Phytoremediation for co-contaminated soils of chromium and benzo[a]pyrene using Zea mays L.

A greenhouse experiment was carried out to investigate the single effect of benzo[a]pyrene (B[a]P) or chromium (Cr) and the joint effect of Cr–B[a]P on the growth of Zea mays, its uptake and accumulation of Cr, and the dissipation of B[a]P over 60 days. Results showed that single or joint contamination of Cr and B[a]P did not affect the plant growth relative to control treatments. However, the occurrence of B[a]P had an enhancing effect on the accumulation and translocation of Cr. The accumulation of Cr in shoot of plant significantly increased by?≥?79 % in 50 mg kg^?1 Cr–B[a]P (1, 5, and 10 mg kg^?1) treatments and by?≥?86 % in 100 mg kg^?1 Cr–B[a]P (1, 5, and 10 mg kg^?1) treatments relative to control treatments. The presence of plants did not enhance the dissipation of B[a]P in lower (1and 5 mg kg^?1) B[a]P contaminated soils; however, over 60 days of planting Z. mays seemed to enhance the dissipation of B[a]P by over 60 % in 10 mg kg^?1 single contaminated soil and by 28 to 41 % in 10 mg kg^?1B[a]P co-contaminated soil. This suggests that Z. mays might be a useful plant for the remediation of Cr–B[a]P co-contaminated soil.     

Distribution of potentially toxic elements (PTEs) in tailings,soils, and plants around Gol-E-Gohar iron mine,a case study in Iran

This study investigated the concentration of potentially toxic elements (PTEs) including Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, V, and Zn in 102 soils (in the Near and Far areas of the mine), 7 tailings, and 60 plant samples (shoots and roots of Artemisia sieberi and Zygophylum species) collected at the Gol-E-Gohar iron ore mine in Iran. The elemental concentrations in tailings and soil samples (in Near and Far areas) varied between 7.4 and 35.8 mg kg^?1 for As (with a mean of 25.39 mg kg^?1 for tailings), 7.9 and 261.5 mg kg^?1 (mean 189.83 mg kg^?1 for tailings) for Co, 17.7 and 885.03 mg kg^?1 (mean 472.77 mg kg^?1 for tailings) for Cu, 12,500 and 400,000 mg kg^?1 (mean 120,642.86 mg kg^?1 for tailings) for Fe, and 28.1 and 278.1 mg kg^?1 (mean 150.29 mg kg^?1 for tailings) for Ni. A number of physicochemical parameters and pollution index for soils were determined around the mine. Sequential extractions of tailings and soil samples indicated that Fe, Cr, and Co were the least mobile and that Mn, Zn, Cu, and As were potentially available for plants uptake. Similar to soil, the concentration of Al, As, Co, Cr, Cu, Fe, Mn, Mo, Ni, and Zn in plant samples decreased with the distance from the mining/processing areas. Data on plants showed that metal concentrations in shoots usually exceeded those in roots and varied significantly between the two investigated species (Artemisia sieberi > Zygophylum). All the reported results suggest that the soil and plants near the iron ore mine are contaminated with PTEs and that they can be potentially dispersed in the environment via aerosol transport and deposition.     

Bioremediation of Cd and carbendazim co-contaminated soil by Cd-hyperaccumulator Sedum alfredii associated with carbendazim-degrading bacterial strains

The objective of this study was to develop a bioremediation strategy for cadmium (Cd) and carbendazim co-contaminated soil using a hyperaccumulator plant (Sedum alfredii) combined with carbendazim-degrading bacterial strains (Bacillus subtilis, Paracoccus sp., Flavobacterium and Pseudomonas sp.). A pot experiment was conducted under greenhouse conditions for 180 days with S. alfredii and/or carbendazim-degrading strains grown in soil artificially polluted with two levels of contaminants (low level, 1 mg kg^?1 Cd and 21 mg kg^?1 carbendazim; high level, 6 mg kg^?1 Cd and 117 mg kg^?1 carbendazim). Cd removal efficiencies were 32.3–35.1 % and 7.8–8.2 % for the low and high contaminant level, respectively. Inoculation with carbendazim-degrading bacterial strains significantly (P?<?0.05) increased Cd removal efficiencies at the low level. The carbendazim removal efficiencies increased by 32.1–42.5 % by the association of S. alfredii with carbendazim-degrading bacterial strains, as compared to control, regardless of contaminant level. Cultivation with S. alfredii and inoculation of carbendazim-degrading bacterial strains increased soil microbial biomass, dehydrogenase activities and microbial diversities by 46.2–121.3 %, 64.2–143.4 %, and 2.4–24.7 %, respectively. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed that S. alfredii stimulated the activities of Flavobacteria and Bradyrhizobiaceae. The association of S. alfredii with carbendazim-degrading bacterial strains enhanced the degradation of carbendazim by changing microbial activity and community structure in the soil. The results demonstrated that association of S. alfredii with carbendazim-degrading bacterial strains is promising for remediation of Cd and carbendazim co-contaminated soil.     

