The accumulation of trace metals in soil is a serious environmental problem that creates a hazard when metals are transferred to water or plants. To understand the mobility and bioavailability of trace metals, the concentrations and distributions of trace metals must be established for different physical and chemical phases of the soil. We determined the concentrations of trace metals (Zn, Pb, Cu, Cr, Co, Ni, Mn, and Fe) in soil using the sequential extraction method recommended by Community Bureau of Reference (BCR) and analysed chemical properties, such as the pH, cation exchange capacity, total organic carbon, electrical conductivity, and calcium carbonate. Our results revealed higher concentrations of trace metals in topsoil samples (0–20 cm) than in subsoil samples (20–40 cm and 40–60 cm) for most metals at four sites. Zn in the topsoil was mostly associated with the non-resistant fraction at all sites. Approximately 60% more Pb was bound to the non-residual, exchangeable and reducible fractions at all sites, and soil depths. Cr, Cu, Ni and Fe were mainly in the residual fraction, whereas Mn was largely present in the non-resistant fraction. The global contamination factor of trace metals decreased with soil depth. The mobility and bioavailability were greatest for Zn, followed by Cu and Pb.
A specific flora has developped in Central Africa on soils which are naturally rich in Cu and Co. Mining and ore treatment activities in the Katanga province (RDC) have generated contaminations which endanger ecosystem viability and/or human health. A survey of edaphic conditions prevailing for plant growing on natural metalliferous outcrops, the « copper hills », in mining sites (quarries), and in contaminated areas around metal smelters, is conducted as a first stage of a phytoremediation-based research programme. Soluble, available and total content in some metallic trace elements have been measured. The first results show a relatively high heterogeneity inside and between sites. But the main finding is related to the very different nature of contamination between the three types of sites. This point constitutes an additionnal difficulty that should be taken into account for the selection of metallophytic species from the copper hills or the quarries in order to vegetalize a site contaminated by atmospheric fall outs from metal smelters in Lubumbashi.
The quantities transported of metal ions at pH 4, in ascending order, were: • M1: Cr <Pb < Al <As <Ni = Zn = Cd
• M2: Cr <Al = Pb = As <Ni = Zn = Cd
Transport of heavy metals from the roots to the aerial parts of plants is a key factor in phytoextraction processes because the pollutant may be removed from the site once the plants are harvested. In this context, the transport of heavy metals through materials with a similar diameter to those found in the plants xylem may be of practical use in the development of new techniques to remove these pollutants based on the capillary properties showed by certain materials, replicating the soil-plant-atmosphere continuity (Sperry et al., 2003). Under these premises, research must be carried out to learn more about the performance of the materials, particularly, in relation to the change of certain environmental variables (concentrations, temperature, pressure, type of contaminants, etc.) and, in turn, applications in situ should also be undertaken. Given the wide range of micro and nanomaterials (properties, life spans, costs, etc.) and the changing conditions of the contaminatedsites, the emulation of transport of pollutants based on the vascular system of plants may have an interesting potential of development in soil remediation.
2. Materials and methods
2.1. Study area and characterization of experimental soils
The study area consists of a 3 km radius circle surrounding the Sclaigneaux calaminary site. The term “calaminary” originates from “Calamine” which is a general description of zinc-ores such as zinc –silicate, zinc –carbonate or the assemblage of hemimorphite, smithsonite, hydrozincite and willemite (Dejonghe, 1998). This area is known for its historical soil contamination by a former Zn – Pb ore treatment plant ( Liénard et al., 2014 ). The Cu, Cd, Pb and Zn metals originate from historic atmospheric fallout of dusts enriched in these four metals. The soils used in the experiment represent one of the three major soils type present on the study area ( Liénard et al., 2011 ), and are characterized as loamy-stony soils with gravel (Cambisols (Siltic) ( WRB, 2014 )) developed on ancient alluvial gravely terraces of Meuse river. Three samples were collected from contaminated ﬁelds and a control sample was collected from an uncontaminated ﬁeld. Sampling points were located according to distance from the metal source. Four plots of about 20 –25 m 2 in size were selected for the study. The study sites
Collapse in contact with NAPL and increase sweep efficien-
cy of contaminated areas
This project will lead to the application of foam technology on LNAPL contaminatedsites. This study presents the first steps towards this objective. Different surfactants have been select- ed and sand column tests were made.
