International audience | The role of land use on fate of metals in soils is poorly understood. In this work, we studied the incorporation of lead in two neighboring soils with comparable pedogenesis but under long-term different agricultural management. Distributions of anthropogenic Pb were assessed from concentrations and isotopic compositions determined on bulk horizon samples, systematical 5–10 cm increment samples, and on 24-h EDTA extracts. Minor amounts of anthropogenic lead were detected until 1-m depth under permanent grassland, linked to high earthworm activity. In arable land, exogenous Pb predominantly accumulated at depths <60 cm. Although the proximity between the two sites ensured comparable exposition regarding atmospheric Pb deposition, the isotopic compositions clearly showed the influence of an unidentified component for the cultivated soil. This work highlights the need for exhaustive information on historical human activities in such anthropized agrosystems when fate of metal pollution is considered.

The increasing use of rare earth elements (REEs) in electric and electronic equipment has been associated with the presence of these elements in aquatic systems. The present study aimed to evaluate the toxicity of two REEs, Lanthanum (La) and Gadolinium (Gd), towards the mussel species Mytilus galloprovincialis. For this, the toxicity was assessed after a short-term exposure (14 days) to an environmentally relevant concentration of each element (10 μg/L), followed by a recovery period (14 days) in the absence of any contaminant. The measured biomarkers included energy-related parameters, activity of antioxidant and biotransformation enzymes, indicators of oxidative damage, levels of oxidized glutathione and neurotoxicity. After exposure mussels accumulated more La (0.54 μg/g) than Gd (0.15 μg/g). After recovery higher concentration decrease was observed for Gd (≈40% loss) compared to La exposed mussels (≈30% loss) which may be associated with lower detoxification capacity of mussels previously exposed to La. Mussels increased their metabolism (i.e., higher electron transport system activity) only after the exposure to Gd. Exposure to La and Gd resulted into lower energy expenditure, while when both elements were removed glycogen and protein concentrations decreased to values observed in non-contaminated mussels. Antioxidant and biotransformation capacity was mainly increased in the presence of Gd. This defense response avoided the occurrence of cellular damage but still loss of redox balance was found regardless the contaminant, which was re-established after the recovery period. Neurotoxicity was only observed in the presence of Gd with no effects after the recovery period. Results showed that a short-term exposure to La and especially to Gd can exert deleterious effects that may compromise specific biochemical pathways in aquatic species, such as M. galloprovincialis, but under low concentrations organisms can be able to re-establish their biochemical status to control levels after a recovery period.

The novel La-MOF@x%PANI composite was synthesized via a two-step procedure with ultra-sonication, and the adsorption mechanism of Pb²⁺ ions from synthetic aqueous solutions was systematically studied. The Pb²⁺ adsorption on the La-MOF@x%PANI was evaluated by the Fourier transform infrared spectroscopy, powder X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray analysis, Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy, and elemental mapping analyses. The effects of the adsorption-influencing parameters, including contact time, solution pH, and co-existing cations on the maximum adsorption capacity of Pb²⁺ onto the prepared composite material were investigated. Moreover, the adsorption of Pb²⁺ ions could be eliminated with rapid adsorption kinetics using the water-stable La-MOF@x%PANI composite. The as-synthesized La-MOF@50%PANI exhibited excellent adsorption performance toward Pb²⁺ ions with an extraordinary adsorption capacity of 185.19 mg/g at pH 6. The Pb²⁺ adsorption onto the La-MOF@x%PANI composite follows the pseudo-second-order kinetics and fits well with the Langmuir isotherm model, indicating the Pb²⁺ adsorption depended on the solution pH as the adsorption mechanism was mainly governed by the electrostatic attraction. Notably, La-MOF@x%PANI composite possesses outstanding regeneration ability and stability after up to four successive cycles. The satisfactory findings reflect that the La-MOF@50%PANI hybrid composite holds a great promise for remediating Pb²⁺ ions from aqueous environments.

