High Organic Content Soil Research Articles

Determination of N,N-Dialkylethanolamines Related to Chemical Warfare Agents as Benzylated Species in an OPCW Proficiency Test Soil Sample by Electron Ionization Gas Chromatography-Mass Spectrometry

In the field of chemical warfare agents (CWAs), ethanolamines are important building blocks for the preparation of nerve agents belonging to the V-series such as VX and VR as well as the nitrogen-based mustards. In this work, the determination of three members in this class of Schedule 2B reportable chemicals, namely N,N-dimethylethanolamine (DMEA), N,N-diethylethanolamine (DEEA), and N,N-diisopropylethanolamine (DIEA) by electron ionization gas chromatography-mass spectrometry (EI-GC-MS) is presented. The three dialkylethanolamines were spiked in a high organic content soil matrix featured during the 45th Organization for the Prohibition of Chemical Weapons (OPCW) proficiency test (PT) at two separate concentrations each (1 and 10 µg/g separately), simulating values often encountered during these tests. The N,N-dialkylethanolamines were O-alkylated using benzyl bromide and sodium carbonate at 55 °C and were detected as their benzylated versions by electron ionization GC-MS. The benzylation of each dialkylethanolamine yielded derivatives with higher molecular weight and therefore different GC-MS profiles such as longer retention times and sharper peak chromatography relative to their unmodified counterparts. These characteristics enable the analytical chemist to detect and confirm these important CWA-related chemicals specifically in instances where they are present in low concentrations (i.e. <10 µg/g) among more abundant interferences.

Characterization of atmospheric methane release in the outer Mackenzie River delta from biogenic and thermogenic sources

Abstract. The Mackenzie River delta is the second largest Arctic river delta in the world. Thin and destabilizing permafrost coupled with vast natural gas reserves at depth, high organic-content soils, and a high proportion of wetlands create a unique ecosystem conducive to high rates of methane (CH4) emission from biogenic and thermogenic sources. Hotspots are known to have a significant contribution to summertime CH4 emissions in the region. Still, little research has been done to determine how often geologic or biogenic CH4 contributes to hotspots in the Mackenzie River delta. In the present study, stable carbon isotope analysis was used to identify the source of CH4 at several aquatic and terrestrial sites thought to be hotspots of CH4 flux to the atmosphere. Walking transects and point samples of atmospheric CH4 and CO2 concentrations were measured. Source stable carbon isotope (δ13C-CH4) signatures were derived from keeling plots of point samples and ranged from −42 ‰ to −88 ‰ δ13C-CH4, identifying both biogenic and thermogenic sources. A CH4 source was determined for eight hotspots, two of which were thermogenic in origin (−42.5 ‰, −44.7 ‰), four of which were biogenic in origin (−71.9 ‰ to −88.3 ‰), and two of which may have been produced by the oxidation of biogenic CH4 (−53.0 ‰, −63.6 ‰), as evidenced by δ13C-CH4 signatures. This indicates that the largest hotspots of CH4 production in the Mackenzie River delta are caused by a variety of sources.

Polydopamine-coated polyethylene sieve plate as an efficient and convenient adsorption sink for the bioaccessibility prediction of PAHs in soils

Bioaccessibility measurements of polycyclic aromatic hydrocarbons (PAHs) in soils are significant for exposure risk assessment. The current physicochemical methods require tedious operation processes, underestimate the actual risks, or are unsuitable for high organic content soils. In this work, an efficient and convenient method based on polydopamine-coated polyethylene sieve plate (PDA@PESP) and hydroxypropyl-β-cyclodextrin (HPCD) was developed to predict the bioaccessibility of PAHs in multi-type soils. The PDA@PESP can be prepared via in situ self-polymerization, allowing to extract PAHs from HPCD solution quantitatively and rapidly. When applied to evaluate the bioaccessibility with PDA@PESP as an adsorption sink and HPCD as a diffusive carrier, the proposed method can significantly improve the extractable fraction of PAHs compared to single HPCD extraction in particular for high organic carbon content soil and high-ring PAHs. The desorption kinetics data indicated that the method can predict the bioaccessible fraction of PAHs. In addition, the method predicted a satisfactory accumulation into earthworms (Eisenia fetida) with a slope statistically approximated to 1. A highly significant linear regression (R2 = 0.95) was also found between the proposed method and Tenax desorption in historically contaminated soils, demonstrating that the method is an efficient and convenient approach for the bioaccessibility prediction of PAHs in soils.

