土壤中二氧化碳，甲烷检测方案(同位素质谱仪)

The integration of the automated EOSENSE soilchambers with the isotopic Picarro CRDS analyzersallows to investigate simultaneously the isofluxes ofN，O， co， and CH from soils. Measuring isotopic N，O， co， and CH soil fluxwith cavity ring-down spectroscopy Renato Winkler， Nick Nickerson?， Magdalena E. G. Hofmann1， Muhammad Shahbaz3， Gunnar Borjesson31Picarro， Inc.， Santa Clara， USA *Contact： rwinkler@picarro.com2EOSENSE Inc.， Dartmouth， Canada 3Swedish University of Agricultural Science， Uppsala， Sweden **Contact： nick@eosense.com*** Contact： muhammad.shahbaz@slu.se INTRODUCTION · Stable isotope analysis of N2O， CO， and CH is a valuable tool to better understandproduction and consumption pathways in soils. · Here， we present the integration of two cavity ring-down spectrometers (CRDS) forcontinuous stable isotope analysis of N2O， CO， and CH with 12 automated soil fluxchambers. INSTRUMENTATION Picarro G2201-ianalyzer (near infrared) ·Field-deployable analyzer for simultaneous high-precision 613C analysis of CH and CO2. · Precision (1-0， 1-hour window， 5-minute averages)： 613C-CO2<0.16%o，613C-CH4<1.15%。 Picarro G5131-i analyzer (mid infrared) ·Field station deployable ·Precision (1-a， 1-hour window， 5-minute averages)：615N，615N，615NB，6180<1% Field site The measurements were performed at a long-term field experiment site located at Ultuna，Uppsala， Sweden. The Ultuna trial field has been started in 1956. The soil， a clay loamwith 36.5% clay， has been classified as Eutric Cambisol. At the start of the experiment， thesoil contained 1.5% total C and 0.17% N and was slightly acidic (pH 6.6). The overall aim of the field experiment is to study the effects of different organic andmineral fertilizers on soil properties and carbon (C) and nitrogen (N) dynamics. Thepresent chamber set-up is also designed to investigate the effects of different pH-levels insoil on N2O fluxes， with pH ranging from 4.0 up to 7.5. Considerations for soil chamber measurements · The G5131-ianalyzer (i-N，O) operates in the mid infrared， and therefore， requires morestable operating conditions than a near infrared analyzer. We refer to the G5131-i asbeing field stationary deployable. · The G5131-i analyzer (i-N，O) was initially designed for atmospheric measurements. Apriori， soil chamber measurements are challenging because large variations inbackground gas concentration (e.g. CHa andO2) can require further data postprocessing. · In the setup presented here， the chamber measurements were considered as a quasiclosed loop configuration since the subsampling line for the G5131-i sampled at a lowflow (<50mL/min) and sampling was done for less than 15 minutes. Therefore， thepressure change in the chamber was negligible. Alternatively， one could also allowambient air to mix into the soil chamber to avoid under-pressure. In this case， the smalldilution needs to be taken into account in the data analysis， i.e. following the openchamber approach (personal comm. Eliza Harris， University of Innsbruck). Fig. 1： Schematic illustrating theintegration of the G5131-i andanalyzer with amultiplexer and a eosACautomated chamber system.The G5131-i is subsampling airfrom the G2201-i recirculationloop (also see box on‘Considerations for soil chambermeasurements'). RESULTS Fig. 2： N20 emission during <15 minsoil chamber closure. The NO flux wasdetermined to be 1122.7 nmol/m2/s. Table 1： Keeling plot end-members. Note that all-values are uncalibrated values and the data aremeant to illustrate the precision of the isotopicend-member characterization! Fig. 3： N2O Keeling plotend-members (circles) incomparison too soil andtroposphere literature datafrom Toyoda et al.， 2015.Note that 615Npukand 6180aree tuncalibrated values，still the isotopic values arereasonable. Fig.4： Keeling plots. Notethat the 15Nuk valuesare uncalibrated! CONCLUSIONS ·The Picarro G2201-i and the Picarro G5131-i analyzer can be operated in parallel to obtainN2O， CO2 and CHa isofluxes. Please follow the QR code to learn more about the CO2 andCHa carbon isotope data obtained during this study! · For a ca. 12.5 min soil chamber closure， the N20 concentration was enriched by 130 ppb(corresponding to a flux of 11227 nmol/m2/s) allowing to determine the 615Nbulk： 615N。， 615Ng，6180 end-member with a precision of ±1.4%o，±1.8%o，±1.6%o，±1.6%o， respectively. 1. Picarro G2201-i和Picarro G5131-i分析仪可以并行设置操作以获得N2O，CO2和CH4等通量。2. 大约在土壤室关闭12.5分钟后，N2O浓度增加了130 ppb（对应于11227 nmol / m2 / s的通量），从而可以确定δ15Nbulk，δ15Nα，δ15Nβ，δ18O，精度为±1.4‰，± 分别为1.8‰，±1.6‰，±1.6‰。