Vent and soil flux measurement system

Abstract

A method and apparatus are provided for maintaining pressure inside a closed chamber equal to the changing outside pressure, detecting leaks in the plumbing (i.e., air handling system) of a trace gas flux measurement system, and estimating the kinetic volume, e.g., of such a system.

What is claimed is: 
     
         1 . A system comprising:
 a chamber; and   a vent coupled with the chamber;   wherein the vent comprises first and second vent surfaces, and wherein a distance between the first and second vent surfaces decreases from a center of the vent to an edge of the vent.   
     
     
         2 . The system of  claim 1 , wherein the vent is positioned far enough away from a surface of the chamber to allow air to enter the vent at a free stream velocity. 
     
     
         3 . The system of  claim 1 , wherein the vent comprises a cylindrical symmetrical shape. 
     
     
         4 . The system of  claim 1 , wherein the vent comprises a center region and an inlet/outlet region, and wherein a height of the center region is about five times greater than a height of the inlet/outlet region. 
     
     
         5 . The system of  claim 1 , wherein the vent comprises a center region and an inlet/outlet region, and wherein at least one vent surface tapers from the center region to the inlet/outlet region at an angle of about 15 degrees or less. 
     
     
         6 . The system of  claim 5 , wherein the vent comprises a center region and an inlet/outlet region, and wherein both vent surfaces taper from the center region to the inlet/outlet region at an angle of about 15 degrees or less. 
     
     
         7 . The system of  claim 1  further comprising a gas analyzer coupled with the chamber. 
     
     
         8 . The system of  claim 7 , wherein the gas analyzer is operative to measure CO 2 . 
     
     
         9 . The system of  claim 1 , wherein the chamber comprises a soil flux chamber. 
     
     
         10 . A soil flux measurement system comprising:
 a chamber;   a gas analyzer; and   a leak detection system, wherein the chamber, the gas analyzer, and the leak detection system are coupled together with conduits, the leak detection system comprising:
 a pump; 
 a valve; and 
 a pressure transducer. 
   
     
     
         11 . The soil flux measurement system of  claim 10  further comprising:
 at least one additional chamber; and 
 a multiplexer coupled with the first-mentioned chamber and the at least one additional chamber with conduits. 
 
     
     
         12 . A method for determining an active volume of a chamber over a non-uniform surface that has air-filled pores where the active volume is unknown, the method comprising:
 (a) measuring a steady state flux; and   (b) using the measured steady state flux to determine an active volume in a transient flux measurement.   
     
     
         13 . The method of  claim 12 , wherein the steady state and transient flux measurements are for a concentration of CO 2 . 
     
     
         14 . The method of  claim 12 , wherein the steady state and transient flux measurements are for a concentration of methane.