HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Reichman, R. Articles by Rolston, D. E. Search for Related Content PubMed PubMed Citation Articles by Reichman, R. Articles by Rolston, D. E. Agricola Articles by Reichman, R. Articles by Rolston, D. E. Related Collections Organic Compounds Other Environmental Contamination Air Pollution Soil Pollution

TECHNICAL REPORTS
Atmospheric Pollutants and Trace Gases

Design and Performance of a Dynamic Gas Flux Chamber

^a Environmental Physics Dep., Israel Institute for Biological Research, P.O. Box 19, Ness-Ziona 74100, Israel
^b Land, Air and Water Resources, University of California, One Shields Ave., Davis, CA 95616

* Corresponding author (raichman{at}iibr.gov.il)

Received for publication September 24, 2001.

	ABSTRACT

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Chambers are commonly used to measure the emission of many trace gases and chemicals from soil. An aerodynamic (flow through) chamber was designed and fabricated to accurately measure the surface flux of trace gases. Flow through the chamber was controlled with a small vacuum at the outlet. Due to the design using fans, a partition plate, and aerodynamic ends, air is forced to sweep parallel and uniform over the entire soil surface. A fraction of the air flowing inside the chamber is sampled in the outlet. The air velocity inside the chamber is controlled by fan speed and outlet suction flow rate. The chamber design resulted in a uniform distribution of air velocity at the soil surface. Steady state flux was attained within 5 min when the outlet air suction rate was 20 L/min or higher. For expected flux rates, the presence of the chamber did not affect the measured fluxes at outlet suction rates of around 20 L/min, except that the chamber caused some cooling of the surface in field experiments. Sensitive measurements of the pressure deficit across the soil layer in conjunction with measured fluxes in the source box and chamber outlet show that the outflow rate must be controlled carefully to minimize errors in the flux measurements. Both over- and underestimation of the fluxes are possible if the outlet flow rate is not controlled carefully. For this design, the chamber accurately measured steady flux at outlet air suction rates of approximately 20 L/min when the pressure deficit within the chamber with respect to the ambient atmosphere ranged between 0.46 and 0.79 Pa.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
VOLATILIZATION OF soil-applied organic chemicals (e.g., pesticides) from soil to the atmosphere and their vapor transport in air are the principal processes leading to their widespread dispersion in the environment (Glotfelty et al., 1984; Taylor and Spencer, 1990). There are growing concerns over the potential risks from exposure to airborne pesticides and other hazardous materials that have immediate and/or long-term human and ecological health impacts. Accurate measurement of soil trace gases emission to the atmosphere is essential for estimating amounts of hazardous materials emitted into the atmosphere, and thus for assessing the effects of such emissions upon the environment.

