Peiqiang Hou

Effects of elevated O3 concentration on winter wheat and rice yields in the Yangtze River Delta, China

The 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.

Surface methane emissions from different land use types during various water levels in three major drawdown areas of the Three Gorges Reservoir

Methane (CH4) emissions from the drawdown area of the Three Gorges Reservoir (TGR) have not been thoroughly investigated even though the drawdown area encompasses one third of the reservoir surface. In this study, CH4 emissions from different land uses were measured in the TGR drawdown area. The average diffusive CH4 emissions were 2.61, 0.19, 0.18, and 0.12 mg CH4 m(-2) h(-1) in rice paddies, fallow lands, deforested lands, and croplands, respectively, and were positively related to the duration of the inundated season among the latter three land uses. On average the drawdown areas studied here (except rice paddies) were sources in the inundated season (0.22 +/- 0.26 mg CH4 m(-2) h(-1)) and a sink in the drained season (-0.008 +/- 0.035 mg CH4 m(-2) h(-1)). The water level was the dominant factor that controlled whether the drawdown area was either inundated or drained, which in turn determined whether the drawdown area was a source or sink of CH4 emissions. The average diffusive CH4 emissions from the fallow lands, croplands, and deforested lands increased as the distance from the dam increased from Zigui (0.10 +/- 0.15 mg CH4 m(-2) h(-1)) to Wushan (0.15 +/- 0.29 mg CH4 m(-2) h(-1)) to Yunyang (0.24 +/- 0.27 mg CH4 m(-2) h(-1)), which could reflect different sediment characteristics and water velocities. The total CH4 emission from the drawdown area was estimated to range from 1033.5 to 1333.9 Mg CH4 yr(-1), which would account for 42-54% of the total CH4 emissions from the water surface of TGR.

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

With the open-top chambers (OTCs) in situ in Yangtze River Delta, China in 2007 and 2008, the effects of elevated O₃ exposure on nutrient elements and quality of winter wheat and rice grain were investigated. Grain yield per plant of winter wheat and rice declined in both years. The N and S concentrations increased under elevated O₃ exposure in both years and C-N ratios decreased significantly. The concentrations of K, Ca, Mg, P, Mn, Cu and Zn in winter wheat and the concentrations of Mg, K, Mn and Cu in rice increased. The concentrations of protein, amino acid and lysine in winter wheat and rice increased and the concentration of amylose decreased. The increase in the nutrient concentration was less than the reduction of grain yield in both winter wheat and rice, and, hence, the absolute amount of the nutrients was reduced by elevated O₃.

Quality and seasonal variation of rainwater harvested from concrete, asphalt, ceramic tile and green roofs in Chongqing, China

There is an urgent requirement to examine the quality of harvested rainwater for potable and non-potable 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.

Soil warming effect on net ecosystem exchange of carbon dioxide during the transition from winter carbon source to spring carbon sink in a temperate urban lawn.

The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback of urban lawn in warmed environment. Soil warming effect on net ecosystem exchange (NEE) of carbon dioxide during the transition period from winter to spring was investigated in a temperate urban lawn in Beijing, China. The NEE (negative for uptake) under soil warming treatment (temperature was about 5 degrees C higher than the ambient treatment as a control) was -0.71 micromol/(m2 x sec), the ecosytem was a CO2 sink under soil warming treatment, the lawn ecosystem under the control was a CO2 source (0.13 micromol/(m2 x sec)), indicating that the lawn ecosystem would provide a negative feedback to global warming. There was no significant effect of soil warming on nocturnal NEE (i.e., ecosystem respiration), although the soil temperature sensitivity (Q10) of ecosystem respiration under soil warming treatment was 3.86, much lower than that in the control (7.03). The CO2 uptake was significantly increased by soil warming treatment that was attributed to about 100% increase of alpha (apparent quantum yield) and Amax (maximum rate of photosynthesis). Our results indicated that the response of photosynthesis in urban lawn is much more sensitive to global warming than respiration in the transition period.