Emitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here ...we present a comprehensive data set of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol-1 (30% uncertainty) and, complemented with additional field campaigns, this data set confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75 % to the IO budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL.
High‐resolution surface measurements of dimethylsulfide (DMS), chlorophyll a fluorescence, and the efficiency of photosystem II were conducted together with temperature and salinity along five ...eastward sections in the tropical and subtropical Atlantic, Indian, and Pacific Oceans. Analysis of variability length scales revealed that much of the variability in DMS concentrations occurs at scales between 15 and 50 km, that is, at the lower edge of mesoscale dynamics, decreasing with latitude and productivity. DMS variability was found to be more commonly related to that of phytoplankton‐related variables than to that of physical variables. Unlike phytoplankton physiological data, DMS did not show any universal diel pattern when using the normalized solar zenith angle as a proxy for solar time across latitudes and seasons. The study should help better design sampling and computing schemes aimed at mapping surface DMS and phytoplankton distributions, taking into account latitude and productivity.
Key Points
The variability in open ocean DMS concentrations occurs at the submesoscale
DMS and phytoplankton patchiness increase with productivity
No single pattern of diel variation in DMS is valid for the global ocean
Ship-based Multi-Axis Differential Optical Absorption Spectroscopy measurements of iodine monoxide (IO) and atmospheric and seawater Gas Chromatography-Mass Spectrometer observations of methyl iodide ...(CH3I) were made in the Eastern Pacific marine boundary layer during April 2010 as a part of the HaloCarbon Air Sea Transect-Pacific (HaloCAST-P) scientific cruise. The presence of IO in the open ocean environment was confirmed, with a maximum differential slant column density of 5 × 1013 molecules cm−2 along the 1° elevation angle (corresponding to approximately 1 pptv) measured in the oligotrophic region of the Southeastern Pacific. Such low IO mixing ratios and their observed geographical distribution are inconsistent with satellite estimates and with previous understanding of oceanic sources of iodine. A strong correlation was observed between reactive iodine (defined as IO + I) and CH3I, suggesting common sources. In situ measurements of meteorological parameters and physical ocean variables, along with satellite-based observations of Chlorophyll a (Chl a) and Chromophoric Dissolved Organic Matter (CDOM) were used to gain insight into the possible sources of iodine in this remote environment. Surprisingly, reactive iodine showed a negative correlation (> 99% confidence) to Chl a and CDOM across the cruise transect. However, a significant positive correlation (> 99% confidence) with sea surface temperature (SST) and salinity instead suggests a widespread abiotic source related to the availability of aqueous iodine and to temperature.
The input of new nitrogen into the euphotic zone constrains the export of organic carbon to the deep ocean and thereby the biologically mediated long-term CO2 exchange between the ocean and ...atmosphere. In low-latitude open-ocean regions, turbulence-driven nitrate diffusion from the ocean's interior and biological fixation of atmospheric N2 are the main sources of new nitrogen for phytoplankton productivity. With measurements across the tropical and subtropical Atlantic, Pacific and Indian oceans, we show that nitrate diffusion (171±190 μmol m(-2) d(-1)) dominates over N2 fixation (9.0±9.4 μmol m(-2) d(-1)) at the time of sampling. Nitrate diffusion mediated by salt fingers is responsible for ca. 20% of the new nitrogen supply in several provinces of the Atlantic and Indian Oceans. Our results indicate that salt finger diffusion should be considered in present and future ocean nitrogen budgets, as it could supply globally 0.23-1.00 Tmol N yr(-1) to the euphotic zone.
The distribution and biological cycling of the climate active trace gas dimethylsulfide (DMS) and its algal precursor dimethylsulfoniopropionate (DMSP) were characterized at 20 stations across the ...Canadian High Arctic during fall 2007. Transformation rates of DMSP and production rates of DMS from dissolved DMSP (DMSPd) were measured during 3 h onboard incubations with radioactively labeled 35S‐DMSP. Particulate DMSP (DMSPp) in surface waters varied between 2 and 39 nmol L−1 and increased with chlorophyll a (Chl a) concentrations (r = 0.84). DMS concentrations in surface waters ranged from 0.05 to 0.8 nmol L−1 and were positively correlated with DMSPp (r = 0.89) and Chl a (r = 0.74). The DMSPd loss rate constant varied from 0.01 to 0.14 h−1 and was also positively correlated with Chl a concentrations (r = 0.67). The turnover time of the DMSPd pool varied between 0.3 and 3.4 days (mean = 0.96 day). Bacterial DMS production varied between 0.01 and 0.51 nmol L−1 d−1 (mean = 0.14 nmol L−1 d−1). Assuming local steady state conditions at the time scale of a day, the turnover time of the DMS pool based only on production from DMSPd was ∼6 days at the sampling stations. This long turnover time suggests that DMS production was dominated by nonbacterial processes during our study. Our results show that DMS production could persist at low rates in late fall under ice‐free conditions. The magnitude of this production appears to be limited by the low algal and bacterial production prevailing at that time.
