Developing a fluorimetric sequential injection methodology to study adsorption/desorption of glyphosate on soil and sediment samples

This paper describes the development of a sequential injection method to automate the fluorimetric determination of glyphosate based on a first step of oxidation to glycine by hypochlorite at 48 degrees C, followed by reaction with the fluorogenic reagent o-phthaldialdehyde in presence of 2-mercaptoethanol in borate buffer (pH > 9) to produce a fluorescent 1-(2`-hydroxyethylthio)-2-N-alkylisoindole. The proposed method has a linear response for glyphosate concentrations between 0.25 and 25.0 mu mol L(-1), with limits of detection and quantification of 0.08 and 0.25 mu mol L(-1), respectively. The sampling rate of the method is 18 samples per hour, consuming only a fraction of reagents consumed by the chromatographic method based on the same chemistry. The method was applied to study adsorption/desorption properties in a soil and in a sediment sample. Adsorption and desorption isotherms were properly fitted by Freundlich and Langmuir equations, leading to adsorption capacities of 1384 +/- 26 and 295 +/- 30 mg kg(-1) for the soil and sediment samples, respectively. These values are consistent with the literature, with the larger adsorption capacity of the soil being explained by its larger content of clay minerals, while the sediment was predominantly sandy. (C) 2011 Elsevier B.V. All rights reserved.

Development, validation, and application of a method for the GC-MS analysis of fipronil and three of its degradation products in samples of water, soil, and sediment

A method for the identification and quantification of pesticide residues in water, soil, and sediment samples has been developed, validated, and applied for the analysis of real samples. The specificity was determined by the retention time and the confirmation and quantification of analyte ions. Linearity was demonstrated over the concentration range of 20 to 120 µg L(-1), and the correlation coefficients varied between 0.979 and 0.996, depending on the analytes. The recovery rates for all analytes in the studied matrix were between 86% and 112%. The intermediate precision and repeatability were determined at three concentration levels (40, 80, and 120 µg L(-1)), with the relative standard deviation for the intermediate precision between 1% and 5.3% and the repeatability varying between 2% and 13.4% for individual analytes. The limits of detection and quantification for fipronil, fipronil sulfide, fipronil-sulfone, and fipronil-desulfinyl were 6.2, 3.0, 6.6, and 4.0 ng L(-1) and 20.4, 9.0, 21.6, and 13.0 ng L(-1), respectively. The method developed was used in water, soil, and sediment samples containing 2.1 mg L(-1) and 1.2% and 5.3% of carbon, respectively. The recovery of pesticides in the environmental matrices varied from 88.26 to 109.63% for the lowest fortification level (40 and 100 µg kg(-1)), from 91.17 to 110.18% for the intermediate level (80 and 200 µg kg(-1)), and from 89.09 to 109.82% for the highest fortification level (120 and 300 µg kg(-1)). The relative standard deviation for the recovery of pesticides was under 15%.

Vegetation, soil and site characteristics of samples taken along the Yamal Transet in 2007-2008

The overarching goal of the Yamal portion of the Greening of the Arctic project is to examine how the terrain and anthropogenic factors of reindeer herding and resource development combined with the climate variations on the Yamal Peninsula affect the spatial and temporal patterns of vegetation change and how these changes are in turn affecting traditional herding of the indigenous people of the region. The purpose of the expeditions was to collect groundobservations in support of remote sensing studies at four locations along a transect that traverses all the major bioclimate subzones of the Yamal Peninsula. This data report is a summary of information collected during the 2007 and 2008 expeditions. It includes all the information from the 2008 data report (Walker et al. 2008) plus new information collected at Kharasavey in Aug 2008. The locations included in this report are Nadym (northern taiga subzone), Laborovaya (southern tundra = subzone E of the Circumpolar Arctic Vegetation Map (CAVM), Vaskiny Dachi (southern typical tundra = subzone D), and Kharasavey (northern typical tundra = subzone C). Another expedition is planned for summer 2009 to the northernmost site at Belyy Ostrov (Arctic tundra = subzone B). Data are reported from 10 study sites - 2 at Nadym, 2 at Laborovaya, and 3 at Vaskiny Dachi and 3 at Kharasavey. The sites are representative of the zonal soils and vegetation, but also include variation related to substrate (clayey vs. sandy soils). Most of the information was collected along 5 transects at each sample site, 5 permanent vegetation study plots, and 1-2 soil pits at each site. The expedition also established soil and permafrost monitoring sites at each location. This data report includes: (1) background for the project, (2) general descriptions and photographs of each locality and sample site, (3) maps of the sites, study plots, and transects at each location, (4) summary of sampling methods used, (5) tabular summaries of the vegetation data (species lists, estimates of cover abundance for each species within vegetation plots, measured percent ground cover of species along transects, site factors for each study plot), (6) summaries of the Normalized Difference Vegetation Index (NDVI) and leaf area index (LAI) along each transect, (7) soil descriptions and photos of the soil pits at each study site, (8) summaries of thaw measurements along each transect, and (9) contact information for each of the participants. One of the primary objectives was to provide the Russian partners with full documentation of the methods so that Russian observers in future years could repeat the observations independently.

Volume, Surface, Connectivity and Size Distribution of Soil Pore Space in CT Images: Comparison of Samples at Different Depths from Nearby Natural and Tillage Areas

The study of soil structure, i.e., the pores, is of vital importance in different fields of science and technology. Total pore volume (porosity), pore surface, pore connectivity and pore size distribution are some (probably the most important) of the geometric measurements of pore space. The technology of X-ray computed tomography allows us to obtain 3D images of the inside of a soil sample enabling study of the pores without disturbing the samples. In this work we performed a set of geometrical measures, some of them from mathematical morphology, to assess and quantify any possible difference that tillage may have caused on the soil. We compared samples from tilled soil with samples from a soil with natural vegetation taken in a very close area. Our results show that the main differences between these two groups of samples are total surface area and pore connectivity per unit pore volume.

