Natural attenuation of residual heavy metal contamination in soils affected by the Aznalcóllar mine spill, SW Spain

Non-amended soils affected by pyritic sludge residues were monitored for 7 years to assess the long-term natural attenuation ability of these soils. The decrease in both the total concentration of elements (particularly As) and (NH(4))(2)SO(4)-extractable fractions of Mn, and Zn, below the maximum permissible levels indicate a successful natural ability to attenuate soil pollution. Soil acidification by pyrite oxidation and rainfall-enhanced leaching were the largest contributors to the reduction of metals of high (Mn, Cu, Zn and Cd) and low (Fe, Al, and As) availability. Periodic use of correlation and spatial distribution analysis was useful in monitoring elemental dispersion and soil property/element relationships.     

Seasonal variation of atmospheric polycyclic aromatic hydrocarbons along the Kaohsiung coast

Thirty-three air samples were collected by high-volume samplers from May 2007 to June 2008 in the coastal area of southwest Taiwan and analyzed for total suspended particulates (TSP) and polycyclic aromatic hydrocarbons (PAHs). Concentrations of TSP and total PAHs ranged from 40.4 to 251 μg m(-3) and 1.86-56.4 ng m(-3), respectively. Except for joss paper burning during the religious celebration of Ghost Month, which resulted in the highest concentration of PAHs in the summer of 2007, a seasonal variation in total PAH concentration was observed over this study period, with the highest concentrations in winter and the lowest in summer. Because of the geographical and climatic characteristics of the sampling site, monsoon activities modulate the seasonal variations of PAHs. Diagnostic ratios showed that PAHs in the atmosphere of the Kaohsiung coastal area arose predominantly from vehicle emissions (mainly from diesel exhaust), joss paper burning, and coal/wood combustion. The results of hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicated that the sampling days could be divided into three groups and that the major source identification of PAHs was the same as the identification by diagnostic ratios. In addition, the results of HCA and PCA suggest that the samples collected with a prevailing northerly or northeasterly wind direction contain both local emissions and those from neighboring sources. On the other hand, the cases related to westerly or northwesterly winds indicated that local emission was the major source for the sampling site.     

荞麦不同器官总黄酮含量的日变化研究

研究荞麦初花期不同器官总黄酮含量的日变化趋势、最佳取样时间和取样部位,为养麦的综合开发利用提供理论依据.对4份来自不同地区的甜荞和苦养不同器官的总黄酮含量进行了日变化研究.结果表明,一天中同一品种不同器官中的黄酮含量均表现为花>叶>茎>根,且花和叶中的含量显著大于茎和根,不同品种各器官中总黄酮含量的日变化差异较大.     

Climate, canopy conductance and leaf area development controls on evapotranspiration in a boreal coniferous forest over a 10-year period: A united model assessment

The aim of this work was to test a process-based model (hydrological model combined with forest growth model) on the simulation of seasonal variability of evapotranspiration (ET) in an even-aged boreal Scots pine (Pinus sylvestris L.) stand over a 10 year period (1999-2008). The water flux components (including canopy transpiration (E_t) and evaporation from canopy (E_c) and ground surface (E_g) were estimated in order to output the long-term stand water budget considering the interaction between climate variations and stand development. For validation, half-hourly data on eddy water vapor fluxes were measured during the 10 growing seasons (May-September). The model predicted well the seasonal course of ET compared to the measured values, but slightly underestimated the water fluxes both in non-drought and drought (2000, 2003 and 2006) years. The prediction accuracy was, on average, higher in drought years. The simulated ET over the 10 years explained, on average, 58% of the daily variations and 84% of the monthly amount of ET. Water amount from E_t contributed most to the ET, with the fractions of E_t, E_c and E_g being, on average, 67, 11 and 23% over the 10-year period, respectively. Regardless of weather conditions, the daily ET was strongly dependent on air temperature (T_a) and vapor pressure deficit (D_a), but less dependent on soil moisture (W_s). On cloudy and rainy days, there was a non-linear relationship between the ET and solar radiation (R_o). During drought years, the model predicted lower daily canopy stomatal conductance (g_cs) compared with non-drought years, leading to a lower level of E_t. The modeled daily g_cs responded well to D_a and W_s. In the model simulation, the annual LAI increased by 35% between 1999 and 2008. The ratio of E_c: ET correlated strongly with LAI. Furthermore, LAI reduced the proportion of E_g as a result of the increased share of E_c and E_t and radiation interception. Although the increase of LAI affected positively E_t, the contribution of E_t in ET was not significantly correlated with LAI. To conclude, although the model predicted reasonably well the seasonal course of ET, the calculation time steps of different processes in the model should be homogenized in the future to increase the prediction accuracy.     

