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Direct infiltration of roof runoff into the ground may pose a potential risk of soil and groundwater contamination. The performance of two different barrier materials for the retention of zinc from roof runoff of an eleven year old zinc roof was examined in a field study. As barrier materials geotextile and clinoptilolite were applied. Automatic samplers were used to take samples both at the inlet and at the outlet of the retention facility. Samples of twenty rain events were examined. Zinc was detected in the roof runoff in concentrations of up to 25 mg/L, and lead which originates from the tin‐solder was present in concentrations of up to 84 μg/L. Under most circumstances, a first flush could be observed for the analysed substances. No retention of heavy metals was observed, where only geotextile was used as a barrier material. The clinoptilolite filter was able to adsorb up to 97 % of zinc from the roof runoff. 相似文献
43.
The necessary condition for the seismic refraction method to succeed is that the refracted first arrivals from each layer in a multilayered earth system should be detected on a seismogram as first arrivals, and this is possible only when velocities of all underlying layers are successively greater. The usual procedure to interpret the refraction travel times is to fit such a data set with several intersecting straight lines by employing a visual technique which may lead to errors of subjective judgment, as the velocity model depends on the selection of various line segments through the data. To remove the visual fit we propose here a layer stripping method based on minimum intercept time, apparent velocity, rms residual, and maximum data points by least-squares fitting to yield several intersecting straight lines. Once data are segmented out, the conventional equations can be used to determine the velocity structure. 相似文献
44.
本文介绍了频率域线源大地电磁法有限元正演模拟的研究结果. 在外边界上统一应用适合于人工源的一阶吸收边界条件来形成边值问题,可减小基于平面波假设造成的人为截断边界的影响. 程序编辑中设计了两个二维数组分别存储总体系数矩阵的非零元素和在总体结点编号中的位置,使内存占用量减少,且物理意义明确,方便用高斯-赛德尔等迭代法解有限元方程时调用. 采用视δ函数模拟线源,提高了解方程组的稳定性. 最后通过对1个简单模型和1个复杂模型的模拟,证明所用的方法对异常体能够有明显的反映,说明了该方法的可靠性和有效性. 相似文献
45.
Active Source Seismic Identification and Automatic Picking of the P-wave First Arrival Using a Convolutional Neural Network 总被引:1,自引:1,他引:0
XU Zhen WANG Tao XU Shanhui WANG Baoshan FENG Xuping SHI Jing YANG Minghan 《中国地震研究》2019,33(2):288-304
In seismic data processing, picking of the P-wave first arrivals takes up plenty of time and labor, and its accuracy plays a key role in imaging seismic structures. Based on the convolution neural network (CNN), we propose a new method to pick up the P-wave first arrivals automatically. Emitted from MINI28 vibroseis in the Jingdezhen seismic experiment, the vertical component of seismic waveforms recorded by EPS 32-bit portable seismometers are used for manually picking up the first arrivals (a total of 7242). Based on these arrivals, we establish the training and testing sets, including 25,290 event samples and 710,616 noise samples (length of each sample:2s). After 3,000 steps of training, we obtain a convergent CNN model, which can automatically classify seismic events and noise samples with high accuracy (> 99%). With the trained CNN model, we scan continuous seismic records and take the maximum output (probability of a seismic event) as the P-wave first arrival time. Compared with STA/LTA (short time average/long time average), our method shows higher precision and stronger anti-noise ability, especially with the low SNR seismic data. This CNN method is of great significance for promoting the intellectualization of seismic data processing, improving the resolution of seismic imaging, and promoting the joint inversion of active and passive sources. 相似文献
46.
