Particulate Carbon Concentrations Research Articles

Mobile-monitoring of Black Carbon and Ultrafine particles in Bangalore, India

INTRODUCTION--Mobile monitoring can effectively capture spatial patterns in on-road exposure. Here, we report measured on-road concentrations of black carbon and ultrafine particles in urban and peri-urban Bangalore, India.METHODS--Our mobile platform, a CNG car, was equipped with an aethalometer for black carbon (BC) and a condensation particle counter for ultrafine particles (UFP). We sampled on roadways in four parts of Bangalore: a central business district, a residential urban neighborhood, a peri-urban neighborhood, and along an urban-rural transect; in total, we collected ~400 h (~5000 km) of on-road data. Our study design involved oversampling each road segment (n=25 repeated samples per road). We then quantify, via subsequent subsampling, the data requirements for robustly estimating time-integrated concentrations. We computed average concentration for each 30m road segment and computed mean and median concentrations for each region.RESULTS--Mean on-road concentrations were highest in the central business district (BC: 50 µg/m3; UFP: 145,000 cm-3), intermediate in the urban residential neighborhood (32 µg/m3; 87,000 cm-3), and lowest in the peri-urban neighborhood (29 µg/m3; 30,000 cm-3). Median values are 2% - 38% less than mean. The urban-rural transect reveals analogous spatial patterns: average concentrations decline when going from downtown to the peri-urban area; spatial gradients are larger for UFP than BC. Subsampling analyses reveal how the robustness of estimated mean concentrations varies with number of observations and the timing of those observations, and how that relationship varies in space.CONCLUSION--Average on-road concentrations decline from downtown to the peri-urban area; spatial gradients are larger for UFP than BC. Our subsampling analyses inform how many visits are needed to obtain robust estimates of long-term average concentrations, as well as how that result varies in space and time.

Imbalanced Stoichiometric Reservoir Sedimentation Regulates Methane Accumulation in China's Three Gorges Reservoir

AbstractThe river‐reservoir continuum drives a separation of sedimentation along the longitudinal hydrodynamic gradients, potentially causing imbalanced stoichiometric sedimentation. However, there are still uncertainties regarding the contribution of imbalanced stoichiometric sedimentation to methane emissions along this continuum. A 2‐year field survey and in situ experiments were conducted in China's Three Gorges Reservoir (TGR), a river‐valley‐dammed reservoir. Sediments were trapped and collected to analyze for particulate carbon (C), nitrogen (N), and phosphorus (P) concentrations of different sizes in the summer flooded and winter dry seasons along the mainstem. Large amounts of sediments were deposited in the middle part of the TGR, particularly in the summer flood season. Hydrodynamic gradients structured imbalanced stoichiometric sedimentation patterns. Averaged particulate C:N:P proportions in the sediment layer along the upper, middle, and lower parts of the TGR in the first 30 years of reservoir operation were estimated to be 68:7:1, 97:8:1, and 151:13:1, respectively. The middle part of the TGR, being the “control point” of methane accumulation based on seasons, exhibited a shift in stoichiometry and stable isotope signatures, indicating that there was likely a shift in sources of POM. P, specifically in smaller size particles (<10 μm), seemed to be the potential key driver that regulates particulate C:N:P in the sediment of the TGR. Its sedimentation, primarily in the middle part of the TGR, contributed to the significant decreases in particulate C/P ratios and could possibly regulate long‐term CH4 accumulation in the reservoir.

