Total Organic Carbon Ratio Research Articles

The influence of tree species composition on the storage and mobility of semivolatile organic compounds in forest soils

Soil contamination with PCBs and PAHs in adjacent forest plots, characterized by a distinct composition in tree species (spruce only, mixed and beech only), was analyzed to investigate the influence of ecosystem type on contaminant mobility in soil under very similar climate and exposure conditions. Physical-chemical properties and contaminant concentrations in litter (L), organic (F, H) and mineral (A, B) soil horizons were analyzed. Contaminant distribution in the soil core varied both in relation to forest type and contaminant group/properties. Contaminant mobility in soil was assessed by examining the ratios of total organic carbon (TOC)-standardized concentrations across soil horizons (Enrichment factors, EFTOC) and the relationship between EFTOC and the octanol-water equilibrium partitioning coefficient (KOW). Contaminant distribution appeared to be highly unsteady, with pedogenic/biogeochemical drivers controlling contaminant mobility in organic layers and leaching controlling accumulation in mineral layers. Lighter PCBs displayed higher mobility in all forest types primarily controlled by leaching and, to a minor extent, diffusion. Pedogenic processes controlling the formation of soil horizons were found to be crucial drivers of PAHs and heavier PCBs distribution. All contaminants appeared to be more mobile in the soil of the broadleaved plot, followed by mixed canopy and spruce forest. Increasing proportion of deciduous broadleaf species in the forest can thus lead to faster degradation or the faster leaching of PAHs and PCBs. The composition of humic substances was found to be a better descriptor of contaminant concentration than TOC.

Mangrove forest degradation indicated by mangrove-derived organic matter in the Qinzhou Bay, Guangxi, China, and its response to the Asian monsoon during the Holocene climatic optimum

The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum (HCO), using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources: mangrove-derived, terrigenous, and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope (δ 13Corg) and the molar ratio of total organic carbon to total nitrogen (C/N). The percentage of mangrove-derived organic matter (MOM) contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.

Post-treatment of refinery wastewater effluent using a combination of AOPs (H2O2 photolysis and catalytic wet peroxide oxidation) for possible water reuse. Comparison of low and medium pressure lamp performance

The main aim of this work was to study the feasibility of multi-barrier treatment (MBT) consisting of filtration, hydrogen peroxide photolysis (H2O2/UVC) and catalytic wet peroxide oxidation (CWPO) for post-treatment of petroleum refinery effluent. Also the possibility of water reuse or safe discharge was considered. The performance of MBT using medium (MP) and low (LP) pressure lamps was compared as well as operation and maintenance (O&M) cost. Decomposition of organic compounds was followed by means of gas chromatography–mass spectrometry (GC–MS), total organic carbon (TOC) and chemical oxygen demand (COD) analysis.After filtration step (25 μm) turbidity and concentration of suspended solids decreased by 92% and 80%, respectively. During H2O2/UVC process with LP lamp at optimal conditions (H2O2:TOC ratio 8 and UVC dose received by water 5.28 WUVC s cm−2) removal of phenolic compounds, TOC and COD was 100%, 52.3% and 84.3%, respectively. Complete elimination of phenolic compounds, 47.6% of TOC and 91% of COD was achieved during H2O2/UVC process with MP lamp at optimal conditions (H2O2:TOC ratio 5, UVC dose received by water 6.57 WUVC s cm−2). In order to compare performance of H2O2/UVC treatment with different experimental set up, the UVC dose required for removal of mg L−1 of COD was suggested as a parameter and successfully applied.The hydrophilicity of H2O2/UVC effluent significantly increased which in turn enhanced the oxidation of organic compounds during CWPO step. After H2O2/UVC treatment with LP and MP lamps residual H2O2 concentration was 160 mg L−1 and 96.5 mg L−1, respectively. Remaining H2O2 was fully consumed during subsequent CWPO step (6 and 3.5 min of contact time for LP and MP, respectively). Total TOC and COD removal after MBT was 94.7% and 92.2% (using LP lamp) and 89.6% and 95%, (using MP lamp), respectively. The O&M cost for MBT with LP lamp was estimated to be 0.44 € m−3 while with MP lamp it was nearly five times higher. Toxicity assessment was performed using two marine species (Vibrio fischeri and Paracentrotus lividus sea-urchin) after each treatment step. The highest toxicity was attributed to H2O2/UVC effluent for both tested species. After MBT a drastic decrease of toxicity was achieved.

