discharge than other worldwide glacier-fed streams. Additionally, dissolved trace and minor element concentrations were comparable to acid mine drainage. Non-conservative dissolved element behaviors resulted from adsorption/desorption reactions in tributary mixing zones. At low pH values, hydrous Fe oxides acted as the dominant sorption surfaces. The poor water quality observed in Cordillera Blanca headwaters coupled with the likely exposure of additional sulfide-rich outcrops from ongoing glacial retreat may pose water quality challenges.     

The amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. A fluid inclusion study

This work presents the results of a fluid inclusion study of an amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. Early fluid-inclusions in the granulite facies area are characteristically carbonic (CO₂), in contrast to predominantly aqueous early inclusions in the amphibolite facies area. These early inclusions can be related to peak metamorphic conditions (750-820°C and 3-5 kbar for peak granulite facies metamorphism). Relatively young CO₂ inclusions with low densities (<0.8g/cm³) indicate that the first part of the cooling history of the rocks was characterized by a near isothermal uplift.
N₂-CH₄ inclusions, with compositions ranging between pure CH₄ and pure N₂ (Raman spectral analysis), were found in the whole area. They are probably syn- or even pre-early inclusions. Only nearly critical homogenizing inclusions have been found (low density). Pressure estimates, based on densities of early fluid inclusions, show that the rapid transition of amphibolite towards granulite facies metamorphism is virtually isobaric. Granulite facies metamorphism in West Uusimaa is a thermal event, probably induced by the influx of hot, CO₂-bearing fluids.     

The effect of Ca-Tschermaks component on trace element partitioning between clinopyroxene and silicate melt

We have studied the influence of Ca-Tschermaks (Calcium Tschermaks or CaTs) content of clinopyroxene on the partitioning of trace elements between this phase and silicate melt at fixed temperature and pressure. Ion probe analyses of experiments carried out in the system Na₂O–CaO–MgO–Al₂O₃–SiO₂, at 0.1 MPa and 1218°C, produced crystal-melt partition coefficients (D) of 36 trace elements (Li, Cl, Sc, Ti, V, Cr, Fe, Co, Ge, Sr, Y, Zr, Nb, Mo, Ru, Rh, In, Sn, Sb, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta and W), for clinopyroxene compositions between 10 and 32 mol% CaTs. Partition coefficients for 2+ to 5+ cations show, for each charge, a near parabolic dependence of log D on ionic radius of the substituting cation, for partitioning into both the M1 and M2 sites of clinopyroxene. Fitting the results to the elastic strain model of Blundy and Wood [Blundy, J.D., Wood, B.J., 1994. Prediction of crystal-melt partition coefficients from elastic moduli. Nature 372, 452–454] we obtain results for the strain-free partition coefficients of theoretical cations (D₀), with site radius r₀, and for the site's Young's Modulus (E).

In agreement with earlier data our results show that increasing ^ivAl concentration in cpx is matched by increasing D, E_M1, E_M2 and D₀ for tri-, tetra- and pentavalent cations. The degree of fractionation between chemically similar elements (i.e. Ta/Nb, Zr/Hf) also increases. In contrast, D values for mono-, di- and hexavalent cations decrease with increasing ^ivAl in the cpx. The large suite of trace elements used has allowed us to study the effects of cation charge on D₀, r₀ and E. We have found that D₀ and r₀ decrease with increasing cation charge, e.g. r₀=0.66 Å for 4+ cations and 0.59 Å for 5+ cations substituting into M1. Values of E_M1 and E_M2 increase with cation charge as well as with increasing ^ivAl content. The increase in E_M2 is linear and close to the trend set by Hazen and Finger [Hazen, R.M., Finger, L.W., 1979. Bulk modulus-volume relationship for cation–anion polyhedra. J. Geophys. Res. 84 (10) 6723–6728] for oxides. E_M1 values are much higher and do not fit the trend predicted by the Hazen and Finger relationship.     

