Carbonate Chemistry and the Potential for Acidification in Georgia Coastal Marshes and the South Atlantic Bight, USA.

In coastal regions and marginal bodies of water, the increase in partial pressure of carbon dioxide (pCO2) in many instances is greater than that of the open ocean due to terrestrial (river, estuarine, and wetland) influences, decreasing buffering capacity and/or increasing water temperatures. Coastal oceans receive freshwater from rivers and groundwater as well as terrestrial-derived organic matter, both of which have a direct influence on coastal carbonate chemistry. The objective of this research is to determine if coastal marshes in Georgia, USA, may be "hot-spots" for acidification due to enhanced inorganic carbon sources and if there is terrestrial influence on offshore acidification in the South Atlantic Bight (SAB). The results of this study show that dissolved inorganic carbon (DIC) and total alkalinity (TA) are elevated in the marshes compared to predictions from conservative mixing of the freshwater and oceanic end-members, with accompanying pH around 7.2 to 7.6 within the marshes and aragonite saturation states (ΩAr) <1. In the marshes, there is a strong relationship between the terrestrial/estuarine-derived organic and inorganic carbon and acidification. Comparisons of pH, TA, and DIC to terrestrial organic material markers, however, show that there is little influence of terrestrial-derived organic matter on shelf acidification during this period in 2014. In addition, ΩAr increases rapidly offshore, especially in drier months (July). River stream flow during 2014 was anomalously low compared to climatological means; therefore, offshore influences from terrestrial carbon could also be decreased. The SAB shelf may not be strongly influenced by terrestrial inputs to acidification during drier than normal periods; conversely, shelf waters that are well-buffered against acidification may not play a significant role in mitigating acidification within the Georgia marshes. Supplementary Information: The online version contains supplementary material available at 10.1007/s12237-023-01261-3.

Microbial succession and dynamics in meromictic Mono Lake, California.

Mono Lake is a closed-basin, hypersaline, alkaline lake located in Eastern Sierra Nevada, California, that is dominated by microbial life. This unique ecosystem offers a natural laboratory for probing microbial community responses to environmental change. In 2017, a heavy snowpack and subsequent runoff led Mono Lake to transition from annually mixed (monomictic) to indefinitely stratified (meromictic). We followed microbial succession during this limnological shift, establishing a two-year (2017-2018) water-column time series of geochemical and microbiological data. Following meromictic conditions, anoxia persisted below the chemocline and reduced compounds such as sulfide and ammonium increased in concentration from near 0 to ~400 and ~150 µM, respectively, throughout 2018. We observed significant microbial succession, with trends varying by water depth. In the epilimnion (above the chemocline), aerobic heterotrophs were displaced by phototrophic genera when a large bloom of cyanobacteria appeared in fall 2018. Bacteria in the hypolimnion (below the chemocline) had a delayed, but systematic, response reflecting colonization by sediment "seed bank" communities. Phototrophic sulfide-oxidizing bacteria appeared first in summer 2017, followed by microbes associated with anaerobic fermentation in spring 2018, and eventually sulfate-reducing taxa by fall 2018. This slow shift indicated that multi-year meromixis was required to establish a sulfate-reducing community in Mono Lake, although sulfide oxidizers thrive throughout mixing regimes. The abundant green alga Picocystis remained the dominant primary producer during the meromixis event, abundant throughout the water column including in the hypolimnion despite the absence of light and prevalence of sulfide. Our study adds to the growing literature describing microbial resistance and resilience during lake mixing events related to climatic events and environmental change.

Microbial Niche Diversification in the Galápagos Archipelago and Its Response to El Niño.

