Diurnal variations of saltation activity at Tazhong: the hinterland of Taklimakan Desert

The Taklimakan Desert of China is a region of frequent sandstorms and, thus, is a major sand and dust source area. Tazhong, a small mining village, is located near the center of the Taklimakan Desert at a distance of 220 km from the desert margins. Near Tazhong, we conducted a 2-year field investigation designed to monitor the diurnal variation of saltation activity using fast-responding piezoelectric saltation sensors (Sensits). Results suggest that saltation activity tends to occur more frequently during daytime in all seasons, relatively high levels of saltation activity are maintained from around 11:30 to around 16:30 local standard time (LST), because of stronger wind speed, higher soil temperature and lower relative humidity. During the spring and summer seasons, the saltation activity can occur at any time of the day, while there are some periods with zero saltation seconds at night and in the early morning during autumn and winter seasons. The results confirm that sandstorms tend to occur more frequently during daylight hours, so it may be helpful to forecast and guard against the occurrence of blowing sand or sandstorms in the Taklimakan Desert.     

Characteristics of dissolved organic nitrogen (DON) in the surface water of Beijing Olympic Forest Park

The characteristics of dissolved organic nitrogen (DON) in surface water from Beijing Olympic Forest Park (BOFP) were investigated in this study. Nanofiltration (NF) pretreatment procedure using two NF membranes (NF90 and NF270) was applied to increase the accuracy and precision of DON measurements in surface water samples with high dissolved inorganic nitrogen/total dissolved nitrogen (DIN/TDN) ratios. Compared to NF90, NF270 showed better performance in lowering the DIN/TDN ratio and retaining DOC in both the synthetic water and raw water samples. DON concentrations ranged from 0.01 to 0.83 mg N L^?1 in water samples collected over four different months and showed a seasonal variation. The DON increased in summer due to the higher activity of decomposers on recent litterfall or because of a higher production of biomass in the surface water body. The molecular weight (MW) fractions of <3 kDa accounted for more than 50 % of the total DOC concentration and the fractions of <3 kDa contributed to more than 48 % of the total DON concentration. It could be concluded that most of the DON present in surface water of BOFP was composed of small molecules, which were mainly composed of monomers such as amino acids and urea, readily available for the uptake by phytoplankton and heterotrophic bacteria.     

Status and challenges of water pollution problems in China: learning from the European experience

This paper provides a review of the water environment problems faced in China and a comparison with the European experience in dealing with such issues, with an attempt to emphasize the challenges in China. The paper also summarizes various studies in China to highlight the severity of water pollution problems faced by regulators, polluters and the general public. China’s water situation can be characterized by insufficient quantities of water, uneven distribution of water spatially and temporally, as well as poor water quality. Water pollution in China has spread from point source to non-point source, from fresh water to coastal water, and from surface water to groundwater. From the management and technological experience from EU, including water framework directive, water price system, desalination and groundwater recharge technologies, and from the analysis of water environment problems and management system in two regions, we could come to the conclusion that water price, water market and water tax could be introduced to China for water environment regulations. Moreover, it is necessary to establish a reliable risk assessment system for water quality, human health and ecological safety.     

The influences of land-use changes on the absorbed nitrogen and phosphorus loadings in the drainage basin of Lake Chaohu,China

The influences of land-use changes on the absorbed nitrogen and phosphorus loadings in the drainage basin of Lake Chaohu were investigated in this study. Based on the principle of universal soil loss equation, a model was developed for estimating the annual mean soil erosion amount from 1989 to 2008 in Chaohu basin. Applying the GIS and soil data, the absorbed nitrogen and phosphorus loadings were stimulated and quantified for three-time stage (1989–1995, 1996–2000, 2001–2008). Furthermore, the influences of historical land-use changes on the absorbed nitrogen and phosphorus loadings were assessed. The results indicated that the absorbed nitrogen and phosphorus loadings of drainage basin have an obvious spatial difference in the three-time stage because of the different characteristics of climate and geology. Temporally, the absorbed nitrogen and phosphorus loadings in the second stage (1996–2000) are less than the one in the first (1989–1995) and third stage (2001–2008), and the load of third stage is the largest, which was mainly impacted by rainfall and land-use change. Forest and grass can act as a source for the load of absorbed nitrogen or absorbed phosphorus. The paddy land and residential land in these areas act as sinks or transformation zones as expected. Other factors such as slope and geology also play important roles in the transport of nutrients and sediments to streams.     

