Organic carbon

Among prokaryotes, the large vacuolated marine sulphur bacteria are unique in their ability to store, transport and metabolize significant quantities of sulphur, nitrogen, phosphorus and carbon compounds. In this study, unresolved questions of metabolism, storage management and behaviour were addressed in laboratory experiments with Thioploca species collected on the continental shelf off Chile. The Thioploca cells had an aerobic metabolism with a potential oxygen uptake rate of 1760 lmol O 2 per dm 3 biovolume per h, equivalent to 4.4 nmol O 2 per min per mg protein. When high ambient sulphide concentrations (B200 lM) were present, a sulphide uptake of 6220 ± 2230 lmol H 2 S per dm 3 per h, (mean ± s.e.m., n ¼ 4) was measured. This sulphide uptake rate was six times higher than the oxidation rate of elemental sulphur by oxygen or nitrate, thus indicating a rapid sulphur accumulation by Thioploca. Thioploca reduce nitrate to ammonium and we found that dinitrogen was not produced, neither through denitrification nor through anammox activity. Unexpectedly, polyphosphate storage was not detectable by microautoradiography in physiological assays or by staining and microscopy. Carbon dioxide fixation increased when nitrate and nitrite were externally available and when organic carbon was added to incubations. Sulphide addition did not increase carbon dioxide fixation, indicating that Thioploca use excess of sulphide to rapidly accumulate sulphur rather than to accelerate growth. This is interpreted as an adaptation to infrequent high sulphate reduction rates in the seabed. The physiology and behaviour of Thioploca are summarized and the adaptations to an environment, dominated by infrequent oxygen availability and periods of high sulphide abundance, are discussed.

Elucidating the role of pyrogenic carbon (C pyr) as a global pool for CO 2 sequestration in temperate ecosystems requires information on the contribution of C pyr to soil organic carbon (SOC) across different climatic regions. We investigated the effect of climate and basic soil properties on the accumulation of C pyr in surface soils across the native North American prairies. Topsoil samples (0-10 cm) of 18 native grassland sites along temperature and precipitation transects from central Saskatoon, Canada, to south Texas, USA, were analyzed for benzenecarboxylic acids as molecular markers for C pyr after nitric acid oxidation in the bulk soil (<2 mm), clay-(<2 mm) and silt-sized (2-20 mm) separates. C pyr contributed between 4 and 18% to SOC, the major proportions of C pyr being mostly found in the clay and silt fractions. C pyr in soil did not correlate with basic inorganic soil properties such as pH or clay content, but it increased significantly as SOC contents increased (r 2 = 0.78; P < 0.001). Obviously, C pyr co-accumulated with dead biomass. Since this accumulation depends on climate, also C pyr contents in soil depend on climate and may be predicted by the logarithm of the ratio of mean annual temperature (MAT) to mean annual precipitation (MAP) (P < 0.05). We conclude that the natural potential of soils to sequester C pyr reflects both, (1) higher C pyr production at sites with high plant biomass in moist climates, and (2) lower C pyr residence time at soils acting as a CO 2 source in warm climates.

Ce travail montre l'application d'une nouvelle méthode fondée sur l'utilisation d'un spectromètre d'émission à plasma à couplage inductif (ICP) qui est capable de différencier les divers types de carbone. Le carbone organique total (COT) est obtenu par un étalonnage ordinaire après avoir éliminé complètement le carbone inorganique (CI) de l'échantillon. Pour la détermination du CI, un réacteur spécialement conçu a été adapté à l'appareil. Un échantillon d'un volume donné a été introduit dans le réacteur, puis on a rajouté de l'acide chlorhydrique et, fi nalement, le CO 2 produit a été envoyé vers le plasma. Dans ce cas, nous avons obtenu un signal transitoire. Le CI a été calculé grâce à la mesure des signaux provenant d'étalons de bicarbonate. Finalement, le carbone organique volatil (COV) a été obtenu en injectant un petit volume d'échantillon dans un réacteur à haute température (120-160ºC). Les composés volatils ont été transportés vers le plasma et un signal transitoire a été de nouveau obtenu. A propos des résultats obtenus, les limites de détection (LOD) étaient 0.05 μg/mL pour le COT et 0.03 μg/mL pour le CI. La répétabilité des méthodes était très bonne, les écarts-types relatifs étant inférieurs à 5% pour toutes les déterminations. En ce qui concerne les valeurs de COT et CI, la méthode fondée sur l'utilisation d'un ICP donne des résultats similaires à ceux obtenus avec des méthodes de référence (combustion à haute temperature et détection par infrarouge) pour le domaine de concentration compris entre 10 et 900 µg/L et 40 et 320 µg/L pour le COT et CI, respectivement. Dédié à Jean-Michel Mermet à l'occasion de sa dernière conférence * To w h o m c o r r e s p o n d a n c e s h o u l d b e a d d r e s s e d :

Epidemiologic studies have shown associations between ambient particulate matter (PM) and adverse health outcomes including increased mortality, emergency room visits, and time lost from school and work. The mechanisms of PM-related health effects are still incompletely understood, but a hypothesis under investigation is that many of the adverse health effects may derive from oxidative stress, initiated by the formation of reactive oxygen species (ROS) within affected cells. While the adverse effects from PM have historically been associated with the airborne concentration of PM and more recently fine-particle PM, we considered it relevant to develop an assay to quantitatively measure the ability of PM to catalyze ROS generation as the initial step in the induction of oxidative stress. This ability of PM could then be related to different sources, chemical composition, and physical and spatial/temporal characteristics in the ambient environment. The measurement of ROS-forming ability in relation to sources and other factors will have potential relevance to control of redox-active PM. If oxidative stress represents a relevant mechanism of toxicity from PM, the measurement of redox activity represents a first step in the elucidation of the subsequent downstream processes. We have developed an assay for PM redox activity, utilizing the reduction of oxygen by dithiothreitol which serves as an electron source. We have found that PM will catalyze the reduction of oxygen and have examined the distribution and chemical characteristics of the redox activity of PM fractions collected in different sites in the Los Angeles Basin. Samples of concentrated coarse, fine, and ultrafine PM, obtained with aerosol concentrators, were studied with regard to their chemical properties and redox activity. Redox activity was highest in the ultrafine fraction, in agreement with results indicating ultrafines were the most potent toward inducing that heme oxygenase expression and depleting intracellular glutathione, which has relevance to induction of oxidative stress. Comparison of the redox activity with chemical composition showed a reasonable correlation of redox activity with elemental carbon (r 2 ¼ 0:79), organic carbon (r 2 ¼ 0:53), and with benzo[ghi]perylene (r 2 ¼ 0:82), consistent with species typically found in mobile emission sources. r