Effects of soil type, temperature, moisture, application dose, fertilizer, and organic amendments on chemical properties and biodegradation of dimethyl disulfide in soil

AbstractDimethyl disulfide (DMDS) is a potential alternative to methyl bromide for soil fumigation to control soil‐borne disease. Laboratory experiments were conducted to investigate the effects of combinations of soil and environmental factors of DMDS degradation in soil. The results showed that soil pH and soil organic matter content are the major factors influencing the degradation of DMDS in soil. Generally, DMDS degradation was significantly slower in acidic and high organic content soils. The degradation rate increased with temperature and water content. However, when the temperature exceeded 35°C, the degradation rate decreased, and when the soil water content was raised to 10%, the change in DMDS degradation was not significant in Fangshan soil. The degradation of DMDS in soil depended on the initial application rate. Degradation slowed down as the fumigant application rate increased. DMDS degradation in soil was restrained by the addition of organic matter to soil, and the effect was enhanced by increased dosage. DMDS degradation in soil was also restrained by the use of chemical fertilizers except when amended with sodium dihydrogen phosphate and sodium thiosulfate. The impact of fumigant application rates and chemical fertilizers on bacterial communities in soil was determined by 16S rRNA amplicon sequencing. The results showed that bacterial diversity was affected by different treatments. Our study provides useful information to evaluate environmental safety assessments of DMDS in soil.

Pesticide fate modelling in conservation tillage: Simulating the effect of mulch and cover crop on S-metolachlor leaching

Conservation tillage practices mainly based on cover crops and no-tillage with accumulation of crop residues at the soil surface (mulch) modify the environmental fate of pesticides. However, only few pesticide fate models are able to consider mulch of crop residues as well as the effect of intermediate cover crops. Thus, the objective was to develop an approach to model the effects of crop residues left at the soil surface and cover crops on the fate of pesticides. This approach consisted in (1) considering the crop residues as a soil layer with specific physical, hydrodynamic and pesticide-reactivity properties close to that of a high organic content soil layer, and (2) introducing a correction factor of the potential evapotranspiration, estimated through a calibration step, to take into account the reduction of soil evaporation by the presence of a mulch. This approach was developed using MACRO as support pesticide model. To assess the model performances, we used the data from a field experiment designed in an irrigated maize monoculture under conservation tillage. Soil water content, water percolates, soil temperature and S-metolachlor herbicide concentrations in the leachate at 1m depth were measured during two years. The approach chosen to simulate the mulch effects allowed MACRO to make acceptable predictions of the observed water percolation, soil temperature and to a less extent herbicide leaching. However, it showed a poor performance to simulate the soil water content. Results are discussed in terms of further modelling options to better assess the environmental risks of pesticides under conservation tillage. This approach remains to be tested against various soils, crops, pesticides and types of mulch.

