Hypoxia in Manila Bay, Philippines during the northeast monsoon

Herein we present results from one of the first extensive bay-wide oceanographic surveys of Manila Bay, wherein 31 stations were sampled during the northeast monsoon (cold and dry season). A band of hypoxic bottom water (dissolved oxygen<2.8 mg/L) spanned the midsection of the bay from east to west. Bottom nitrate concentrations (5.7-16.8 μM; avg. 11.1 μM) and total organic carbon values in sediments (1.7-3.1%; avg. 2.4%) were high in the midsection, which coincided with the band of hypoxic bottom water. Physical processes and site-specific accumulation of organic material likely lead to hypoxic conditions in Manila Bay, even during the northeast monsoon period when the water column is relatively well mixed. The results of this study complement the previously reported widespread hypoxia that occurs during the rainy season. Thus, hypoxia may be pervasive in the bay throughout the year, although it varies in intensity and spatial extent.     

Nutrient inputs from submarine groundwater discharge on the Santiago reef flat, Bolinao, Northwestern Philippines

Submarine groundwater discharge (SGD) on the reef flat of Bolinao, Pangasinan (Philippines) was mapped using electrical resistivity, 222Rn, and nutrient concentration measurements. Nitrate levels as high as 126 μM, or 1-2 orders of magnitude higher than ambient concentrations, were measured in some areas of the reef flat. Nutrient fluxes were higher during the wet season (May-October) than the dry season (November-April). Dissolved inorganic nitrogen (DIN=NO3+NO2+NH4) and soluble reactive phosphorus (SRP) fluxes during the wet season were 4.4 and 0.2 mmoles m(-2) d(-1), respectively. With the increase population size and anthropogenic activities in Bolinao, an enhancement of SGD-derived nitrogen levels is likely. This could lead to eutrophic conditions in the otherwise oligotrophic waters surrounding the Santiago reef flat.     

Anodic Oxidation as Green Alternative for Removing Diethyl Phthalate from Wastewater Using Pb/PbO2 and Ti/SnO2 Anodes

The electrochemical oxidation (EO) of diethyl phthalate (DEP) in aqueous solution was studied at Pb/PbO₂ and Ti/SnO₂ anode materials under galvanostatic‐experimental conditions. Results obtained clearly demonstrated that the anode plays a significant role for the optimization of the oxidation process, deciding the mechanisms and by‐products formed. DEP and by‐products of oxidation were also analyzed during various stages of the electrolysis reaction by HPLC and GC/MS techniques. Before the analysis by GC/MS technique, the samples were treated by solid phase microextraction (SPME) in order to concentrate the compounds from the reaction solution and identify all electrolysis intermediates. Current efficiencies (instantaneous current efficiency; ICE and total current efficiency; TCE) achieved during EO experiments were dependent on anode used and current density (20–40 mA cm^?2) at 40°C. The results obtained demonstrated that the environmental electrochemical methods can be a feasible alternative for the wastewater treatment containing hazardous phthalates.     

Galaxy evolution in Hickson compact groups: the role of ram-pressure stripping and strangulation

Galaxies in compact groups tend to be deficient in neutral hydrogen compared to isolated galaxies of similar optical properties. In order to investigate the role played by a hot intragroup medium (IGM) for the removal and destruction of H  i in these systems, we have performed a Chandra and XMM–Newton study of eight of the most H  i deficient Hickson compact groups. Diffuse X-ray emission associated with an IGM is detected in four of the groups, suggesting that galaxy–IGM interactions are not the dominant mechanism driving cold gas out of the group members. No clear evidence is seen for any of the members being currently stripped of any hot gas, nor for galaxies to show enhanced nuclear X-ray activity in the X-ray bright or most H  i deficient groups. Combining the inferred IGM distributions with analytical models of representative disc galaxies orbiting within each group, we estimate the H  i mass-loss due to ram-pressure and viscous stripping. While these processes are generally insufficient to explain observed H  i deficiencies, they could still be important for H  i removal in the X-ray bright groups, potentially removing more than half of the interstellar medium in the X-ray bright HCG 97. Ram pressure may also have facilitated strangulation through the removal of galactic coronal gas. In X-ray undetected groups, tidal interactions could be playing a prominent role, but it remains an open question whether they can fully account for the observed H  i deficiencies.     