Atmospheric aerosols local–regional discrimination for a semi-urban area in India

In the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI), measurements were carried out with a sequential filter-based aerosol sampler and on-line instruments for aerosol composition and behaviour at Gual Pahari, close to New Delhi. In fine mode (PM2.5), the secondary organic carbon (SOC) to total organic carbon ratio was 46%. This indicated that condensation of SOC on fine size particles could occur rapidly which may be related to the growth of aerosols and the potential to the size of cloud condensation nuclei in the region.Source region discrimination was improved significantly through coupling conditional probability functions with receptor modelling, and validation through volume size distribution. The air masses from industrial and dense populated regions show a mix of local as well as regional emissions to fine mode aerosols. The back-trajectory analysis captured the long-range transport of sea-salt aerosols enriched with mineral dust. The surface wind directions identified the influence of local emission activities.

Variations in sedimentary environments in the forearc and backarc regions of the Ryukyu Arc since 25 ka based on CNS analysis of sediment cores

In this study, we analyzed 14C dates, grain size, and carbon, nitrogen, and sulfur element contents using sediment cores collected at the eastern edge of the backarc and forearc of the Ryukyu Arc, and demonstrated different temporal variations in CaCO3 contents and ratios of total organic carbon and total nitrogen contents (C/N ratios) compared with previous studies of the Okinawa Trough cores. Increases in CaCO3 contents and decreases in C/N ratios, from the Last Glacial Maximum to the Holocene, in the Okinawa Trough backarc basin correspond with sea-level changes. These results demonstrate that the sedimentary environment in the Okinawa Trough is influenced by sediment supply from mainland China, and reveal temporal variations reflecting changes in the Yangtze River mouth that accompany sea-level changes. In contrast, CaCO3 contents of cores in this study are double those in the Okinawa Trough cores, and show an increasing trend at 7.5–6.0 cal ka BP. Additionally, in the forearc core, the profile of the CaCO3 content decreases at 11.5–8.1 cal ka BP. These variations in CaCO3 contents suggest that marine productivity changed with sea surface trophic conditions. In addition, the lateral transport of terrigenous sediment by the Kuroshio and Ryukyu currents might contribute to an increased CaCO3 content by reducing the influence of dilution. Variations in the C/N ratio after 7.8 cal ka BP suggest that the Kuroshio Countercurrent has varied in strength at 1–2 ka intervals since the early Holocene, influencing the deposition of terrigenous organic matter from the Okinawa Islands in the deeper parts of the east backarc.

Seagrass (Zostera marina) Colonization Promotes the Accumulation of Diazotrophic Bacteria and Alters the Relative Abundances of Specific Bacterial Lineages Involved in Benthic Carbon and Sulfur Cycling.

Seagrass colonization changes the chemistry and biogeochemical cycles mediated by microbes in coastal sediments. In this study, we molecularly characterized the diazotrophic assemblages and entire bacterial community in surface sediments of a Zostera marina-colonized coastal lagoon in northern China. Higher nitrogenase gene (nifH) copy numbers were detected in the sediments from the vegetated region than in the sediments from the unvegetated region nearby. The nifH phylotypes detected were mostly affiliated with the Geobacteraceae, Desulfobulbus, Desulfocapsa, and Pseudomonas. Redundancy analysis based on terminal restriction fragment length polymorphism analysis showed that the distribution of nifH genotypes was mostly shaped by the ratio of total organic carbon to total organic nitrogen, the concentration of cadmium in the sediments, and the pH of the overlying water. High-throughput sequencing and phylogenetic analyses of bacterial 16S rRNA genes also indicated the presence of Geobacteraceae and Desulfobulbaceae phylotypes in these samples. A comparison of these results with those of previous studies suggests the prevalence and predominance of iron(III)-reducing Geobacteraceae and sulfate-reducing Desulfobulbaceae diazotrophs in coastal sedimentary environments. Although the entire bacterial community structure was not significantly different between these two niches, Desulfococcus (Deltaproteobacteria) and Anaerolineae (Chloroflexi) presented with much higher proportions in the vegetated sediments, and Flavobacteriaceae (Bacteroidetes) occurred more frequently in the bare sediments. These data suggest that the high bioavailability of organic matter (indicated by relatively lower carbon-to-nitrogen ratios) and the less-reducing anaerobic condition in vegetated sediments may favor Desulfococcus and Anaerolineae lineages, which are potentially important populations in benthic carbon and sulfur cycling in the highly productive seagrass ecosystem.

