Dissolved carbon in an urban area of a river in the Brazilian Amazon

The main objective of this study was to evaluate dissolved organic and inorganic carbon dynamics along upstream and downstream reaches of the Acre River draining the city of Rio Branco, in the state of Acre, Brazil. Dissolved organic carbon (DOC) concentrations in the Acre River were significantly higher during the wet season, ranging from 385 +/- A 160 to 430 +/- A 131 mu M among the stations, with no difference in upstream and downstream concentrations. Dissolved inorganic carbon (DIC) showed an inverse pattern, with higher concentrations in the dry season, ranging from 816 +/- A 215 to 998 +/- A 754 mu M among the stations, as well as no difference in upstream and downstream DIC concentrations. Bicarbonate was the dominant DIC fraction and was mainly observed during the dry season. Due to lower pH values during the wet season, CO(2) partial pressure (pCO(2)) in the Acre River was higher in the wet season, with values ranging from 4,567 +/- A 1,813 to 4,893 +/- A 837 ppm among the stations. Our results indicate that, although the Acre River drains a large city with significant sewage disposal into the river, seasonal hydrological processes are the main driver of dissolved carbon dynamics, even in the downstream study reach directly influenced by urbanization.

Reduction of Chromium from Al(2)O(3)-CaO-SiO(2)-CrOx Slags by Carbon Dissolved in Liquid Iron

The goal of this work is to investigate the reduction of chromium from a quaternary slag by carbon dissolved in liquid steel. Laboratory scale experiments were conducted to study the reduction of chromium oxides in the slag by carbon dissolved in the melt. These experiments were made under different conditions of slag basicity and amount of added carbon. Thermodynamic calculations based on Double Sublattice model were applied using the commercial software Thermo-Calc, with the IRSID database. The results obtained showed good correlation with practical and calculated results, making it possible to predict equilibrium conditions of the system and to determine the activities of chromium oxides in the slag.

Availability of two forms of dissolved nitrogen to the coral Pocillopora damicornis and its symbiotic zooxanthellae

The relative contribution of dissolved nitrogen (ammonium and dissolved free amino acids DFAAs) to the nitrogen budget of the reef-building coral Pocillopora damicornis was assessed for colonies growing on control and ammonium-enriched reefs at One Tree Island (southern Great Barrier Reef) during the ENCORE (Enrichment of Nutrient on Coral Reef; 1993 to 1996) project. P. damicornis acquired ammonium at rates of between 5.1 and 91.8 nmol N cm(-2) h(-1) which were not affected by nutrient treatment except in the case of one morph. In this case, uptake rates decreased from 80.5 to 42.8 nmol cm(-2) h(-1) (P < 0.05) on exposure to elevated ammonium over 12 mo. The presence or absence of light during measurement did not influence the uptake of ammonium ions. Nitrogen budgets revealed that the uptake of ammonium from concentrations of 0.11 to 0.13 mu M could completely satisfy the demand of growing P. damicornis for new nitrogen. P. damicornis also took up DFAAs at rates ranging from 4.9 to 9.8 nmol N cm(-2) h(-1). These rates were higher in the dark than in the light (9.0 vs 5.1 nmol m(-2) h(-1), P < 0.001). Uptake rates were highest for the amino acids serine, arginine and alanine, and lowest for tyrosine. DFAA concentrations within the ENCORE microatolls that received ammonium were undetectable, whereas they ranged up to 100 nM within the control microatolls. The contribution of DFAAs to the nitrogen budget of P. damicornis constituted only a small fraction of the nitrogen potentially contributed by ammonium under field conditions. Even at the highest field concentrations measured during this study, DFAAs could contribute only similar or equal to 11.3% of the nitrogen demand of P. damicornis. This contribution, however, may be an important source of nitrogen when other sources such as ammonium are scarce or during periods when high concentrations of DFAAs become sporadically available (e.g. cell breakage during fish-grazing).

Net uptake of dissolved free amino acids by the giant clam, Tridacna maxima: alternative sources of energy and nitrogen?