Evaluation of solubility of polycyclic aromatic hydrocarbons in ethyl lactate/water versus ethanol/water mixtures for contaminated soil remediation applications

Solubility data of recalcitrant contaminants in cosolvents is essential to determine their potential applications in enhanced soil remediation. The solubilities of phenanthrene, anthracene, fluoranthene and benzo[a]pyrene in ethyl lactate/water and ethanol/water mixtures were measured using equilibrium techniques. The cosolvency powers derived from solubility data were then applied to the model developed from the solvophobic approach to predict the capability of ethyl lactate and ethanol in enhancing the desorption of contaminants from soils. Both ethyl lactate and ethanol cosolvents were shown to be able to enhance the solubilisation of the tested four polycyclic aromatic hydrocarbons by > 4 orders of magnitude above the levels obtained with water alone. However, ethyl lactate demonstrated a greater capacity to enhance PAH solubility than ethanol. The cosolvency powers of ethyl lactate/water system obtained from the end-to-end slope (σ) and the end-to-half slope (σ0.5) of the solubilisation curve were 1.0–1.5 and 2.0–2.9 higher than ethanol/water system respectively. In line with this, ethyl lactate/water was demonstrated to enhance the desorption of contaminants from soil by 20%–37% and 18%–61% higher compared to ethanol/water system in low organic content and high organic content soils respectively, with a 2:1 (V/W) ratio of solution: soil and with cosolvent fraction as low as 0.4. With the exception of benzo[a]pyrene, the experimental desorption results agreed fairly with the predicted values, under an applied solution: soil ratio that was enough to hold the capacity of released contaminants.

Meta‐barcoding of ‘dirt’ DNA from soil reflects vertebrate biodiversity

DNA molecules originating from animals and plants can be retrieved directly from sediments and have been used for reconstructing both contemporary and past ecosystems. However, the extent to which such 'dirt' DNA reflects taxonomic richness and structural diversity remains contentious. Here, we couple second generation high-throughput sequencing with 16S mitochondrial DNA (mtDNA) meta-barcoding, to explore the accuracy and sensitivity of 'dirt' DNA as an indicator of vertebrate diversity, from soil sampled at safari parks, zoological gardens and farms with known species compositions. PCR amplification was successful in the full pH range of the investigated soils (6.2 ± 0.2 to 8.3 ± 0.2), but inhibition was detected in extracts from soil of high organic content. DNA movement (leaching) through strata was evident in some sporadic cases and is influenced by soil texture and structure. We find that DNA from the soil surface reflects overall taxonomic richness and relative biomass of individual species. However, one species that was recently introduced was not detected. Furthermore, animal behaviour was shown to influence DNA deposition rates. The approach potentially provides a quick methodological alternative to classical ecological surveys of biodiversity, and most reliable results are obtained with spatial sample replicates, while relative amounts of soil processed per site is of less importance.

Calibration of a combined dielectric probe for soil moisture and porewater salinity measurement in organic and mineral coastal wetland soils

Accurate measurement of soil moisture ( θ), bulk electrical conductivity ( σ b ), and porewater electrical conductivity ( σ w ) in the vadose zone is critical for a wide range of environmental monitoring applications. The use of combined dielectric probes allows for the automated collection of high-resolution, long-term data, however variation in probe response to different soil types can lead to unacceptably large measurement errors, especially in soils with high organic content such as those found in wetlands. The objectives of this study were to calibrate and field-test a combined, capacitance-based dielectric probe for three soil series encountered in the floodplain of a southeastern (USA) coastal river where watershed modifications have led to reduced freshwater flow and saltwater intrusion. To calibrate the probe, floodplain soils were categorized into three groups: a low organic content fine sand; a moderately organic, depositional fluvent soil; and a highly organic muck. PVC soil cores were packed at field bulk density, and θ and σ b were measured in the lab over a range of soil moistures (pressure potentials of 0–333 cm H 2O) and σ w values (0.01–1.0 S/m). Soil dielectric properties measured with the probe were used to test several potential models relating real and imaginary dielectric constants to θ, σ b , and σ w . Soil-specific calibrations improved θ estimation over standard manufacturer calibrations, particularly for the more organic soils. Of all θ– σ b – σ w models tested, the empirical relationship proposed by Vogeler et al. (1996) performed the best (overall R 2 = 0.97 for the three soils), though all models performed well in all soils (0.94 ≤ R 2 ≤ 0.98) and each can be selected for the specific range of σ b expected in the field. Calibrations were successfully tested in the field by comparing in-ground probe estimates of σ w with collocated soil water samples. These calibrations add to the limited published data available for soils of high organic content and support accurate monitoring of the vadose zone in coastal wetlands to inform restoration and management of these valued ecosystems.

