Impacts of Soil Organic Matter and Temperature on Sorption of Acetazolamide on Four Soils

Batch sorptions of acetazolamide (AZ) were conducted using four soils from China. Sorption of AZ was found to be impacted by OC, clay content, and soil pH, with higher k_d values for soils with higher clay content. The k_d values of SOM-removed soils are much lower than those of bulk soils. Sorption data were well fitted with a Freundlich model (r² > 0.99). Chelating with the metal ions on the surfaces of soil particles was probably involved. With pH increase, the electrostatic attraction between anionic AZ and positively charged soil surface may increase. The sorption capacity decreased when the temperature increased from 20 to 40°C, and the calculated thermodynamics parameters of ΔG₀, ΔH₀, and ΔS₀ indicated that the sorption was a non-spontaneous, physisorption, and exothermic process. Sorption coefficients (k_d) for the compound in soil were low (ranging from 0.42 to 1.19 L·kg^?1) and indicated that low level sorption of AZ with appreciable risk of ground water contamination.     

Characteristics of Copper Sorption by Various Agricultural Soils in China and the Effect of Exogenic Dissolved Organic Matter on the Sorption

To explore the effect of exogenic dissolved organic matter (DOM) on Cu(II) sorption in agricultural soils, 26 agricultural soils were collected across China. Exogenic dissolved organic matter, extracting from wheat straw (DOM_W) and swine manure (DOM_S), respectively, were added to the soils to conduct a series of batch sorption and characterization experiments. The solid-liquid partition coefficient (K_d) ranged from 0.02 to 76.46 L g^?1, suggesting different Cu(II) sorption on various soils. PCA analysis indicated that pH, free Fe/Al oxides, carbon, and total Cu content had a significant positive relationship with the Cu(II) sorption, respectively. And the contribution rate of pH was the highest (38.15%). Moreover, DOM markedly inhibited the Cu(II) sorption in alkaline soils while promoted the Cu(II) sorption in acidic soils, which were interacted by the soil properties and DOM characteristics. The effect of DOM_S on Cu(II) sorption were more obvious than DOM_W, which were further confirmed by Fourier transform infrared (FTIR) spectroscopy. FTIR also showed Cu(II) was primarily adsorbed on the specific functional groups, such as CO, OH, and CO, providing direct evidences for the binding of Cu(II) with DOM. This study can guide the rational use of organic fertilizers, and also provide baseline knowledge for the prevention and control of soil pollution.     

Simultaneous Desorption and Desorption Kinetics of Phenanthrene,Anthracene, and Heavy Metals from Kaolinite with Different Organic Matter Content

Soils contaminated simultaneously with polycyclic aromatic hydrocarbons (PAHs) and heavy metals pose major threat to human health and environment by getting released from soil into water environment. The purpose of this study was to evaluate simultaneous desorption and desorption kinetics of PAHs (phenanthrene and anthracene) and heavy metals (lead, nickel, and zinc) from artificially contaminated kaolinite soils with different organic matter content. Batch desorption tests were conducted using single and combined enhancing agents containing Triton X-100 and Tween 80 as non-ionic surfactants, Ethylenediaminetetraacetic acid (EDTA) as a chelating agent, and citric acid as an organic acid. The solution with the highest removal efficiency was the combined solution of Triton X-100 (10% w/w) + EDTA (0.01 M). Removal levels around 92, 46, 92, 95, and 96% were obtained for phenanthrene, anthracene, lead, nickel, and zinc, respectively, by using this combination. Batch desorption kinetics experiments were performed using the mentioned combination. During the first 24 h, desorption kinetics were rapid, followed by a plateau until the end. The data obtained from desorption kinetics experiments were fitted with four kinetics models: pseudo-second-order equation, empirical power function, elovich, and parabolic diffusion. The correlation coefficient of the pseudo-second-order equation was higher than that of other functions. Moreover, batch experiments have showed inverse correlations between removal efficiency and organic matter content of soil.     

