High Amounts Of Organic Matter Research Articles

New biomimetic approach to determine the bioavailability of triclosan in soils and its validation with the wheat plant uptake bioassay

A new biomimetic approach for triclosan (TCS) was developed based on the leaching of the analyte from different biosolid-amended agricultural soils and the subsequent extraction of the leachates, using a rotating disk sorptive extraction (RDSE) procedure. The leaching equilibrium for TCS was reached at 3h when the ISO method (ISO/TS 21268-1:2007) was followed.The concentrations determined by this biomimetic method were compared with the bioavailability of TCS, determined by its accumulation in the roots of wheat plants grown in the same soil–biosolid systems.It was observed that the amount of organic matter in the soil matrix was a determining factor for mobilization of TCS. An increasing biosolid rate applied to soils resulted in a reduced mobility of TCS because the high amount of organic matter provided by the biosolid increased the hydrophobic interaction between TCS and the matrix. Similarly, increasing biosolid concentrations in the soil significantly decreased the bioavailability of TCS to the wheat plant. Thus, the bioavailability factor in wheat roots decreased from 0.22 to 0.08 for a soil having a pH of 8.2, when the biosolid rate was increased from 30 to 200Mgha−1, respectively.A significant correlation (R=0.98) was obtained between TCS concentration in wheat plants and the proposed biomimetic methodology, indicating that the latter can predict the bioavailability in a time period as short as 180min.The results of this study confirm our previous findings that amending soils with biosolids is beneficial for immobilizing low polarity contaminants and helps prevent their percolation through the soil profile and into groundwater.

Fenton and photo-Fenton process to the wastewater treatment of coffee fruits.

Brazil is the largest coffee producer in the world. After the coffee harvest, the coffee cherry goes through some processes with the objective to improve the quality of the coffee. Among these processes the coffee cherries washing and pulping processes generates large amount of wastewater which contains high amount of organic matter. The present study evaluated the efficiency of Fenton and photo-Fenton processes to reduce chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC) and color from the coffee pulping wastewater. Wastewater samples from conventional and organic cultures, collected in 2010, were used in these studies. A preliminary characterization of the effluent showed high content of organic matter and acidic pH. The Fenton process showed to be efficient to the removal of organic matter, resulting in a reduction of 92% of COD, 95% of BOD and 69% of TOC. Use of the photo Fenton system resulted in a reduction of 98% of COD, 100% of BOD and 94% of TOC. The reduction of the wastewater color was also observed in both processes.

Effect of four soil and water conservation practices on soil physical processes in a non-terraced oil palm plantation

Mulching materials from oil palm residues such as pruned palm fronds (OPF), empty fruit bunches (EFB), and Eco-mat (ECO; a compressed EFB mat) are often the recommended soil and water conservation practices (CP) for oil palm plantations on hill slopes. Another recommended CP is the construction of silt pits or trenches (SIL) across the hill slope to capture runoff and then return the water and nutrients into the surrounding soil. Although these four CP are recommended practices, their relative effects on improving soil physical properties and on increasing the soil water content have never been compared with one another. Consequently, the objective of this study was to fill in this knowledge gap. A three-year field experiment was conducted in a non-terraced oil palm plantation, and soil samples from 0 to 0.15, 0.15 to 0.30, and 0.30 to 0.45m depths were collected every three months and analyzed for their soil physical properties. Soil water content up to 0.75m depth was also measured daily. EFB released the highest amount of organic matter and nutrients into the soil compared to OPF, ECO, and SIL. Hence, EFB was most effective to increase soil aggregation, aggregate stability, soil water retention at field capacity, available soil water content, and the relative proportion of soil mesopores. Due to these improved soil physical properties, EFB also gave the highest soil water content. Unlike ECO that concentrated more water in the upper soil layers, EFB distributed the soil water more uniformly throughout the whole soil profile, but SIL concentrated more soil water in the lower soil layers (>0.30m) because the water levels in the pits were often below 0.30m from the soil surface. The large opening area of the silt pits could have also caused large evaporative water losses from the pits. EFB mulching is recommended as the best CP, particularly for oil palm plantations on hill slopes.

