Ultramafic Areas Research Articles

Integrating environmental, ecological and human health risk assessments for heavy metals in tropical ultramafic soils

Ultramafic soils are a natural source of metals such as Ni, Co and Cr that can pose ecosystem and human risks. Here, we assessed the environmental, ecological, and human health (carcinogenic and non-carcinogenic) risks from exposure to ultramafic soils through an integrated approach using petrographic and soil mineralogical assessments together with total, available, bioaccessible, and soil fractions analyses of Ni, Co and Cr in ultramafic soils from Brazil. The metal concentrations were similar or up to 5-fold higher for Ni than other studies worldwide in ultramafic soils. Soil sequential extraction showed Co and Ni predominantly bound to Fe and Mn oxides, while Cr was mostly in residual fractions. Medium environmental risks were found for Ni (RAC = 13.0), but no environmental risks were associated with Co and Cr in soils. Ecological risks were high (PERI = 522.8) and significantly high (PERI = 1759.9). Low metal bioaccessibility led to acceptable carcinogenic and non-carcinogenic risks for all routes of human exposure to soil, but consuming vegetables grown in these soils posed unacceptable cancer risks (> 10−3). Our results reinforce the need to monitor ultramafic areas regarding the mobility and availability of metals in the soil to ensure food safety and human health.

Effect of soil additives on biogeochemistry of ultramafic soils—an experimental approach with Brassica napus L

Ultramafic soils are characterized by low productivity due to the deficiency of macroelements and high content of Ni, Cr, and Co. Incorporation of ultramafic soils for agricultural and food production involves the use of fertilizers. Therefore, this study aims to find the soil additive that decreases the metallic elements uptake by plant using Brassica napus as an example. In this study, we evaluate the effect of manure (0.5 g N/kg of soil), humic acids (1 g of Rosahumus/1 dm3 H2O; 44% C), KNO3 (0.13 g K/kg of soil), lime (12.5 g/kg of soil), (NH4)2SO4 (0.15 g N/kg of soil), and Ca(H2PO4)2) (0.07 g P/kg of soil) on the phytoavailability of metallic elements. The effect of soil additives on metallic elements uptake by Brassica napus was studied in a pot experiment executed in triplicates. Statistical analysis was applied to compare the effects of additives in ultramafic soil on plant chemical composition relative to control unfertilized ultramafic soil (one-way ANOVA and Kruskal–Wallis test). The study shows that in almost all treatments, metallic elements content (Ni, Cr, Co, Al, Fe, Mn) is higher in roots compared to the aboveground parts of Brassica napus except for (NH4)2SO4, in which the mechanism of Mn accumulation is opposite. The main differences between the treatments are observed for the buffer properties of soil and the accumulation of specific metals by studied plants. The soils with the addition of lime and manure have the highest buffer properties in acidic conditions (4.9-fold and 2.1-fold increase relative to control soil, respectively), whereas the soil with (NH4)2SO4 has the lowest effect (0.8-fold decrease relative to control soil). Also, the addition of manure increases the biomass of aboveground parts of B. napus (3.4-fold increase) and decreases the accumulation of Ni (0.6-fold decrease) compared to plants cultivated in the control soil. On the contrary, the addition of (NH4)2SO4 noticeably increases the accumulation of Ni, Co, Mn, and Al in aboveground parts of B. napus (3.2-fold, 18.2-fold, 11.2-fold, and 1.6-fold, respectively) compared to plant grown in control soil, whereas the humic acids increase the accumulation of Cr in roots (1.6-fold increase). Therefore, this study shows that manure is a promising fertilizer in agricultural practices in ultramafic soil, whereas (NH4)2SO4 and humic acids must not be used in ultramafic areas.

