Water-soluble Contaminants Research Articles

The Effect of Plant Growth Regulator for Phytoremediation

Phytoremediation is the use of vegetation for in situ treatment of contaminated soils, sediments, and water. It is best applied at sites with shallow contamination of metal pollutants. The term “assisted phytoextraction” usually refers to the process of applying a chemical additive to contaminated soil in order to increase the metal uptake by crop plants. In the process of phytoremediation, applying plant growth regulator can promote phytoextraction effects. This paper reviewed the effect of the plant growth regulator for the biological growth, plant transpiration and heavy metal stress. the increase in metal accumulation in upper parts of plant could be related to both the role of PGRs in the enhancement of plant resistance to stress (as toxic metals) and the increase in transpiration rate, i.e. flux of water-soluble soil components and contaminants by the regulation of stomatal opening.

Haemocytic leukemia in Prince Edward Island (PEI) soft shell clam (Mya arenaria): Spatial distribution in agriculturally impacted estuaries

Intensive farming of potatoes in Prince Edward Island (PEI) relies on the repeated and widespread application of fertilizers and pesticides. In PEI the main potato farming areas are in close proximity and drain directly to estuaries. Runoff from high agricultural activity watersheds could impact benthic organism health in the depositional zone of downstream estuaries. The estuarine filter feeder Mya arenaria (soft-shell clam) could be particularly vulnerable to both particle-adsorbed and water soluble contaminants. M. arenaria is susceptible to haemocytic leukemia. In May 2009, we established that heavily proliferated leukemia (HPL) prevalence was generally higher in PEI estuaries located downstream of high intensity potato farming (Dunk and Wilmot estuaries) watersheds than in estuaries downstream of lower intensity areas. Using Mab-1E10 based immunocytochemistry we observed that leukemic haemocytes from the Dunk and Wilmot estuaries were 1E10 negative whereas those from the Ox/Sheep estuary (low potato farming intensity) were 1E10 positive. The expression of genes in the p53 tumour suppressor pathway enabled us to differentiate groups of leukemic and normal M. arenaria, validating our diagnoses. In October 2009, we confirmed that HPL prevalence was elevated in the Dunk and Wilmot estuaries compared to reference (Souris River). Moreover, leukemia prevalence declined with distance from the river mouths along transects through the Dunk and Wilmot estuaries. The pesticides ß-endosulfan and α-endosulfan were detected in surface sediments from the Dunk and Wilmot estuaries, but not in sediments from either the Souris River or several other lower intensity potato farming watersheds. Our study provides evidence of an association between intensity of potato farming and prevalence of clam leukemia at downstream estuaries in PEI.

Ecotoxicological impacts of effluents generated by oil sands bitumen extraction and oil sands lixiviation on Pseudokirchneriella subcapitata

The exploitation of Athabasca oil sands deposits in northern Alberta has known an intense development in recent years. This development has raised concern about the ecotoxicological risk of such industrial activities adjacent to the Athabasca River. Indeed, bitumen extraction generated large amounts of oil sands process-affected water (OSPW) which are discharged in tailing ponds in the Athabasca River watershed. This study sought to evaluate and compare the toxicity of OSPW and oil sands lixiviate water (OSLW) with a baseline (oil sands exposed to water; OSW) on a microalgae, Pseudokirchneriella subcapitata, at different concentrations (1.9, 5.5, 12.25, 25 and 37.5%, v/v). Chemical analyses of water-soluble contaminants showed that OSPW and OSLW were enriched in different elements such as vanadium (enrichment factor, EF=66 and 12, respectively), aluminum (EF=64 and 15, respectively), iron (EF=52.5 and 17.1, respectively) and chromium (39 and 10, respectively). The toxicity of OSPW on cells with optimal intracellular esterase activity and chlorophyll autofluorescence (viable cells) (72h-IC 50%<1.9%) was 20 times higher than the one of OSW (72h-IC 50%>37.5%, v/v). OSLW was 4.4 times less toxic (IC 50%=8.5%, v/v) than OSPW and 4.5 times more toxic than OSW. The inhibition of viable cell growth was significantly and highly correlated (<−0.7) with the increase of arsenic, beryllium, chromium, copper, lead, molybdenum and vanadium concentrations. The specific photosynthetic responses studied with JIP-test (rapid and polyphasic chlorophyll a fluorescence emission) showed a stimulation of the different functional parameters (efficiency of PSII to absorb energy from photons, size of effective PSII antenna and vitality of photosynthetic apparatus for energy conversion) in cultures exposed to OSPW and OSLW. To our knowledge, our study highlights the first evidence of physiological effects of OSPW and OSLW on microalgae.