A combined approach of physicochemical and biological methods for the characterization of petroleum hydrocarbon-contaminated soil

Main physicochemical and microbiological parameters of collected petroleum-contaminated soils with different degrees of contamination from DaGang oil field (southeast of Tianjin, northeast China) were comparatively analyzed in order to assess the influence of petroleum contaminants on the physicochemical and microbiological properties of soil. An integration of microcalorimetric technique with urease enzyme analysis was used with the aim to assess a general status of soil metabolism and the potential availability of nitrogen nutrient in soils stressed by petroleum-derived contaminants. The total petroleum hydrocarbon (TPH) content of contaminated soils varied from 752.3 to 29,114 mg kg^?1. Although the studied physicochemical and biological parameters showed variations dependent on TPH content, the correlation matrix showed also highly significant correlation coefficients among parameters, suggesting their utility in describing a complex matrix such as soil even in the presence of a high level of contaminants. The microcalorimetric measures gave evidence of microbial adaptation under highest TPH concentration; this would help in assessing the potential of a polluted soil to promote self-degradation of oil-derived hydrocarbon under natural or assisted remediation. The results highlighted the importance of the application of combined approach in the study of those parameters driving the soil amelioration and bioremediation.     

Column study of Cr(VI) removal by cationic hydrogel for in-situ remediation of contaminated groundwater and soil

Column experiments were conducted for examining the effectiveness of the cationic hydrogel on Cr(VI) removal from groundwater and soil. For in-situ groundwater remediation, the effects of background anions, humic acid (HA) and pH were studied. Cr(VI) has a higher preference for being adsorbed onto the cationic hydrogel than sulphate, bicarbonate ions and HA. However, the adsorbed HA reduced the Cr(VI) removal capacity of the cationic hydrogel, especially after regeneration of the adsorbents, probably due to the blockage of adsorption sites. The Cr(VI) removal was slightly influenced by the groundwater pH that could be attributed to Cr(VI) speciation. The 6-cycle regeneration and reusability study shows that the effectiveness of the cationic hydrogel remained almost unchanged. On average, 93% of the adsorbed Cr(VI) was recovered in each cycle and concentrated Cr(VI) solution was obtained after regeneration. For in-situ soil remediation, the flushing water pH had an insignificant effect on the release of Cr(VI) from the soils. Multiple-pulse flushing increased the removal of Cr(VI) from the soils. In contrast, more flushing water and longer operation may be required to achieve the same removal level by continuous flushing.     