Influence of Soil Organic Matter on Copper Extraction from Contaminated Soil

Column experiments of copper extraction from four contaminated soils characterized by a content of Soil Organic Matter (SOM) ranging from 1% to 25% are presented and discussed. The extraction was performed by flushing the soil with an aqueous solution of a sodium salt of ethylene diamminotetraacetic acid (EDTA). Preliminary tests were performed on a soil containing 25% of organic matter, to investigate the influence of pH, concentration and volumes of EDTA on its chelant action and on the dissolution of SOM. Having selected the optimal conditions for the extraction process, a further series of tests was conducted on the four soils to evaluate the influence of organic content on copper extraction yields. EDTA solutions at 0.01 M, 0.05 M, 0.1 and 0.2 M were injected at 0.33 ml/s; copper and organic matter extraction yield were determined. At a pH of 5, 15 pore volume (PV) of a solution containing 0.05M EDTA, extracted about 99% of copper contained by the soil with the higher organic matter content. Under the same conditions, and for soil with > 6% SOM, extraction yields over 80% were achieved, while at lower organic content, copper extraction was dramatically reduced. This was attributed to the formation of highly stable copper-humate complexes and to their increasingly dissolution that occurred in the soils with higher organic matter level.

Experimental tests performed at different contamination levels (1200 mg/kg, 2400 mg/kg) showed that EDTA extraction effectiveness also depended upon initial soil Cu concentration.     

Chemical Characteristics and Origin of Dissolved Organic Matter in the Yukon River

Monthly (or bi-weekly) water samples were collected from the Yukon River, one of the largest rivers in North America, at a station near the US Geological Survey Stevens Village hydrological station, Alaska from May to September 2002, to examine the quantity and quality of dissolved organic matter (DOM) and its seasonal variations. DOM was further size fractionated into high molecular weight (HMW or colloidal, 1 kDa–0.45 μm) and low molecular weight (LMW, <1 kDa) fractions. Dissolved organic carbon (DOC), colored dissolved organic matter (C-DOM) and total dissolved carbohydrate (TCHO) species were measured in the size fractionated DOM samples. Concentrations of DOC were as high as 2830 μmol-C l⁻¹ during the spring breakup in May and decreased significantly to 508–558 μmol-C l⁻¹ during open-water season (June–September). Within the DOC pool, up to 85% was in the colloidal fraction (1 kDa–0.45 μm) in early May. As DOC concentration decreased, this colloidal portion remained high (70–85% of the bulk DOC) throughout the sampling season. Concentrations of TCHO, including monosaccharides (MCHO) and polysaccharides (PCHO), varied from 722 μmol-C l⁻¹ in May to 129 μmol-C l⁻¹ in September, which comprised a fairly constant portion of bulk DOC (24±2%). Within the TCHO pool, the MCHO/TCHO ratio consistently increased from May to September. The C-DOM/DOM ratio and the size fractionated DOM increased from May to September, indicating that DOM draining into the Yukon River contained increased amounts of humified materials, likely related to a greater soil leaching efficiency in summer. The average composition of DOM was 76% pedogenic humic matter and 24% aquagenic CHO. Characteristics of soil-derived humic substances and low chlorophyll-a concentrations support a dominance of terrestrial DOM in Yukon River waters.     

Incorporation of Petroleum Carbon Into Soil Organic Matter During Biodegradation

A procedure, based on measurement of the stable carbon isotope ¹³C, has been developed for determining the extent to which petroleum carbon is incorporated into soil organic matter (SOM) by humification of biomass produced during biodegradation of the petroleum in soil. We have shown that a crude oil having a δ¹³C of-27.4%, when biodegraded in a soil containing SOM with a δ¹³C of-15.7%, resulted in a change of the δ¹³C of the bound SOM reflecting that of petroleum carbon. Comparison of five soil biodegradation tests using different amounts and types of fertilizer to stimulate biodegradation of the oil in this soil showed that the extent of the δ¹³C change in the bound SOM varied with the extent of oil biodegradation observed. To obtain ¹³C data on the SOM, the residual petroleum was first removed by rigorous extraction with dichloromethane using a Soxhlet apparatus. The extracted soil was then combusted to release bound carbon as CO₂, which was analyzed for ¹³C. Where the SOM has a δ¹³C similar to that of petroleum, ¹⁴C measurements of SOM would give similar results. This type of data, referred to as the petroleum “footprint” in the SOM, could be useful in identifying or confirming intrinsic biodegradation of petroleum in contaminated soil.     