The Galápagos Archipelago is located at the intersection of several major oceanographic features that produce diverse environmental conditions around the islands, and thus has the potential to serve as a natural laboratory for discerning the underlying environmental factors that structure marine microbial communities. Here we used quantitative metagenomics to characterize microbial communities in relation to archipelago marine habitats, and how those populations shift due to substantial environmental changes brought on by El Niño. Environmental conditions such as temperature, salinity, inorganic dissolved nutrients, and dissolved organic carbon (DOC) concentrations varied throughout the archipelago, revealing a diversity of potential microbial niches arising from upwelling, oligotrophic to eutrophic gradients, physical isolation, and potential island mass effects. The volumetric abundances of microbial community members shifted with these environmental changes and revealed several taxonomic indicators of different water masses. This included a transition from a Synechococcus dominated system in the west to an even mix of Synechococcus and Prochlorococcus in the east, mirroring the archipelago's mesotrophic to oligotrophic and productivity gradients. Several flavobacteria groups displayed characteristic habitat distributions, including enrichment of Polaribacter and Tenacibaculum clades in the relatively nutrient rich western waters, Leeuwenhoekiella spp. that were enriched in the more nutrient-deplete central and eastern sites, and the streamlined MS024-2A group found to be abundant across all sites. During the 2015/16 El Niño event, both environmental conditions and microbial community composition were substantially altered, primarily on the western side of the archipelago due to the reduction of upwelling from the Equatorial Undercurrent. When the upwelling resumed, concentrations of inorganic nutrients and DOC at the western surface sites were more typical of mesopelagic depths. Correspondingly, Synechococcus abundances decreased by an order of magnitude, while groups associated with deeper water masses were enriched, including streamlined roseobacters HTCC2255 and HIMB11, Thioglobacaceae, methylotrophs (Methylophilaceae), archaea (Nitrosopumilaceae), and distinct subpopulations of Pelagibaceriales (SAR11 clade). These results provide a quantitative framework to connect community-wide microbial volumetric abundances to their environmental drivers, and thus incorporation into biogeochemical and ecological models.

Molecular composition and biodegradation of loggerhead sponge Spheciospongia vesparium exhalent dissolved organic matter.

Sponges are critical components of marine reefs due to their high filtering capacity, wide abundance, and alteration of biogeochemical cycling. Here, we characterized dissolved organic matter (DOM) composition in the sponge holobiont exhalent seawater of a loggerhead sponge (Spheciospongia vesparium) and in ambient seawater in Florida Bay (USA), as well as the microbial responses to each DOM pool through dark incubations. The sponge holobiont removed 6% of the seawater dissolved organic carbon (DOC), utilizing compounds that were low in carbon and oxygen, yet high in nitrogen content relative to the ambient seawater. The microbial community accessed 7% of DOC from the ambient seawater during a 5-day incubation but only 1% of DOC from the sponge exhalent seawater, suggesting a decrease in lability possibly due to holobiont removal of nitrogen-rich compounds. If this holds true for other sponges, it may have important implications for DOM lability and cycling in coastal environments.

Offshore transport of particulate organic carbon in the California Current System by mesoscale eddies.

The California Current System is characterized by upwelling and rich mesoscale eddy activity. Cyclonic eddies generally pinch off from meanders in the California Current, potentially trapping upwelled water along the coast and transporting it offshore. Here, we use satellite-derived measurements of particulate organic carbon (POC) as a tracer of coastal water to show that cyclones located offshore that were generated near the coast contain higher carbon concentrations in their interior than cyclones of the same amplitude generated offshore. This indicates that eddies are in fact trapping and transporting coastal water offshore, resulting in an offshore POC enrichment of 20.9 ± 11 Gg year-1. This POC enrichment due to the coastally-generated eddies extends for 1000 km from shore. This analysis provides large-scale observational-based evidence that eddies play a quantitatively important role in the offshore transport of coastal water, substantially widening the area influenced by highly productive upwelled waters in the California Current System.

Identifying labile DOM components in a coastal ocean through depleted bacterial transcripts and chemical signals.