Flesh residue concentrations of organochlorine pesticides in farmed and wild salmon from British Columbia, Canada

The present study reports measured levels of organochlorine pesticides (OCPs) in commercial salmon feed (n = 8) and farmed Atlantic, coho, and chinook salmon (n = 110), as well as wild coho, chinook, chum, sockeye, and pink salmon (n = 91). Flesh residue concentrations (ng/g wet weight) of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), chlordanes, chlorobenzenes (CBz) and cyclodiene pesticides (e.g., dieldrin, mirex) were 2 to 11 times higher (p < 0.05) in farmed salmon compared with wild salmon. Concentrations were positively correlated with flesh lipid levels. Farmed Atlantic salmon (12-15% lipid) typically exhibited the greatest OCP burdens compared with other salmon species. However, when expressed on a lipid weight basis, concentrations of OCPs (ng/g lipid weight) in wild salmon, in many cases, exceeded those levels in farmed salmon. Observed interspecies and site-specific variations of OCP concentrations in farmed and wild salmon may be attributed to divergent life history, prey/feed characteristics and composition, bioenergetics, or ambient environmental concentrations. Calculated biomagnification factors (BMF = C(F)/C(D), lipid wt) of OCPs in farmed salmon typically ranged between two and five. Biomagnification of chemicals such as DDTs, chlordanes, and mirex was anticipated, because those compounds tend to exhibit high dietary uptake and slow depuration rates in fish because of relatively high octanol-water partition coefficients (K(OW)s > 10⁵). Surprisingly, less hydrophobic pesticides such as hexachlorocyclohexanes and endosulfans (K(OW) s < 10⁵) consistently exhibited a high degree of biomagnification in farmed salmon species (BMFs > 5). This is contrary to previous laboratory and field observations demonstrating fish BMFs less than 1 for low K(OW) chemicals, because of efficient respiratory elimination of those compounds via gills. The results suggest that ambient seawater concentrations and bioconcentration-driven accumulation may play a key role in the bioaccumulation of these relatively more water-soluble contaminants in farmed salmon. Finally, OCP exposure through consumption of British Columbian salmon is found to be low relative to United States national average per capita total exposure levels and provisional tolerable daily intakes.

High temperature water-gas shift step in the production of clean hydrogen rich synthesis gas from gasified biomass

The possibility of using the water-gas shift (WGS) step for tuning the H2/CO-ratio in synthesis gas produced from gasified biomass has been investigated in the CHRISGAS (Clean Hydrogen Rich Synthesis Gas) project. The synthesis gas produced will contain contaminants such as H2S, NH3 and chloride components. As the most promising candidate FeCr catalyst, prepared in the laboratory, was tested. One part of the work was conducted in a laboratory set up with simulated gases and another part in real gases in the 100 kW Circulating Fluidized Bed (CFB) gasifier at Delft University of Technology. Used catalysts from both tests have been characterized by XRD and N2 adsoption/desorption at −196 °C. In the first part of the laboratory investigation a laboratory set up was built. The main gas mixture consisted of CO, CO2, H2, H2O and N2 with the possibility to add gas or water-soluble contaminants, like H2S, NH3 and HCl, in low concentration (0–3 dm3 m−3). The set up can be operated up to 2 MPa pressure at 200–600 °C and run un-attendant for 100 h or more. For the second part of the work a catalytic probe was developed that allowed exposure of the catalyst by inserting the probe into the flowing gas from gasified biomass. The catalyst deactivates by two different causes. The initial deactivation is caused by the growth of the crystals in the active phase (magnetite) and the higher crystallinity the lower specific surface area. The second deactivation is caused by the presence of catalytic poisons in the gas, such as H2S, NH3 and chloride that block the active surface. The catalyst subjected to sulphur poisoning shows decreased but stable activity. The activity shows strong decrease for the ammonia and HCl poisoned catalysts. It seems important to investigate the levels of these compounds before putting a FeCr based shift step in industrial operation. The activity also decreased after the catalysts had been exposed to gas from gasified biomass. The exposed catalysts are not re-activated by time on stream in the laboratory set up, which indicates that the decrease in CO2-ratio must be attributed to irreversible poisoning from compounds present in the gas from the gasifier. It is most likely that the FeCr catalyst is suitable to be used in a high temperature shift step, for industrial production of synthesis gas from gasified biomass if sulphur is the only poison needed to be taken into account. The ammonia should be decomposed in the previous catalytic reformer step but the levels of volatile chloride in the gas at the shift step position are not known.