A variety of techniques has been developed and used to measure emission in the field (de Mello and Hines, 1994; Denmand and Raupach, 1993; Lenschow, 1995; Hutchinson and Livingston, 1993, 2002; Livingston and Hutchinson, 1995; Majewski et al., 1990, 1995; Rolston, 1986, 1994; Weseley et al., 1989; Yates et al., 1997). Various micrometeorological methods (e.g., aerodynamic method) (Lenschow, 1995; Majewski et al., 1990, 1995; Yates et al., 1997) and enclosure-based methods (e.g., flux chambers) (de Mello and Hines, 1994; Denmand and Raupach, 1993; Hutchinson and Livingston, 1993, 2002; Livingston and Hutchinson, 1995; Rolston, 1986, 1994; Weseley et al., 1989) are the most common. The micrometeorological-based measurements that are frequently used for measuring pesticide volatilization rates require extensive instrumentation and highly sensitive pesticide concentration measurements at different heights in the air (e.g., the gradient method). The treated area also needs to be large to achieve a reasonable fetch. Measuring emission with chamber methods is relatively simple and does not require a large surface area. These methods involve placing an open-bottom chamber over a small area of soil surface and measuring the gas emitted into the chamber. The trapping arrangement may be by passive (or closed) systems or active (or dynamic, flowing) systems. Various assumptions are applied to these chamber methods, and models based on these assumptions have been developed and used to calculate fluxes from the data obtained (de Mello and Hines, 1994; Denmand and Raupach, 1993; Gao and Yates, 1998b; Rolston, 1986, 1994, Livingston and Hutchinson, 1995; Hutchinson and Livingston, 2002). Although some of the assumptions associated with these methods may not be entirely valid under real-world situations, chambers have been used extensively for measuring emissions of a variety of gases due to their simplicity and ease in fabrication and operation. The variety of gases measured includes trace gases, such as CO₂, N₂O, NO_x, CH₄, and selenium (Se) (de Mello and Hines, 1994; Fukui and Doskey, 1996; Hutchinson and Mosier, 1981; Jury et al., 1982; Kanemasu et al., 1974; Valente et al., 1995; Lin et al., 1999; Dungan et al., 2000) and volatile organic compounds (VOCs), such as volatile pesticides (Gao et al., 1997; Gao and Yates, 1998a; Sanders et al., 1985; Yates et al., 1997; Yagi et al., 1993; Wang et al., 1997; Woodrow and Seiber, 1991), spilled volatile solvents, and volatile constituents from waste disposal sites (Balfour et al., 1987; Eklund, 1992). Experience gained from numerous applications of both types of flux chambers has shown that both methods have their own advantages and disadvantages. Summaries and comments on the advantages and disadvantages of these chamber methods can be found in the reviews of Hutchinson and Livingston (1993)( 2002), Livingston and Hutchinson (1995), Rolston (1986), Weseley et al. (1989), and Denmead and Raupach (1993).

Although the flux chamber method is probably one of the simplest tools for measuring volatile organic compound volatilization, it can have several disadvantages compared with micrometeorological-based measurements (Yates et al., 1997; Wang et al., 1997). First, when the chamber sampling area is a small fraction of total area for emission, the measured flux could be highly variable due to soil spatial heterogeneity. Next, the presence of the chamber can change the environmental properties (such as soil temperature and the wind profile near the soil surface) of the sampled area compared with the rest of the surface area. This effect on local environment is especially large for the static chambers but may be small for the dynamic chambers if designed and operated properly (Jury et al., 1982; Hutchinson et al., 2000; Wang et al., 1997). Yates et al. (1997) used four independent methods including flux chamber and micrometeorological (aerodynamic, theoretical profile shape [TPS], and integrated horizontal flux [IHF]) methods to estimate the total methyl bromide lost after application. They found a reasonable agreement between fluxes measured using the dynamic chamber and the aerodynamic method, which was better than the agreement between the aerodynamic and the other (theoretical profile shape and integrated horizontal flux) micrometeorological methods where lower rates were obtained.

One major disadvantage associated with dynamic chambers is that the air flowing through the chamber may change the pressure gradient between the soil-gas phase and the chamber interior (Gao et al., 1997; Gao and Yates, 1998a,b; Livingston and Hutchinson, 1995; Hutchinson and Livingston, 1993, 2002; Rolston, 1986). This pressure difference may create advective mass flow of the target gas that will result in an under- or overestimate of emissions, depending on design. In the case of pumping air into the chamber, an underestimation of the flux is most likely, while overestimation can be observed where the air is sucked out (Kanemasu et al., 1974). Another potential problem with the dynamic chamber is associated with the aerodynamic behavior or airflow pattern if not designed properly (Gao et al., 1997). Gao and Yates (1998b) analyzed flux chambers using diffusion theory and mass balance principles. Simulations using a mathematical model for the dynamic chamber showed that the proper measurement of flux depends on both chamber operation conditions and soil air permeability. A dynamic chamber may underestimate the actual flux when operating on low permeability soils. On soils with high air permeability, a dynamic chamber may give an underestimate of the actual flux when operating at low airflow rate but an overestimate when the airflow rate is high. The latter predictions were confirmed in a laboratory study where emission of methylene chloride from a constant source was measured (Gao and Yates, 1998a).

In this paper, we describe a dynamic flux chamber that was designed and fabricated to minimize the bias of underestimation or overestimation of the actual flux. Results from laboratory and field tests are presented and discussed.