It is only recently that freshwaters have been identified as important quantitative components of the carbon (C) cycle at global and regional scales. To date there are no studies that quantitatively predict the effects of alterations in temperature and flow regimes, individually, or in concert, on organic C dynamics in streams. To address this need, we applied a mechanistic model to simulate organic C dynamics in Mediterranean river networks under 27 different scenarios of altered temperature and flow regimes. We predict that the organic C dynamics in freshwaters in the Mediterranean, as well as in other semiarid regions, will be highly sensitive to global climate change owing to major increases in the degree of intermittency as well as in flood frequency and magnitude. Results indicate that flow regime alterations increase C export rates, whereas temperature alterations increase instream metabolism of organic C. However, flow regime alterations exhibit a much greater influence on C dynamics than do changes in the temperature regime. Reservoirs partly counteract the effects of flow extremes on C export rates, and their role in the C dynamics increases with increasing flow variability. The present study is one of the first studies to quantify the complex interactions between the flow and the temperature regime on C dynamics, emphasizing the key role of extreme events such as dry periods and floods, compared with overall trend effects. This information is pivotal in understanding the impact of future climate change on global C dynamics.

Evaluation of emerging diesel-particulate emissions control technology will require analytical procedures capable of continuous measurement of transient organic and elemental carbon emissions. Procedures based on the flame ionization properties of organic carbon and ...

In this paper, we have assessed the temporal, spatial and depth related variation of suspended particulate organic matter (POM) in the Bay of Bengal. For this purpose, suspended particulate matter (SPM) samples were collected from eight depths (2 to 1000 m) at 9 locations in the Bay of Bengal during July/August 2001 (Southwest monsoon, SWM), September/October 2002 (Fall Intermonsoon, FIM), and March/April 2003 (Spring Inter-monsoon, SPIM). The SPM samples were analyzed for chlorophyll a (Chl a), particulate organic carbon (POC) and total particulate nitrogen (TPN). The surface concentrations of POC varied from 4.3 to 11.1 µM C, 3.1 to 10.9 µM C, and 4.3 to 9.0 µM C during SWM, FIM, and SPIM, respectively. The levels of SPM, and the concentrations of Chl a, and POC were relatively higher in the offshore compared to the near shore stations, especially during SWM. The POC concentration and its contribution to the SPM were higher in the surface waters, and both decreased with increasing water column depth at most of the stations. The observed decrease with depth of POC indicates heterotrophic uptake and/or dilution by inorganic material, poor in POC. This was also reflected in the C/N ratio which generally increased with water column depth. The relatively low C/N and POC/Chl a ratios, and high Chl a and % POC during the SWM and FIM indicate the presence of relatively fresh POM in the Bay during these two seasons. The observed seasonal differences in the quality of POM appears to be governed by river runoff and the physical forces such as eddies which pump nutrients into the surface waters thereby enhancing biological production.

The UNMIX and Chemical Mass Balance (CMB) receptor models were used to investigate sources of PM 2.5 aerosols measured between March 2001 and February 2002 in Gwangju, Korea. Measurements of PM 2.5 particles were used for the analysis of carbonaceous species (organic (OC) and elemental carbon (EC)) using the thermal manganese dioxide oxidation (TMO) method, the investigation of seven ionic species using ion chromatography (IC), and the analysis of twenty-four metal species using Inductively Coupled Plasma (ICP)-Atomic Emission Spectrometry (AES)/ICP-Mass Spectrometry (MS). According to annual average PM 2.5 source apportionment results obtained from CMB calculations, diesel vehicle exhaust was the major contributor, accounting for 33.4% of the measured PM 2.5 mass (21.5 μg m − 3), followed by secondary sulfate (14.6%), meat cooking (11.7%), secondary organic carbon (8.9%), secondary nitrate (7.6%), urban dust (5.5%), Asian dust (4.4%), biomass burning (2.8%), sea salt (2.7%), residual oil combustion (2.6%), gasoline vehicle exhaust (1.9%), automobile lead (0.5%), and components of unknown sources (3.4%). Seven PM 2.5 sources including diesel vehicles (29.6%), secondary sulfate (17.4%), biomass burning (14.7%), secondary nitrate (12.6%), gasoline vehicles (12.4%), secondary organic carbon (5.8%) and Asian dust (1.9%) were identified from the UNMIX analysis. The annual average source apportionment results from the two models are compared and the reasons for differences are qualitatively discussed for better understanding of PM 2.5 sources. Additionally, the impact of air mass pathways on the PM 2.5 mass was evaluated using air mass trajectories calculated with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) backward trajectory model. Source contributions to PM 2.5 collected during the four air mass patterns and two event periods were calculated with the CMB model and analyzed. Results of source apportionment revealed that the contribution of diesel traffic exhaust (47.0%) in stagnant conditions (S) was much higher than the average contribution of diesel vehicle exhaust (33.4%) during the sampling period. During Asian dust (AD) periods when the air mass passed over the Korean peninsula, Asian dust and secondary organic carbon accounted for 25.2 and 23.0% of the PM 2.5 mass, respectively, whereas Asian dust contributed only 10.8% to the PM 2.5 mass during the AD event when the air mass passed over the Yellow Sea. The contribution of biomass burning to the PM 2.5 mass during the biomass burning (BB) event equaled 63.8%.

