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901.
Accumulation and risk of heavy metals in relation to agricultural intensification in the river sediments of agricultural regions 总被引:1,自引:1,他引:0
The enrichment characteristics and risk of heavy metals were studied in the sediments of Liucha River in Chao Lake Valley, where agricultural intensification has developed rapidly since the 1980s. The results revealed that Cd, Pb and Zn showed the lowest levels in the upper reaches and peak values in the lower reaches, increasing from 0.064, 7.75 and 59.75 mg/kg to 0.176, 12.33 and 96.82 mg/kg on average, respectively. Enrichment factor (EF) analysis showed that the EF values of Cd, Pb and Zn (maximum 4.76, 2.51 and 2.74, respectively) all increased from the upper reaches to the lower reaches (>1.5), while correlation analysis and cluster analysis showed that they primarily originated from the extensive use of phosphate fertilizer. In addition, the comprehensive potential ecological risk due to Cd, Cr, Cu, Ni, Pb and Zn in the sediments showed low degree, but Cd showed moderate and high risk at some sites. Therefore, heavy metal pollution due to agricultural intensification in the agricultural regions of Chao Lake Valley should be given great attention during management of the water environment. 相似文献
902.
Hong Zhang Baoqing Shan Liang Ao Wenzhong Tang Shengfang Wen 《Environmental Earth Sciences》2014,72(2):399-406
A complete record derived from a core dated both by 210Pb and 137Cs chronologies from Lake Ngoring at the headwater areas of the Yellow River provides new insight into the changing atmospheric deposition of trace metals including Cd, Cr, Cu, Ni, Pb, and Zn. This study showed that there was an inflection in the early 1960s, before which both fluxes and contents of Cd, Ni, Pb, and Zn remained relatively steady or slowly increased, and thereafter continued increases both in fluxes and contents were found. Taking Pb as an example, the flux increased from 0.13 (before 1960) to 0.25 mg m?2 a?1 (averaged 1963–2006). According to atmospheric flux calculations using Al as a reference element, atmospheric fluxes of trace metals generally showed a rapid increase and peaked in recent years, closely following the historical economic development of the neighboring region, mainly for Qinghai and Gansu provinces. The atmospheric inventory for Zn was the highest, reaching 1.068 g m?2, while the lowest was for Cd, at only 0.079 gm?2. The percentage proportions of atmospheric deposition for Cd, Ni, and Zn were 37, 12, and 8.7 %, respectively. Hence, the atmospheric contribution to the trace metal content via long range transport is not negligible when considering input of materials to lake ecosystems. 相似文献
903.
904.
中亚前陆盆地地层中氧同位素和孢粉,以及黄土高原和北太平洋粉尘记录均表明,中中新世(16~12 Ma)中亚地区气候干旱化显著增强。然而,对其驱动机制的认识不一,包括全球降温、中亚地区的构造抬升、高海拔的"原西藏高原"的存在、副特提斯洋的退缩以及上述几者联合作用的结果。不过,全球降温(约14 Ma)、"原西藏高原"的抬升(≥40 Ma)、以及副特提斯洋退缩的时间(34 Ma)与中中新世中亚气候干旱化增强的时间(16~12 Ma)不一致。因此,它们可能是导致中中新世中亚干旱化增强的重要边界条件,或者是有利的辅助条件,但没起直接的主导作用。对塔里木盆地东南缘江尕勒萨伊剖面的前期研究结果表明,阿尔金山快速抬升始于16 Ma。在获得了磁性地层年龄的基础上,前人的碳氧同位素数据指示了16 Ma江尕勒萨依地区气候干旱化逐渐增强。鉴于同时发生,笔者把16 Ma气候干旱化增强归因于此时阿尔金山的快速抬升。从更广范围看,中中新世中亚发生了广泛的的地壳缩短变形和造山运动。对中国黄土高原的红粘土以及北太平洋粉尘沉积的多指标分析(磁化率、粒径、粉尘通量以及物源等)表明,中中新世中亚构造抬升及其引起的雨影效应是中亚气候干旱化增强的主因。 相似文献
905.
906.
目前基坑管井回灌设计及优化尚无专门成熟的方法,通过不同基坑回灌类型的分析,提出了基坑管井回灌设计原则及设计流程,并对回灌参数进行了探讨,对回灌可施加的最大压力进行了分析,通过285组基坑水文地质数值模型的计算,对比分析了不同渗透各向异性系数、回灌井结构、回灌井位置和保护建(构)筑物位置下的渗流特征,提出了回灌设计综合指数,从经济、技术及施工难度角度综合评估回灌对保护建(构)筑物以及对坑内降水的双重作用,指导抽灌一体化设计。 相似文献
907.
通过对大同市某变电站下伏采空区治理的实例,介绍了采空区治理方法的选择和实施过程,探讨了采空区注浆加固治理工程设计理念,总结了施工过程中各种问题的解决方法和成功经验。 相似文献
908.
909.
比勒提地区位于新疆西南天山,以该区1:50000高精度磁测数据为基础,采用解析延拓、方向导数等技术手段提取与断裂构造有关的磁异常信息,对区域内构造进行识别,结合标本物性参数统计,对引起磁异常的原因进行分析。对区域磁异常向上延拓及求一阶导数后进行对比,圈定4个特征异常带A1-A4,结合地质资料,识别出4条断裂构造FW1-FW4,FW1和FW2对应喀拉铁克断裂及其次级断裂,FW3为构造动力作用产生的强片理化带,FW4为隐伏断裂,表明高精度磁法测量在本区能有效识别断裂并反映其分布。 相似文献
910.
Based on thermal simulation experiment, interactions between volcanic fluids and source rocks were studied. Gas generations in the dry system and fluid system under different temperatures were analyzed. The results showed that the various types of source rocks are similar in composition, containing gaseous C1-C5 hydrocarbons, H2 and CO2 whose gas yields increase with increasing temperature. The gas yield of source rocks of type I is the high- est, followed by type II, and that of source rocks of type III is the lowest, indicating that the yield of hydrocarbon gases is related to their hydrocarbon generating potential. Although the generating potential of type III is the lowest, it can still be regarded as a useful gas source when it is buried deeply enough. The basic volcanic fluid restrains the generation of gaseous hydrocarbons in different types of source rocks, but promotes the generation of inorganic gases. 相似文献