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921.
Characteristics of distribution and transport of petroleum contaminants in fracture-karst water in Zibo Area, Shandong Province, China 总被引:8,自引:0,他引:8
Fracture-karst water is an important water resource for the water supply in North China. Petroleum contamination is one of
the most problematic types of the groundwater pollution. The characteristics of distribution and transport of the petroleum
contaminants in fracture-karst water are different from those in porous water. The flow velocity of fracture-karst water is
much faster than the velocity of porous water on an average. Therefore, contaminant transport in fracture-karst water is an
absolute advection-dominated problem. The plume of the petroleum contamination may extend to several kilometers from pollution
sources. It was not caused by the oil pool floating on the water table but by the oil components dissolved and scattered in
groundwater. The distribution of the petroleum contaminants over space are concentrated in the strong conductive zone on the
plane. On the vertical section the highest concentration of the oil contaminants appeared in the strata where the contamination
sources were located. The concentrations of the oil contaminants in wells changed greatly over time. Therefore, the curves
of concentration versus time fluctuated greatly. The reasons are as follows. (a) Fracture-karst water has a very great velocity.
(b) Local flow fields which were caused by pumping and stoppage in some wells changed frequently. (c) In fracture-karst aquifer
the transport channels are complicated. (d) Residual oil in vadose zone was leached after rainfall. It is of great practical
value for the control and remediation of petroleum contamination in fracture-karst aquifer to understand those characteristics. 相似文献
922.
本文中作者采用红外光谱方法对雅鲁藏布江蛇绿岩带拉昂错超基性岩体二辉橄榄岩中的单斜辉石进行了测试研究。结果表明 ,雅鲁藏布江蛇绿岩带拉昂错岩体二辉橄榄岩中的单斜辉石为透辉石 ;该透辉石中含有一定量的结构水 ;并且 ,其高频带相关的结构OH含量是 1 4 6× 1 0 -6。透辉石成分的这种特殊性 (含有结构OH)恰恰是其特殊的高温高压的幔源生成环境的反映。 相似文献
923.
通过对葫芦河流域与已知优质苹果产区———五方河流域之间土壤养分、盐量和微量元素的丰缺水平对比研究,证实葫芦河流域新积土无论常量养分、可溶性岩离子含量,还是微量元素含量水平总体高于五方河流域的新积土,土质更优于黄绵土,具备开发为优质果品生产基地的地质条件。为土地资源的利用和生态环境保护提供了新的依据。 相似文献
924.
古尔班通古特沙漠土壤养分空间分异与干扰的关系 总被引:16,自引:11,他引:5
对干扰条件下古尔班通古特沙漠土壤养分空间分异特征进行了研究。分析土壤养分的变化趋势,及干扰与植被和土壤养分之间的关系。研究表明:沙漠边缘至沙漠腹地,全N、全P和全K含量、EC、总盐,可溶性离子HCO-3、SO2-4及Ca2+呈增加趋势。CO2-3、Mg2+、 Cl-、Na+4种离子含量较低,变化规律不明显。除全K含量随公路里程呈较连续的增加外,其他养分条件在公路里程25—75 km ,80—125 km和大于125 km的范围内的变化趋势都呈现高\?低\?显著增高的波动过程,分析表明这种波动性的变化是由干扰造成的。干扰因子数与生物结皮盖度呈显著负相关,但与植物种类与植物盖度都达到了显著正相关的水平。除与pH值呈正相关外,干扰因子数与土壤养分指标都呈负相关,其中与全K、全P、全N和EC的负相关接近于显著或极显著水平。随公路里程增加,生物结皮呈现从地衣苔藓藻类地衣地衣苔藓的过渡,这与土壤养分条件和干扰因子数相对应。人类活动是导致彩克沙漠公路里程80—125 km范围沙漠土壤养分条件的降低的主要原因,受水源和居住地的影响,该段沙漠人类放牧活动影响的最大范围为里程125—145 km之间。人类在沙漠活动的加强会增加沙漠生态干扰源和干扰强度,最终降低沙漠土壤的养分条件。 相似文献
925.
PIV技术及其在风沙边界层研究中的应用 总被引:2,自引:2,他引:0
为了考察粒子图像测速度技术在风沙环境风洞中的测量精度及在风沙边界层研究中的应用潜力,通过筛选适当的示踪颗粒,借助PIV测量系统重新测量了风沙环境风洞中的风廓线,并获得了风沙边界层内跃移沙粒的速度和浓度分布规律。实验结果表明:PIV测得的风速廓线与标准风速廓线仪所测结果相当吻合(R2≥0.99);沙粒跃移的平均水平速度和相对浓度(灰度)沿距离沙面高度分别呈幂函数和负指数分布,沙粒速度随高度和自由风速的增加而增大,相对浓度随高度的增加而快速衰减,风速越小衰减越快,风速越大衰减越慢,这一结果与前人的结论一致。PIV系统为将来能够进行更加精确的风沙运动微观机理研究提供了技术保证。 相似文献
926.
Abstract. Hg, Cd, Pb and Zn concentrations were determined in sediment and in tissues of five species of soft-bottom marine macrophytes ( Posidonia oceanica, Cymodocea nodosa, Zostera noltii, Ruppia cirrhosa and Caulerpa prolifera ) along the Spanish Mediterranean coast. Levels of metals were low in most of the sampling stations and similar to those found by other authors in uncontaminated zones. Certain locations, however, showed some degree of contamination (Cambrils, Almassora, Alacant, Mar Menor and El Portús). In Santa Pola we found high contents of metals in one sample of sediment due to the high proportion of the fine fraction (particules < 63µm) and organic matter, but not in the seagrass species. Mercury and zinc concentrations in the sediment are correlated to those in at least some anatomic fractions of Posidonia oceanica, Cymodocea nodosa and Caulerpa prolifera , suggesting that these species reflect the levels of these metals in the environment. Lead contents in the alga Caulerpa prolifera are also correlated to those in the sediment, while no significant correlations were obtained for cadmium. Among the species studied, Posidonia oceanica and Cymodocea nodosa seem to be better biomonitors than Caulerpa prolifera . 相似文献
927.
928.
Changes in fossil midge (Chironomidae) assemblages in response to cultural activities in a shallow, polymictic lake 总被引:6,自引:0,他引:6
Chironomid (Diptera: Chironomidae) head capsules were studied from a core of recent sediments from shallow, macrophyte-dominated Lake Opinicon, Ontario, Canada, to determine if assemblages have changed in response to lake-level changes and other watershed disturbances, including deforestation and agriculture. Our results indicate that the construction of the Rideau Canal in the early 1830s and subsequent flooding of Lake Opinicon has had the greatest impact on this system, but that even this disturbance did not greatly affect chironomid assemblages. Despite other significant cultural disturbances in the watershed, the lake sediments have recorded only minor changes in its recent history, providing support for the hypothesis of alternative lake equilibria. These results correspond well with diatom inferences of only minor changes in past lake trophic status. 相似文献
929.
930.
风沙流中沙粒随机运动的数值模拟研究 总被引:15,自引:8,他引:7
通过对描述沙粒垂向运动速度脉动分量的随机微分方程的直接求解,获得了风沙流中沙粒运动的随机轨迹。结果表明,由于沙粒垂向脉动速度的影响,沙粒的轨迹与不考虑其垂向脉动速度的情形存在明显不同。在此基础上,通过对大量轨迹的统计计算,得到了沙粒浓度的分布规律。 相似文献