Scavenging of BHCs and DDTs from soil by thermal desorption and solvent washing

Intensive remediation of abandoned former organochlorine pesticides (OCPs) manufacturing areas is necessary because the central and surrounding soils contaminated by OCPs are harmful to crop production and food safety. Organochlorine and its residues are persistent in environments and difficult to remove from contaminated soils due to their low solubility and higher sorption to the soils. We performed a comprehensive study on the remediation of OCPs-contaminated soils using thermal desorption technique and solvent washing approaches. The tested soil was thermally treated at 225, 325, 400, and 500 °C for 10, 20, 30, 45, 60, and 90 min, respectively. In addition, we tested soil washing with several organic solvents including n-alcohols and surfactants. The optimal ratio of soil/solvent was tested, and the recycling of used ethanol was investigated. Finally, activities of polyphenol oxidase (PPO), urease (URE), alkaline phosphatase, acid phosphatase (ACP), and invertase (INV) were assayed in the treated soils. The tested soil was thermally treated at 500 °C for 30 min, and the concentration of contaminants in soil was decreased from 3,115.77 to 0.33 mg kg^?1. The thermal desorption in soil was governed by the first-order kinetics model. For the chemical washing experiment, ethanol showed a higher efficiency than any other solvent. Using a 1:20 ratio of soil/solvent, the maximum removal of OCPs was achieved within 15 min. Under this condition, approximately 87 % of OCPs was removed from the soils. More than 90 % of ethanol in the spent wash fluid could be recovered. Activities of some enzymes in soils were increased after ethanol treatment. But ALP, ACP, and INV activities were decreased and PPO and URE showed slightly higher activities following remediation by thermal treatment. Both heating temperature and time were the key factors for thermal desorption of OCPs. The n-alcohol solvent showed higher removal of OCPs from soils than surfactants. The highly efficient removal of OCPs from soil was achieved using ethanol. More than 90 % of ethanol could be recovered and be reused following distillation. This study provides a cost-effective and highly efficient way to remediate the OCPs-contaminated soils.     

Influence of ciprofloxacin on the microbial catabolic diversity in soil

In this study, the effect of ciprofloxacin (CIP) on the catabolic diversity of soil microbial communities was evaluated. Soil samples were spiked with ciprofloxacin (0, 1, 5 and 50 mg?kg^?1) and were incubated for 1, 3, 9, 22 and 40 days. Untreated controls received only water. The functional diversity of the microbial community studied was characterized using a catabolic response profile (CRP). Six substrate groups were tested: carbohydrates, amino acids, carboxylic acids, aromatic chemicals, alcohols and polymers. After 40 days, the CIP concentrations in the soil samples ranged from 25% to 58% of the initial concentrations. Soil respiratory responses to the individual substrates D-glucose, lactose, D-mannose, L-glutamic, Na-citrate, malic acid and inosine were inhibited at the high CIP concentrations (5 and 50 mg·kg^?1) in the soils and were increased at the lowest CIP concentration (1 mg·kg^?1). Soil respiration was inhibited at all of the CIP concentrations after the addition of D-galactose and glycerol. The CIP concentration and incubation time explained 45.3% of the variance of the catabolic responses. The CRP analysis clearly discriminated among the different CIP concentrations. The results suggest that CIP strongly affects the catabolic diversities of soil microbial communities and that its effect is more significant than that of incubation time.     

Responses of earthworm to aluminum toxicity in latosol

Excess aluminum (Al) in soils due to acid rain leaching is toxic to water resources and harmful to soil organisms and plants. This study investigated adverse impacts of Al levels upon earthworms (Eisenia fetida) from the latosol (acidic red soil). Laboratory experiments were performed to examine the survival and avoidance of earthworms from high Al concentrations and investigate the response of earthworms upon Al toxicity at seven different Al concentrations that ranged from 0 to 300 mg kg^?1 over a 28-day period. Our study showed that the rate of the earthworm survival was 100 % within the first 7 days and decreased as time elapsed, especially for the Al concentrations at 200 and 300 mg kg^?1. A very good linear correlation existed between the earthworm avoidance and the soil Al concentration. There was no Al toxicity to earthworms with the Al concentration ≤50 mg kg^?1, and the toxicity started with the Al concentration ≥100 mg kg^?1. Low Al concentration (i.e., <50 mg kg^?1) enhanced the growth of the earthworms, while high Al concentration (>100 mg kg^?1) retarded the growth of the earthworms. The weight of earthworms and the uptake of Al by earthworms increased with the Al concentrations from 0 to 50 mg kg^?1 and decreased with the Al concentrations from 50 to 300 mg kg^?1. The protein content in the earthworms decreased with the Al concentrations from 0 to 100 mg kg^?1 and increased from 100 to 300 mg kg^?1. In contrast, the catalase (CAT) and superoxide dismutase (SOD) activities in the earthworms increased with the Al concentrations from 0 to 100 mg kg^?1 and decreased from 100 to 300 mg kg^?1. The highest CAT and SOD activities and lowest protein content were found at the Al concentration of 100 mg kg^?1. Results suggest that a high level of Al content in latosol was harmful to earthworms.     

