Ca-H-Al exchanges and aluminium mobility in two Chinese acidic forest soils: a batch experiment

Exchange reactions between Ca²⁺, H⁺ and Al species and their effects on the aluminium mobility in two Chinese acidic forest soils were studied. The study was based on a batch experiment using extractant solutions with different base cation (calcium) concentrations and pH. The experimental data showed that increased Ca²⁺ concentrations increased the release of soil hydrogen—and aluminium ions, especially from the more acid soil. In agreement with a cation exchange process, the treatment with Ca²⁺ extracts gave significantly decreased soil aluminium saturation (AlS) and increased calcium saturation (CaS) on the ion exchanger. Geochemical calculation using AlCHEMI program showed that activities of Al³⁺ in the extracts were all strongly under-saturated with respect to any gibbsite mineral in the studied pH region (i.e. below 4.1). There were instead apparently two different mechanisms controlling the activities of Al³⁺ in extracts. At pH between about 4.1 and 3.7, the Al³⁺ activity did not change significantly with pH. This is especially the case in the more acid soil. Apparently there are no sizeable pools available to release Al in this pH region. At pH below 3.7 (induced by higher Ca²⁺concentration) the activity of Al³⁺ increased with H⁺ though not in a pattern that complies with a gibbsite solubility control. An increase of base cation deposition would therefore mainly enhance the release of hydrogen ions between pH 4.1 and 3.7 and aluminium ions below pH 3.7 from Chinese mature acidic soils. This will cause an increased acidity of soil water in the short term and a decrease in the soil acidity in the long term. More attention should be paid to this fact in Chinese acid rain studies and control options.     

Depth-related influences on biodegradation rates of phenanthrene in polluted marine sediments of Puget Sound, WA

A whole-core injection method was used to determine depth-related rates of microbial mineralization of (14)C-phenanthrene added to both contaminated and clean marine sediments of Puget Sound, WA. For 26-day incubations under micro-aerobic conditions, conversions of (14)C-phenanthrene to (14)CO(2) in heavily PAH-contaminated sediments from two sites in Eagle Harbor were much higher (up to 30%) than those in clean sediments from nearby Blakely Harbor (<3%). The averaged (14)C-phenanthrene degradation rates in the surface sediment horizons (0-3 cm) were more rapid (2-3 times) than in the deeper sediment horizons examined (>6 cm), especially in the most PAH polluted EH9 site. Differences in mineralization were associated with properties of the sediments as a function of sediment depth, including grain-size distribution, PAH concentration, total organic matter and total bacterial abundance. When strictly anaerobic incubations (in N(2)/H(2)/CO(2) atmosphere) were used, the phenanthrene biodegradation rates at all sediment depths were two times slower than under micro-aerobic conditions, with methanogenesis observed after 24 days. The main rate-limiting factor for phenanthrene degradation under anaerobic conditions appeared to be the availability of suitable electron acceptors. Addition of calcium sulfate enhanced the first order rate coefficient (k(1) increased from 0.003 to 0.006 day(-1)), whereas addition of soluble nitrate, even at very low concentration (<0.5 mM), inhibited mineralization. Long-term storage of heavily polluted Eagle Harbor sediment as intact cores under micro-aerobic conditions also appeared to enhance anaerobic biodegradation rates (k(1) up to 0.11 day(-1)).     

甘肃省农村民居抗震设防现状与地震安全农居示范工程对策

本文根据甘肃省农村社会经济发展和地震环境特征,简要分析了甘肃农村民居主要建筑结构类型和抗震性能,结合近10多年来破坏性地震资料,总结了农村民居主要震害特点,提出了实施甘肃省农村民居地震安全工程的对策与措施。     

The potential transient dynamics of forests in New England under historical and projected future climate change

Projections of vegetation distribution that incorporate the transient responses of vegetation to climate change are likely to be more efficacious than those that assume an equilibrium between climate and vegetation. We examine the non-equilibrium dynamics of a temperate forest region under historic and projected future climate change using the dynamic ecosystem model LPJ-GUESS. We parameterized LPJ-GUESS for the New England region of the United Sates utilizing eight forest cover types that comprise the regionally dominant species. We developed a set of climate data at a monthly-step and a 30-arc second spatial resolution to run the model. These datasets consist of past climate observations for the period 1901?C2006 and three general circulation model projections for the period 2007?C2099. Our baseline (1971?C2000) simulation reproduces the distribution of forest types in our study region as compared to the National Land Cover Data 2001 (Kappa statistic?=?0.54). Under historic and nine future climate change scenarios, maple-beech-basswood, oaks and aspen-birch were modeled to move upslope at an estimated rate of 0.2, 0.3 and 0.5?m?yr^?1 from 1901 to 2006, and continued this trend at an accelerated rate of around 0.5, 0.9 and 1.7?m?yr^?1 from 2007 to 2099. Spruce-fir and white pine-cedar were modeled to contract to mountain ranges and cooler regions of our study region under projected future climate change scenarios. By the end of the 21^st century, 60% of New England is projected to be dominated by oaks relative to 21% at the beginning of the 21^st century, while northern New England is modeled to be dominated by aspen-birch. In mid and central New England, maple-beech-basswood, yellow birch-elm and hickories co-occur and form novel species associations. In addition to warming-induced northward and upslope shifts, climate change causes more complex changes in our simulations, such as reversed conversions between forest types that currently share similar bioclimatic ranges. These results underline the importance of considering community interactions and transient dynamics in modeling studies of climate change impacts on forest ecosystems.     

