Total Particulate Carbon Research Articles

Carbon monoxide (CO) and particulate matter (PM) emissions during the combustion of wood pellets in a small-scale combustion unit – Influence of aluminum-(silicate-)based fuel additivation

The additivation of solid biofuels has proven to be an effective method for reducing total particulate matter (TPM) and carbon monoxide (CO) emissions, as well as for reducing ash-related problems related to, e.g., fouling and slagging. During the combustion with additives, potassium (K) released from the solid biofuels is bound into temperature-stable compounds, thus preventing the formation of inorganic (i.e., K-based) TPM. Simultaneously by reducing K in the gas phase, the inhibition of gas-phase oxidation (e.g., CO oxidation) due to interference of K within the existing radical pool is hindered. Particularly kaolin, an aluminum-silicate-based additive has proven effective in reducing not only TPM but also CO emissions. The mitigation effects on CO emissions have previously been reported mostly in a subordinate role and explanations are given in the form of hypotheses. In this study, seven additives (i.e., kaolin, kaolinite, meta-kaolinite, aluminum hydroxide, muscovite, muscovite coated with titanium dioxide and kalsilite, each at 0.3 wt%a.r.) were investigated during wood pellet combustion in a small-scale furnace (7.8 kW). For both CO and TPM emissions, kaolin proved to be most effective (i.e., −52% CO, −49% TPM), followed by muscovite, kaolinite, TiO2 coated muscovite, aluminum hydroxide, and meta-kaolinite.

Boosting methane production and raw waste activated sludge treatment in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system: The effect of organic loading rate

This study deals with the effect of different organic loading rates (OLRs) on the organic load removal and the productivity of methane, in a microbial electrolysis cell-anaerobic digestion (MEC-AD) system treating raw waste activated sludge (WAS). For comparison, two identical reactors, a control (AD) and a MEC-AD reactor were constructed. Both reactors operated for 131 days, during which different Organic Loading Rates (OLRs) were examined; 1.1, 1.7 and 2.9 gCOD/(L*d). The results showed that the MEC-AD reactor performed better, relative to the AD reactor, at high OLRs. Specifically, the additional total particulate carbon and Kjeldahl nitrogen removal reached 12% and 13%, respectively, at an OLR of 1.7 gCOD/(L*d), while they reached 19% and 13%, respectively, at an OLR of 2.9 gCOD/(L*d). Moreover, the biogas production and the methane content increased by 30% and 6%, respectively, at an OLR of 1.7 gCOD/(L*d) and by 32% and 5%, respectively, at an OLR of 2.9 gCOD/(L*d). The electrochemical measurements indicated that the power output increased from 5 to 30 mW/m2 when the OLR increased from 1.1 to 2.9 gCOD/(L*d). Overall, the results showed that the MEC-AD accelerated and enhanced the WAS treatment, boosting methane productivity.

Nunataryuk field campaigns: understanding the origin and fate of terrestrial organic matter in the coastal waters of the Mackenzie Delta region

Abstract. Climate warming and related drivers of soil thermal change in the Arctic are expected to modify the distribution and dynamics of carbon contained in perennially frozen grounds. Thawing of permafrost in the Mackenzie River watershed of northwestern Canada, coupled with increases in river discharge and coastal erosion, triggers the release of terrestrial organic matter (OMt) from the largest Arctic drainage basin in North America into the Arctic Ocean. While this process is ongoing and its rate is accelerating, the fate of the newly mobilized organic matter as it transits from the watershed through the delta and into the marine system remains poorly understood. In the framework of the European Horizon 2020 Nunataryuk programme, and as part of the Work Package 4 (WP4) Coastal Waters theme, four field expeditions were conducted in the Mackenzie Delta region and southern Beaufort Sea from April to September 2019. The temporal sampling design allowed the survey of ambient conditions in the coastal waters under full ice cover prior to the spring freshet, during ice breakup in summer, and anterior to the freeze-up period in fall. To capture the fluvial–marine transition zone, and with distinct challenges related to shallow waters and changing seasonal and meteorological conditions, the field sampling was conducted in close partnership with members of the communities of Aklavik, Inuvik and Tuktoyaktuk, using several platforms, namely helicopters, snowmobiles, and small boats. Water column profiles of physical and optical variables were measured in situ, while surface water, groundwater, and sediment samples were collected and preserved for the determination of the composition and sources of OMt, including particulate and dissolved organic carbon (POC and DOC), and colored dissolved organic matter (CDOM), as well as a suite of physical, chemical, and biological variables. Here we present an overview of the standardized datasets, including hydrographic profiles, remote sensing reflectance, temperature and salinity, particle absorption, nutrients, dissolved organic carbon, particulate organic carbon, particulate organic nitrogen, CDOM absorption, fluorescent dissolved organic matter intensity, suspended particulate matter, total particulate carbon, total particulate nitrogen, stable water isotopes, radon in water, bacterial abundance, and a string of phytoplankton pigments including total chlorophyll. Datasets and related metadata can be found in Juhls et al. (2021) (https://doi.org/10.1594/PANGAEA.937587).