Rooted Cutting of Gymnostoma Sumatranum for Land Reclamation in Degraded Ultramafic Forests in Sabah

Gymnostoma sumatranum, a member of the Casuarinaceae family, is a resilient tree species well-adapted to nutrient-deficient soils. In Sabah, it stands out among the three widely distributed Casuarinaceae species, holding promise for land reclamation initiatives in degraded ultramafic forests. This comprehensive study addresses three primary objectives for effective G. sumatranum propagation, 1) sprig selection for rooted cutting, 2) impact of commercial rooting hormones on growth and nodulation, and 3) identification of suitable potting media for seedling development. The results indicated that the middle-part sprig is preferable for rooted cutting, with a higher rooting percentage (75.9%) compared to the upper-part sprig (57.5%). Additionally, the use of Seradix-3 as a growth hormone treatment yields significant improvements in explant length and root production. However, variations in root nodulation, influenced by different treatments, suggested limitations in commercial rooting hormones, with only 31% of rooted explants exhibiting nodulation. This underscores the need for further research to comprehend factors influencing nodulation in this context. In terms of potting media, river sand (R-sand) emerges as the most effective for G. sumatranum seedling development in the nursery stage based on S-index (healthy seedlings = 31.5%) and growth index (Height = 51.14±14.82 mm; N-Branch = 51.14±14.82), emphasising the critical role of proper potting medium selection for optimal seedling growth and survival. The study also highlights previous restoration efforts by the Sabah Forestry Department, utilising G. sumatranum and other pioneer species to restore degraded ultramafic areas in Sabah. Overall, these results contribute to the long-term goal of restoring the functioning capacity of valuable ultramafic ecosystems and promoting sustainable reforestation practices.

Grassland flora of ultramafic areas in Northern Pindus (Greece)

AbstractIn Europe, the largest and most floristically diverse ultramafic (serpentine) outcrops are located on the Balkan Peninsula. In Greece, the Northern Pindus mountain range is characterized as a floristic diversity hotspot, due to the presence of large ultramafic outcrops that harbor a large number of nickel (Ni) hyperaccumulators with potential use in agromining. The work presented here is part of a more in‐depth study of floristic composition and ecology of plant communities in ultramafic grasslands of the Northern Pindus mountain range. In 2021–2022, 120 relevés in three subareas (sA1, sA2, and sA3) were sampled according to the Braun‐Blanquet method. We identified 493 plant taxa belonging to 61 families. The most abundant families were Asteraceae, Poaceae, Fabaceae, Lamiaceae, and Caryophyllaceae. A total of 22 plant taxa are endemic to Greece. Ninety‐five taxa are of Balkan origin while 158 taxa are distributed to the broader Mediterranean region. The highest number of plant life‐forms are hemicryptophytes (56.39%) and therophytes (23.33%). Eight Ni hyperaccumulators including Centaurea thracica, Bornmuellera baldaccii, Bornmuellera emarginata, Bornmuellera tymphaea, Noccaea boeotica, Noccaea tymphaea, Odontarrhena chalcidica, and Odontarrhena smolikana were recorded.

The discovery and global distribution of hyperaccumulator plants: A personal account

AbstractAn instance of extreme accumulation of Zn by a plant species was found in the 19th century, and observations of unusually high concentrations of other elements (Cu, Co, Ni, Cd, Pb, As, Se) were recorded between the 1920s and 1970s. Of relevance to the study of ultramafic areas and their floras is the occurrence of extreme Ni accumulation. The term “hyperaccumulator” was introduced in 1976 to signify a species exhibiting a concentration that can be hundreds or thousands of times greater than that usually found in plants on most common soils. Concentration criteria that allow a species to be regarded as a hyperaccumulator have been defined and refined from time to time. The following account details my own involvement in the discovery of new examples of metal hyperaccumulation, with particular emphasis on Ni accumulation by plants of ultramafic floras worldwide. The interest in hyperaccumulators has prompted investigations into different aspects of the biota of metalliferous soils. The search for new examples of hyperaccumulation continues, aided in part by non‐destructive X‐ray fluorescence scanning of herbarium specimens, which previously served as a resource providing small fragments for sensitive but destructive analysis. Identification of species as hyperaccumulators must be supported by further field exploration to understand the factors governing the level of metal uptake, and to stimulate further work on plant systematics, biochemistry, genetics, and molecular biology. Applications to phytoremediation and agromining are worth pursuing in some cases. Conservation issues are important because many hyperaccumulators are rare and restricted in their distribution.