Determination of acrylamide in potato crisps by capillary electrophoresis with quantum dot‐mediated LIF detection

Acrylamide or 2-propenamide (AAM), a water-soluble toxic contaminant, has recently caused health concern after it was found in food products made by high-temperature cooking. Due to its weak UV absorption and electrochemically inactive state, common analytical methods do not have sufficient sensitivity to meet the World Health Organization requirement. A LIF detection method mediated by water-soluble CdTe quantum dots capped with mercaptopropyl acid (MPA) is thus developed for AAM quantitation. The optimized conditions are as follows: 30 mmol/L SDS, 0.1 mmol/L quantum dot, and 40 mmol/L phosphate buffer solution at pH 8.0 under 18 kV run voltage with LIF detection at 473 nm excitation and 568 nm fluorescence. The linear quantitation range for AAM was found to vary from 1.0 to 100 mg/kg and a detection limit (S/N=2) at 0.1 mg/kg, showing sufficient sensitivity to meet the maximum AAM specified by the Joint Food and Agriculture Organization/World Health Organization Expert Committee for potato crisps. Recoveries for potato crisps sample spiked with 10, 20, and 100 mg/kg AAM were found to vary between 90 and 95% with RSD <5.7% (n=3).

Assessing the performance and longevity of Nb, Pt, Ta, Ti, Zr, and ZrO 2-sputtered Havar foils for the high-power production of reactive [ 18F]F − by proton irradiation of [ 18O]H 2O

As water-soluble ionic contaminants, which arise following proton irradiation of [ 18O]H 2O have been associated with decreased [ 18F]FDG yields, the minimization of these contaminants is an asset in improving the [ 18F]F − reactivity. To this end, we have previously demonstrated that the use of Nb-sputtered Havar foils results in decreased radionuclidic and chemical impurities in proton irradiated [ 18O]H 2O, improved [ 18F]FDG yields, and improved [ 18F]FDG yield consistency when compared with non-sputtered Havar. Resulting from the highly reactive chemical microenvironment within the target however, this niobium layer is observed to degrade over time. To find a material that displays increased longevity with regards to maintaining high [ 18F]F − reactivity, this project extensively investigated and compared Havar foils sputtered with Nb, Pt, Ta, Ti, Zr and ZrO 2. Of the materials investigated, the results of this study suggest that Ta-sputtered Havar foil is the preferred choice. For similar integrated currents (∼1,000,000 μA min), when comparing the Ta-sputtered Havar with Nb-sputtered Havar we observed: (i) greater than an order of magnitude decrease in radionuclidic impurities, (ii) a 6.4 percent increase ( p=0.0025) in the average TracerLab MX [ 18F]FDG yield, and (iii) an overall improvement in the FDG yield consistency. Excellent performance of the Ta-sputtered foil was maintained throughout its ∼1,500,000 μA min lifetime.