Influence of the Interactions Between Black Carbon and Soil Constituents on the Sorption of Pyrene

Biochar (a kind of black carbon (BC)) has been advocated as a promising additive to farmland, thus it is crucial to understand the influence of BC on the fate of hydrophobic organic chemicals (HOCs) when they exist in soil. This study explored the sorption of pyrene onto a BC sample obtained by pyrolyzing pine sawdust, two soils, clay (kaolinite), and the mixtures thereof to investigate the influence of the interactions between BC and soil constituents on the sorption of HOCs and the mechanisms therein. Sorption of pyrene onto soil?BC mixtures was significantly less than that predicted by the sum of the individual soil and BC sorption, indicating that the sorption of pyrene onto soil and BC did not occur independently. The reduction of BC sorption capacity in soil seemed primarily to be caused by soil dissolved organic matter (DOM), which attenuated pyrene sorption onto BC by 18.7%?40.3% (within pyrene equilibrium concentration range of 0.05?0.5 S _w). These were likely due to the blockage of micropores, reduced accessibility of sorption sites, and binding of pyrene by DOM in aqueous solution. In addition to the DOM effect, kaolinite also diminished pyrene sorption onto BC to some extent, which suggested additional interaction between BC and soil particles. Pyrene sorption onto the soil?BC mixtures varied with water content and contact time. The influence of wet versus dry conditions and contact time on the K_oc of pyrene was more obvious when pyrene equilibrium concentrations were lower. The effect of aging also varied with soil properties. In summary, BC could not behave independently in soil, and its sorption capacity was changed by its interactions with soil constituents, which may be influenced by soil properties, environmental condition, and contact time.     

Comparison of Soil Organic Matter in Created, Restored and Paired Natural Wetlands in North Carolina

Soil organic matter (SOM) content is a key indicator of soil quality and is correlated to a number of important soil processes that occur in wetlands such as respiration, denitrification, and phosphorus sorption. To better understand the differences in the SOM content of created (CW), restored (RW), and paired natural wetlands (NWs), 11 CW/RW-NW pairs were sampled in North Carolina. The site pairs spanned a range of hydrogeomorphic (HGM) subclasses common in the Coastal Plain. The following null hypotheses were tested: (1) SOM content of paired CW/RWs and NWs are similar; (2) SOM content of wetlands across different HGM subclasses is similar; and (3) interactions between wetland status (CW/RW vs. NW) and hydrogeomorphic subclass are similar. The first null hypothesis was rejected as CW/RWs had significantly lower mean SOM (11.8 ± 3.9%) than their paired NWs (28.98 ± 8.0%) on average and at 10 out of the 11 individual sites. The second and third null hypotheses were also rejected as CW/RWs and NWs in the non-riverine organic soil flat subclass had significantly higher mean SOM content (31.08 ± 14.2%) than the other three subclasses (8.18 ± 2.5, 11.18 ± 8.2, and 10.38 ± 4.2%). Individual sites within this fourth subclass also had significantly different SOM content. This indicated that it would be inappropriate to include the organic soil flat subclass with either the riverine or non-riverine mineral soil flat subclasses when considering restoration guidelines. These results also suggested that if there is a choice in mitigation options between restoration or creation, wetlands should be restored rather than created, especially those in the non-riverine organic soil flat subclass.     

The Effect of Mineral Particulate Matter on the Productive Characteristics of Bacterioplankton and the Degradation of Labile Organic Material

The effect of mineral particulate matter on the population of bacterioplankton, its aggregation, and productive characteristics was studied in model experiments with different concentrations of particulate kaolin and the same concentration of organic substance (sodium humate). It was found that the presence of mineral particulate matter stimulated the aggregation of bacterioplankton, improved bacterial production, and extended the productive period of bacterioplankton. The integral specific production of aggregated bacterioplankton was higher than that of free-swimming bacterioplankton. The energy metabolic coefficient K ₂ of bacterioplankton in the presence of mineral particulate matter was higher than in its absence.     

