The sea-surface microlayer (SML) has different physical, chemical and biological properties compared to the subsurface water, with an enrichment of organic matter i.e., dissolved organic matter ...including UV absorbing humic substances, fatty acids and many others. Here we present experimental evidence that dissolved organic matter, such as humic acids, when exposed to sunlight, can photosensitize the chemical conversion of linear saturated fatty acids at the air-water interface into unsaturated functionalized gas phase products (i.e. saturated and unsaturated aldehydes and acids, alkenes and dienes,...) which are known precursors of secondary organic aerosols. These functionalized molecules have previously been thought to be of biological origin, but here we demonstrate that abiotic interfacial photochemistry has the potential to produce such molecules. As the ocean is widely covered by the SML, this new understanding will impact on our ability to describe atmospheric chemistry in the marine environment.
Abstract Background The Dutch Health Council recently recommended the introduction of a colorectal cancer (CRC) screening programme by faecal occult blood testing (FOBT) for individuals aged 55–75 at ...population risk of CRC. Individuals at an increased familial CRC risk (⩾2 times population risk) should be identified at a younger age, so they and their relatives can receive earlier, more intensive surveillance instead of FOBT. Aims To determine the percentage of participants with a positive FOBT in a CRC screening programme with an increased familial CRC risk. Methods In a population-based study, 10,569 individuals aged 50–75 received an FOBT. Individuals with a positive FOBT were invited for colonoscopy and familial risk assessment. Participants with an average familial CRC risk were compared to those with an increased risk. Increased familial CRC risk was defined as a cumulative lifetime risk of CRC of at least 10%. Results Of 6001 participants, 430 had a positive FOBT, of whom 324 (63% males; mean age 63 years) completed colonoscopy and familial risk assessment. CRC ( n = 22) and/or advanced adenomas ( n = 122) were found in 133 participants. Familial CRC risk was increased in 6% of participants with a positive FOBT. No significant differences were found between participants with an average versus an increased familial CRC risk. Conclusion Six percent of participants with a positive FOBT had an increased familial CRC risk. Identifying at-risk participants enables them and their relatives to undergo regular colonoscopies. Adding familial risk assessment to FOBT screening may thus prevent a substantial number of CRCs.
Agro-industrial areas are frequently affected by various sources of atmospheric pollutants that have a negative impact on public health and ecosystems. However, air quality in these areas is ...infrequently monitored because of their smaller population compared to large cities, especially in developing countries. The Cauca River valley (CRV) is an agro-industrial region in southwestern Colombia, where a large fraction of the area is devoted to sugarcane and livestock production. The CRV is also affected by road traffic and industrial emissions. This study aims to elucidate the chemical composition of particulate matter fine mode (PM2.5) and to identify the main pollutant sources before source attribution. A sampling campaign was carried out at a representative site in the CRV region, where daily averaged mass concentrations of PM2.5 and the concentrations of water-soluble ions, trace metals, organic and elemental carbon, and various fractions of organic compounds (carbohydrates, n alkanes, and polycyclic aromatic hydrocarbons – PAHs) were measured. The mean PM2.5 was 14.4±4.4 µg m−3, and the most abundant constituent was organic material (52.7 % ± 18.4 %), followed by sulfate (12.7 % ± 2.8 %), and elemental carbon (7.1 % ± 2.5 %), which indicates the presence of secondary aerosol formation and incomplete combustion. Levoglucosan was present in all samples, with a mean concentration of (113.8±147.2 ng m−3), revealing biomass burning as a persistent source. Mass closure using the elemental carbon (EC) tracer method explained 88.4 % on PM2.5, whereas the organic tracer method explained 70.9 % of PM2.5. We attribute this difference to the lack of information of specific organic tracers for some sources, both primary and secondary. Organic material and inorganic ions were the dominant groups of species (79 % of PM2.5). OMprim and OMsec contribute 24.2 % and 28.5 % to PM2.5. Inorganic ions as sulfate, nitrate, and ammonia constitute 19.0 %, EC 7.1 %, dust 3.5%, particle-bounded water (PBW) 5.3 %, and trace element oxides (TEOs), 0.9 % of PM2.5. The aerosol was acidic, with a pH of 2.5±0.4, mainly because of the abundance of organic and sulfur compounds. Diagnostic ratios and tracer concentrations indicate that most PM2.5 was emitted locally and had contributions of both pyrogenic and petrogenic sources, that biomass burning was ubiquitous during the sampling period and was the main source of PAHs, and that the relatively low PM2.5 concentrations and mutagenic potentials are consistent with low-intensity, year-long biomass burning (BB) and sugarcane pre-harvest burning in the CRV.
