Flux chamber

Diagrams of benthic sampiing equipment, (a) Pore water peepers used for collecting pore water in situ via moiecuiar diffusion across a 0.4- j,m polycarbonate membrane. These probes were 36 inches iong. Each of the six ports on the peeper held 6mL of equilibration fluid. The probes were deployed for 1 to 2.5 y to ensure equilibrium had been reached with the pore waters, (b) Benthic flux chamber. This chamber covered a bottom area of SSScm. Source From Aller, R. C., et al. (1998). Deep-Sea Research, 45, 133-165. 

In Illustrative Example 19.2 we discussed the flux of trichloroethene (TCE) from a contaminated aquifer through the unsaturated zone into the atmosphere. The example was based on a real case of a polluted aquifer in New Jersey (Smith et al., 1996). These authors compared the diffusive fluxes, calculated from measured TCE vapor concentration gradients, with total fluxes measured with a vertical flux chamber. They found that the measured fluxes were often several orders of magnitude larger than the fluxes calculated from Fick s first law. In these situations the vapor profiles across the unsaturated zone were not always linear. The authors attributed this to the influence of advective transport through the unsaturated zone. In order to test this hypothesis you are asked to make the following checks ... 

Carpi and Iindberg [160] have developed a Teflon dynamic flux chamber for measuring mercury soil emissions. 

Most studies of the local actions of opioids on the intestinal mucosa have utilized muscle-stripped sheets of ileal mucosa with attached submucosa mounted in Ussing flux chambers. Peptidase-resistant enkephalin derivatives such as DPDPE decrease short-circuit current, an electrical measure of active transepithelial ion transport, across isolated mucosal sheets from the guinea pig ileum [46,127,128], rabbit ileum [129-131], mouse jejunum [132], and pig distal jejunum/ileum [133]. This effect, which occurs after the application of opioid agonists to the serosal aspect of epithelial sheets, is due to an increase in electroneutral salt absorption and a decrease in electrogenic chloride secretion [46,132,133], In contrast to enkephalin derivatives, opiate alkaloids have limited effects on active transepithelial transport of ions [69]. Pretreat-... 

Dr. Stephen Beauchamp in Halifax Harbour. The flux chamber beside him helps him measure the changing concentrations of mercury in the air and water. 

The first example of soil consumption of CH4 was reported by Harriss et al. (1982), who observed seasonal concentration decreases (and increases) in flux chamber headspaces. Keller et al. (1990) reported similar observations for tropical soils. This work was followed by measurements in tundra environments by Whalen and Reeburgh (1990b), and by more extensive experimental work using chamber measurements, jar experiments, and " CH4 tracer experiments on boreal forest soils by Whalen et al. (1992). Koschorreck and Conrad (1993) devised a multiport device for laboratory studies on soil cores. 

The above studies are only able to detect net CH4 production or net CH4 consumption, i.e., either production or consumption must exceed the competing process to produce an observable positive or negative concentration change in a flux chamber. To separate the effects of oxidation and production, the effect of CH4 oxidation has been measured by using CH3F, a specific inhibitor... 

Jahnke R. A. and Jahnke D. B. Calcium carbonate dissolution in deep sea sediments reconciling microelectrode, pore water, and benthic flux chamber results. Geochim. Cosmo-chim. Acta (in press). 

Measurements using flux chambers and micro-meteorological techniques are the most numerous (see special section of J. Geophys. Res. 104(017), 1999). As noted in Section 9.04.2, Kinsman and... 

Carpi A. and Lindberg S. E. (1998) Application of a Teflon dynamic flux chamber for quantifying soil mercury flux test and results over background soil. Atmos. Environ. 32(5), 873-882. 

Figure 1. Box model for the calculation of Mn redox cycling near the sediment-water interface. Sedimentation rates are measured with sediment traps. The burial rate Sh is estimated from dated sediment cores. In situ sampling techniques (flux chambers and peepers) are used to quantify the diffusive flux across the sediment-water interface FS6. The resuspension rate R is estimated from the increase in the mass flux of settling material between the 81- and 86-m horizons.

Measurements of Diffusive Fluxes. Benthic chamber experiments were carried out by using an automatic flux chamber (sediment lander). Our lander followed closely the design of Devol (43). The two benthic flux chambers have an area of 400 cm2 each. They penetrated the sediment to a... 

In this case, flux chamber measurements may provide more accurate estimates of the diffusive fluxes (Figure 6b). Fluxes are calculated in millimoles per square meter per day according to... 

Fig. 1 Steady-state flux chamber measurements and model results of TGM moving from soil to air. (From Ref. l)...

Volatile and semivolatile organic chemicals placed on surface soils have very similar chemical process behavior patterns as those shown above for Hg. Numerous laboratory and a few field flux measurements have been performed on this class of chemicals as documented in a recent review. The review was performed to assess the quantity and quality of measured flux data and the availability of process-based emission models. The basic difference between the flux chamber model and the field-scale model is that the former involves a steady-state flux process and the latter is a transient one. The EC models needed for the large time-scale involved with most field applications must consider the so-called weathering effect which characterizes the depletion of the available-for-volatilization chemical mass in the... 

Lindberg, S.E. Zhang, H. Vette, A.F. Gustin, M.S. Barnett, M.O. Kuiken, T. Dynamic flux chamber measurement of gaseous mercury emissions fluxes over soils. Part 2. Effect of flushing flow rate on verification of a two resistance exchange interface simulation model. Atmos. Environ. 2002, 36, 847-859. 

In order to avoid the difficulties of naturally occurring variations in study conditions, Fall et al. (1988) studied the emission of sulfur gases from several plant/soil systems using a flux chamber. The study was designed so that emissions from soil could be separated from emissions from plants. Variable amounts of carbon disulfide were emitted from wheat. The effects of light and temperature were observed. Further work was proposed so that systematic investigation could accurately measure the contributions of a number of sulfur compounds under varying conditions. 

Ventilated chamber Small plot Surface Ilux Surface flux Chamber does not alter flux Control region is deep enough to neglect flux through top X = 1 m, r =. f 0 min X = 30 m, T = 30 min... 

Rahn, T. A., Fessenden, J. E., and Wahlen, M., Flux chamber measurements of anomalous CO2 emission from the flanks of Mammoth Mountain, California, Geophys. Res. Lett., 23(14), 1861-1864, 1996. 

---