This paper derives the distribution of peatland in Europe as the extent of peat and peat-topped soils indicated by soil databases. The data sources were the 1:1,000,000 European Soil Database (v1.0) and a data set of organic carbon content (%) for the topsoils of Europe at 1km x 1km resolution that was recently published in map form. The strong influences of vegetation and land use on soil organic carbon (OC) content were taken into account in computing the 1km (OC) data set, as was the influence of temperature. The areas of peat and peat-topped soils estimated from the European Soil Database are generally in close agreement with those obtained using the Map of OC in Topsoils of Europe. The results reveal a strong northern bias in the distribution of organic soils across Europe. Almost one-third of the peatland resource of Europe is in Finland, and more than a quarter is in Sweden. The remainder is in Poland, the UK,

In order to classify the trophic state of detritus sink systems, instead of the conventional indicators based on inorganic nutrient availability and algal biomass and productivity in the water column, we used new biochemical descriptors based on the amount of sedimentary organic carbon (C) and nitrogen (N) potentially available to hetero-trophs. We investigated spatial and temporal changes in microphytobenthic biomass, organic matter biochemical com-position, and enzymatically hydrolyzable protein and carbohydrate pools along a northsouth transect in the Marsala lagoon (Mediterranean Sea, Italy) at three stations characterized by different hydrodynamic conditions and organic matter content in the sediment. In the Marsala lagoon water currents decreased from north to south and this pattern was reflected by organic matter distribution and composition. Sediment organic matter concentrations were among the highest reported in the literature and, in the central area where large meadows of the seagrass Posidonia oceanica were present, display a strong dominance of highly refractory carbohydrates. The protein to carbohydrate ratio was always , 1, indi-cating the dominance of aged organic detritus. Microphytobenthic biomass displays an increasing pattern southward, and its contribution to the biopolymeric C pools ranged from negligible in the central sector of the lagoon to 50% in its northern part, indicating that sources of sediment organic C also changed along the hydrodynamic gradient. The per-centage contribution of the enzymatically hydrolyzable fraction of proteins and carbohydrates was inversely related to total protein and total carbohydrate concentrations, respectively, suggesting that bioavailability of organic C and N in-creased with decreasing organic matter content in the sediment and with increasing hydrodynamic regime. Microphyto-benthic contribution to biopolymeric C (as a proxy of autotrophic organic C) and the ratio of the enzymatically digestible fraction to biopolymeric C (as an indicator of organic matter liability) were significantly correlated, suggesting that chlorophyll a sediment content might be used as an indicator of food promptly available to consumers. The present study also highlighted that the ratio of labile (i.e., enzymatically digestible) versus biopolymeric organic C in the sediments tends to decrease with increasing organic matter content, due to the increase of the refractory fraction of organic C.

Changes in oceanic primary production, linked to changes in the network of global biogeochemical cycles, have profoundly influenced the geochemistry of Earth for over 3 billion years. In the contemporary ocean, photosynthetic carbon fixation by marine phytoplankton leads to formation of ϳ45 gigatons of organic carbon per annum, of which 16 gigatons are exported to the ocean interior. Changes in the magnitude of total and export production can strongly influence atmospheric CO 2 levels (and hence climate) on geological time scales, as well as set upper bounds for sustainable fisheries harvest. The two fluxes are critically dependent on geophysical processes that determine mixed-layer depth, nutrient fluxes to and within the ocean, and food-web structure. Because the average turnover time of phytoplankton carbon in the ocean is on the order of a week or less, total and export production are extremely sensitive to external forcing and consequently are seldom in steady state. Elucidating the biogeochemical controls and feedbacks on primary production is essential to understanding how oceanic biota responded to and affected natural climatic variability in the geological past, and will respond to anthropogenically influenced changes in coming decades. One of the most crucial feedbacks results from changes in radiative forcing on the hydrological cycle, which influences the aeolian iron flux and, in turn, affects nitrogen fixation and primary production in the oceans. P. G.

Both visible near-infrared (VNIR) and mid-infrared (MIR) spectroscopy have been claimed to better predict pesticide sorption in soils than other methods. We compared the performances of VNIR and MIR spectroscopy for predicting both organic carbon content (f OC ) and the sorption affinity (K d ) of diuron in 112 surface soils from South Australia. Separate calibration models were developed between VNIR and MIR spectra, and f OC and K d using partial least-squares (PLS) regression. MIR clearly outperformed VNIR for predictions of both f OC and K d in soils. Correlation (R 2 ) and accuracy (RPD) indices were 0.4 and 1.3 for the VNIR-PLS model versus 0.8 and 2.3 for the MIR-PLS model, respectively, for K d prediction. PLS loadings for sorption prediction were compared in terms of the soil information they contained. While VNIR loading did not include any direct spectral information regarding soil minerals, MIR loading included peaks associated with sand, clays, and carbonates. Perhaps by better predicting f OC and integrating the effects of OC as well as minerals, the MIR-PLS model provided a better prediction for diuron K d values in our calibration set.

Soil tensile strength (TS) and aggregate stability (AS) values can be used as indicators of soil structural quality. The objective of this study was to determine the influences of land use types, soil carbon and clay contents on soil structure. Soil samples were collected from 51 different locations from the Kumkale Basin in Çanakkale in April and July 2003. A global positioning system (GPS) was used to determine the coordinates of sampling points. TS, AS, soil organic carbon (SOC), and clay contents were determined. Results of soil analysis and coordinates of sampling points were transferred to the Arc View geographical information systems (GIS) program. Multiple regression analysis showed that TS was positively related (r 2 = 0.89 and 0.92 in April and July, respectively) to clay content when SOC was high. The water stable aggregates in pasture soils were approximately 10 times more water stable than those in other agricultural soils in the region. In general, wet AS was more sensitive to cropping and management systems than TS. Soil AS rose with increasing soil SOC content while TS of soil aggregates was mostly influenced by clay content. However, the effect of clay content on aggregate TS rose with increasing SOC content.