Assessment of distribution and sources of pyrogenic carbon in the lower course of the Guadiana River (SW Iberian Peninsula)

PurposeThe main goal of this work was to determine the pyrogenic carbon (PyC) distribution in surficial sediments for the last 40 km of the Guadiana River (SW Iberian Peninsula). In addition, the changes in the contribution of terrestrial and marine organic matter (OM) sources and their relationship with the PyC contents were assessed.Materials and methodsSediments were collected from 22 stations within the lower course of the Guadiana River. All the samples were analyzed for total organic carbon (TOC), total nitrogen (TN), organic carbon to nitrogen atomic ratios (C/N), and stable carbon isotope ratio (δ13C) as indicators of changes in the sources of OM. PyC was determined according to the chemo-thermal oxidation method (CTO-375).Results and discussionTOC ranged from 0.25 to 2.37 %dw. The greatest TOC contents were located in sediments collected at the middle estuary. The C/N values ranged from 7.7 to 12.7, with slight relative increase in the marine input compared to pre-Alqueva times. Similar C/N ranges are representative of native soil OM, lacustrine OM, and local sedimentary OM. The δ 13C values of the sediment samples ranged from –25.0 to –27.6 ‰ illustrating a signature of C3 higher plants, marsh-plants, lacustrine plants, and freshwater algae present in the area of study and in the forests located upstream. PyC ranged between 0.17 and 0.74 gkg−1, with the highest contents measured in samples located close to urbanized areas. Sediments collected at the middle estuary, within a rural area, showed the lowest proportions of PyC relative to the percent of TOC (≤4 % TOC). The negative relationship between PyC to TOC ratio and TOC contents confirmed the selective preservation of PyC to degradation in the sedimentary OM of the Guadiana estuary. The carbon isotope composition of the final material after applying the CTO-375 method (hereafter called δ13CPyC) was ˂–30 ‰, suggesting that the PyC fraction was mainly composed of a mixture of fossil fuels and C3-charred biomass. Nevertheless, selective loss of the less recalcitrant OM fractions due to degradation and/or chemical alteration might contribute to lighter carbon isotope values of PyC.ConclusionsGeochemical data showed that sedimentary OM was composed of a mix of different OM sources, with a slight increase in the marine input after the Alqueva dam went into operation. The PyC content was higher close to urbanized areas of the Guadiana River estuary. The selective preservation of PyC in the sedimentary OM of the Guadiana estuary was observed.

4-Nitroaniline Degradation by TiO2Catalyst Doping with Manganese

Stainless steel anode covered with layer film of TiO2doped with manganese was utilized to decompose 4-nitroaniline in rectangular borosilicate glass reactor, while stainless steel mesh was chosen as cathode; the anode and cathode were connected to the direct-current power; meantime two 60 W (λmax= 365 nm) UV lamps were used as light source. The microstructures on TiO2before and after being doped with manganese were analyzed by energy disperse X-ray (EDX) and X-ray diffraction (XRD). The performance of degradation of 4-nitroaniline was evaluated by analyzing cracking ratio of 4-nitroaniline ring, the chemical oxygen demand (COD), and total organic carbon (TOC) in remaining solution. Monitored parameters during all the photocatalytic reaction including dissolved oxygen, direct voltage, and radiation dosage of ultraviolet rays were investigated. When dissolved oxygen concentration, direct voltage, and radiation dosage of ultraviolet rays were, respectively, equivalent to 9 mg/L, 24 V, and 1200 μW/cm2, the degradation ratio of 4-nitroaniline reached maximum. The experimental results indicated that cracking ratio of 4-nitroaniline ring and the removal ratio of COD and TOC were, respectively, more than 99%, 85%, and 80% when reaction was run for 10 hours. The values of COD and TOC were, respectively, less than 16 mg/L and 8 mg/L while the experiment was finished.