Measurements of free amino acids (FAAs) in the marine environment to
elucidate their transfer from the ocean into the atmosphere, to marine
aerosol particles and to clouds, were performed at the ...MarParCloud (marine biological production,
organic aerosol particles and marine clouds: a process chain) campaign
at the Cabo Verde islands in autumn 2017. According to physical and chemical
specifications such as the behavior of air masses, particulate MSA
concentrations and MSA∕sulfate ratios, as well as particulate mass
concentrations of dust tracers, aerosol particles predominantly of marine
origin with low to medium dust influences were observed. FAAs were
investigated in different compartments: they were examined in two types of
seawater underlying water (ULW) and in the sea surface microlayer (SML), as
well as in ambient marine size-segregated aerosol particle samples at two
heights (ground height based at the Cape Verde Atmospheric Observatory, CVAO, and
at 744 m height on Mt. Verde) and in cloud water using concerted
measurements. The ∑FAA concentration in the SML varied between
0.13 and 3.64 µmol L−1, whereas it was between 0.01 and 1.10 µmol L−1 in the ULW; also, a strong enrichment of ∑FAA
(EFSML: 1.1–298.4, average of 57.2) was found in the SML. In the
submicron (0.05–1.2 µm) aerosol particles at the CVAO, the
composition of FAAs was more complex, and higher atmospheric concentrations
of ∑FAA (up to 6.3 ng m−3) compared to the supermicron
(1.2–10 µm) aerosol particles (maximum of 0.5 ng m−3) were
observed. The total ∑FAA concentration (PM10) was between
1.8 and 6.8 ng m−3 and tended to increase during the campaign. Averaged
∑FAA concentrations in the aerosol particles on Mt. Verde were
lower (submicron: 1.5 ng m−3; supermicron: 1.2 ng m−3) compared to
the CVAO. A similar contribution percentage of ∑FAA to dissolved
organic carbon (DOC) in the seawater (up to 7.6 %) and to water-soluble
organic carbon (WSOC) in the submicron aerosol particles (up to 5.3 %)
indicated a related transfer process of FAAs and DOC in the marine
environment. Considering solely ocean–atmosphere transfer and neglecting atmospheric
processing, high FAA enrichment factors were found in both aerosol particles
in the submicron range (EFaer(∑FAA): 2×103–6×103) and medium enrichment factors in the
supermicron range (EFaer(∑FAA): 1×101–3×101). In addition, indications for a biogenic FAA
formation were observed. Furthermore, one striking finding was the high and
varying FAA cloud water concentration (11.2–489.9 ng m−3), as well as
enrichments (EFCW: 4×103 and 1×104 compared to the SML and ULW, respectively), which were reported here for
the first time. The abundance of inorganic marine tracers (sodium,
methanesulfonic acid) in cloud water suggests an influence of oceanic
sources on marine clouds. Finally, the varying composition of the FAAs in the
different matrices shows that their abundance and ocean–atmosphere transfer
are influenced by additional biotic and abiotic formation and degradation
processes. Simple physicochemical parameters (e.g., surface activity) are
not sufficient to describe the concentration and enrichments of the FAAs in
the marine environment. For a precise representation in organic matter (OM)
transfer models, further studies are needed to unravel their drivers and
understand their composition.