Occurrence of polar organic contaminants in the dissolved water phase of the Danube River and its major tributaries using SPE-LC-MS 2 analysis

Polar water-soluble organic contaminants were analysed in the dissolved liquid water phase of river water samples from the Danube River and its major tributaries (within the Joint Danube Survey 2). Analyses were performed by solid-phase extraction (SPE) followed by triple-quadrupole liquid chromatography mass spectrometry (LC-MS 2). In total, 34 different polar organic compounds were screened. Focus was given on pharmaceutical compounds (such as ibuprofen, diclofenac, sulfamethoxazole, carbamazepine), pesticides and their degradation products (e.g. bentazone, 2,4-D, mecoprop, atrazine, terbutylazine, desethylterbutylazine), perfluorinated acids (PFOS; PFOA), and endocrine disrupting compounds (nonylphenol, NPE 1C, bisphenol A, estrone). The most relevant polar compounds identified in the Danube River basin in terms of frequency of detection, persistency, and concentration levels were 1H-benzotriazole (median concentration 185 ng/L), caffeine (87 ng/L), tolyltriazole (73 ng/L), nonylphenoxy acetic acid (49 ng/L), carbamazepine (33 ng/L), 4-nitrophenol (29 ng/L), 2,4-dinitrophenol (19 ng/L), PFOA (17 ng/L), sulfamethoxazole (16 ng/L), desethylatrazine (11 ng/L), and 2,4-D (10 ng/L). The highest contamination levels were found in the area around Budapest and in the tributary rivers Arges (Romania), Timok (Bulgaria), Rusenski Lom (Bulgaria), and Velika Morava (Serbia).

Cross-Contamination Test of an Enthalpy Wheel Loading a Strong Acidic Cation Ion-Exchange Resin or 3A Zeolite as a Desiccant Material

Enthalpy wheels have been widely used for achieving comfortable air-conditioning with low energy consumption. Desiccant materials such as silica gel and molecular sieves are used so as to give it a latent heat exchanging function. However, this important function has become the cause of cross-contamination because substances with offensive odors are also adsorbed onto desiccants. In this study, cross-contamination of an enthalpy wheel consisting of ion-exchange resin particles as a desiccant material is examined and compared with a commercialized 3A zeolite wheel. It is found that the ion-exchange resin type wheel shows a smaller cross-contamination ratio than the other for all contaminants tested in this study, i.e. ammonia, carbon dioxide, formaldehyde and propane, although water-soluble and smaller contaminants such as ammonia still indicated a higher contamination ratio.

Evaluation of Detergency Using Artificially Soiled Multifiber Fabrics

The evaluation of textile detergency was carried out using artificially soiled multifiber adjacent fabric (MFF) composed of six different warp regions. The MFF soiled with model water-soluble, oily or particulate contaminant was cleaned in water, water/ethanol (1/1 in volume ratio), ethanol and n-decane with the stirring as a mechanical action. The detergency of the each fiber region was determined from the change in surface reflectance of the corresponding region due to cleaning. The soil removal was strongly dependent on contaminant, fiber and liquid species, indicating that the detergency was dominated by the dissolution of the contaminant into the washing liquid and the affinity between the contaminant and the fiber surface. The addition of alkali and surfactant to water or the solubilization of water into n-decane considerably increased the soil removal. The experimental results were not in contradiction with common and well-known knowledge about textile washing. Therefore, the artificially soiled MFF can be utilized for the detergency evaluation for textiles.

Investigation of Optimum Liquid for Textile Washing using Artificially Soiled Fabrics

In order to obtain a criterion of liquid cleaning power, a textile washing test was carried out in water and various organic solvents. Cotton and polyester clothes soiled with particulate, oily and water-soluble contaminants were used. The soiled clothes were cleaned in various liquids with stirring and the detergency was evaluated from the change in the surface reflectance of the soiled cloth due to cleaning. The detergency was largely dependent on contaminant, cloth and liquid species, and showed good agreement with common and well-known knowledge about textile washing; the particulate contaminant was difficult to remove in any liquid. In contrast, the oily and water-soluble contaminants were readily removable in the organic solvents and water, respectively. By adding alkali and surfactant to water, the removal of any contaminant considerably increased. In comparison with the stirring, the ultrasonic washing was carried out with the aqueous solutions, but unexpectedly the detergency of most soiled clothes did not increase. For any artificially soiled clothes, a certain relation was successively found between the detergency and the relative dielectric constant.

