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841.
J. Mohapl 《Environmental monitoring and assessment》2001,72(1):1-35
The objective of this study is to decide if chemical concentrations measured during 1988-1997in precipitation by the Canadian Air and Precipitation Monitoring Network (CAPMoN) indicate changes in the annual patterns. The inference is based on SO4, NO3, Cl,NH4, Na, Ca and K concentrations monitored daily with the rain water acidity pH. By pattern is understood the probability distribution of the annual sample at a particular location. Most of the annual data can be well described by means of a linear regression model with second order polynomial trend and autocorrelated noise. Statistical analysis based on the model shows luck of systematic significant year to year increases or declines of the concentrations. 相似文献
842.
利用气相色谱/燃烧/同位素比值质谱(GC/C/IRMS)分析技术,采用NaHSO3与半胱胺衍生化方法,测定了气态乙醛在衍生化反应过程中的碳同位素效应,探讨了采用该方法测定大气乙醛碳同位素组成的可行性。试验测定了乙醛、衍生剂半胱胺及相应衍生物的碳同位素比值,结果表明,乙醛衍生物的δ13C测量值与理论值的偏差范围为0.11‰~0.35‰,在仪器精密度范围内(<0.50‰),即在衍生化过程中基本不会发生碳同位素分馏。采用该方法初步测定了大气中乙醛的碳同位素组成,实测数据显示,广州地化所和肇庆鼎湖山大气乙醛δ13C平均值分别为(-34.21±0.27)‰和(-31.23±0.16)‰,相同采样点的大气乙醛碳同位素组成基本不变,可见该方法可作为研究大气乙醛不同排放源的一种有效方法。 相似文献
843.
采用能源弹性系数分析法,利用统计年鉴和环境影响评价报告书提供的数据,对山西省火电行业产生的大气污染状况进行了研究.结果表明:在现阶段的常规模式发展下,山西省火电行业污染严峻,将在很大程度上加剧当前山西省大气污染严重的态势;定义火电生产弹性系数为0.8时的发展方式为预警模式,在该模式下污染可得到一定控制;只有当进入火电生产弹性系数为0.5的和谐模式发展时,才能大幅减少SO2和NOx的排放.建议通过采取强化宏观调控、严格审批以及加强技术改造,将山西省火电行业的火电生产弹性系数控制在0.8以下. 相似文献
844.
土壤-水体系中固/液比对溶解性石油烃吸附的影响 总被引:1,自引:0,他引:1
采用批实验的方法,研究了2种土壤在不同的固/液比(solid-to-solution ratio,SSR)条件下对溶解性石油烃(DPH)的吸附-解吸特性.结果表明,DPH在土壤中的吸附-解吸等温线符合线性方程;解吸表现出明显的滞后现象,滞后因子随SSR的升高而增加,随土壤有机碳含量(OC)的升高而减小,对于OC=1.54%的稻田土,当SSR从10.00 g·L-1变化至75.00 g·L-1,DPH的解吸滞后因子从1.43升高到2.21;对于OC=15.91%的黑土,当SSR从2.50 g·L-1变化至5.00 g·L-1,DPH的解吸滞后因子从1.18升高到1.37.说明吸附的不可逆性随SSR的升高而增强,随土壤有机碳含量的升高而减弱.另外,研究发现由吸附等温线计算得到的kOC随SSR的升高(不可逆性的增强)而减小,在此基础上建立了固定体系中kOC与SSR的关系模型,用于预测实际环境中DPH在土-水界面的迁移. 相似文献
845.
846.
Sophie Beltran Frank Cézilly Jérôme Boissier 《Behavioral ecology and sociobiology》2009,63(9):1363-1368
“Divorce” (mate switching) rate is known to vary largely both between and within socially monogamous species. Although the
adult sex ratio can have an important influence on mating patterns, very few studies have investigated the influence of sex
ratio on divorce rate in monogamous species, and even less so from an experimental point of view. In addition, most studies
on the causes and consequences of divorce have been performed on vertebrate species, whereas data for invertebrate monogamous
species remain scarce. Schistosoma mansoni is a monogamous endoparasite with a complex life cycle characterized by asexual reproduction in the intermediate host and
sexual reproduction in the definitive host. In the wild, populations of S. mansoni inside their definitive hosts are characterized by a male-biased sex ratio. We studied the influence of experimentally varying
the adult sex ratio on divorce rate in S mansoni, using controlled infections of hosts with clonal populations. The more male-biased the sex ratio was, the more the divorce
rate increased, whereas no such effect was observed under a female-biased sex ratio. In this study and for the first time,
we showed, by handling the sex ratio, that the divorce rate increases in adult male-biased sex ratio conditions in a monogamous
species. 相似文献
847.
