Epsilon Archive for Student Projects

Abstract

The research group Soil and Water Management at the department of Soil and Environment at the
Swedish University of Agricultural Sciences in Uppsala are studying greenhouse gas emissions from
cultivated peat soils. To measure carbon dioxide emissions from peat soils in the field the research
group are now using two portable carbon dioxide meters (Vaisala GMP343). For practical reasons,
they plan to acquire a new type of automated field meter. The aim of this study is to evaluate the
present meters to see how environmental conditions and instrument settings affect the results,
which is meant to facilitate the introduction of the new field meter when the meters needs to be
compared. As a part of the study the relationship between groundwater level and carbon dioxide
emissions from peat soils will be investigated.

The evaluation of the two carbon dioxide meters was made by connecting them to one single airtight
system, with the aim of creating identical measurement environments. Various factors such as
warm-up time and flow rate was tested to see how they affect the results, and to see if there are any
disparities between the meters. The relationship between groundwater level and carbon dioxide
emission was investigated by adjusting the groundwater level in three different peat soil profiles
from Örke in Sweden (60 ° N, 17 ° E) in a temperature regulated laboratory. The carbon dioxide
emissions from the profiles were measured using a Vaisala GMP343 carbon dioxide meter at
groundwater levels 0, -5, -20, -30 and -40 cm.

The results from the evaluation of the carbon dioxide emission meters show that there are some
differences between the meters that needs to be taken into account when measurements are made.
The most important discovery is that the two meters registers different carbon dioxide
concentrations, and that the difference between them is not constant at different concentrations.
The observed difference can introduce systematic errors when both meters are used in the same
experiment, errors that may result in erroneous conclusions when the research group investigate
how different treatments of peat soils affects carbon dioxide emissions. The results from
investigating the relationship between groundwater level and carbon dioxide emission show that
there is an obvious positive correlation between the two. Carbon dioxide emissions was largest at
the groundwater level of -40 cm and then declined to an average of 43% and 12% at levels of -20 and
-5 cm respectively. The optimal groundwater level to minimize carbon dioxide emissions was 0 and -
5 cm.