Identification of water soluble and particle bound compounds causing sublethal toxic effects. A field study on sediments affected by a chlor-alkali industry

A combination of cost effective sublethal Daphnia magna feeding tests, yeast- and cell culture-based bioassays and Toxicity Identification Evaluation (TIE) procedures was used to characterize toxic compounds within sediments collected in a river area under the influence of the effluents from a chlor-alkali industry (Ebro River, NE Spain). Tests were designed to measure and identify toxic compounds in the particulate and filtered water fractions of sediment elutriates. The combined use of bioassays responding to elutriates and dioxin-like compounds evidenced the existence of three major groups of hazardous contaminants in the most contaminated site: (A) metals such as cadmium and mercury bound to sediment fine particles that could be easily resuspended and moved downstream, (B) soluble compounds (presumably, lye) able to alkalinize water to toxic levels, and (C) organochlorine compounds with high dioxin-like activity. These results provided evidence that elutriate D. magna feeding responses can be used as surrogate assays for more tedious chronic whole sediment tests, and that the incorporation of such tests in sediment TIE procedures may improve the ability to identify the toxicity of particle-bound and water-soluble contaminants in sediments.

The effects of exogenous plant growth regulators in the phytoextraction of heavy metals

The term “assisted phytoextraction” usually refers to the process of applying a chemical additive to contaminated soil in order to increase the metal uptake by crop plants. In this study three commercially available plant growth regulators (PGRs) based on cytokinins (CKs) were used to boost the assisted phytoextraction of Pb and Zn in contaminated soil collected from a former manufactured gas-plant site. The effects of EDTA treatment in soil and PGR treatment in leaves of Helianthus annuus were investigated in terms of dry weight biomass, Pb and Zn accumulation in the upper parts of the plants, Pb and Zn phytoextraction efficiency and transpiration rate. Metal solubility in soil and its subsequent accumulation in shoots were markedly enhanced by EDTA. The combined effects of EDTA and cytokine resulted in an increase in the Pb and Zn phytoextraction efficiency (up to 890% and 330%, respectively, compared to untreated plants) and up to a 50% increase in foliar transpiration. Our results indicate that exogenous PGRs based on CKs can positively assist the phytoextraction increasing the biomass production, the metal accumulation in shoots and the plant transpiration. The observed increase in biomass could be related to its action in stimulation of cell division and shoot initiation. On the other hand, the increase in metal accumulation in upper parts of plant could be related to both the role of PGRs in the enhancement of plant resistance to stress (as toxic metals) and the increase in transpiration rate, i.e. flux of water-soluble soil components and contaminants by the regulation of stomatal opening.

Efficient removal and mechanisms of water soluble aromatic contaminants by a reduced-charge bentonite modified with benzyltrimethylammonium cation

A novel strategy utilizing the phenyls interaction and the hydrophobic affinity of available siloxane surface in the interlayer of bentonite was proposed to improve the sorption capabilities of organobentonites for water soluble aromatic contaminants. A unique organobentonite (65BTMA) was synthesized by intercalating benzyltrimethylammonium cation (BTMA +) into the interlayer of a reduced-charge bentonite with cation exchange capacity (CEC) of 65 cmol kg −1. Phenol, aniline and toluene were used as model compounds of water soluble aromatic contaminants. Their respective removal efficiencies by 65BTMA were achieved at 83.3%, 89.2% and 97.3% at the initial concentration of 20 mg l −1. To reveal the sorption mechanism, sorption characteristics of aromatic contaminants to 65BTMA were compared with that of aliphatic contaminants in similar molecular size. And various organobentonites were prepared by combining TMA + (tetramethylammonium), BTMA +, HTMA + (heptyltrimethylammonium) and CTMA + (cetyltrimethylammonium) with two bentonites (CEC = 108 and 65 cmol kg −1). To 65BTMA, sorption magnitudes of aromatic contaminants were much greater than that of aliphatic compounds with similar size; and dramatically higher than those to other organobentonites at low pollutant concentrations. These observations revealed that the strong phenyls interactions contributed significantly to sorb the aqueous soluble aromatic contaminants to 65BTMA (>90%), and which favored to design uniquely powerful sorbents.