Characterization and energy potential of food waste from catering service in Hangzhou, China.

Safe disposal of food waste is becoming an impending issue in China with the rapid increase of its production and the promotion of environmental awareness. Food waste from catering services in Hangzhou, China, was surveyed and characterized in this study. A questionnaire survey involving 632 units across the urban districts showed that 83.5% of the food waste was not properly treated. Daily food waste production from catering units was estimated to be 1184.5 tonnes. The ratio of volatile solid to total solid, easily biodegradable matter (including crude fat, crude protein and total starch) content in total solid and the ratio of total organic carbon to nitrogen varied in ranges of 90.1%-93.9%, 60.9%-72.1%, and 11.9-19.9, respectively. Based on the methane yield of 350 mL g VS(-1) in anaerobic batch tests, annual biogas energy of 1.0 × 10(9) MJ was estimated to be recovered from the food waste. Food waste from catering services was suggested to be an attractive clean energy source by anaerobic digestion.

Applicability of Ozone and Biological Activated Carbon for Potable Reuse

The Upper San Gabriel Valley Municipal Water District in California is considering groundwater replenishment as a potential strategy to augment its potable water supply. This case study demonstrates the broad applicability of ozone and biological activated carbon (BAC) for such potable reuse systems based on recently developed criteria and models for bulk organics, trace organic contaminants, disinfection byproducts, and cost. Using an advanced treatment train composed of ozone (ozone to total organic carbon ratio of 1.0) and BAC (empty bed contact time of 20 min), a 10 million gallon per day potable reuse facility can achieve savings of $25–$51 million in capital costs, $2–$4 million per year in operations and maintenance costs, and 4–8 GWh per year in energy consumption in comparison to alternative treatment trains with reverse osmosis. This ozone-based treatment train is also capable of achieving public health criteria recently developed by the California Department of Public Health and the National Water Research Institute for potable reuse applications.

The optimization of chlorine dose in water treatment process in order to reduce the formation of disinfection by-products

The main threat to human health is associated with organic compounds, which are found in the natural water ecosystem. The law relating to drinking water quality protects consumers’ health. Thus, the need to remove disinfection by-products (DBP) precursors requires the application of high-efficient water treatment processes. Usually, chlorine is used to disinfection, and then, haloforms are generated. Well-calibrated model, estimating the concentration of DBP in treated water, can be a useful tool for predicting the quantity of trihalomethanes in water in the distribution network. Such a model makes it also possible to identify the critical control points in the monitoring process. This paper presents the statistical analysis of chloroform formation in treated water, based on laboratory tests. The chloroform concentration is expressed as a function of factors, which determine kinetics of the chemical reaction of organic compounds with chlorine. Two new variables—the ratio of total organic carbon and chloroform and the ratio of chlorine consumption and chlorine dose, both obtained after 1 h of the reaction—were taken into account. From the function predicting the chloroform concentration, one can determine the optimal dose of chlorine in the disinfection of water in dynamic operational conditions.