	THEORY

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
In general, a flow-through chamber can be analyzed with the principle of mass balance, that is, the mass change of the target gas within the chamber headspace (dM) is due to the mass input and output, which can be expressed as (Gao and Yates, 1998b):

[1]

where V is the volume of the chamber headspace, dC^a is the change of the target gas concentration within the chamber headspace, A is the enclosed soil surface area, J_g is the flux of the target gas at the enclosed soil surface, Q is the airflow rate, and C_in(t) and C_out(t) are the target gas concentrations in the chamber for the incoming air and outgoing air, respectively.

A hidden assumption in Eq. [1] is that the airstream through the chamber sweeps over the entire covered soil surface with a uniform velocity, and its direction is parallel to the enclosed soil surface. If the chamber is operating under steady state, that is, the rate of airflow through the chamber is constant and not a function of time, we have:

[2]

which is a commonly used equation to calculate steady state fluxes for dynamic chambers (de Mello and Hines, 1994; Livingston and Hutchinson, 1995; Hutchinson and Livingston, 1993, 2002; Gao and Yates, 1998a,b; Rolston, 1986; Wang et al., 1997). However, this equation can be used only if the dynamic chamber design follows the above assumptions.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Aerodynamic Chamber Design and Fabrication
The aerodynamic flux chamber was designed and fabricated to meet the following criteria.

1. The airflow in the chamber should sweep over the entire enclosed soil surface, eliminating any stagnant air zones in the chamber.

2. The direction of the airflow in the chamber should be parallel to the covered soil surface, and any components of airflow perpendicular to the soil surface should be eliminated.

3. The openings of the chamber's air inlet and outlet should be large enough to minimize pressure changes due to air introduction and to ensure a relatively uniform velocity of airstream in the chamber at the desired air flow rates.

4. Air velocity inside the chamber should be as close as possible to the ambient conditions, approximately 1 and 4.5 m/s for 2 cm and 2 m above the soil surface, respectively. These values were obtained with the logarithmic profile equation (Eq. [3]) that is commonly used to describe the vertical wind velocity distribution in the Ekman layer (turbulent boundary layer) (McIlveen, 1986) with u_* = 0.3 m/s (a centered value of a wide range of measurements; McIlveen, 1986) and z₀ = 0.5 cm (laminar boundary layer depth):

[3]

where v is the vertical wind velocity, u_* is the friction velocity, k = 0.4 is von Karman constant, z is the vertical coordinate, and z₀ is the aerodynamic roughness length.

5. The pattern of airflow in the chamber should be relatively uniform across the soil surface to simplify the analysis of such flow.

6. The outside surface of the chamber should reflect solar radiation so that radiant heating can be effectively reduced.

7. Material for chamber fabrication should be strong and rigid to avoid structural deformation under field conditions.

The flux chamber, schematically shown in Fig. 1 , consists of a large air inlet (2.5 cm), main body (40 x 40 cm) divided into two sections by a partition plate, five fans, aerodynamic edges, and air outlet. The entire chamber body was made with 20-gauge galvanized sheet metal. Due to the design using fans, a partition plate, and aerodynamic ends, air is forced to sweep parallel and uniform over the entire soil surface. A fraction of the air flowing inside the chamber is sampled in the outlet. The air velocity inside the chamber is controlled by fan speed and outlet suction flow rate (Q).

View larger version (24K): [in this window] [in a new window]   Fig. 1. Schematic diagram of the flux chamber: (a) side view and (b) top view.

Aerodynamic Behavior
To study the aerodynamic behavior of the chamber and to evaluate whether it meets the design criteria, the air velocity distribution within the chamber was measured with a hotwire anemometer Model W-141-A (Weather Measure Corporation, Sacramento, CA). The air velocity inside the chamber was measured at 16 evenly distributed points, shown schematically in Fig. 1b, at the height of 1.3 to 2.3 cm above the soil surface. The velocity distribution was measured for different fan positions and outlet suction flow rates while the chamber was set up as shown in Fig. 2 .