Determination of solute leaching potential within a hummocky agricultural landscape

Leaching of water-soluble contaminants has resulted in degradation of groundwater quality. This research project examined the long-term spatial variability of leaching processes within two hummocky, agricultural landscapes near Bittern Lake, in central Alberta. Analysing the distribution of soil profiles within a landscape, we created a leaching potential index based on a soil profile index (SPI) and plan curvature measurements. The index accurately differentiated locations of very high and high leaching potential from low and very low leaching potential. This index may become a useful tool to determine the variability of leaching within an agricultural landscape, to identify areas of high leaching potential, to determine agricultural best management practices, and to minimize contamination of groundwater. Key words: Soil-landscape, soil horizon, soil classification, sulphate, electrical conductivity, leaching

Cleaning and Hydrophilization of Atomic Force Microscopy Silicon Probes

The silicon surface of commercial atomic force microscopy (AFM) probes loses its hydrophilicity by adsorption of airborne and package-released hydrophobic organic contaminants. Cleaning of the probes by acid piranha solution or discharge plasma removes the contaminants and renders very hydrophilic probe surfaces. Time-of-flight secondary-ion mass spectroscopy and X-ray photoelectron spectroscopy investigations showed that the native silicon oxide films on the AFM probe surfaces are completely covered by organic contaminants for the as-received AFM probes, while the cleaning methods effectively remove much of the hydrocarbons and silicon oils to reveal the underlying oxidized silicon of the probes. Cleaning procedures drastically affect the results of adhesive force measurements in water and air. Thus, cleaning of silicon surfaces of the AFM probe and sample cancelled the adhesive force in deionized water. The significant adhesive force values observed before cleaning can be attributed to formation of a bridge of hydrophobic material at the AFM tip-sample contact in water. On the other hand, cleaning of the AFM tip and sample surfaces results in a significant increase of the adhesive force in air. The presence of water soluble contaminants at the tip-sample contact lowers the capillary pressure in the water bridge formed by capillary condensation at the AFM tip-sample contact, and this consequently lowers the adhesive force.

Quantitative oral dosing of water soluble and lipophilic contaminants in the Japanese medaka ( Oryzias latipes)

Quantitative oral dosing in fish can be challenging, particularly with water soluble contaminants, which can leach into the aquarium water prior to ingestion. We applied a method of bioencapsulation using newly hatched brine shrimp ( Artemia franciscana) nauplii to study the toxicokinetics of five chlorinated and brominated halogenated acetic acids (HAAs), which are drinking water disinfection by-products. These results are compared to those obtained in a previous study using a polybrominated diphenyl ether (PBDE-47), a highly lipophilic chemical. The HAAs and PBDE-47 were bioencapsulated using freshly hatched A. franciscana nauplii after incubation in concentrated solutions of the study chemicals for 18 h. Aliquots of the brine shrimp were quantitatively removed for chemical analysis and fed to individual fish that were able to consume 400–500 nauplii in less than 5 min. At select times after feeding, fish were euthanized and the HAA or PBDE-47 content determined. The absorption of HAAs was quantitatively similar to previous studies in rodents: rapid absorption with peak body levels occurring within 1–2 h, then rapidly declining with elimination half-life of 0.3–3 h depending on HAA. PBDE-47 was more slowly absorbed with peak levels occurring by 18 h and very slowly eliminated with an elimination half-life of 281 h.

Optimisation of the Solid-Contact Test with Arthrobacter globiformis (7 pp)