水系沉积物测量发现新疆乌恰县吾合沙鲁中型铜矿

正1研究目的(Objective)新疆乌恰县吾合沙鲁地区位于塔里木盆地西缘,区域上发育重要的砂砾岩型铜铅锌-天青石-铀-煤成矿系统,已分布有乌拉根超大型砂砾岩型铅锌矿、萨热克大型砂砾岩型铜矿、萨哈尔铜矿、花园铜矿、杨叶铜矿、杨树沟铜矿、吾东—伊日库勒铜矿等典型矿床,具有十分独特的砂砾岩型铜铅锌矿     

Arsenic and presumed resistate trace element geochemistry of the Lincolnshire (UK) sedimentary ironstones,as revealed by a regional geochemical survey using soil,water and stream sediment sampling

A regional geochemical survey using soils, stream sediment and stream water sampling revealed multi-element geochemical anomalies, though of low environmental mobility, associated with Mesozoic sedimentary ironstones in Lincolnshire, UK. The most prominent of these anomalies were of As and V in soils and sediments, but elevated levels of elements such as Cr, La, Ce and Th were also observed. These were initially thought to be part of a residual resistate element or heavy-mineral suite, but careful examination suggests that these too may be primarily associated with the process of Fe oxide precipitation during the initial formation of the ironstones.     

The Lappajärvi meteorite crater,Finland: petrography,Rb-Sr,major and trace element geochemistry of the impact melt and basement rocks

Impact melt lithologies of the 77 m.y. old Finnish meteorite crater Lappajärvi as well as the Precambrian target rocks have been studied in detail, to identify and characterize different impact melt types (clast-poor, clast-rich, suevitic melt) and to study their chemical (major and trace elements) and isotopic (Rb-Sr) compositions in comparison to the composition of the target rocks.The Rb-Sr system of the whole melt body—including the suevitic melt—is shown to have been reequilibrated by the impact by extensive turbulent mixing of the various melted or vaporized target rocks. Chemical interactions (exchange of alkali elements, ⁸⁷Sr-redistribution) between feldspar clasts and impact melt surrounding them are the result of thermal metamorphism following the incorporation of target rock fragments of various degrees of shock metamorphism into the superheated melt. Exchange reactions between clasts and melt are determined by thermal activation, but the degree of shock metamorphism in the clasts plays an important role, too.Major and trace element distributions in impact melt and basement rocks indicate that the Lappajärvi melt body chemically is extremely homogeneous. Even volatile elements (such as Zn and Cu) were not strongly fractionated. Comparison of the abundances of siderophile elements in the impact melt (e.g., 118–177 ppm Cr, 195–340 ppm Ni, 6–12 ppb Ir) and calculated target rock mixture (79% mica schist, 11% granite-pegmatite, 10% amphibolite) (e.g., 85.6 ppm Cr, 54.8 ppm Ni, 0.5 ppb Ir) revealed the chondritic nature (C or H chondritic) of the meteoritic projectile. Less than 2% of the meteorite can be detected in the coherent melt, whereas the suevitic melt is uncontaminated by the projectile.     

Transportation and evolution of trace element bearing phases in stream sediments in a mining – Influenced basin (Upper Isle River,France)

Arsenic-bearing stream sediments enter the Upper Isle River, an Au mining-influenced basin (France), by the discharge of mining sites, tailings runoff and weathering of mineralized veins in granites and gneiss. Some fresh ochreous As-rich deposits on the river banks and in floodplains are identified as additional As-rich point sources (As between 0.07 and 6.5 wt.%). The <63 μm fraction of stream sediments contains elevated As bulk concentrations, ranging from 160 to 890 mg/kg, compared to the geochemical background (70 mg/kg on average). It is also enriched in Cd, Hg and W. Spatial variations of these trace elements show 3 significant increases corresponding to the 3 drained mining districts. They decrease down river but are still enriched 30 km downstream of the mining districts due to downstream transportation. Three types of trace element-bearing phases have been identified as: (i) detrital primary sulfides, with high in situ As percentages (up to 43.7 wt.%). They also carry significant amounts of W according to the differences in chemical compositions of the total and light <63 μm fractions. These sulfide particles do not show any sign of alteration in the oxygenated stream sediments; (ii) Secondary Fe–Mn oxyhydroxides,some with very high in situ As₂O₅ concentrations (up to 59.8 wt.%) and with about 40% of the total Cd composition. They occur as fresh precipitates in the river banks and floodplains and as discrete particles in stream sediments and (iii) Al–Si fine-grained phases. Their major element composition is highly variable with in situ As₂O₅ concentrations ranging between 430 and 5020 mg/kg. This type of solid phase is also the major carrier of Hg.     