}Ozonation is a disinfection technique commonly used in the treatment of drinking water. It destroys harmful microbes, but it also degrades organic matter in water, increasing the bioavailability of organic matter. Recently, it was found that not only organic carbon but also phosphorus can limit the microbial growth in drinking water, which contains high amount of organic matter. We used a bioassay to analyze whether ozone could also increase the microbially available phosphorus (MAP) in drinking water, and whether MAP in ozone-treated water was associated with the growth of heterotrophic microbes. We found that both assimilable organic carbon and MAP concentrations were increased by ozone treatment. In ozonated water, microbial growth was mainly limited by phosphorus, and even minor changes in MAP concentration dramatically increased the growth potential of heterotrophic microbes. In this study, ozonation increased the MAP by 0.08-0.73 mg P/l, resulting in an increase of 80,000-730,000 CFU/ml in water samples. In contrast to MAP, the content of assimilable organic carbon (AOC potential) did not correlate with microbial growth. The results show that in water treatment not only AOC potential but also MAP should be considered as an important factor that can limit microbial growth in drinking water.

Detailed d13C stratigraphies have been published recently for several Cenomanian-Turonian pelagic sections of southern England, and the Lower Saxony basin of Germany. The observed changes in the d13C record provide a useful tool for high-resolution stratigraphic correlation, and are used here to create a composite Cenomanian-Turonian d13C curve in a time-related framework. A best fit curve to 673 carbon isotope data is provided using the LOWESS regression scatterplot smoother. The long-term trend of the smoothed composite d13C profile varies on time scales of 106 years, and shows stable d13C values through the Lower Cenomanian, an increase in the Middle and Upper Cenomanian, with a major positive excursion around the Cenomanian-Turonian boundary, and a decrease through the Lower and Middle Turonian. Short-term fluctuations vary on time scales of 105 years, and dominated the d13C signal in the higher Middle and Upper Turonian. Changes of the Cenomanian-Turonian d13C record have commonly been explained by variations in the organic carbon flux to the sedimentary reservoir, in response to eustatic sea-level change. However, mass balance consideration suggests also an influence of carbonate production and burial rate on the d13C signal. Enhanced inorganic carbon burial increased the ratio of the inorganic to organic carbon fluxes and shifted the 13C/12C ratio to more negative values. This pattern may be observed in the Early and Middle Turonian d13C long-term record, and correlates with the spatial expansion of pelagic carbonate deposits in epicontinental seas. Short-term d13C variations could be either a directly response to short-term sea-level changes, reflecting local conditions in the European epicontinental sea, or could represent changes in oceanic 12C storage in response to the varying intensity of thermohaline circulation.

ÐSediment cores from Lake Biwa (Shiga Prefecture) and Lake Kizaki (Nagano Prefecture) provide evidence of variations in the climate of Japan subsequent to the end of the last glacial period. Concentrations of organic carbon increase in sediments deposited after the Pleistocene±Holocene boundary, as wetter climates washed in more soil nutrients and aquatic productivity increased. Organic matter C/N ratios simultaneously decrease, indicating smaller proportions of land-derived plant matter. Lake Biwa C/N ratios and organic carbon isotope ratios uctuate markedly between 10 and 4 Kya, suggesting that both delivery of land-derived organic matter and production of lake-derived organic matter were variable during this period of time. Similar variability in biotic paleoceanographic indicators has been reported in sediments from the Oki Ridge in the Japan Sea and has been interpreted to record early Holocene¯uctuations in the intensity of the Tsushima Current. Such¯uctuations in this warm-water current are likely to have caused concordant¯uctuations in climate on Honshu, a relationship that explains the variability in rainfall evident in the organic matter of the lake sediments.

The interaction of organic compounds with the mineral phase is considered as one stabilization mechanism for organic carbon (OC) in soils. The objective of this study is to assess the role of mineral surfaces for the long-term stabilization of OC in arable soils, with special emphasis on iron oxides. Soil samples were taken from two contrasting treatment types, i.e. fertilized plots and C-depleted plots, in long-term agroecosystem experiments. The soil organic carbon pool of the C-depleted plots is considered to show a lower contribution of labile compounds and consequently to be relatively enriched in refractory compounds compared with the fertilized counterparts. In fractions <6 μm, OC was studied in relation to total mineral surface area, surface area contributed by oxides and silicates, and the content and type of iron oxides (dithionite and oxalate extractable iron, Fed and Feo). In two sandy soils, OC contents were linearly related to total mineral surface area and the content of the two iron oxide fractions (Fed and Feo). The surface area developed by the silicates was low and thus the surface area contribution from oxides was dominant in fractions <6 μm. In contrast to the sandy soils, in a loamy soil OC was not correlated with surface area or the iron oxide content. However, the different soils agreed with respect to the behavior of C in density fractions: losses of OC occurred mainly from the light fraction (⩽2 g cm−3), whereas C in the heavy fraction (>2 g cm−3) proved to be stable. For the sandy soils, mineral surface area appears to control the storage of OC in fine fractions. Given the dominant surface area contribution from oxides, OC storage here primarily depends on the oxides. The C-depleted plots in particular show that surface area controls the accumulation of refractory C. The interaction of organic compounds with the mineral phase, mainly with the surface of oxides, seems to be a major mechanism for the long-term stabilization of OC in these sandy soils. An interaction with minerals seems to be important for stabilizing OC also in the loamy soil, although this is not reflected by a proportional relation between OC and surface area across the fractions.

Polycyclic aromatic hydrocarbon (PAH) concentrations in 34 surface sediments along the Susquehanna River were investigated in 2000. The total concentrations of PAHs in the surface sediments of Lake Clarke, Lake Aldred, the upper Conowingo Reservoir, and the lower Conowingo Reservoir were 3.3 ± 1.5 lg g À1 (n = 9), 1.6 ± 1.3 lg g À1 (n = 4), 9.8 ± 5.5 lg g À1 (n = 7), and 4.0 ± 1.2 lg g À1 (n = 14), respectively. These represent the first comprehensive measurement of PAHs in Susquehanna River surface sediments. Overall, total PAH concentrations were relatively lower in Lake Aldred, which is more shallow and sloped, and significantly higher in the upper Conowingo Reservoir. The sediment PAH levels were related to river flow rates, which are indirectly correlated with the particle size of the surface sediments. Total PAH levels in all the studied sites were below the effects range median (ERM) of 44.8 lg g À1 with 38% (13 of the 34 sampling sites) exceeding the effects range low (ERL) of 4.02 lg g À1 . Principal component analysis indicated that variations in the PAH compound patterns of each reservoir decreased from upstream to downstream, indicating that the surface sediments were mixed along the Susquehanna River. The PAH patterns in the lower Conowingo Reservoir sediments were a combination of those upstream sources. Source analysis using isomer ratios as indicators suggested that PAHs in the Susquehanna River surface sediment are derived from the combustion of fossil fuels such as coal and gasoline with coal as the major source of contaminants.