Black shale deposition during Toarcian super-greenhouse driven by sea level

Abstract. One of the most elusive aspects of the Toarcian oceanic anoxic event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the end of the overarching positive trend in the carbon isotopes that characterises the T-OAE. In the present study, we have attempted to establish a sequence stratigraphic framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a combination of mineralogical (quartz and clay relative abundance) and geochemical (Si, Zr, Ti and Al) measurements. Combined with the evolution in redox sensitive elements (Fe, V and Mo), the data suggest that expression of anoxia was hampered in European epicontinental seas during most of the T-OAE (defined by the positive carbon isotope trend) due to insufficient water depth that prevented stratification of the water column. Only the first stratigraphic occurrence of black shales in Europe corresponds to the "global" event. This interval is characterised by >10% Total Organic Carbon (TOC) content that contains relatively low concentration of molybdenum compared to subsequent black shale horizons. Additionally, this first black shale occurrence is coeval with the record of the major negative Carbon Isotope Excursion (CIE), likely corresponding to a period of transient greenhouse intensification likely due to massive injection of carbon into the atmosphere–ocean system. As a response to enhanced weathering and riverine run-off, increased fresh water supply to the basin may have promoted the development of full anoxic conditions through haline stratification of the water column. In contrast, post T-OAE black shales during the serpentinum and bifrons Zones were restricted to epicontinental seas (higher Mo to TOC ratios) during a period of relative high sea level, and carbon isotopes returning to pre-T-OAE values. Comparing palaeoredox proxies with the inferred sequence stratigraphy for Sancerre suggests that episodes of short-term organic carbon enrichment were primarily driven by third-order sea level changes. These black shales exhibit remarkably well-expressed higher-frequency cyclicities in the oxygen availability in the water column whose nature has still to be determined through cyclostratigraphic analysis.

A Novel Approach for Inferring the Proportion of Terrestrial Organic Matter Input to Marine Sediments on the Basis of TOC:TN and δ<sup>13</sup>C<sub>org</sub> Signatures

The ratio of total organic carbon to total nitrogen (TOC:TN) and the stable carbon isotope ratio of organic matter (δ13Corg) are widely applied for inferring the origin of organic matter (OM) in Quaternary marine sediments. A plot of TOC:TN vs. δ13Corg is useful for such studies but is strongly based on qualitative constraints. This study is based on the qualitative characterization of the source of Quaternary OM via analysis of TOC:TN and δ13Corg signatures, but also proposes a probability parameter, which combines both signatures, to infer the amount of Terrestrial OM Input (TOMI). This index provides a method for quantifying the proportion of terrestrial OM vs. marine OMin a more comprehensive manner. The TOMI index concept was applied to a study area in theJoetsuBasin, eastern margin of theJapanSea, where previous studies have characterized theOMfrom the Last Glacial Maximum (LGM) to the present. The upwards increase in TOC indicates thatOMproduction during the Holocene was higher than during the LGM. The enriched δ13Corg signature upwards and decrease in TOC:TN suggest predominantly marine phytoplankton OM during the Holocene. Throughout the LGM, low OM production with depleted δ13Corg values and high TOC:TN values in the sediments suggest a predominantly C3 terrestrial plant source for the OM. Using these data, it was possible to calculate a proxy for a sea level variation curve during that period and to investigate the influence of the proximity of the coastal line to the continental slope on the input of terrestrial material to the basin. The proposal provides information for the application of sequence stratigraphic concepts. The TOMI index could confirm that the proximity to the shoreline and shelf break has a strong influence on the input of terrestrial material during lowstand periods.

Effects of nonylphenols on soil microbial activity and water retention

The main aim of this study is to analyze the influence of 4-nonylphenol (NP) on soil water retention and biological activity. Two doses of 4-nonylphenol (25 and 50mgkg−1) were tested in a loam soil with and without peat amendment. In general, one week after the start of the experiment, the soil water content retained at −0.75MPa of soil suction was 18% higher in the soil amended and its basal respiration (BR) was 15% higher than soil without peat. In contrast, the microbial activity indices (CM: coefficient of mineralization or BR:total organic carbon (TOC) ratio; Cmic:Corg: microbial biomass carbon (MBC):TOC ratio; qCO2: metabolic quotient or BR:MBC ratio) were higher in the soil without peat, compared to the soil amended with peat. On the other hand, the addition of NP to soil was able to modify soil biological but not physical (water retention, desorption) properties. When soil was amended with peat, MBC was reduced one week after applying NP. In contrast, no effects of NP on MBC were observed in the soil without peat. BR was reduced by 16% one week after applying 50mgkg−1 of NP to soil with peat, and was increased by 46% one week after applying 25mgkg−1 of NP to soil without peat. The effects of NP on MBC and BR could be associated more with the adsorption of NP by soil organic matter, while changes in CM or Cmic:Corg ratio were more closely related to changes in soil water retention. The potential toxic effects of NP (high qCO2 values) were only observed in the absence of peat amendments. Peat addition reduced NP toxic effects on microorganisms.