Synergistic Effects of Organic Contaminants and Soil Organic Matter on the Soil-Water Partitioning and Effectiveness of a Nonionic Surfactant (Triton X-100)

Napthalene- and decane-contaminated soils were treated with Triton X-100 (a nonionic surfactant) to characterize the soil-water partitioning behavior of the surfactant in soils with different organic content. Soil samples with different organic content were prepared by mixing sand-mulch mixtures at different proportions. The experimental results indicated that the amount of surfactant sorbed onto soil increased with increasing soil organic content and increasing surfactant concentration. The effective critical micelle concentration (CMC) also increased with increasing organic content in soil. The CMC of Triton X-100 in aqueous systems without soil was about 0.3 mM and the effective CMC values measured for soil-water-surfactant systems (approximately 1:19 soil/water ratio) with 25%, 50%, and 75% mulch content were 0.9, 1.0, and 1.7 mM, respectively. Sub-CMC surfactant sorption was modeled accurately with both the Freundlich and the linear isotherm. The maximum surfactant sorption onto soil varied from 66% to 82% of added surfactant in the absence of contaminant. The effective CMC values for Triton X-100 increased to some extent in the presence of contaminants, as did the maximum surfactant sorption. The maximum surfactant sorbed onto the soil with 75% mulch content increased from 82% for clean soils, to 95% and 96% for soils samples contaminated with naphthalene and decane, respectively.     

Influence of Lime and Organic Matter on the Mobility of Cadmium in Cadmium-Contaminated Soil in Relation to Nutrition of Spinach

Cadmium and cadmium compounds are water soluble, mobile in most soils, bio-available, and tend to bio-accumulate. A pot culture experiment was conducted on contaminated soil to study the influence of lime and organic matter on the mobility of cadmium in spinach and its rhizosphere soil. Application of lime (50% and 100% lime requirement) and organic matter (0.5 and 1% by weight of soil) to soil decreased the availability of Cd to the soil and plant throughout the crop growth. The highest diethylene triamine penta-acetic acid (DTPA) extractable Cd was 10.84 mg kg^?1 in the treatment OM₀ L₀ (No application of organic matter and lime) at 20 days after sowing of spinach. Likewise, the highest Cd concentration in spinach roots and shoots were 19.80 and 17.0 mg kg^?1 in the treatment OM₀ L₀ at 20 days after sowing. The Cd concentration in spinach roots and shoots were decreased by 63.23 and 71.88%, respectively, in the treatment OM₁ L₁₀₀ (application of FYM at 1.0% by weight of soil and lime at 100% lime requirement) after 60 days of growth. The lowest concentrations of Cd in the soil and plant after the harvest of the crop were 2.88 and 4.27 mg kg^?1, respectively, in the treatment OM₁ L₁₀₀ and resulted in 65.75 and 71.55% decrease over control (OM₀ L₀). The highest total chlorophyll content of leaves was 2.19 mg kg^?1 of fresh weight in the treatment OM₁ L₁₀₀ at 40 days of crop growth.     

Reversibility of Soil Productivity Decline with Organic Matter of Differing Quality Along a Degradation Gradient

In the highlands of Western Kenya, we investigated the reversibility of soil productivity decline with increasing length of continuous maize cultivation over 100 years (corresponding to decreasing soil organic carbon (SOC) and nutrient contents) using organic matter additions of differing quality and stability as a function of soil texture and inorganic nitrogen (N) additions. The ability of additions of labile organic matter (green and animal manure) to improve productivity primarily by enhanced nutrient availability was contrasted with the ability of stable organic matter (biochar and sawdust) to improve productivity by enhancing SOC. Maize productivity declined by 66% during the first 35 years of continuous cropping after forest clearing. Productivity remained at a low level of 3.0 t grain ha^-1 across the chronosequence stretching up to 105 years of continuous cultivation despite full N–phosphorus (P)–potassium (K) fertilization (120–100–100 kg ha⁻¹). Application of organic resources reversed the productivity decline by increasing yields by 57–167%, whereby responses to nutrient-rich green manure were 110% greater than those from nutrient-poor sawdust. Productivity at the most degraded sites (80–105 years since forest clearing) increased in response to green manure to a greater extent than the yields at the least degraded sites (5 years since forest clearing), both with full N–P–K fertilization. Biochar additions at the most degraded sites doubled maize yield (equaling responses to green manure additions in some instances) that were not fully explained by nutrient availability, suggesting improvement of factors other than plant nutrition. There was no detectable influence of texture (soils with either 11–14 or 45–49% clay) when low quality organic matter was applied (sawdust, biochar), whereas productivity was 8, 15, and 39% greater (P < 0.05) on sandier than heavier textured soils with high quality organic matter (green and animal manure) or only inorganic nutrient additions, respectively. Across the entire degradation range, organic matter additions decreased the need for additional inorganic fertilizer N irrespective of the quality of the organic matter. For low quality organic resources (biochar and sawdust), crop yields were increasingly responsive to inorganic N fertilization with increasing soil degradation. On the other hand, fertilizer N additions did not improve soil productivity when high quality organic inputs were applied. Even with the tested full N–P–K fertilization, adding organic matter to soil was required for restoring soil productivity and most effective in the most degraded sites through both nutrient delivery (with green manure) and improvement of SOC (with biochar).     

