Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments of a Brazilian subtropical microbasin

International audienceHumic substances (HS) perform a fundamental role in aquatic environments, exhibiting different levels of reactivity in retaining metal ions and organic pollutants. Also, they control the primary production of these ecosystems and act in the carbon sequestering process. In order to improve our understanding vis-à-vis the structural and functional features of HS from aquatic systems, this study aimed to chemically and spectroscopically characterize humic acids (HA) isolated from bottom sediment samples of a stream in a Brazilian subtropical microbasin by elemental analysis, and infrared (FT-IR), ultraviolet and visible (UV-Vis) and solid-state 13C nuclear magnetic resonance (CP-MAS 13C NMR) spectroscopies, thermogravimetry (TG), and scanning electron microscopy (SEM). Although all samples originated from the same environment, the data showed that the HA have distinct chemical and spectroscopic properties, and that the location and characteristics of the sampling points from which the sediments were collected played an important role in the differences observed. Furthermore, vascular plant matter is probably the main contributor to these samples

THE EVOLUTION OF PLANT BIOMASS IN SOIL POLLUTED WITH CRUDE OIL IN DIFFERENT EXPERIMENTAL VARIANTS

Soil acidity is among the important environmental factors which can influence plant growth and can seriously limit crop production. Therefore, liming acid soils is basic to maintain an optimal pH. Soil pH has a large influence on the availability of plants nutrients. The steel slag can be used as an amendment for an acid soil considering the high contents of CaO and MgO. The paper presents the preliminary obtained data regarding the use of steel slag resulted as a metallurgical waste from a Romanian steel refinery and its effect on the soil pH. The physical and chemical characteristics of the acid soil are presented. The effects of the steel slag applied at different rates on soil pH have been investigated in the laboratory experiment

Trace metals dynamics in surface sediments investigated by DGT micro-scale measurements

In surface sediments, metal mobility is controlled by the recruitment and turn-over of organic matter whereas sulphide is thought to control the concentration of metals in sediment pore water by removing them from the solution. DGT is a dynamic probe that measures the kinetically available fraction of metals or sulphide. DGT uses a credit card size probe inserted into the sediment that provides a snapshot of the metal distribution in the sediment, which can be uncovered by spectrochemical analytical techniques. In-situ vertical profiles and horizontal maps of trace metals at high (mm scale) and ultra-high resolution (100 $\mu$m) together with Fe, Mn and sulphide were generated from DGT probes deployed in surface sediments. Collectively, the results showed that besides vertical gradients, associated with the depletion of oxygen with depth and the degradation of organic matter by a succession of electron acceptors, small scale remobilisation of metals associated with sediment heterogeneity take place

Statistical learning theory for geospatial data. Case study: Aral sea

In recent years there has been an explosive growth in the development of adaptive and data driven methods. One of the efficient and data-driven approaches is based on statistical learning theory (Vapnik 1998). The theory is based on Structural Risk Minimisation (SRM) principle and has a solid statistical background. When applying SRM we are trying not only to reduce training error ? to fit the available data with a model, but also to reduce the complexity of the model and to reduce generalisation error. Many nonlinear learning procedures recently developed in neural networks and statistics can be understood and interpreted in terms of the structural risk minimisation inductive principle. A recent methodology based on SRM is called Support Vector Machines (SVM). At present SLT is still under intensive development and SVM find new areas of application (www.kernel-machines.org). SVM develop robust and non linear data models with excellent generalisation abilities that is very important both for monitoring and forecasting. SVM are extremely good when input space is high dimensional and training data set i not big enough to develop corresponding nonlinear model. Moreover, SVM use only support vectors to derive decision boundaries. It opens a way to sampling optimization, estimation of noise in data, quantification of data redundancy etc. Presentation of SVM for spatially distributed data is given in (Kanevski and Maignan 2004)

Determination of palladium, platinum and rhodium concentrations in urban road sediments by laser ablation-ICP-MS.

The introduction of catalytic converter technology to cars has alleviated gaseous exhaust emissions but in turn has resulted in emissions of the three platinum group metals (PGMs), Pd, Pt and Rh, contained in the automobile catalyst. The environmental effects of PGMs are still largely unknown and their accurate determination is particularly difficult because concentrations are at trace levels. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a direct trace element measurement technique and can be used for the rapid characterization of metals in solid environmental matrices. Here, the capability of LA-ICP-MS for the direct quantitative determination of PGMs in road sediments was assessed. Two Nd:YAG laser systems operating at 266 and 1064 nm, respectively, were coupled to an ICP-MS. Uncontaminated road sediments were spiked with PGMs, both as solution and as solid certified reference material, and used to assess the analytical performance of the technique and to calibrate the instrument. Interferences due to the formation of molecular ions and double charged ions were investigated. The LA-ICP-MS was then used to determine the concentration of PGMs in a recent urban road sediment and the results were compared with high resolution-ICP-MS measurements after microwave sample digestion with Aqua Regia. The LA-ICP-MS allows the quantitative analysis of Pd, Pt, and Rh in road sediments at sub microgram per gram levels with a relative standard deviation of 10% and with estimated detection limits in the lower nanogram per gram range. Good agreement between LA-ICP-MS and HR-ICP-MS analysis could be obtained for Pt and Rh (<3% R.S.D. at ca. 100 ng g−1) whereas the determination of Pd remains subject to interferences

