Measurement of methane emissions from a rice field using manual head-space sampling in closed chambers

Date

10-2008

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Josefina L. Solivas

Co-adviser

Maxima E. Flavier

Committee Member

Hidelisa P. Hernandez

Abstract

Methane (CH4) emission rates were determined using closed chambers. Gas samples were collected using transparent chambers with 60 cm x 60 cm base and 122.5 cm height during a ten-minute interval for thirty minutes. The set up which included four chambers collected gas samples during 9:00 AM and 2:00 PM based on the completed preliminary experiments. The gas samples were analyzed using Shimadzu Gas Chromatograph equipped with Flame Ionization Detector. Preliminary tests were conducted on the chambers and syringes to ensure that there will be no or at least negligible losses on the sample during handling from the field to the laboratory. Also a separate preliminary test was done to determine the optimum sampling time. The set up which was composed of four chambers along a gradient from the irrigation source showed highest methane emission rates at the chamber nearest to the source. Soil temperature generally governed the methane emission patterns among the four sampling points. Soil reduction potential gave a weak inverse relationship with the emission rates. Soil methane emissions were found to be supported by pH readings ranging from 6.3 to7.3 all throughout the season. Peak emission was at 12.81 mg CH4 m2 in the afternoon of 37 DAT which was 222.08% of the average morning and afternoon emissions all throughout the season. On the other hand, the minimum CH, emission rate was determined 16 DAT in the morning with a rate of 0.20 mg CH. m2 (6.43 % of the average morning and afternoon emissions over the season). Emissions during the wet season ranged from 0.20 mg CH., m.2 to 9.46 mg CH4 m2 h-1 (average of four chambers) in the morning and from 0.37 mg CH4 nit lit and 12.81 mg CH4 m2 h1' in the afternoon (average of four chambers). Statistical analysis using Wilk-Shaphiro test showed that the emission rates in the morning and in the afternoon followed the normal distribution at 5% level of significance. The analysis based on Levene's test showed that the variances of both the emission rates during the morning and afternoon readings are the same. The estimated amount of methane emitted from the soil to the atmosphere was at 138.24 kg CH4 per hectare per season.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2008 C4 L66

Document Type

Thesis

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