(Table 1) Soil density and concentration of 10Beryllium and 26Aluminium in samples from two ash deposits in the McMurdo Dry Valleys

The McMurdo Dry Valleys, Antarctica (MDV) are among the oldest landscapes on Earth, and some landforms there present an intriguing apparent contradiction such that millions of years old surface deposits maintain their meter-scale morphology despite the fact that measured erosion rates are 0.1-4 m/Ma. We analyzed the concentration of cosmic ray-produced 10Be and 26Al in quartz sands from regolith directly above and below two well-documented ash deposits in the MDV, the Arena Valley ash (40Ar/39Ar age of 4.33 Ma) and the Hart ash (K-Ar age of 3.9 Ma). Measured concentrations of 10Be and 26Al are significantly less than expected given the age of the in situ air fall ashes and are best interpreted as reflecting the degradation rate of the overlying sediments. The erosion rate of the material above the Arena Valley ash that best explains the observed isotope profiles is 3.5 ± 0.41 x 10**-5 g/cm**2/yr (~0.19 m/Ma) for the past ~4 Ma. For the Hart ash, the erosion rate is 4.8 ± 0.21 x 10**-4 g/cm**2/yr (~2.6 m/Ma) for the past ~1 Ma. The concentration profiles do not show signs of mixing, creep, or deflation caused by sublimation of ground ice. These results indicate that the slow, steady lowering of the surface without vertical mixing may allow landforms to maintain their meter-scale morphology even though they are actively eroding.

Radiocarbon dating, carbon storage and soil properties of samples from Tulemalu Lake, central Canadian Arctic

We investigated total storage and landscape partitioning of soil organic carbon (SOC) in continuous permafrost terrain, central Canadian Arctic. The study is based on soil chemical analyses of pedons sampled to 1 m depth at 35 individual sites along three transects. Radiocarbon dating of cryoturbated soil pockets, basal peat and fossil wood shows that cryoturbation processes have been occurring since the Middle Holocene and that peat deposits started to accumulate in a forest-tundra environment where spruce was present (~6000 cal yrs BP). Detailed partitioning of SOC into surface organic horizons, cryoturbated soil pockets and non-cryoturbated mineral soil horizons is calculated (with storage in active layer and permafrost calculated separately) and explored using principal component analysis. The detailed partitioning and mean storage of SOC in the landscape are estimated from transect vegetation inventories and a land cover classification based on a Landsat satellite image. Mean SOC storage in the 0-100 cm depth interval is 33.8 kg C/m**2, of which 11.8 kg C/m**2 is in permafrost. Fifty-six per cent of the total SOC mass is stored in peatlands (mainly bogs), but cryoturbated soil pockets in Turbic Cryosols also contribute significantly (17%). Elemental C/N ratios indicate that this cryoturbated soil organic matter (SOM) decomposes more slowly than SOM in surface O-horizons.

Soil properties and microbial indicators of samples from Lake Wellman, Darwin Mountains, Antarctica

Four pedons on each of four drift sheets in the Lake Wellman area of the Darwin Mountains were sampled for chemical and microbial analyses. The four drifts, Hatherton, Britannia, Danum, and Isca, ranged from early Holocene (10 ka) to mid-Quaternary (c. 900 ka). The soil properties of weathering stage, salt stage, and depths of staining, visible salts, ghosts, and coherence increase with drift age. The landforms contain primarily high-centred polygons with windblown snow in the troughs. The soils are dominantly complexes of Typic Haplorthels and Typic Haploturbels. The soils were dry and alkaline with low levels of organic carbon, nitrogen and phosphorus. Electrical conductivity was high accompanied by high levels of water soluble anions and cations (especially calcium and sulphate in older soils). Soil microbial biomass, measured as phospholipid fatty acids, and numbers of culturable heterotrophic microbes, were low, with highest levels detected in less developed soils from the Hatherton drift. The microbial community structure of the Hatherton soil also differed from that of the Britannia, Danum and Isca soils. Ordination revealed the soil microbial community structure was influenced by soil development and organic carbon.

Preconcentration of polar phenolic compounds from water samples and soil extract by liquid-phase microextraction and determination via liquid chromatography with ultraviolet detection.

2016

Soil management effects on organic carbon in isolated fractions of a Gray Luvisol

Agricultural management affects soil organic matter, which is important for sustainable crop production and as a greenhouse gas sink. Our objective was to determine how tillage, residue management and N fertilization affect organic C in unprotected, and physically, chemically and biochemically protected soil C pools. Samples from Breton, Alberta were fractionated and analysed for organic C content. As in previous report, N fertilization had a positive effect, tillage had a minimal effect, and straw management had no effect on whole-soil organic C. Tillage and straw management did not alter organic C concentrations in the isolated C pools, while N fertilization increased C concentrations in all pools. Compared with a woodlot soil, the cultivated plots had lower total organic C, and the C was redistributed among isolated pools. The free light fraction and coarse particulate organic matter responded positively to C inputs, suggesting that much of the accumulated organic C occurred in an unprotected pool. The easily dispersed silt-sized fraction was the mineral-associated pool most responsive to changes in C inputs, whereas the microaggregate-derived silt-sized fraction best preserved C upon cultivation. These findings suggest that the silt-sized fraction is important for the long-term stabilization of organic matter through both physical occlusion in microaggregates and chemical protection by mineral association.