Evaluation of maturity and stability parameters of composts prepared from farm wastes

A composting experiment was carried out to study changes in physical [color, odor, temperature, organic matter (OM) loss], chemical [C:N ratio, water-soluble organic carbon (Cw):organic N (Norg) ratio, NH4 +-N and NO3 −-N, humic acid (HA):fulvic acid (FA) ratio, humification index (HI) and cation-exchange capacity (CEC):total organic carbon (TOC) ratio)] and biological [seed germination index (GI)] parameters to assess compost maturity and stability over a period of 150 days. Five composts were prepared using a mixture of different farm wastes with or without enrichment of N, rock phosphate (RP) and microorganism (MO) inoculation. All the composts appeared to change to a granular and dark grey color without foul odor, and attained a constant temperature with no measurable changes (ambient level) at 120 days of composting. Correlation analysis showed that the optimal values of the selected parameters for our experimental conditions are as follows: organic matter loss > 42%, C:N ratio < 15, HA:FA ratio > 1.9, HI > 30%, CEC:TOC ratio > 1.7 and Cw:Norg ratio < 0.55. Composts enriched with N + RP or N + RP + MO matured at 150 and 120 days, respectively, whereas composts without any enrichment or enrichment with N or RP + MO did not mature even at 150 days of composting.

Evaluation of Maturity and Stability Parameters of Composts Prepared from Organic Wastes and Their Response to Wheat

The objective of this study was to evaluate changes in physical, chemical and biological parameters to assess the maturity and stability of composts prepared from mixture of different organic wastes over a time period of 150 days. Six different composts were prepared using a mixture of different organic wastes with or without enrichment of rock phosphate (RP), microorganism inoculation (MO) and agro-industrial wastes (sewage sludge, pressmud, poultry waste). All the composts attained a constant temperature with no measurable changes (ambient level) at 120 days of composting. Compost maturity should be assessed by measuring two or more compost parameters, and that parameters of compost maturity need to satisfy the following threshold values: organic matter loss >42 %, C:N ratio 1.9, humification index >30 %, cation exchange capacity:total organic carbon ratio >1.7 and germination index >70 %. Ambient temperature, decrease in bacterial and fungal counts along with increase in actinomycetes count and stable at the end of composting could also be used as stability parameters. Composts enriched with RP, MO and agro-industrial wastes matured earlier compared to un-enriched composts. Application of agro-industrial waste composts significantly increased wheat yield compared with addition of their raw materials. Agro-industrial waste composts applied with recommended dose of NK fertilizers produced wheat yield comparable to that obtained with recommended dose of NPK fertilizers, indicating a net saving of 100 % P fertilizer.

Enhanced decomposition of (4-chloro-2-methylphenoxy) acetic acid by combined ultrasonic and oxidative treatment

Combined ultrasonic (US) irradiation and sodium peroxodisulfate (Na2S2O8) treatment has been investigated for promotion of both decomposition of (4-chloro-2-methylphenoxy) acetic acid (MCPA) and mineralization of organic residues. This treatment is expected to accelerate both reactions, because the US cavitation effect promotes the production of radicals, such as SO4−· and OH·, by the decomposition of Na2S2O8 and water. In this study, decomposition experiments were performed on 100 ppm MCPA aqueous solutions in a sonoreactor at reaction temperatures of 298–333 K with US irradiation alone, Na2S2O8 treatment alone, and the combination of US and Na2S2O8 treatment. It was found that the combined treatment achieved a higher MCPA decomposition rate and total organic carbon (TOC) removal ratio than either treatment alone. The decomposition ratios of both MCPA and TOC increased with reaction temperature, and especially steep increases were observed at 333 K due to a significant promotion of thermal decomposition of Na2S2O8. The production of radical species was also promoted by the combined treatment. These results suggest that the higher MCPA decomposition rate and TOC removal ratio are due to the increased formation of sulfate and hydroxyl radicals via thermal and US decomposition of Na2S2O8.

