Correlation between meteorological parameters and nitrogen compounds present in wastewater in the formation of nitrous oxide in soils

Abstract

In the present work, nitrous oxide emissions were estimated [mg/L] by the use of lysimeters under the closed chamber technique for a six month period. The lysimeters were classified by the type of irrigation used: one for drinking water, and the other for treated wastewater. Each lysimeter had two different types of soil (sand and clay), based on the types of soil in Chihuahua City, Mexico. An additional classification based on the depth was done (reticular and vadose zone). Each zone collected gas by the use of a closed chamber technique, allowing the samples to be taken for subsequent quantification and analysis by gas chromatography. A statistical analysis of variance (ANOVA) and principal components analysis (PCA) were conducted to identify the most influential variables or parameters in the formation of nitrous oxide. The variables that were considered for analysis were total Kjeldahl nitrogen (TKN), ammoniacal nitrogen (NH3-N), nitrate nitrogen (NO3-N), and nitrite nitrogen (NO2-N), along with meteorological parameters. In total, 58944 mg/L of N2O were emitted during the measurement period. The results showed that concentration emissions of N2O where the type of soil is sandy were smaller than those of clay soil, while the mean concentration in the vadose zone was higher than those in the reticular zone, regardless the type of soil. The parameters that showed greater influence in the N2O emissions were NO2-N and NO3-N concentrations. Temperature also played an important role in the emissions (the highest emissions were emitted during the cold months). Furthermore, denitrification appeared to be the dominant process in the production of nitrous oxide in soils. Implications: Nitrous oxide (NO) emissions produced in lysimeters with two types of soil (sand and clay) at two different depths (vadose and reticular zones) using treated waste water showed that the higher emissions of NO are derived from clay soils in vadose zone; it could be due to the formation of clogging that favors the formation of anoxic conditions for the denitrification process. The parameters that showed more influence in the NO emissions were nitrite (NO-N) and nitrate (NO-N) concentrations along with the temperature.

Treated wastewater viability of use in green areas according to nitrogen compounds concentration

“…Clay soils have instead slower vertical downward flow due to smaller pores. Establishing anaerobic conditions nitrogen can be obtained as a gas that will escape to the atmosphere by means of the denitrification process (Bojorquez et al 2018).…”

“…In clays, the removal of N-NO 2 and N-NO 3 , produced by one meter of soil column is not enough, the smaller pores and lower permeability produce a slower vertical downward flow. It must be considered that in clay soils there may be slightly anaerobic conditions, so by means of the denitrification process, nitrogen will be obtained as a gas that will escape to the atmosphere (Bojorquez et al 2018). In soils with clay presence, it is necessary to confirm the existence of sand layers that are at least one meter thick.…”

“…This was raised with the conceptual model in Figure 3. The lysimeter's geometric design was the same used by Bojorquez et al (2018). Each lysimeter measured 50 cm  50 cm  100 cm, it was made of acrylic, and had a thickness of 10 mm.…”