View larger version (18K): [in this window] [in a new window]   Fig. 2. Experimental setup.

These tests were performed with the experimental system shown in Fig. 2 that consisted of a constant source box, a layer of soil supported by a screen above the source, chamber, and air flow system. During the experiments, the apparatus was placed in a laboratory fume hood at 25°C ambient temperature.

Constant Source Box. The constant source was an open top box (75 x 75 x 21.5 cm) packed with 7.5 cm of fine sandy soil creating a 14-cm chamber for the vapor source. The chamber base (40 x 40 x 5 cm) covers only a part of the soil surface area leaving some soil area open to the atmosphere. Liquid Freon 113 was introduced through a burette connected to the input port into a Petri dish. A fan achieved mixing inside the chamber. The Freon was allowed to evaporate for 4 to 6 h to establish steady state flux conditions prior to chamber tests. Sampling and analyzing gaseous Freon at several points within the source box confirmed Freon uniformity and well-mixed conditions inside the box.

Soil Properties. The soil used in this study was Oso-flocco sand classified as fine sand. The bulk density was 1.57 g/cm³, and the air permeability was 2 x 10^-11 m².

Chemical Properties. Freon-113 (1,1,2-trichloro-1,2,2-trifluororthane), a volatile organic liquid, was the constant vapor source chemical in this study. Due to its boiling point (47.6°C), Freon 113 evaporates from its liquid phase under ambient temperature and can provide a vapor source of constant concentration. It also has low toxicity and low adsorption (Altevogt, 2001) to sand compared with other volatile organic solvents with the same volatility. The Freon-113 (Fisher Scientific Co., Fair Lawn, NJ) used in these experiments was of Optima grade purity. Other chemical–physical properties are summarized in Table 1.

Pressure Deficit
The pressure deficit between the soil surface inside the chamber and the outside open air and across the soil layer (P2–P1; Fig. 2) was measured with an Omega Engineering (Stamford, CT) Model PX2670 differential pressure transducer (range: ±25 Pa; sensitivity: 0.01 Pa). The pressure deficit was measured for different air velocities and outlet suction flow rates.

The pressure deficit influence on the measured soil emissions was studied by simultaneous measurement of fluxes in the source box, chamber outlet, and pressure deficits across the soil layer for three air velocities and three outflow suction rates. Emission rate from the source box was determined from the changing mass of the Freon source measured with a balance (Ohaus [Florham Park, NJ] Scout II Model SR2020) inserted into the source box.

Field Tests
Chamber effects on soil temperature were studied at a University of California-Davis experimental field during July 2000. The soil at the site is Yolo silt loam (22% sand, 56% silt, 22% clay and 1.9% organic matter) and is classified as fine-silty, mixed, superactive, nonacid, thermic Mollic Xerofluvent. Bulk density of the upper 2 cm was 1.2 g/cm³.

Soil temperature was measured at two depths (1 and 5 cm) with a Campbell Scientific (Logan, UT) 101 thermistor probe. The dependence of soil temperature deviation on the duration that the chamber was in place, time of day, and soil moisture was evaluated. The chamber effect on soil temperature was determined from the deviation of the measurement from that expected from the normal diurnal temperature curve.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Aerodynamic Behavior
The results for air velocity distribution within the chamber as a function of three average flow velocities are summarized in Table 2 and shown in Fig. 3 . The average air velocity at 1.3 to 2.3 cm above the soil surface varied in the range of 1.06 to 1.26 m/s, a velocity consistent with the design criteria. The low coefficient of variation (6–8%) suggests a fairly uniform distribution of air velocity within the chamber. The outlet suction rate showed no effect on air velocity distribution.

View larger version (41K): [in this window] [in a new window]   Fig. 3. Distribution of air velocity in the chamber.

View this table: [in this window] [in a new window]   Table 3. Pressure deficits measured between the open atmosphere (POA) and the soil surface inside the chamber (POA-P1), and across the soil layer (PP2-P1) as function of outlet suction rates for three different average velocities inside the chamber.