The role of dissolved free amino acids (DFAA) in nitrogen and energy budgets was investigated for the giant clam, Tridacna maxima, growing under field conditions at One Tree Island, at the southern end of the Great Barrier Reef, Australia. Giant clams (121.5-143.7 mm in shell length) took up neutral, acidic and basic amino acids. The rates of net uptake of DFAA did not differ between light and dark, nor for clams growing under normal or slightly enriched ammonium concentrations. Calculations based on the net uptake concentrations typical of the maximum concentrations of DFAA found in coral reef waters (similar to 0.1 mu M)revealed that DFAA could only contribute 0.1% and 1% of the energy and nitrogen demands of giant clams, respectively. These results suggest that DFAA does not supply significant amounts of energy or nitrogen for giant clams or their symbionts.

Dissolved organic carbon in rainwater from areas heavily impacted by sugar cane burning

This work reports on rainwater dissolved organic carbon (DOC) from Ribeirao Preto (RP) and Araraquara over a period of 3 years. The economies of these two cities, located in Sao Paulo state (Brazil), are based on agriculture and related industries, and the region is strongly impacted by the burning of sugar cane foliage before harvesting. Highest DOC concentrations were obtained when air masses traversed sugar cane fields burned on the same day as the rain event. Significant increases in the DOC volume weighted means (VWM) during the harvest period, for both sites, and a good linear correlation (r=0.83) between DOC and K (a biomass burning marker) suggest that regional scale organic carbon emissions prevail over long-range transport. The DOC VWMs and standard deviations were 272 +/- 22 mu mol L-1 (n=193) and 338 +/- 40 mu mol L-1 (n=80) for RP and Araraquara, respectively, values which are at least two times higher than those reported for other regions influenced by biomass burning, such as the Amazon. These high DOC levels are discussed in terms of agricultural activities, particularly the large usage of biogenic fuels in Brazil, as well as the analytical method used in this work, which includes volatile organic carbon when reporting DOC values. Taking into account rainfall volume, estimated annual rainwater DOC fluxes for RP (4.8 g C m(-2) yr(-1)) and Araraquara (5.4 g C m(-2) yr(-1)) were close to that previously found for the Amazon region (4.8 g C m(-2) yr(-1)). This work also discusses whether previous calculations of the global rainwater carbon flux may have been underestimated, since they did not consider large inputs from biomass combustion sources, and suffered from a possible analytical bias. (c) 2008 Elsevier Ltd. All rights reserved.

Effect of soil composition and dissolved organic matter on pesticide sorption

The effect of the solid and dissolved organic matter fractions, mineral composition and ionic strength of the soil solution on the sorption behaviour of pesticides were studied. A number of soils, chosen so as to have different clay mineral and organic carbon content, were used to study the sorption of the pesticides atrazine (6-chloro-N-2-ethyl-N-4-isopropyl-1,3,5-triazine-2,4-diamine), 2,4-D ((2,4-dichlorophenoxy) acetic acid), isoproturon (3-(4-isopropylphenyl)1,1-dimethylurea) and paraquat (1,1'-dimethyl-4,4'-bipyridinium) in the presence of low and high levels of dissolved organic carbon and different background electrolytes. The sorption behaviour of atrazine, isoproturon and paraquat was dominated by the solid state soil components and the presence of dissolved organic matter had little effect. The sorption of 2,4-D was slightly affected by the soluble organic matter in the soil. However, this effect may be due to competition for adsorption sites between the pesticide and the soluble organic matter rather than due to a positive interaction between the pesticide and the soluble fraction of soil organic matter. It is concluded that the major factor governing the sorption of these pesticides is the solid state organic fraction with the clay mineral content also making a significant contribution. The dissolved organic carbon fraction of the total organic carbon in the soil and the ionic strength of the soil solution appear to have little or no effect on the sorption/transport characteristics of these pesticides over the range of concentrations studied. (C) 2002 Elsevier Science B.V. All rights reserved.

