Chemical and physicochemical characteristics of humic acids extracted from compost, soil and amended soil

In order to gain understanding about how “HA-like substances” from organic amendments may change some properties in the soil solution, the knowledge of chemical and physicochemical characteristics (charge development, acid–base behavior and heterogeneity) should be known.

The aim of this research were (i) to study the elemental and functional composition, (ii) to determine charge behavior, acid–base properties (apparent dissociation constant and buffer capacity) and (iii) to evaluate heterogeneity of humic acids (HA) isolated from municipal solid waste compost (MWC) and from the corresponding MWC-amended soil, in comparison to those of the unamended soil HA using potentiometric titration and differential scanning potentiometry (DSP).

Potentiometric titration and the first derivative of −Q versus pH (negative charge development versus pH) curves could be used to determine proton-affinity distribution and the chemical heterogeneity of the HA as well as the average pK_app and buffer capacity in a wide range of pH.

Differential scanning potentiometry allows determination of the pK_app values in a narrower range of pH than potentiometric titrations and is another simple methodology to study acid–base behavior of HA.

DSP allows us to determine seven different pK_app values for HA-S and HA-E and four different pK_app for HA-C. Each one of these values corresponds to known acidic groups that can be present in the macromolecule of HA.     

Differences between super-centrifuged and membrane-filtrated soil solutions obtained from bulked and non-bulked topsoils by soil centrifugation

The composition of the soil solution must be known to estimate the mobility and availability of plant nutrients and contaminants. When soil centrifugation is used to obtain the soil water for analysis, bulked soil samples are normally used in order to reduce random variations. In the present study, large systematic differences between the centrifugates from bulked and core samples are reported. For most of the soil solution components, no, or only small differences could be detected between super-centrifuged and membrane-filtrated solutions.     

Differences between super-centrifuged and membrane-filtrated soil solutions obtained from bulked and non-bulked topsoils by soil centrifugation

The composition of the soil solution must be known to estimate the mobility and availability of plant nutrients and contaminants. When soil centrifugation is used to obtain the soil water for analysis, bulked soil samples are normally used in order to reduce random variations. In the present study, large systematic differences between the centrifugates from bulked and core samples are reported. For most of the soil solution components, no, or only small differences could be detected between super-centrifuged and membrane-filtrated solutions.     

Corrosion of underground pipelines in clay soil with varied soil layer thicknesses and aerations

Underground pipelines suffer from corrosion in the soil. In this work, weight-loss testing, electrochemical measurements and surface analysis techniques were used to investigate the pipeline steel corrosion in a Regina clay soil with varied soil layer thicknesses and gassing conditions (i.e., aerobic, CO₂-containing and anaerobic). Results demonstrate that the steel corrosion is dependent on the soil layer thickness, where a maximum corrosion rate is recorded under the 5 mm thick soil due to the competitive impact of the blocking effect of the soil layer and its moisture-retaining ability on the corrosion. In thin soil layers, the corrosion is accelerated with the increasing soil thickness due to more water contained in the soil. With the further increase of the soil layer thickness, the blocking effect of the soil on diffusion of corrosive species is dominant. The corrosion of the steel also depends heavily on the gassing condition in the soil. Under the specific soil layer thickness, the steel suffers from the highest corrosion rate in aerobic soil, which is followed by the 5% CO₂/N₂-containing soil. The steel corrosion is negligible (0.006 mm/y only) when the soil is purged with N₂. In addition to uniform corrosion, localized corrosion occurs on the steel under soil due to its heterogeneous nature at a much greater rate than the uniform corrosion. The maximum localized corrosion rates in 5% CO₂/N₂-containing 5 mm thick soil layer and in the 3 mm thick soil that is open to air are 1.03 mm/y and 0.72 mm/y, respectively. As a comparison, the uniform corrosion rates are 0.05 mm/y and 0.04 mm/y under the two conditions.     