Status of organic carbon (C), total nitrogen (N), available potassium (K), calcium (Ca) and phosphorus (P) in three different depths (0−5 cm, 5−15 cm and 15−30 cm) on two hill slopes of 35% and 55% in orange orchard cultivated by the Mro tribe of Chittagong Hill Tracts (CHTs) were evaluated and compared with those in degraded bush forests, through digging three profiles in each land use. The content of all the five nutrients was found to be higher in the soil of orange orchard than in the soil of forest. But the variation was not consistent for both the slopes. The content varied depth wise also, having the highest value in surface soil in case of both the land uses on both the slopes. A mean available K content was significantly higher in orange orchard than in forest on 55% slope, while it was lower on 35% slope. Surface soil contained the nutrients of K and Ca with the amount of 0.2905-mg·g -1 soil and 3.025-mg·g -1 soil respectively in the orchard, while 0.1934-mg·g -1 soil and ...

This paper presents a case study on application of photosynthetic bacteria wastewater treatment system to recover organic carbon in wastewater in the form of photosynthetic bacterial cells. In noodle production process, the wastewater was mainly produced during rice soaking and rinsing processes containing starch as its main constituent. For carbon recovery purpose, wastewater was applied to laboratory photosynthetic wastewater treatment

Nutrient and organic carbon (OC) losses are important components of the soil degradation processes produced by continuous agriculture. It was hypothesized that coarse textured soils will be more affected by cultivation than fine textured ones. The purpose of this study was to evaluate the status of OC, total nitrogen (Nt), and three phosphorous fractions (total inorganic, Pi; organic, Po; and available, Pa) in different textured virgin (under Prosopis caldenia forest) and cultivated soils of the semi-arid pampa of Argentina. Three virgin and non-fertilized cultivated soil pairs, representative from soils of the region, were selected for this study: two fine sandy loam Entic Haplustolls and a sandy Typic Ustipsamment. The element content of each soil was analysed from the (0)1-mm to 0)1}2-mm sized aggregates. Results indicated that cultivation decreased the OC, Po and Pi contents in fine aggregates of the fine textured soils, and in coarse aggregates of the coarse textured soil. Plant absorption and wind erosion were probably the main processes which decreased element contents in both textural soil types. It was speculated that in the sandy soil the elements lost from fine sized aggregates were restored by the break down of the weak coarse aggregates produced by tillage. The C/N ratios showed mostly small changes due to cultivation, indicating that no changes of organic matter quality occurred. Only the sandy soil showed C/N increases in the fine sized aggregates and decreases in the coarse sized aggregates. The C/Po quotients were not changed by cultivation, indicating that the qualitative composition of P organic compounds remained unchanged. Large OC decreases and Pa increases after cultivation detected in one of the fine textured soil were apparently linked to the occurrence of natural fires.

Phytoplankton carbon and particulate organic carbon (POC), nitrogen (PON), and phosphorus (POP) (POC : PON : POP) were analyzed in 109 temperate lakes covering a wide span in productivity and other key parameters. Seasonal means of total POC (four samples) ranged from 206 to 7160 g C L Ϫ1 , with a grand mean of 960 g C L Ϫ1 , whereas estimated phytoplankton C ranged 12 to 1,770 g C L Ϫ1 , with a mean of 217 g C L Ϫ1 . Sestonic C : P ratios ranged from 59 to 553 (atom : atom), with a mean of 207. The elemental contributions from phytoplankton and other sestonic compartments (mainly detritus) were analyzed with a simple regression model, in which autochthonous and allochthonous components were separated. Model-derived estimates for N : P ratios of phytoplankton and allochthonous seston compartments were nearly equal (15.4 Ϯ 2.5 and 16.0 Ϯ 2.0) and were not significantly different from the Redfield N : P ratio (16). The estimated C : P ratio of allochthonous detritus was 2.7 times higher than that for phytoplankton (123 Ϯ 15), which again was not significantly different from the Redfield C : P ratio (106). Altogether, this indicates that sestonic components of autochthonous origin should be closer to Redfield proportions in eutrophic than in oligotrophic lakes. It also indicates that major contributions of allochthonous detrital C in oligotrophic lake seston may explain deviations from the Redfield ratio and calls for caution when interpreting elemental ratios in algae versus total seston. The regression model indicates that live phytoplankton cells rarely exceed 40% of total POC, yet it suggests that a major fraction of detritus is derived from autotrophs. This close link between live and dead cells could explain why total seston apparently carries the stoichiometric and biochemical footprints from the phytoplankton. Judged from algal biomass alone, Daphnia would face severe food limitation in a majority of lakes, while if we were to include total seston, Daphnia would be above threshold food levels in all lakes. Likewise, the effect of food quality limitation related to C : P ratios will turn out differently if total seston or only the phytoplankton fraction is considered.

1] Black carbon (BC), the product of incomplete combustion of fossil fuels and biomass (called elemental carbon (EC) in atmospheric sciences), was quantified in 12 different materials by 17 laboratories from different disciplines, using seven different methods. The materials were divided into three classes: (1) potentially interfering materials, (2) laboratory-produced BC-rich materials, and (3) BC-containing environmental matrices (from soil, water, sediment, and atmosphere). This is the first comprehensive intercomparison of this type (multimethod, multilab, and multisample), focusing mainly on methods used for soil and sediment BC studies. Results for the potentially interfering materials (which by definition contained no fire-derived organic carbon) highlighted situations where individual methods may overestimate BC concentrations. Results for the BC-rich materials (one soot and two chars) showed that some of the methods identified