Utilization of Lime for Stabilizing Soft Clay Soil of High Organic Content

This paper presents the results of geotechnical and mineralogical investigations on lime-treated soft clay soil from Idku City, Egypt, where high organic matters of about 14% exist. Lime was added in the order of 1%, 3%, 5% and 7% by weight and laboratory experiments after 7, 15, 30 and 60 days were conducted including the mineralogical and microstructural examinations, grain size analysis, plasticity limits, unconfined compressive tests, vane shear tests and oedometer tests. The results indicate that soft clay soil of high organic content of 14% can be stabilized satisfactorily with the addition of 7% lime. The results also demonstrate that the changes in the mineralogical contents and soil fabric of high organic lime-treated soft clay improve soil plasticity, strength and compressibility.

Late Glacial and Holocene environmental history of a buried ice-wedge system, Barrow, Alaska

The DFG funded project (RI 809/17-1) aims to reconstruct environmental changes in the Eurasian Arctic during the Late Quaternary interstadial and interglacial periods basing on microfossils records from permafrost sequences of NE-Siberia. We present the testate amoebae records from the Cape Mamontovy Klyk (Laptev Sea coast) covering the last 50 14C ka.Testate amoebae (Protozoa: Rhizopoda, Testacea) are one cell microorganisms with a distinct organic shell (testa). They are common in wet environments such as wetlands but they are also frequent in soils, especially in high organic content soils. Their well-defined ecological preferences for habitats and good preservation of fossil shells provide a basis for the rhizopod analysis as a method for reconstruction of environmental changes and climate in the past. The analysis show that differences of Pleistocene and the Holocene climatic conditions are well reflected in the testate amoebae records. The main characteristic of Mamontovy Klyk fossil rhizopod complexes is the dominance of eurybiotic soil genera (e.g. Centropyxis, Cyclopyxis, Plagiopyxis and Phryganella). Fluctuations in species abundances and diversity well reflect alternating of warm-wet and cold-dry periods during the Late Pleistocene, in particular the Karginsky interstadial ca 50-30 14C ka BP and Sartan stadial 30-10 ka 14C BP. It is obvious that climate changes were more drastic during the Pleistocene. These changes were at least partly responsible for the disappearance of some rare rhizopod species (e.g. Argynnia sp., Paraquadrulla irregularis). Considering the species diversity as a result of ecological and climatic conditions, we assume that habitat and climatic conditions during the periods with higher species diversity (e.g. Karginsky interstadial), were more favourable than during the Sartan stadial.

Adsorption of phthalate esters on soil at near saturation conditions

Batch studies were performed to determine the adsorption behavior of dimethyl phthalate ester and diethyl phthalate ester on two sandy New Jersey soils at near saturation conditions. One soil had a very low organic matter content (<0.012%) while the other was quite higher (1.33%). Both esters displayed BET type adsorption to the high organic content soil, while little adsorption was displayed to the low organic matter soil. Linear, Langmuir, Freundlich, BET, and a composite isotherm proposed by Marinas and Li were fitted to the data. The composite isotherm fir best in all cases. The diethyl phthalate evidence a greater tendency to adsorb than the dimethyl phthalate.

The fate and persistence of polychlorinated biphenyls in soil.