Taxonomic and functional biodiversity variations of meiobenthic and nematode assemblages across an extreme environment: a study case in a Blue Hole cave

In this paper we have explored for the first time the biodiversity pattern of the meiobenthic assemblage in a Blue Hole of the Maldivian Archipelago. The cave is characterised by a marked change of the chemical water parameters below 50 m of depth, with a relevant increase in hydrogen sulfide, carbon dioxide, and sulfates (H2S, CO2 and SO42–). Thus, three stations were selected above and two below the chemo-thermocline in order to test the possible effects of the chemical variations on the meiobenthos. The difficulty of adaptation to these environmental conditions is clearly suggested by the presence of only a few dominant meiobenthic taxa in the bottom of the cave. However, meiobenthic organisms seemed more resistant than macrobenthos, which disappeared completely below this depth. The nematode assemblage was mainly represented by Xyalidae, Desmodoridae, Comesomatidae and Linhomoeidae. A high level of confinement of nematode genera at the different depths has been documented. In the upper part, their structure and biodiversity were comparable to those of the Maldivian subtidal habitats characterised by fine coralline sediments, while a notable dominance was detected in the bottom. The Blue Hole features also influenced the functional traits of the nematode assemblage with a documented increasing number of general opportunists and decrease of Maturity Index. The dominance of non-selective deposit feeders supports the hypothesis of a high amount of organic matter accumulated on the sea bottom of the cave.

Characterization of the Upper Ordovician and Lower Silurian Marine Shale in Northwestern Guizhou Province of the Upper Yangtze Block, South China: Implication for Shale Gas Potential

A detailed study of the upper Ordovician Wufeng shale and lower Silurian Longmaxi shale in northwestern Guizhou province of the upper Yangtze block was conducted on the basis of systematic analyses of a series of experimental measurements on core samples. Trace element ratios V/Cr, U/Th, and V/(V + Ni) reveal that variable paleoredox conditions existed during the deposition of the shale and the degree of anoxia decreased upward. The shale has high thermal maturity with an average Ro value of 3.38% (ranging from 2.94 to 3.65%) and high amounts of organic matter with an average total organic carbon (TOC) content of 2.02% (ranging from 0.36 to 6.73%), the type of which is sapropelic (I) to humic–sapropelic (II1). This indicates that the shale is good gas-producing shale in terms of geochemistry. The mineralogy of the shale is composed of 44.7% quartz and 32.6% clay minerals on average. The shale is characterized by low porosity ranging from 0.6 to 4.4% (averaging 1.8%) and low permeability varying from 0.0066 × 10–3 to 0.1098 × 10–3 μm2 (averaging 0.0378 × 10–3 μm2). The correlations of porosity with the TOC content, quartz content, and clay mineral content demonstrate that the shale interval rich in quartz and organic matter has higher porosity than the clay-rich interval. The gas adsorption capacity increases with the increasing of the TOC content, indicating that organic matter is responsible for adsorbing gas in this shale. Comprehensive analyses through experimental data show that the studied Wufeng–Longmaxi shale succession, especially the lower section, holds the potential for shale gas exploration and development because of TOC enrichment, high thermal maturity, good fracability, and potentially large gas content.

Efficient treatment of domestic wastewater by electrochemical oxidation process using bored doped diamond anode

Domestic wastewaters (DWW) contain varied and high amounts of organic matter which are difficult to oxidize biologically or chemically. The discharge of such effluents is undesirable and can cause excessive oxygen demand in the receiving water. In order to produce an effluent suitable for stream discharge, electrochemical techniques have been explored at the laboratory pilot scale for organic compound removal from DWW. Electrolysis of DWW was carried out using rectangular electrolytic cell containing two circular electrodes (anode and cathode). A preliminary voltametric study was carried out using different anode materials (Ti/BDD, Ti/IrO2 and Ti/IrO2–RuO2). The Ti/BDD electrode was found to be the most effective electrode for DWW treatment. Electrochemical oxidation process using Ti/BDD electrode at the anode and a-C at the cathode with a current density imposed of 26.53mA/cm2 ensures the removal efficiencies of 78.2%, 70% and 89.5% of COD, TOC and color, respectively. DWW could be oxidized by both direct anodic electrochemical oxidation (by means of OH) and indirect electrochemical oxidation via mediators, such as hydrogen peroxide generated by cathodic reduction. Both actions (direct and indirect effects) lead to the formation of powerful oxidizing agents capable of oxidizing refractory organic compounds.

