Payatas landfill in Quezon City, Philippines, releases leachate to the Marikina River through a creek.Multivariate statistical techniques were applied to study temporal and spatial variations in water quality of a segment of the Marikina River. The data set included 12 physico-chemical parameters for

No abstract

High temporal-resolution fluctuations in oxygen concentration and vertical velocity were measured over an intertidal sandflat (water depth < 69 cm) using an oxygen microelectrode and an acoustic Doppler velocimeter, in order to estimate oxygen flux across the sediment -water interface using the eddy-correlation method. The effect of flux estimate procedures, including noise removal and extraction of fluctuating components, was investigated. The estimated oxygen effluxes from the sediment ranged from -3.2 to 6.6 mmol O 2 m -2 h -1 in the light and from -14.5 to -6.6 mmol O 2 m -2 h -1 in the dark. The oxygen-uptake fluxes in the dark were markedly higher than those measured by a conventional enclosure technique. High-frequency turbulence and/or noise (> 5 Hz) observed in the vertical velocity and oxygen concentration data made little contribution to the total oxygen flux (0 to 7%). However, trends (steady change over a longer time scale) caused significant artifacts in the estimated fluxes for several cases. Thus, removal of trends from raw time-series data is recommended. The co-spectrum of the fluctuating components of vertical velocity and oxygen concentration revealed that the oxygen flux at a frequency band between 0.3 and 1.4 Hz (at a period from 0.7 to 3.3 s) was a major contributor to the total oxygen flux. This frequency was consistent with the dominant frequency of vertical velocity, indicating that transport and exchange of porewater and overlying water by wind-induced waves may be crucial processes to dissolved oxygen flux between permeable sandy sediments and shallow waters.

No abstract

Inorganic aluminum salts, such as aluminum sulfate, are coagulants that cause small particles, such as bacteria and viruses as well as inorganic particles, to destabilize and combine into larger aggregates. In this investigation, batch coagulation treatments of water samples spiked with Qbeta, MS2, T4, and P1 viruses were conducted with four different aluminum coagulants. The total infectious virus concentration in the suspension of floc particles that eventually formed by dosing with coagulant was measured after the floc particles were dissolved by raising the pH with an alkaline beef extract solution. The virus concentrations were extremely reduced after the water samples were dosed with aluminum coagulants. Viruses mixed with and adsorbed onto preformed aluminum hydroxide floc were, however, completely recovered after the floc dissolution. These results indicated that the aluminum coagulation process inactivates viruses. Virucidal activity was most prominent with the prehydrolyzed aluminum salt coagulant, polyaluminum chloride (PACl). Virucidal activity was lower in river water than in ultrapure water--natural organic matter in the river water depressed the virucidal activity. Mechanisms and kinetics of the virus inactivation were discussed. Our results suggest that intermediate polymers formed during hydrolysis of the aluminum coagulants sorbed strongly to viruses, either rendering them inactive or preventing infectivity.