Automated cavity ring down spectroscopy usage for nitrous oxide emission measurements from soil using recirculation system

Abstract

The nitrous oxide accounted for the year 2015 gives 60 % of Latvia's greenhouse gas emissions from the agricultural sector. Majority of nitrous oxide comes from mineral fertiliser application and manure management. Nitrous oxide emission from soils is strongly correlated with the soil moisture and temperature. Since nitrous oxide has very low concentrations in natural environment, there is a risk to overestimate or underestimate nitrous oxide emission. Automated cavity ring down spectroscopy for nitrous oxide emission measurements is a relatively new technology and there is a need for development of proper methodology. The aim of this study is to identify proper measurement time for nitrous oxide emission from soil by using automated cavity ring down spectroscopy with recirculation system. The automated cavity ring down spectroscopy, namely Picarro G2508, was connected in a closed recirculation system with the chamber of total volume 2 litres. Dray soil samples were weighted in containers and different amounts of water and ammonium nitrate were added. Totally 36 samples were used in the experiment. Each sample was measured 10 minutes and the nitrous oxide concentration was recorded for each second. For each sample measurements were repeated three times. The linear regression method was used to calculate the emission amount for different time periods from 30 seconds till 600 seconds. The results of the research show quite high variation of nitrous oxide emission from the soil samples. Data analysis showed that the minimal measurement time has to be at least 250 seconds.