Prediction of long‐term sustainability of constructed urban soil: impact of high amounts of organic matter on soil physical properties and water transfer

AbstractSustainability of urban soils lies in their ability to facilitate water and air permeabilities. Exogenous organic matter has been shown to have a positive impact on these properties. Under urban conditions, a large one‐time input of an organic amendment was made to the reconstituted soil. Two organic materials, green‐waste compost (gw) or cocompost from sewage sludge and wood chips (sw), were mixed with sandy loam soil (40% v/v) and placed in 600‐L containers. Containers received a 29‐cm thick layer of sandy loam soil–organic matter mix over a 28‐cm thick layer without organic amendment. Volumetric water content, dry bulk density, hydraulic conductivity at saturation and water retention were measured over 5 yrs in the soils and values for the mixes and a control compared. After this time, dry bulk density was greater (1.54 g/cm3) in control than in gw or sw soils (1.31 and 1.11 g/cm3, respectively), whereas hydraulic conductivity at saturation was smaller (4 × 10−7 m/s) than in gw (3.4 × 10−6) or sw (3.7 × 10−6 m/s). HYDRUS 1D water balance model indicated that below 27 cm depth in the control after 5 yrs, there was a high degree of anoxia, lasting >200 days per year, compared with <40 days in gw and sw. Amplification of the risk of anoxia below 27 cm depth after 10 yrs was 323, 151 and 100 days in the control, gw and sw, respectively. Organic matter amendment could support sustainable urban soils for ten years after soil reconstitution.

Biocoenosis response to hydrological variability in Southern Africa during the last 84 ka BP: A study of lipid biomarkers and compound-specific stable carbon and hydrogen isotopes from the hypersaline Lake Tswaing

Sea surface temperature (SST) changes in the SW Indian and SE South Atlantic Ocean are proposed to have controlled environmental changes at the southern tip of the African continent during the past. For a better understanding of the hydrological variations and their environmental impact during the past 84kabeforepresent (BP), we analyzed lipid biomarkers and their stable carbon (δ13C) and hydrogen (δD) isotopic compositions in sediments from Lake Tswaing (25°24′30″ S, 28°04′59″ E). δD values of long-chain n-alkanes from higher plants varied between −155 and −82‰ and matched well with SST gradient changes between the tropical and subtropical SW Indian Ocean. Increased SSTs correlate with deuterium-depleted δD values of n-alkanes and indicate a higher convection transporting more moisture across South Africa in the time from 84 to 80kaBP, during the marine isotope stage (MIS) 4 and from 50 to 39kaBP. During these humid periods high amounts of organic matter (up to 9.8% total organic carbon (TOC)) were deposited in Lake Tswaing. Periods with deuterium-enriched δD values of n-alkanes (76kaBP, 73 to 69kaBP, 55 to 51kaBP, and 31.4 to 12.6kaBP), indicating dry climate and increased lake water salinity, were associated with lower TOC contents and a higher degradation state of the terrestrial organic matter. We occasionally detected algae-derived C37- and C38-alkenones in the core, particularly in times when lake salinity and alkalinity were elevated. The disappearance of alkenones around 25kaBP was accompanied by highly depleted δD values of n-alkanes from aquatic organisms (−180‰ for n-C23) indicating a substantial freshening of the lake water. The vegetation surrounding Lake Tswaing during the last 84kaBP consisted mainly of savanna-type plants, such as trees and shrubs with varying contributions from C4 grasses. The latter predominated particularly at the end of MIS 5 and during arid climatic conditions in MIS 3. We show that the changing vegetation controls the n-alcohol to n-alkane ratio of the leaf waxes; this is reflected by the higher plant alkane (HPA) index which has potential as a new climate-controlled vegetation proxy; in semi-arid periods HPA index values were elevated reflecting savanna vegetation which is adapted to drier climate, whereas HPA index values were lower during more humid conditions.