Assessment of pollutant emission in Poland from various categories of transport

Abstract This paper refers to the inventory of pollutant emissions in Poland from different transport categories over the period 1990–2020. The changes in the annual national emissions of selected pollutants, i.e. nitrogen oxides, non-methane volatile organic compounds, sulfur oxides, PM2.5, PM10, total suspended particulate matter, carbon monoxide, and lead were analysed. The shares of the national annual emissions of the examined pollutants from each studied transport category in the national annual emission from total transport were assessed. The sensitivity of the national annual pollutant emission inventory with regard to the transport categories and emitted substances under the study was assessed. The trend of decrease in the national annual emissions of the substances analysed was appraised as positive in the face of a substantial intensification of transport activities. Taking into account the fact that road transportation is responsible for a dominant share of the national emission of pollutants, important progress in the reduction of emissions is attributable to the substantial technical improvement of the internal combustion engines of road vehicles.

Temporal dynamics of total microbial biomass and particulate detritus at Station ALOHA

Particulate adenosine-5′-triphosphate (P-ATP) and particulate carbon (PC) concentrations were measured on approximately monthly intervals throughout the upper water column (0–1000 m) over a 30-yr (1989–2018) period at Station ALOHA to track the seasonal-to-decadal variability in total microbial biomass and the dynamics of living-to-nonliving particulate organic matter pools. On selected cruises, samples were also collected to a depth of ∼4800 m. P-ATP concentrations were relatively uniform (27–34 ng l−1) throughout the upper euphotic zone (0–100 m) with a distinct peak at 45 m. P-ATP concentrations were significantly higher (p < 0.001) in summer (Jun-Aug) than in winter (Dec-Feb), especially between 45 and 100 m where the seasonal differences averaged 28%. Below 100 m, P-ATP concentrations decreased rapidly with depth to a 30-yr mean value of 3.5 ng ATP l−1 at 250 m, and then decreased more gradually to a 30-yr mean value of 0.9 ng ATP l−1 at 1000 m. Between 125 and 175 m, the seasonal peak in P-ATP shifted to spring (Mar-May), with minima in fall (Sep-Nov) and winter (Dec-Feb). No consistent seasonal variations in P-ATP were detected at depths >175 m, suggesting a temporally stable habitat. Assuming a PC:P-ATP ratio of 250:1 (g g−1), the 0–100 m, 100–250 m, and 250–1000 m depth-integrated microbial biomass estimates were 775, 425, and 350 mg C m−2, respectively. Bathypelagic zone (>1000 m) P-ATP concentrations, based on a more limited data set than the upper portions of the water column, were low (0.4–0.7 ng ATP l−1). However, when integrated over the entire deep water habitat (1000–4800 m), bathypelagic zone microbial biomass was substantial (425 mg C m−2). Expressed as a percentage of total PC, microbial biomass ranged from ∼30% in the upper euphotic zone to ∼3% at depths >3000 m, emphasizing the preponderance of detrital PC throughout the entire water column. The total water column inventory of microbial biomass at Station ALOHA was 2 g C m−2 compared to ∼18 g C m−2 for total suspended PC; approximately 50% of the total microbial biomass is resident in the aphotic zone (>175 m). Although daily gross primary production at Station ALOHA is on par with the total euphotic zone (0–175 m)-integrated microbial biomass (∼1 g C m−2 d−1 and ∼1 g C m−2, respectively), the sources of C and energy fueling the substantial aphotic zone microbial biomass (∼1 g m−2) are not well understood at the present time.