WARM (Water Accounting Rice Model) simulates paddy rice (Oryza sativa L.), based on temperature-driven development and radiation-driven crop growth. It also simulates: biomass partitioning, floodwater effect on temperature, spikelet sterility, floodwater and chemicals management, and soil hydrology. Biomass estimates from WARM were evaluated and compared with the ones from two generic crop models (CropSyst, WOFOST). The test-area was the Po Valley (Italy). Data collected at six sites from 1989 to 2004 from rice crops grown under flooded and non-limiting conditions were split into a calibration (to estimate some model parameters) and a validation set. For model evaluation, a fuzzy-logic based multiple-metrics indicator (MQI) was used: 0 (best) ≤ MQI ≤ 1 (worst). WARM estimates compared well with the actual data (mean MQI = 0.037 against 0.167 and 0.173 with CropSyst and WOFOST, respectively). On an average, the three models performed similarly for individual validation metrics such as modelling efficiency (EF > 0.90) and correlation coefficient (R > 0.98). WARM performed best in a weighed measure of the Akaike Information Criterion: (worst) 0<wk<1 (best), considering estimation accuracy and number of parameters required to achieve it (mean wk=0.983 against 0.007 and ∼0.000 with CropSyst and WOFOST, respectively). WARM results were sensitive to 30% of the model parameters (ratio being lower with both CropSyst, <10%, and WOFOST, <20%), but appeared the easiest model to use because of the lowest number of crop parameters required (10 against 15 and 34 with CropSyst and WOFOST, respectively). This study provides a concrete example of the possibilities offered using a range of assessment metrics to evaluate model estimates, predictive capabilities, and complexity. 相似文献
848.
Changes in carbon use efficiency (CUE), which is defined as the ratio of net primary production (NPP) to gross primary production (GPP), were analyzed for Abies veitchii Lindl. forests with respect to stand development by developing a simple mathematical model incorporating data on physiological variables and leaf mass ratio. A decrease in CUE with stand development was successfully expressed as a function of stand biomass (y) based on the following three assumptions: (1) a power-law relationship between mean respiration and mean individual tree mass, (2) a power-functional relationship between mean gross primary production and mean individual tree mass, and (3) self-thinning relationship between stand biomass and density. Based on this model, a parameter of CUE–y relationship was defined, and it was clarified that CUE decrease with stand development is caused not by the ratio of specific respiration rate to specific gross photosynthetic rate, but by leaf mass ratio. Since CUE is high in young forests, helpful information on selecting woody species when planting seedlings was provided from the viewpoints of reducing CO2 in the atmosphere and global warming. 相似文献
849.
850.
酸沉降对马尾松菌根共生蛋白及营养关系影响 总被引:6,自引:0,他引:6
研究模拟酸雨及不同Ca/Al比对马尾松(Pinusm assoniana Lam b.)菌根中真菌与植物共生及营养关系的影响,在分子水平上揭示污染对生物的作用和生物抗性机理.当pH20 的模拟酸雨与铝共同作用时,马尾松菌根中酸性磷酸酶、硝酸还原酶以及海藻糖酶和甘露醇脱氢酶活性明显下降,即pH20 的模拟酸雨及铝离子对马尾松幼苗根的磷、氮吸收以及两共生生物之间的营养物质交换过程产生了影响,且铝离子在pH值低的情况下毒性作用更强;而钙能有效地缓解铝的毒性⒚在本实验中当Ca/Al比为1/1 时,缓解能力最强;在接种外生菌根真菌彩色豆马勃(Pisolithustinctorius)后,马尾松幼苗根部酶活性仍能保持一定水平,植物对模拟酸雨及铝毒的抗性增强.菌根形成初期,经等点聚焦电泳后分离出在植物及真菌纯培养中均不存在的共生蛋白,其等电点为470,经pH20的模拟酸雨处理后该蛋白仍存在 相似文献