Soil quality assessment through a multi-approach analysis in soils of abandoned terraced land in NE Spain

The abandonment of agricultural land in mountainous areas has been an outstanding problem along the last century and has captured the attention of scientists, technicians and administrations, for the dramatic consequences sometimes occurred due to soil instability, steep slopes, rainfall regimes and wildfires. Hidromorfological and pedological alterations causing exceptional floods and accelerated erosion processes has therefore been studied, identifying the cause in the loss of landscape heterogeneity. Through the disappearance of agricultural works and drainage maintenance, slope stability has resulted severely affected. The mechanization of agriculture has caused the displacement of vines, olives and corks trees cultivation in terraced areas along the Mediterranean catchment towards more economically suitable areas. On the one hand, land use and management changes have implicated sociological changes as well, transforming areas inhabited by agricultural communities into deserted areas where the colonization of disorganized spontaneous vegetation has buried a valuable rural patrimony. On the other hand, lacking of planning and management of the abandoned areas has produced badlands and infertile soils due to wildfire and high erosion rates strongly degrading the whole ecosystems. In other cases, after land abandonment a process of soil regeneration has been recorded. Investigations have been conducted in a part of NE Spain where extended areas of terraced soils previously cultivated have been abandoned in the last century. The selected environments were semi-abandoned vineyards, semi-abandoned olive groves, abandoned stands of cork trees, abandoned stands of pine trees, scrubland of Cistaceaea, scrubland of Ericaceaea, and pasture. The research work was focused on the study of most relevant physical, chemical and biological soil properties, as well as runoff and erosion under soils with different plant cover to establish the abandonment effect on soil quality, due to the peculiarity and vulnerability of these soils with a much reduced depth. The period of observation was carried out from autumn 2009 to autumn 2010. The sediment concentration of soil erosion under vines was recorded as 34.52 g/l while under pasture it was 4.66 g/l. In addition, the soil under vines showed the least amount of organic matter, which was 12 times lower than all other soil environments. The carbon dioxide (CO2) and total glomalin (TG) ratio to soil organic carbon (SOC) in this soil was 0.11 and 0.31 respectively. However, the soil under pasture contained a higher amount of organic matter and showed that the CO2 and TG ratio to SOC was 0.02 and 0.11 respectively indicating that the soil under pasture better preserves the soil carbon pool. A similar trend was found in the intermediate soils in the sequence of land use change and abandonment. Soil structural stability increased in the two soil fractions investigated (0.25-2.00 mm, 2.0-5.6 mm) especially in those soils that did not undergo periodical perturbations like wildfires. Soil quality indexes were obtained by using relevant physical and chemical soil parameters. Factor analysis carried out to study the relationship between all soil parameters allowed to related variables and environments and identify those areas that better contribute to soil quality towards others that may need more attention to avoid further degradation processes.

Evaluation of Lower Cambrian Shale in Northern Guizhou Province, South China: Implications for Shale Gas Potential

The Lower Cambrian shale is an important source rock for conventional oil and gas in northern Guizhou province (NGP), south China, but has recently been considered as a potential shale gas reservoir. In this study, characterization of this target shale was determined through a systematic series of measurements on core samples. According to total organic carbon (TOC) and Rock-Eval data, the Lower Cambrian shale is overmature but still contains high amounts of organic matter, which is composed mainly of alginite. The TOC content is enriched up to 10.4% at the base of the shale. There are two different correlation patterns between trace elements and TOC in the Lower Cambrian shale. A good correlation present in the upper part indicates a non-sulfidic anoxic sedimentary environment. However, higher enrichments of U, V, and Mo in the basal part exhibit sulfidic euxinic conditions. Brittle minerals are quite abundant and have a critical effect on artificial fracture. Gas sorption volume increases with an increasing TOC, pore volume, and surface area, indicating that pores at the microscale associated with the organic matter fraction are an important control on storage capacity. The contribution of clay minerals to the sorbed gas may be irrelevant because of the presence of moisture. Analysis of data indicates that the basal part of the Lower Cambrian shale demonstrates the greatest potential for gas content and can be explored for production.

Permeability Reduction by Sediment Retention in Saturated Sand Columns

Recently, researchers in coastal engineering have paid more attention to the role of sediment (particulate organic matter adsorbed on fine solid particles, diameter range 1–\(100~\upmu \)m) in considering the biodiversity of estuaries. In this study, permeability reduction of saturated sand columns by sediment retention is investigated through laboratory experiments. Water-based sediment was injected through vertical sand columns under a constant water head difference, with different flow rates, porosities of the sand columns, and the chemical properties of sediment. It was found that the permeability reduction was uniquely correlated with flow rate and sediment properties; that is, increasing flow rate or using sediment containing high amounts of organic matter causes a significant reduction in permeability. Furthermore, an approximate experimental equation is proposed to predict the retention mass of sediment. This equation can predict the retention mass with a relative error of less than 5 %. In addition, a new model is proposed to determine the permeability reduction by sediment retention. This model could predict the permeability reduction with a relative error of 10 %.