View larger version (23K): [in this window] [in a new window]   Fig. 4. Fluxes measured in the chamber outlet vs. fluxes measured in source box and pressure deficits across the soil layer for v = 1.26 m/s and (a) Q = 30 L/min, (b) Q = 20 L/min, and (c) Q = 10 L/min.

View larger version (23K): [in this window] [in a new window]   Fig. 6. Fluxes measured in the chamber outlet vs. fluxes measured in source box and pressure deficit across the soil layer for v = 1.06 m/s and (a) Q = 30 L/min, (b) Q = 20 L/min, and (c) Q = 10 L/min.

View larger version (22K): [in this window] [in a new window]   Fig. 5. Fluxes measured in the chamber outlet vs. fluxes measured in source box and pressure deficit across the soil layer for v = 1.15 m/s and (a) Q = 30 L/min, (b) Q = 20 L/min, and (c) Q = 10 L/min.

Soil Temperature
Chamber effects on soil temperature at two soil depths for two soil surface moisture conditions (Fig. 7) show that the chamber depressed soil temperature. The extent of soil cooling depended on soil depth, soil moisture conditions, time of day, and time period that the chamber was in place. Chamber effects on soil temperature at 5 cm were negligible compared with 1 cm, especially under wet soil conditions. The decrease in temperature under dry soil conditions was three times higher (maximum 6–9°C) compared with wet soil conditions (maximum 2–3°C) for the same time of day. The maximum cooling was observed during the period between 1400 and 1600 h. Generally, the longer the chamber was in place, the greater the soil cooling. However, significant cooling was observed only during the afternoon hours (1400–1600 h), which is a small portion of the diurnal period of time (8%). On a daily basis, the average soil temperature perturbation was about 1.5°C, which is expected to cause only small errors in flux measurements. The main effect of this perturbation could be observed only on the diurnal pattern of flux measurement. We expect that during the midday and early afternoon hours, the observed volatilization rates will be lower due to the lowered soil temperature. As a result, higher pesticide concentrations will remain in the soil surface layer, enhancing the volatilization rates during the late afternoon hours. More field experiments and/or modeling will need to be done to fully understand this effect and test its magnitude.

View larger version (35K): [in this window] [in a new window]   Fig. 7. Chamber effect on soil temperature at two depths for two soil surface water contents.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

	ACKNOWLEDGMENTS

 
This research was supported by the NIEHS Superfund Basic Research Program (P42ESO4699) and the USEPA Center for Ecological Health Research (R819658, R825433) at the University of California-Davis. Although the information in this document has been funded in part by the USEPA, it may not necessarily reflect the views of the Agency and no official endorsement should be inferred. We thank Dianne Louie, Matt Quok, and Jakov and Edan Reichman for their assistance with some of the experiments.

	REFERENCES

TOP ABSTRACT INTRODUCTION THEORY MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