Shifts in growth light optima among diatom species support their succession during the spring bloom in the Arctic

Abstract Diatoms of the Arctic Ocean annually experience extreme changes of light environment linked to photoperiodic cycles and seasonal variations of the snow and sea‐ice cover extent and thickness which attenuate light penetration in the water column. Arctic diatom communities exploit this complex seasonal dynamic through a well‐documented species succession during spring, beginning in sea‐ice and culminating in massive phytoplankton blooms underneath sea‐ice and in the marginal ice zone. The pattern of diatom taxa sequentially dominating this succession is relatively well conserved interannually, and taxonomic shifts seem to align with habitat transitions. To understand whether differential photoadaptation strategies among diatom taxa explain these recurring succession sequences, we coupled laboratory experiments with field work in Baffin Bay at 67.5°N. Based on field data, we selected five diatom species typical of different ecological niches and measured their growth rates under light intensity ranges representative of their natural habitats. To characterize their photoacclimative responses, we sampled pigments and total particulate carbon, and conducted 14C‐uptake photosynthesis response curves and variable fluorescence measurements. We documented a gradient in species respective light intensity for maximal growth suggesting divergent light response plasticity, which for the most part align with species sequential dominance. Other photophysiological parameters supported this ecophysiological framing, although contrasts were always clear only between succession endmembers, Nitzschia frigida and Chaetoceros neogracilis. To validate that these photoacclimative responses are representative of in situ dynamics, we compared them to the chlorophyll a‐specific light‐limited slope (α*) and saturated rate of photosynthesis (), monitored in Baffin Bay on sea‐ice and planktonic communities. This complementary approach confirmed that unusual responses in α* and as a function of light history intensity are similar between sentinel sympagic species N. frigida and natural ice‐core communities. While no light‐history‐dependent trends were observed in planktonic communities, their α* and values were in the range of measurements from our monospecific cultures. Synthesis. Our results suggest that Arctic diatoms species photoadaptation strategy is tuned to the light environment of the habitats in which they dominate and indeed drives the seasonal taxonomic succession.

Depth profiles of suspended carbon and nitrogen along a North Pacific transect: Concentrations, isotopes, and ratios

AbstractWe present concentrations of total particulate carbon (PC), carbonate (PIC), total particulate nitrogen (PN), 13C and 15N of suspended particles along a North Pacific transect. In the upper 400 m, suspended PIC to particulate organic carbon (POC) ratios generally follow published sinking PIC/POC ratios. Below 600 m, suspended PIC/POC become significantly lower than sinking PIC/POC, likely indicating PIC dissolution within the suspended load. In three out of the five stations, suspended PN δ15N increase with depth from the euphotic zone to the thermocline, consistent with previous observations in many ocean regions (e.g.,BATS and HOT). However, in the other two stations where phytoplankton blooms were encountered, high suspended PN δ15N (up to 12‰) were observed in the euphotic zone, which was likely caused by the export of low‐δ15N PN during the phytoplankton blooms. Average Corg : N ratio of suspended particles along the transect is 5.1 0.2, with the value in the subtropical gyre (5.8 0.3) slightly higher than the subarctic gyre (4.6 0.2).

Constraining growth rates and the ratio of living to nonliving particulate carbon using beam attenuation and adenosine‐5′‐triphosphate at Station ALOHA

AbstractCarbon is not only the foundation of all life on our planet, but also an element that persists in detrital material long after living organisms die. Quantifying the relative amount of living and nonliving carbon in suspended particles in the ocean is challenging and rarely done; yet it is key to understanding the fate of organic matter and informing food web models. Here, we use particulate adenosine‐5′‐triphosphate (ATP) and particulate carbon (PC) data collected as a component of the Hawaii Ocean Time‐series program to show that living particles comprise only ~ 26–42% of the total PC pool in the surface waters of the North Pacific Subtropical Gyre, regardless of time of year. Diel‐resolving particulate beam attenuation data are then used in conjunction with PC and ATP data to constrain living particle net growth rates for this system, yielding rates of ~ 0.5–0.7 d−1 year‐round. These estimates are realistic and consistent with previous microscopy and incubation‐based work in the region.