CARBON AND NITROGEN IN SOILS AND HUMIC FRACTIONS OF DIFFERENT PEDOFORMS IN THE ATLANTIC FOREST BIOME

Relief is a soil formation factor that can modify the distribution of soil organic matter (SOM) fractions in a landscape. The objective of this study was to evaluate the effect of the relief on SOM fractions, considering their distribution in different topographic positions, segments, in two pedoforms (concave and convex) in areas covered with forest in the Atlantic Forest biome. The two pedoforms were selected in adjacent areas and divided into segments considering the topographic variation. The carbon and nitrogen origins were evaluated in the extract up to 100 cm of depth. Soil samples from the 0-5, 5-10, and 10-20 cm layers were collected for chemical characterization and fractioning (granulometric and chemical) of the SOM. The soil density in the 0-5 and 5-10 cm layers was determined to calculated the carbon stocks. The isotopic composition showed predominance of 13C. The highest organic carbon and particulate carbon contents were found in the convex pedoform. The distribution of humic fractions showed that the larger part of the humidified carbon was in the humin fraction. The humin and fulvic acid fractions were higher in the convex pedoform. The carbon stocks were, in general, higher in the convex pedoform, decreasing as the soil depth increased; and nitrogen stocks presented no differences. The higher carbon and nitrogen contents were found in the convex pedoform and in the lower region of the concave pedoform.

Characteristics, distribution, and sources of particulate carbon in rainfall collected by a sequential sampler in Nanchang, China

Wet deposition is the most important sink of atmospheric particulate matter. Although some studies have evaluated the concentrations of particulate carbon in rainfall, few have analyzed the changing distribution of particulate carbon during the precipitation process. Automatic sequential rainfall collections were obtained in Nanchang City, China, using a 4 mm precipitation interval, and the concentrations of water-insoluble carbon compounds (WIOC) and elemental carbon (EC) were evaluated. The concentrations of WIOC and EC in each 4 mm fraction were precisely determined, and the sources of WIOC and EC were analyzed. The concentrations of WIOC and EC in Nanchang precipitation ranged from 0.0012 mg L−1 to 3.55 mg L−1 and from 0.0061 mg L−1 to 2.30 mg L−1, respectively. WIOC and EC varied greatly among precipitation events and decreased gradually during individual events. Higher precipitation intensity caused greater rates of sub-cloud carbon wash-out and decreasing concentrations of carbon in precipitation. The WIOC/EC ratio during most rainfall events was about 2, but the ratio during the last stage of rainfall often exceeded 2. The correlation between WIOC and EC in the first two 4 mm precipitation fractions was very high, while the correlation between WIOC and EC in the last two fractions was weaker. The majority of WIOC and EC in precipitation originated in sub-cloud atmospheric particles, though a significant percentage of WIOC and EC in the final fraction of precipitation originated from cloud water. As a precipitation event progressed, the contribution of sub-cloud particulate carbon decreased, while the contribution of particulate carbon in cloud water increased.

Bio-inspired Recyclable Carbon Interface for Solar Steam Generation

Solar power, as one of renewable energy, holds potential application for producing steam which relies on high-temperature liquid by traditional methods. Herein, steam was generated by a bio-inspired strategy derived from the plants transpiration using a Printed Recyclable Carbon Membrane (PRCM). The membrane structure facilitated the concentration of carbon particles for the photoreaction and the heat generation for water evaporation, thereby improving the photo-thermal conversion efficiency. The PRCM achieved the best steady evaporation efficiency of 51.9%, which was 5.6 times higher than the value for water and recycling tests were demonstrated. The carbon particles were separated from the water under the magnetism action, a convenient approach that avoided secondary pollution resulting from the disintegration of the PRCM. Rapid preparation, low cost, and reusability of the printed carbon membrane allow for photo-thermal applications such as solar steam generation and seawater desalination.

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.

Thermo-chemical equilibrium modeling and simulation of biomass gasification

Here, we present the results of numerical studies of biomass gasification using poultry litter, sewage sludge and wood waste (pine shavings) as examples of starting materials. The aim of the study was to find ways to increase the degree of biomass conversion to combustible gaseous products (CO, H2, CnHm) and to achieve high calorific value of the generated synthesis gas. Modeling biomass gasification was performed for a multicomponent reacting system in a state of thermodynamic and chemical equilibrium. The mathematical model and the calculation program created by the authors were used. The presence of a condensed phase in the form of fine particles of solid carbon and ash in biomass gasification products was taken into account. The optimal levels of gasification temperatures and conditions that help minimizing the concentration of solid carbon particles in gasification products were determined. For optimal biomass gasification, we recommend using the thermal energy obtained from burning part of the generated syngas.