• Altevogt, A.S. 2001. A determination of the flux of gas-phase volatile organic compounds due to naturally occurring, environmentally significant driving forces. Ph.D. diss. Univ. of California, Davis.
• Balfour, W.D., C.E. Schmidt, and B.N. Eklund. 1987. Sampling approaches for the measurement of volatile compounds in hazardous waste sites. J. Hazard. Mater. 14:135–148.
• De Mello, W.Z., and M.E. Hines. 1994. Application of static and dynamic enclosures for determining dimethyl sulfide and carbonyl sulfide exchange in Sphagnum peatland: Implication for magnitude and direction of flux. J. Geophys. Res. 99:14601–14607.
• Denmand, O.T., and M.R. Raupach. 1993. Methods for measuring atmospheric gas transport in agricultural and forest systems. p. 19–23. In L.A. Harper, A.R. Moiser, J.M. Duxbury, and D.E. Rolston (ed.) Agricultural ecosystem effects on trace gases and global climate change. ASA Spec. Publ. 55. ASA, Madison, WI.
• Dungan, R.S., A. Stork, and W.T. Frankenberger, Jr. 2000. A wind tunnel for measuring selenium volatilization under field-like conditions. J. Environ. Qual. 29:460–466.[Abstract/Free Full Text]
• Eklund, B. 1992. Practical guidance for flux chamber measurements of fugitive volatile organic emission rates. J. Air Waste Manage. Assoc. 42:1583–1591.
• Fukui, Y., and P.V. Doskey. 1996. An enclosure technique for measuring non-methane organic compound emissions from grassland. J. Environ. Qual. 25:601–610.[Abstract/Free Full Text]
• Gao, F., and S.R. Yates. 1998a. Laboratory study of closed and dynamic flux chambers: Experimental results and implications for field application. J. Geophys. Res. 103 (D20):26115–26125.
• Gao, F., and S.R. Yates. 1998b. Simulation of enclosure-based methods for measuring gas emissions from soil to the atmosphere. J. Geophys. Res. 103 (D20):26127–26136.
• Gao, F., S.R. Yates, M.V. Yates, J. Gan, and F.F. Ernst. 1997. Design, fabrication and application of a dynamic chamber for measuring gas emissions from soil. Environ. Sci. Technol. 31:148–153.
• Glotfelty, D.E., A.W. Taylor, B.C. Turner, and W.H. Zoller. 1984. Volatilization of surface-applied pesticides from fallow soil. J. Agric. Food Chem. 32:638–643.
• Hutchinson, G.L., and G.P. Livingston. 1993. Use of chamber systems to measure trace gas fluxes. p. 63–78. In L.A. Harper, A.R. Moiser, J.M. Duxbury, and D.E. Rolston (ed.) Agricultural ecosystem effects on trace gases and global climate change. ASA Spec. Publ. 55. ASA, Madison, WI.
• Hutchinson, G.L., and G.P. Livingston. 2002. Gas flux. In J. Dane and C. Topp (ed.) Methods of soil analysis. Part 4. SSSA Book Ser. 5. SSSA, Madison, WI (in press).
• Hutchinson, G.L., G.P. Livingston, R.W. Healy, and R.G. Striegl. 2000. Chamber measurement of surface–atmosphere trace gas exchange: Numerical evaluation of dependence on soil, interfacial layer, and source/sink properties. J. Geophys. Res. 105 (D7):8865–8875.
• Hutchinson, G.L., and A.R. Mosier. 1981. Improved soil cover method for field measurement of nitrous oxide fluxes. Soil. Sci. Soc. Am. J. 45:311–316.[Abstract/Free Full Text]
• Jury, W.A., J. Letey, and T. Collins. 1982. Analysis of chamber methods used for measuring nitrous oxide fluxes. Soil. Sci. Soc. Am. J. 46:250–256.[Abstract/Free Full Text]
• Kanemasu, E.T., W.L. Powers, and J.W. Sij. 1974. Field chamber measurements of CO₂ flux from soil surface. Soil Sci. 118:233–237.
• Lenschow, D.H. 1995. Micrometeorological techniques for measuring biosphere–atmosphere trace gas exchange. p. 126–163. In P.A. Matson and R.C. Harris (ed.) Biogenic trace gases: Measuring emissions from soil and water. Blackwell Sci., Malden, MA.
• Lin, Z.-Q., D. Hansen, A. Zayed, and N. Terry. 1999. Biological selenium volatilization: Method of measurement under field conditions. J. Environ. Qual. 28:309–315.[Abstract/Free Full Text]