Carbon export and fate beneath a dynamic upwelled filament off the California coast

Abstract. To understand the vertical variations in carbon fluxes in biologically productive waters, four autonomous carbon flux explorers (CFEs), ship-lowered CTD-interfaced particle-sensitive transmissometer and scattering sensors, and surface-drogued sediment traps were deployed in a filament of offshore flowing, recently upwelled water, during the June 2017 California Current Ecosystem – Long Term Ecological Research process study. The Lagrangian CFEs operating at depths from 100–500 m yielded carbon flux and its partitioning with size from 30 µm–1 cm at three intensive study locations within the filament and in waters outside the filament. Size analysis codes intended to enable long-term CFE operations independent of ships are described. Different particle classes (anchovy pellets, copepod pellets, and &gt; 1000 µm aggregates) dominated the 100–150 m fluxes during successive stages of the filament evolution as it progressed offshore. Fluxes were very high at all locations in the filament; below 150 m, flux was invariant or increased with depth at the two locations closer to the coast. Martin curve b factors (± denotes 95 % confidence intervals) for total particulate carbon flux were +0.37 ± 0.59, +0.85 ± 0.31, −0.24 ± 0.68, and −0.45 ± 0.70 at the three successively occupied locations within the plume, and in transitional waters. Interestingly, the flux profiles for all particles &lt; 400 µm were a much closer fit to the canonical Martin profile (b−0.86); however, most (typically &gt; 90 %) of the particle flux was carried by &gt; 1000 µm sized aggregates which increased with depth. Mechanisms to explain the factor of 3 flux increase between 150 and 500 m at the mid-plume location are investigated.

Development of a Monitoring System for Semicontinuous Measurements of Stable Carbon Isotope Ratios in Atmospheric Carbonaceous Aerosols: Optimized Methods and Application to Field Measurements.

Carbon content constitutes a major fraction of atmospheric particulate matter (PM) and directly influences the earth's climate and human health. The stable carbon isotope ratios (δ13C) can be used to track potential sources and atmospheric processes of carbonaceous aerosols. Previously, determination of δ13C was always conducted in offline carbonaceous aerosol samples. The poor time-resolution results cannot provide information regarding the temporal evolution of δ13C at a short-time scale. In this study, we developed a new system for online measurements of δ13C in atmospheric carbonaceous aerosols by combining a semicontinuous organic carbon/elemental carbon (OC/EC) analyzer and online cavity ring-down spectroscopy (CRDS) (OC/EC analyzer-CRDS). To provide better stability in the determination of δ13C, a carrier gas with CO2 (∼200 ppm) in "balance gas" was used, and Keeling analysis was employed to separate the δ13C signal of the sample from background CO2 gas. Our results showed that the accuracy and absolute precision of the δ13C measurements by the OC/EC analyzer-CRDS system were better than 0.1‰ and 0.5‰, respectively, for the samples containing carbon content more than 5 μg. Furthermore, we employed this system to monitor δ13C (δ13C-TC) in particulate total carbon (TC) with a time resolution of 2-4 h over Beijing in late summer and early autumn, 2019. During the sampling period, the TC concentrations varied from 0.1 to 12.0 μg m-3 with a mean value of 6.0 ± 2.4 μg m-3. The δ13C-TC ranged from -28.2 to -24.2‰ (mean value was -25.9 ± 0.9‰) without significant diurnal variations, suggesting similar contributing sources to TC. Comparing the δ13C signatures of different emissions, we found that liquid fuels and primary and secondary C3 plants were likely the dominant sources of particulate TC. Finally, we found that atmospheric heavy precipitation washed out the aged aerosols from the polluted air, resulting in significant depletion (∼2.4‰) of δ13C-TC in the atmosphere. This paper described a novel system for conducting online measurements of δ13C in atmospheric carbonaceous aerosols and provided us information to better understand the temporal evolution of emission sources and atmospheric processes of carbonaceous aerosols.

