Cytotoxicity of fibrous antigorite from New Caledonia.

Exposure to asbestos and asbestos-like minerals has been related to the development of severe lung diseases, including cancer and malignant mesothelioma (MM). A high incidence of non-occupational MM was observed in New Caledonia (France) in people living in proximity of serpentinite outcrops, containing chrysotile and fibrous antigorite. Antigorite is a magnesium silicate, which shares with chrysotile asbestos the chemical formula. To achieve information on antigorite toxicity, we investigated the physico-minero-chemical features relevant for toxicity and cellular effects elicited on murine macrophages (MH-S) and alveolar epithelial cells (A549) of three fibrous antigorites (f-Atg) collected in a Caledonian nickel lateritic ore and subjected to supergene alteration. Field Atg were milled to obtain samples suitable for toxicological studies with a similar particle size distribution. UICC chrysotile (Ctl) and a non-fibrous antigorite (nf-Atg) were used as reference minerals. A high variability in toxicity was observed depending on shape, chemical alteration, and surface reactivity. The antigorites shared with Ctl a similar surface area (16.3, 12.1, 20.3, 13.4, and 15.6 m2/g for f-Atg1, 2, 3, nf-Atg, and Ctl). f-Atg showed different level of pedogenetic weathering (Ni depletion f-Atg1 ≪ f-Atg2 and 3) and contained about 50% of elongated mineral particles, some of which exhibited high aspect ratios (AR > 10 µm, 20%, 26%, 31% for f-Atg1, 2, and 3, respectively). The minerals differed in bio-accessible iron at pH 4.5 (f-Atg1 ≪ f-Atg3, < f-Atg2, nf-Atg < Ctl), and surface reactivity (ROS release in solution, f-Atg1 ≪ f-Atg2, 3, nf-Atg, and Ctl). f-Atg2 and f-Atg3 induced oxidative stress and pro-inflammatory responses, while the less altered, poorly reactive sample (f-Atg1) induced negligible effects, as well nf-Atg. The slow dissolution kinetics observed in simulated body fluids may signal a high biopersistence. Overall, our work revealed a significative cellular toxicity of f-Atg that correlates with fibrous habit and surface reactivity.

Influences of species and watersheds inputs on trace metal accumulation in mangrove roots.

Mangrove forest is a key ecosystem between land and sea, and provides many services such as trapping sediments and contaminants. These contaminants include trace metals (TM) that can accumulate in mangroves soil and biota. This paper innovates by the comparative study of the effects of the watershed inputs on TM distribution in mangrove soil, on roots bioconcentration factors of two species (Avicennia marina and Rhizophora stylosa), and on Fe plaque formation and immobilization of these TM. Two mangrove forests in New Caledonia were chosen as study sites. One mangrove is located downstream ultramafic rocks and a Ni mine (ultrabasic site), whereas the second mangrove ends a volcano-sedimentary watershed (non-ultrabasic site). TM concentrations (Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn) were measured in soil, porewaters, and roots of both species via ICP-OES or Hg analyzer. Analyzed TM were significantly more concentrated in soils at the ultrabasic site with Fe, Cr, and Ni the most abundant. Iron, Mn, and Ni were the most concentrated in the roots with mean values of 9,651, 192, and 133 mg kg-1 respectively. However, the bioconcentration factors (BCF) of Fe (0.16) and Ni (0.11) were low due to a lack of ions in the dissolved phase and potential uptake regulation. The uptake of TM by mangrove trees was influenced by concentrations in soil, but more importantly by their potential bioavailability and the physiological characteristics of each species. TM concentrations and BCF were lower for R. stylosa probably due to less permeable root system. A. marina limits TM absorption through Fe plaque formation on its pneumatophores with a capacity to retain TM up to 94% for Mn. Mean Fe plaque formation is potentially correlated to Fe concentration in soil. Eventually, framboids of pyrite were observed within root tissues in the epidermis of A. marina's pneumatophores.

Mobility of Ni, Co, and Mn in ultramafic mining soils of New Caledonia, assessed by kinetic EDTA extractions.

The aim of this study was to determine the mobilization capability of Ni, Co, and Mn contained in New Caledonian ultramafic soils. Two series of soils were sampled: bare-surface mining soils in a Ni-mining context (n = 10), and forest soils, either in the vicinity of mine-working areas (n = 3) or far away from any known mining activity (n = 2). We focused on the < 100 µm soil fraction, because of its sensitivity to wind erosion, and its possible dissemination toward urbanized areas. In order to assess maximum potential metal mobility, EDTA kinetic extractions were performed over 24 h. Extraction curves were modeled as the sum of two first-order reactions. The first EDTA extracted pool corresponds to "quickly" released metals, while the second pool corresponds to "slowly" released metals. The remaining fraction is the EDTA non-extractable pool. Extractable Ni, Co, and Mn were always low in relation to total concentrations (< 5% for Ni, and 5-35% for Co and Mn). The extraction rate of the less labile pool was significantly higher for forest soils than for mining soils, whatever the metal. Despite the greater extractability potential in forest surface soils, mining soils represent a bigger environmental risk, because of their high metal content and, above all, because of their predisposition to surface runoff and eolian deflation.

Impact of nickel mining in New Caledonia assessed by compositional data analysis of lichens.

The aim of this study is to explore the use of lichens as biomonitors of the impact of nickel mining and ore treatment on the atmosphere in the New Caledonian archipelago (South Pacific Ocean); both activities emitting also Co, Cr and possibly Fe. Metal contents were analysed in thirty-four epiphytic lichens, collected in the vicinity of the potential sources, and in places free from known historical mining. The highest Ni, Co, and Cr concentrations were, as expected, observed in lichens collected near ore deposits or treatment areas. The elemental composition in the lichens was explored by multivariate analysis, after appropriately transforming the variables (i.e. using compositional data analysis). The sample score of the first principal component (PC1) makes the largest (positive) multiplicative contribution to the log-ratios of metals originating from mining activities (Ni, Cr, Co) divided by Ti. The PC1 scores are used here as a surrogate of pollution levels related to mining and metallurgical activity. They can be viewed as synthetic indicators mapped to provide valuable information for the management and protection of ecosystems or, as a first step, to select locations where air filtration units could be installed, in the future, for air quality monitoring. However, as this approach drastically simplifies the problem, supplying a broadly efficient picture but little detail, recognizing the different sources of contamination may be difficult, more particularly when their chemical differences are subtle. It conveys only relative information: about ratios, not levels, and is therefore recommended as a preliminary step, in combination with close examination of raw concentration levels of lichens. Further validation using conventional air-monitoring by filter units should also prove beneficial.

Alternative dry separation of PM10 from soils for characterization by kinetic extraction: example of new Caledonian mining soils.

A simple new device for dry separation of fine particulate matter from bulk soil samples is presented here. It consists of a stainless steel tube along which a nitrogen flow is imposed, resulting in the displacement of particles. Taking into account particle transport, fluid mechanics, and soil sample composition, a tube 6-m long, with a 0.04-m diameter, was found best adapted for PM10 separation. The device rapidly produced several milligrams of particulate matter, on which chemical extractions with EDTA were subsequently performed to study the kinetic parameters of extractable metals. New Caledonian mining soils were chosen here, as a case-study. Although the easily extracted metal pool represents only 0.5-6.4 % of the total metal content for the elements studied (Ni, Co, Mn), the total concentrations are extremely high. This pool is therefore far from negligible, and can be troublesome in the environment. This dry technique for fine particle separation from bulk parent soil eliminates the metal-leaching risks inherent in wet filtration and should therefore ensure safe assessment of environmental quality in fine-textured, metal-contaminated soils.