Dissolved organic nitrogen behaviour during denitrification with suspended and attached biomass

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente, perfil Engenharia Sanitária

Spatial-temporal variation of dissolved inorganic material in the Amazon basin

The Amazon River basin is important in the contribution of dissolved material to oceans (4% worldwide). The aim of this work was to study the spatial and the temporal variability of dissolved inorganic materials in the main rivers of the Amazon basin. Data from 2003 to 2011 from six gauging stations of the ORE-HYBAM localized in Solimões, Purus, Madeira and Amazon rivers were used for this study. The concentrations of Ca2+, Na+, K+, Mg2+, Cl-, SO4 -2, HCO3 - and SiO2 were analyzed. At the stations of Solimões and Amazon rivers, the concentrations of Ca2+, Mg2+, HCO3 - and SO4 -2 had heterogeneous distribution over the years and did not show seasonality. At the stations of Madeira river, the concentration of these ions had seasonality inversely proportional to water discharge (dilution-concentration effect). Similar behavior was observed for the concentrations of Cl- and Na+ at the stations of the Solimões, Amazon and Madeira rivers, indicating almost constant release of Cl- and Na+ fluxes during the hydrological cycle. K+ and SiO2 showed almost constant concentrations throughout the years and all the stations, indicating that their flows depend on the river discharge variation. Therefore, the temporal variability of the dissolved inorganic material fluxes in the Solimões and Amazon rivers depends on the hydro-climatic factor and on the heterogeneity of the sources. In the Madeira and Purus rivers there is less influence of these factors, indicating that dissolved load fluxes are mainly associated to silicates weathering. As the Solimões basin contributes approximately 84% of the total flux of dissolved materials in the basin and is mainly under the influence of a hydro-climatic factor, we conclude that the temporal variability of this factor controls the temporal variability of the dissolved material fluxes of the Amazon basin.

Anatomy of contaminated aquifers of an industrial site: insights from the stable isotope compositions of waters and dissolved inorganic carbon

The hydrogen and oxygen isotopes of water and the carbon isotope composition of dissolved inorganic carbon (DIC) from different aquifers at an industrial site, highly contaminated by organic pollutants representing residues of the former gas production, have been used as natural tracers to characterize the hydrologic system. On the basis of their stable isotope compositions as well as the seasonal variations, different groups of waters (precipitation, surface waters, groundwaters and mineral waters) as well as seasonably variable processes of mixing between these waters can clearly be distinguished. In addition, reservoir effects and infiltration rates can be estimated. In the northern part of the site an influence of uprising mineral waters within the Quaternary aquifers, presumably along a fault zone, can be recognized. Marginal infiltration from the Neckar River in the cast and surface water infiltration adjacent to a steep hill on the western edge of the site with an infiltration rate of about one month can also be resolved through the seasonal variation. Quaternary aquifers closer to the centre of the site show no seasonal variations, except for one borehole close to a former mill channel and another borehole adjacent to a rain water channel. Distinct carbon isotope compositions and concentrations of DIC for these different groups of waters reflect variable influence of different components of the natural carbon cycle: dissolution of marine carbonates in the mineral waters, biogenic, soil-derived CO2 in ground- and surface waters, as well as additional influence of atmospheric CO2 for the surface waters. Many Quaternary aquifer waters have, however, distinctly lower delta(13)C(DIC) values and higher DIC concentrations compared to those expected for natural waters. Given the location of contaminated groundwaters at this site but also in the industrially well-developed valley outside of this site, the most likely source for the low C-13(DIC) values is a biodegradation of anthropogenic organic substances, in particular the tar oils at the site.

Non-invasive detection of cocaine dissolved in wine bottles by (1) H magnetic resonance spectroscopy.