Development of electrically conductive composites based on recycled resources

The current study was focused on the development of electrically conductive composites of carbon particle filled cotton fabric/epoxy systems. The carbon particles were refined to the scale of micro/nanoparticles using ball milling and morphological properties were studied by Malvern zetasizer and SEM. The influence of different concentrations of carbon particles in green epoxy resin for electrical conductivity was studied. Additionally, the electrical conductivity and electromagnetic shielding ability of conductive composites were analyzed. Waveguide method at high frequency (i.e. at 2.45 GHz) was used to investigate the EMI shielding. Similarly, the effect of different concentrations of carbon particles in composites was also studied for mechanical strength (tensile and flexural). A comprehensive study showed the improvements in electrical and mechanical properties with increase in the concentration of carbon particles and their even distribution in resin. The composites with higher carbon filler concentration showed maximum electrical conductivity (1.0E–02), shielding effectiveness 23.13 dB and mechanical properties.

Supplemental Folate and the Relationship Between Traffic-Related Air Pollution and Livebirth Among Women Undergoing Assisted Reproduction.

Traffic-related air pollution has been linked to higher risks of infertility and miscarriage. We evaluated whether folate intake modified the relationship between air pollution and livebirth among women using assisted reproductive technology (ART). Our study included 304 women (513 cycles) presenting to a fertility center in Boston, Massachusetts (2005-2015). Diet and supplements were assessed by food frequency questionnaire. Spatiotemporal models estimated residence-based daily nitrogen dioxide (NO2), ozone, fine particulate, and black carbon concentrations in the 3 months before ART. We used generalized linear mixed models with interaction terms to evaluate whether the associations between air pollutants and livebirth were modified by folate intake, adjusting for age, body mass index, race, smoking, education, infertility diagnosis, and ART cycle year. Supplemental folate intake significantly modified the association of NO2 exposure and livebirth (P = 0.01). Among women with supplemental folate intakes of <800 μg/day, the odds of livebirth were 24% (95% confidence interval: 2, 42) lower for every 20-parts-per-billion increase in NO2 exposure. There was no association among women with intakes of ≥800 μg/day. There was no effect modification of folate on the associations between other air pollutants and livebirth. High supplemental folate intake might protect against the adverse reproductive consequences of traffic-related air pollution.

Health effects of exposure to diesel exhaust in diesel-powered trains

BackgroundShort-term controlled exposure to diesel exhaust (DE) in chamber studies have shown mixed results on lung and systemic effects. There is a paucity of studies on well-characterized real-life DE exposure in humans. In the present study, 29 healthy volunteers were exposed to DE while sitting as passengers in diesel-powered trains. Exposure in electric trains was used as control scenario. Each train scenario consisted of three consecutive days (6 h/day) ending with biomarker samplings.ResultsCombustion-derived air pollutants were considerably higher in the passenger carriages of diesel trains compared with electric trains. The concentrations of black carbon and ultrafine particles were 8.5 μg/m3 and 1.2–1.8 × 105 particles/cm3 higher, respectively, in diesel as compared to electric trains. Net increases of NOx and NO2 concentrations were 317 μg/m3 and 36 μg/m3. Exposure to DE was associated with reduced lung function and increased levels of DNA strand breaks in peripheral blood mononuclear cells (PBMCs), whereas there were unaltered levels of oxidatively damaged DNA, soluble cell adhesion molecules, acute phase proteins in blood and urinary excretion of metabolites of polycyclic aromatic hydrocarbons. Also the microvascular function was unaltered. An increase in the low frequency of heart rate variability measures was observed, whereas time-domain measures were unaltered.ConclusionExposure to DE inside diesel-powered trains for 3 days was associated with reduced lung function and systemic effects in terms of altered heart rate variability and increased levels of DNA strand breaks in PBMCs compared with electric trains.Trial registrationClinicalTrials.Gov (NCT03104387). Registered on March 23rd 2017

Abundance and Light Absorption Properties of Brown Carbon Emitted from Residential Coal Combustion in China.