为了研究二氧化碳物理相变技术应用于新型震源研发的可行性,在地下成层性较好的某煤田地震测区,开展了利用二氧化碳相变技术激发地震波的野外人工震源激发-接收实验.并与传统炸药震源进行了对比.地震数据利用Aries2.66型垂直分量反射地震仪和PDS-2型三分量地震仪接收.根据实测地震数据,从野外地震记录震相识别,初至波传播距离分析,震源近场地震信号时频分析,CO_2相变激发震源子波提取和基于CO_2震源子波的地震初至波波形反演实验等多个方面,进行了关于CO_2相变激发技术能否产生地震波信号以及能否将其应用于新型震源研发的可行性研究.研究结果表明CO_2物理相变膨胀能够产生能量集中的地震波信号;在实验区地质条件和激发参量下地震记录中初至波的可识别的传播距离约为1km;震源近场地震信号的主频集中在8~13Hz;利用震源近场数据提取了CO_2震源子波;通过地震初至波波形反演实验认为这种震源子波能够应用于波形反演等方面的研究.因为CO_2相变激发具有绿色、环保、安全等方面的优点,若能进一步在激发能量、激发—延迟时间一致性等方面加以改进,该技术有望在城市隐伏活动断层探测、城市地下空间探测、煤矿高瓦斯环境人工地震勘探等领域发挥重要的作用. 相似文献
47.
综合利用区域台站和流动台站(近台)的记录,基于初至P震相重新测定了2017年九寨沟序列M_S7.0主震和M_L≥3.0余震的震源位置,并利用较高精度的定位结果分析余震分布与地震构造的关系,解释发震断裂带的结构.获得的新认识有:(1)九寨沟主震震源深度为16km,位于余震带中段的南缘;余震主要分布深度为4~17km.(2)沿余震带的走向,余震分布与主震同震位错大小的分布明显相关.余震带中段8~16km深度存在的余震稀疏区与同震位错的高值区相吻合,应是发震断裂带主凹凸体的部位,也是主震时应变释放较充分的部位;余震带南东段10~18km深度的余震密集区对应了同震位错的亏损区之一,三次M_L≥5.0余震都发生于此;余震带西北段在5~10km之下既缺少余震,又属同震位错的亏损区,可能与那里多条断裂的交汇或合并造成的构造复杂性有关;余震带中-北西段3~5km深度的也缺少余震,也对应了浅部的同震位错亏损区.(3)证实了九寨沟地震的发震构造为虎牙断裂带北段,同时新揭示出发震断裂带表现为由主断裂和分支断裂构成的、向上分叉的花状结构,尺度约为4.5km宽(最大)、35km长,主断裂朝SW陡倾.这些反映主震破裂可能不只受控于单一的断裂,而有可能是沿主断裂发生主破裂,而沿分支断裂发生次要破裂.另外,本文对发震断裂带结构的分段解释,是遵循构造地质学原理去综合震源排列、震源机制解、地表断层已知位置、相邻剖面断层解释结果等信息的分析结果,而不仅仅依据余震的密集分布进行推断. 相似文献
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49.
River biofilms are dominant riverine biota with diverse microorganisms. They have been found to contribute greatly to river self‐purification for removal of nutrients and organic matter. This study intended to investigate the ability of naturally occurring river biofilms with changing seasons for the removal of the organophosphorus pesticide diazinon. Natural river biofilms from spring showed higher ability to remove diazinon (99.9% removal) than those from winter (77%) with light exposure. In contrast to control sets without biofilms under irradiation, 27% of diazinon removal in spring and 22% in winter may result from microbial activity within biofilms. Removal of diazinon by river biofilms could be attributed mostly to degradation due to low sorption capacity of biofilms. Spring biofilms had higher dissipation rates (0.265 and 0.486 d?1 for biofilms with different growth periods) than winter ones (0.099 and 0.119 d?1) according to first order model. Higher ability of diazinon removal by spring biofilms may be explained by their higher bacterial and algal biomass comparing to winter biofilms. Naturally occurring river biofilms played a significant role in degradation of diazinon, particularly for those grown in spring. Their potential for use in the treatment of diazinon‐contaminated water has been demonstrated. 相似文献
50.
地震波在沙丘中的传播速度与沙丘厚度密切相关.利用延迟时反演高速顶界时,采用常速或插值方法求取表层速度,不能正确反应这种变化关系,使反演模型底界存在误差,影响静校正精度.利用微测井成果数据拟和得到时深曲线,再利用延迟时从时深曲线求取表层速度和厚度可有效解决此问题.方法为:解释和分析地震微测井数据→应用地震微测井或有代表性表层结构线段拟合时深曲线→利用野外单炮初至时间获取表层延迟时→应用延迟时与时深曲线反演近地表结构模型→静校正量计算.应用结果表明,该方法快速有效,在M10JQ3D中获得较好效果. 相似文献