Recently, a number of cases of smuggling dissolved cocaine in wine bottles have been reported. The aim of the present study was to determine whether cocaine dissolved in wine can be detected by proton magnetic resonance spectroscopy ((1) H MRS) on a standard clinical MR scanner, in intact (i.e. unopened) wine bottles. (1) H MRS experiments were performed with a 3 Tesla clinical scanner on wine phantoms with or without cocaine contamination. The aromatic protons of cocaine displayed resonance peaks in the 7-8 ppm region of the spectrum, where no overlapping resonances of wine were present. Additional cocaine resonances were detected in the 2-3 ppm region of the spectrum, between the resonances of ethanol and other wine constituents. Detection of cocaine in wine (at 5 mM, i.e. ∼1.5 g/L) was feasible in a scan time of 1 min. We conclude that dissolved cocaine can be detected in intact wine bottles, on a standard clinical MR scanner. Thus, (1) H MRS is the technique of choice to examine this type of suspicious cargo, since it allows for a non-destructive and rapid content characterization. Copyright © 2010 John Wiley & Sons, Ltd.

Hydrogen sulfide measurement by headspace-gas chromatography-mass spectrometry (HS-GC-MS): application to gaseous samples and gas dissolved in muscle.

The aim of our study was to present a new headspace-gas chromatography-mass spectrometry (HS-GC-MS) method applicable to the routine determination of hydrogen sulfide (H(2)S) concentrations in biological and gaseous samples. The primary analytical drawback of the GC/MS methods for H(2)S measurement discussed in the literature was the absence of a specific H(2)S internal standard required to perform quantification. Although a deuterated hydrogen sulfide (D(2)S) standard is currently available, this standard is not often used because this standard is expensive and is only available in the gas phase. As an alternative approach, D(2)S can be generated in situ by reacting deuterated chloride with sodium sulfide; however, this technique can lead to low recovery yield and potential isotopic fractionation. Therefore, N(2)O was chosen for use as an internal standard. This method allows precise measurements of H(2)S concentrations in biological and gaseous samples. Therefore, a full validation using accuracy profile based on the β-expectation tolerance interval is presented. Finally, this method was applied to quantify H(2)S in an actual case of H(2)S fatal intoxication.

Radiological detection of dissolved cocaine

Introduction: Smuggling dissolved drugs, especially cocaine, in bottled liquids is a problem at borders nowadays. Common fluoroscopy of packages at the border cannot detect contaminated liquids. To find a dissolved drug, an immunological test using a drug-test panel has to be performed. This means that a control sample of the cargo must be opened to perform the test. As it is not possible to open all boxes, and as smugglers hide the drugcontaining boxes between regularly filled boxes, contaminated cargos can be overlooked. Investigators sometimes cannot perform the drug-test panel because they try not to arouse the smugglers' suspicion in order to follow the cargo and to find the recipient. Aims: The objective of our studies was to define non-invasive examination techniques to investigate cargos that are suspicions to contain dissolved cocaine without leaving traces on the samples. We examined vessels containing cocaine by radiological cross-section techniques such as multidetector computed tomography (MDCT) and magnetic resonance spectroscopy (MRS). Methods: In a previous study, we examined bottles of wine containing dissolved cocaine in different quantities using an MDCT unit. To distinguish between bottles containing red wine and those where cocaine was solved in the wine, cross sectional 2D-images have been reconstructed and the absorption of X-rays was quantified by measuring the mean density of the liquid inside the bottles. In our new study, we investigated phantoms containing cocaine dissolved in water with or without ethanol as well as cocaine dissolved in different sorts of commercially available wine by the use of a clinical magnetic resonance unit (3 tesla). To find out if dissolved cocaine could be detected, magnetic resonance spectroscopy (1H MRS) was performed. Results: By using a MDCT-unit and measuring the mean attenuation of X-rays, it is possible to distinguish weather substances are dissolved in a liquid or not, if a comparative liquid without any solutions is available. The increase of the mean density indicates the presence of dissolved substances without the possibility to identify the substance. By using magnetic resonance spectroscopy, dissolved cocaine can be clearly identified because it produces distinctive resonances in the spectrum. In contrast to MDCT, this technique shows a high sensitivity (detection of 1 mM cocaine in wine). Conclusions: Cross-sectional imaging techniques such as MDCT and MRS appropriated to examine cargos that are suspicious to contain dissolved cocaine. They allow to perform non-invasive investigations without leaving any trace on the cargo. While an MDCT scan can detect dissolved substances in liquids, identification of cocaine can be obtained by MR-spectroscopy. Acknowledgment: This work was supported by the Centre d'Imagerie BioMédicale (CIBM) of the University of Lausanne (UNIL), the Swiss Federal Institute of Technology Lausanne (EPFL), the University of Geneva (UniGe), the Centre Hospitalier Universitaire Vaudois (CHUV), the Hôpitaux Universitaire de Genève (HUG) and the Leenaards and the Jeantet Foundations.