An analysis on observed and simulated PNA associated atmospheric diabatic heating

This study examines the PNA associated atmospheric diabatic heating by linearly isolating the influence of ENSO. The analysis is based on the NCEP–NCAR and ERA-40 reanalyses and a 1,000-year-long integration of the CCCma coupled climate model. Both the vertically integrated and three-dimensional diabatic heating are examined. The Rossby wave sources in association with the PNA are also diagnosed. The PNA-related heating is confined outside the tropics and is dominated by anomalies in the eastern Pacific, with a north–south dipole structure in mid-latitudes and the northern subtropics. The heating anomalies change sign with height in mid-latitudes but have the same sign throughout the troposphere in the northern subtropics. Relatively weak heating anomalies also appear in mid-latitudes, downstream of the heating dipole over North America and the western North Atlantic. The heating anomalies are largely supported by the advections related to the mean state throughout the troposphere, and partially damped by the advections related to the eddy effect, particularly at the upper troposphere over the North Pacific. Broadly similar patterns are seen from the NCEP–NCAR and ERA-40 reanalyses. Yet anomalous heating centers are generally located at relatively lower troposphere for the ERA-40 with respect to the NCEP–NCAR. The tropical heating anomalies are rather weak, remarkably different from those related to ENSO variability. In addition, the Rossby wave source collocates with the atmospheric diabatic forcing in the mid-high latitudes over the PNA sector, and shows no forcing source in the tropics. The results demonstrate possible forcing in the mid-high latitudes, regardless of tropical heating for the PNA teleconnection. The modeled heating and wave forcing anomalies in association with the modeled PNA compare reasonably well with the reanalysis-based estimates, increasing confidence in the observational results. The analysis provides further evidence of the independence of the PNA on ENSO from the diabatic heating point of view.     

重庆市主城区15年来酸雨变化趋势分析

本文运用重庆市主城区1993～2007年降水pH值监测资料,分析了重庆市最近15年来酸雨的变化趋势。结果表明,重庆市主城区降水pH值较低,15年来平均pH值介于3．8～4．5之间。重庆市年降水pH值基本呈递增趋势,倾向率达0．23／10a;最近5年的月际变化中,降水酸度夏高冬低,酸雨频率夏低冬高;各季节中,秋季pH值年际变化呈明显的波动状升高的趋势,其余3个季节呈弱波动,升降趋势不明显。重庆市酸雨（pH〈5．6）频率较高,各季节的酸雨频率基本在80％以上,且有增大的趋势;各季节中春季呈明显的升高趋势,其余季节略升高或趋势不明显。重庆市较强级别以上强度的酸雨（pH〈4．5）频率年际变化幅度较大,介于30～80％之间,变化趋势不明显。重庆市酸雨强度的变化主要受污染源排放量及其它因素的影响。     

桂林市低温冰冻过程特征分析

利用常规资料,欧洲资料分析了桂林冰冻日和冰冻过程的时空分布和长(≥6d)冰冻过程、短(＜6d)冰冻过程在51a平均场和距平场上的特征.     

浅谈气象短信的用语问题

气象短信即传送气象信息,又蕴含着气象服务的浓郁的人文关怀,因此正确使用词语尤为重要.遗憾的是,部分气象短信中存在用语不当、内容表述不够准确简练等问题,并分别举例进行论述,期望引起气象短信编写人员的重视.     

2009年11月北京极端低温和强降水事件分析

2009年10月底到11月底,包括北京在内的华北地区连续出现2次较强冷空气过程,造成大范围的低温、雨雪天气。利用北京地区11个气象站近50年逐日气温、降水资料,对全市历年11月低温雨雪事件的演变特征进行了分析。结果表明,2009年11月全市月平均气温、月平均最低气温均突破了50年的最低记录,月平均最高气温位列1981年11月之后,接近历史极值;2009年11月降雪量也位列有记录以来第一位,冰冻日数历史排位第三;从气温和降水极端事件发生的频次来看,2009年11月日平均气温、日最高气温和日最低气温通过5%分位值标准的极端低温事件频次都明显偏多,在50年中居于第2位,降水量通过95%分位值标准的极端强事件频次在50年中居于第四位。2009年11月的严重低温雨雪事件出现在区域气温总体变暖、低温事件频率总体下降的气候趋势背景下,在一定程度上放大了负面影响。亚洲中高纬地区500hPa高度场经向度异常加大、冷暖气流交换活跃,是造成2009年11月极端低温和大雪的直接环流因子。     

山西省主汛期极端变化降水特征

利用环渤海地区60个测站1961～2008年逐日降水资料,采用L矩参数估计方法对各站超临界值日极端降水拟合广义帕雷托分布。结果表明,广义帕雷托分布能够很好地拟合环渤海地区日极端降水的概率分布,其尺度参数、形状参数与极端降水重现期的地理空间分布密切相关,重现期50、100年一遇的日极端降水空间分布基本一致,山东南部、河北西南部、辽宁西部与河北东北部等区域具有较高极端降水值。