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Bio-nanocatalysts (BNCs) consisting of horseradish peroxidase (HRP) self-assembled with magnetic nanoparticles (MNPs) enhance enzymatic activity due to the faster turnover and lower inhibition of the enzyme. The size and magnetization of the MNPs affect the formation of the BNCs, and ultimately control the activity of the bound enzymes. Smaller MNPs form small clusters with a low affinity for the HRP. While the turnover for the bound fraction is drastically increased, there is no difference in the H2O2 inhibitory concentration. Larger MNPs with a higher magnetization aggregate in larger clusters and have a higher affinity for the enzyme and a lower substrate inhibition. All of the BNCs are more active than the free enzyme or the MNPs (BNCs > HRP ≫ MNPs). Since the BNCs show surprising resilience in various reaction conditions, they may pave the way towards new hybrid biocatalysts with increased activities and unique catalytic properties for magnetosensitive enzymatic reactions.

Few investigations have been made on the impact of elevated ozone (O3) concentration on methane (CH4) emission from rice paddies. Using open-top chambers in situ with different O3 treatments, CH4 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 O3 additions (O3-1 and O3-2). The mean O3 concentrations during the O3 fumigation were 19.7, 22.6, 69.6 and 118.6ppb in 2007 and 7.0, 17.4, 82.2 and 138.3ppb in 2008 for treatments CF, NF, O3-1 and O3-2, respectively. The rice yields, as compared with CF, were reduced by 32.8% and 37.1%, 58.3% and 52.1% in treatments O3-1 and O3-2 in 2007 and 2008, respectively. The diurnal patterns of CH4 emission varied temporally with treatments and there was inconsistence in diurnal variations in CH4 emissions from the paddy field. The daily mean CH4 emissions were significantly lower in treatments O3-1 and O3-2 than those in treatments CF and NF. Compared with CF treatment, CH4 emissions from the paddy field were decreased to 46.5% and 38.3%, 50.6% and 46.8% under treatments O3-1 and O3-2 in the whole growing seasons of 2007 and 2008, respectively. The seasonal mean CH4 emissions were negatively related with AOT40 (accumulative O3 concentration above 40ppb; 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 CH4 emission from the rice paddy due to an increased O3 exposure might partially mitigate the global warming potential induced by soil carbon loss under elevated O3 concentrations.

Th is publication was based on work supported by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). Experimental details of the synthesis and characterization of the sorbent. Adsorption and desorption of the sorbent.

Methane emissions from hydroelectric reservoirs can comprise a considerable portion of anthropogenic methane. However, lack of data on CH(4) emissions in different geographical regions and high spatial-temporal variability in the emission rates of reservoirs has led to uncertainties regarding regional emission estimates of CH(4). In the subtropical plateau climate region, we used the Ertan hydroelectric reservoir as a study area. The CH(4) flux at the air-water interface was assessed by floating chambers and factors influencing emissions, including the distance from the dam, water depth, seasonal variation in wet and dry season, air-water temperature gradient and wind speed, and was also studied through a year-long systematic sampling and monitoring experiment. The results showed that the surface of the reservoir was a source of CH(4) during the sampling period and the annual average CH(4) flux was 2.80 +/- 1.52 mg m(-2) d(-1). CH(4) flux (and its variation) was higher in the shallow water areas than in the deep-water areas. CH(4) flux near the dam was significantly higher than that of other locations farther from the dam in the dry season. The seasonal variations of CH(4) emission in wet and dry seasons were minor and significant diurnal variations were observed in wet and dry seasons. Exponential relationships between the CH(4) flux and air-water temperature gradient were found. Air-water temperature gradient was an important factor influencing diurnal variations of CH(4) flux in the Ertan hydroelectric reservoir. These results indicate that systematic sampling is needed to better estimate CH(4) flux through coverage of the spatial variation of different water depths, measuring-point distance from the dam, seasonal variation in wet and dry seasons and changes in climate factors (such as air-water temperature gradient). Our results also provide a fundamental parameter for CH(4) emission estimation of global reservoirs. Copyright (C) 2010 John Wiley a Sons, Ltd.

Based on the carbon-nitrogen cycles and greenhouse gas (GHG) mitigation and emission processes related to straw return and burning, a compound greenhouse gas budget model, the "Straw Return and Burning Model" (SRBM), was constructed to estimate the net mitigation potential of straw return to the soil in China. As a full GHG budget model, the SRBM addressed the following five processes: (1) soil carbon sequestration, (2) mitigation of synthetic N fertilizer substitution, (3) methane emission from rice paddies, (4) additional fossil fuel use for straw return, and (5) CH4 and N2O emissions from straw burning in the fields. Two comparable scenarios were created to reflect different degrees of implementation for straw return and straw burning. With GHG emissions and mitigation effects of the five processes converted into global warming potential (GWP), the net GHG mitigation was estimated. We concluded that (1) when the full greenhouse gas budget is considered, the net mitigation potential of straw return differs from that when soil carbon sequestration is considered alone; (2) implementation of straw return across a larger area of cropland in 10 provinces (i.e., Shanghai, Jiangsu, Zhejiang, Fujian, Jiangxi, Hubei, Hunan, Guangdong, Guangxi, and Hainan) will increase net GHG emission; (3) if straw return is promoted as a feasible mitigation measure in the remaining provinces, the total net mitigation potential before soil organic carbon (SOC) saturation will be 71.89 Tg CO2 equivalent (eqv)/yr, which is equivalent to 1.733% of the annual carbon emission from fossil fuel use in China in 2003; (4) after SOC saturation, only 13 of 21 provinces retain a relatively small but permanent net mitigation potential, while in the others the net GHG mitigation potential will gradually diminish; and (5) the major obstacle to the feasibility or permanence of straw return as a mitigation measure is the increased CH4 emission from rice paddies. The paper also suggests that comparable scenarios in which all the related carbon-nitrogen cycles are taken into account be created to estimate the mitigation potentials of organic wastes in different utilizations and treatments.

Soil as the largest global carbon pool has played a great role in sequestering the atmospheric carbon dioxide (CO(2)). Although global carbon sequestration potentials have been assessed since the 1980s, few investigations have been made on soil carbon sequestration (SCS) in China's cropland. China is a developing country and has a long history of agricultural activities. Estimation of SCS potentials in China's cropland is very important for assessing the potential measures to prevent the atmospheric carbon rise and predicting the atmospheric CO(2) concentration in future. After review of the available results of the field experiments in China, relationships between SCS and nitrogen fertilizer application, straw return and no-tillage (NT) practices were established for each of the four agricultural regions. According to the current agricultural practices and their future development, estimations were made on SCS by nitrogen fertilizer application, straw return and NT in China's cropland. In the current situation, nitrogen fertilizer application, straw return and zero tillage can sequester 5.96, 9.76 and 0.800 Tg C each year. Carbon sequestration potential will increase to 12.1 Tg C yr(-1) if nitrogen is fertilized on experts' recommendations. The carbon sequestration potentials of straw return and NT can reach 34.4 and 4.60 Tg C yr(-1) when these two techniques are further popularized. In these measures, straw return is the most promising one. Full popularization of straw return can reduce 5.3% of the CO(2) emission from fossil fuel combustion in China in 1990, which meets the global mean CO(2) reduction requested by the Kyoto Protocol (5.2%). In general, if more incentive policies can be elaborated and implemented, the SCS in China's cropland will be increased by about two times. So, popularization of the above-mentioned agricultural measures for carbon sequestration can be considered as an effective tool to prevent the rapid rise of the atmospheric CO(2) in China.