Figure 7.4 Total PAH concentrations in a) roots and b) shoots. .................................................................. 83 Figure 7.5 Total PAH concentration in roots () and in shoots () as a function of total soil concentration.
............................................................................................................................................................. 83 Figure 7.6 Comparison between experimental and predicted individual PAH root concentrations obtained with Briggs and Nguyen models and using pore water concentrations obtained from a) and b) POM measurements, c) and d) Tenax extracted fraction, e) and f) total soil concentrations........ 85 Figure 7.7 Comparison between experimental and predicted individual PAH shoot concentrations obtained with Briggs model and using pore water concentrations obtained from a) POM measurements, b) Tenax extracted fraction, c) total soil concentrations. ......................................... 86 Figure 9.1 A flow chart for conducting a tiered risk assessment applying the isotope dilution method and the PNEC-calculator in tier 3. ............................................................................................................ 101 Figure 9.2. Screenshot of the software to calculate a soil type specific PNEC value. Available from: http://www.arche-consulting.be/metal-csa-toolbox/soil-pnec-calculator/ ..................................... 102 Figure 9.3 Schematic for conducting a risk assessment that accounts for difference in partitioning behavior of pyrogenically impacted sitesand reference soils. ......................................................... 104 Figure 9.4 Schematic for conducting a risk assessment that is based on bioavailable porewater concentrations
A significant number of petroleum-contaminatedsites have been identified in polar regions as a result of fuel storage, transportation, military, and industrial activities (1). Cold temperatures and the remote locations of these sites pose challenges to site remediation. On-site ex situ bioremediation has been demonstrated in field studies at sub-Arctic sites (2). It is generally believed that the potential for bioreme- diation exists only during the 2 to 3 month summer season when daily mean air temperatures at northern sites are generally in the range of 5-15 °C. The short summer season over which bioremediation is implemented and monitored is often insufficient time for meeting remediation targets, especially where contamination is extensive. Treatment systems are usually left dormant after summer when freezing temperatures set in and revived in the following summer (3), and there is little knowledge on the extent of petroleum hydrocarbon degradation occurring in this time interval and on how petroleum hydrocarbon-degrading bacteria respond to these temperature regimes.
126.96.36.199. Phytostabilization. Phytostabilization is the use of plants to de- crease the bioavailability and mobility of heavy metal(loid)s in soils due to their stabilization with the help of plants ( Sylvain et al., 2016 ). Phytostabilization of metals does not reduce the concentration of heavy metal(loid)s present in contaminated soil but prohibits their off-site movement. Phytostabilization aims to restrict heavy metal(- loid)s in the vadose zone of plants through accumulation by roots or precipitation within the rhizosphere ( Bolan et al., 2011 ). Therefore, un- like other methods of phytoremediation, phytostabilization does not re- mediate the contaminatedsoils but reduces the contamination of nearby media/area. Phytostabilization is generally used for soils where phytoextraction is not desirable or possible. Furthermore, phytostabilization can also be used at sites where technical or regulato- ry limitations interrupt with the selection and implementation of the most appropriate remediation techniques. For example, in order to limit off-site heavy metal(loid)s movement from barren contaminated site, phytostabilization can be a useful option. Plants can prohibit movement of metals through several methods: reduced leaching through upward water ﬂow generated by plant transpiration, reduced soil erosion due to stabilization of soil by plant roots and decrease in runoff due to above-ground vegetation. Phytostabilization does not pro- duce contaminated secondary waste that needs further management. Phytostabilization is helpful in achieving ecosystem restoration because it increases soil fertility. However, since the heavy metal(loid)s are sta- bilized within soil, the site needs regular monitoring to make sure that the optimal stabilizing conditions are retained ( Bolan et al., 2011 ). Phytostabilization may raise some issues under highly contaminatedsoils. In such cases, cultivation of plant species tolerant to metal contamination and adapted to the local environmental conditions is advantageous.