Understanding which compounds comprising the complex and dynamic marine dissolved organic matter (DOM) pool are important in supporting heterotrophic bacterial production remains a major challenge. We eliminated sources of labile phytoplankton products, advected terrestrial material and photodegradation products to coastal microbial communities by enclosing water samples in situ for 24 h in the dark. Bacterial genes for which expression decreased between the beginning and end of the incubation and chemical formulae that were depleted over this same time frame were used as indicators of bioavailable compounds, an approach that avoids augmenting or modifying the natural DOM pool. Transport- and metabolism-related genes whose relative expression decreased implicated osmolytes, carboxylic acids, fatty acids, sugars and organic sulfur compounds as candidate bioreactive molecules. FT-ICR MS analysis of depleted molecular formulae implicated functional groups ~ 30-40 Da in size cleaved from semi-polar components of DOM as bioreactive components. Both gene expression and FT-ICR MS analyses indicated higher lability of compounds with sulfur and nitrogen heteroatoms. Untargeted methodologies able to integrate biological and chemical perspectives can be effective strategies for characterizing the labile microbial metabolites participating in carbon flux.

Bacterial Biogeography across the Amazon River-Ocean Continuum.

Spatial and temporal patterns in microbial biodiversity across the Amazon river-ocean continuum were investigated along ∼675 km of the lower Amazon River mainstem, in the Tapajós River tributary, and in the plume and coastal ocean during low and high river discharge using amplicon sequencing of 16S rRNA genes in whole water and size-fractionated samples (0.2-2.0 µm and >2.0 µm). River communities varied among tributaries, but mainstem communities were spatially homogeneous and tracked seasonal changes in river discharge and co-varying factors. Co-occurrence network analysis identified strongly interconnected river assemblages during high (May) and low (December) discharge periods, and weakly interconnected transitional assemblages in September, suggesting that this system supports two seasonal microbial communities linked to river discharge. In contrast, plume communities showed little seasonal differences and instead varied spatially tracking salinity. However, salinity explained only a small fraction of community variability, and plume communities in blooms of diatom-diazotroph assemblages were strikingly different than those in other high salinity plume samples. This suggests that while salinity physically structures plumes through buoyancy and mixing, the composition of plume-specific communities is controlled by other factors including nutrients, phytoplankton community composition, and dissolved organic matter chemistry. Co-occurrence networks identified interconnected assemblages associated with the highly productive low salinity near-shore region, diatom-diazotroph blooms, and the plume edge region, and weakly interconnected assemblages in high salinity regions. This suggests that the plume supports a transitional community influenced by immigration of ocean bacteria from the plume edge, and by species sorting as these communities adapt to local environmental conditions. Few studies have explored patterns of microbial diversity in tropical rivers and coastal oceans. Comparison of Amazon continuum microbial communities to those from temperate and arctic systems suggest that river discharge and salinity are master variables structuring a range of environmental conditions that control bacterial communities across the river-ocean continuum.

Hydrocarbon composition and concentrations in the Gulf of Mexico sediments in the 3 years following the Macondo well blowout.

In April of 2010, the Macondo well blowout in the northern Gulf of Mexico resulted in an unprecedented release of oil into the water column at a depth of approximately 1500 m. A time series of surface and subsurface sediment samples were collected to the northwest of the well from 2010 to 2013 for molecular biomarker and bulk carbon isotopic analyses. While no clear trend was observed in subsurface sediments, surface sediments (0-3 cm) showed a clear pattern with total concentrations of n-alkanes, unresolved complex mixture (UCM), and petroleum biomarkers (terpanes, hopanes, steranes) increasing from May to September 2010, peaking in late November 2010, and strongly decreasing in the subsequent years. The peak in hydrocarbon concentrations were corroborated by higher organic carbon contents, more depleted Δ14C values and biomarker ratios similar to those of the initial MC252 crude oil reported in the literature. These results indicate that at least part of oil discharged from the accident sedimented to the seafloor in subsequent months, resulting in an apparent accumulation of hydrocarbons on the seabed by the end of 2010. Sediment resuspension and transport or biodegradation may account for the decrease in sedimented oil quantities in the years following the Macondo well spill.