A comprehensive assessment of ambient air quality in Çanakkale city: Emission inventory, air quality monitoring, source apportionment, and respiratory health indicators

This comprehensive study aims to examine the relationships between ambient air quality (AAQ) and respiratory health of the participants residing in three different towns of Çanakkale city, Turkey between August 2013 and 2014. AAQ measurements for bioaerosols, volatile organic compounds (VOCs), total particulate matter (PM) count, carbon dioxide (CO2), and carbon monoxide (CO) were performed and monthly pulmonary function test (PFT) was applied to volunteer participants residing in the study sites (n = 121) for one year. Additionally, concentrations of air pollutants for PM2.5/PM10, sulfur dioxide (SO2), nitrogen oxides, and ozone were gathered from AAQ monitoring stations. To estimate the contributions of the emission sources and their effects on human health in the region, an emission inventory was also prepared in the region and AERMOD modelling system was applied for the year of 2013. Accordingly, the industry was the most polluting sector for NOx and SO2, while road traffic and residential heating were the most polluting sectors for CO and PM10. Factor analysis revealed that organics, combustion, bioaerosol propagation, and ozone accumulation contributed to AAQ, in agreement with AQ modelling results. Çan had the worst air quality (industrialized site), which affected the respiratory health indicators of the participants. Generalized linear model estimated that PF of the participants varied according to the residing district, gender, suffering from asthma, and lifelong smoking or environmental tobacco smoke exposure (p < 0.05). Also, PF of the participants were linked with VOCs levels in the Central town, total PM count in Lapseki, and ozone levels in Çan (p < 0.05).

Modeling microalgae growth in continuous culture: Parameters analysis and temperature dependence

Microalgae are considered to be a promising biofuel resource for carbon dioxide fixation in the future. Modeling the growth of microalgae is an effective method to study the growth performance of microalgae, which is also helpful to control the cultivation of microalgae in artificial bioreactor. In continuous culture, dilution rate and influent inorganic nitrogen concentration have shown significant effects on the growth of microalgae. In this paper, the common and overall influences of dilution rate and influent inorganic nitrogen concentration on the microalgae growth have been investigated. Based on numerical simulation, this paper plots the results of total and unit time particulate carbon concentration in 3D figures to expose the varied tendency. It is found that the value of points on the ridge line increases with the dilution rate decreasing and influent inorganic nitrogen concentration increasing for both the total particulate carbon concentration and the particulate carbon concentration per day. The influence of several typical temperatures has been modeled and calculated. The value of biomass productivity will be further increased when the dilution rate is getting closer to 0. This paper will go a step further for the parameters design of continuous culture photo-bioreactor (PBR) for later study.

Effect of electric heating and ice added to the bowl on mainstream waterpipe semivolatile furan and other toxicant yields

ObjectivesWe examined mainstream total particulate matter, nicotine, cotinine, menthol, pyrene, carbon monoxide (CO) and semivolatile furan yields from a commercial waterpipe with two methods for heating the tobacco, quick-light charcoal...

Simulation of suspended sediment and black carbon transport in surface water layer of Ha Long bay

Delft3D model employed to simulate the distribution and transport of suspended sediment and black carbon in Ha Long bay shows outcomes meeting with results from previous experiment studies. In the rainy season, suspended matter in surface layer is mainly in waters of western and southwestern Cat Ba island regions, and from Cua Luc toward the south nearshore areas with concentration of 50–130 g/m3. The concentration of suspended setdiment in the waters from Cua Luc to the north nearshore area is from 20 g/m3 to 50 g/m3 and that of offshore areas is 2–20 g/m3. In the dry season, the average concentrations of suspended matter are lower, approximately 110–150 g/m3 compared to the rainy season. In the rainy season, the total particulate carbon in surface layer is 0.0016–0.0028 kg/m3 and in the dry season, it ranges from 0.0001–0.005 kg/m3.

Variations in the abundance and distribution of aggregates in the Ross Sea, Antarctica

The vertical distribution and temporal changes in aggregate abundance and sizes were measured in the Ross Sea, Antarctica between 2002 and 2005 to acquire a more complete understanding of the mechanisms and rates of carbon export from the euphotic layer. Aggregate abundance was determined by photographic techniques, and water column parameters (temperature, salinity, fluorescence, transmissometry) were assessed from CTD profiles. During the first three years the numbers of aggregates increased seasonally, being much more abundant within the upper 200 m in late summer than in early summer from 50 to 100 m (12.5 L–1 in early summer vs. 42.9 L–1 in late summer). In Year 4 aggregate numbers were substantially greater than in other years, and average aggregate abundance was maximal in early rather than late summer (177 vs. 84.5 L–1), which we attributed to the maximum biomass and aggregate formation being reached earlier than in other years. The contribution of aggregate particulate organic carbon to the total particulate carbon pool was estimated to be 20%. Ghost colonies, collapsed colonies of the haptophyte Phaeocystis antarctica, were observed during late summer in Year 4, with maximum numbers in the upper 100 m of ca. 40 L–1. Aggregate abundance, particulate organic carbon and ghost colonies all decreased exponentially with depth, and the rate of ghost colony disappearance suggested that their contribution to sedimentary input was small at the time of sampling. Bottom nepheloid layers were commonly observed in late summer in both transmissometer and aggregate data. Late summer nepheloid layers had fluorescent material within them, suggesting that the particles were likely generated during the same growing season. Longer studies encompassing the entire production season would be useful in further elucidating the role of these aggregates in the carbon cycle of these regions.