Carbohydrates, originating from marine microorganisms, enter the atmosphere as part of sea spray aerosol (SSA) and can influence fog and cloud microphysics as cloud condensation nuclei (CCN) or ...ice-nucleating particles (INP). Particularly in the remote Arctic region, significant knowledge gaps persist about the sources, the sea-to-air transfer mechanisms, atmospheric concentrations, and processing of this substantial organic group. In this ship-based field study conducted from May to July 2017 in the Fram Strait, Barents Sea, and central Arctic Ocean, we investigated the sea-to-air transfer of marine combined carbohydrates (CCHO) from concerted measurements of the bulk seawater, the sea surface microlayer (SML), aerosol particles and fog. Our results reveal a wide range of CCHO concentrations in seawater (22–1070 µg L−1), with notable variations among different sea-ice-related sea surface compartments. Enrichment factors in the sea surface microlayer (SML) relative to bulk water exhibited variability in both dissolved (0.4–16) and particulate (0.4–49) phases, with the highest values in the marginal ice zone (MIZ) and aged melt ponds. In the atmosphere, CCHO was detected in super- and submicron aerosol particles (CCHOaer,super: 0.07–2.1 ng m−3; CCHOaer,sub: 0.26–4.4 ng m−3) and fog water (CCHOfog,liquid: 18–22 000 µg L−1; CCHOfog,atmos: 3–4300 ng m−3). Enrichment factors for sea–air transfer varied based on assumed oceanic emission sources. Furthermore, we observed rapid atmospheric aging of CCHO, indicating both biological/enzymatic processes and abiotic degradation. This study highlights the diverse marine emission sources in the Arctic Ocean and the atmospheric processes shaping the chemical composition of aerosol particles and fog.
Ice-nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (N.sub.INP) are not well characterized, and, ...although there is some understanding of their sources, it is still unclear to what extend different sources contribute or if all sources are known. In this work, we examined properties of INPs at Cabo Verde (a.k.a. Cape Verde) from different environmental compartments: the oceanic sea surface microlayer (SML), underlying water (ULW), cloud water and the atmosphere close to both sea level and cloud level.
This study examines carbohydrates, amino acids, and lipids as important contributors to organic carbon (OC) in the tropical Atlantic Ocean at the Cape Verde Atmospheric Observatory (CVAO). The above ...compounds were measured in both surface seawater and in ambient sub-micron aerosol particles to investigate their sea-to-air transfer, including their enrichment in the sea surface microlayer (SML), potential atmospheric in situ formation or degradation, and their oceanic contribution to the ambient marine aerosol particles.
The embodied capital theory states that the extended juvenile period has enabled human foragers to acquire the complex foraging skills and knowledge needed to obtain food. Yet we lack detailed data ...on how forager children develop these skills and knowledge. Here, we examine the seasonal diet composition, foraging behavior, and botanical knowledge of Mbendjele BaYaka forager children in the Republic of the Congo. Our data, acquired through long-term observations involving full-day focal follows, show a high level of seasonal fluctuation in diet and foraging activities of BaYaka children, in response to the seasonal availability of their food sources. BaYaka children foraged more than half of the time independent from adults, predominantly collecting and eating fruits, tubers, and seeds. For these most-consumed food types, we found an early onset of specialization of foraging skills in children, similar to the gendered division in foraging in adults. Specifically, children were more likely to eat fruit and seed species when there were more boys and men in the group, and girls were more likely than boys to collect tuber species. In a botanical knowledge test, children were more accurate at identifying plant food species with increasing age, and they used fruits and trunks for species identification, more so than using leaves and barks. These results show how the foraging activities of BaYaka children may facilitate the acquisition of foraging skills and botanical knowledge and provide insights into the development of embodied capital. Additionally, BaYaka children consumed agricultural foods more than forest foods, probably reflecting BaYaka’s transition into a horticultural lifestyle. This change in diet composition may have significant consequences for the cognitive development of BaYaka children.
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