The effect of leaching on the integrity of a natural clay

Leaching effects on the strength of a natural clay substrate can lead to loss of integrity of pond containment situation — especially if the clay material constitutes the liner system for the containment pond. In this study, the integrity of the clay in the face of five different types of leachates is studied via the creep characteristics of the clay. The resultant effects are evaluated in terms of (a) soil fabric/structure reinforcement or degradation, and/or (b) changes in the relationships established between soil particles and chemical pore fluid. The integrity of the clay is seen to be severely conditioned by (a) factors producing the initial soil structural state, (b) the chemistry of the leachate, (c) local boundary conditions, and (d) time.     

Effects of biochar-based fertilizers on nutrient leaching in a tobacco-planting soil

Acta Geochimica - Biochar is a soil amendment for increasing soil quality and decreasing nutrient leaching. However, there is little information on the impact of biochar-based fertilizer (BF) on...     

The influence of carbon on trace element partitioning behavior

Carbon has been proposed as a potential light element in planetary cores, included in models of planetary core formation, and found in meteoritic samples and minerals. To better understand the effect of C on the partitioning behavior of elements, solid/liquid partition coefficients (D = (solid metal)/(liquid metal)) were determined for 17 elements (As, Au, Co, Cr, Cu, Ga, Ge, Ir, Ni, Os, Pd, Pt, Re, Ru, Sb, Sn, and W) over a range of C contents in the Fe-Ni-C system at 1 atm. The partition coefficients for the majority of the elements increased as the C content of the liquid increased, an effect analogous to that of S for many of the elements. In contrast, three of the elements, Cr, Re, and W, were found to have anthracophile (C-loving) preferences, partitioning more strongly into the metallic liquid as the C content increased, resulting in decreases to their partition coefficients. For half of the elements examined, the prediction that partitioning in the Fe-Ni-S and Fe-Ni-C systems could be parameterized using a single set of variables was not supported. The effects of S and C on elemental partitioning behavior can be quite different; consequently, the presence of different non-metals can result in different fractionation patterns, and that uniqueness offers the opportunity to gain insight into the evolution of planetary bodies.     

The trace element composition of silicate inclusions in diamonds: a review

On a global scale, peridotitic garnet inclusions in diamonds from the subcratonic lithosphere indicate an evolution from strongly sinusoidal REE_N, typical for harzburgitic garnets, to mildly sinusoidal or “normal” patterns (positive slope from LREE_N to MREE_N, fairly flat MREE_N–HREE_N), typical for lherzolitic garnets. Using the Cr-number of garnet as a proxy for the bulk rock major element composition it becomes apparent that strong LREE enrichment in garnet is restricted to highly depleted lithologies, whereas flat or positive LREE–MREE slopes are limited to less depleted rocks. For lherzolitic garnet inclusions, there is a positive relation between equilibration temperature, enrichment in MREE, HREE and other HFSE (Ti, Zr, Y), and decreasing depletion in major elements. For harzburgitic garnets, relations are not linear, but it appears that lherzolite style enrichment in MREE–HREE only occurs at temperatures above 1150–1200 °C, whereas strong enrichment in Sr is absent at these high temperatures. These observations suggest a transition from melt metasomatism (typical for the lherzolitic sources) characterized by fairly unfractionated trace and major element compositions to metasomatism by CHO fluids carrying primarily incompatible trace elements. Melt and fluid metasomatism are viewed as a compositional continuum, with residual CHO fluids resulting from primary silicate or carbonate melts in the course of fractional crystallization and equilibration with lithospheric host rocks.