In the last decades, soilsand groundwater at industrial sites have been at risk from contaminant discharges, inducing a major risk to the environment and to humans. At many industrial sites, a vadose or unsaturated soil zone separates the source area at the soil surface from the target groundwater body in the subsoil. This vadose zone largely controls contaminant release to the groundwater body. Therefore, it is important to understand the processes that govern the transport and fate of contaminants in this area, especially for designing protection and remediation measures (Govindaraju, 2002). In order to understand the distribution and the transport of pollutants to groundwater, contaminant fluxes through the vadose zone must be quantified (Bloem et al., 2010; Mertens et al., 2008; Govindaraju, 2002). However, as stated by Mertens et al. (2005) and
chelating agent before harvest were evaluated. In the akaline soil tested, the use of the free-acid form of EDTA and exposure time of one to 2 weeks before harvesting, increased the concen- tration of metals translocated to plant tissues. Total heavy metal accumulation (Cu, Pb, and Zn) was in the range of 0.1–0.25% of aerial and root tissues for both willow and fescue. Indian mustard accumulated these metals to an extent of 0.5% and 1.2% of aerial and root biomass, respectively, after a 2 week exposure time to EDTA. The phytoextraction results were lower (i.e., 0.12%) than those obtained by Blaylock et al. (1997) in a pot trial (soil pH 7.3, and using 5 mmol/kg EDTA), where Indian mustard (cv. 426308) accumulated 1% Pb in aerial tissues. Direct comparison of these two studies is diﬃcult however, due to notable diﬀerences in the soils used. The soil used by Blaylock et al. (1997) was a clean silt loam soil amended with heavy metals, whereas the soil used in this study was collected from the site, without metal amendment or pH readjustment. To our knowledge, this is the ﬁrst phytoextraction study focussing on alkaline soils.
This work assesses the potential of stinging nettle (Urd.ca dioica L.) growing on trace element contaminatedsoils to produœ fibres for rnaterial applications. The nettles studied in this work grew spontaneously and dominated the vegetation cover in poplar short rotation coppices planted for the phytornanagement of lands contaminated by trace elements. Two sites were studied, contaminated by Hg for the first one and a mix of As, Cd, Pb and Zn for the second one. Results show that, for the considered soils, the contaminant contents in nettle bast fibres were at low levels, comparable to those collected at unpolluted control areas. lt rnakes it possible to consider this biornass for material use. The measured rnatter yield was lower than those obtained with traditional fibre crops cultivated in Europe on agricultural lands. However, the tensile properties of the bast fibres mechanically ex tracted without field retting or prior alkaline treatment were equal to or better than those of industrial hemp and flax, rnaking spontaneous nettles an interesting supplement to traditional European fibre crops for rnaterial applications.
VISUAL COLORIMETRIC SCREENING METHOD
Simple qualitative and semi-quantitative visual colorimetric tests to screen for explosive residues on-site can be performed using the Expray TM kit (available from Plexus Scientific, Silver Spring, MD). This method is particularly useful in the field when chunks of unknown material are suspected to be energetic material based. The Expray TM kit comes in a small lightweight (less than 1.4 kg) case that contains three aerosol cans for dispensing chemical reagents and some test paper. To screen surfaces, e.g., range scrap, the first step is to wipe (rub) exposed surfaces with a white sheet of paper (100 test sheets are supplied with the kit, or any white filter paper or cotton swab could be used). For direct analysis of soils (or other materials comprised of small particles), a small quantity (0.5 to 1 g) is placed in the middle of 47 mm fiberglass filter paper and soaked with acetone (approximately, twice the volume as weight). The filter paper is folded over and placed on a clean white paper surface. For soil or water sample extracts, a small aliquot (5 µL) of solvent extract (acetone or acetonitrile) is transferred to a test sheet. Actually, several (6 to 12) sample extracts can be screened simultaneously by carefully arranging the placement of each aliquot on the test sheet.
Final Report., Alberta Environment, Lethbridge, Canada, 112 pp., 1986.
Or, D., Tuller, M., and Stothoff, S.: Review of Vadose Zone Measurement and Monitoring Tools for Yucca Mountain Performance Confirmation Program, U.S. Nuclear Regulatory Commission, Washington D.C., USA, 110pp., 2006.