Expression patterns of elemental cycling genes in the Amazon River Plume.

Metatranscriptomics and metagenomics data sets benchmarked with internal standards were used to characterize the expression patterns for biogeochemically relevant bacterial and archaeal genes mediating carbon, nitrogen, phosphorus and sulfur uptake and metabolism through the salinity gradient of the Amazon River Plume. The genes were identified in 48 metatranscriptomic and metagenomic data sets summing to >500 million quality-controlled reads from six locations in the plume ecosystem. The ratio of transcripts per gene copy (a direct measure of expression made possible by internal standard additions) showed that the free-living bacteria and archaea exhibited only small changes in the expression levels of biogeochemically relevant genes through the salinity and nutrient zones of the plume. In contrast, the expression levels of genes in particle-associated cells varied over orders of magnitude among the stations, with the largest differences measured for genes mediating aspects of nitrogen cycling (nifH, amtB and amoA) and phosphorus acquisition (pstC, phoX and phoU). Taxa varied in their baseline gene expression levels and extent of regulation, and most of the spatial variation in the expression level could be attributed to changes in gene regulation after removing the effect of shifting taxonomic composition. We hypothesize that changes in microbial element cycling along the Amazon River Plume are largely driven by shifting activities of particle-associated cells, with most activities peaking in the mesohaline regions where N2 fixation rates are elevated.

Deciphering ocean carbon in a changing world.

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. A vast number of compounds are present in DOM, and they play important roles in all major element cycles, contribute to the storage of atmospheric CO2 in the ocean, support marine ecosystems, and facilitate interactions between organisms. At the heart of the DOM cycle lie molecular-level relationships between the individual compounds in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have eluded clear definition because of the sheer numerical complexity of both DOM molecules and microorganisms. Emerging tools in analytical chemistry, microbiology, and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions being addressed using recent methodological and technological developments in those fields and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.

Chemical dispersants can suppress the activity of natural oil-degrading microorganisms.

During the Deepwater Horizon oil well blowout in the Gulf of Mexico, the application of 7 million liters of chemical dispersants aimed to stimulate microbial crude oil degradation by increasing the bioavailability of oil compounds. However, the effects of dispersants on oil biodegradation rates are debated. In laboratory experiments, we simulated environmental conditions comparable to the hydrocarbon-rich, 1,100 m deep plume that formed during the Deepwater Horizon discharge. The presence of dispersant significantly altered the microbial community composition through selection for potential dispersant-degrading Colwellia, which also bloomed in situ in Gulf deep waters during the discharge. In contrast, oil addition to deepwater samples in the absence of dispersant stimulated growth of natural hydrocarbon-degrading Marinobacter. In these deepwater microcosm experiments, dispersants did not enhance heterotrophic microbial activity or hydrocarbon oxidation rates. An experiment with surface seawater from an anthropogenically derived oil slick corroborated the deepwater microcosm results as inhibition of hydrocarbon turnover was observed in the presence of dispersants, suggesting that the microcosm findings are broadly applicable across marine habitats. Extrapolating this comprehensive dataset to real world scenarios questions whether dispersants stimulate microbial oil degradation in deep ocean waters and instead highlights that dispersants can exert a negative effect on microbial hydrocarbon degradation rates.

Microspatial gene expression patterns in the Amazon River Plume.