Several management systems can improve soil productivity. By studying aggregate stability it is possible to quantify whether or not the management is ameliorating the natural soil properties and the land capability for agriculture. The effect of three tillage systems on the stability of soil aggregates and soil organic carbon was studied in comparison to reference plots with grass and bare soil. Samples were collected at the Pesagro Experimental Research Station in Paty do Alferes, state of Rio de Janeiro, Brazil, from an experiment that has been carried out from 1995 to 2001, on a Dystrophic Red Latosol (Typic Haplorthox). Aggregate size distribution mean weight diameter, geometric mean diameter of the aggregates, and total organic carbon in each aggregate size fraction were determined. The proportion of aggregates with diameter ≥2 mm appeared to be a suitable indicator of the influence of tillage systems on aggregation. At a depth of 0-5 cm, aggregates ≥2 mm were 50% of soil under no-tillage, which was greater than under animal traction (35%) and conventional tillage (30%). Total organic carbon concentration was greater under no-tillage (19 g kg −1 ) than under conventional tillage (11 g kg −1 ) at a depth of 0-5 cm, but not significantly different (average 13 g kg −1 ) at a depth of 5-10 cm. Soil exposure with tillage and lack of residue inputs caused declines in aggregation and organic carbon, both of which make soil susceptible to erosion. Adoption of no-tillage led to a decline in aggregation compared with grass reference, but did significantly alter soil organic concentration, suggesting it was a valuable conservation practice for vegetable production on sloping soils.

Soil organic carbon (OC) mobilization due to erosional processes can have consequences regarding CO2 emission or sequestration. OC can be mineralized (emitted as CO2 to the atmosphere) during detachment, transport and deposition of soil particles, or buried in depositional settings, where it can also be stabilized. The contradicting results in the published literature in the last decade point towards a lack of information concerning OC dynamics in relation to different erosion processes at different spatial scales. The objective of this work was to characterize the quantity and type of erosion OC mobilized by the different erosion processes identified at a catchment scale with respect to the original soils where they came from. With the purpose of analysing the type (labile or stable) and quantity of organic carbon (OC) mobilized by different erosive processes identified at the slope-bed connection, the erosion deposits of gullies, sheet erosion, bank erosion and tillage erosion wer...

Assessing the effects of air quality on public health and the environment requires reliable measurement of PM 2.5 mass and its chemical components. This study seeks to evaluate PM 2.5 measurements that are part of a newly established national network by comparing them with more versatile sampling systems. Experiments were carried out during 2002 at a suburban site in Maryland, United States, where two samplers from the US Environmental Protection Agency (US EPA) Speciation Trends Network: Met One Speciation Air Sampling System-STN S and Thermo Scientific Reference Ambient Air Sampler-STN R , two Desert Research Institute Sequential Filter Samplers-DRI F , and a continuous TEOM monitor (Thermo Scientific Tapered Element Oscillating Microbalance, 1400a) sampled air in parallel. These monitors differ not only in sampling configuration but also in protocol-specific laboratory analysis procedures. Measurements of PM 2.5 mass and major contributing species (i.e., sulfate, ammonium, organic carbon, and total carbon) were well correlated among the different methods with r-values 40.8. Despite the good correlations, daily concentrations of PM 2.5 mass and major contributing species were significantly different at the 95% confidence level from 5% to 100% of the time. Larger values of PM 2.5 mass and individual species were generally reported from STN R and STN S. These differences can only be partially accounted for by known random errors. Variations in flow design, face velocity, and sampling artifacts possibly influenced the measurement of PM 2.5 speciation and mass closure. Statistical tests indicate that the current uncertainty estimates used in the STN and DRI network may underestimate the actual uncertainty.

Micropaleontological and geochemical analyses were carried out on two sediment box cores (AH00-2220 and CR02-23) recovered in the Lower St. Lawrence Estuary (LSLE) in order to document recent temporal variations of primary productivity and carbon fluxes to the bottom waters. These reveal a tenfold increase in the accumulation rate of dinoflagellate cysts and benthic foraminifera in the sediment over the last four decades which can be interpreted as a recent increase in pelagic and benthic production. Furthermore, the appearance of the benthic foraminiferal species Brizalina subaenariensis and Bulimina exilis, which are tolerant of low oxygen concentrations and high organic fluxes, in the upper 20 cm of the cores, may reflect significant changes in bottom water conditions over the last 40 yrs. Variations in the microfossil abundances in core AH00-2220 are strongly correlated with an increase in organic carbon (OC) content (from 1.1 to 1.6%) and to a shift in the isotopic signature of the latter (δ 13 C ORG from −24.8 to − 24.0‰). Similarly, a concomitant decrease in the C ORG :N ratio (from 15 to 12), an increase in organic carbon content (from 1.3 to 1.9%) and an increase in δ 13 C ORG (from − 24.5 to − 23.5‰) were observed in core CR02-23, all of which suggest an enhanced accumulation of marine over terrestrial OC in the LSLE. Our results imply that a significant increase in marine productivity in the LSLE occurred since the 1960's.

refers to molecular-level characteristics such as elemental composition, functional groups, and molecular con-Formation of chemically resistant humic substances might be an formation that influence the inherent biodegradability important process controlling recycling of soil C to the atmosphere. of the molecule. Interactions refers to the intermolecular Humic substances are believed to be resistant to microbial decomposition because they accumulate in soil, but there is little direct experi-interactions with other inorganic or organic molecules mental evidence for their inherent recalcitrance. My objective was to that influence biodegradability-for example, complexcompare the microbial mineralization rates of the humic and fulvic ation with Al. Physical accessibility refers to the location acid fraction to other fractions of decayed plant matter in soil. Uniof the molecule with respect to enzymes or cells. For formly 14 C labeled Populus fremontii leaf litter that had decomposed example, substrates may be located in submicrometer for 180 d was fractionated into the NaOH-insoluble residue, phenolic, pores too small for microbial cells to enter (Sollins et humic acid, fulvic acid, hydrophilic acid, and hydrophilic neutral fracal., 1996). These conditions do not necessarily occur extions. Humic acid comprised 22.7% of the C in the decomposed litter.