Estimation of Suspended Matter, Organic Carbon, and Chlorophyll-a Concentrations from Particle Size and Refractive Index Distributions

Models of particle density and of organic carbon and chlorophyll-a intraparticle concentration were applied to particle size distributions and particle real refractive index distributions determined from flow cytometry measurements of natural seawater samples from a range of UK coastal waters. The models allowed for the estimation of suspended particulate matter, organic suspended matter, inorganic suspended matter, particulate organic carbon, and chlorophyll-a concentrations. These were then compared with independent measurements of each of these parameters. Particle density models were initially applied to a simple spherical model of particle volume, but generally overestimated independently measured values, sometimes by over two orders of magnitude. However, when the same density models were applied to a fractal model of particle volume, successful agreement was reached for suspended particulate matter and both inorganic and organic suspended matter values (RMS%E: 57.4%, 148.5%, and 83.1% respectively). Non-linear organic carbon and chlorophyll-a volume scaling models were also applied to a spherical model of particle volume, and after an optimization procedure achieved successful agreement with independent measurements of particulate organic carbon and chlorophyll-a concentrations (RMS%E: 45.6% and 51.8% respectively). Refractive index-based models of carbon and chlorophyll-a intraparticle concentration were similarly tested, and were also found to require a fractal model of particle volume to achieve successful agreement with independent measurements, producing RMS%E values of 50.2% and 45.2% respectively after an optimization procedure. It is further shown that the non-linear exponents of the volume scaling models are mathematically equivalent to the fractal dimensionality coefficients that link cell volume to mass concentration, reflecting the impact of non-uniform distribution of intracellular carbon within cells. Fractal models of particle volume are thus found to be essential to successful closure between results provided by models of particle mass, intraparticle carbon and chlorophyll content, and bulk measurements of suspended mass and total particulate carbon and chlorophyll when natural mixed particle populations are concerned. The results also further confirm the value of determining both size and refractive index distributions of natural particle populations using flow cytometry.

Porewater dissolved organic and inorganic carbon in relation to methane occurrence in sediments of the Gdańsk Basin (southern Baltic Sea)

The impact of methane occurrence on carbon forms dissolved in pore waters was investigated in the present study. The cores were collected at three geochemically different stations in the Gdańsk Basin area (southern Baltic Sea). Sediments were analyzed for methane, total particulate carbon (TPC) and particulate organic carbon (POC). In pore waters extracted using Rhizon samplers the following parameters were measured: sulfate, total dissolved sulfide (TDS), dissolved inorganic (DIC) and organic carbon (DOC). Concentrations of DIC and DOC in pore water profiles were up to 5 times higher at stations with methane compared to the station without methane in shallow sediments. Average fluxes of DIC and DOC were calculated for three separate sediment layers at each station (surface layer – benthic flux, flux in sulfate-methane transition (SMT) or in intermediate layer and flux below SMT/intermediate). Benthic DIC and DOC fluxes were highest at one of the stations with shallow SMT (7–20 cm): 8.71 mmol m−2 d−1 and max. 1.48 mmol m−2 d−1, respectively. Additionally, we found strong dependences between DIC and DOC in sediments of stations with methane (R2 = 0.98). The relationship between methane and DOC in sediment profiles was described by exponential regression (R2 = 0.83). The contribution of particulate inorganic carbon (PIC) in TPC was significantly higher at the methane station with highest DIC concentration and fluxes.