Eclogitic garnet inclusions show “normal” REE_N patterns, with LREE at about 1× and HREE at about 30× chondritic abundance. Clinopyroxenes approximately mirror the garnet patterns, being enriched in LREE and having chondritic HREE abundances. Positive and negative Eu anomalies are observed for both garnet and clinopyroxene inclusions. Such anomalies are strong evidence for crustal precursors for the eclogitic diamond sources. The trace element composition of an “average eclogitic diamond source” based on garnet and clinopyroxene inclusions is consistent with derivation from former oceanic crust that lost about 10% of a partial melt in the garnet stability field and that subsequently experienced only minor reenrichment in the most incompatible trace elements. Based on individual diamonds, this simplistic picture becomes more complex, with evidence for both strong enrichment and depletion in LREE.

Trace element data for sublithospheric inclusions in diamonds are less abundant. REE in majoritic garnets indicate source compositions that range from being similar to lithospheric eclogitic sources to strongly LREE enriched. Lower mantle sources, assessed based on CaSi–perovskite as the principal host for REE, are not primitive in composition but show moderate to strong LREE enrichment. The bulk rock LREE_N–HREE_N slope cannot be determined from CaSi–perovskites alone, as garnet may be present in these shallow lower mantle sources and then would act as an important host for HREE. Positive and negative Eu anomalies are widespread in CaSi–perovskites and negative anomalies have also been observed for a majoritic garnet and a coexisting clinopyroxene inclusion. This suggests that sublithospheric diamond sources may be linked to old oceanic slabs, possibly because only former crustal rocks can provide the redox gradients necessary for diamond precipitation in an otherwise reduced sublithospheric mantle.     

酸活化坡缕石对土壤中Cd的钝化效果研究

为探究不同浓度H2SO4溶液活化的坡缕石对土壤中Cd的钝化效果,使用浓度分别为5％、7.5％、10％、12.5％、15％的H2SO4溶液对坡缕石进行活化,加入Cd污染土壤进行钝化实验和盆栽实验.结果表明:施加不同浓度H2SO4溶液活化的坡缕石均能显著降低土壤有效态Cd含量,10％的H2SO4活化的坡缕石钝化效果最显著,...     

Geochemistry of stream water in a catchment in Finland affected by sulphidic fine sediments

The impact of sediment type on stream water geochemistry was studied in a catchment in Finland affected by sulphidic fine-grained sediments. Stream water samples for general characterisation of water quality (pH, electrical conductivity) were taken at the basin outlet during various hydrological conditions, while samples for detailed geochemical analysis were collected at 119 sites in the catchment on one single occasion during high-water flow in autumn. The occurrence of sulphidic fine sediments was estimated based on data from an airborne electromagnetic survey carried out by the Geological Survey of Finland.Growing-symbol maps, which were prepared for each of the studied variables in water, and statistical calculations including factor analysis and Spearman correlations show that the concentrations of Al, Ga, U and Tl, all the lanthanides and several alkali and alkaline earth metals (K, Mg, Na, Li, Ca, Rb, Sr), transition metals (Cd, Co, Cu, Zn, Sc, Mn, Ni, Y, Hf) and non-metals (S, Br, I, Si) increase in water when the proportion of the catchment cover of sulphidic fine sediments increases. It is therefore argued that these elements are released and mobilised in considerable amounts by the oxidation and subsequent acidification and weathering of this type of sediment. Other elements are either slightly depleted in streams in areas of sulphidic fine sediments (V, Nb, Pb, Zr), have a distribution unrelated to sediment type (Fe, Cr, Cs, Mo), or are only weakly impacted by the occurrence of sulphidic sediments in the catchment (As, Ti, Ba). It is argued that these elements are not leached extensively from the oxidising sulphidic sediments, and that their distributions at least partly may be controlled by the contents of dissolved humic material and/or suspended organic and inorganic phases in the water.