Release of phosphorus (P) from sediment to overlying water has to be dealt with to address algal blooms in eutrophic lakes. In this study, the sediment from the Lake Taihu was amended with lanthanum modified zeolite (LMZ) to reduce P release under different pH, temperature and anaerobic conditions. LMZ performed well, to decreasing P concentration in Lake Taihu water in the presence of sediment. The EPC₀ value, the critical P concentration at which there was neither P adsorption nor P release, was lowered by adding LMZ, suggesting that amendment with LMZ could diminish the risk of P release from the sediment. From the Langmuir isotherm model, the adsorption capacity of phosphate by LMZ was estimated to be 64.1 mgP/g. The LMZ-amended sediment had a higher content of stable P forms (HCl-P and Res-P) and a lower content of P forms with a high (NH₄Cl-P and BD-P) or medium-high (NaOH-P and Org-P) risk of release, when compared with the original sediment. The fractionation simulates conditions which release potentially mobile P which can then be simply re-bound to LMZ. At high pH (>9.0), anaerobic condition or high temperature promoted the liberation of P from sediment. However, P release could be greatly inhibited by LMZ. In addition, although Mn²⁺ and NH₄⁺ ions were released from sediment under the anaerobic condition, the release could also be hindered by adding LMZ. LMZ is a promising P inactivation agent to manage eutrophication in the sediment of Lake Taihu.

Lanthanum (La) modified bentonite (LMB) is one of the available mitigating agents used for the reduction of the phosphorus (P) recycling in eutrophic lakes. The potential toxicity of the La from LMB to aquatic organisms is a matter of concern. In this study the accumulation of La was investigated in the macrophyte Elodea nuttallii, in chironomid larvae and in several fish species during periods up to five years following in situ LMB applications. The application of LMB increased the La concentration of exposed plants and animals. During the first growing season following LMB applications, the La content of E. nuttallii increased 78 fold (3.98–310.68 μg La. g−1 DW) to 127 fold (2.46–311.44 μg La. g−1). During the second growing season following application, the La content decreased but was still raised compared to plants that had not been exposed. The La content of chironomids was doubled in the two years following LMB application, although the increase was not significant. Raised La concentrations in fish liver, bone, muscle and skin were observed two and five years following to LMB application. Liver tissues showed the highest La increase, ranging from 6 fold (0.046–0.285 μg La. g−1 DW) to ∼20 fold (0.080–1.886 μg La. g−1, and 0.122–2.109 μg La. g−1) two years following application and from 6 fold (0.046–0.262 μg La. g−1) to 13 fold (0.013–0.167 μg La. g−1) after five years in pelagic and littoral fish. The La content of the liver from Anguilla anguilla (eel) had increased 94 fold (0.034–3.176 μg La. g−1) two years and 133 fold (0.034–4.538 μg La. g−1) five years following LMB application. No acute and chronic effects of La accumulation were observed and human health risks are considered negligible. We advocate the long-term study of effects of La accumulation following future LMB applications.

Both occupational and environmental exposure to asbestos-mineral fibres can be associated with lung diseases. The pathogenic effects are related to the dimension, biopersistence and chemical composition of the fibres. In addition to the major mineral elements, mineral fibres contain trace elements and their content may play a role in fibre toxicity. To shed light on the role of trace elements in asbestos carcinogenesis, knowledge on their concentration in asbestos-mineral fibres is mandatory. It is possible that trace elements play a synergetic factor in the pathogenesis of diseases caused by the inhalation of mineral fibres. In this paper, the concentration levels of trace elements from three chrysotile samples, four amphibole asbestos samples (UICC amosite, UICC anthophyllite, UICC crocidolite and tremolite) and fibrous erionite from Jersey, Nevada (USA) were determined using inductively coupled plasma mass spectrometry (ICP-MS). For all samples, the following trace elements were measured: Li, Be, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Sb, Cs, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U. Their distribution in the various mineral species is thoroughly discussed.The obtained results indicate that the amount of trace metals such as Mn, Cr, Co, Ni, Cu and Zn is higher in anthophyllite and chrysotile samples, whereas the amount of rare earth elements (REE) is higher in erionite and tremolite samples. The results of this work can be useful to the pathologists and biochemists who use asbestos minerals and fibrous erionite in-vitro studies as positive cyto- and geno-toxic standard references.

