Automated sampling system for long-term monitoring of nitrous oxide and methane fluxes from soils

Abstract

We describe an automated gas sampling system for monitoring trace gas fluxes from soils. The sampling system allows automated collection of gas samples in glass vials using a syringe pump connected to an automated static chamber installed in the field. The gas samples are transferred to a laboratory and then analyzed using a gas chromatography system. Comparisons between manual and automated sampling of standard gases showed good agreement (r 2 = 0.99996 for N 2 O, r 2 = 0.999 for CH 4 and r 2 = 0.998 for CO 2 ). In a field test, replicated flux measurements using two chambers generally showed good agreement. The sampling system allows frequent and long-term monitoring of fluxes under a wide range of weather conditions (tested temperatures ranged from -6.5 to 40°C; 127 mm day -1 max precipitation). The major advantages of the system are its increased portability, ease of operation and cost effectiveness compared with on-line automated sampling/analytical systems.

Fully automated, high‐throughput instrumentation for measuring the δ13C value of methane and application of the instrumentation to rice paddy samples

“…The combination of automated gas sampling with high‐throughput δ 13 C analyses revealed a distinct temporal variation in the δ 13 C values of the CH 4 emitted from the rice paddy with the highest time resolution ever reported. A clear seasonal trend in δ 13 C values was observed: CH 4 was relatively enriched in 13 C at the beginning of the growing season; as the season progressed, CH 4 became lighter in 13 C, reaching a minimum at the middle of the season; and then it became enriched in 13 C again over the reproductive stages of the rice (Fig.…”

“…Note that with our system, we were able to measure the δ 13 C values of atmospheric CH 4 in 19‐mL vials (~1.6 nmol). The same type of vial has been used in an automated gas‐sampling system for measuring gas fluxes . Therefore, our system enabled us to obtain the δ 13 C signature of CH 4 along with CH 4 flux data without the need for additional sampling (see the next section).…”

Methane and nitrous oxide emissions due to excreta returns from grazing cattle in Nasu, Japan

“…; Akiyama et al . ). The bottom edge of each clear polycarbonate cubic chamber (45 × 45 × 45 cm) was inserted into the soil to a depth of 5 cm by cutting a narrow slit into the turf in the shape of a 45 × 45 cm square.…”

“…In each trial, we monitored the fluxes of CH 4 and N 2 O for 78-85 days by using automated closed chambers (Allen et al 1996;Akiyama et al 2009). The bottom edge of each clear polycarbonate cubic chamber (45 9 45 9 45 cm) was inserted into the soil to a depth of 5 cm by cutting a narrow slit into the turf in the shape of a 45 9 45 cm square.…”

Nitrogen Cycling in Rice Paddy Environments: Past Achievements and Future Challenges

“…Although the nitrification-denitrification process may cause loss of fertilizer N from rice paddy fields, it can prevent environmental pollution, such as nitrate leaching and emission of a greenhouse gas, nitrous oxide (N 2 O). In situ gas monitoring studies revealed only little emission of N2O from rice paddy soils throughout the rice cultivation period, in contrast to upland crop fields (4,86). Since rice paddy soils have strong denitrification activity (3), little emission of N2O gas indicates that N2 is the major end product of denitrification in rice paddy fields (86).…”