Serpentinite Soils Research Articles

Japonolirion osense, a close relative of the mycoheterotrophic genus Petrosavia, exhibits complete autotrophic capabilities

The plant kingdom exhibits a diversity of nutritional strategies, extending beyond complete autotrophy. In addition to full mycoheterotrophs and holoparasites, it is now recognized that a greater number of green plants than previously assumed use partly of fungal carbon. These are termed partial mycoheterotrophs or mixotrophs. Notably, some species exhibit a dependency on fungi exclusively during early ontogenetic stages, referred to as initial mycoheterotrophy. Japonolirion osense, a rare plant thriving in serpentinite soils, emerges as a potential candidate for initial mycoheterotrophy or mixotrophy. Several factors support this hypothesis, including its diminutive sizes of shoot and and seeds, the establishment of Paris-type arbuscular mycorrhizal associations, its placement within the Petrosaviales—largely composed of fully mycoheterotrophic species—and its ability to face the challenging conditions of its environment. To explore these possibilities, our study adopts a multidisciplinary approach, encompassing stable isotope abundance analyses, in vitro experiments, anatomical analyses, and comparative plastome analyses. Our study aims to (1) determine whether J. osense relies on fungal carbon during germination, indicating initial mycoheterotrophy, (2) determine if it employs a dual carbon acquisition strategy as an adult, and (3) investigate potential genomic reductions in photosynthetic capabilities. Contrary to expectations, our comprehensive findings strongly indicate that J. osense maintains complete autotrophy throughout its life cycle. This underscores the contrasting nutritional strategies evolved by species within the Petrosaviales.

Assessments of Heavy Metals Accumulation, Bioavailability, Mobility, and Toxicity in Serpentine Soils

Accumulation of heavy metals is a concerning issue due to their known persistence in the ecosystem, and there are standard limits established for their maximum allowable concentrations in soils. However, heavy metal accumulation coming from serpentinite soils often exceeds the regulatory values, and there is a lack of knowledge regarding their bioavailability, mobility, and toxicity in the environment. This research applied novel selective sequential extraction and leaching procedures to assess the gaps in knowledge regarding heavy metals accumulation on serpentinite topsoil derived from a few states in Peninsular Malaysia. Based on the total digestion method, the concentration of all studied heavy metals except Mn exceeded the site screening levels issued by the Department of Environment, Malaysia (DOEM). The Geo-accumulation Index categorized Cr, Cd, Ni, and Co as extreme contamination and Cu, Pb, Zn, and Mn as unpolluted to moderate contamination. From the extraction results, Cd was found bounded 100% to a residual fraction. Meanwhile, Ni, Co, and Cr were mostly (≥92%) found to be bound to a residual fraction, with the remaining percentages distributed within non-bioavailable fractions (crystalline Fe oxides, poorly crystalline Fe oxides, and Mn oxides). Nevertheless, Cu, Pb, Zn, and Mn contaminants showed an increase (1–9%) in bioavailability and mobility fractions (soluble–exchangeable, surface-adsorbed, and organic matter) which pose a threat to the environment. The toxicity of the heavy metals greatly surpassed the DOEM standards; however, it was still below the global USEPA toxicity control. This research concluded that, even though the toxicity level of the topsoils had not exceeded the global toxicity limit, the accumulation of heavy metals in the serpentinite soils needs to be addressed due to its high concentration and its being potentially bioavailable and mobile in the environment.

Determination of Some Heavy Metals in Serpentinitic Soils and Rocks from Sulaymaniyah / Kurdistan Region of Iraq