Nitrogen Rather Than Phosphorus Limits the Productivity of the Dominant Tree Species at Mine-Disturbed Ultramafic Areas in the Southern Philippines

Understanding the stoichiometry of nitrogen (N) and phosphorus (P) plays a pivotal role in the ecological restoration of degraded landscapes. Here, the N and P limitation and stoichiometry of dominant tree species in mine-disturbed ultramafic areas in the Southern Philippines are reported. Field surveys revealed that out of a total of 1491 trees/shrubs recorded from all quadrats, comprising 22 native and 9 non-native species, there were six tree species (native: Alstonia macrophylla Wallich., Buchanania arborescens Blume., Syzygium sp., and non-native: Casuarina equisetifolia L., Terminalia catappa L. and Acacia mangium Wild.) that were found dominant, having >10% relative abundance. Significant differences (p < 0.01) in the leaf N and leaf P content among these species were observed, where C.equisetifolia (due to N fixation ability) and T. catappa had the highest values, respectively. These did not, however, translate to statistical differences in the leaf N:P ratios either in individual species or when grouped by origin (native or non-native). Interestingly, all dominant tree species revealed very low leaf N:P ratios (<4), suggesting that N rather than P limits the productivity in mine-disturbed ultramafic areas, which is also confirmed by low levels of leaf N (<2.0%). Results further revealed a poor correlation between leaf N and leaf N:P ratios (r = 0.13; p = 0.60), while leaf P (r = 0.49; p < 0.05) revealed otherwise, reinforcing that P is not a limiting factor as also shown in high levels of leaf P (>0.20%). Despite the N-limitation, B. arborescens, C. equisetifolia, and T. catappa had the highest leaf N and P content, suggesting their higher suitability for revegetation of the sites. These findings warrant further verification taking into account the plant physiology, phenology, and soil nutrient availability in natural, degraded, and rehabilitated ultramafic environments.

Metal accumulation by Alyssum serpyllifolium subsp. malacitanum Rivas Goday (Brassicaceae) across different petrographic entities in South-Iberian ultramafic massifs: plant-soil relationships and prospects for phytomining

In the ultramafic area of Spain, a high quantity of petrographic entities is present. Data on the variability among populations of hyperaccumulation are scarce. We investigated Alyssum serpyllifolium subsp. malacitanum for variations in eleven elements among populations growing in different ultramafic massifs in different petrographic entities (dunites, harzburgite-pyroxenic dunite, harzburgite-lherzolite, pyroxenite, and serpentinites). Samples of leaves and soils were collected from the ultramafic outcrops of Sierra Bermeja and Sierra de Mijas (Andalusia, Spain). The concentrations of Ni, Fe, Mg, Si, Cr, Co, Sr, Mn, Cu, Zn, and Ba and the bioaccumulation factors (BAF) were determined. Although analysis of variance of the data for each element revealed considerable variation in soil chemistry (for Fe, Mg, Sr, and Ba) among the different petrographic entities, population-level variation with regard to the hyperaccumulation in the leaves was not detected. BAF values >1 were obtained for Sr and Ni depending on the petrographic entities. The correlation detected between the concentration of Ni in leaves and concentration in soil is relevant. The population-level variation obtained in the BAF values for Sr and Ni provides comprehensive information on the natural variation of hyperaccumulation. The BAF obtained for Ba is an important result for phytomining. Novelty statement To date, studies of hyperaccumulation in plant tissues on ultramafic rocks have not considered the great diversity of petrographic entities in the world's outcrops. One of them is the one that we studied in Spain with more than eight petrographic entities and different soils. Our hypothesis is that the different chemical compositions of the soils in ultramafic rocks significantly affect the hyperaccumulation of metals by specialized plants, which may have consequences for phytomining. For this purpose, individuals, populations, and different soils have been tested and the results have been subjected to the corresponding statistical tests. The obtained knowledge reflects the different behavior of the studied plant not only for the Ni: the obtained results for Sr and for Ba revealed interesting results for the hyperaccumulation in Alyssum of both metals.