修复铬污染地下水的可渗透反应墙介质筛选

通过实验研究筛选出一种经济、高效的用于修复铬污染地下水的可渗透反应墙(PRB)介质。实验以铬污染地下水为研究对象,分别对Fe0、Fe0+石英砂和包覆型零价铁填料进行了筛选实验,选取处理效果好且经济可行的包覆型零价铁材料作为PRB反应介质。结果表明,以包覆型零价铁材料作为PRB反应介质,大大提高了铁粉的利用效率,且缓解了系统堵塞严重的问题。以包覆型零价铁材料作为PRB反应介质修复Cr(VI)污染地下水是可行的。     

Evaluation of Acinetobacter sp. B9 for Cr (VI) resistance and detoxification with potential application in bioremediation of heavy-metals-rich industrial wastewater

Present work demonstrates Cr (VI) detoxification and resistance mechanism of a newly isolated strain (B9) of Acinetobacter sp. Bioremediation potential of the strain B9 is shown by simultaneous removal of major heavy metals including chromium from heavy-metals-rich metal finishing industrial wastewater. Strain B9 tolerate up to 350 mg L^?1 of Cr (VI) and also shows level of tolerance to Ni (II), Zn (II), Pb (II), and Cd (II). The strain was capable of reducing 67 % of initial 7.0 mg L^?1 of Cr (VI) within 24 h of incubation, while in presence of Cu ions 100 % removal of initial 7.0 and 10 mg L^?1 of Cr (VI) was observed with in 24 h. pH in the range of 6.0–8.0 and inoculum size of 2 % (v/v) were determined to be optimum for dichromate reduction. Fourier transform infrared spectroscopy and transmission electron microscopy studies suggested absorption or intracellular accumulation and that might be one of the major mechanisms behind the chromium resistance by strain B9. Scanning electron microscopy showed morphological changes in the strain due to chromium stress. Relevance of the strain for treatment of heavy-metals-rich industrial wastewater resulted in 93.7, 55.4, and 68.94 % removal of initial 30 mg L^?1 Cr (VI), 246 mg L^?1 total Cr, and 51 mg L^?1 Ni, respectively, after 144 h of treatment in a batch mode.     

Assessment of natural sepiolite on cadmium stabilization, microbial communities, and enzyme activities in acidic soil

A pot trial was conducted to assess the efficiency of sepiolite-induced cadmium (Cd) immobilization in ultisoils. Under Cd concentrations of 1.25, 2.5, and 5 mg?kg^?1, the available Cd in the soil after the application of 1–10 % sepiolite decreased by a maximum of 44.4, 23.0, and 17.0 %, respectively, compared with no sepiolite treatments. The increase in the values of soil enzyme activities and microbial number proved that a certain metabolic recovery occurred after sepiolite treatment. The dry biomass of spinach (Spinacia oleracea) increased with increasing sepiolite concentration in the soil. However, the concentration (dry weight) of Cd in the spinach shoots decreased with the increase in sepiolite dose, with maximum reduction of 92.2, 90.0, and 84.9 %, respectively, compared with that of unamended soils. Under a Cd level of 1.25 mg?kg^?1, the Cd concentration in the edible parts of spinach at 1 % sepiolite amendment was lower than 0.2 mg?kg^?1 fresh weight, the maximum permissible concentration (MPC) of Cd in vegetable. Even at higher Cd concentrations (2.5 and 5 mg?kg^?1), safe spinach was produced when the sepiolite treatment was up to 5 %. The results showed that sepiolite-assisted remediation could potentially succeed on a field scale by decreasing Cd entry into the food chain.     