The present study aimed to investigated the assessed total content of Arsenics, Ba, Pb, Rb, Sn, Sr, U and V in serpentinitic soils and rocks that wide spread over Penjwin and Mawat area in Sulaymaniyah governorate/ Kurdistan region of Iraq. This research was carried out during the seasons of 2018-2019 in seven pedons (1, 2 and 3 from Penjwin area, 4,5, 6, and 7 from Mawat area) that chosen according to the variation in chemical composition of the parent materials that soil developed. The pedons of Penjwin area were classified as Inceptisols, while the pedons from Mawat area were classified as Mollisols. The results showed that the total selected metals concentration of soils in all pedons were varied, and the total contents of heavy metal in the soil samples decreased in the order of V > Sr > Ba > Rb > Pb > As >Sn > U. The total concentration of As, Ba, Pb, Rb, Sn, Sr, U and V in soils were ranged between (< 0.2 to 11.8, 20 to 310, 1.3 to 22.7, 3.2 to 71.4, 0.2 to 4.1, 69.1 to 179.0, 0.1 to 1.9 and 88 to 277 mg kg-1) respectively. In addition, V contents in these soils were higher in compared to the other studied elements, with considerable variation between pedons on different landscapes, which reflected the serpentinitic differences and degrees in chemical weathering of the associative serpentinitic rocks. Total concentration of studied metals in rocks from both areas were varied and these values ranged between (<5 to 6.0, <10 to 10, 6 to 37.3, 0.2 to 1.2, <0.2 to 17.3, 5.2 to 137, <0.1 to 0.4 and 15 to 206 mg kg-1) for As, Ba, Pb, Rb, Sn, Sr, U and V respectively.

Variations in serpentinitic soils in humid Asia

Variations in serpentinitic soils in humid Asia

Адаптивное управление лесным хозяйством: на примере лесов скального дуба (Quercus petraea (Matt.) Leibl.) горы Озрен республики Сербской

Adaptive management is a basic concept of managing forest ecosystems in the face of increased risks such as climate change. Therefore, there is a need to develop key theories and information on which adaptive forest management is based on. This paper deals with the overview of basic information on adaptive forest management, with particular reference to its importance in relation to examples of sessile oak forests drying and climate change in the Republic of Srpska, Bosnia and Herzegovina. Silviculture of sessile oak forests affected by acute and chronic drying of the trees should be based on the preservation of the complete set of stands and miscibility with black pine on shallow serpentinite and peridotite soils. The paper deals with the possibilities of adaptive management of sessile oak forests and concludes with a description of adaptive management activities.For citation: Govedar Z., Medarevic M. Adaptive Forest Management: Case Study of Sessile Oak (Quercus petraea (Matt.) Leibl.) Forests on Ozren Mountain of the Republic of Srpska. Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 3, pp. 93–105. DOI: 10.37482/0536-1036-2020-3-93-105

Studying the roles of calcium and magnesium in cell death in the serpentine native plant Alyssum inflatum NYÁRÁDY through cell suspension culture technique

Calcium is an essential element for plants’ survival and ability to deal with environmental stresses. However, it can cause cell death due to cellular disequilibrium. Serpentine plants are sensitive to high concentrations of Ca2+, which induces lethal symptoms, especially under environmental stress. In this study, the direct effects of Ca2+ on cell death were investigated in cell cultures of Alyssum inflatum, a serpentine plant native to Western Iran, and results were compared to a non-serpentinitic congeneric species A. saxatile. The results were also compared to the effects of Mg2+ treatments in both species, as another determinative factor in serpentinite soil is high Mg2+ content. Plasma membrane permeability, reactive oxygen species (ROS), and malondialdehyde (MDA) production were measured as physiological cell injury indices. In A. inflatum higher levels of ROS and MDA were observed in Ca2+-treated cells (5 mM or more), while in A. saxatile they were measured in Mg2+-treated cells (5 mM or more). In serpentine species, results indicated that cell death by Ca2+ was more intensive than the cell death by Mg2+, which were observed with less intensity in non-serpentine plants. Microscopic studies showed that cell death occurred via apoptosis-like programmed cell death (AL-PCD). Therefore, Ca2+ sensitivity and AL-PCD as mechanistic reasons for their non-serpentine intolerance would be a crucial consideration in cellular researches concerning serpentine plants, which could be employed in green technologies such as phytoremediation.