Plants of ultramafic areas in Hokkaido, Japan

Plants of ultramafic areas in Hokkaido, Japan

Tahiti Petrel Pseudobulweria rostrata population decline at a nickel-mining site: a critical need for adapted conservation strategies

SummaryNew Caledonia hosts a large part of the world’s breeding population of the Tahiti Petrel Pseudobulweria rostrata. This rare, cryptic and little-studied seabird nests locally in the mountains up to 1,200 m in altitude, particularly in ultramafic (i.e. nickel-rich) areas where mining activity is a major threat. The considerable development of mining activities in New Caledonia over the past decade raises concerns about its potential impacts on breeding populations through both direct habitat destruction and side effects such as pollution or repeated disturbances. This context calls for a dedicated assessment of the persistence of local populations to guide the design of an adapted conservation strategy and potential restoration programmes. We investigated the impact of mining activities on a Tahiti Petrel population when surveyed pre-mining (2004–2007) and following a period of full mining (2017–2018). The vocal activity was assessed at a total of 114 night-call count stations spread over the Koniambo massif. Areas with ground-originated vocal activity were then searched during daytime for nesting evidence. Finally, georeferenced aerial photos were used to estimate habitat degradation as the percentage of bare soil cover (PBSC) within a 400-m radius around each call count station. Our study revealed a dramatic decline in the Tahiti Petrel vocal activity and a desertion of breeding habitats during the full-mining period compared to the pre-mining period. In light of these results, we recommend designing safe breeding areas and combining restoration methods including social attraction, predation control and artificial burrows at mining sites.

Chromium mobility in ultramafic areas affected by mining activities in Barro Alto massif, Brazil: An isotopic study

This work studies the potential release of Cr from solids to surface water and groundwater, and the related isotopic compositions, in a nickel laterite ore deposit from Barro Alto in Brazil (in the State of Goiás). This ultramafic system is characterized by elevated concentrations of chromium (Cr). Even largely immobile Cr may be naturally leached from weathering profiles such as laterite to the surface and groundwater. This system is exploited for metal production, and both mining and metallurgical activities result in a significant increase in the trivalent (Cr(III)) and hexavalent chromium (Cr(VI)) concentrations released into the environment via runoff. Among all the samples collected, ores contained higher amounts of chemically and isotopically exchangeable Cr(VI) (ECr(VI)) with values as high as 104 (± 8) mg kg−1. δ53Cr increased from −0.28 (± 0.01)‰ to −0.05 (± 0.01)‰ and the ECr(VI) value was up to 30 times higher in deep soils than at the surface (up to 7 (± 1) mg kg−1). Chemically extracted Cr(VI) (ECr(VI)-KH2PO4) displayed positive δ53Cr value (1.69 (±0.03) ‰) with a similar Cr isotopic composition as the ones measured in freshwater sampled in and around the mine area. It appears that Cr is primarily released as Cr(VI), i.e. the toxic species, and becomes increasingly more available as it moves from the soil profile to the ores and mining residues. Based on the differences in the Cr isotopic composition, this study proves that δ53Cr can be used in environmental studies to trace Cr leaching.

Plant Functional Traits on Tropical Ultramafic Habitats Affected by Fire and Mining: Insights for Reclamation

Biodiversity-rich tropical ultramafic areas are currently being impacted by land clearing and particularly by mine activities. The reclamation of ultramafic degraded areas requires a knowledge of pioneer plant species. The objective of this study is to highlight the functional traits of plants that colonize ultramafic areas after disturbance by fire or mining activities. This information will allow trait-assisted selection of candidate species for reclamation. Fifteen plots were established on ultramafic soils in Sabah (Borneo, Malaysia) disturbed by recurrent fires (FIRE plots) or by soil excavation and quarrying (MINE plots). In each plot, soil samples were collected and plant cover as well as species abundances were estimated. Fifteen functional traits related to revegetation, nutrient improvement, or Ni phytomining were measured in sampled plants. Vegetation of both FIRE and MINE plots was dominated by perennials with lateral spreading capacity (mainly by rhizomes). Plant communities displayed a conservative growth strategy, which is an adaptation to low nutrient availability on ultramafic soils. Plant height was higher in FIRE than in MINE plots, whereas the number of stems per plant was higher in MINE plots. Perennial plants with lateral spreading capacity and a conservative growth strategy would be the first choice for the reclamation of ultramafic degraded areas. Additional notes for increasing nutrient cycling, managing competition, and implementing of Ni-phytomining are also provided.