Effect of methods of preparation on distribution of heavy metals in different size fractions of municipal solid waste composts

The present study compares the distribution and nature of heavy metals in composts from 12 cities of India, prepared from different types of processed urban solid wastes, namely mixed wastes (MWC), partially segregated wastes (PSWC), and segregated bio-wastes (BWC). Compost samples were physically fractionated by wet sieving, followed by extraction of heavy metals by dilute HCl and NaOH. Bigger particles (>0.5 mm) constituted the major fraction in all three types of composts and had a relatively lower concentration of organic matter and heavy metals, the effect being more pronounced in MWC and PSWC in which a significant portion of the heavy metals was distributed in finer size fractions. Cd, Ni, Pb, and Zn were extracted to a greater extent by acid than by alkali, the difference being greater in MWC, which contained a higher amount of mineral matter. In contrast, Cu and Cr were extracted to a greater extent by dilute alkali, particularly from BWC containing a higher amount of organic matter. Water-soluble heavy metals were generally related to the water-soluble C or total C content as well as to pH, rather than to their total contents. This study concludes that wet sieving with dilute acid can effectively reduce heavy metal load in MWC and PSWC.

Interactive effects of depth and temperature on CH4 and N2O flux in a shallow podzol

Measuring and modelling the efflux of greenhouse gases from soils is crucial for gauging ecosystem responses to climate and land-use change, and potential contributions and feedbacks to gas emissions. Upland soils with high amounts of organic matter can produce large effluxes of CH4 and potentially N2O, and therefore understanding the sensitivity of such fluxes to changes in climate (e.g. temperature) is of importance. Here we consider the role of shallow podzols in the temperature response of CH4 and N2O efflux using a simple laboratory incubation. Such soils have a shallow peat layer overlain by coarse organic matter, and by splitting and incubating these layers across a 1–30 °C temperature ramp, we observed a significant negative temperature response for both gases, and a gas-dependent effect on the presence of a between-layer difference. Given these observations, there is a need to consider the temperature sensitivity of near surface layers as distinct, and to recognise the potential for shallow podzols to have a strong source–sink transition across temperature ranges.

EFFECT OF SOME ORGANIC SOURCES IN WHEAT YIELD AND SOIL SANDY FERTILITY

Two field experiments were conducted at Abdel Menem Riyadh village, Al-Bostan, Beheira Governorate in two successive winter seasons of 2008/2009 and 2009/2010 to assess the effects of some organic sources viz. chicken manure (CM), farmyard manure (FYM) and organic wastes (OW) in combination with different levels of inorganic N fertilizer 60, 90 and120 kg N/fed on wheat yield and its components under sprinkler irrigation system prevailing in the region and to evaluate to what extent the fertilizer treatments impact on soil fertility status of the experimental field. The results showed that application of organic nitrogen sources in combination with inorganic nitrogen recorded significant effect on wheat grains and straw yields and weight of one-1000 grain. The significant effect of the organic nitrogen sources was in the following order: CM > FYM > OW with the exception of the significant effect of OW and FYM, which were similar on their effect on wheat straw yield. Applying CM (at rate of 50 kg organic-N/fed. =2ton CM/fed) combination with 90 kg N/fed significantly yielded the most significantly favorable N, P and K uptake in wheat grains and straw. When CM was applied at rate (50 kg organic nitrogen/fed.) in combination with 90 kg N/fed, the experimental soil gained after harvest the highest amounts of N, P and K as well as the highest amount of organic matter that will support the subsequent crop.