The last major earthquakes along the Magallanes–Fagnano fault system recorded by disturbed trees (Tierra del Fuego,South America)

Forests situated above active fault zones may record hillslope evolution, thus holding information about recent seismic events. Lenga trees (Nothofagus pumilio) extend across the Magallanes–Fagnano fault system (MFFS), the active transform boundary between the South American and Scotia plates. Coseismic surface ruptures along the fault scarp tilt trees located uphill. During the interseismic period, tree growth curves the trunks. Annual tree rings from the study area show abrupt changes from concentric to asymmetric, allowing the timing of major historical earthquakes to be established. In this case, tree‐ring analysis suggests rupture on the MFFS fault scarp in 1883 ± 5 and 1941 ± 10, coinciding with the February 1, 1879 (Modified Mercalli Scale, VI) and the December 17, 1949 (Ms 7.8) earthquakes in Tierra del Fuego. Our results provide evidence that this fault system was the source of these earthquakes, which has implications for seismic hazard in the study region.     

A Reliability-Based Evaluation of the Effects of Geometry on Levee Underseepage Potential

Levee foundations along meandering rivers are often modeled in seepage analyses with simplified models consisting of two layers having uniform thickness and soil properties. While this may simplify the analysis and allow for use of simplified reliability methods, it is important to realize the limitations of these simplifying assumptions. Due to the complex geomorphic regime that is often encountered in the fluvial environment, levee foundation geometry can range from simple to very complex. Variations in layer thickness and continuity affect the pore pressure and seepage regime and, consequently, affect the potential for internal erosion of the foundation soils. A study has been performed to assess the effects of complex subsurface geometry on the susceptibility of levees to underseepage related internal erosion. Reliability-based internal erosion analyses have been performed on eight hypothetical levee profiles using two analytical methods. The first-order second-moment-blanket theory (FOSM-BT) method applies a simplified reliability assessment technique to the US Army Corps of Engineers “Blanket Theory” equations. This method requires that the analysis profile be simplified to meet the requirements of the equations and places limitations on how the uncertainty of the various input parameters is modeled. The more complex response surface-Monte Carlo simulation method is capable of modeling more complex geometries and multiple failure modes and is flexible in how uncertainty of the various input parameters are modeled. The results of the two methods are compared to evaluate the effectiveness of the FOSM-BT in evaluating internal erosion potential in increasingly complex levee foundation conditions.     

Hydrochemical and isotopic characterization of the hydrological budget of a MAB Reserve: Mar Chiquita lagoon,province of Buenos Aires,Argentina

Mar Chiquita is a coastal lagoon located in the Argentine Buenos Aires province in South America. The aim of this study was to perform a hydrochemical and stable isotopes characterization in order to better the understanding of the hydrology of the Mar Chiquita lagoon’s catchment and its water budget. Groundwater samples were taken from 144 wells and 21 samples from main streams, and seven lagoon water samples were also collected. Chemical analyses were carried out using standard laboratory methods, and isotopic determinations were made through laser spectroscopy using a DLT-100 liquid–water isotope analyzer. Hydrochemical analysis permits a general classification of groundwater and streamwater as sodium bicarbonate waters, while the lagoon chemical composition shows an evolution toward seawater composition, from the north to its mouth, which is located southerly. Isotopic data show a source of aquifer recharge from rainfall and a groundwater domain into the streams’ flow. Three main components can be recognized as end members in a plot of electrical conductivity (EC) versus δ¹⁸O: seawater, streamwater and groundwater. Obtained EC values for groundwater in the discharge zone (EC average value = 3,516 μS/cm) allow minimizing its direct contribution and to take into consideration two dominating end members: streamwater and seawater. Mar Chiquita lagoon’s water falls close to the line between streamwater and seawater end members according to its EC and δ¹⁸O. The obtained seawater proportion for these samples ranges from 84 % in the lagoon’s mouth to around 0 % in the more distal area.     