Heavy metal accumulation by poplar in calcareous soil with various degrees of multi-metal contamination: implications for phytoextraction and phytostabilization

The object of this study was to assess the capacity of Populus alba L. var. pyramidalis Bunge for phytoremediation of heavy metals on calcareous soils contaminated with multiple metals. In a pot culture experiment, a multi-metal-contaminated calcareous soil was mixed at different ratios with an uncontaminated, but otherwise similar soil, to establish a gradient of soil metal contamination levels. In a field experiment, poplars with different stand ages (3, 5, and 7 years) were sampled randomly in a wastewater-irrigated field. The concentrations of cadmium (Cd), Cu, lead (Pb), and zinc (Zn) in the poplar tissues and soil were determined. The accumulation of Cd and Zn was greatest in the leaves of P. pyramidalis, while Cu and Pb mainly accumulated in the roots. In the pot experiment, the highest tissue concentrations of Cd (40.76 mg kg^?1), Cu (8.21 mg kg^?1), Pb (41.62 mg kg^?1), and Zn (696 mg kg^?1) were all noted in the multi-metal-contaminated soil. Although extremely high levels of Cd and Zn accumulated in the leaves, phytoextraction using P. pyramidalis may take at least 24 and 16 years for Cd and Zn, respectively. The foliar concentrations of Cu and Pb were always within the normal ranges and were never higher than 8 and 5 mg kg^?1, respectively. The field experiment also revealed that the concentrations of all four metals in the bark were significantly higher than that in the wood. In addition, the tissue metal concentrations, together with the NH₄NO₃-extractable concentrations of metals in the root zone, decreased as the stand age increased. P. pyramidalis is suitable for phytostabilization of calcareous soils contaminated with multiple metals, but collection of the litter fall would be necessary due to the relatively high foliar concentrations of Cd and Zn.     

Dissipation of available benzo[a]pyrene in aging soil co-contaminated with cadmium and pyrene

A microcosm experiment was conducted to investigate the dissipation of available benzo[a]pyrene (BaP) in soils co-contaminated with cadmium (Cd) and pyrene (PYR) during aging process. The available residue of BaP in soil was separated into desorbing and non-desorbing fractions. The desorbing fraction contributed more to the dissipation of available BaP than the non-desorbing fraction did. The concentration of bound-residue fraction of BaP was quite low across all treatments. Within the duration of this study (250 days), transformation of BaP from available fractions to bound-residue fraction was not observed. Microbial degradation was the dominant mechanism of the dissipation of available BaP in the soil. The dissipation of available BaP was significantly inhibited with the increment in Cd level in the soil. The addition of PYR (250 mg kg^?1) remarkably promoted the dissipation of available BaP without reducing Cd availability in the soil. The calculated half-life of available BaP in the soil prolonged with the increment in Cd level; however, the addition of PYR shortened the half-life of available BaP by 13.1, 12.7, and 32.8 % in 0.44, 2.56, and 22 mg Cd kg^?1 soils, respectively. These results demonstrated that the inhibiting effect of Cd and the promoting effect of PYR on the dissipation of available BaP were competitive. Therefore, this study shows that the bioremediation process of BaP can be more complicated in co-contaminated soils.     

Insights into the mercury(II) adsorption and binding mechanism onto several typical soils in China

To better understand the Hg(II) adsorption by some typical soils and explore the insights about the binding between Hg(II) and soils, a batch of adsorption and characteristic experiments was conducted. Results showed that Hg(II) adsorption was well fitted by the Langmuir and Freundlich. The maximum adsorption amount of cinnamon soil (2094.73 mg kg^?1) was nearly tenfold as much as that of saline soil (229.49 mg kg^?1). The specific adsorption of Hg(II) on four soil surface was confirmed by X-ray photoelectron spectroscopy (XPS) owing to the change of elemental bonding energy after adsorption. However, the specific adsorption is mainly derived from some substances in the soil. Fourier transform infrared spectroscopy (FTIR) demonstrated that multiple oxygen-containing functional groups (O–H, C=O, and C–O) were involved in the Hg(II) adsorption, and the content of oxygen functional groups determined the adsorption capacity of the soil. Meanwhile, scanning electron microscopy combined with X-ray energy dispersive spectrometer (SEM–EDS) more intuitive revealed the binding of mercury to organic matter, metal oxides, and clay minerals in the soil and fundamentally confirmed the results of XPS and FTIR to further elucidate adsorptive phenomena. The complexation with oxygen-containing functional groups and the precipitation with minerals were likely the primary mechanisms for Hg(II) adsorption on several typical soils. This study is critical in understanding the transportation of Hg(II) in different soils and discovering potential preventative measures.     

