北极大气中典型持久性有机污染物对海冰变化的响应

近年来,北极变暖速度几乎是全球平均速度的两倍,海冰加速消融被认为会使沉积的持久性有机污染物（POPs）重新释放进入大气。本文利用近30年的大气POPs浓度数据和北极海冰数据,比较了有机氯农药（OCPs）和多氯联苯（PCBs）在北极Alert、Zeppelin、Stórhöfði和Pallas这4个站点的变率,结合互相关分析,探讨POPs对海冰变化的响应。结果发现,在周围多为浮冰区的Zeppelin站点,OCPs（特别是HCB和α-HCH）在2009年后与海冰变化显著负相关,而在其他站点显著性较低或无显著相关性。PCBs在Stórhöfði和Pallas站点,超前海冰变化,可能与长距离输送和土壤的二次释放有关,而在Zeppelin站点出现了和DDTs类似的滞后海冰变化的现象。本研究表明,不同类型的POPs对海冰变化的时空响应不同,海冰消融不一定导致大气POPs浓度增大。

     

Influence of a coarse interlayer on seawater intrusion and contaminant migration in coastal aquifers

Vertical 2D slice laboratory experiments were carried out in homogenous and layered sand tanks to elucidate the effects of a highly permeable (coarse‐grained sand) interlayer on seawater intrusion and transport of contaminants to a coastal sea. Tidal fluctuations produced oscillations in the seawater–freshwater transition zone, fluctuations of the contaminant infiltration rate and a zigzag contaminant plume outline. The seawater wedge became discontinuous at the (vertical) edges of the interlayer because of increased lateral movement of the seawater–freshwater interface within the interlayer. The contaminant plume formed a tail within the interlayer depending on the tidal stage, and similar to the wedge, its movement was accentuated. A simple analytical model that neglected vertical flow reliably predicted steady‐state seawater intrusion into the coastal aquifer. Numerical modeling was used to gain insight into the groundwater hydrodynamics and contaminant migration. The numerical results confirmed the experimental findings, i.e. that a highly permeable interlayer can provide a rapid transit path for contaminants to reach the seaward boundary and that the interlayer amplifies the effects of tidal fluctuations, resulting in wider transition zones for the seawater wedge and contaminant plume. Numerical simulations further showed that, with increasing interlayer hydraulic conductivity, the maximum seawater intrusion distance inside the interlayer increases approximately linearly. For the fixed‐head contaminant injection condition used, the model showed that contaminant infiltration increases approximately logarithmically with increasing interlayer hydraulic conductivity (other factors held fixed). Copyright © 2013 John Wiley & Sons, Ltd.     

基于五种油源的中重度风化溢油的常规鉴定指标的应用效果评估

本文利用采集于我国三大油田的五种原油样品开展了长达210天的溢油风化模拟实验,并依据相对偏差和重复性限数学分析法,进行溢油风化过程分析和诊断比值应用效果评估。研究结果表明:经过210天的风化,溢油鉴定诊断比值发生明显改变;其中来源于萜烷、甾烷和多环芳烃的诊断比值变化率要远低于正构烷烃,可用于中长期风化溢油鉴定。此外,研究发现,在这些有效诊断比值中有4个变化率较小,相对偏差低于5%,保持了较好的稳定性,更适合于重度风化溢油鉴定。     

Missing the boat: Critical threats to coral reefs are neglected at global scale

Coral reefs have experienced a global decline due to overfishing, pollution, and warming oceans that are becoming increasingly acidic. To help halt and reverse this decline, interventions should be aimed at those threats reef experts and managers identify as most severe. The survey included responses from 170 managers, representing organizations from 50 countries and territories, and found that respondents generally agreed on the two major threats: overfishing and coastal development. However, resource allocation did not match this consensus on major threats. In particular, while overfishing receives much attention, coastal development and its attendant pollution are largely neglected and underfunded. These results call for a re-examination of how resources are allocated in coral reef conservation, with more attention given to aligning how money is spent with what are perceived to be the primary threats.     

Opportunistic natural experiments using digital telemetry: a transit disruption case study

ABSTRACT

In the past decade society has entered a technological period characterized by handheld computing that supports input and processing from numerous sensors. Today’s mobile phones offer the ability to integrate input from sensors monitoring various external and internal sources (e.g., accelerometer, magnetometer, microphone, GPS, wireless Internet, and Bluetooth). Furthermore, these raw inputs can be integrated and processed in ways that can offer novel representations of human behaviour. As a result, new opportunities to examine and better understand human spatial behaviour are available; one such application is the constant monitoring of a group of people over an extended period of time. Such a research setting lends itself to natural experiments that emerge as a result of regular and on-going observations. We report here on the observation of a natural experiment that took place in the context of a month-long monitoring study of 28 participants using mobile phone-based ubiquitous sensor monitoring. The implications for public health and transportation planning are discussed.     