Multimetal Resistant, Alkalitolerant Bacteria Isolated from Serpentinizing Fluid-Associated Sediments and Acid Mine Drainage in the Zambales Ophiolite, the Philippines

Weathering in ophiolitic exposure settings often produces fluids and sediments that have elevated concentrations of various toxic heavy metals such as chromium, nickel, cobalt, copper, and zinc. Microorganisms inhabiting these environments (e.g., serpentinite soils or sediments) are likely adapted to tolerate these metals along with other physicochemical extremes. The purpose of this study is to isolate bacteria capable of tolerating extremely high concentrations of multiple metals and to assess the various tolerance mechanisms exhibited by different organisms. Sediment samples for microbial culturing were collected from Manleluag Spring National Park and Barlo Mine located on the island of Luzon, the Philippines. Luria-Bertani (LB) agar medium was supplemented with increasing concentrations of five trace elements – Cu, Cr, Co, Ni, and Zn. Over 20 isolates were obtained from media with concentrations ranging from 25 mg/L to 400 mg/L of each metal. Most isolates were identified as belonging to the genus Bacillus. Adaptation mechanisms, including potential biomineralization, were considered for select strains using inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). ICP-OES analysis suggests that the primary resistance mechanism used by most isolates is cellular efflux, although it was determined that some organisms were able to reduce aqueous Cu concentration by up to 40%. Most strains exhibited growth at pH 12, demonstrating that alkalitolerant, highly metal resistant organisms are found in these ophiolite-associated environments. These organisms may be exploited for bioremediation, secondary metabolite production, and other industrial applications.

Elemental Concentration in Serpentinitic Soils over Ultramafic Bedrock in Sierra Bermeja (Southern Spain)

Although the presence of potentially toxic metals in soils is normally associated with human soil pollution, these elements also appear naturally in environments in which the lithological base contains ultramafic rocks such as peridotites. Serpentinitic soils tend to develop on substrates of this kind, often containing metals with few or no known biological functions, which in some cases are toxic for most plants. This study assessed the level of potentially toxic metals and other elements in an endorheic basin discovered in Sierra Bermeja (Southern Spain), one of the largest peridotite outcrops on Earth. In this location—of particular interest given that basins of this kind are very rare on peridotites—six geomorphoedaphic sub-units on three different substrates were identified. The distribution of microelements in these sub-units was analyzed, and stratified random sampling was performed to identify the major ions with essential functions for living organisms and the potentially toxic metals. The lowest values for macronutrients appeared in the soils formed on ultramafic materials. When analyzing the load of potentially toxic metals, no significant differences were detected between the soils formed on serpentinite and peridotite substrates, although different values were obtained in the soils formed over acidic rocks.

Characteristics of phosphorus fractions in the soils derived from sedimentary and serpentinite rocks in lowland tropical rain forests, Borneo

ABSTRACT Soil organic phosphorus (P) is an important P source for biota especially in P-limited forests. Organic P has various chemical formations which differ in bioavailability and these organic P can be degraded by phosphatase enzymes. Here, we report soil P fractions inferred from solution 31P-NMR spectroscopy and soil phosphatase activities of two tropical rain forests on contrasting parent materials; sedimentary and ultramafic igneous (serpentinite) rocks. Compared to the sedimentary soils and previous studies, P fractions of the serpentinite soils have distinctly high proportions of pyrophosphate and scyllo-inositol hexakisphosphate (scyllo-IP6). The accumulation of pyrophosphate and scyllo-IP6 may be related to strong sorptive capacity of iron oxides present in the serpentinite soils, which implies a consequent low P availability in the serpentinite soils. Mean value of soil phosphatase activities was higher in the serpentinite soils than in the sedimentary soils, suggesting that biota in these serpentinite forests depend more on soil organic P as a P source.

Ecological implications of pedogenesis and geochemistry of ultramafic soils in Kinabalu Park (Malaysia)