Morais Ultramafic Complex: A Survey towards Nickel Phytomining

Ultramafic areas are critical for nickel (Ni) phytomining due to the high concentration of this element in their soils and the number of hyperaccumulators they harbor. The aim of the present study was to evaluate the potential of the Morais massif, an ultramafic area in Portugal, for phytomining using the hyperaccumulator species Alyssum serpyllifolium subsp. lusitanicum. Soil samples and A. serpyllifolium specimens were collected in four locations of the Morais massif. After determination of Ni concentrations in the samples, the results show that soil pseudo-total Ni concentrations in sites number 1 and 2 are significantly higher than in the soil samples collected in the other two locations, with 1918 and 2092 mg kg−1, respectively. Nickel accumulation is significantly greater in the aerial parts of plants collected at sites 1, 2, and 4, presenting Ni harvestable amount means of 88.36, 93.80, and 95.56 mg per plant, respectively. These results suggest that the sites with highest potential for phytomining are sites 1, 2, and 4. A nickel agromining system in these locations could represent an additional source of income to local farmers, since ultramafic soils have low productivity for agriculture and crop production.

Recovery of ultramafic soil functions and plant communities along an age-gradient of the actinorhizal tree Ceuthostoma terminale (Casuarinaceae) in Sabah (Malaysia)

Background and aims: Pioneer plants may improve the ecological restoration of degraded ultramafic areas by plant-soil interaction processes. In this study, we assess the effect of the pioneer actinorhizal tree C. terminale (Casuarinaceae) on the recovery of plant communities and soil functions on degraded tropical ultramafic sites. Methods: Soil and plant samples were collected along a tree-age gradient in two degraded ultramafic sites in Sabah (Northern Borneo, Malaysia): a Technosol and a Leptosol. Chemical composition of plants and soils, and biological activity of soils were assessed at both sites. Plant colonisation was assessed by plot vegetation surveys. Results: An improvement in soil fertility parameters (pH reduction from 8.5 to 6.8, an increase in the concentrations of several nutrients and enhanced soil enzyme activities) was observed along the C. terminale age gradient. However, plant cover and diversity was only improved around mature trees at the site that was not impacted by mining. Conclusion: C. terminale promotes the recovery of several soil functions, mainly related to the storage and recycling of N, P, K, S. Besides plant-soil feedback, other environmental factors (i.e. exposition to sunlight, drought) may play an important role on revegetation of ultramafic soils.

Metal accumulation by the ultramafic flora of Kosovo

AbstractThe largest serpentine outcrops in Europe occur in the Balkan Peninsula. Kosovo, as a part of this region, hosts an ultramafic area of 487 km2 within its territory. This work reports the first systematic biogeochemical survey on the significant and most representative ultramafic massifs of Kosovo. The aim of this study was (i) to detail the geochemical composition of 12 ultramafic pedons obtained from 10 selected sites chosen as representative for Kosovo, (ii) to inventoriate the flora occurring on these sites and (iii) to identify plant species with potential for use in phytostabilization or phytoextraction purposes. Twelve representative pedons from 10 different sites across the country were excavated and 27 horizon samples were collected. Regarding the serpentine flora, a total of 162 plant taxa located at the ultramafic sites were collected. Soils samples were characterized for basic physico‐chemical characteristics and both plant and soil samples were analyzed for chemical composition. The serpentine soils samples displayed a vast array of physico‐chemical characteristics which reflected the geochemistry of the bedrock, the degree of weathering and the horizon characteristics. However there appeared to be a relationship between edaphic properties and the occurrence of several plant species. Although most of the plants’ species did not show metal concentrations above 1000 mg kg−1, Odontarrhena muralis (syn. Alyssum murale Waldst. and Kit). and Noccaea ochroleuca (Boiss and Heldr.) F.K.Mey. (syn. Thlaspi ochroleucum), did, thus meeting the criterion of Ni hyperaccumulating plants. Given the aforementioned, the resilience of these plants to both tolerate and accumulate heavy metals may prove useful for phytostabilization,

