Atmospheric Methyl Bromide (CH3Br) from Agricultural Soil Fumigations

The treatment of agricultural soils with CH(3)Br (MeBr) has been suggested to be a significant source of atmospheric MeBr which is involved in stratospheric ozone loss. A field fumigation experiment showed that, after 7 days, 34 percent of the applied MeBr had escaped into the atmosphere. The remaining 66 percent should have caused an increase in bromide in the soil; soil bromide increased by an amount equal to 70 percent of the applied MeBr, consistent with the flux measurements to within 4 percent. Comparison with an earlier experiment in which the escape of MeBr to the atmosphere was greater showed that higher soil pH, organic content and soil moisture, and deeper, more uniform injection of MeBr may in combination reduce the escape of MeBr.     

A Net Sink for Atmospheric CH3Br in the East Pacific Ocean

Surface waters along a cruise track in the East Pacific Ocean were undersaturated in methyl bromide (CH(3)Br) in most areas except for coastal and upwelling regions, with saturation anomalies ranging from + 100 percent in coastal waters to -50 percent in open ocean areas, representing a regionally weighted mean of -16 (-13 to -20) percent. The partial lifetime of atmospheric CH(3)Br with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6) years. The global, mean dry mole fraction of CH3Br in the atmosphere was 9.8 +/- 0.6 parts per trillion, with an interhemispheric ratio of 1.31 +/- 0.08. These data indicate that approximately 8 percent (0.2 parts per trillion) of the observed interhemispheric difference in atmospheric CH3Br could be attributed to an uneven global distribution of oceanic sources and sinks.     

Atmospheric Trends and Lifetime of CH3CCI3 and Global OH Concentrations

Determination of the atmospheric concentrations and lifetime of trichloroethane (CH(3)CCI(3)) is very important in the context of global change. This halocarbon is involved in depletion of ozone, and the hydroxyl radical (OH) concentrations determined from its lifetime provide estimates of the lifetimes of most other hydrogen-containing gases involved in the ozone layer and climate. Global measurements of trichloroethane indicate rising concentrations before and declining concentrations after late 1991. The lifetime of CH(3)CCI(3) in the total atmosphere is 4.8 +/- 0.3 years, which is substantially lower than previously estimated. The deduced hydroxyl radical concentration, which measures the atmosphere's oxidizing capability, shows little change from 1978 to 1994.     

Quantum Yield for Production of CH3NC in the Photolysis of CH3NCS

The ultraviolet spectrum of methyl isothiocyanate (CH(3)NCS) and the quantum yield for its dissociation into methyl isocyanide (CH(3)NC) and atomic sulfur at 308 nanometers, Phi = 0.98 +/- 0.24, were measured. Methyl isothiocyanate is widely used as an agricultural fumigant and readily enters the atmosphere during and after application. The results indicate that photodissociation by sunlight is an effective pathway for its removal from the atmosphere.     

自由大气CO2浓度升高对稻田CH4排放的影响研究

采用FACE田间试验,对高CO2:浓度影响稻田CH4排放规律进行了观测分析,并利用δ13C技术初步分析了土壤CH4的排放来源.结果显示,植株和±壤的CH4排放速率在高CO2浓度处理大于对照18%以上,其增加幅度为土壤大于植物,CH4排放速率可能受田间水分条件影响较大.与对照比较,高CO2浓度条件下植物和土壤部分CH4累积排放总量增加,且变化幅度随生长期而降低,前期(54 d)常规氮处理(NN)高于低氮处理(LN),后期LN高于NN;但是行间裸土CH4累积排放总量在前期(54d)增加和之后降低的幅度均为NN高于LN.土壤排放CH4δ13C值从移栽到第102 d,高CO2浓度处理LN和NN水平下土壤对照(CK)仅分别升高9.0%和8.3%,种水稻则降低8.8%和8.1%;但是在对照CO2浓度条件下土壤对照降低17.2%和112.5%(P=0.047),种水稻降低40.3%和105.9%(P=0.023),表明高CO2浓度下有更多C4来源的碳释放,对照CO2浓度条件下有更多C3来源的碳释放.水稻不同生长期与土壤对照比较,种水稻土壤排放CH4δ13C值降低的幅度总和在高CO2浓度条件LN和NN水平下分别为114.8%和72.7%,对照CO2浓度条件下分别为41.9%和72.8%,表明在种有植物的情况下更多当季的碳分解释放,LN水平下高CO2浓度促进来源于当季碳的CH4排放.NN水平下没有发现CO2浓度的影响,可能与作物生物量和它的间接产物(根系分泌物)的影响有关.     