Brown carbon (BrC) fractions, including water-soluble organic carbon (WSOC), water-soluble humic-like substances (HULISw), alkaline soluble organic carbon (ASOC), and methanol soluble organic carbon (MSOC) were extracted from particles emitted from the residential combustion of coal with different geological maturities. The abundances and light absorption properties of these BrC fractions were comprehensively studied. The results showed that the abundances of the different constituents of the BrC fraction varied greatly with the extraction solvent, accounting for 4.3%-46%, 2.3%-23%, 3.2%-14%, and 76%-98% of the total carbon content in particles. The specific UV-vis absorbance (SUVA254) of BrC fractions followed the order of MSOC > ASOC > HULISw > WSOC. The WSOC and MSOC fractions from the combustion of low maturity coal had relatively low SUVA254 and high SR values. The mass absorption efficiencies (MAE365) for ASOC and MSOC were higher than for WSOC, and WSOC and MSOC from low maturity coal combustion had relatively low levels of light absorption. These findings indicated that coal combustion is a potential source of atmospheric BrC and the abundance and light absorption of the coal combustion-derived BrC fractions were strongly dependent on the extraction methods used and the coal maturity rather than the coal shapes.

Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa.

Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion, and carcasses, and the stoichiometry and bioavailability of these inputs likely interact with characteristics of the recipient ecosystem to determine their effects on ecosystem function. We studied the influence of hippopotamus excretion/egestion and wildebeest carcasses, and their interactions with discharge, in the Mara River, Kenya. We measured nutrient dissolution and decomposition rates of wildlife inputs, the influence of inputs on nutrient concentrations and nutrient limitation in the river and the influence of inputs on biofilm growth and function in both experimental streams and along a gradient of inputs in the river. We found that hippopotamus excretion/egestion increases ammonium and coarse particulate organic matter in the river, and wildebeest carcasses increase ammonium, soluble reactive phosphorus, and total phosphorus. Concentrations of dissolved carbon and nutrients in the water column increased along a gradient of wildlife inputs and during low discharge, although concentrations of particulate carbon decreased during low discharge due to deposition on the river bottom. Autotrophs were nitrogen limited and heterotrophs were carbon limited and nitrogen and phosphorus colimited upstream of animal inputs but there was no nutrient limitation downstream of inputs. In experimental streams, hippo and wildebeest inputs together increased biofilm gross primary production (GPP) and respiration (R). These results differed in the river, where low concentrations of hippo inputs increased gross primary production (GPP) and respiration (R) of biofilms, but high concentrations of hippo inputs in conjunction with wildebeest inputs decreased GPP. Our research shows that inputs from large wildlife alleviate nutrient limitation and stimulate ecosystem metabolism in the Mara River and that the extent to which these inputs subsidize the ecosystem is mediated by the quantity and quality of inputs and discharge of the river ecosystem. Thus, animal inputs provide an important ecological subsidy to this river, and animal inputs were likely important in many other rivers prior to the widespread extirpation of large wildlife.

Monitoring Chemical Contamination of Medical Air Produced On-Site in a Healthcare Institution Using Low-Cost Air Quality Sensors

Medical air is used in hospitals for patients suffering from a wide range of conditions. This air is typically produced by pressurizing outdoor air on-site and supplying it to patients through a lengthy piping system. Thus, it may contain chemical pollution from outdoor sources, line contamination, or technical problems within the compressor system. Hospitals in North America are mandated to meet medical air quality standards established by the United States Pharmacopeia (USP), yet its quality is often unmonitored. Further, USP limits for many pollutants common in ambient air are unspecified while specified limits for some pollutants are far higher than common ambient air quality standards even though this air is intended for potentially vulnerable individuals. Finally, patient exposure is not determined and thus generally unknown. In this study a sensor-based air quality monitor was used in conjunction with portable instruments to measure the concentration of CO, CO2, NOx, O3, black carbon (BC), and ultrafine particles (UFP). Simultaneous measurements were made at the outdoor intake to the compression system and at the patient-room end of pipelines at a Canadian hospital. The results show a strong association between outdoor air pollution and the medical air quality for some pollutants, based on correlation analysis. The concentrations of CO and CO2 in the medical air were close to outdoor levels and followed the time-related changes in the outdoor concentrations. In contrast, the concentrations of NOx and O3 were lower than outdoor levels, and BC and UFP levels were generally below detection limit. Although the chemical pollutant concentrations were below the USP standards, this study indicates that outdoor sources of air pollution can strongly influence the chemical contamination of medical air.