Metal hyperaccumulating Brassicaceae from the ultramafic area of Yahyalı in Kayseri province, Turkey

AbstractMany of the plants found in serpentine areas are endemics and they may accumulate Ni at high concentration. High accumulation of Cr is rare, or in some views, never properly demonstrated. Generally, a very small proportion of any serpentine flora shows high accumulation of Ni, in some serpentine areas Ni accumulators are completely absent. There are approximately 570 hyperaccumulator plant species found on earth, 450 of them are Ni hyperaccumulators. A few of the Ni accumulators have potential for phytoremediation or phytomining. In the present study, 19 different Brassicaceae members growing in serpentine habitats in the district of Yahyalı, Kayseri province, Turkey viz., members of genera Aethionema, Alyssum, Arabis, Heldreichia, Hesperis, Iberis, Isatis, Microthlaspi, Odontarrhena, Pseudosempervivum and Thlaspi were investigated. Nickel concentrations in the soil and underground and aboveground parts of plants were determined by using ICP‐OES. It was observed that Ni concentrations of seven taxa (Odontarrhena muralis, O. oxycarpa, Isatis cappadocica subsp. cappadocica, Microthlaspi perfoliatum, Pseudosempervivum sempervivum, Thlaspi triangulare, Thlaspi rosulare) reach the threshold criterion of 1,000 mg kg−1 for Ni hyperaccumulation. In this study Ni concentrations in aboveground tissues of I. cappadocica subsp. cappadocica are determined as 5,587 mg kg−1 (in dry weight). Accordingly, it is suggested that this taxon be added to the list of Ni hyperaccumulator plants.

Diversity and functional traits of lichens in ultramafic areas: a literature‐based worldwide analysis integrated by field data at the regional scale

AbstractWhile higher plant communities found on ultramafics are known to display peculiar characteristics, the distinguishability of any peculiarity in lichen communities is still a matter of contention. Other biotic or abiotic factors, rather than substrate chemistry, may contribute to differences in species composition reported for lichens on adjacent ultramafic and non‐ultramafic areas. This work examines the lichen biota of ultramafics, at global and regional scales, with reference to species‐specific functional traits. An updated world list of lichens on ultramafic substrates was analyzed to verify potential relationships between diversity and functional traits of lichens in different Köppen–Geiger climate zones. Moreover, a survey of diversity and functional traits in saxicolous communities on ultramafic and non‐ultramafic substrates was conducted in Valle d'Aosta (North‐West Italy) to verify whether a relationship can be detected between substrate and functional traits that cannot be explained by other environmental factors related to altitude. Analyses (unweighted pair group mean average clustering, canonical correspondence analysis, similarity‐difference‐replacement simplex approach) of global lichen diversity on ultramafic substrates (2314 reports of 881 taxa from 43 areas) displayed a zonal species distribution in different climate zones rather than an azonal distribution driven by the shared substrate. Accordingly, variations in the frequency of functional attributes reflected reported adaptations to the climate conditions of the different geographic areas. At the regional scale, higher similarity and lower species replacement were detected at each altitude, independent from the substrate, suggesting that altitude‐related climate factors prevail over putative substrate–factors in driving community assemblages. In conclusion, data do not reveal peculiarities in lichen diversity or the frequency of functional traits in ultramafic areas.

Is metal hyperaccumulation occurring in ultramafic vegetation of central and southern Mexico?

AbstractIn Mexico, ultramafic complexes are present in different regions from the northwest (Baja California Norte) to the southeast (Chiapas). In this paper, we present the results of the exploration of three ultramafic (serpentine) habitats in central and southern Mexico: Cuicatlán–Concepción Pápalo (Oaxaca), Tehuitzingo–Tecomatlán (Puebla), and San Juan de Otates (Guanajuato). Previous geology studies showed that these complexes are mainly made up of serpentinized peridotites. Soil analyses demonstrated typical ultramafic characteristics such as high content of Mg in relation to Ca, and high concentrations of Fe, Cr, Co, and Ni. Soil samples from Oaxaca and Puebla had similar Ni contents around 2300 mg kg−1, while samples of Guanajuato showed the lowest Ni levels with an average of 200 mg kg−1 as well as for other metals such as Co, Cr, Mn, and Zn. During this study, 83 plant specimens were collected, of which 52 were identified at genus level and 40 at species level. The collected plants belong to 19 different families such as Anacardiaceae, Fabaceae, Acanthaceae, Asteraceae, Sterculiaceae, and Verbenaceae which are also widely present in other ultramafic areas in Iran, Brazil, Sri Lanka, and Costa Rica. Only two Mexican endemic species are included in the collection. Ni hyperaccumulators were not detected at any of the studied sites. Therefore, hyperaccumulation, as a tolerance mechanism of the flora in response to ultramafic geochemical stress, does not seem to be developed in Central Mexico, as observed in the close Costa Rican site of Santa Elena.