海涂土壤电导率的空间变异性研究

运用地统计方法对海涂土壤电导率的空间变异性进行了深入的分析．结果表明,土壤电导率的空间变异可分为系统变异和随机变异两类,系统变异由微地形、土壤管理等外在环境因素决定,因此不同采样区的系统变异存在差异,其中表层土壤的系统变异明显强于深层土壤;而在不同采样区求得的随机变异结构稳定相似并存在套合结构,它们的变程不受采样方向和采样时间的影响．     

Supra-canonical 26Al/27Al and the residence time of CAIs in the solar protoplanetary disk

The canonical initial 26Al/27Al ratio of 4.5 x 10(-5) has been a fiducial marker for the beginning of the solar system. Laser ablation and whole-rock multiple-collector inductively coupled plasma-source mass spectrometry magnesium isotope analyses of calcium- and aluminum-rich inclusions (CAIs) from CV3 meteorites demonstrate that some CAIs had initial 26Al/27Al values at least 25% greater than canonical and that the canonical initial 26Al/27Al cannot mark the beginning of solar system formation. Using rates of Mg diffusion in minerals, we find that the canonical initial 26Al/27Al is instead the culmination of thousands of brief high-temperature events incurred by CAIs during a 10(5)-year residence time in the solar protoplanetary disk.     

重庆市植烟土壤基础环境信息空间变异性分析

采用SPSS软件,对重庆主要植烟区土壤的各项基础环境信息数据进行处理,计算出各项基础环境的相应统计学参数,并分析其在不同尺度上的空间变异性。结果表明:重庆市多数植烟土壤的酸碱度适宜烟草种植,碱解N含量偏低且空间变异较大,速效P整体缺乏但局部空间变异大,速效K含量高且空间变异小;有效B整体缺乏且空间变异小,有效Mo含量丰富且空间变异小,有效Fe整体含量中等但局部变异大,有效Mn整体不缺但局部空间变异大,有效Zn整体含量低且空间变异小;交换性Ca2 含量丰富且空间变异小,交换性Mg2 整体缺乏且空间变异小,交换性S2 含量丰富且空间变异小,CEC整体含量适中且空间变异小。     

CH3·与CO反应机理的理论研究

采用密度泛函B3LYP/6-311G**和QC ISD(T)/6-311G**方法计算研究了CH3.与CO反应机理,全参数优化了反应势能面上各驻点的几何构型,用内禀反应坐标(IRC)计算和频率分析方法,对过渡态进行了验证。研究结果表明:CO对CH3.自由基有稳定化作用。该反应的研究将为烃类的燃烧和大气环境的保护提供理论依据。     

Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum

Assessing the impact of future anthropogenic carbon emissions is currently impeded by uncertainties in our knowledge of equilibrium climate sensitivity to atmospheric carbon dioxide doubling. Previous studies suggest 3 kelvin (K) as the best estimate, 2 to 4.5 K as the 66% probability range, and nonzero probabilities for much higher values, the latter implying a small chance of high-impact climate changes that would be difficult to avoid. Here, combining extensive sea and land surface temperature reconstructions from the Last Glacial Maximum with climate model simulations, we estimate a lower median (2.3 K) and reduced uncertainty (1.7 to 2.6 K as the 66% probability range, which can be widened using alternate assumptions or data subsets). Assuming that paleoclimatic constraints apply to the future, as predicted by our model, these results imply a lower probability of imminent extreme climatic change than previously thought.     

不同地形条件下样点密度对土壤养分空间变异的影响

以湖南省安仁县的豪山乡(山地地形)和渡口乡(丘陵区)为研究对象,根据传统统计学和地统计学的相关原理,运用变异函数分析法和空间插值估计法,研究耕地土壤养分碱解氮含量、有效磷含量、速效钾含量、有机质含量的空间变异及其分布特征,研究不同地形条件样点密度对插值精度的影响。结果表明：土壤养分变异系数为16.56% ~97.9%,属于中等变异;山地地区碱解氮含量、速效钾含量、有机质含量的基底效应值<25%,丘陵区有机质含量、碱解氮含量的基底效应值为38.15% ~74.45%,2种地形有效磷含量的基底效应值为88.44% ~100%;根据研究区土壤养分的空间变异情况,建议山地区采样密度为0.16个/hm2,丘陵区采样密度为0.10个/hm2。     

Fatness of the total body as estimated from measurements on the eviscerated carcass

In mice of the genetically obese strain with body fatness below 28 percent, fatness of the eviscerated carcass equaled fatness of the total body. Above 28 percent, the two values diverged with the eviscerated carcass being the higher. In the fattest individuals the prediction of total body fatness from measurements made on the eviscerated carcass may be in error by + 6.5 percent-fatness. When total body fatness exceeded about 25 percent, visceral depots no longer participated proportionately, and probably did not participate at all in further fat accretion.     