Tree Species Effects on Soil Organic Matter Dynamics: The Role of Soil Cation Composition

Abstract We studied the influence of tree species on soil carbon and nitrogen (N) dynamics in a common garden of replicated monocultures of fourteen angiosperm and gymnosperm, broadleaf and needleleaf species in southwestern Poland. We hypothesized that species would influence soil organic matter (SOM) decomposition primarily via effects on biogeochemical recalcitrance, with species having tissues with high lignin concentrations retarding rates of decomposition in the O and A horizons. Additionally, because prior work demonstrated substantial divergence in foliar and soil base cation concentrations and soil pH among species, we hypothesized that species would influence chemical stabilization of SOM via cation bridging to mineral surfaces in the A-horizon. Our hypotheses were only partially supported: SOM decomposition and microbial biomass were unrelated to plant tissue lignin concentrations, but in the mineral horizon, were significantly negatively related to the percentage of the cation exchange complex (CEC) occupied by polyvalent acidic (hydrolyzing) cations (Al and Fe), likely because these cations stabilize SOM via cation bridging and flocculation and/or because of inhibitory effects of Al or low pH on decomposers. Percent CEC occupied by exchangeable Al and Fe was in turn related to both soil clay content (a parent material characteristic) and root Ca concentrations (a species characteristic). In contrast, species influenced soil N dynamics largely via variation in tissue N concentration. In both laboratory and in situ assays, species having high-N roots exhibited faster rates of net N mineralization and nitrification. Nitrification:mineralization ratios were greater, though, under species with high exchangeable soil Ca²⁺. Our results indicate that tree species contribute to variation in SOM dynamics, even in the mineral soil horizons. To our knowledge the influence of tree species on SOM decomposition via cation biogeochemistry has not been demonstrated previously, but could be important in other poorly buffered systems dominated by tree species that differ in cation nutrition or that are influenced by acidic deposition.     

Bacterial Degradation of Dissolved Organic Matter from Two Northern Michigan Streams

This study used high-pressure size exclusion chromatography (HPSEC) to measure the changes in molecular weight distributions of dissolved organic matter (DOM) of two Northern Michigan streams following inoculation with bacterial concentrates from the same locations. During the initial 12 h of the experiment, weight average molecular weight (M _w ) of DOM decreased, as high molecular weight components were lost from solution. After 12 h, the M _w of DOM increased, primarily because of a loss of intermediate to lower molecular weight components. Leucine incorporation showed little or no bacterial metabolism during the first 12 h, but metabolism increased substantially after 12 h. The initial loss of high molecular weight components during the period of little or no bacterial metabolism suggests preferential adsorption of these components to the bacterial surfaces, perhaps followed by metabolism. This suggested interpretation is consistent with previous observations of preferential adsorption of higher molecular weight components to viable but non-metabolizing Bacillus subtilis and to mineral surfaces. The latter loss of lower molecular weight components was most likely due to bacterial metabolism of the DOM, which is consistent with previous observations that lower molecular weight components are more biodegradable. The HPSEC technique uses 254 nm wavelength for detection and focuses primarily on humic- and fulvic-type components rather than low molecular weight organic molecules, such as carbohydrates. Thus, results confirmed that humic/fulvic components are biodegradable, but did not address other DOM components.     