We investigated expression of genes mediating elemental cycling at the microspatial scale in the ocean's largest river plume using, to our knowledge, the first fully quantitative inventory of genes and transcripts. The bacterial and archaeal communities associated with a phytoplankton bloom in Amazon River Plume waters at the outer continental shelf in June 2010 harbored ∼ 1.0 × 10(13) genes and 4.7 × 10(11) transcripts per liter that mapped to several thousand microbial genomes. Genomes from free-living cells were more abundant than those from particle-associated cells, and they generated more transcripts per liter for carbon fixation, heterotrophy, nitrogen and phosphorus uptake, and iron acquisition, although they had lower expression ratios (transcripts ⋅ gene(-1)) overall. Genomes from particle-associated cells contributed more transcripts for sulfur cycling, aromatic compound degradation, and the synthesis of biologically essential vitamins, with an overall twofold up-regulation of expression compared with free-living cells. Quantitatively, gene regulation differences were more important than genome abundance differences in explaining why microenvironment transcriptomes differed. Taxa contributing genomes to both free-living and particle-associated communities had up to 65% of their expressed genes regulated differently between the two, quantifying the extent of transcriptional plasticity in marine microbes in situ. In response to patchiness in carbon, nutrients, and light at the micrometer scale, Amazon Plume microbes regulated the expression of genes relevant to biogeochemical processes at the ecosystem scale.

Sampling problems in Brazilian research: a critical evaluation of studies on medicinal plants

This work compiled Brazilian articles regarding medicinal plant use by local communities in order to analyze the most common sampling problems and if research characteristics can influence the presence of sampling irregularities. We focused on studies about medicinal plants that present a species-indications list and had a quantitative nature. The proportion of works with and without sampling problems was evaluated considering the journal impact factor, period of publication, community status (urban x rural), sample type, presence of testing hypothesis and presence of research questions. We found that an alarming proportion of papers had some kind of sampling problems (48.39% serious and 19.35% moderate). The most common problems were related to: lack of information regarding the sample size or the universe, small sample sizes and selection of specialists based on obscure criteria. We could not find a significant influence between our tested variables and the occurrence of sampling problems, except for the community status (urban x rural). Results indicate that a significant amount of intracultural diversity is not properly captured, taking into consideration both the population as a whole and a group of interest in the community (= healers).

Nova técnica: operação de Norwood com perfusão regional cerebral e coronariana / New technique: Norwood operation with regional cerebral and coronary perfusion

Objetivo: Avaliar o resultado imediato da operação de Norwood modificado com nova técnica de perfusão regional cerebral (PRCeA) anterógrada associado a perfusão regional coronariana (PRCoR) retrógrada em substituição à parada circulatória total com hipotermia profunda em crianças portadoras da Síndrome da Hipoplasia do Coração Esquerdo (SHCE) com aorta ascendente extremamente hipoplásica (AH). Métodos: No período de dezembro de 2006 a fevereiro de 2008, a operação de Norwood modificado com tubo entre o ventrículo direito e as artérias pulmonares ou shunt tipo Sano foi realizada em oito crianças portadoras de SHCE e aorta ascendente com diâmetro inferior a 3 mm, (quatro do sexo masculino e quatro do sexo feminino) com idade média de 9,2 dias (variando de 1 a 29 dias) e peso médio de 3,3 kg (variando de 2,7 a 3,8 kg). Utilizada CEC e hipotermia a 25ºC com duas cânulas venosas e anastomose de um enxerto de politetrafluoretileno com a artéria inominada utilizado como linha arterial e para PRCeA. A PRCoR foi realizada por meio de um desvio na linha arterial e colocação de um cateter na aorta ascendente. Foram analisados o resultado cirúrgico imediato e a presença de alterações neurológicas nesse período. Resultados: O resultado cirúrgico imediato revelou mortalidade de 25 por cento e ausência de comprometimento neurológico ao exame clínico. Conclusão: A operação de Norwood modificado pode ser realizada com PRCeA e PRCoR em crianças com SHCE e AH com resultado cirúrgico imediato satisfatório e ausência de complicações neurológicas.

