黄河河川基流量演化规律及其驱动因子探讨

河川基流量是指地下水补给河川径流的水量。论文首次对黄河河川基流量50年来的时空演化规律和驱动因子做了较为全面的分析。研究表明:黄河河川基流量约占黄河河川径流量的44%,黄河河川基流量对维持健康黄河具有重要意义。受自然变化和人类活动影响,黄河干支流河川基流量50年来总体呈下降趋势;支流基流量变化可划分为双峰型、单峰型、直线下降型3种类型,干流区间基流量主要减少在黄河中游地区。黄河河川基流量具有维持河川径流、维护河流生态、湖泊以及表生生态植被良性发展等多种功能,河川基流量衰减导致湖泊萎缩、表生植被退化、加剧黄河断流等一系列生态环境负效应。通过对驱动因子进一步分析表明,降水量是维持河川基流量的主要来源,其变化影响黄河河川基流量变化趋势。人类活动是黄河河川基流量驱动因子中最活跃的因子,基流量衰减最明显的地区也是人类活动频繁的地区。因此维持健康的黄河必须要对黄河基流量进行科学保护和合理开发利用。     

Simulated potential effects of ecological factors on a hypothetical population of Chiricahua leopard frog (Rana chiricahuensis)

Simulations provide an opportunity to examine how single or multiple perturbations may impact a specific species. The objectives of this study were to identify thresholds at which changes in stream peak flow, stream base flow, and/or chytrid fungus presence alter long-term Rana chiricahuensis populations. We used scenarios with varying peak flow mortality rates, base flow mortality rates, and chytrid fungus mortality rates. Sensitivity analysis was also conducted. Over 50 years, populations in six scenarios increased and 13 scenarios decreased. Eight scenarios resulting with fewer than 100 individuals included stochastic effects for at least two of three perturbations and the remaining scenarios included chronic effects of 30% or higher. Scenarios with population increases had either no chytrid fungus effect or chronic effects from perturbations totaling less than 30%. In the absence of chytrid fungus, populations increased and became stable. At a 10% annual death rate caused by chytrid fungus, the R. chiricahuensis population decreased 46.8%. At a 20% death rate, the population decreased 98.6%. Model scenarios were sensitive to peak flow death rates. As peak flow mortality increased to 10 and 20%, extinction rates increased to 91.7 and 99.9%, respectively. With model parameters and the no base flow mortality, R. chiricahuensis populations declined by 92% with a 3.2% extinction rate at 50 years. Models with base flow mortality rates of 10 and 20% resulted in population extinction rates of 48.7 and 96.1%, respectively. Scenario analysis of perturbations on a hypothetical R. chiricahuensis population provided a framework in which to view combined effects on a species. Analysis supports supposition that chytrid fungus is the proximate cause of many amphibian declines, but the added effect of base flow and peak flow has the potential to hasten declines.     

东北商品粮基地粮食生产的区域分异

论文以商品粮基地县为研究单元,运用数理统计和GIS空间分析结合的方法,揭示东北商品粮基地县粮食总产的区域差异。研究结果表明:①粮食总产低于平均水平的商品粮基地县占多数,高于平均水平的基地数量仅占36.36%,但粮食产量占全部基地县粮食总产量的64.74%;②粮食生产基本上形成了以玉米、大豆、水稻为主的生产能力格局,粮食总产的区域差异小于分品种粮食作物内部的区域差异;③从省域尺度看,粮食总产高于平均水平的基地县84.6%分布在黑龙江和吉林两省,粮食生产布局的区域化、专业化趋势明显,大宗粮食作物进一步向产粮大县集中;④从区域尺度看,粮食总产的空间格局高低交错,集中在以松嫩平原中部黑土区、辽河平原和三江平原为重心的平原地区,有由中部平原地区向周边递减的趋势。回归分析表明,播种面积的区域差异是导致商品粮基地县粮食总产区域分异的主要原因,农业现代化水平对其具有重要影响。应加强商品粮基地建设,加大中低产田的改造力度,走以提高粮食单产来提高粮食综合生产能力的内涵式发展道路。     

Towards a framework for assessment and management of cumulative human impacts on marine food webs

Effective ecosystem‐based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions.     