Bioenergetics and bioremediation of contaminated soil

The microbial biodegradation of xenobiotic compounds in soil and ground water is constrained by the laws of thermodynamics. Bioremediation is being investigated in a rhizosphere environment in which higher plants provide carbon and energy to sustain the microbial population. Toluene, phenol, trichloroethylene and trichloroethane have been fed in separate experiments to a pilot scale system with alfalfa growing in sandy soil containing less than 10% of silt. It is well known that microbial populations are numerous in the root zone of healthy vegetation. Root exudates can stimulate aerobic microbial biodegradation of compounds which by themselves support growth poorly or not at all. Polynuclear aromatic compounds such as phenanthrene, anthracene, and pyrene, which are not very soluble in water, and chlorinated aliphatic hydrocarbons such as trichloroethylene are examples of compounds that can be biodegraded in the rhizosphere when root exudates are present to enhance and sustain microbial activity. Solar driven transport processes such as water and solute movements due to evapotranspiration increase the likelihood that the contaminants will come into contact with the microorganisms and be degraded. The thermodynamic and bioenergetic aspects of transport and biodegradation in the rhizosphere are examined through a review of the literature and the analysis of experimental data collected in the pilot scale system.     

Quality assurance and quality control in forest soil analyses: a comparison between European soil laboratories

In transnational monitoring programmes, a balance between international reference methods, which improve spatial comparability, and national analysis methods that favour temporal comparability, by their use and testing over many years, needs to be sought. Prior to the next Pan-European Forest Soil Survey, a third interlaboratory comparison of soil analysis methods was organised. All participating laboratories were requested to use the same reference methods. Fifty-two soil laboratories from 27 European countries analysed a total of 48 soil parameters on three soil samples which were typical for European forest soils. The results of the statistical analysis showed a high interlaboratory and intralaboratory variability, especially for the acid oxalate extractions, particle size distribution, exchangeable elements and total carbonates. The intercomparability of the test results did not improve compared to the previous ring test. As the exercise aimed primarily at comparing the performance of the laboratories, it was not powerful enough to find cause–effect relationships between the meta information provided by the laboratories and the variability of the test results.     

Managed bioremediation of soil contaminated with crude oil soil chemistry and microbial ecology three years later

Analysis of samples taken from three experimental soil lysimeters demonstrated marked long-term effects of managed bioremediation on soil chemistry and on bacterial and fungal communities 3 yr after the application of crude oil or crude oil and fertilizer. The lysimeters were originally used to evaluate the short-term effectiveness of managed (application of fertilizer and water, one lysimeter) vs unmanaged bioremediation (one lysimeter) of Michigan Silurian crude oil compared to one uncontaminated control lysimeter. Three years following the original experiment, five 2-ft-long soil cores were extracted from each lysimeter, each divided into three sections, and the like sections mixed together to form composited soil samples. All subsequent chemical and microbiological analyses were performed on these nine composited samples. Substantial variation was found among the lysimeters for certain soil chemical characteristics (% moisture, pH, total Kjeldahl nitrogen [TKN], ammonia nitrogen [NH₄-N], phosphate phosphorous [PO₄-P], and sulfate [SO₄ ⁻²]). The managed lysimeter had 10% the level of total petroleum hydrocarbons (TPH-IR) found in the unmanaged lysimeter. Assessment of the microbial community was performed for heterotropic bacteria, fungi, and aromatic hydrocarbon-degrading bacteria (toluene, naphthalene, and phenanthrene) by dilution onto solid media. There was little difference in the number of heterotrophic bacteria, in contrast to counts of fungi, which were markedly higher in the contaminated lysimeters. Hydrocarbon-degrading bacteria were elevated in both oil-contaminated lysimeters. In terms of particular hydrocarbons as substrates, phenanthrene degraders were greater in number than naphthalene degraders, which outnumbered toluene degraders. Levels of sulfate-reducing bacteria seem to have been stimulated by hydrocarbon degradation.     

Occurrence of bromine in plants and soil

The usefulness of X-ray fluorescence analysis for the determination of bromine in soil and plants is demonstrated by comparing the results with those obtained by activation analysis. An abnormal accumulation of bromine in some soils, plants and cigarettes has been found. Volcanic ash soil accumulates bromine in its humic acid. The large ratio of chlorine to bromine in river water may be explained by the accumulation of bromine in humus of soil. The possibility of bromine contamination of food and cigarettes, due to the application of agricultural chemicals, is pointed out.     