The Mobile Observations of Ultrafine Particles (MOV-UP) Study: Winter 2018 Sampling

The Mobile ObserVations of Ultrafine Particles (MOV-UP) Study is a two-year project intended to quantify air quality impacts of air traffic for communities located near, and below the flight paths of the SeaTac airport. The study aims to assess ultrafine particle concentrations within 10 miles of the airport in the directions of aircraft take-offs and landings over the course of 4 seasons. To date, sampling has been completed for Winter 2018. Over this time period, 16 days of mobile sampling were conducted using a suite of mobile instruments capable of detecting particles between 10-20, 20-36 and &amp;gt;36 nm in diameter on a 10 second time-scale. Black carbon (BC) particle concentration was collected on the 10 second scale as well as the full range of particle size distribution from 10 nm to 1 µm on the 1 minute time scale. The mean wind direction during the drives was from the SW. There were two days with wind from the NW, which resulted in reversal of the landing and take-off direction at the airport. A varimax rotated principal component analysis was performed on the 1 minute particle size distribution data and BC concentration, normalized to total particle count. Three components accounted for 74% of the variance observed. The first component, explaining 33% of the variance, shows high loadings of particles with median diameter of less than 20.5 nm. The second component, explaining 23% of the variance, shows high loadings of particles with median diameter of greater than 20.5 nm. The third component, explaining 18% of the variance, shows high proportion of black carbon. The geographic distribution of the component scores suggests that the first component is associated with the aircraft flight path. This study demonstrates the ability of mobile monitoring to detect variations in on-road particle size distribution that may be associated not only with vehicular traffic, but also with distance to flight path within 10 miles of an urban airport.

Status of atmospheric particulate matter and black carbon concentration at Ashuganj in Brahmanbaria

Atmospheric particulate matter (PM) samples (both PM10 and PM2.5) were collected simultaneously from Midland Power Company Limited at Ashuganj, in Brahmanbaria to monitor the seasonal fluctuations of particulate matter and black carbon (BC) concentrations from air samples. Total eight samples were collected from January 2016 to December 2017 using two Air Metrics MiniVol samplers and the quantity of PM2.5 and PM10 was detected by weighing the filters before and after exposure. The concentration of PM (PM2.5 and PM10) and BC were analyzed at the laboratory of Chemistry Division, Atomic Energy Centre, Dhaka. The black carbon concentration from both PM2.5 and PM10 samples were also determined by reflectance measurement. The concentrations of PM2.5 varied from 12.2–145 μgm−3 where mean value was 67.09 μgm−3. The mean concentration of PM10 was 103.64 μgm−3 whereas the concentration ranged from 20.5–220 μgm−3. The ratios of PM2.5/PM10 fluctuated during different seasons, winter showed higher concentration and summer showed relatively lower concentration for both PM2.5 and PM10. Atmospheric dispersion due to increased wind speeds and wider mixing layer heights are recognized to be responsible for the lower PM concentrations in warmer months. The concentrations of BC in PM2.5 also varied from 2.44–33.4 μgm−3 and BC in PM10 varied from 4.51–57.2 μgm−3, respectively. The concentrations of particulate matter exceeded the Bangladesh National Ambient Air Quality Standard.J. Bangladesh Agril. Univ. 16(2): 232-236, August 2018

