a b s t r a c tThere is an urgent requirement to examine the quality of harvested rainwater for potable and nonpotable purposes, based on the type of roofing material. In this study, we examined the effect on the quality of harvested rainwater of conventional roofing materials (concrete, asphalt and ceramic tile roofs) compared with alternative roofing materials (green roof). The results showed that the ceramic tile roof was the most suitable for rainwater-harvesting applications because of the lower concentrations of leachable pollutants. However, in this study, the green roof was not suitable for rainwater harvesting applications. In addition, seasonal trends in water quality parameters showed that pollutants in roof runoff in summer and autumn were lower than those in winter and spring. This study revealed that the quality of harvested rainwater was significantly affected by the roofing material; therefore, local government and urban planners should develop stricter testing programs and produce more weathering resistant roofing materials to allow the harvesting of rainwater for domestic and public uses.
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.
a b s t r a c tThe effects of a continuing rise of ambient ozone on crop yield will seriously threaten food security in China. In the Yangtze River Delta, a rapidly developing and seriously air polluted region in China, innovative open-top chambers have been established to fumigate winter wheat and rice in situ with elevated O 3 . Five years of study have shown that the yields of wheat and rice decreased with increasing O 3 concentration. There were significant relationships between the relative yield and AOT40 (accumulated hourly O 3 concentration over 40 ppb) for both winter wheat and rice. Winter wheat was more sensitive to O 3 than rice. O 3 -induced yield declines were attributed primarily to 1000-grain weight and harvest index for winter wheat, and attributed primarily to grain number per panicle and harvest index for rice. Control of ambient O 3 pollution and breeding of O 3 tolerant crops are urgent to guarantee food security in China.
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