Effects of organic matter on carbonate stable isotope ratios (δ13C, δ18O values) – implications for analyses of bulk sediments

Stable isotope ratio (δ(13)C, δ(18)O values) analyses of carbonates can be biased by CO(2) release from organic impurities. This is most critical for carbonate isotope analyses from bulk sediments containing comparably high amounts of organic matter (OM). Several methods have been developed to remove OM prior to analyses, but none of them can be universally applied. Moreover, pretreatment methods cause isotopic bias in themselves and should probably best be avoided. Thus, it is essential to have indicators for reliable isotope values of untreated carbonate-OM mixtures. Artificial mixtures of organic compounds with a standard carbonate were analyzed to investigate the bias on carbonate isotope ratios caused by OM in the sample. The total-inorganic-carbon to total-organic-carbon ratio (TIC/TOC) was used as a measure for the " organic impurity" of the sample. The target was to evaluate TIC/TOC as a measure for sample quality and to define TIC/TOC thresholds for reliable isotope measurements of mixtures between calcium carbonate and organic compounds. The effect of organic impurities on carbonate stable isotope values depended on the specific OM compound and the respective TIC/TOC ratio. Different CO(2) release rates were determined for the pure OM compounds. A sample TIC/TOC ratio ≥0.3 was found to be a threshold for reliable measurements of the isotope composition of calcium carbonate. Bulk carbonate analyses from carbonate-OM mixtures are reliable only if the TIC/TOC values do not fall below certain thresholds. This has implications for carbonate isotope studies from bulk sediments for which the TIC/TOC ratios should be considered as an easy-to-determine measure for sample-quality assessment.

Live (stained) benthic foraminifera from the Cap-Ferret Canyon (Bay of Biscay, NE Atlantic): A comparison between the canyon axis and the surrounding areas

Living (Rose Bengal stained) benthic foraminiferal faunas were investigated at 13 deep-sea stations sampled in the Cap-Ferret Canyon area (NE Atlantic). One station (151m) is located on the continental shelf close to the canyon head. All other stations are located along 2 bathymetric transects: 7 sites along the canyon axis with depths ranging from 300 to 3000m and 5 stations along the adjacent flank with depths ranging from 300m to 2000m. Sedimentological analyses indicate that the Cap-Ferret Canyon is at present inactive in terms of sediment gravity flow. Compared to stations on the adjacent flank, canyon-axis stations are generally characterised by shallow oxygen penetration depths, high diffusive oxygen uptakes (DOU) and high lipid contents. Higher mineralisation rates recorded in the canyon axis are likely due to a preferential focusing of labile organic matter in the canyon axis. Foraminiferal standing stocks do not exhibit any straightforward correlation with the different descriptors of organic matter available in the sediment. However, foraminiferal standing stock and diversity along the canyon axis are generally higher than on the adjacent flank. Canyon axis sites yield dominant species that are similar to those at adjacent flank and open slope stations located at comparable water depths. However, intermediate and deep infaunal species were only recorded in the lower canyon axis, where high amounts of organic matter were observed in deeper sediment layers. Finally, the faunal composition in the Cap-Ferret Canyon is different compared to the nearby Cap-Breton Canyon, where sediment gravity flows are active. The absence of pioneer species and the occurrence of highly specialized taxa are both consistent with the much more stable conditions in terms of hydro-sedimentary conditions prevailing in the Cap-Ferret Canyon.

Comparison of the soil carbon and nitrogen contents of Quercus cerris and Fraxinus excelsior in the Mersin-Gulnar region

Background: Soil samples were taken from a depth of 0-10 cm under the Quercus cerris and Fraxinus excelsior at an altitude of 1300-1500 m from the Kullin site at Gulnar-Mersin and were compared for their pH, CaCOs, nitrogen (N) %, and carbon (C) % contents. Balanced soils in natural forest ecosystems are known to be very rich in carbon content which increases with latitude and altitude and that the C/N ratio varies greatly between the soils of different plant species. We determined the values of the C/N rates in Q. cerris and F. excelsior soils of the Gulnar Gezende forest for the first time at this altitude. Material and Methods: A pH meter and Scheibler calcimeter were used to determine the soil pH and lime contents respectively. Percentage C was determined using the Anne method and the N% with the Kjeldahl method. Results: There was no difference in the pH values and nitrogen percentage contents between the two soils. Q. cerris soil was found to have medium levels of CaCOs, while the level of CaCCh in F. excelsior soils was low. The C/N rates and carbon contents were higher in Q. cerris soil than F. excelsior soil (P Conclusions: The higher carbon content of Q. cerris soil can be explained by higher amounts of organic matter compared with F. excelsior, which might depend on factors such as microclimate and their specific characteristics.