Spatial distribution of mercury in topsoil from five regions of China

The concentrations and distributions of mercury (Hg) in topsoil from four provinces and one municipality in China were investigated. A total of 1,254 samples were collected and analyzed. The average concentrations of Hg were 0.064 mg kg^?1 for Liaoning Province, 0.100 mg kg^?1 for Jiangsu Province, 0.110 mg kg^?1 for Zhejiang Province, 0.154 mg kg^?1 for Sichuan Province, and 0.098 mg kg^?1 for Chongqing Municipality. Although differences were found among the ranges of Hg concentrations, the average values for each region were similar with other published data. The concentrations of Hg in topsoil varied largely upon the sampling locations. More than 80 % of the soil samples from Liaoning Province, Jiangsu Province, Zhejiang Province, and Chongqing Municipality, were ranked Grade I by the China Environmental Quality Standard for Soils, which can be considered as not contaminated by Hg. The concentrations of Hg in 0.3–0.4 % of soils collected from Jiangsu Province, Zhejiang Province and Chongqing Municipality exceeded the limitation for Grade III, indicating the contamination of Hg in these sites. The sources and potential risks of Hg in these sites should be brought to attention and further investigated.     

The impact of zero-valent iron nanoparticles upon soil microbial communities is context dependent

Nanosized zero-valent iron (nZVI) is an effective land remediation tool, but there remains little information regarding its impact upon and interactions with the soil microbial community. nZVI stabilised with sodium carboxymethyl cellulose was applied to soils of three contrasting textures and organic matter contents to determine impacts on soil microbial biomass, phenotypic (phospholipid fatty acid (PLFA)), and functional (multiple substrate-induced respiration (MSIR)) profiles. The nZVI significantly reduced microbial biomass by 29 % but only where soil was amended with 5 % straw. Effects of nZVI on MSIR profiles were only evident in the clay soils and were independent of organic matter content. PLFA profiling indicated that the soil microbial community structure in sandy soils were apparently the most, and clay soils the least, vulnerable to nZVI suggesting a protective effect imparted by clays. Evidence of nZVI bactericidal effects on Gram-negative bacteria and a potential reduction of arbuscular mycorrhizal fungi are presented. Data imply that the impact of nZVI on soil microbial communities is dependent on organic matter content and soil mineral type. Thereby, evaluations of nZVI toxicity on soil microbial communities should consider context. The reduction of AM fungi following nZVI application may have implications for land remediation.     

The combined effects of urea application and simulated acid rain on soil acidification and microbial community structure

Our aim was to test the effects of simulated acid rain (SAR) at different pHs, when applied to fertilized and unfertilized soils, on the leaching of soil cations (K, Ca, Mg, Na) and Al. Their effects on soil pH, exchangeable H⁺ and Al³⁺ and microbial community structure were also determined. A Paleudalfs soil was incubated for 30 days, with and without an initial application of urea (200 mg N kg^?1soil) as nitrogen (N) fertilizer. The soil was held in columns and leached with SAR at three pH levels. Six treatments were tested: SAR of pH 2.5, 4.0 and 5.6 leaching on unfertilized soil (T1, T2 and T3), and on soils fertilized with urea (T4, T5 and T6). Increasing acid inputs proportionally increased cation leaching in both unfertilized and fertilized soils. Urea application increased the initial Ca and Mg leaching, but had no effect on the total concentrations of Ca, Mg and K leached. There was no significant difference for the amount of Na leached between the different treatments. The SAR pH and urea application had significant effects on soil pH, exchangeable H⁺ and Al³⁺. Urea application, SAR treated with various pH, and the interactions between them all had significant impacts on total phospholipid fatty acids (PLFAs). The highest concentration of total PLFAs occurred in fertilized soils with SAR pH5.6 and the lowest in soils leached with the lowest SAR pH. Soils pretreated with urea then leached with SARs of pH 4.0 and 5.6 had larger total PLFA concentrations than soil without urea. Bacterial, fungal, actinomycete, Gram-negative and Gram-positive bacterial PLFAs had generally similar trends to total PLFAs.     