The fate and persistence of PCBs 28, 52, 101, 138, and 180 artificially introduced into three soils was studied under a variety of field conditions for up to 415 d following initial contamination. A relationship was detected between ln Koa (octanol/air partition coefficient) and the experimentally observed first-order loss rate constant that was statistically significant at at least the 90% level in all but one instance. In nearly all experiments, PCB persistence was greater in soils of higher organic carbon content. Soil temperature and moisture content were also indicated as important influences on persistence. Significantly longer half-lives were observed in a soil in which initial PCB contamination had occurred ca. 1 year previously. A mass balance showed the most likely mechanism of loss to be volatilisation. Losses attributable to aerobic biodegradation could not be ruled out, but those due to leaching, uptake by biota, and soil erosion were demonstrated to be negligible. First-order rate constants (Kv) were determined for volatilisation of the same congeners from soil under a variety of controlled laboratory scenarios. Multiple linear regression analysis (MLRA) showed the most important influences on kv to be ln Koa (adjusted for soil temperature) and soil organic carbon content. Limited evidence was observed for a relationship between kv and soil moisture content, but not water flux. When tested against field measurements, the MLRA-derived relationship between kv and independent variables predicted to within a factor of 2.5, the persistence of PCBs 28, 52, and 101, However, it did not account for the influence of the age of contaminant association with the soil, soil moisture content or water flux, and failed to function for soils of high organic content, or where ln Koa exceeds ca. 23.

Effects of belowground grazing by collembola on growth, mycorrhizal infection, and P uptake of Geranium robertianum

We hypothesized that the grazing of vesicular-arbuscular mycorrhizal (VAM) hyphae by soil animals could be responsible for the lack of a direct relationship between mycorrhizal infection intensity and nutrient uptake under field conditions. To test this hypothesis, we determined the effect of a range of densities of the collembola, Folsomia candida, on growth, VAM infection, and P uptake in Geranium robertianum, a common forest herb, under greenhouse conditions. Total and aboveground growth were greater at low collembola density than either at higher collembola density or without collembola. These differences were greater when the plants were grown in a high organic content soil mix than when grown in sand. Root mass was not affected by collembola density. In the soil mix, root length decreased with increasing collembola density, but not in the sand. The percent of root length infected with VAM was lower at any collembola density than when collembola were absent. Total infected root length decreased linearly with increasing collembola density. Few significant differences in P uptake or tissue concentration were found. Thus, plant growth (but not P uptake) may be stimulated at low collembola density and inhibited at high. We discuss mechanisms which may be responsible for this non-linear response, and the implications of the pattern of response to studies of plant competition, nutrient turnover, and revegetation.

Anomalies in microbial biomass measurements in acid organic soils using extractable carbon following chloroform fumigation

Two experiments showed that the chloroform fumigation-extraction (CFE) method is unreliable in wet soils of high organic content. The first experiment which applied the CFE method to a defined 14C-labelled biomass showed that the 0.5 M K 2SO 4-extractable C flush was not originated by lysed biomass. In the second experiment, direct observation of protozoan cells showed their preservation after chloroform fumigation. It is suggested that the high water content of the soil protected the cells against lysis because of the low solubility of chloroform.

Pentachlorophenol: health and environmental effects profile.

Pentachlorophenol is used as an industrial wood preservative for utility poles, crossarms, fence posts, and other purposes (79%);for NaPCP (12%); and miscellaneous, including mill uses, consumer wood preserving formulations and herbicide intermediate (9%) (CMR, 1980). As a wood preservative, pentachlorophenol acts as both a fungicide and insecticide (Freiter, 1978). The miscellaneous mill uses primarily involve the application of pentachlorophenol as a slime reducer in paper and pulp milling and may constitute ∼6% of the total annual consumption of pentachlorophenol (Crosby et al., 1981). Sodium pentachlorophenate (NaPCP) is also used as an antifungal and antibacterial agent (Freiter, 1978). Pentachlorophenol also is used as a general herbicide (Martin and Worthing, 1977).Photolysis and microbial degradation are the important chemical removal mechanisms for pentachlorophenol in water. In surface waters, pentachlorophenol photolyzes rapidly (ECETOC, 1984; Wong and Crosby. 1981; Zepp et al., 1984); however,...