Export of dissolved organic carbon, nitrogen and phosphorus following clear-cutting of three Norway spruce forest growing on drained peatlands in southern Finland

Abstract

Migration of dissolved organic carbon in biochars and biochar-mineral complexes

The objective of this work was to determine the contribution of dissolved organic carbon (DOC) from a biochar mineral complex (BMC), so as to better understand the interactions between DOC, biochar, clay, and minerals during thermal treatment, and the effects of BMC on amended soils. The BMC was prepared by heating a mixture of a H3PO4-treated saligna biochar from Acacia saligna, clays, other minerals, and chicken manure. The BMC was applied to a sandy loam soil in Western Australia, where wheat was grown. Liquid chromatography-organic carbon detection (LC-OCD) tests were carried out on water extracts from the untreated biochar, the BMC, the BMC-amended soil, and on a control soil to measure the DOC concentration. LC-OCD tests provide a fingerprint of the DOC, which allows the fractions of DOC to be determined. Thermal processing enhanced the reaction of the A. saligna biochar with manure, clays and minerals, and affected the distribution of the DOC fractions. Notably, the process leads to immobilization of hydrophobic DOC and to an increase in the concentration of low-molecular-weight neutrals in the BMC. The application of the BMC to soil increases the DOC in the amended soil, especially the biopolymer fraction.

Tracing of the Rhône River, wastewater, and mixing within Lake Geneva : stable isotope compositions of water and dissolved inorganic carbon

This study presents an evaluation of the stable isotopic composition of water (hydrogen and oxygen) and dissolved inorganic carbon (DIC) of Lake Geneva, a deep, peri-alpine lake situated at the border between Switzerland and France. The research goal is to apply vertical and seasonal variations of the isotope compositions to evaluate mixing processes of pollutants, nutrients and oxygen. Depth profiles were sampled at different locations throughout Lake Geneva on a monthly and seasonal basis over the course of three years (2009-2011). The results of the oxygen isotopic composition indicate a Rhône River interflow, which can be traced for about 55 km throughout the lake during summer. The Rhône River interflow is 7 to 15 m thick and the molar fraction of Rhône water is estimated to amount up to 37 %. Calculated density of the water and measured isotopic compositions demonstrate that the interflow depth changes in conjunction with the density gradient in the water column during fall. Partial pressure of CO2 indicates that the epilimnion is taking up CO2 from the atmosphere between spring and fall. The epilimnion is most enriched in 13CDIC in September and a progressive depletion of 13CDIC can be observed in the metalimnion from spring to late fall. This stratification is dependent on the local density stratification and the results demonstrate that parameters, which are indicating photosynthesis, are not necessarily linked to δ13CDIC values. In addition, the amount of primary production shows a strong discrepancy between summer 2009 and 2010, but δ13CDIC values of the epilimnion and metalimnion do not indicate variations. In the hypolimnion of the deep lake δ13CDIC values are constant and the progressive depletion allows tracing remineralization processes. The combination of stable carbon and oxygen isotopic compositions allows furthermore tracing Rhône River water fractions, as well as wastewater, stormwater and anthropogenic induced carbon in the water column of the shallow Bay of Vidy. In combination with the results of measured micropollutants, the study underlines that concentrations of certain substances may be related to the Rhône River interflow and/or remineralization of particulate organic carbon. Water quality monitoring and research should therefore be extended to the metalimnion as well as sediment water interface.