Suspended matter in the Caribbean Sea: A gravimetric analysis

Total suspended matter in the water column of the Caribbean was determined quantitatively by means of filtration through 0.45 μ membrane filters. Results show that prior values obtained by centrifuging methods are too low, and that the existence of a nepheloid layer cannot be gravimetrically demonstrated in the Caribbean.     

Disaster preparedness of local governments in Panay Island,Philippines

Disaster preparedness plans reduce future damages, but may lack testing to assess their effectiveness in operation. This study used the state-designed Local Government Unit Disaster Preparedness Journal: Checklist of Minimum Actions for Mayors in assessing the readiness to natural hazards of 92 profiled municipalities in central Philippines inhabited by 2.4 million people. Anchored on the Hyogo Framework for Action 2005–2015, it assessed their preparedness in 4 criteria—systems and structures, policies and plans, building competencies, and equipment and supplies. Data were analyzed using statistical package for social sciences, frequency count, percentage, and weighted mean. The local governments were found highly vulnerable to tropical cyclone and flood while vulnerable to earthquake, drought, and landslide. They were partially prepared regardless of profile, but the coastal, middle-earning, most populated, having the least number of villages, and middle-sized had higher levels of preparedness. Those highly vulnerable to earthquake and forest fire were prepared, yet only partially prepared to flood, storm surge, drought, tropical cyclone, tornado, tsunami and landslide. The diverse attitude of stakeholders, insufficient manpower, and poor database management were the major problems encountered in executing countermeasures. Appointing full-time disaster managers, developing a disaster information management system, massive information drive, organizing village-based volunteers, integrating disaster management into formal education, and mandatory trainings for officials, preparing for a possible major volcanic eruption and crafting a comprehensive plan against emerging emergencies like the COVID-19 pandemic may lead to a 360° preparedness.

     

Photochemistry of methane-water ices

We report a study on the broadband ultraviolet photolysis of methane-water ice mixtures, at low methane concentrations and temperatures relevant to the icy satellites of the outer Solar System. The photochemistry of these mixtures is dominated by the action of hydroxyl radicals on methane and the resulting products. This implies that, given sufficient exposure time, the methane will eventually be completely oxidized to carbon dioxide. The presence of methane inhibits the formation of hydrogen peroxide by serving as a trap for hydroxyl radicals. The distribution of photochemical products is broadly similar to that previously conducted using ion and electron sources, with some differences possibly attributable to the difference in radiation source. The results are applicable to a variety of icy bodies in the Solar System. On Enceladus, where methane mixed with water is measured in the plumes, methane in the surface ices is subject to oxidation and will eventually be converted to CO₂. The CH stretch feature detected in the VIMS spectra of the Enceladus surface ice suggests that methane is currently being supplied to the surface ice, likely from re-condensation of the plume gas.     

Limb Spicules from the Ground and from Space

We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series of five wavelengths observed in a very narrow band at Hα, on-band and at ± 0.035 nm and ± 0.070 nm (10 s at each wavelength) using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 Hα spicules, and 14 EUV spicules that overlapped Hα spicules; we found that their dynamical and morphological properties fit into the framework of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection mechanism for spicule generation, and with UV spicules being a sheath region surrounding the Hα spicules.     

Interfacial energy effects and the evolution of pore size distributions during quartz precipitation in sandstone

Pore size is usually thought to control the rate of crystal growth in porous geological media by determining the ratio of mineral surface area to fluid volume. However, theory suggests that in micron-scale to nanometer scale pores, interfacial energy (surface energy) effects can also become important. Interfacial energy typically increases the solubility of very small crystals growing in tiny pores, and when the fluid is close to equilibrium - as is often the case in geological systems - mineral precipitation could occur in relatively large pores, while in very small adjacent pores crystal growth might be suppressed. Such a mechanism would effectively restrict the reactive surface area of the porous medium, thereby reducing the bulk reaction rate. We investigated the pore size distributions in naturally cemented sandstone adjacent to an isolated stylolite and found that quartz precipitation was inhibited in pores smaller than 10 μm in diameter. Furthermore, we demonstrate that kinetic formulations which assume constant solubility cannot reproduce the observed pore size patterns in mineralized samples; by contrast, excellent fits with the data are obtained when interfacial energy effects are taken into account. Reaction rates in geological media determined in field studies can be orders of magnitude lower than those measured in laboratory experiments, and we propose that reduced reaction rates in porous media with micron and submicron-scale porosity could account for much of the apparent paradox.     

Spectral Irradiance and Phytoplankton Community Composition in a Blackwater-Dominated Estuary,Winyah Bay,South Carolina,USA

We investigated spatial and temporal relationships between spectral irradiance and phytoplankton community composition in the blackwater-influenced estuary Winyah Bay, South Carolina. Upstream, high concentrations of chromophoric dissolved organic matter (CDOM) absorbed blue wavelengths, resulting in a predominantly red light field. Green light prevailed downstream near the lower-CDOM coastal ocean, and phytoplankton community composition was distinct from upstream and mid-estuarine communities. Diatoms were abundant throughout the estuary in January, August, and October, cryptophytes dominated in July, and chlorophytes were abundant in December 2006. Only diatoms and chlorophytes showed significant covariation with the spectral attenuation coefficient (k(λ)): Chlorophytes showed positive relationships with k(442) (blue light) while diatoms were negatively correlated with k(442) and k(490) (violet to blue). Phytoplankton community composition in Winyah Bay appears to be driven by strong horizontal flow rather than gradients in spectral irradiance, but results indicate that water color is likely to play a greater role in blackwater-influenced estuaries with longer residence times.     