Key Points
Low but significant DMSP microbial uptake takes place in late fall in the Arctic
Microbial DMSP uptake appears to be limited by bacterial production
DMS production is low but significant under ice‐free conditions in late fall
Films like Firefox, Surrogates, and Avatar have explored the possibilities of using brain-computer interfaces (BCIs) to control machines and replacement bodies with only thought. Real world BCIs have ...made great progress toward that end. Invasive BCIs have enabled monkeys to fully explore 3-D space using neuroprosthetics. However, noninvasive BCIs have not been able to demonstrate such mastery of 3-D space. Here, we report our work, which demonstrates that human subjects can use a noninvasive BCI to fly a virtual helicopter to any point in a 3-D world. Through use of intelligent control strategies, we have facilitated the realization of controlled flight in 3-D space. We accomplished this through a reductionist approach that assigns subject-specific control signals to the crucial components of 3-D flight. Subject control of the helicopter was comparable when using either the BCI or a keyboard. By using intelligent control strategies, the strengths of both the user and the BCI system were leveraged and accentuated. Intelligent control strategies in BCI systems such as those presented here may prove to be the foundation for complex BCIs capable of doing more than we ever imagined.
Emission of the trace gas dimethylsulphide (DMS) from the ocean influences the chemical and optical properties of the atmosphere, and the olfactory landscape for foraging marine birds, turtles and ...mammals. DMS concentration has been seen to vary across seasons and latitudes with plankton taxonomy and activity, and following the seascape of ocean's physics. However, whether and how does it vary at the time scales of meteorology and day-night cycles is largely unknown. Here we used high-resolution measurements over time and depth within coherent water patches in the open sea to show that DMS concentration responded rapidly but resiliently to mesoscale meteorological perturbation. Further, it varied over diel cycles in conjunction with rhythmic photobiological indicators in phytoplankton. Combining data and modelling, we show that sunlight switches and tunes the balance between net biological production and abiotic losses. This is an outstanding example of how biological diel rhythms affect biogeochemical processes.
Carbon materials are on the rise owing to their outstanding properties compared with their metal-based homologs. This interest triggered intensive research toward the preparation of carbon-based ...nanostructures including those doped with heteroatoms, among which nitrogen-containing carbon materials are the most ubiquitous. Biomass and biowastes stand as sustainable and cost-effective precursors to access tunable carbon-based nanomaterials. Excitingly, chitosan—an aminopolysaccharide marine waste—displays additional advantages of distinctively featuring nitrogen in the biopolymer skeleton, thereby avoiding the tedious step of nitrogen enrichment of the carbonaceous framework that often necessitates the use of exogenous chemicals. This review sheds light on the opportunities offered by transforming chitosan into nitrogen-containing carbon framework, including porous carbon, graphene, and carbon dots derivatives. The templating effect of chitosan, its strong interaction with metal species, and its shaping in different forms provide multifaceted possibilities for the rational design of advanced functional carbon nanomaterials. Overall, this fashionable trend in material science is expected to trigger a new debate around the most efficient way in which biomass and biowastes should be transformed, sustainability could be improved, and high-value added materials could be obtained.
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•Melt infiltration is efficient for the dispersion of nickel in micro-mesoporous silica.•Properties of the secondary intra-wall porosity is decisive in dispersing Ni phase.•A high ...degree of interconnectivity between the two porosities is in favor of NPs formation in the intra-wall pores.•Excellent properties for cinnamaldehyde and 5-HMF hydrogenations are obtained over intra-wall pore confined NPs.
Effective encapsulation strategies are highly sought-after in heterogeneous catalysis for preparing highly active and stable metal (oxide) nanocatalysts. Herein, we report an optimized Melt Infiltration (MI) procedure to confine nickel(oxide) nanoparticles (NPs) into hierarchical microporous-mesoporous scaffolds. Three SBA-15 silicas were synthesized in order to obtain different degrees of interconnectivity between the main mesopores. The impact of the SBA-15 pore characteristics, i.e., this interconnectivity, also named secondary intra-wall porosity (IWP), on the final nickel (oxide) NPs size and localization has been specifically investigated. Using MI, which consisted in the diffusion of the precursor in the liquid state inside the porosity of the support in the presence of the native surfactant occluding the pores, a selective localization of the NiO NPs inside the IWP was obtained, without large NPs plugging the main mesopores if IWP pores connecting the main mesopores do exist. When IWP – selective localization – occurs for the NPs, they show a size directly depending on the IWP dimensions. The obtained materials were tested, after reduction, in the hydrogenation reactions of cinnamaldehyde and 5-hydroxymethylfurfural. The catalytic results underline the positive effect of IWP - confinement of NPs to obtain and maintain an elevated dispersion of the metallic Ni active phase and to reach a high catalytic activity in hydrogenation under mild reaction conditions.
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