In Sabah, Malaysia, ultramafic rock outcrops are widespread (totalling 3500km2, one of the main outcrops in the tropical zone), and predominantly of the peridotite type. However, strongly serpentinised peridotite is also locally common, particularly along fault lines in the Mt. Kinabalu area. This study aimed to determine the extent of chemical variation in ultramafic soils in relation to the degree of serpentinisation and the weathering intensity, and consequent potential ecological implications linked to resulting soil chemical fertility. It was hypothesized that young soils and soils derived from bedrock with a significant degree of serpentinisation strongly differ from typical Geric Ferralsols and result in soil chemistries with more adverse properties to plant life (e.g. low availability of the essential nutrients N, P, K and Ca and high concentrations of potentially phytotoxic Mg and Ni). Ultramafic soil diversity linked to the age of the soil or the degree of serpentinisation would thus be a main factor of plant diversity and distribution. The diverse topography of Kinabalu Park (ultramafic soils present between 400 and 2950masl) has given rise to high pedodiversity with the broad overall ultramafic soil types being: (i) deep laterite soils (Geric Ferralsols); (ii) moderately deep montane soils (Dystric Cambisols) with mor humus; (iii) shallow skeletal soils at high altitude (Eutric Cambisols Hypermagnesic); and (iv) bare serpentinite soils (Hypereutric Leptosols Hypermagnesic) at low altitude (200–700masl). Leptosols on serpentinite and Eutric Cambisols have the most extreme chemical properties in the whole Kinabalu Park area both with very high Mg:Ca molar quotients, with either high available Ni (Cambisols) or high pH (Leptosols). These soils host specific and adapted vegetation (high level of endemism) that tolerates geochemical peculiarities, including Ni hyperaccumulators. Geric Ferralsols present far less chemical constraints than Hypermagnesian Cambisols soils to the vegetation and host a tall and very diverse rainforest, not so different than that on non-ultramafic soils. It therefore appears that altitude, soil age and degree of bedrock serpentinisation are the main determining factors of soil properties: the qualifier “ultramafic” alone is not sufficient to define soil geochemical and ecological conditions in the Kinabalu Park area, probably more than in any other ultramafic region in the world.

Serpentine geology links to water quality and heavy metals in sediments of a stream system in central Queensland, Australia

Serpentinite soils, common throughout the world, are characterized by low calcium-to-magnesium ratios, low nutrient levels and elevated levels of heavy metals. Yet the water quality and heavy metal concentrations in sediments of streams draining serpentine geology have been little studied. The aim of this work was to collect baseline data on the water quality (for both wet and dry seasons) and metals in sediments at 11 sites on the Marlborough Creek system, which drains serpentine soils in coastal central Queensland, Australia. Water quality of the system was characterized by extremely hard waters (555–698 mg/L as CaCO3), high dissolved salts (684–1285 mg/L), pH (8.3–9.1) and dissolved oxygen (often >110% saturation). Cationic dominance was Mg > Na > Ca > K and for anions HCO3 > Cl > SO4. Al, Cu and Zn in stream waters were naturally high and exceeded Australian and New Zealand Environment and Conservation Council guidelines. Conductivity displayed the highest seasonal variability, decreasing significantly after wet season flows. There was little seasonal variation in pH, which often exceeded regional guidelines. Stream sediments were enriched with concentrations of Ni, Cr, Co and Zn up to 35, 21, 10 and 2 times the world average for shallow sediments, respectively. Concentrations for Ni and Cr were up to 60 and 16 times those of the relevant Interim Sediment Quality Guidelines Low Trigger Values, respectively. The distinctive nature of the water and sediment data suggests that it would be appropriate to establish more localized water quality and sediment guidelines for the creek system for the water quality parameters conductivity, Cu and Zn (and possibly Cr and Cd also), and for sediment concentrations of Cd, Cr and Ni.

Partition of geogenic nickel in paddy soils derived from serpentinites

Serpentinitic soils contain high concentrations of geogenic Ni. During serpentinitic mineral weathering, the Ni released from soils into ecosystems could be a source of non-anthropogenic metal contamination. In this study, soil samples were collected from two pedons in paddy fields in Taiwan and Japan; these samples were used to explore the profile distribution of total and labile Ni, demonstrating the contribution of Ni-bearing Fe and Mn oxides to the Ni partition in these soils. Serpentine and chlorite were the dominant primary minerals; thus, the soils reflected serpentinitic characteristics and exhibited high background concentrations of Ni. The total Ni content ranged from 240 to 520 mg kg−1. Repeated redox and leaching cycles caused the redistribution of Ni in the paddy soils. The diethylenetriamine pentaacetate (DTPA)-extractable Ni, an availability index of Ni, increased as the soil depth decreased in the two pedons. An additional pool of labile Ni was present in the soils because the Ni concentration determined using a 0.1 N HCl extraction was much higher than was that determined using the DTPA extraction. Fe and Mn oxides were closely related to the labile Ni in these paddy soils. However, Ni was predominantly retained by amorphous and crystalline Fe oxides rather than Mn oxides. Shortening the flooded duration of paddy field is required to reduce the solubility of Ni because that the labile Ni and redox-sensitive Fe oxides can affect both the paddy soils and environment when Ni is released into the soil solution and becomes bioavailable under reducing conditions.