Zea Mays, A New Host for Ligniera Junci (Plasmodiophorales)

Roots of Zea mays plants grown in soils of high organic content in reclaimed fields of the Albemarle-Pamlico peninsula of North Carolina were found to be abundantly infected with Ligniera junci (Pl...

FACTORS AFFECTING THE ACTIVITY OF DI‐ALLATE AND TRI‐ALLATE

Summary. Factors investigated included the susceptibility of Avena fatua L. at various stages of growth, the amount of moisture needed to activate di‐allate in Regina heavy clay, the vapour action of di‐allate in soil, the effect of organic matter on the availability of di‐allate, and the persistence of di‐allate and tri‐allate in Regina heavy clay.A. fatua sown at depths of 5–15 cm was killed by di‐allate or tri‐allate. as were seedlings treated at the 15–2‐leaf stage. Seedlings of spring wheat (Triticum aestivum L.) survived rates of 24 oz/ac if the shoots were 1–3 cm long prior to exposure.When di‐allate at 16 oz/ac was mixed with a 5 cm layer of Regina heavy clay (wilting point 19–6%) slightly less than 15% soil moisture was required to give complete control of A.fatua. Further experiments indicated that a large percentage of A. fatua seedlings were killed by the action of di‐allate vapour in the soil.In other tests the activity of di‐allate and tri‐allate was reduced when the percentage of organic matter in the soil was increased by adding peat. This could explain why there is little damage to wheat sown in treated soil of high organic content while similar rates can cause extensive damage in soils of low organic content.Under comparable conditions tri‐allate persisted for a longer period in the soil than di‐allate. Both chemicals exhibited a lag period after which their breakdown appeared to follow a first‐order reaction. Differences in the period of persistence were attributed to a much longer lag period and a slightly slower rate of biological breakdown for tri‐allate as compared to di‐allate.Facteurs affectant l'activité du di‐allate et du tri‐allate

Factors Influencing the Population Fluctuation of Pratylenchus penetrans in Soils of High Organic Content. I. Effect of Soil Fumigants and Different Crop Plants12

Seven selected fields situated near Newland, Indiana, were sampled at monthly intervals during 4 growing seasons to determine the population levels of Pratylenchus penetmns (Cobb) Filipjev and Stekhoven. During the course of the study several of the fields in which sampling sites were situated were treated at various times with I or more of the following nematicidal chemicals: D-D®(1,3-dichloropropene and 1,2-dichloropropane mixture) , Telone® (dichloropropenes mixture), or Vorlex® (mixture of dichloropropenes, dichloropropanes and related chlorinated C3 hydrocarbons plus methyl isothiocyanate). During the first and second growing seasons following fumigation, the P. penetrans population tended to remain low irrespective of crop grown. In the absence of this “fumigation effect” the nematode developed high populations on all crops grown in the rotations, which included onion, corn, potato, spearmint, and peppermint. In a greenhouse test potato, peppermint, onion, and corn were grown in soil naturally infested with P. penetrans at 2 different levels of infestation. In this test the smallest buildup of the nematode occurred on onion.

FURTHER STUDIES OF TOBACCO ANTHRACNOSE IN SOUTHERN RHODESIA*

Results of laboratory tests in Southern Rhodesia indicate that Colletotrichum tabacum, Böning, the causal organism of tobacco anthracnose, could survive in dry soil for 13–17 weeks and therefore might survive from one season to the next in dry soil in the absence of tobacco‐plant residue. The most favourable conditions for survival arose when soils of high organic content dried out fairly soon after being infected; soils which remained moist were the least favourable.Chemical control of soil infection with methyl bromide gas at 1 lb./100 sq.ft. was effective and not phytotoxic. Of the wettable powders used as soil disinfectants, thiram was more effective than zineb or maneb, but all were phytotoxic at certain concentrations. Phytotoxicity to tobacco, which took the form of stunting and poor root growth, varied with different commercial preparations of thiram and zineb.