Application of solid phase microextraction for the determination of soil fumigants in water and soil samples

The potential of solid phase microextraction (SPME) for the determination of the soil fumigants 1,3-dichloropropene (1,3-DCP) and methyl isothiocyanate (MITC) in environmental samples such as soil and water samples has been investigated. Direct immersion SPME followed by GC/ECD/NPD analysis allowed the rapid determination of the two fumigants in water samples, with very little sample manipulation, giving an LOD of 0.5 microg L(-1). Precision, calculated as relative standard deviation (RSD) for six replicates at three concentration levels, was found to be lower than 20% at the concentration levels tested. For the analysis of soil samples, headspace (HS)-SPME combined with GC/ECD/NPD analysis has been applied. Quantification using matrix-matched calibration curves allowed determination of both analytes (MITC and 1-3-DCP) with a LOD of 0.1 microg kg(-1) (RSD < 10%) for the two concentration levels assayed (0.02 and 0.2 mg kg(-1)). The HS-SPME procedure developed in this paper was applied to soil samples from experimental green house plots treated with metham-Na, a soil disinfestation agent that decomposes in soil to MITC. The absence of sample manipulation as well as the low solvent consumption in SPME methodology are among the main advantages of this analytical approach.     

Vertical distribution of the natural and artificial radionuclides in various soil profiles to investigate soil erosion

Vertical distributions of ¹³⁷Cs and ²¹⁰Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From ¹³⁷Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t^.ha^-1.y^-1 and from 79.9 to 3.5 t^.ha^-1.y^-1, respectively. The ²¹⁰Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region.     

Relationships of labile pool of Mn with some general soil properties and extractable soil Mn contents

Labile pool (E-value) of Mn and extractable soil Mn content using six multinutrient extractants were estimated in fifty surface (0–15 cm) soil samples. Labile pool of Mn was poorly correlated to the general soil properties and modified Olsen’s-; 0.01 M CaCl₂- and 1 M MgCl₂-extractable Mn contents but it was positively and significantly correlated to diethylene triamine pentaacetic acid (DTPA), pH 7.3; ammonium bicarbonate + DTPA (pH 7.6); and Mehlich-3-extractable soil Mn contents. The multinutrient extractants involving only simple salt solutions were not useful to assess the availability of Mn in soils.     

Quality assurance and quality control in forest soil analyses: a comparison between European soil laboratories

In transnational monitoring programmes, a balance between international reference methods, which improve spatial comparability, and national analysis methods that favour temporal comparability, by their use and testing over many years, needs to be sought. Prior to the next Pan-European Forest Soil Survey, a third interlaboratory comparison of soil analysis methods was organised. All participating laboratories were requested to use the same reference methods. Fifty-two soil laboratories from 27 European countries analysed a total of 48 soil parameters on three soil samples which were typical for European forest soils. The results of the statistical analysis showed a high interlaboratory and intralaboratory variability, especially for the acid oxalate extractions, particle size distribution, exchangeable elements and total carbonates. The intercomparability of the test results did not improve compared to the previous ring test. As the exercise aimed primarily at comparing the performance of the laboratories, it was not powerful enough to find cause–effect relationships between the meta information provided by the laboratories and the variability of the test results.

     

Bromine residues in the soil and fruits of certain crops after soil fumigation with methyl bromide

Dried fruits of pole beans, cucumber and tomatoes taken from plants in a plastic house on treated and untreated soils with methyl bromide were analyzed for their Br content by X-ray fluorescence (XRF) spectroscopy. Fumigation rates were 0, 450 900, 1350 kg/Ha. Two samples were analyzed at three-week intervals. The highest Br residue in the fruits analyzed was 17.3 ppm. This residue is below the tolerance set by the U.S.D.A. and FAO/WHO. In the treated and untreated soils, the highest Br content was 61.9 and 15.4 ppm, respectively. In general there was a decrease in Br residues in both fruits and treated soil with time. There were no visual phytotoxicity effects even with the highest rate of fumigation.     

Arsenic in contaminated soil and river sediment

Different areas in the Erzgebirge mountains are contaminated by high arsenic concentration which is caused by the occurrence of ore and industrial sources. The study showed clearly a high concentration of arsenic in the surface and under soil (A and B horizons) in the Freiberg district. The distribution of the arsenic concentration in the area, the content of water soluble arsenic, the several oxidation states (As³⁺, As⁵⁺) and the bonding types have been analyzed.     

Determination of I-129 and I-127 in soil and tracer experiments on the adsorption of iodine on soil

Neutron activation analysis of¹²⁹I and¹²⁷I in soil has been studied. The limit of detection for¹²⁹I in soil was about 0.05 mBq/kg or 1×10^–9 as¹²⁹I/¹²⁷I atom ratio. The range of¹²⁹I concentration in surface soils collected around Tokaimura (Ibaraki Prefecture) was 0.9–41 mBq/kg.Tracer experiments on the adsorption of iodine were also carried out, in order to obtain information on the behaviour of iodine in soil-water systems. Different adsorption patterns of iodide and iodate on soil were found. It was supposed that iodide was adsorbed by the soil fraction which became unstable at about 200° C and iodate by the fraction which was relatively stable to heating.     