Quantitative Determination of Fluoroquinolones in Contaminated Soils by HPLC with Solid-Phase Extraction

International audienceThis work reports the development of an analytical method for the simultaneous analysis of three fluoroquinolones; ciprofloxacin (CIP), norfloxacin (NOR) and ofloxacin (OFL) in soil matrix. The proposed method was performed by using microwave-assisted extraction (MAE), solid-phase extraction (SPE) for samples purification, and finally the pre-concentrated samples were analyzed by HPLC detector. In this study, various organic solvents were tested to extract the test compounds, and the extraction performance was evaluated by testing various parameters including extraction solvent, solvent volume, extraction time, temperature and number of the extraction cycles. The current method showed a good linearity over the concentration ranging from 1 – 300ng g-1 with correlation coefficients (r2 > 0.998) for all test compounds. Good recoveries were also obtained for the test compounds ranged from 89 – 99 %. The relative standard deviation (RSD) from intra-day and inter-day precision was lower than 7%, and the detection (LOD) and quantification (LOQ) limits ranged from 0.9 – 2.7ng g-1.Finally, the proposed method was applied to determine the target compounds in real soil samples irrigated with wastewater. The results confirm the presence of the test compounds in soils with values ranging from 1.9 – 4.6ng g-1, as well as the suitability of the proposed method to determine the test compounds in real soil matrix as well as the ability of the test compounds to accumulate in soils irrigated with sewag

Evaluation of Samarium Doped Hydroxyapatite, Ceramics for Medical Application: Antimicrobial Activity

Samarium doped hydroxyapatite (Sm:HAp), Ca10-xSmx(PO4)6(OH)2 (HAp), bionanoparticles with different xSm have been successfully synthesized by coprecipitation method. Detailed characterization of samarium doped hydroxyapatite nanoparticles (Sm:HAp-NPs) was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The biocompatibility of samarium doped hydroxyapatite was assessed by cell viability. The antibacterial activity of the Sm:HAp-NPs was tested against Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus). A linear increase of antimicrobial activity of P. aeruginosa has been observed when concentrations of Sm:HAp-NPs in the samples with xSm=0.02 were higher than 0.125 mg/mL. For Sm:HAp-NPs with xSm=0.05 a significant increase of antibacterial activity on E. coli was observed in the range 0.5–1 mg/mL. For low concentrations of Sm:HAp-NPs (xSm=0.05) from 0.031 to 0.125 mg/mL a high antibacterial activity on Enterococcus faecalis has been noticed. A growth of the inhibitory effect on S. aureus was observed for all concentrations of Sm:HAp-NPs with xSm=0.02

Simultaneous release of sulphide with Fe, Mn, Ni and Zn in marine harbour sediment measured using a combined metal/sulphide DGT probe.

The technique of DGT (Diffusive Gradients in Thin Films) was further developed to allow simultaneous measurement of sulfide and trace metals at the same location in sediment. The new combined DGT probe consisted of a layer of gel impregnated with AgI, overlain by (1) a layer of gel containing Chelex, (2) a layer of gel and (3) a filter membrane. Diffusion of sulfide was controlled by layers (1) to (3), while diffusion of metals was controlled by layers (2) and (3). The Chelex gel trapped metals that were measured after elution with acid. The AgI gel trapped sulfide through the formation of Ag2S. This was then measured densitometrically as the colour changed from pale yellow to grey. Experiments demonstrated that concentrations of metal or sulfide measured by the combined device were no different to the concentrations measured by more conventional devices. The presence of Chelex in the gel did not impede the diffusion of sulfide. Deployment of a combined probe in marine sediment revealed simultaneous remobilisation of metals and sulfide at the same location. Solubility calculations indicated that some precipitation of amorphous FeS was probably occurring at the maxima in sulfide concentrations. There was general undersaturation with respect to NiS, but ZnS was supersaturated at all locations. There appeared to be localised active zones of organic matter decomposition, where reduction of manganese oxides, iron oxides and sulfate occurred simultaneously. Mass balance calculations indicated that Ni could not be supplied by release from decomposing organic matter. Manganese oxides were the most likely source, but supply from reductive dissolution of iron oxides could not be entirely discounted. Supply from either Fe or Mn oxides could account for the Zn maxima. Application of the newly developed combined probe provides new information that helps understanding of the complex nature of trace metal and sulfur chemistry in sediments