中国水稻土有机和无机碳的空间分布特征

农业土壤碳库对陆地生态系统碳循环的研究具有重要意义。水稻土是中国主要的耕作土壤,在土壤碳固定研究中具有现实意义。文章根据最近建成的中国1∶100万数字化土壤图和全国1490个水稻土剖面数据,估算我国水稻土碳密度和储量,并进一步分亚类和区域研究了水稻土碳库的分布特征。结果表明,中国水稻土面积为45.69×104km2,占我国土壤总面积的4.92%。中国水稻土无机碳的分布面积为5.93×104km2,仅占水稻土总面积的13%。水稻土碳密度具有高度的空间变异性,水稻土剖面0~100cm有机碳密度介于0.53kg·m-2~446.2kg·m-2之间,无机碳密度介于0.05kg·m-2~90.03kg·m-2。水稻土表层0~20cm有机碳密度介于0.17kg·m-2~55.38kg·m-2之间,无机碳密度介于0.01kg·m-2~21.85kg·m-2。中国水稻土剖面0~100cm和表层0~20cm碳总储量分别为5.39Pg和1.79Pg。水稻土碳储量以有机碳为主,约占水稻土碳总储量的95%,水稻土剖面0~100cm和表层0~20cm有机碳储量分别为5.09Pg和1.72Pg。水稻土无机碳储量较低,仅占水稻土碳总储量的5%左右,水稻土剖面0~100cm和表层0~20cm无机碳储量分别为0.30Pg和0.07Pg。     

现行脱硫技术存在排放温室气体的隐患

工业革命以来,由于人类活动持续大量排放温室气体,使得全球出现了持续性的气候变暖趋势,而为了治理局部的和区域的SO2污染问题,大规模的脱硫活动在我国急速增加,这势必大幅增加CO2的排放,加剧气候变暖的进程,如果我国大型火电厂的脱硫率达到80%,按照2005年全国SO2排放量已经达到0.2549Gt计算,采用现行脱硫方法将每年向大气中排放0.088Gt的CO2。将占我国CO2年排放量的10%,对人类赖以生存的地球形成严重威胁。因而,需要研究脱硫的无碳工艺,以及碳捕集、碳储存、碳利用技术,树立综合的环境意识,在控制大气污染、减排温室气体与保护臭氧层方面寻找结合点。     

地衣样品的采集和保存技术的研究

本文阐述了地衣样品的规范的采集;无污染的采样工具、运输工具、盛装容器及加工器械是保存技术的先行条件。全程序的质控是保存技术的基础,温度、压力、光则是保存技术决定性的因素。通过三种保存技术的研究筛选出了既经济又简便的保存技术     

全玻璃针筒注射器保存空气中甲烷和总烃的影响因素

采用全玻璃针筒取样/保存、双通道双毛细管柱测定非甲烷总烃分析方法,以甲烷标准气体样品、标准气体样品(TO-14、TO-15),以及3种实际环境空气样品为例,考察了全玻璃针筒注射器取样保存影响检测结果的若干因素。结果表明,样品的保存时间取决于以下因素:(1)样品性质,不同类型样品的保存时间差异大,化学反应活性强的样品,其总烃含量呈现先升高后降低趋势,甲烷则相对稳定;(2)样品浓度水平,相同条件下相同类型样品,浓度高的保存时间短于低浓度样品,如与环境空气浓度相仿的样品保存时间可超过60 h;(3)保存环境的避光程度,对于同一种VOCs标准气体样品,避光、半避光、非避光保存样品回收率迥异,趋势差别极大,对于部分样品即便是避光保存仍发现回收率变化极大;(4)全玻璃材质注射器的气密性,需对照技术规范要求,进行气密性的检查。     

基于VR技术的大型储罐火灾爆炸仿真软件设计

为了研究大型储罐事故后果的严重性，针对大型储罐火灾爆炸试验难以实施的情况，以虚拟现实技术为研究手段，重现大型储罐火灾和爆炸事故过程；通过对储罐火灾和爆炸事故进行理论分析，优选出大型储罐火灾爆炸事故后果数学模型；基于某商业原油储备库布置，利用3Ds Max软件对库区进行建模，结合Qt界面编写技术和OSG粒子效果技术进行交互式设计，划分火灾和爆炸2大仿真模块，设计各模块下属基本功能，形成1套基于真实场景的大型储罐火灾爆炸事故后果三维仿真模拟软件。研究结果表明:基于VR技术的大型储罐火灾爆炸仿真软件具有较强的沉浸感和交互性等特点，能够实时仿真大型储罐火灾爆炸事故动态演变过程，降低大型储罐火灾爆炸试验成本，同时为制定事故应急预案和应急处置措施提供科学参考。     

National contributions to global ecosystem values

Current conservation templates prioritize biogeographic regions with high intensity ecosystem values, such as exceptional species richness or threat. Intensity-based targets are an important consideration in global efforts, but they do not capture all available opportunities to conserve ecosystem values, including those that accrue in low intensity over large areas. We assess six globally-significant ecosystem values—intact wilderness, freshwater availability, productive marine environments, breeding habitat for migratory wildlife, soil carbon storage, and latitudinal potential for range shift in the face of climate change—to highlight opportunities for high-impact broadly-distributed contributions to global conservation. Nations can serve as a cohesive block of policy that can profoundly influence conservation outcomes. Contributions to global ecosystem values that exceed what is predicted by a nation's area alone, can give rise to countries with the capacity to act as ‘conservation superpowers’, such as Canada and Russia. For these conservation superpowers, a relatively small number of national policies can have environmental repercussions for the rest of the world.     