Sediment traps were deployed on the Northwest Shelf (NWS) of Australia in November 1996, to determine fluxes of organic matter and inorganic elements from the photic zone to deeper waters in a transect extending from Exmouth Shelf to Exmouth Plateau. Infiltrex II water samplers collected particulate and dissolved organics from the water column near the trap sites. Surface sediments and sediment cores were also collected over the study region. Lipid biomarkers were used to determine the sources of organic carbon and its cycling processes on the NWS.Dry weight fluxes from the traps ranged from 124 to 616 mg m−2 day−1and particulate organic carbon (POC) fluxes ranged from 22 to 42 mg m−2 day−1. The biogenic lipids consisted of biomarkers indicative of marine zooplankton, phytoplankton and bacteria, plus traces of land plant markers. A large contribution of unresolved complex material (UCM), which is indicative of petroleum, was detected at four times the biogenic hydrocarbon flux at shallow stations, and up to seven times the biogenic hydrocarbon flux at the most offshore station.There is essentially no river input, and only trace aeolian-derived material to contribute to primary production on the NWS of Australia. Most of the organic matter produced are rapidly recycled in the water column and the small fraction of lipids that settle to the sediments is already partially degraded and undergoes further rapid degradation in the surface sediments. Natural oil seeps also provide utilisable organic carbon to the system. The production and vertical flux rates of organics determined in this study are comparable to those reported in studies of shallow traps in oceanic areas from long-term studies in the Arabian Sea, and other coastal margins such as the Bay of Biscay (France) and California (USA).In offshore areas, most “living” lipid materials passed through the GFF filters thus invalidating POC estimates based on high volume sampling. To adequately assess living (particulate) carbon, gentle filtration of low volume seawater samples is more accurate, as shown by this solid phase absorption study of individual lipid biomarkers.

Termites play an important role in decomposition processes in savanna and tropical forest ecosystems. In the process of mound building, termites modify the physical, chemical and biochemical characteristics of the soil they use for construction, as well as the soil of nearby areas, so that organic compounds, particularly C and N, and in some cases P, are more abundant in the termite nests than in the surrounding soils. In this study, organic matter and nutrient mineralization in incubation experiments were measured in mounds of Nasutitermes ephratae and associated soils of Orinoco savannas. The mounds of Nasutitermes ephratae contain more C, N and P than adjacent topsoils due to the use of faecal material to build gallery walls. Mounds accumulate 2.25 times more total P than adjacent soils. Available and potentially mineralizable organic P (Po) were signi®cantly higher in Nasutitermes mounds than in adjacent soils. The mound materials signi®cantly stimulated soil microbial metabolism, due to the accumulation of organic carbon (9.30%). The results for nitrogen dynamics emphasise the low ammoni-®cation rate in savanna soils. Ammonium production in the savanna soil was very low ranging from 20.4 to 39.9 mg g 21 , whereas in the mound the value increases to 1528 mg g 21 , which means that as much as 20% of the total nitrogen was found as inorganic nitrogen within the termitaria. Nitrate production on the other hand was negligible in both soils and mound, so that the nitri®cation rate seemed to be not limited by ammonium production. The nutrient depleted conditions of this environment together with the important concentrations of C, N and P found within the mounds of Nasusitermes ephratae corroborated the hypothesis that termite mounds can act as`sinks' in the nutrient economy of well-drained savannas with low productivity. q

The main aim of this study was to reconstruct the history of water level fluctuations of a small dimictic lake during the Holocene based on the lithological and geochemical composition of sediments. We studied lithological and geochemical parameters in sediment cores extracted along a transect through Lake Juusa in southeastern Estonia. Analysis revealed that LOI 550 and CaCO 3 content in the accumulated sediment are dependent on water depth. At depths greater than 3 m, the relationship between organic carbon and CaCO 3 is inverse, whereas no relationship exists at shallower depths. Lake-level changes are well depicted on the grain-size distribution profiles and macrofossil composition. An increase in the >315 lm fraction appeared during the initial phases of water level fluctuations, followed by an increase in the 100-315 lm fraction. The >36 lm fraction dominated the silt fraction. Higher OC/N ratios in shallow water sediments reflect the dominance of macrophytes vegetation.

The distribution of nepheloid layers across the outer shelf and upper continental slope off Namibia was studied during a cruise with R.V. Meteor in late austral summer 2003. Optical measurements, carried out with a transmissometer and a backscattering fluorometer, are correlated with suspended particulate matter (SPM) and particulate organic carbon (POC) values from water sample filtration. Conductivity-temperature-depth and oxygen data are used to relate the nepheloid layers to hydrographic structures. The particle content of surface water at the continental slope is controlled primarily by the offshore extension of highly productive upwelling filaments. A pronounced bottom nepheloid layer (BNL) covers the entire area of study with maximum intensity above the outer shelf and at the shelf break-an area where erosional forces dominate. The detachment of this BNL at the shelf break feeds a major intermediate nepheloid layer (INL) at 25.51S. This INL is positioned at 250-400 m depth, at the lower boundary of an oxygen minimum zone, and is likely connected to the poleward flow of South Atlantic Central Water (SACW) across the shelf break. Together, these strong subsurface nepheloid layers are indicators of intensive lateral particle transport from the outer shelf towards a depocenter of organic matter on the upper continental slope. r

With respect to carbon sequestration in soil, attempts have been made to identify soil organic matter (SOM) fractions that respond more rapidly to changes in land-use than bulk SOM, which could thus serve as early indicators for the overall stock change. We used a combination of physical fractionation (size and density separation) and chemical characterisation (C-to-N ratios, CuO lignin signature, 13 C NMR spectroscopy) to identify sensitive SOM fractions in an agricultural system with sandy dystric cambisols in Bavaria, Germany, 7 years after a land-use change. Land-use types included long-term arable land and grassland, and conversion from one system to the other. Soil carbon and nitrogen contents in 0 -3 cm increased from 14 to 39 mg organic carbon g À 1 soil, and from 1.7 to 3.9 mg nitrogen g À 1 soil in the following order: permanent arable, conversion grassland to arable, conversion arable to grassland, and permanent grassland. Wet sieving and ultrasonic dispersion with 22 J ml À 1 released < 5% and 60% to 80%, respectively, of the amount of particles >20 Am relative to complete dispersion. The most sensitive fraction, with respect to land-use, was SOM in the fraction >20 Am not released after sequential wet sieving and ultrasonic dispersion. In contrast, the proportion of free light (wet sieving, density < 1.8 g cm À 3 ) and occluded light (ultrasonic dispersion with 22 J ml À 1 , < 1.8 g cm À 3 ) particulate organic matter (POM) showed no clear response to land-use. The structural composition of POM indicated its vegetation origin with a selective enrichment of lignin and a loss of O-alkyl C relative to its plant precursors. Decomposition of the occluded light POM was only slightly advanced relative to the free light POM. In mineral fractions < 20 Am, SOM was significantly more transformed than in the coarse fractions, as shown by NMR spectroscopy; however, it revealed no specific land-use pattern. An exception to this was the proportion of O-alkyl C in the clay fraction, which increased with SOC content. Ratios of alkyl to O-alkyl C in mineral fractions < 20 Am differentiated samples gave a better differentiation of samples than the C-to-N ratios. We conclude that neither free nor occluded light POM are appropriate early indicators for changes in land-use at the investigated sites; however, total SOM, its distribution with depth, and SOM allocated in stable aggregates >20 Am were more sensitive. D