Community Structure of Soil Nematodes Associated with Solanum Tuberosum

The soil nematode food web structure under a potato crop compared to a forest control treatment was investigated for 10 months. All nematode functional guilds were recovered from both treatments. Higher populations of enrichment nematodes (bacterivores and fungivores) were recovered in the potato plots and this is attributed to possible higher amounts of organic matter in the crop plots as compared to the forest control. For the pest suppression species, higher populations of carnivorous nematodes were recorded in the forest samples, while higher populations of the omnivorous nematodes were recorded in the potato plots. It will therefore seem that while the environmental response of predatory (carnivorous) nematodes is linked to physical perturbation, food sources are a more important factor in the environmental response of the omnivorous nematodes. Whereas the plant-feeding species of the Pl3 class were significantly higher in the crop plots, the Pl5 plant species were significantly higher in the forest control samples. These differences are attributed to host specificity. Overall, the plant-feeding nematodes dominated (9 families, 14 genera, 35.73 % total biomass contribution), followed by the enrichment nematodes (8 families, 12 genera, 33.53% total biomass), and then the pest suppression species (9 families, 19 genera, 30.76% total biomass). Based on these results plant-parasitic nematodes of the Pl3 cp class particularly Helicotylenchus mucronatus, Rotylenchus buxophilus, and Meloidogyne microcephala, are considered a potential threat to potato production in the study area.

Organic geochemical characteristics and oil generating potential of the Upper Jurassic Safer shale sediments in the Marib-Shabowah Basin, western Yemen

The organic rich Safer shales exposed in the north-central part of onshore Marib-Shabowah Basin are evaluated and their depositional environments are interpreted. Total organic carbon contents (TOC) of the shales range from 1.02–16.8wt%, and yield hydrogen index (HI) values ranging from 130 to 820mgHC/g TOC, consistent with mainly Type II with minor contributions from Type I and mixed Types II–III kerogens. The Safer shale samples have vitrinite reflectance values in the range of 0.5–1.0 Ro%, indicating early mature to peak mature stage for oil generation. Tmax values range from 429–438°C, which are in reasonably good agreement with vitrinite reflectance data. Kerogen microscopy shows that the Safer shales are characterized by high amounts of organic matter, consisting predominantly of yellow fluorescing amorphous organic matter and alginite of marine origin. This is supported by their high content of hydrogen rich Type II and I oil-prone kerogen.The biomarker distributions of the Upper Jurassic Safer extracts are characterized by dominant low to medium molecular weight compounds (n-C14 to n-C20), low Pr/Ph ratio (<1.0), high phytane/n-C18 ratios (0.82–2.68), and predominant regular sterane C27. All biomarker parameters clearly indicate that the organic matter was derived from marine algal inputs and deposited under anoxic (reducing) conditions. Hypersaline conditions also prevailed during deposition of these sediments, as indicated by the presence of gammacerane.

The response of chironomid assemblages to mineral richness gradient in the Western Carpathian helocrenes

Chironomid assemblages of helocrene springs were investigated in the Western Carpathians in order to identify potential effect of water mineral richness on the taxonomic structure of the assemblages. A complex gradient considering water chemistry and substratum was used as a measure of basicity (mineral richness). Taxonomic structure, total abundance and abundance of most frequent taxa were related to this gradient with regards to two contrasting habitats: trickle (A) and water-loged soil with standing water (B). The variance in chironomid assemblage attributable to basicity was estimated and tested via PERMANOVA as well as the possible effect of the other environmental variables. The response of individual taxa was examined using GAM. The results indicate a strong relationship between basicity and substratum characteristics, with coarser mineral substrata at basic and high amount of organic matter at acidic conditions. Although water chemistry was correlated with and inseparable from these substratum properties, it could not be substituted with them, as they discriminated well only between acidic and basic springs, but did not follow the basicity gradient in either acidic or basic group of springs. Chironomid assemblage showed a strong and systematic response to the complex gradient of mineral richness, which explained the largest portion of variance in both the habitat A and B faunal data and was projected on the first axes of both NMDS ordinations. The assemblage response could be documented by the preference of several taxa for particular mineral richness conditions, while the number of taxa seemed to be highest in the middle of the basicity gradient. As only 17 samples were analysed so far, the results are considered preliminary and, hopefully, more confident results will be available in near future.doi: 10.5324/fn.v31i0.1403.Published online: 17 October 2012.