Phosphorus-inactivating agents (PIAs) as geoengineering tools in lakes have been investigated extensively, but PIA resuspension in the photic layer occurs frequently in shallow lakes and little is known about the influence of algae on PIA performance. Our results proved that algae increased the dissolved oxygen, pH and dissolved organic carbon concentration substantially. In the absence of sediment, lanthanum modified zeolite (LMZ) as a representative PIA and algae could deplete dissolved inorganic phosphorus (DIP) from water but the former was faster than the latter. When LMZ and algae coexisted, the amount of phosphorus that was captured by LMZ was 3.1 times greater than that taken up by algae. An increase in pH or dissolved organic carbon increased the zero-equilibrium phosphorus concentration (EPC₀) of the sediment but LMZ addition could lower the EPC₀ and reduce the risk of phosphorus release during the algal blooming season. In the presence of sediment, LMZ reduced the DIP concentration more rapidly and yielded a lower final DIP concentration compared with algae. In conclusion, the influence of algae on the performance of LMZ by (i) taking up DIP to reduce the availability of DIP and convert DIP into a releasable phosphorus form and (ii) increasing the pH and dissolved organic carbon concentration to hinder the adsorption ability of DIP were recognized. The LMZ performed well, even in the presence of algae.

Potentially toxic elements (PTEs) are of major concern due to their high persistence and toxicity. Recently, rare earth elements (REEs) concentration in aquatic ecosystems has been increasing due to their application in modern technologies. Thus, this work aimed to study, for the first time, the influence of REEs (lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, dysprosium and yttrium) and of salinity (10 and 30) on the removal of PTEs (Cd, Cr, Cu, Hg, Ni and Pb) from contaminated waters by living macroalgae (Fucus spiralis, Fucus vesiculosus, Gracilaria sp., Osmundea pinnatifida, Ulva intestinalis and Ulva lactuca). Experiments ran for 168 h, with each macroalga exposed to saline water spiked with the six PTEs and with the six PTEs plus nine REEs (all at 1 μmol L⁻¹) at both salinities. Results showed that all species have high affinity with Hg (90–99% of removal), not being affected neither by salinity changes nor by the presence of other PTEs or REEs. Cd showed the lowest affinity to most macroalgae, with residual concentrations in water varying between 50 and 108 μg L⁻¹, while Pb removal always increased with salinity decline (up to 80% at salinity 10). REEs influence was clearer at salinity 30, and mainly for Pb. No substantial changes were observed in Ni and Hg sorption. For the remaining elements, the effect of REEs varied among algae species. Overall, the results highlight the role of marine macroalgae as living biofilters (particularly U. lactuca), capable of lowering the levels of top priority hazardous substances (particularly Hg) and other PTEs in water, even in the presence of the new emerging contaminants - REEs. Differences in removal efficiency between elements and macroalgae are explained by the contaminant chemistry in water and by macroalgae characteristics.

Applications of aluminium (Al) salt or lanthanum (La) modified bentonite (LMB) have become popular methodologies for immobilizing phosphorus (P) in eutrophic lakes. The presence of humic substances, has been shown to inhibit this form of treatment due to the complexation with La/Al. However, the effects of other dissolved organic matter (DOM), especially that derived from phytoplankton (the dominant source in eutrophic lakes) are unknown. In this study, the interaction with La/Al of Suwannee River Standard Humic Acid Standard II (SRHA) and algae-derived DOM (ADOM) were investigated and compared. Differed to SRHA which was dominated by polyphenol-like component (76.8%, C1-SRHA), majority in ADOM were protein-like substance, including 41.9% tryptophan-like component (C2-ADOM) and 21.0% tyrosine-like component (C3-ADOM). Two reactions of complexation and coprecipitation were observed between SRHA/ADOM and La/Al. Complexation dominated at low metal inputs less than 10 μM and coprecipitation was the main reaction at higher metal inputs. For ADOM, the tryptophan-like component (C2-ADOM) was the important component to react with metal. The reaction rate for C2-ADOM with La were about two-third of that for C1-SRHA, indicating that the influence of C2-ADOM was significant during the P immobilization by La/Al-based treatment in eutrophic lakes. The P removal data in the presence of ADOM confirmed the significant inhibition of ADOM. In addition, based on the composition of coprecipitates and relatively biodegradable character of tryptophan-like substances (C2-ADOM), the coprecipitation of ADOM was assumed to reduce the stability of precipitated P in eutrophic lakes. The release of P from the potential biodegradation of the coprecipitates and thus the possible decline of the performance of P immobilization by La/Al-based treatments is an important work in the future.