A Novel Microbial Biofilm for Bioremoval of Nickel from Aqueous Media

ABSTRACTThis study evaluated the efficacy of a microbial biofilm in removing Ni ions in aqueous media. The biofilm was developed incorporating a garden soil fungus with a bacterium isolated from Ni-rich serpentinite soil. The biofilm was characterized using microscopy, scanning electron microscopy, Fourier transform infrared (FTIR) investigations, and Boehm and potentiometric titrations. Ni removal was determined using batch experiments as a function of pH, Ni concentration, and time. The adsorption isotherm assay was conducted with varying Ni concentrations from 25 to 500 mg/L for 4 days. Isotherm and kinetic modeling were applied to the experimental data to understand the mechanisms of Ni removal. The zero point charge at pH 4.5 indicated the pH values greater than 4.5 is favorable for Ni adsorption. Acidic nature of the biofilm was reflected from Boehm titration data showing higher number of acidic groups than basic groups. With the increase in initial Ni concentration, the uptake increased from 3.43 to 38.16 mg/g. Hill, the best-fitted isotherm model, indicated a maximum adsorption capacity of 165.37 mg/g. After 4 days, the adsorption rate reached an equilibrium with a maximum sorption of ∼30 mg/g for an initial concentration of 100 mg/L. Kinetic model fitting with Power function further demonstrated the chemisorptive interaction of Ni with the biofilm surface. A clear involvement of functional groups of the biofilm in Ni bonding was observed from the attenuated total reflection (ATR)-FTIR spectrum. The microbial biofilm showed an efficient but slow removal of Ni from aqueous media.

Bioleaching of Lizardite by Magnesium- and Nickel-Resistant Fungal Isolate from Serpentinite Soils—Implication for Carbon Capture and Storage

The major goal of this study was to evaluate the potential of fungal species indigenous to mine tailing soils in accelerating Mg release from lizardite (a polymorph of serpentine) at ambient T/P conditions. We characterized the culturable fungal isolates at three sampling sites representative of different degrees of mineral weathering by isolating the genomic subunits and internal transcribed spacer (ITS) rRNA genes using PCR and sequencing of cloned fragments. We chose the specific strain primarily identified as Talaromyces sp. for the further experiments with lizardite because of this strain's remarkable tolerance to high [Mg2+] (1 mol·L−1) and [Ni2+] (10 mM·L−1) levels in the screening test and its ubiquity in the most severely weathered samples. Results of dissolution experiments revealed that both magnesium-release rate and efficiency were significantly increased (e.g., by a factor of up to 15) in the presence of fungal cells than those in the abiotic controls. The enhanced dissolution of lizardite was mainly attributed to the fungal production of organic acids including oxalic acid, gluconic acid, formic acid, and fumaric acid added to the solution. The proton-promoted dissolution, however, was indicated not to be the only mechanism for fungus-lizardite interactions as much lesser Mg (in wt.%) was recovered in the abiotic system where the solution pH was constantly adjusted to match that of the fungal system. We also explored the dependence of fungal dissolution (of lizardite) on temperature and mineral particle sizes. In particular, we found that up to ∼ 50 wt.% of Mg was released from mineral particles of ∼ 50 μm within 30 days at 38°C, ∼ 26% and 8% higher than that at 18°C and 28°C, respectively. At the same temperature of 28°C, the Mg-release efficiency increased from 12.2 wt% for particles of ∼ 270 μm to 38.4 wt% for those of ∼100 μm although no apparent difference was recognized when the particle size decreased below 100 μm. The nonlinear correlation of dissolution rates with particle surface areas suggested that the dissolution process was controlled by mineral surface-structural modification along with Mg release and by fungal cells’ interaction with these surface structures. An amorphous layer of Mg-depleted silica was detected at the reacted mineral surface by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Formation of glushinskite (MgC2O4·2H2O) was also observed when oxalate was accumulated to certain concentrations in the solution. Overall, this study showed that the isolated Talaromyces sp. was a promising bioagent to improve the efficacy of cation release from serpentine minerals for the purpose of carbon sequestration and resource recovery.