Objective: To assess the immediate result of the modified Norwood procedure with new technique of anterograde regional cerebral perfusion (ARCeP) and retrograde regional coronary perfusion (RRCoP) in substitution of profound hypothermia and circulatory arrest in children with hypoplastic left heart syndrome (HLHS) with extremely hypoplastic ascending aorta (HA). Methods: In the period of December of 2006 to February 2008 the modified Norwood procedure with tube between the right ventricle and pulmonary arteries or Sano shunt was performed in eight children with HLHS and with ascending aorta diameter less than 3 mm, (four male and four female) with median age of 9.2 days (ranging from 1 to 29 days) and median weigh of 3.3 kg (ranging from 2.7 to 3.8 kg). We used cardiopulmonary bypass and hypothermia at 25ºC with two venous cannulas and suture with a polytetrafluoroethylene graft sutured to the innominate artery as an arterial line and used to ARCeP. The RRCoP was performed by a deviation in the arterial line and placement of a catheter in the ascending aorta. The immediate surgical results and the clinical neurological manifestation were assessed. Results: The immediate surgical results revealed mortality of 25 percent and there were absence of neurological injury at clinical examination. Conclusions: The modified Norwood procedure can be accomplished with ARCeP and RRCoP in children with HLHS with HA with satisfactory immediate surgical result and without neurological complications.

New technique: Norwood operation with regional cerebral and coronary perfusion.

OBJECTIVE: To assess the immediate result of the modified Norwood procedure with new technique of anterograde regional cerebral perfusion (ARCeP) and retrograde regional coronary perfusion (RRCoP) in substitution of profound hypothermia and circulatory arrest in children with hypoplastic left heart syndrome (HLHS) with extremely hypoplastic ascending aorta (HA). METHODS: In the period of December of 2006 to February 2008 the modified Norwood procedure with tube between the right ventricle and pulmonary arteries or Sano shunt was performed in eight children with HLHS and with ascending aorta diameter less than 3 mm, (four male and four female) with median age of 9.2 days (ranging from 1 to 29 days) and median weigh of 3.3 kg (ranging from 2.7 to 3.8 kg). We used cardiopulmonary bypass and hypothermia at 25 masculineC with two venous cannulas and suture with a polytetrafluoroethylene graft sutured to the innominate artery as an arterial line and used to ARCeP. The RRCoP was performed by a deviation in the arterial line and placement of a catheter in the ascending aorta. The immediate surgical results and the clinical neurological manifestation were assessed. RESULTS: The immediate surgical results revealed mortality of 25% and there were absence of neurological injury at clinical examination. CONCLUSIONS: The modified Norwood procedure can be accomplished with ARCeP and RRCoP in children with HLHS with HA with satisfactory immediate surgical result and without neurological complications.

Triterpenoids as major components of the insect-trapping glue of Roridula species.

Roridula dentata and R. gorgonias, two South African plants that were formerly believed to be carnivorous, exhibit an extremely sticky exudate at the tips of secretory trichomes. Unlike the trapping mucilage of Droseraceae, it does not consist of acidic polysaccharides. The Roridula trapping glue was found to be a mutual solution of mainly dihydroxytriterpenoids, instead. All samples contain two isomers of ring A dihydroxyolean-12-enes and dihydroxyurs-12-enes. The difference between the two species is the additional presence of taraxeradiol in the glue of R. gorgonias. The absolute chemical structures of the reported triterpenoids still need confirmation.

Source profiles of organic compounds emitted upon combustion of green vegetation from temperate climate forests.

Biomass burning is an important primary source of particles containing biomarker compounds, which are introduced into smoke primarily by direct volatilization/steam stripping and by thermal alteration based on combustion conditions. This study presents comprehensive organic compound source profiles for smoke from controlled burning of green vegetation native to the predominant temperate and semiarid forests of the western United States. Smoke particles were extracted with dichloromethane/methanol (2:1, v/v), and the extracts were analyzed as their TMS derivatives by gas chromatography-mass spectrometry. Carbohydrates were by far the major compound class emitted in smoke particles, encompassing 57-77% of the total extractable organic compounds detected here. Lignin derivatives (5-17%) and diterpenoids (up to 16%) from bleed resins were the next most abundant compound groups observed. The major individual compounds encompassed methyl-inositols (up to 41%, e.g., pinitol) for conifer smokes, deoxy-inositols (up to 32%, e.g., quercitol) for samples containing oak vegetation, and the thermally altered product of cellulose combustion levoglucosan (14-21%). The remaining compound classes, i.e., n-alkanoic acids, n-alkanols, n-alkanes, triterpenoids, steroids, and polycyclic aromatic hydrocarbons, were present at lower abundances (mostly < 5%). The results showed that burning of green (moist) vegetation imprints high amounts of polar/ water-soluble compounds into the smoke probably by volatilization/steam stripping processes, resulting in a different biomarker profile compared to dry/dead vegetation and wood combustion emissions.

