A laboratory comparison of two methods used to estimate the isotopic composition of soil delta13CO2 efflux at steady state.
نویسندگان
چکیده
The stable isotopic composition of soil (13)CO(2) flux is important for monitoring soil biological and physical processes. While several methods exist to measure the isotopic composition of soil flux, we do not know how effective each method is at achieving this goal. To provide clear evidence of the accuracy of current measurement techniques we created a column filled with quartz sand through which a gas of known isotopic composition (-34.2 per thousand) and concentration (3,000 ppm) diffused for 7 h. We used a static chamber at equilibrium and a soil probe technique to test whether they could identify the isotopic signature of the known gas source. The static chamber is designed to identify the source gas isotopic composition when in equilibrium with the soil gas, and the soil probe method relies on a mixing model of samples withdrawn from three gas wells at different depths to identify the gas source. We sampled from ports installed along the side of the sand column to describe the isotopic and concentration gradient as well as to serve as a control for the soil probe. The soil probe produced similar isotopic and concentration values as the control ports, as well as Keeling intercepts. The static chamber at equilibrium did not identify the source gas but, when applied in a two end-member mixing model, did produce a similar Keeling intercept produced from the control ports. Neither of the methods was able to identify the source gas via the Keeling plot method probably because CO(2) profiles did not reach isotopic steady state. Our results showed that the static chamber at equilibrium should be used only with a Keeling plot approach and that the soil probe is able to provide estimates of uncertainty for the isotopic composition of soil gas as well as information pertinent to the soil profile.
منابع مشابه
Measuring and modelling the isotopic composition of soil respiration: insights from a grassland tracer experiment
The carbon isotopic composition (δ13C) of CO2 efflux (δCefflux) from soil is generally interpreted to represent the actual isotopic composition of the respiratory source (δCRs). However, soils contain a large CO2 pool in airfilled pores. This pool receives CO2 from belowground respiration and exchanges CO2 with the atmosphere (via diffusion and advection) and the soil liquid phase (via dissolut...
متن کاملSampling soil-derived CO2 for analysis of isotopic composition: a comparison of different techniques.
A new system for soil respiration measurement [P. Rochette, L.B. Flanagan, E.G. Gregorich. Separating soil respiration into plant and soil components using analyses of the natural abundance of carbon-13. Soil Sci. Soc. Am. J., 63, 1207-1213 (1999).] was modified in order to collect soil-derived CO2 for stable isotope analysis. The aim of this study was to assess the suitability of this modified...
متن کاملEstimating the Saturated Hydraulic Conductivity of Soil Using Gene Expression Programming Method and Comparing It with the Pedotransfer Functions
Saturated hydraulic conductivity of soil is an important physical property of soil that affects water movement in soil, Since the measurement of saturated hydraulic conductivity by direct methods in the field or in the laboratory is hard, time-consuming and costly, the indirect methods are being used.The aim of this study is to estimate the saturated hydraulic conductivity from other soil prope...
متن کاملImplementation of a Low- Cost Multi- IMU by Using Information Form of a Steady State Kalman Filter
In this paper, a homogenous multi-sensor fusion method is used to estimate the trueangular rate and acceleration with a combination of four low cost (< 10$) MEMS Inertial MeasurementUnits (IMU). An information form of steady state Kalman filter is designed to fuse the output of four lowaccuracy sensors to reduce the noise effect by the square root of the number of sensors. A hardware isimplemen...
متن کاملA field-based method for simultaneous measurements of the δ18O and δ13C of soil CO2 efflux
Three approaches for determining the stable isotopic composition (δ13C and δ18O) of soil CO2 efflux were compared. A new technique employed mini-towers, constructed of open-topped piping, that were placed on the soil surface to collect soil-emitted CO2. Samples were collected along a vertical gradient and analyzed for CO2 concentration and isotopic composition. These data were then used to prod...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Rapid communications in mass spectrometry : RCM
دوره 22 16 شماره
صفحات -
تاریخ انتشار 2008