Chromium and nickel in Pteridium aquilinum from environments with various levels of these metals.

Pteridium aquilinum is a ubiquitous species considered to be one of the plants most resistant to metals. This fern meets the demands for a good bioindicator to improve environmental control. Therefore, it was of interest to survey the accumulation of Cr and Ni in the rhizome and fronds of this species collected in Lower Silesia (SW Poland) of serpentinite rich in Cr and Ni and granite poor in these metals. Additionally, concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were measured in granite and serpentinite parent rocks, soils, and in P. aquilinum (rhizome and fronds). The experiment was carried out with rhizomes of ferns from both types of soils placed in pots supplemented with 50, 100, and 250 mg kg−1 of Cr or Ni or both elements together. At a concentration of 250 mg kg−1 of Cr, Ni, or Cr + Ni, fronds (from granite or serpentinite origin) contained significantly higher Cr and Ni concentrations when both metals were supplied together. In the same concentration of 250 mg kg−1 of Cr, Ni, or Cr + Ni, rhizomes (from granite or serpentinite origin) contained significantly higher Cr and Ni concentrations when both metals were supplied separately. The explanation of metal differences in the joint accumulation of Cr and Ni on the rhizome or frond level needs further investigation. The lack of difference in Cr and Ni concentration in the rhizome and fronds between experimental P. aquilinum collected from granite and serpentinite soils may probably indicate that the phenotypic plasticity of this species is very important in the adaptation to extreme environments.

Assessment of selected sequential extraction and the toxicity characteristic leaching test as indices of metal mobility in serpentinite soils

Serpentinite soils are characterised by high concentrations of chromium, nickel, and cobalt. The accumulation of heavy metals as non-degradable inorganic contaminants is of great concern. Under normal circumstances the form in which a metal exists governs its transport in the environment and thus, its hazards. In this study, a specific developed speciation analysis for tropical soils was applied to determine the mobility of Cr, Ni and Co in two serpentinitic soil outcrops in Malaysia. The combination of selective sequential extraction analysis (SEE) and X-ray diffraction of soil powders showed that Cr and Ni are primarily associated with the residual fraction of soil which is inherited from resistant silicates. The crystalline Fe-oxide fraction of soil is the second substanial scavenger of Cr and Ni, whilst the dynamics of Co are mostly controlled by Mn-oxide and the poor crystalline Fe-oxide. The more easily mobilised forms of the studied metals carried on soluble-exchangeable, surface adsorbed and organic matter fractions are of minimal compartments. Therefore these metals are basically not available in the environment. On the other hand, corroborating information on the mobility of the metals was gained by applying the toxicity characteristic leaching procedure test (TCLP). The consistent results of the TCLP with the SSE revealed the non-toxic effects of Cr, Ni and Co in the environment despite their overload accumulation in the analysed serpentinite soils.

Phosphorus and trace metals in serpentine-affected soils of the Sumas Basin, British Columbia

Baugé, S. M. Y., Lavkulich, L. M. and Schreier, H. E. 2013. Phosphorus and trace metals in serpentine-affected soils of the Sumas Basin, British Columbia. Can. J. Soil Sci. 93: 359–367. Soils of the Sumas watershed in the Lower Fraser Valley of British Columbia have contrasting P, Mg and trace elements contents arising from two major sources, periodic deposition of serpentine-rich sediments and intensive agricultural activities. Four study sites were examined for soil P by several extractants commonly used for P availability assessments. The results were compared with aqua regia to determine best estimates of extractable P. In addition, these extractants were evaluated as indices of associated trace metal amounts. Aqua regia, acid ammonium oxalate and 1 M HCl extracted similar amounts of P and trace metals. Acid ammonium oxalate was found to be closely related to the estimates of total P and recoverable elements, followed by 1 M HCl. There was clear separation of the sites by both P values and trace elements associated with serpentine (Cr and Ni) and those from agricultural activities (Cu and Zn). Results suggest that a single extraction, 1 M HCl, can be an effective measure of both available P and trace elements in serpentinitic soils.