Background, Aim and Scope A number of biotests are available for the characterisation of solid matters such as soil or sediment. Among these, bacterial biotests using single test species often analyse the toxicity of water-soluble contaminants in aquatic extracts, but there is also a need for a fast and inexpensive bacterial solid-contact test. In this study, a solid contact test with added bacteria (Arthrobacter globiformis) was optimised (through miniaturization) for the development of a test kit with conserved bacteria. As in other tests, the results can be influenced by natural soil factors, often masking anthropogenic impacts. For this reason, a further goal of this study was the investigation of the influence of natural soil characteristics on the result of the solid contact test. The project is part of the joint research project 'Optimization of ecotoxicological test methods for routine use' (abbreviated as ERNTE-Forschungsvorhaben: 0330305). Materials and Methods: This method is based on an existing German standard (DIN 38412 L 48) using Arthrobacter globiformi for testing whole soils and sediments. The test principle is the measurement of the dehydrogenase activity of the test organism A. globiformis after an incubation time of two hours with the solid material. To attain the miniaturization in microplates, dye measurement was changed from spectrophotometrical determination of the substrate resazurine to the fluorimetric measurement of the product resorufin. A second step towards optimisation was the use of freeze-dried bacteria. Seven selected uncontaminated soils were tested in order to determine the influence of natural soil characteristics on the results of the solid contact test with A. globiformis. Freshly spiked and polluted field soils were analysed in order to obtain information about the sensitivity of the test. Results: It is possible to perform the contact test in microplates. The fluorimetric dye measurement can be carried out in the presence of the solid material, so the work-intensive step of centrifugation and filtration is no longer necessary. The measurement in the optimised contact test is based on the kinetics of the enzyme reaction. The investigation showed that conserved bacteria have the same activity and sensitivity as cultivated bacteria. Discussion: The study of the uncontaminated soils demonstrated the influence of various soil characteristics on the results of the solid contact test. This information is the basis for the selection of the control and reference soils and is crucial for setting the threshold value in toxicity testing. The investigation of freshly spiked and contaminated soils showed a different sensitivity dependent on the kind of the contamination. Conclusions: The solid contact test was successfully optimised using microplates, whereas now less than six hours are necessary for the analysis. The optimised test is rapid and sensitive, requiring small samples and no stock culture of the bacteria A. globiformis if using freeze-dried bacteria. In this study, the effect of natural soil factors such as pH-value was shown. This information is used to define the threshold value for toxicity. Therefore, the optimised contact test can be used for an efficient assessment of soil or soil substrates. Further studies will clear up if this optimisation is also valid for aquatic sediments and waste. Recommendations and Perspectives: Due to its short analysis time, the test is suitable for screening different kinds of solid matter and can be used for on-site analysis. - The optimised contact test with freeze-dried bacteria as part of a battery of tests is appropriate for the assessment of contaminated soils, sediments and waste.

Freezing To Preserve Groundwater Samples and Improve Headspace Quantification Limits of Water-Soluble Organic Contaminants for Carbon Isotope Analysis

Few systematic investigations have addressed the use of freezing for applications in analytical chemistry. Here, we tested its potential to preserve groundwater samples and to improve headspace quantification limits for compound-specific isotope analysis. Analysis of compound concentrations, as well as stable carbon isotope ratios, confirmed that trichloroethene was preserved in frozen suspensions of nanoscale zerovalent iron. In contrast, storage at 7 degrees C was ineffective, and complete degradation of TCE occurred in 4 weeks. Hence, freezing may stop even abiotic chemical reactions that would not be prevented by cooling or traditional preservation agents. In the absence of iron, we found that headspace concentrations of 14 organic contaminants were considerably higher over frozen solutions than at 25 degrees C, likely reflecting a freezing-out effect governed by Raoult's law. The observed enhancement depended on the salinity of the samples and was strongest for water-soluble, volatile compounds (values in brackets indicate the minimum observed effect out of six replicates): tert-butyl alcohol (TBA, 35-fold), methyl tert-butyl ether (MTBE, 14-fold), 1,2-dichloroethane (10-fold), or benzene (7-fold). In contrast, little enhancement was observed for less water-soluble compounds, such as tetrachloroethene. Although standard deviations of the measurements were too high for the method to be used for quantitative analysis of total compound concentrations, since we found that freezing introduces no measurable carbon isotope effect for TBA, MTBE, 1,2-dichloroethane, and benzene, the method is an effective way of increasing the sensitivity of compound-specific isotope analysis, particularly of water-soluble organic contaminants.

ELISE NMR: Experimental liquid sealing of NMR samples

We present a simple, generally applicable approach to prevent sample evaporation when working at elevated temperatures in high resolution NMR. It consists of experimentally sealing the NMR sample by a second liquid (Experimental Liquid Sealing, ELISE). For aqueous samples, we identified the mineral oil commonly used in PCR application as the best candidate, because it contains only a very limited amount of water-soluble contaminants, is stable over time and heat resistant. The procedure does not interfere with shim settings, and is compatible with a wide variety of samples, including oligosaccharides and proteins. For chloroform samples, a simple drop of water allows to efficiently seal the sample, avoiding solvent evaporation even over lengthy time periods.