Determination of sugar cane herbicides in soil and soil treated with sugar cane vinasse by solid-phase extraction and HPLC-UV

This work reports on the development and validation of a small-scale and efficient SPE-HPLC-UV method for the simultaneous determination of the most used herbicides (diuron, hexazinone, and tebuthiuron) applied to soil and soil treated with sugar cane vinasse (soil-vinasse) in areas where sugar cane crops are grown in the state of São Paulo, Brazil. The analytical procedure was optimized for solvent extraction and HPLC-UV conditions. Extraction and clean-up were combined in a single step employing solid-phase extraction, avoiding sophisticated techniques, organic-solvent-water mixtures and consequently a longer concentration step. Recovery studies with soil and soil-vinasse samples spiked at two herbicides levels (around 0.25 and 2.0 mg kg⁻¹) and sample stability (sample frozen for 20 days before analysis) were applied as parameters to control the efficiency of the method. Good accuracy and precision were achieved with average recoveries ranging from 78% to 120% and relative standard deviations less than 10% throughout the whole recovery test. The method's limit of detection ranged between 0.025 and 0.050 mg kg⁻¹ for diuron, hexazinone, and tebuthiuron in soil and soil-vinasse. The feasibility of this method was applied to determine the herbicide half-lives (t_1/2) in soil and soil-vinasse in a laboratory study. Sugar cane vinasse added to soil increased the degradation of diuron and tebuthiuron (p < 0.05), reducing the t_1/2 from 80 to 7 days and 128 to 73 days, respectively. This method is presented as an alternative which could be applied to assess herbicide behavior in soil in order to prevent water contamination and to contribute to establish pesticide limits in soil.     

Physicochemical fractionation of americium, thorium, and uranium in Chernozem soil after sharp temperature change and soil drought

A sequential extraction procedure was used to study the changes in the physicochemical forms of americium (Am), thorium (Th), and uranium (U) in laboratory-contaminated Chernozem soil as a result of sharp variations of the environmental temperature and soil moisture. The influence of freezing and soil drought on the radio-ecological hazard was evaluated three months after radioactive contamination with aqueous solutions of ²⁴¹Am, ²³⁴Th, and U. The subsequent changes in the physicochemical forms of the actinides, caused by sharp increases in the environmental temperature and soil moisture, were examined for one month. The data showed that continuous freezing increased the potentially mobile forms of Am and Th but had the opposite effect on U. Prolonged soil drought did not influence the fractionation of Am and Th but led to the redistribution of U between the carbonates and organic matter and caused its immobilisation. The sharp increase in the temperature of the frozen soil caused the immobilisation of Am and Th and increased the potential mobility of U. The warming and enhanced humidity of the dry soil led to the immobilisation of Am and redistribution of U between the soil phases.     

Prediction of soil organic carbon partition coefficients by soil column liquid chromatography

To avoid the limitation of the widely used prediction methods of soil organic carbon partition coefficients (KOC) from hydrophobic parameters, e.g., the n-octanol/water partition coefficients (KOW) and the reversed phase high performance liquid chromatographic (RP-HPLC) retention factors, the soil column liquid chromatographic (SCLC) method was developed for KOC prediction. The real soils were used as the packing materials of RP-HPLC columns, and the correlations between the retention factors of organic compounds on soil columns (ksoil) and KOC measured by batch equilibrium method were studied. Good correlations were achieved between ksoil and KOC for three types of soils with different properties. All the square of the correlation coefficients (R2) of the linear regression between log ksoil and log KOC were higher than 0.89 with standard deviations of less than 0.21. In addition, the prediction of KOC from KOW and the RP-HPLC retention factors on cyanopropyl (CN) stationary phase (kCN) was comparatively evaluated for the three types of soils. The results show that the prediction of KOC from kCN and KOW is only applicable to some specific types of soils. The results obtained in the present study proved that the SCLC method is appropriate for the KOC prediction for different types of soils, however the applicability of using hydrophobic parameters to predict KOC largely depends on the properties of soil concerned.