Accumulation of Cr,Cd, Pb,Cu, and Zn by plants in tanning sludge storage sites: opportunities for contamination bioindication and phytoremediation

Tanning sludge enriched with high concentrations of Cr and other metals has adverse effects on the environment. Plants growing in the metalliferous soils may have the ability to cope with high metal concentrations. This study focuses on potentials of using native plants for bioindication and/or phytoremediation of Cr-contaminated sites. In the study, we characterized plants and soils from six tanning sludge storage sites. Soil in these sites exhibited toxic levels of Cr (averaged 16,492 mg kg^?1) and other metals (e.g., 48.3 mg Cu kg^?1, 2370 mg Zn kg^?1, 44.9 mg Pb kg^?1, and 0.59 mg Cd kg^?1). Different metal tolerance and accumulation patterns were observed among the sampled plant species. Phragmites australis, Zephyranthes candida, Cynodon dactylon, and Alternanthera philoxeroides accumulated moderate-high concentrations of Cr and other metals, which could make them good bioindicators of heavy metal pollution. High Cr and other metal concentrations (e.g., Cd and Pb) were found in Chenopodium rubrum (372 mg Cr kg^?1), Aster subulatus (310 mg Cr kg^?1), and Brassica chinensis (300 mg Cr kg^?1), being considered as metal accumulators. In addition, Nerium indicum and Z. candida were able to tolerate high concentrations of Cr and other metals, and they may be used as preferable pioneer species to grow or use for restoration in Cr-contaminated sites. This study can be useful for establishing guidelines to select the most suitable plant species to revegetate and remediate metals in tanning sludge-contaminated fields.     

Detection and quantification of chlordecone in contaminated soils from the French West Indies by GC-MS using the 13C10-chlordecone stable isotope as a tracer

Chlordecone is an organochlorine insecticide that has been widely used to control banana weevil in the French West Indies. As a result of this intense use, up to 20,000 ha are contaminated by this insecticide in the French West Indies, and this causes environmental damage and health problems. A scenario of exposure was drawn by French authorities, based on land usage records. Many efforts have been made to monitor the occurrence of chlordecone and its main metabolites using different analytical methods, including GC, GC/MS, LC/MS, and NIRS. Although these different methods allow for the detection and quantification of chlordecone from soils, none of them estimate the bottleneck caused by extraction of this organochlorine from soils with high adsorption ability. In this study, we used ¹³C₁₀-chlordecone as a tracer to estimate chlordecone extraction yield and to quantify chlordecone in soil extracts based on the ¹³C/¹²C isotope dilution. We report the optimization of ¹³C₁₀-chlordecone extraction from an Andosol. The method was found to be linear from 0.118 to 43 mg kg^?1 in the Andosol, with an instrumental detection limit estimated at 8.84 μg kg^?1. This method showed that chlordecone ranged from 35.4 down to 0.18 mg kg^?1 in Andosol, Nitisol, Ferralsol, and Fluvisol soil types. Traces of the metabolite β-monohydrochlordecone were detected in the Andosol, Nitisol, and Ferralsol soil samples. This last result indicates that this method could be useful to monitor the fate of chlordecone in soils of the French West Indies.     

Phytoscreening and phytoextraction of heavy metals at Danish polluted sites using willow and poplar trees

The main purpose of this study was to determine typical concentrations of heavy metals (HM) in wood from willows and poplars, in order to test the feasibility of phytoscreening and phytoextraction of HM. Samples were taken from one strongly, one moderately, and one slightly polluted site and from three reference sites. Wood from both tree species had similar background concentrations at 0.5 mg kg^?1 for cadmium (Cd), 1.6 mg kg^?1 for copper (Cu), 0.3 mg kg^?1 for nickel (Ni), and 25 mg kg^?1 for zinc (Zn). Concentrations of chromium (Cr) and lead (Pb) were below or close to detection limit. Concentrations in wood from the highly polluted site were significantly elevated, compared to references, in particular for willow. The conclusion from these results is that tree coring could be used successfully to identify strongly heavy metal-polluted soil for Cd, Cu, Ni, Zn, and that willow trees were superior to poplars, except when screening for Ni. Phytoextraction of HMs was quantified from measured concentration in wood at the most polluted site. Extraction efficiencies were best for willows and Cd, but below 0.5 % over 10 years, and below 1?‰ in 10 years for all other HMs.