Estimation of Standing Stock and Decomposition Rates of Labile Organic Matter in Waters of Novorossiisk Bay,Black Sea

The annual dynamics of the decomposition rate, standing stock, and residence time of labile organic matter as an index of full self-purification were investigated in Novorossiisk Bay, Black Sea. The results are suggestive of fairly effective processes of biological self-purification in polluted waters of the bay. The decomposition rate was highest (0.3–0.7 mgO₂/l per day) during the summer, and it decreased by 4–8 times in winter. The residence time of labile organic matter was 97–104 days in winter and 8–11 days in summer. Oxygen consumption rates measured in different areas of the bay conformed to their trophic status and were not above the normal level for summer.     

Extracellular Enzyme Activities and Soil Organic Matter Dynamics for Northern Hardwood Forests receiving Simulated Nitrogen Deposition

Anthropogenic nitrogen enrichment alters decomposition processes that control the flux of carbon (C) and nitrogen (N) from soil organic matter (SOM) pools. To link N-driven changes in SOM to microbial responses, we measured the potential activity of several extracellular enzymes involved in SOM degradation at nine experimental sites located in northern Michigan. Each site has three treatment plots (ambient, +30 and +80 kg N ha⁻¹ y⁻¹). Litter and soil samples were collected on five dates over the third growing season of N treatment. Phenol oxidase, peroxidase and cellobiohydrolase activities showed significant responses to N additions. In the Acer saccharum–Tilia americana ecosystem, oxidative activity was 38% higher in the litter horizon of high N treatment plots, relative to ambient plots, while oxidative activity in mineral soil showed little change. In the A. saccharum–Quercus rubra and Q. velutina–Q. alba ecosystems, oxidative activities declined in both litter (15 and 23%, respectively) and soil (29 and 38%, respectively) in response to high N treatment while cellobiohydrolase activity increased (6 and 39% for litter, 29 and 18% for soil, respectively). Over 3 years, SOM content in the high N plots has decreased in the Acer–Tilia ecosystem and increased in the two Quercus ecosystems, relative to ambient plots. For all three ecosystems, differences in SOM content in relation to N treatment were directly related (r² = 0.92) to an enzyme activity factor that included both oxidative and hydrolytic enzyme responses.     

Cadmium Sorption Characteristics of Soil Amendments and its Relationship with the Cadmium Uptake by Hyperaccumulator and Normal Plants in Amended Soils

In order to select appropriate amendments for cropping hyperaccumulator or normal plants on contaminated soils and establish the relationship between Cd sorption characteristics of soil amendments and their capacity to reduce Cd uptake by plants, batch sorption experiments with 11 different clay minerals and organic materials and a pot experiment with the same amendments were carried out. The pot experiment was conducted with Sedum alfredii and maize (Zea mays) in a co-cropping system. The results showed that the highest sorption amount was by montmorillonite at 40.82 mg/g, while mica was the lowest at only 1.83 mg/g. There was a significant negative correlation between the n value of Freundlich equation and Cd uptake by plants, and between the logarithm of the stability constant K of the Langmuir equation and plant uptake. Humic acids (HAs) and mushroom manure increased Cd uptake by S. alfredii, but not maize, thus they are suitable as soil amendments for the co-cropping S. alfredii and maize. The stability constant K in these cases was 0.14–0.16 L/mg and n values were 1.51–2.19. The alkaline zeolite and mica had the best fixation abilities and significantly decreased Cd uptake by the both plants, with K ≥ 1.49 L/mg and n ≥ 3.59.     

