Sediment chronologies based on radioisotope depth profiles were developed at two sites in the San Francisco Bay estuary to provide a framework for interpreting historical trends in organic compound and metal contaminant inputs. At Richardson Bay near the estuary mouth, sediments are highly mixed by biological andror physical processes. Excess Th penetration ranged from 2 to more than 10 cm at e...

Fast solute mixing can be achieved in a microchannel by rapid unidirectional displacement of a discrete liquid drop. The recirculation streamlines created within the liquid during the drop’s motion cause the solute to interlayer across the channel depth, provided the interlayer diffusion of the solute is small. Uniform interlayering appears when the drop is displaced by more than three drop len...

Smith and Rabouille (2002; hereafter SR02) have examined the relationships between the mixed-layer depth in deep-sea sediments, L, as based on 210Pb and 14C profiles, and a set of environmental variables that include particulate organic carbon (POC) flux, oxygen penetration depth, and oceanographic depth. They have established the existence of a strong nonlinear correlation between their operat...

Phytoplankton-grazer dynamics are often characterized by long transients relative to the length of the growing season. Using a phytoplankton-grazer model parameterized for Daphnia pulex with either flexible or fixed algal carbon:nutrient stoichiometry, we explored how nutrient and light supply (the latter by varying depth of the mixed water column) affect the transient dynamics of the system st...

Reliable estimates of in situ phytoplankton growth rates are central to understanding the dynamics of aquatic ecosystems. A common approach for estimating in situ growth rates is to incubate natural phytoplankton assemblages in clear bottles at fixed depths or irradiance levels and measure the change in chlorophyll a (Chl) over the incubation period (typically 24 h). Using a modelling approach,...

This study investigated the main factors influencing digester temperature and methods to reduce heat losses during the cold season in the subtropics. Four composite digesters (two insulated and two uninsulated) were buried underground to measure their internal temperature (°C) at a depth of 140 cm and 180 cm, biogas production and methane (CH4) concentration in biogas from August to February. I...

A cold model of a rotary holding furnace was studied using water and a kerosene-LIX973N organic mixture which are immiscible. The residence time distribution obtained showed that there was an optimum depth of the upper layer of organic where mixing with the bath fluid was maximised. The use of air bubblers showed that at low air flow rates, the air curtain acted to limit mixing but as the air f...

A compact commercial Doppler lidar has been deployed in Indianapolis for two years to measure wind profiles and mixing layer properties as part of project to improve greenhouse measurements from large area sources. The lidar uses vertical velocity variance and aerosol structure to measure mixing layer depth. Comparisons with aircraft and the NOAA HRDL lidar generally indicate good performance, ...