Pedogeochemical characteristics of chromite in a paddy soil derived from serpentinites

Chromite is a primary Cr-bearing mineral in serpentinitic soil; therefore, these soils generally contain a high concentration of Cr, which causes a potential risk to human health after Cr is mobilized by chromite weathering into the environment. This study examined the micromorphological characteristics of chromite and identified chromite weathering as a source of Cr in a paddy soil profile derived from serpentinites in Eastern Taiwan. The soil samples were tested by partitioning Cr in the bulk soil and measuring the element composition in the chromite. The fractionation of Cr in all soil horizons was performed using a selective sequential procedure (SSE). The SSE results demonstrated that the original Cr was primarily fixed in the recalcitrant minerals of the serpentinitic soils. However, labile Cr fractions were also clearly observed in the soils. During chemical weathering, Cr(III) was released from hydrolysis in chromite under the submergence of the pedon, whereas Cr(VI) examined using XANES spectra was absent in the soils. The micromorphological observation using polarized-light microscopic and SEM-BSE images indicated that chromite was altered, which corresponded to the increase of labile Cr toward the surface soil. In the chromite grain, Cr decreased with the increase of Fe and decrease of Al, Mn, Mg, and Zn during pedogenesis. Chromite acted as a source of Cr through dissolution in the pedon.

Elemental composition of phytoliths in modern plants (Ericaceae)

Plants accumulate opaline silica in the form of phytoliths. Species and availability of Si are the main factors that determine the phytolith content in plants. Therefore, several Ericaceae species were tested in different soils. Erica andevalensis is restricted to grow in acid- and metal-enriched soils in the Iberian Pyritic Belt, and therefore it is particularly suitable to study the effects of metals on the phytolith composition. Ericaceae that originate from soils in mining areas were compared with those from unpolluted areas. Species from mining areas included E. andevalensis (Riotinto mines, Andalucía, SW Spain), Erica australis and Calluna vulgaris (Touro mine Galicia, NW Spain). For the unpolluted areas, C. vulgaris was collected on peat (Sapric Histosol), quartzite (Albic Podsol) and serpentinite (Mollic Gleysol) soils. The abundance and elemental composition (Ca, Mg, Al, Fe, Mn, Cu, Zn, Cr, Ni, Pb and As) of phytoliths in leaves were analyzed. Elemental quantification by means of Energy-dispersive Miniprobe Multielement Analyzer (EMMA-XRF) is an innovative method for elemental analysis of phytoliths. Both the highest leaf phytolith production and elemental concentration were found in species from mine soils, with the highest phytolith contents for C. vulgaris and highest concentration of elements (Ca, Fe, Mn, Cu, Zn, Pb and As) for E. andevalensis. The highest Cr and Ni concentration in phytoliths was found on serpentinite soils. The lowest values of phytoliths and metal concentrations were found in heathers from quartzite and peaty soils.The abundance of phytoliths agreed with the availability of Si in the studied soils and its elemental composition reflected the geochemical conditions. The results presented here suggest that phytoliths act as alleviates of metal stress in heathers.

Topographic and soil differences from peridotite to serpentinite

Pedologists commonly lump peridotite and serpentinite soils together without reporting differences between them. Peridotite and serpentinite are chemically similar, but mineralogically quite different. A detailed soil survey in which soils with peridotite and serpentinite parent materials were separated in mapping revealed appreciable differences in geomorphic and pedologic features between these two types of ultramafic rocks. In mountainous terrain of the Klamath Mountains, California and Oregon, slopes tend to be steeper on peridotite and the soils redder. More Luvisols (Alfisols) were found on peridotite and more Phaeozems (Mollisols) on serpentinite. Very shallow soils (7% of the area), which are Leptosols (mostly Mollisols and Entisols, few Alfisols), are more common on serpentinite. Sparsely vegetated barrens are commonly fragmental colluvium (talus) on peridotite and erodible, slightly to moderately stony summits and sideslopes on serpentinite. Large landslides are much more extensive in serpentinite terrain. Vegetative cover differences from peridotite to serpentinite are much less pronounced than the topographic and soil differences; the plant differences are obvious only on shallow soils.