Phenols and hydroxy-PAHs (arylphenols) as tracers for coal smoke particulate matter: source tests and ambient aerosol assessments.

Source tests were conducted to analyze and characterize diagnostic key tracers for emissions from burning of coals with various ranks. Ambient aerosol particulate matter was also collected in three areas of China and a background area in Corvallis, OR (U.S.) to confirm the presence of tracers specific for coal smoke. The results showed a series of aliphatic and aromatic hydrocarbons and phenolic compounds, including PAHs and hydroxy-PAHs as the major tracers, as well as a significant unresolved complex mixture (UCM) of compounds. The tracers that were found characteristic of coal combustion processes included hydroxy-PAHs and PAHs. Atmospheric ambient samples from Beijing and Taiyuan, cities where coal is burned in northern China, revealed that the hydroxy-PAH tracers were present during the wintertime, but not in cities where coal is not commonly used (e.g., Guangzhou, South China). Thus, the mass of hydroxy-PAHs can be apportioned to coal smoke and the source strength modeled by summing the proportional contents of EC (elemental carbon), PAHs, UCM and alkanes with the hydroxy-PAHs.

Gas chromatography coupled to mass spectrometry for analyses of organic compounds and biomarkers as tracers for geological, environmental, and forensic research.

Gas chromatography, especially when coupled with mass spectrometry, is the analytical method of choice for elucidation of biomarker compounds present in organic mixtures extracted from geological, environmental, and biological samples. This review describes the biomarker concept, i. e., the precursor natural products to the geological/environmental derivatives, and their application as multi-tracers in the geosphere and ambient environment. The mass spectrometric methods currently utilized for such analyses are reviewed with a general key to the literature, and typical examples of applications using GC-MS are also described.

Analysis of sugars in environmental samples by gas chromatography-mass spectrometry.

Many environmental samples contain complex mixtures of organic compounds with different sources, polarities and reactivities. This study reports a method for the analysis of both polar/water-soluble and apolar organic compounds in several kinds of environmental samples. The analytical method consists of extraction with a mixture of dichloromethane:methanol (2:1, v/v), silylation using BSTFA (N,O-bis-(trimethylsilyl)trifluoroacetamide) and analysis by gas chromatography-mass spectrometry (GC-MS), a common device in chemical and environmental laboratories. Fifty individual sugar standards, including monosaccharides, sugar alcohols, anhydrosugars, disaccharides and trisaccharides, were analyzed for the determination of their fragmentation patterns and retention times. Recoveries (at three concentrations) and limits of detection (LOD) were determined for a standard mixture containing glucose (monosaccharide), sorbitol (sugar alcohol), levoglucosan (anhydrosugar) and sucrose (disaccharide), and they varied from 68 to 119% and 130 to 360 ng mL(-1), respectively. The method was used for the analysis of aerosol particle, soil and sediment samples, and demonstrated its feasibility in detecting not only several important environmental sugars (e.g., glucose, fructose, inositol, mannitol, sorbitol, levoglucosan, sucrose, mycose), but also a large range of organic compound classes from other polar components (e.g., dicarboxylic acids) to apolar compounds such as n-alkanes. Therefore, the analytical method presented here demonstrated its usefulness for a better understanding of sources and transport of various organic compounds in different environmental compartments.