Abstract. Despite growing evidence that the ocean is an important source of ice-nucleating particles (INPs) in the atmosphere, our understanding of the properties and concentrations of INPs in ocean surface waters remains limited. We have investigated INPs in sea surface microlayer and bulk seawater samples collected in the Canadian Arctic during the summer of 2016. Consistent with our 2014 studies, we observed that INPs were ubiquitous in the microlayer and bulk seawaters; heat and filtration treatments reduced INP activity, indicating that the INPs were likely heat-labile biological materials between 0.22 and 0.02 µm in diameter; there was a strong negative correlation between salinity and freezing temperatures; and concentrations of INPs could not be explained by chlorophyll a concentrations. Unique in the current study, the spatial distributions of INPs were similar in 2014 and 2016, and the concentrations of INPs were strongly correlated with meteoric water (terrestrial runoff plus precipitation). These combined results suggest that meteoric water may be a major source of INPs in the sea surface microlayer and bulk seawater in this region, or meteoric water may be enhancing INPs in this region by providing additional nutrients for the production of marine microorganisms. In addition, based on the measured concentrations of INPs in the microlayer and bulk seawater, we estimate that the concentrations of INPs from the ocean in the Canadian Arctic marine boundary layer range from approximately 10−4 to <10-6 L−1 at −10 ∘C.

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The objective of this study is to quantify the impact of freshwater stratification on the vertical gradients of partial pressure of CO2 (pCO2) and estimates of air-sea CO2 exchange in Hudson Bay during peak sea-ice melt and river runoff. During the spring of 2018, we sampled water in Hudson Bay and Hudson Strait for dissolved inorganic carbon, total alkalinity, salinity, the oxygen stable isotope ratio in the water (δ18O), and other ancillary data. The coastal domain and regions close to the ice edge had significant vertical concentration gradients of pCO2 across the top meters of the ocean due to the presence of a stratified fresh layer at the surface. The pCO2 and salinity in the central (where sea-ice melt was significant) and the southeast (where river runoff and sea-ice melt were significant) side of the bay generally increased with depth, with average gradients of 4.5 μatm m–1 and 0.5 m–1, respectively. Ignoring these gradients causes a significant error in calculating air-sea CO2 fluxes, especially when using shipboard underway systems that measure pCO2 at several meters below the sea surface. We found that the oceanic CO2 sink in Hudson Bay is underestimated by approximately 50% if underway pCO2 system measurements are used without correction. However, we observed that these gradients do not persist for more than 5 weeks following ice melt. We have derived a linear correction for underway pCO2 measurements to account for freshwater stratification during periods of 1–5 weeks after ice breakup. Given the lack of measurements in stratified Arctic waters, our results provide a road map to better estimates of the important role of these regions in global carbon cycles.

This study provides 6 years of high‐resolution underway measurements of the sea surface partial pressure of CO2 (pCO2sw), sea surface temperature, and salinity across the Canadian Arctic Archipelago (CAA). Observed pCO2sw varied regionally, with the northern and central channels of the CAA undersaturated in pCO2sw (with respect to the atmosphere), while the western regions were typically saturated to supersaturated in pCO2sw. This apparent spatial variability was caused to some extent by the timing of our ship transit through the CAA, as we also found a general seasonal trend of pCO2sw being undersaturated in the early summer, followed by saturation to supersaturation in late summer, and a return to undersaturation during the autumn. Sea surface temperature was significantly correlated with pCO2sw at various locations across the CAA, but we also observed the effects of other regional processes like upwelling, primary production, riverine input, and sea ice melt. These processes are linked to each other, and hence, it is impossible to pinpoint only one dominant factor controlling pCO2sw variability in the CAA. However, we found that sea ice dominates the seasonal cycle of all these processes, thus making the timing of sea ice breakup a useful predictor of pCO2sw variability in the CAA. We calculated an average net oceanic sink of 14 mmol CO2 · m−2 · day−1 for the CAA during the summer and autumn seasons, but caution that a more rigorous budgeting approach is required to fully account for biases in dates and locations of our measurements.