Global-scale evidence for the refractory nature of riverine black carbon

Wildfires and incomplete combustion of fossil fuel produce large amounts of black carbon. Black carbon production and transport are essential components of the carbon cycle. Constraining estimates of black carbon exported from land to ocean is critical, given ongoing changes in land use and climate, which affect fire occurrence and black carbon dynamics. Here, we present an inventory of the concentration and radiocarbon content (∆14C) of particulate black carbon for 18 rivers around the globe. We find that particulate black carbon accounts for about 15.8 ± 0.9% of river particulate organic carbon, and that fluxes of particulate black carbon co-vary with river-suspended sediment, indicating that particulate black carbon export is primarily controlled by erosion. River particulate black carbon is not exclusively from modern sources but is also aged in intermediate terrestrial carbon pools in several high-latitude rivers, with ages of up to 17,000 14C years. The flux-weighted 14C average age of particulate black carbon exported to oceans is 3,700 ± 400 14C years. We estimate that the annual global flux of particulate black carbon to the ocean is 0.017 to 0.037 Pg, accounting for 4 to 32% of the annually produced black carbon. When buried in marine sediments, particulate black carbon is sequestered to form a long-term sink for CO2.

High-performance solar steam generation of a paper-based carbon particle system

Solar steam generation systems have drawn widely interest for water purification to solve the fresh water shortage recently. In this work, a typical bi-layer system was prepared by daubing carbon particles on the air-laid paper (C-paper). The effects of the thickness of the air-laid paper film and the carbon particle concentration on the evaporation rate were investigated. Results turn out that: with the increase of the layers of papers, the evaporation rate increases initially until the paper film reaches a thickness of nine layers, and then saturates to a constant value. The thickness of nine layers of air-laid papers is optimum for enhancing the evaporation rate when more layers of papers could not further increase the evaporation rate. With the increase of the concentration of the carbon particles, the evaporation rate also initially increases rapidly and then gradually tends to a constant value, due to both of the limited ability of vapor passing through the top layer and the reduced light absorption capability of carbon particles induced by the stack of carbon particles. Applying the optimum thickness of the paper film and the optimum concentration of carbon particles in our C-paper system, the evaporation rate and the evaporation efficiency under a solar power illumination of 1 kW·m−2 can be respectively 0.964 kg·m−2·h−1 and 70%, which are close to the ones of the home-made CNT-paper and GO-paper systems. The C-paper is an excellent candidate for solar steam generation applications, thanks to its easy preparation, high efficiency and low cost.

Coccolithophore populations and their contribution to carbonate export during an annual cycle in the Australian sector of the Antarctic zone

Abstract. The Southern Ocean is experiencing rapid and relentless change in its physical and biogeochemical properties. The rate of warming of the Antarctic Circumpolar Current exceeds that of the global ocean, and the enhanced uptake of carbon dioxide is causing basin-wide ocean acidification. Observational data suggest that these changes are influencing the distribution and composition of pelagic plankton communities. Long-term and annual field observations on key environmental variables and organisms are a critical basis for predicting changes in Southern Ocean ecosystems. These observations are particularly needed, since high-latitude systems have been projected to experience the most severe impacts of ocean acidification and invasions of allochthonous species. Coccolithophores are the most prolific calcium-carbonate-producing phytoplankton group playing an important role in Southern Ocean biogeochemical cycles. Satellite imagery has revealed elevated particulate inorganic carbon concentrations near the major circumpolar fronts of the Southern Ocean that can be attributed to the coccolithophore Emiliania huxleyi. Recent studies have suggested changes during the last decades in the distribution and abundance of Southern Ocean coccolithophores. However, due to limited field observations, the distribution, diversity and state of coccolithophore populations in the Southern Ocean remain poorly characterised. We report here on seasonal variations in the abundance and composition of coccolithophore assemblages collected by two moored sediment traps deployed at the Antarctic zone south of Australia (2000 and 3700 m of depth) for 1 year in 2001–2002. Additionally, seasonal changes in coccolith weights of E. huxleyi populations were estimated using circularly polarised micrographs analysed with C-Calcita software. Our findings indicate that (1) coccolithophore sinking assemblages were nearly monospecific for E. huxleyi morphotype B/C in the Antarctic zone waters in 2001–2002; (2) coccoliths captured by the traps experienced weight and length reduction during summer (December–February); (3) the estimated annual coccolith weight of E. huxleyi at both sediment traps (2.11 ± 0.96 and 2.13 ± 0.91 pg at 2000 and 3700 m) was consistent with previous studies for morphotype B/C in other Southern Ocean settings (Scotia Sea and Patagonian shelf); and (4) coccolithophores accounted for approximately 2–5 % of the annual deep-ocean CaCO3 flux. Our results are the first annual record of coccolithophore abundance, composition and degree of calcification in the Antarctic zone. They provide a baseline against which to monitor coccolithophore responses to changes in the environmental conditions expected for this region in coming decades.