• Livingston, G.P., and G.L. Hutchinson. 1995. Enclosure-based measurement of trace gas exchange: Applications and sources of error. p. 14–51. In P.A. Matson and R.C. Harris (ed.) Biogenic trace gases: Measuring emissions from soil and water. Blackwell Sci., Malden, MA.
• Longdoz, B., M. Yernaux, and M. Aubinet. 2000. Soil CO₂ efflux measurements in a mixed forest: Impact of chamber disturbances, spatial variability and seasonal evolution. Global Change Biol. 6:907–917.
• Lund, C.P., W.J. Riley, L.L. Pierce, and C.B. Field. 1999. The effects of chamber pressurization on soil-surface CO₂ flux and the implications for NEE measurements under elevated CO₂. Global Change Biol. 5:269–281.
• Majewski, M.S., D.E. Glotfelty, K.T. Paw, and J.N. Seiber. 1990. A field comparison of several methods for measuring pesticide evaporation rates from soil. Environ. Sci. Technol. 24:1490–1497.
• Majewski, M.S., M.M. Mcchesney, J.E. Woodrow, J.H. Prueger, and J.N. Seiber. 1995. Aerodynamic measurements of methyl bromide volatilization from tarped and nontarped fields. J. Environ. Qual. 24:742–752.[Abstract/Free Full Text]
• McIlveen, J.F.R. 1986. Basic meteorology: A physical outline. Van Nostrand Reinhold (UK) Co. Ltd., Berkshire, England.
• Rolston, D.E. 1986. Gas flux. p. 1103–1119. In A. Klute (ed.) Methods of soil analysis. Part 1. 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
• Rolston, D.E. 1994. Measuring and modeling gaseous losses of nitrogen. p. 13–25. In 25th Congr. of the Int. Assoc. of Hydrogeol., Adelaide, Australia. Int. Assoc. of Hydrogeol., Adelaide.
• Sanders, P.F., M.M. Mcchesney, and J.N. Seiber. 1985. Measuring pesticide volatilization from small surface areas in the field. Bull. Environ. Contam. Toxicol. 35:569–575.[ISI][Medline]
• Taylor, A.W., and W.F. Spencer. 1990. Volatilization and vapor transport processes. p. 213–269. In H.H. Cheng (ed.) Pesticides in the soil environment: Processes, impacts, and modeling. SSSA Book Ser. 2. SSSA, Madison WI.
• Valente, R.J., F.C. Thornton, and E.J. Williams. 1995. Field comparison of static and flow through chamber techniques for measurement of soil NO emission. J. Geophys. Res. 100:21138–21147.
• Wang, D., S.R. Yates, and F.F. Ernst. 1997. Calibration and testing of a dynamic flow-through chamber for field determination of methyl bromide volatilization flux. Atmos. Environ. 32:4119–4123.
• Weseley, M.L., D.H. Lenschow, and O.T. Denmead. 1989. Flux measurement techniques. p. 31–46. In D.H. Lenscow and B.B. Hicks (ed.). Global tropospheric chemistry: Chemical fluxes in the global atmosphere. Natl. Center for Atmos. Res., Boulder, CO.
• Woodrow, J.E., and J.N. Seiber. 1991. Two chamber methods for the determination of pesticide flux from contaminated soil and water. Chemosphere 23:291–304.
• Yagi, K., J. Williams, N.Y. Wang, and R.J. Cicerone 1993. Agricultural soil fumigation as a source of atmospheric methyl bromide. Proc. Natl. Acad. Sci. 90:8420–8423.[Abstract/Free Full Text]
• Yates, S.R., D. Wang, F.F. Ernst, and J. Gan. 1997. Methyl bromide emissions from agricultural fields: Bare-soil, deep injection. Environ. Sci. Technol. 31:1136–1143.

This article has been cited by other articles:

				I. J. van Wesenbeeck, J. A. Knuteson, D. E. Barnekow, and A. M. Phillips Measuring Flux of Soil Fumigants Using the Aerodynamic and Dynamic Flux Chamber Methods J. Environ. Qual., April 5, 2007; 36(3): 613 - 620. [Abstract] [Full Text] [PDF]

				G. P. Livingston, G. L. Hutchinson, and K. Spartalian Trace Gas Emission in Chambers: A Non-Steady-State Diffusion Model Soil Sci. Soc. Am. J., August 3, 2006; 70(5): 1459 - 1469. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Reichman, R. Articles by Rolston, D. E. Search for Related Content PubMed PubMed Citation Articles by Reichman, R. Articles by Rolston, D. E. Agricola Articles by Reichman, R. Articles by Rolston, D. E. Related Collections Organic Compounds Other Environmental Contamination Air Pollution Soil Pollution