This investigation aimed to evaluate the effect of some biocontrol agents against the powdery mildew of Thompson seedless grapevines. The study was carried out during the two successive seasons (2016 and 2017) at a private organic vineyard orchard located at El Beheira Governorate, Egypt. Uncinula necator (syn. Erysiphe necator) is a fungus that causes powdery mildew of grapevine. It causes severe loss in yield quantity and quality. Application of different biocontrol agents, e.g., Trichoderma harzianum, T. hamatum, T. viride, and their combinations, as well as the Blight stop (Trichoderma spp.), a commercial biocide and micronic sulfur, was an attempt to control the disease. The mixture of the three Trichoderma spp. showed the highest efficacy (80.16 and 89.95%) of controlling the disease incidence and severity in the two seasons 2016 and 2017, respectively, followed by the treatment of Blight stop + micronic sulfur (77.12 and 84.02%), while micronic sulfur showed the lowest effect (57.02 and 41.32%). At all treatments, the yield was increased and the chemical characteristics, e.g., "total sugars, total soluble solids (TSS), total anthocyanin (% in mg/100 g F.W.), and total phenols (mg/g betties as gallic acid equivalent)" of berries were improved. On the contrary, the percentage of total acidity was decreased at all treatments than in the control.

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We present a year-round time series of dissolved methane (CH 4 ), along with targeted observations during ice melt of CH 4 and carbon dioxide (CO 2 ) in a river and estuary adjacent to Cambridge Bay, Nunavut, Canada. During the freshet, CH 4 concentrations in the river and ice-covered estuary were up to 240,000% saturation and 19,000% saturation, respectively, but quickly dropped by >100-fold following ice melt. Observations with a robotic kayak revealed that river-derived CH 4 and CO 2 were transported to the estuary and rapidly ventilated to the atmosphere once ice cover retreated. We estimate that river discharge accounts for >95% of annual CH 4 sea-to-air emissions from the estuary. These results demonstrate the importance of resolving seasonal dynamics in order to estimate greenhouse gas emissions from polar systems.Plain Language Summary The primary cause of recent global climate change is increasing concentrations of heat-trapping greenhouse gases in the atmosphere. Ongoing rapid Arctic climate change is affecting the annual cycle of sea ice formation and retreat; however, most published studies of greenhouse gases in Arctic waters have been conducted during ice-free, summertime conditions. In order to characterize seasonal variability in greenhouse gas distributions, we collected year-round measurements of the greenhouse gas methane (CH 4 ) in a coastal Arctic system near Cambridge Bay, Nunavut, Canada. We found that during the ice melt season, river water contains methane concentrations up to 2,000 times higher than the wintertime methane concentrations in the coastal ocean. We utilized a novel robotic kayak to conduct high-resolution mapping of greenhouse gas distributions during ice melt. From these data, we demonstrate that the river water containing elevated levels of methane and carbon dioxide (CO 2 ) flowed into the coastal ocean, and when ice cover melted, these greenhouse gases were rapidly emitted into the atmosphere. We estimate that in this system, more than 95% of all annual methane emissions from the estuary are driven by river inflow.

The effect of temperature on natural antioxidant changes in fresh and dried celery was studied. Celery herbs were dried at 50 and 90ᵒC using a laboratory scale hot air dryer. Fifteen phenolic components (gallic acid, protocatechuic acid, catechol , chlorogenic acid, syringic acid, caffeine , p-coumaric acid, ferulic acid, salycilic acid, cinnamic acid, chrysin, pyrogallol, ellagic acid , catechin and caffeic acid), five flavonoids components were identified in celery herbs (apignen, hesperitin, luteolin, quercetrin and rosmarinic) and three isoflavones components were identified in celery herbs (daidzein, genistein and isorhamnetin) were identified in celery herbs at 50 and 90ᵒC. The chemical constituents of apium graveolens volatile oil were determined, the results observed that eleven components were isolated from apium graveolens essential oil and classified into five chemical categories namely, monocyclic terpenes (78.24%), bicyclic terpenes (14.88%), aliphatic hydrocarbons (1.79%), ketones (0.19) and sesquiterpene (2.89%). These identified compounds accounted for 97.99 % of the composition of apium graveolens essential oil. Organoleptic evaluation of Apium graveolens represented the mean scores and their statistical analysis indication for color, aroma, taste, texture and overall acceptability for biscuit treatments mixed with different concentrations of dried Apium graveolens at 50°C and 90°C.