Recent Ogallala Aquifer Region Drought Conditions as Observed by Terrestrial Water Storage Anomalies from GRACE

Recent severe drought events have occurred over the Ogallala Aquifer region (OAR) during the period 2011–2015, creating significant impacts on water resources and their use in regional environmental and economic systems. The changes in terrestrial water storage (TWS), as indicated by the Gravity Recovery and Climate Experiment (GRACE), reveals a detailed picture of the temporal and spatial evolution of drought events. The observations by GRACE indicate the worst drought conditions occurred in September 2012, with an average TWS deficit of ~8 cm in the northern OAR and ~11 cm in the southern OAR, consistent with precipitation data from the Global Precipitation Climatology Project. Comparing changes in TWS with precipitation shows the TWS changes can be predominantly attributable to variations in precipitation. Power spectrum and squared wavelet coherence analysis indicate a significant correlation between TWS change and the El Nino‐Southern Oscillation, and the influence of equatorial Pacific sea surface temperatures on TWS change is much stronger in the southern OAR than the northern OAR. The results of this study illustrate the value of GRACE in not just the diagnosis of significant drought events, but also in possibly improving the predictive power of remote signals that are impacted by nonregional climatic events (El Nino), ultimately leading to improved water resource management applications on a regional scale. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

How important are uncertainty and dynamics for environmental and climate policy? Some analytics

We introduce ten papers on sustainable resource dynamics. In addition, we provide analytical results on the effect of stochastic damages on optimal economic growth, the effects of habits and loss aversion on the cost-benefit discount rate, and the effect of a carbon budget and carbon capture and storage (CCS) on optimal investment in technical change.     

A coordinated control strategy using supercapacitor energy storage and series dynamic resistor for enhancement of fault ride-through of doubly fed induction generator

Power fluctuation and fault-related complication are the two major issues for doubly fed induction generator (DFIG)-based wind energy conversion system (WECS). The occurrence of fault leads to the rotor over current, stator over current, and DC-link overvoltage as well. These uncertainties may damage the rotor circuit, converter circuit and force the disconnection of wind system from the grid. To get rid of these issues, a supercapacitor energy storage element along with a passive series dynamic resistor (SDR) is suggested in this paper. Supercapacitor energy storage system (SCESS) is located across the DC-link, which able to handle the power fluctuation and the SDR is placed in rotor circuit, which will reduce the overcurrent possibility. Simulation is carried for a DFIG-based WECS for three phase to ground fault and two phase to ground fault. During symmetrical fault as well as asymmetrical fault, various operational disorders appeared such as rotor overcurrent, stator overcurrent and DC-Link overvoltage are found to be within their permissible limits. The results reveal the effectiveness of the proposed strategy over the conventional vector control scheme and SCESS as well.     

Experimental energy and exergy analyses of a discharging heat exchanger for a small hot-oil domestic storage tank

Experiments are described to investigate the thermal performance of a discharging heat exchanger for a small storage tank filled with oil. Experimental results are presented in terms of the discharging energy rates (power) and the discharging exergy rates for low (~4 ml/s) and high discharging flow rates (~8 ml/s). Water heating energy rates, which are respectively maximized at approximately 600 W and 1200 W at low and high flow-rate discharging, are found to be higher than the discharging energy rates, which are respectively maximized at 450 W and 900 W. These results indicate that the energy rates do not accurately evaluate the thermal performance of the discharging heat exchanger since the energy heating rate of the water is greater than that for the oil that heats it, which is thermodynamically inconsistent. The energy rates should thus be used with caution when the thermal performance of the heat exchanger is evaluated. Water heating exergy rates, which are respectively maximized at approximately 45 W and 130 W at low and high flow-rate discharging, are generally smaller than the discharging exergy rates, which are respectively maximized at 65 W and 170 W. Exergy rate results are thus more consistent in the physical process of water heating, and an exergy factor is suggested as a proper measure for evaluating the performance of the discharging heat exchanger. The maximum value of the exergy factor is found to increase from 0.15 at low flow rates to a maximum value of approximately 0.19 at high flow rates. This implies that to extract more energy from a storage tank to a discharging heat exchanger, the flow rate has to be high, which is consistent with the physical process of heating water faster to higher temperatures. The exergy factor can thus be used as a design parameter for discharging heat exchangers.