Estimated impacts of climate warming on California’s high-elevation hydropower

California’s hydropower system is composed of high and low elevation power plants. There are more than 150 high-elevation power plants, at elevations above 1,000 feet (300 m). Most have modest reservoir storage capacities, but supply roughly 74% of California’s in-state hydropower. The expected shift of runoff peak from spring to winter due to climate warming, resulting in snowpack reduction and increased snowmelt, might have important effects on power generation and revenues in California. The large storage capacities at low-elevation power plants provide flexibility to operations of these units under climate warming. However, with climate warming, the adaptability of the high-elevation hydropower system is in question as this system was designed to take advantage of snowpack, a natural reservoir. With so many high-elevation hydropower plants in California, estimation of climate warming effects by conventional simulation or optimization methods would be tedious and expensive. An Energy-Based Hydropower Optimization Model (EBHOM) was developed to facilitate practical climate change and other low-resolution system-wide hydropower studies, based on the historical generation data of 137 high-elevation hydropower plants for which the data were complete for 14 years. Employing recent historical hourly energy prices, the model was used to explore energy generation in California for three climate warming scenarios (dry warming, wet warming, and warming-only) over 14 years, representing a range of hydrologic conditions. The system is sensitive to the quantity and timing of inflows. While dry warming and warming-only climate changes reduce average hydropower revenues, wet warming could increase revenue. Re-operation of available storage and generation capacities help compensate for snowpack losses to some extent. Storage capacity expansion and to a lesser extent generation capacity expansion both increase revenues, although such expansions might not be cost-effective.     

Assessing the relationships between elevation and extreme precipitation with various durations in southern Taiwan using spatial regression models

A spatially autocorrelated effect exists in precipitation of a mountainous basin. This study examines the relationship between maximum annual rainfall and elevation in the Kaoping River Basin of southern Taiwan using spatial regression models (i.e. geographically weighted regression (GWR), simultaneous autoregression (SAR), and conditional autoregression (CAR)). Results show that the GWR, SAR, and CAR models can improve spatial data fitting and provide an enhanced estimation for the rainfall–elevation relationship than the ordinary least squares approach. In particular, GWR achieves the most accurate estimation, and SAR and CAR achieve similar performance in terms of the Akaike information criterion. The relationship between extreme rainfall and elevation for longer duration is more concise than that for short durations. Results show that the spatial distribution of precipitation depends on elevation and that rainfall patterns in study area are heterogeneous between the southwestern plain and the eastern mountain area. Copyright © 2011 John Wiley & Sons, Ltd.     

Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver

Five vertical profiles of silver (Ag) in the subarctic northeast Pacific are presented. Dissolved (< 0.2 μm) Ag concentrations within the surface mixed layer range from 6–25 pM, with the highest observed values at the most coastal site. Elevated Ag concentrations at this station are most likely attributable to the estuarine circulation in the Juan de Fuca Strait. One open-ocean station (P20) exhibited a strong surface Ag maximum. The station was located at the edge of a Haida eddy which raises the possibility that such eddies transport Ag seaward from the coastal zone. Ag concentrations in the deep waters ranged from 60–80 pM. These measurements are consistent with other recent Ag data collected in the Pacific. Ag profiles throughout the Pacific Ocean yield a strong positive correlation between Ag concentration and dissolved silicic acid concentration. However, Ag is depleted relative to silicic acid at intermediate depths where dissolved O₂ concentrations are low, implying a possible removal of Ag from oxygen-depleted waters by scavenging and/or precipitation.     

Downstream effects of water withdrawal in a small,high-gradient basin: Erosion and deposition on the Skokomish River delta

This paper analyzes downstream effects of freshwater flow diversion from a small, active-continental-margin river basin. The Skokomish River delta, a tributary estuary to Hood Canal in Washington state, receives drainage from the southeastern side of the Olympic Mountains. Its drainage basin is steep, and rainfall is high. Since completion of two dams in 1930, approximately 40% of the annual average runoff of the entire system has been diverted from the North Fork Skokomish River for power production; this water does not pass through the lower river or over the delta. Extensive logging has occurred in the remainder of the basin. Comparison of prediversion (1885) and postdiversion (1941 and 1972) bathymetric surveys suggest that deposition (about 0.013 m yr^?1 to 0.022 m yr^?1) has occurred on most of the inner delta and erosion (up to 0.011 m yr^?1 to 0.033 m yr^?1) on much of the outer delta. More rapid postconstruction deposition occurred within the river mouth itself, where the 1926 to 1941 deposition rate was 0.04–0.11 m yr^?1. Nine of 12 historical bathymetric change cross-sections show steepening of the delta surface, two are neutral, and one shows aggradation. This steepening has apparently been caused by a loss of sediment transport capacity in the lower river and estuary combined with steady or increased (due to logging) sediment supply. Although the total area of unvegetated tidal flats has decreased by only about 2%, there has been a 15–19% loss of highly productive low intertidal surface area and an estimated 17% loss of eelgrass (Zostera marina) habitat. A reduction in the size of mesohaline mixing zone has also occurred. These habitat losses are similar to those observed elsewhere in the world in larger river basins that have suffered water withdrawals of the same magnitude, but their impacts either cannot be evaluated or understood casually through consideration of simple measures like changes in total estuarine deltaic area. Evaluation of estuarine effects of anthropogenic modification must, therefore, include consideration of both changes in habitat function and in the physical processes. These must be evaluated within the totality of the river basin-estuary system that cause these changes. In this case, sediment transport constitutes the critical link between fluvial alterations and the remote downstream, estuarine consequences thereof.