Bacterial-viral interactions in the sea surface microlayer of a black carbon-dominated tropical coastal ecosystem (Halong Bay, Vietnam)

Increasing human activity has raised concerns about the impact of deposition of anthropogenic combustion aerosols (i.e., black carbon; BC) on marine processes. The sea surface microlayer (SML) is a key gate for the introduction of atmospheric BC into the ocean; however, relatively little is known of the effects of BC on bacteria-virus interactions, which can strongly influence microbially mediated processes. To study the impact of BC on bacteria-virus interactions, field investigations involving collection from the SML and underlying water were carried out in Halong Bay (Vietnam). Most inorganic nutrient concentrations, as well as dissolved organic carbon, were modestly but significantly higher (p = 0.02–0.05) in the SML than in underlying water. The concentrations of particulate organic carbon (though not chlorophyll a) and of total particulate carbon, which was composed largely of particulate BC (mean = 1.7 ± 6.4 mmol L–1), were highly enriched in the SML, and showed high variability among stations. On average, microbial abundances (both bacteria and viruses) and bacterial production were 2- and 5fold higher, respectively, in the SML than in underlying water. Significantly lower bacterial production (p &amp;lt; 0.01) was observed in the particulate fraction (&amp;gt;3 µm) compared to the bulk sample, but our data overall suggest that bacterial production in the SML was stimulated by particulate BC. Higher bacterial production in the SML than in underlying water supported high viral lytic infection rates (from 5.3 to 30.1%) which predominated over percent lysogeny (from undetected to 1.4%). The sorption of dissolved organic carbon by black carbon, accompanied by the high lytic infection rate in the black carbon-enriched SML, may modify microbially mediated processes and shift the net ecosystem metabolism (ratio of production and respiration) to net heterotrophy and CO2 production in this critical layer between ocean and atmosphere.

Origin of Fine Particulate Carbon in the Rural United States.

Carbonaceous compounds are a significant component of fine particulate matter and haze in national parks and wilderness areas where visibility is protected, i.e., class I areas (CIAs). The Regional Haze Rule set the goal of returning visibility in CIAs on the most anthropogenically impaired days to natural by 2064. To achieve this goal, we need to understand contributions of natural and anthropogenic sources to the total fine particulate carbon (TC). A Lagrangian chemical transport model was used to simulate the 2006-2008 contributions from various source types to measured TC in CIAs and other rural lands. These initial results were incorporated into a hybrid model to reduce systematic biases. During summer months, fires and vegetation-derived secondary organic carbon together often accounted for >75% of TC. Smaller contributions, <20%, from area and mobile sources also occurred. During the winter, contributions from area and mobile sources increased, with area sources accounting for half or more of the TC in many regions. The area emissions were likely primarily from residential and industrial wood combustion. Different fire seasons were evident, with the largest contributions during the summer when wildfires occur and smaller contributions during the spring and fall when prescribed and agricultural fires regularly occur.

Distribution and abundance of mesozooplankton in the Ross Sea, Antarctica

Zooplankton (meso- and macrozooplankton) distributions and biomass are poorly known in the Ross Sea despite their importance in energy transfer within food webs and biogeochemical cycles. Mesozooplankton abundance and biomass on the continental shelf are spatially variable and span two orders of magnitude during austral summer. Selected sub-regions (near the shelf break or ice shelf) show similar variability, suggesting that other processes, either oceanographic or biological, influence zooplankton on smaller scales. Biomass at one location (76.5° S, 172° E) was consistently elevated throughout January, although the causes of this “hotspot” were unclear. At a station near the ice shelf, abundance and biomass of the pteropod Limacina antarctica was very high. Zooplankton biomass at this location was sevenfold greater than any other station, and while the high biomass was driven by pteropod contributions, copepods were also abundant. Copepods dominated the mesozooplankton composition at all other stations, comprising 90 and 78% on average of the total abundance and biomass. Zooplankton biomass comprised on average 3.96% of the total particulate carbon (0–200 m) and was weakly correlated with chlorophyll and biogenic silica. We suggest that summer zooplankton growth and biomass, while linked to organic matter concentrations, are regulated by other factors (e.g., predation by crystal krill and Antarctic silverfish), as both grazers may be responsible for significant losses. Our data indicate that, contrary to other suggestions, summer zooplankton biomass and abundance in the Ross Sea are similar to those in other Antarctic coastal regions.