中国海洋仪器设备研究发展的历史回顾

本文对中国海洋仪器设备研究发展历史的基本情况和主要成就进行了较全面的介绍。     

兰新铁路哈密地区的沙害

本文主要介绍了兰新铁路哈密地区沙害的分布特征、形成原因和防治措施。通过对1986年5月19-20日出现的12级东南大风后的沙害考察,指出平沙地、砂砾戈壁和砾质戈壁地段的铁路,由于线路两侧的地表性质,风沙流运动特征和地貌特征的不同,沙害的分布特征、危害程度、形成条件和防治措施也不同。总结了这次沙害的经验教训,提出了沙害防治以"因害设防、因地制宜,经济有效、长期可靠"为原则的-些具体措施。     

Simultaneous sources deblending via frequency-varying filter in cross-spread azimuth-offset domain

Simultaneous sources acquisition, also referred to as “blended acquisition”, involves recording two or more shots simultaneously. It allows for denser spatial sampling and can greatly speed up the field data acquisition. Thus, it has potential advantage to improve seismic data quality and reduce acquisition cost. In order to achieve the goal of blended acquisition, a deblending procedure is necessary. It attenuates the interference and thus improves the resolution of the pre-stack time migration image. In this paper, we propose an efficient deblending method, which applies frequency-varying median and mean filters to cross-spread azimuth-offset gathers (XSPR-AO). The method can be used with variable window sizes according to the characteristics of the interference. The effectiveness of the method is validated by a field data example.     

裂腹鱼类系统进化及高原适应性研究进展

裂腹鱼类是分布于青藏高原及其周边地区的一群鲤科鱼类,随着青藏高原的隆升由原始的鲃亚科鱼类逐渐演化为适应于寒冷、高海拔和急流等恶劣环境的一个自然类群,其共同特征是肛门和臀鳍基部两侧各有一列特化的鳞片(臀鳞),具有生长缓慢、性成熟晚、寿命较长、繁殖力低等生活史特征。裂腹鱼类是四倍体起源,多倍体化事件在其进化过程中发挥了重要的作用。裂腹鱼类特殊的地理分布、形态特征、遗传结构和生活史对策使其成为研究多倍体鱼类和高原适应机制的重要材料,并受到科学家们的广泛关注。本文综合分类学、系统发育与生物地理学、遗传学和生物学等领域,重点从考古学和系统学等多角度对裂腹鱼类的起源与进化进行论述,基于转录组学阐述裂腹鱼类高原适应的分子机制,较为全面地总结了高原多倍体鱼类的系统进化及极端环境适应。     

我国流域水生态监测与评价体系研究进展及发展对策

水生态监测与评价是水生态系统管理、保护和可持续利用的基础。20世纪80年代开始,欧美发达国家水环境管理政策开始强调生态保护,重视流域水生态质量,先后开展了以水生生物为核心的河流水生态监测与评价研究计划。然而我国目前流域水环境监测与评价的指标主要以传统的理化监测指标为主,缺乏指示水生态变化的水生生物指标,单一的水质改善无法反映水生态环境好转这一长远目标,不能满足“十四五”水生态环境管理由以水污染防治为主向水环境、水生态、水资源“三水”统筹转变的总体要求。本研究系统分析发达国家和地区(如美国、欧盟、澳大利亚等)水生态监测与评价技术体系与业务化运行方面的先进经验,总结梳理我国水生态监测与评价试点已有的工作基础,分析制约我国当前流域水生态监测与评价的关键问题,从保护目标、管理模式、监测网络、科学研究和公众参与五个方面,提出开展我国流域水生态监测与评价体系构建和业务化运行的有关建议,为准确评估和预测流域水生态质量状况的变化、开展保护修复成效评估提供决策支持和重要参考。