Selenium as paleo-oceanographic proxy: A first assessment

Selenium (Se) is an essential trace element, which, with multiple oxidation states and six stable isotopes, has been suggested as a potentially powerful paleoenvironmental proxy. In this study, bulk Se concentrations and isotopic compositions were analyzed in a suite of about 120 samples of fine-grained marine sedimentary rocks and sediments spanning the entire Phanerozoic. While the Se concentrations vary greatly (0.22–72ppm), the δ82/76Se values fall in a fairly narrow range from −1 to +1‰ (relative to NIST SRM3149), with the exception of laminated black shales from the New Albany Shale formation (Late Devonian), which have δ82/76Se values of up to +2.20‰. Black Sea sediments (Holocene) and sedimentary rocks from the Alum Shale formation (Late Cambrian) have Se to total organic carbon ratios (Se/TOC) and δ82/76Se values close to those found in modern marine plankton (1.72±0.15×10−6mol/mol and 0.42±0.22‰). For the other sedimentary sequences and sediments, the Se/TOC ratios show Se enrichment relative to modern marine plankton. Additional input of isotopically light terrigenous Se may explain the Se/TOC and δ82/76Se data measured in recent Arabian Sea sediments (Pleistocene). The very high Se concentrations in sedimentary sequences that include the Cenomanian–Turonian Oceanic Anoxic Event (OAE) 2 may reflect an enhanced input of volcanogenic Se to the oceans. As the latter has an isotopic composition not greatly different from marine plankton, the volcanogenic source does not impart a distinct signature to the sedimentary Se isotope record. The lowest average δ82/76Se values are observed in the OAE2 samples from Demerara Rise and Cape Verde Basin cores (δ82/76Se=−0.14±0.45‰) and could reflect fractionation associated with microbial or chemical reduction of Se oxyanions in the euxinic water column. In contrast, a limiting availability of seawater Se during periods of increased organic matter production and burial may be responsible for the elevated δ82/76Se values and low Se/TOC ratios in the black shales of the New Albany Shale formation. Overall, our results indicate that to unlock the full proxy potential of marine sedimentary Se records, we need to gain a much more detailed understanding of the sources, chemical speciation, isotopic fractionations and cycling of Se in the marine environment.

Environmental changes in Shamei Lagoon, Hainan Island, China: Interactions between natural processes and human activities

The sources and burial patterns of organic matter in Shamei Lagoon, Hainan, China, were investigated by analyzing the collected sediment cores, in terms of the variations in total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition (δ13C and δ15N), and the ratio of total organic carbon to total nitrogen (TOC/TN). On such a basis, the environmental evolution and primary productivity changes of the lagoon were revealed, and the impacts of both natural environmental changes and human activities were identified. Downcore variation patterns of the parameters representing sources and burial flux of organic matter were predominantly related to natural evolution of the lagoon from 1800 to 1950 and they were increasingly affected by human activities afterwards. In the period 1800–1900, the water exchange capacity of the lagoon declined substantially, but it was still suitable for the growth of marine phytoplankton, as is indicated by relatively high proportion and burial flux of organic matter originated from marine sources. During 1900–1950, the lagoon was transformed into a freshwater environment. After 1950, due to strong influence by human activities, the local freshwater phytoplankton became the major source of buried organic matter; at the same time, marine lost its niche and its burial flux was much lower than that of its freshwater counterpart. The large increment of buried freshwater organic matter also indirectly reflects the eutrophication trend since 1950.

Soil fungal community composition does not alter along a latitudinal gradient through the maritime and sub-Antarctic

We investigated the relationships between fungal community composition, latitude and a range of physicochemical parameters in 58 soils sampled from a 2370 km latitudinal gradient between South Georgia (54°S, 38°W) in the sub-Antarctic and Mars Oasis (72°S, 68°W) on Alexander Island in the southern maritime Antarctic. Our study, which is based on approximately ten times the number of samples used in previous similar studies, indicates that latitude and its associated environmental parameters are not related to fungal community composition. Significant changes in the composition of soil fungal communities were observed in relation to gradients of the ratio of total organic carbon to nitrogen, and, to a lesser extent, soil pH.