半干旱黄土区退耕还林十年植被恢复变化分析——以陕西吴起县为例

黄土高原退耕还林（草）政策实施已逾10 a,了解植被恢复变化状况及存在的问题,对于制定和完善生态环境治理方略具有重要意义。以吴起县为例,基于实地调查及遥感等数据,对退耕还林（草）以来植被覆盖度、主要植被类型变化及不同立地条件下植被恢复变化的差异进行了定量分析。结果表明：2000年至2009年,植被覆盖度大于30%的面积在全县总面积中的比例由不足1%上升至91.96%;其中缓坡立地类型上的乔灌林地类型面积增长最为显著,而阳向陡坡等恶劣生境下的植被恢复缓慢;有林地、灌木林地及疏林地均呈现规模增大趋势,属扩张状态;中覆盖度草地、低覆盖度草地、坡耕地及耕地呈现规模减少趋势,属缩减状态。     

黄土高原陆地表层最大可能蒸散量的变化特征

基于黄土高原1961—2008年月平均气温、最高气温、最低气温、相对湿度、降水量、风速和日照百分率等气候要素资料,应用修订的Penman-Monteith（P-M）模型计算了最大可能蒸散量,分析其时空分布、异常分布特征和次区域时间演变特征。结果表明：1961—2008年间,黄土高原最大可能蒸散量多年平均在400~800 mm之间,大部分区域650~750 mm之间。一致性异常分布是黄土高原最大可能蒸散量的最主要空间模态。黄土高原最大可能蒸散量的异常空间分布可分为以下3个关键区：高原西北部区、高原东北部区和高原东南部区。高原西北部区域最大可能蒸散量呈显著增加趋势,且发生了突变现象;高原东北部区域最大可能蒸散量呈显著下降的趋势,也发生了突变;而高原东南部区域下降趋势不显著,未发生突变。黄土高原最大可能蒸散量的3个空间分区中,3 a的周期振荡表现得比较显著。     

基于长时间序列的北京PM2.5浓度日变化及气象条件影响分析

基于2005~2014年北京宝联(城区)和上甸子大气成分本底站(郊区)监测结果得到了PM_(2.5)质量浓度日变化特征,并且讨论了气象条件的影响.结果表明,北京城区PM_(2.5)质量浓度10年平均值的日变化呈双峰分布,对应早晚出行高峰.但是,该特征在2007年以后才比较明显.月际(季节)变化表现为单峰与双峰之间、日最大值在早高峰与晚高峰之间的转换.一年中早峰值浓度在5~8月最高,与地面风速小、相对湿度以及水汽压(空气绝对含水量)较高有关,该季节晚高峰期间浓度变化相对较小主要受混合层较厚、地面风速大、降雨天气发生频繁的影响.11~12月和1~2月的16:00以后浓度明显升高,混合层顶高度在14:00~17:00大幅度下降是重要的影响因素.此外,严重和重度污染日09:00以后污染加重,与年平均值和中度污染日不同.边界层偏南风对来自周边地区高架源的污染物输送是其重要的影响机制.PM_(2.5)质量浓度日变化幅度随污染加重而增大.日最大风速和相对湿度日变化对浓度日变化幅度有影响,而且午后地面出现4~6 m·s-1的偏南风也会加大日变化幅度.北京郊区PM_(2.5)质量浓度多年平均值日变化呈单峰分布,日最大值超前于城区.而且,昼间的浓度在5~7月高于冬季.本研究结果将有助于细化不利扩散条件下的污染减排方案.     

Growth and nutrient accumulation of Phragmites australis in relation to water level variation and nutrient loadings in a shallow lake

Shallow lake eutrophication is a global environmental issue. This study investigated the effects of water level variation and nutrient loadings on the growth and nutrient accumulation of Phragmites australis (reed) by field samplings in Baiyangdian Lake, the largest shallow lake of northern China. The field samplings were conducted in two sites of different nutrient loadings during the whole growth period of reeds, and three types of zones with different water depths were chosen for each site, including the terrestrial zone with water level below the ground, the ecotone zone with the water level varying from belowground to aboveground, and the submerged zone with water level above the ground. The result showed that reed growth was more limited by water level variation than nutrient loadings. The average stem lengths and diameters in terrestrial zones were about 26.3%-27.5% and 7.2%-12.0% higher than those in submerged zones, respectively. Similarly, the terrestrial status increased the aboveground biomass of reeds by 36.6%-51.8% compared with the submerged status. Both the nutrient concentrations and storages in the aboveground reeds were mainly influenced by the nutrient loadings in surface water and sediment rather than the water level variation of the reed growth environment, and the nutrient storages reached their maxima in late August or early September. It was observed that the maximum nitrogen storage occurred in the terrestrial zone with higher nutrient loadings, with the value of 74.5 g/m 2 . This study suggested that water level variation and nutrient loadings should be considered when using reeds to control and remediate eutrophication of shallow lakes.     

丹江口库区小流域土壤磁化率变异特征及影响因素研究

土壤磁化率是表征土壤侵蚀特征的重要指标。本文以丹江口库区五龙池流域土壤为研究对象,沿坡位选取18个条带共采集85个表层(0～10 cm)土壤样品,通过对不同土地利用类型及景观位置的土壤磁化率分析以及与粒度关联分析,揭示小流域土壤磁化率变异特征并评估其影响因素。结果表明:1)土壤质量磁化率、频率磁化率平均含量分别为34. 4×10-8m3/kg、9. 69%,二者均呈中等的空间自相关,其值分别为0. 59、0. 51; 2)不同土地利用类型中,土壤磁化率差异显著,其中质量磁化率为坡耕地梯田灌木林地用材林地;频率磁化率为坡耕地梯田用材林地灌木林地;不同景观位置上,土壤磁化率坡顶最低,中部最高,坡底居中; 3)土壤磁化率与黏粒、粉粒含量存在显著正相关关系,与砂粒含量呈显著负相关关系。研究结果为间接监测流域土壤迁移与环境演变过程提供了依据,增加对流域内生源元素伴随土壤侵蚀迁移的演变历史和过程的理解,对于保护库区水环境和生态安全有重要意义。