Identifying, counting, and characterizing superfine activated-carbon particles remaining after coagulation, sedimentation, and sand filtration

Superfine powdered activated carbon (SPAC; particle diameter ∼1 μm) has greater adsorptivity for organic molecules than conventionally sized powdered activated carbon (PAC). Although SPAC is currently used in the pretreatment to membrane filtration at drinking water purification plants, it is not used in conventional water treatment consisting of coagulation–flocculation, sedimentation, and rapid sand filtration (CSF), because it is unclear whether CSF can adequately remove SPAC from the water. In this study, we therefore investigated the residual SPAC particles in water after CSF treatment. First, we developed a method to detect and quantify trace concentration of carbon particles in the sand filtrate. This method consisted of 1) sampling particles with a membrane filter and then 2) using image analysis software to manipulate a photomicrograph of the filter so that black spots with a diameter >0.2 μm (considered to be carbon particles) could be visualized. Use of this method revealed that CSF removed a very high percentage of SPAC: approximately 5-log in terms of particle number concentrations and approximately 6-log in terms of particle volume concentrations. When waters containing 7.5-mg/L SPAC and 30-mg/L PAC, concentrations that achieved the same adsorption performance, were treated, the removal rate of SPAC was somewhat superior to that of PAC, and the residual particle number concentrations for SPAC and PAC were at the same low level (100–200 particles/mL). Together, these results suggest that SPAC can be used in place of PAC in CSF treatment without compromising the quality of the filtered water in terms of particulate matter contamination. However, it should be noted that the activated carbon particles after sand filtration were smaller in terms of particle size and were charge-neutralized to a lesser extent than the activated carbon particles before sand filtration. Therefore, the tendency of small particles to escape in the filtrate would appear to be related to the fact that their small size leads to a low destabilization rate during the coagulation process and a low collision rate during the flocculation and filtration processes.

Vertical Distributions of Coccolithophores, PIC, POC, Biogenic Silica, and Chlorophyll a Throughout the Global Ocean.

Coccolithophores are a critical component of global biogeochemistry, export fluxes, and seawater optical properties. We derive globally significant relationships to estimate integrated coccolithophore and coccolith concentrations as well as integrated concentrations of particulate inorganic carbon (PIC) from their respective surface concentration. We also examine surface versus integral relationships for other biogeochemical variables contributed by all phytoplankton (e.g., chlorophyll a and particulate organic carbon) or diatoms (biogenic silica). Integrals are calculated using both 100 m integrals and euphotic zone integrals (depth of 1% surface photosynthetically available radiation). Surface concentrations are parameterized in either volumetric units (e.g., m−3) or values integrated over the top optical depth. Various relationships between surface concentrations and integrated values demonstrate that when surface concentrations are above a specific threshold, the vertical distribution of the property is biased to the surface layer, and when surface concentrations are below a specific threshold, the vertical distributions of the properties are biased to subsurface maxima. Results also show a highly predictable decrease in explained‐variance as vertical distributions become more vertically heterogeneous. These relationships have fundamental utility for extrapolating surface ocean color remote sensing measurements to 100 m depth or to the base of the euphotic zone, well beyond the depths of detection for passive ocean color remote sensors. Greatest integrated concentrations of PIC, coccoliths, and coccolithophores are found when there is moderate stratification at the base of the euphotic zone.