Distribution of cyanobacteria and other picophytoplankton in the western North Pacific Ocean,Summer 1989

Cell densities of phycoerythrin-fluorescing cyanobacteria and other chlorophyll-fluorescing picophytoplankton in the 0.2–2.0 µm size fraction were investigated, using an epifluorescence microscope, in the western North Pacific Ocean (36.5–44.0 °N, 155.0°E) in the summer of 1989. Cyanobacteria were most abundant in the surface of the subtropical water (36.5–38.0°N) and less in the northern sea area (39.5–44.0°N). The cell density of other picophytoplankton was, however, high in the northern part and low in the subtropical water. Results showed that algae other than cyanobacteria may significantly contribute to the picophytoplankton community under the low water temperature conditions of open waters. Chlorophylla concentration represented well the abundance of picophytoplankton other than cyanobacteria, but had no significant correlation with the cyanobacteria cell density. Chlorophylla-based data must be interpreted with caution, since the abundances of cyanobacteria were often considerably different even though the chlorophylla concentrations were the same level.     

Hospital Laundry Wastewater Disinfection with Catalytic Photoozonation

Wastewater production in a hospital laundry and the treatment of the most critical wastewater stream, are assessed. Hospital laundry wastewaters are hazardous to the environment due to their high pollutant concentrations and the chemicals added during the clothes washing process. Heterogeneous photocatalysis with UV, O₃ and TiO₂ and their possible combinations were used for disinfection purposes. A ramp‐type reactor was used for TiO₂ (P25 Degussa) fixation and for photochemical diffusion of the ozonized air. After assessing 5‐day biological oxygen demand, chemical oxygen demand, pH, turbidity, and surfactant content, and checking for the presence of thermotolerant coliforms and Escherichia coli, it was concluded that UV/O₃/TiO₂ was the best process/combination, yielding a 100% disinfection rate and a microbiological inactivation of 0.5070 min^–1 for E. coli and of 0.5505 min^–1 for thermotolerant coliforms.     

Human-induced changes on wetlands: a study case from NW Iberia

Wetlands are exceptional ecosystems that contribute to biodiversity and play a key role in the hydrological and carbon cycles. Knowledge of their long-term ecology is essential for a proper understanding of these valuable ecosystems. We present the application of multi-proxy analyses to a 115 cm-thick core from La Molina mire (Alto de la Espina) located in NW Iberia, with a chronology spanning since ～500 BC. The mire is located in an area intensively mined for gold during the Roman period, and close to a water-canalization system used for mining operations at that time. Our aim was to get insights into the development of the wetland by combining palynological records of hydro-hygrophytes, non-pollen palynomorphs and geochemical analyses, supported by ¹⁴C datings and multivariate statistics. The results indicate a complex pattern of ecological succession. During the local Iron Age the wetland was minerotrophic. Since ～20 AD it was subjected to dramatic hydrological changes due to a rise of the water-table, fluctuating between the presence of open water and phases of drawdown. Finally, by ～745 AD, the wetland experienced a rapid evolution towards ombrotrophic conditions. High grazing pressure was detected for the last decades. The significant change occurred during Early Roman Empire seems to have been the consequence of the direct use of the wetland as a water-reservoir of the canalisation system used for gold-mining. Thus, the current nature of the mire may be the result of human impact, although multiple human- and climate-induced causes were potentially linked to the detected shifts. However, the system seems to have been resilient, successfully buffering the changes without substantial alterations of its functioning. Our investigation shows that palaeoecological research is necessary to understand modifications in the structure of wetland ecosystems, their long-term ecology and the role of human-induced changes.