Impact of Anthropogenic Organic Matter on the Distribution Patterns of Sediment Microbial Community from the Yangtze River,China

Abstract

How microbes respond to substantial and increasing anthropogenic disturbance remains an open question in river systems. We tested the hypothesis that the source and distribution of anthropogenic organic matter (OM) were significant factors affecting the spatial variation of the microbial community composition of the Yangtze River sediments. Bulk geochemical proxies and lignin phenols suggested a general decrease of terrestrial C3 plants or soil OM input from the middle to the lower reaches. Fecal sterols inferred higher sewage contamination levels in the middle reaches. Polycyclic aromatic hydrocarbons (PAHs) distribution indicated a dominant biomass and coal combustion signal in the middle reaches, whereas a mixed source including petroleum combustion in the lower reaches. Phylogenetic analysis revealed a large portion of Methanobacteria and Verrucomicrobia enriched in the middle reaches, whereas OM-degrading bacteria, including Flavobacteria, Acidobacteria, and Alphaproteobacteria were dominant in the lower reaches. Quantitative PCR analyses and multivariate analysis further demonstrated that sources and distribution of OM had combined effects in shaping alpha and beta-diversity of sediment microbial communities. Sewage discharge and incomplete OM combustion, respectively, were associated with Methylococcaceae, Chloroflexi, and Bacteroidetes groups. This study provides a foundation for further understanding of the river sediment microbial composition, considering the continued increase of anthropogenic influences.     

Sorption and Desorption of Napropamide in Sandy Soil Amended with Chicken Dung and Palm Oil Mill Effluent

Beach Ridges Interspersed with Swales (BRIS) is a sandy soil and in Malaysia it is found exclusively in the east coast of Peninsular Malaysia. It is a marginal soil because of its low nutrient and water-holding capacity. However, with proper management and organic matter amendments some areas with BRIS soil are cultivated. Napropamide is a selective herbicide widely used to control weeds in BRIS soil. No previous studies have been reported on the effects of organic matter amendments on napropamide sorption in BRIS soil. This study was conducted to determine sorption and desorption of napropamide in BRIS soil amended with chicken dung (CD) and palm oil mill effluent (POME) at 0, 20, 40, and 80 Mg ha^?1. Potential interaction of dissolved organic carbon (DOC) with napropamide and their competition for sorption sites were also determined. Sorption isotherm data were fitted to the log-transformed Freundlich's equation. Sorption of napropamide was higher in soils amended with CD and POME as compared to non-amended soil. At the same rates of application, sorption was higher in soil amended with CD than POME. The Freundlich's coefficient (K_f) values were 0.22, 3.96, and 41.6 for nonamended soil, soil amended with 80 Mg ha^?1 POME, and soil amended with 80 Mg ha^?1 CD, respectively. Desorption of napropamide showed positive hysteresis and the hysteresis were greater with higher rates of CD and POME. There was no association between napropamide and DOC extracted from BRIS soil amended with either CD or POME and also there were no competitions between napropamide and DOC extracted from either CD or POME for sorption sites of the soil samples.     

Organic Matter Preservation and Microbial Community Accumulations in Deep-Hypersaline Anoxic Basins

The Eastern Mediterranean Sea hosts several deep hypersaline anoxic basins (DHABs) such as the Bannock, L'Atalante, Discovery, and Urania which, due to strong salinity gradients, have a limited exchange with the overlying seawater. In the present study, a series of environmental variables associated with the origin and quality of organic matter were thoroughly investigated in an attempt to understand the function of these unique ecosystems. The redox potential of sediments collected from the brines as well as from reference sites varied from ?136 to 543 mV and salinity varied from 38 to 380 psu. Principal component analysis of chemical characteristics, including salinity, redox potential, organic carbon and nitrogen content, and C/N ratio grouped the sediments into two major clusters according to their redox state. Aliphatic hydrocarbon analysis revealed that the organic matter in the DHABs was predominantly of terrestrial origin but there was also evidence for petroleum inputs and for organic matter of phototrophic origin. Phospholipid linked fatty acids (PLFA) which were employed to assess the composition of microbial communities were found in greater abundance in stations situated inside the anoxic basins providing also strong evidence for the presence of methanotrophs and sulfate reducers. These results may represent an enhanced preservation of organic matter and an accumulation of microorganisms in these extreme environments. Heterogeneity in microbial community fatty acid profiles was documented between the anoxic sediments and the oxic and suboxic stations. However there were no significant correlations between PLFA and organic matter parameters. Redox conditions appear to influence microbial community composition, highlighting the role of the redox state as a regulator of organic matter preservation and microbial community accumulations in these ancient hypersaline anoxic lakes.