Elevated concentrations of naturally occurring heavy metals inversely correlate with reproductive output and body mass of the KaguRhynochetos jubatus

To assess the effects of naturally occurring heavy metals on wild birds, we compared reproductive success and heavy metal contents in feathers of Kagu Rhynochetos jubatus living on ultramafic (rich in heavy metals) soil with those of Kagu living on non-ultramafic soil. From 2003 to 2016, we monitored breeding of 19 Kagu families by radiotracking and video-monitoring, and collected rump down feathers from 69 wild Kagu. The metal concentrations in Kagu feathers correlated with the concentrations in the soil. The mean numbers of eggs laid and fledglings per year of Kagu families on non-ultramafic soil were about four times higher, and home-ranges three times smaller, than those of Kagu on ultramafic soil. Mass of eggs and the proportion of eggs that developed to fledglings were similar in the two areas, whereas the mass of adult Kagu on non-ultramafic soil was nearly 10% higher than that of adult Kagu living on ultramafic soil. The impact of naturally occurring heavy metals on Kagu breeding productivity and body mass appears to act through their effects on food supply rather than being caused directly by metal toxicity. The results imply that conservation of Kagu might be more effective in non-ultramafic areas, as populations can recover much faster on these soils and Kagu can then recolonize and bolster populations in ultramafic areas.

Occurrence, Origin and Transformation Processes of Geogenic Chromium in Soils and Sediments

Weathering of ultramafic rocks has been linked to the occurrence of elevated concentrations of hexavalent chromium (Cr(VI)) in soils, sediments, and groundwater. Ultramafic rocks and the derived serpentine soils and sediments are encountered in populated areas around the world and present high Cr concentrations, with an average of 2200 and 2650 mg/kg for rocks and soils, respectively. Groundwater concentrations between 0.2 and 180 μg/L have been reported for Cr(VI) in ultramafic areas, exceeding occasionally the most prevalent drinking water limit of 50 μg/L Crtot, the 5 μg/L Cr(VI) limit established in Italy, and the 10 μg/L Cr(VI) limit proposed in California. Cr release in groundwater occurs through the dissolution of trivalent chromium (Cr(III)) from its mineral hosts, followed by sorption of Cr(III) onto high-valence Mn oxides and oxidation to Cr(VI), which desorbs and is mobile at alkaline pH. Recent findings indicate that hydrogen peroxide and birnessite produced on the surface of Cr(OH)3 by heterogeneous oxidation are two additional potential mechanisms. Thus, groundwater concentrations are controlled by a variety of geoenvironmental factors, including climate, soil mineralogy, pH, organic matter, and others. To provide a basis for the evaluation of Cr mobility in ultramafic environments, this paper presents an overview of the mineralogy and geochemistry of Cr-rich rocks, sediments, and soils, along with the weathering and geochemical processes that control the fate and transport in the subsurface.

Two new species and three new combinations in Cyperaceae of New Caledonia and Australia

Two new species of Cyperaceae endemic to the ultramafic area of southern New Caledonia are described: Chorizandra gigantea J.Raynal ex K.L.Wilson and Schoenus rivularis J.Raynal ex K.L.Wilson. New combinations are made for three species of Cyperaceae in Australia and New Caledonia: Machaerina johnsonii (K.L.Wilson) K.L.Wilson, M. planifolia (Benth.) K.L.Wilson and M. veillonis (J.Raynal) K.L.Wilson