Effects of elevated ozone concentration on methane emission from a rice paddy in Yangtze River Delta, China

Abstract

Few investigations have been made on the impact of elevated ozone (O 3 ) concentration on methane (CH 4 ) emission from rice paddies. Using open-top chambers in situ with different O 3 treatments, CH 4 emissions were measured in a rice paddy in Yangtze River Delta, China in 2007 and 2008. There were four treatments applied: charcoal-filtered air (CF), nonfiltered air (NF), and charcoal-filtered air with different O 3 additions (O 3 -1 and O 3 -2). The mean O 3 concentrations during the O 3 fumigation were 19.7, 22.6, 69.6 and 118.6 ppb in 2007 and 7.0, 17.4, 82.2 and 138.3 ppb in 2008 for treatments CF, NF, O 3 -1 and O 3 -2, respectively. The rice yields, as compared with CF, were reduced by 32.8% and 37.1%, 58.3% and 52.1% in treatments O 3 -1 and O 3 -2 in 2007 and 2008, respectively. The diurnal patterns of CH 4 emission varied temporally with treatments and there was inconsistence in diurnal variations in CH 4 emissions from the paddy field. The daily mean CH 4 emissions were significantly lower in treatments O 3 -1 and O 3 -2 than those in treatments CF and NF. Compared with CF treatment, CH 4 emissions from the paddy field were decreased to 46.5% and 38.3%, 50.6% and 46.8% under treatments O 3 -1 and O 3 -2 in the whole growing seasons of 2007 and 2008, respectively. The seasonal mean CH 4 emissions were negatively related with AOT40 (accumulative O 3 concentration above 40 ppb; Po0.01 in both years), but positively related to the relative rice yield (reference to CF; Po0.01 in 2007 and Po0.001 in 2008), aboveground biomass (Po0.01 in both years) and underground biomass (Po0.01 in 2007 and Po0.05 in 2008). The decreased CH 4 emission from the rice paddy due to an increased O 3 exposure might partially mitigate the global warming potential induced by soil carbon loss under elevated O 3 concentrations.

Effects of elevated O3 exposure on nutrient elements and quality of winter wheat and rice grain in Yangtze River Delta, China

“…The annual mean temperature is 15.9 C; the annual precipitation is 1169 mm and the annual sunshineduration is 2017 h (Zheng et al, 2011). The prevailing cropping pattern is wheatrice or rape-rice rotation.…”

“…The regular octagon open-top chamber (OTCs, 2.2 m in height and 2 m in diameter) was made of aluminum alloy frame covered with polyethylene plastic film (Zheng et al, 2011). The ambient air or O 3 added air delivered by a centrifugal blower was released from down holes in automatically-rotating pipes.…”

“…Since 2003, open-top chambers (OTCs) have been used to investigate the effects of elevated O 3 exposure on winter wheat and rice in physiological processes (Zheng, 2006;Zheng et al, 2007), yield (Wang et al, , 2012, soil microorganism (Chen et al, 2008(Chen et al, , 2010, agroecosystem (Zheng et al, 2011), in Yangtze River Delta, China. The objectives of this study is to investigate the changes of nutrient elements and quality of winter wheat and rice grain under the elevated O 3 exposure.…”

Preliminary report on methane emissions from the Three Gorges Reservoir in the summer drainage period

“…The chromatographic column was filled with XMSfiller of 60-80 mesh, 2 m in length and 2 mm in diameter. The flow rates of the carrier gas (N 2 ), fuel gas (H 2 ) and compressed air were 30, 20 and 30 mL/min, respectively (Zheng et al, 2011b). The standard CH 4 gas (10.2 ppm in air; provided by Chinese CRM/RM Information Center) was used to quantify the CH 4 concentrations for every 15 samples.…”

“…The July 2010 flood removed the chamber bases from Wushan cropland sites and Yunyang wilderness and deforested sites; new bases were positioned in almost the same locations. The static transparent chamber technique was employed to collect gas samples in rice paddies (Zheng et al, 2011b). This technique used a steel-frame chamber (50 cm in length, 50 cm in width and 75 cm in height) covered with polyethylene plastic film (85% transparency).…”