Normalization of the crop water stress index to assess the within-field spatial variability of water stress sensitivity

Precision Agriculture - This paper presents a novel methodology for identifying homogeneous areas within high-frequency drip-irrigated orchards and for defining the most sensitive and resistant...     

Towards an empirical model to estimate the spatial variability of grapevine phenology at the within field scale

Precision Agriculture - The aim of this study is to propose an empirical spatial model to estimate the spatial variability of grapevine phenology at the within-field scale. This spatial model...     

安徽省17地市旅游开发的空间关联分析

从空间关联的视角出发,运用空间统计分析方法对安徽省17个地市旅游开发的空间关联度进行数据分析.选取2009年安徽省17个地市人均旅游收入为观测值,通过计算全局空间自相关指数(Global Moran's I),发现其旅游开发在整体上存在着显著的空间自相关.进一步计算各地市的局部空间自相关指数(Local Moran's...     

Evaluation of spatial and temporal variability of pasture based on topography and the quality of the rainy season

Yield and botanical composition of a given dry-land pasture are heavily influenced by rainfall distribution, and vary according to topography. Through analyzing these parameters, it is possible to identify patterns of spatial distribution, related to topographic characteristics, which can be used to improve spatial management of pasture. The main objective of this project was to assess the role of rainfall, temperature and topography in the spatial and temporal variability of pasture and establish models for predicting the spatial distribution and yield of certain plant species, based on its topographic characteristics. This study was carried out over three years, 2004 to 2006, in a dry-land pasture located in Southern Portugal. The data obtained were analyzed as a function of distance to flow lines and the results demonstrate that certain topographical characteristics, associated with agronomic information, can be very useful in explaining the spatial and temporal variability of yield and the botanical composition of the pasture. The slope of the linear regression of the variables mentioned can be used to estimate the spatial variation of yield and the botanical composition as a function of distance to flow lines. The regression coefficient can be estimated from the annual rainfall, given the strong correlation between the two.     

Steric control of the reaction of CH stretch-excited CHD3 with chlorine atom

Exciting the CH-stretching mode of CHD(3) (where D is deuterium) is known to promote the C-H bond's reactivity toward chlorine (Cl) atom. Conventional wisdom ascribes the vibrational-rate enhancement to a widening of the cone of acceptance (i.e., the collective Cl approach trajectories that lead to reaction). A previous study of this reaction indicated an intriguing alignment effect by infrared laser-excited reagents, which on intuitive grounds is not fully compatible with the above interpretation. We report here an in-depth experimental study of reagent alignment effects in this reaction. Pronounced impacts are evident not only in total reactivity but also in product state and angular distributions. By contrasting the data with previously reported stereodynamics in reactions of unpolarized, excited CHD(3) with fluorine (F) and O((3)P), we elucidate the decisive role of long-range anisotropic interactions in steric control of this chemical reaction.     

甲醛处理在西瓜种子室内发芽中的应用

通过西瓜种子室内发芽方法的摸索、比较 ,发现用体积分数 0 .2 %的甲醛处理种子 10min可以预防霉床现象 ,且对种子无任何毒害作用 ,从而解决了某些西瓜种子由于霉床现象造成的室内芽率结果偏低这一问题。     

农业产值空间变异性研究——以广西壮族自治区为例

【目的】以广西壮族自治区（以下简称广西）农业产值为研究对象,利用地统计学方法探究广西农业产值的空间变异特征,并揭示其空间分异格局对相关因素的响应规律,为农业决策管理部门的农区分类管理和精准农业提供科学参考。【方法】文章首先通过四倍法去除异常值并通过样本代表系数校验获取采样样本70个,然后利用经典统计学方法得出样本的统计特征值并进行分析,最后运用地统计学理论分析广西地区农业生产信息的空间变异性特征,并运用Kriging插值法和莫兰指数对广西农业产值的空间格局进行分析。【结果】广西农业产值的原始数据和对数变换的变异系数分别是61%和21%,属于中等变异性;通过理论模型拟合结果对比选取Gaussian模型进行拟合,其块金效应为0.226%;最后,使用莫兰指数进行空间自相关分析,其全局莫兰指数为0.327 661,表明其空间分布不是随机的,内部存在明显空间集聚性。【结论】广西的农业产值的空间变异特征主要受其结构性因素影响,随机性因素对该区域的空间变异性影响较小,分析其空间发现,农业产值的空间分布特征与地形地貌的空间分布具有一定相似性,通过空间自相关分析探究其集聚性,总体上广西农业产值高高值集聚...     

Production limits analysis of rain-fed maize on the basis of spatial variability of soil factors in North China

Precision Agriculture - In precision agriculture, suitable soil moisture and nutrient levels are important for crop production. Therefore, studying the spatial variability in soil moisture and...