To examine the applicability of C/N and organic carbon stable isotope (δ 13 C) in studies of the Holocene sea level and freshwater discharge in the large river mouth of Yangtze, we observed the distribution of carbon, nitrogen and δ 13 C in a late-Quaternary core (ZK9) collected from the present subaqueous delta. We also collected published data of the two proxies for the suspended particulate matter (SPM) and surficial sediments from the lower Yangtze River to the adjacent East China Sea. The results show that the estuarine front is an important boundary for terrestrial and marine contribution of the organic component in the modern sedimentary environment. In the core ZK9, sediments deposited during c. 13-9 cal. ka BP are characterized by high values of TOC (0.54-1.16%), CaCO 3 (0.35% on average), and C/N (>12), which reflect an inner tidal estuarine environment dominated by C3 terrestrial organic carbon input. During c. 9-0.7 cal. ka BP, both TOC content (0.57% on average) and C/N ratio (<10) decrease remarkably while TN increases, indicating a lower estuarine or shallow marine environment. An abrupt sea level rise from c. 9 cal. ka BP resulted in a deeper water environment and reduced terrestrial input at the core location. The low δ 13 C values (−24.23‰ on average) before c. 6 cal. ka BP reflect a dominantly terrestrial source of organic matter associated with increased freshwater discharge into the estuary during that time. The sediments since c. 6 cal. ka BP are characterized by increasing δ 13 C up to −24.1 to −23.39‰, reflecting more contribution from marine algae as freshwater discharge fell. We suggest that in the Yangtze River mouth the C/N ratio indicates an abrupt sea level rise at c. 9 cal. ka BP, while δ 13 C is more useful in reflecting freshwater discharge.

Over half of the world's peat originated from Sphagnum, representing 10-15% of the terrestrial carbon stock. However, information regarding the release and exudation of organic carbon by living Sphagnum plants into the surface peat is scarce. In this study, we examined the contribution of recent Sphagnum subnitens (Russ. and Warnst.) photosynthate carbon to the peatland dissolved organic carbon (DOC) pool. This was done using a 13 CO 2 pulsechase experimental approach during the growing season. Despite the importance of Sphagnum in long-term carbon accumulation, results showed that the Sphagnum community rapidly contributes recently synthesized carbon to the peatland DOC pool. We estimate that by 4 h up to 4% of the total DOC in peat leachate was derived from 13 CO 2 pulse labelling at ambient CO 2 concentrations. Nonetheless, a huge 64% of the 13 C initially assimilated by photosynthesis was retained in Sphagnum subnitens for 23 days after labelling, consistent with the role of Sphagnum in peatland carbon accumulation. The majority of 13 C loss as respired CO 2 came within the few days post 13 CO 2 labelling, suggesting that it was derived from plant respiration of photosynthates.

Geochemical analyses as well as X ray diffraction measurements were carried out on five sediment cores from the eastern Angola Basin and the equatorial divergence of the South Atlantic. Barite concentrations were calculated from total barium concentrations by subtracting the estimated barium background supplied by "nonbarite" barium carders. Barite concentrations assessed by this geochemical method show a good correspondence to barite concentrations determined by quantitative X ray diffraction measurements. Barite proved to be an important carrier of barium in the pelagic cores, contributing up to 90% of the total barium concentrations in the sediment, while clastic material provides an important source of barium at sites closer to the African continent. Barite accumulation rates were calculated in order to eliminate the diluting effects of varying inputs of terdgenous and biogenic material. Barite accumulation rates show cyclic variations with maxima corresponding to glacial and minima to interglacial stages. Absolute paleoproduction rates were computed from barite accumulation rates. At the Congo fan and the equatorial divergence they are consistent with calculations based on total organic carbon (TOC) accumulation. At the Walvis Ridge, glacial-interglacial cycles contrast to a constant paleoproductivity computed from TOC accumulation. GINGELE AND DAHMKE: BARIUM IN SOUTH ATLANTIC SEDIMENTS combination of geochemical and mineralogical methods. The variations in the accumulation of discrete barite particles, representing relative changes in paleoproductivity, can thus be determined for sedimentary environments with highly varying inputs of terrigenous and biogenic sediment constituents. Absolute paleoproductivity rates are computed from barium accumulation rates with algorithms defined by Dymond et al. [1992] and compared to paleoproductivity calculations of the same sites based on isotopic and geochemical methods [Schneider, 1991; Bickert, 1992]. Material, Methods, and Procedures Five gravity cores were taken during Meteor cruises M6-6 [Wefer et al., 1988] and M9-4 [Wefer et al., 1989] in the Angola Basin and the Brazil Basin and on the Walvis Ridge. Undisturbed surface samples were obtained from box cores taken at the same locations and for six additional sites at different water depths (Figure 1 and Table 1). Cores from the equatorial divergence (GeoB 1041 and GeoB 1117) and the Walvis Ridge (GeoB 1035) consisted mainly of carbonate sands and oozes with minor amounts of opal and clastic material, while the cores from the African continental margin were dominated by fine-grained, diatom-bearing terrigenous muds (Congo fan, GeoB 1008) or silty clays (Angola slope, GeoB 1023) (Figure 2). 40øW 2(YW 0 ø I I i