Laboratory Study for Influence of Clay Content (CC) on Wave-Induced Liquefaction in Marine Sediments

In this artice, the influence of clay content on the wave-induced liquefaction in marine sediments was reported. The one-dimensional (1-D) equipment was setup with a vertical cylinder and 1.8–m–thick clayey sandy deposit and 0.2–m–thick water above the deposit. Unlike the previous experimental study for a single soil layer, this study used sand-kaolin mixtures, sand-illite mixtures, and sand-bentonite mixtures as the experimental samples. A series of experiments with 3,000 wave cycles in each test were conducted under numerous wave and soil conditions, which allowed us to examine the influence of clay content (CC) on wave-induced liquefaction in marine sediments. The experimental results showed that the clayey sandy deposit will become prone to liquefaction with the increase of CC when CC is less than a critical value, which depends on the type of clay. However, when CC is greater than the critical value, liquefaction depth will decrease as CC increases. Furthermore, when the CC value reaches a certain level, liquefaction will not occur. For example, no liquefaction occurs when CC ≥ 33% for both kaolin-sand and illite-sand mixtures and CC ≥ 16.36% for bentonite-sand mixtures.     

Comparative Study of Hydrogen and Carbon Isotopic Composition of Gases Generated from the Pyrolysis of a Peat under Saltwater and Freshwater Conditions

To understand the influence of the diagenetic water medium on the isotopic compositions of thermogenic coalbed gas, both hydrous and anhydrous closed-system pyrolyses were performed at temperatures of 250°C to 650°C on an herbaceous marsh peat. Compared to the results of anhydrous pyrolysis, the hydrocarbon gases generated from hydrous pyrolyses have very different hydrogen isotopic compositions. However, the carbon isotopic compositions of the hydrocarbon gases became only slightly heavier in hydrous pyrolysis, compared to that from anhydrous pyrolysis. With the progress of thermal evolution from peat to a more advanced thermal maturity of vitrinite reflectance values (Ro) of 5.5% during the pyrolysis, the difference in the average δD value increased from 52‰ to 64‰ between the hydrous pyrolysis with saltwater and anhydrous pyrolysis and increased from 18‰ to 29‰ between the hydrous pyrolysis with freshwater and anhydrous pyrolysis, respectively. The difference in the average δ13C value was only 1‰–2‰ between the hydrous and anhydrous pyrolysis. The relationships between the δD values of the generated hydrocarbon gases and Ro values as well as among δD values of the hydrocarbon gas species are established. The close relationships among these parameters suggest that the water medium had a significant effect on the hydrogen isotopic composition and a minimal effect on the carbon isotopic composition of the hydrocarbon gases. The results of these pyrolyses may provide information for the understanding of the genesis of coalbed gas from herbaceous marsh material with the participation of different diagenetic water media.     

四川盆地云和降水观测科学试验设计与实践

2014—2017年四川地区开展了大范围云系观测科学试验。观测对象以盆地层状云系和积层混合云系为主,积状云(对流云)为辅。本文围绕试验目标、区域、观测要素、观测布局设计、观测方案设计、设备技术参数和典型个例等7个方面进行介绍,根据不同类型云系和降水变化特征,设计有针对性的观测方案,获得了不同类型云系和降水的多尺度连续性观测数据,为四川地区开展云和降水关系研究提供详实的综合型外场观测数据。层状降水云典型个例云高可达8km,云强核心部位的云雷达反射率可达28dBz,径向速度可达-6m·s~(-1),在0℃附近,反射率和退偏振因子LDR上有一条明显的亮带,表现为极大值,液态水主要集中于4.5km以下,随着雨强增大,液水含量增加,降水滴谱分布较窄,随着雨强减小,雨滴谱和速度谱变窄,但小粒径数浓度增加,说明对层状云雨强起主导作用的是雨滴直径,而不是数浓度;无降水层状云典型个例云层厚度为3.2km,云顶约为4km,云雷达反射率不超过0dBz,径向速度不超过5m·s~(-1),层状云内整层水汽含量和液水含量较为稳定,云中主要为液态粒子且粒径偏小、小粒径数浓度较高。     

Multi-year Simulations and Experimental Seasonal Predictions for Rainy Seasons in China by Using a Nested Regional Climate Model (RegCM_NCC). Part Ⅰ: Sensitivity Study

A modified version of the NCAR/RegCM2 has been developed at the National Climate Center (NCC), China Meteorological Administration, through a series of sensitivity experiments and multi-year simulations and hindcasts, with a special emphasis on the adequate choice of physical parameterization schemes suitable for the East Asian monsoon climate. This regional climate model is nested with the NCC/IAP (Institute of Atmospheric Physics) T63 coupled GCM to make an experimental seasonal prediction for China and East Asia. The four-year (2001 to 2004) prediction results are encouraging. This paper is the first part of a two-part paper, and it mainly describes the sensitivity study of the physical process parameterization represented in the model. The systematic errors produced by the different physical parameterization schemes such as the land surface processes, convective precipitation, cloud-radiation transfer process, boundary layer process and large-scale terrain features have been identified based on multi-year and extreme flooding event simulations. A number of comparative experiments has shown that the mass flux scheme (MFS) and Betts-Miller scheme (BM) for convective precipitation, the LPMI (land surface process model I) and LPMII (land surface process model Ⅱ) for the land surface process, the CCM3 radiation transfer scheme for cloud-radiation transfer processes, the TKE (turbulent kinetic energy) scheme for the boundary layer processes and the topography treatment schemes for the Tibetan Plateau are suitable for simulations and prediction of the East Asia monsoon climate in rainy seasons. Based on the above sensitivity study, a modified version of the RegCM2 (RegCM_NCC) has been set up for climate simulations and seasonal predictions.