Perri, M. T., Cassiani, G., Gervasio, I., Deiana, R., and Binley, A. M.: A saline tracer test monitored via both surface and cross-borehole electrical resistivity tomography: comparison of time-lapse results, J. Appl. Geophys., 79, 6–16, 30
These values indicated that the pH of the solution after attrition was similar for the different soils studied, which 7
seemed logical as the pH of the soil samples were similar and near 7.5. Around this pH, the solubility of both metals 8
Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, Quebec, Canada, 1 and
National Research Council Canada, Biotechnology Research Institute, Montreal, Quebec, Canada 2
Received 25 January 2011/Accepted 10 April 2011
Arctic soils are increasingly susceptible to petroleum hydrocarbon contamination, as exploration and exploitation of the Arctic increase. Bioremediation in these soils is challenging due to logistical constraints and because soil temperatures only rise above 0°C for ⬃2 months each year. Nitrogen is often added to contam- inated soil in situ to stimulate the existing microbial community, but little is known about how the added nutrients are used by these microorganisms. Microbes vary widely in their ability to metabolize petroleum hydrocarbons, so the question becomes: which hydrocarbon-degrading microorganisms most effectively use this added nitrogen for growth? Using [ 15 N]DNA-based stable isotope probing, we determined which taxo- nomic groups most readily incorporated nitrogen from the monoammonium phosphate added to contaminatedand uncontaminated soil in Canadian Forces Station-Alert, Nunavut, Canada. Fractions from each sample were amplified with bacterial 16S rRNA and alkane monooxygenase B (alkB) gene-specific primers and then sequenced using lage-scale parallel-pyrosequencing. Sequence data was combined with 16S rRNA and alkB gene C quantitative PCR data to measure the presence of various phylogenetic groups in fractions at different buoyant densities. Several families of Proteobacteria and Actinobacteria that are directly involved in petroleum degradation incorporated the added nitrogen in contaminatedsoils, but it was the DNA of Sphingomonadaceae that was most enriched in 15 N. Bacterial growth in uncontaminated soils was not stimulated by nutrient amendment. Our results suggest that nitrogen uptake efficiency differs between bacterial groups in contami- nated soils. A better understanding of how groups of hydrocarbon-degraders contribute to the catabolism of petroleum will facilitate the design of more targeted bioremediation treatments.
diesel oil (10 ml) + fertilizer (1 ml), Arabian light crude oil (10 ml), and crude oil (10 ml) + fertilizer (1 ml). Two different bioremediation agents were used: a slow release fertilizer Inipol EAP-22 (Elf Atochem) in 1997 and a fish compost in 1999. Plots were sampled on a regular basis during a three-year period. All samples were analysed for total, saprophytic psychrophilic, and hydrocarbon-utilising bacteria. A one order of magnitude increase of saprophytic and hydrocarbon-utilising micro-organisms occurred during the first month of the experiment in most of the contaminated enclosures, but no clear differences appeared between fertilized and unfertilized plots. Diesel-oil contamination induced a significant increase of all bacterial parameters in all contaminatedsoils. Crude-oil contamination had no clear effects on microbial assemblages. It was clear that the microbial response could be rapid and efficient in spite of the severe weather conditions. However, microbial growth was not clearly improved in the presence of bioremediation agents.
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Determination of oil content of contaminatedsoilsand sludges
Majid, Abdul; Sparks, Bryan D.
pavement crusts, that had few empty channels, there is no clear relationship between
the abundance of empty channels and crust types (Tab. 3). Globally, empty channels were less abundant in Pinnacle Transect compared to Simpson's Dam. This suggests that bioturbation might be less intense. However, one must keep in mind that the abundance of empty channels is not only related to biological activity but also to channel resilience and past grazing pressure (i.e. hoof compaction, particularly in wet soil; Greene et al., 1994). The latter is related to (i) physical properties of the soil material such as cohesion and (ii) further biological activity that might destroy previous channels. Therefore, the interpretation of the abundance of empty channels in terms of biological activity is not straightforward. In this respect, the abundance of filled in channels might be a better indicator. However, no clear relationships appear between filled in channels and crust type (Tab. 3). In Pinnacle Transect, most buried crusts showed evidences of bioturbation, e.g. perforated plasmic layers (Appendix E, Fig. E14 and E15).