浅谈通讯基站电磁辐射环境影响理论预测模式

介绍了通讯基站电磁辐射环境影响评价的重要胜,在介绍电磁辐射环境标准限值的基础上,针对现有环境影响理论预测与实际监测值存在误差的情况,分析了通讯基站电磁辐射的影响因素和误差存在的原因,并对采取的理论预测模型提出优化建议,使预测结果更接近于实际值,为通讯基站电磁辐射环境影响预测及评价提供更加科学、合理的依据。     

我国自然生态系统氮沉降临界负荷评估

过量的氮沉降引起了一系列环境问题并导致生物多样性损失,因此评估当前生态系统氮沉降临界负荷对区域氮管理及其污染控制至关重要.利用稳态质量平衡法估算了当前我国自然生态系统的氮沉降临界负荷,并与氮沉降数据对比,获取了我国超过氮沉降临界负荷的生态系统空间分布情况.结果表明,6%的地区氮沉降临界负荷大于56 kg·(hm²·a)^-1,67%的地区氮沉降临界负荷在14～56 kg·(hm²·a)^-1之间,27%的地区氮沉降临界负荷小于14 kg·(hm²·a)^-1.氮沉降临界负荷较高的区域主要分布在青藏高原东部、内蒙古东北部和南部部分地区.氮沉降临界负荷较低的区域主要分布在青藏高原西部、西北地区和东南部分地区.氮沉降超过临界负荷的区域约占我国的21%,主要分布在东南和东北部分地区.东北、西北和青藏高原地区超临界负荷值普遍低于14 kg·(hm²·a)^-1.因此,未来这些超过氮沉降临界负荷地区的氮素管理和控制更为值得关注.     

季铵型树脂的合成及其对水中溴酸根及前驱物溴离子的吸附性能与机制

水中的溴离子(Br^-)和溴酸根离子(BrO₃^-)由于难挥发、易溶解、稳定性好而难以除去,因此,制备了一种对较低浓度的Br^-和BrO₃^-都有良好吸附去除效果的季铵碱树脂(Quaternary ammonium base resin,QABR)并表征了其物化结构.同时,考察了初始浓度、QABR投加量、溶液pH、离子强度、吸附接触时间和吸附温度等因素对QABR吸附Br^-和BrO₃^-性能的影响.结果表明,在0.05～4.00 mmol·L^-1浓度范围内,在298 K、pH=7.0时QABR对Br^-和BrO₃^-的吸附能力最佳,其最大吸附量分别为1.78 mmol·g^-1和1.65 mmol·g^-1;QABR对Br^-和BrO₃     

GSM移动通信基站对周围环境电磁辐射影响

按照《辐射环境保护管理导则—电磁辐射环境影响评价方法与标准》（HJ/T10.3—1996）的有关规定,GSM移动通信基站电场强度的管理目标值为5.4 V/m,功率密度的管理目标值为8μW/cm2。在根据麦克斯韦电磁场理论确定远场区范围,结合基站天线运行的基本参数,以及在对垂直波瓣图进行拟合的基础上,通过《辐射环境保护管理导则——电磁辐射监测仪器和方法》（HJ/T 10.2-1996）中的微波远场轴向功率密度计算公式计算GSM移动通信基站对周围环境的辐射水平进行预测。预测结果表明,基站周围的电磁辐射水平与天线的发射功率、公众活动区域与天线的高度差以及天线的主瓣方向关系密切。实际应用中可以通过减小发射功率,增加天线与公众活动区域的高度差以及调整天线的主瓣方向等措施来降低其对周围环境的影响,并通过制定有效的监测、管理计划和加强公众沟通,及时消除可能的电磁污染。     

REGIONAL APPLICATION OF AN APPROXIMATE STREAMFLOW PARTITIONING METHOD1

ABSTRACT: The approximate streamflow partitioning method which uses daily rainfall and streamfiow data was applied in Coastal Plain, Coastal Flatwoods, and Southern Piedmont physiographic regions for estimation of the surface and subsurface flow components of total streainflow. Sizes of the watersheds ranged from 9.6 km² to 1,030 km. Although the streamflow partitioning method was developed and tested on the Coastal Plain physiographic region, results indicate that the procedure can be applied to other physiographic regions where available data are limited to daily values. The effect of channelization on the partitioned flow components in the Coastal Plain and Coastal Flatwoods physiographic areas was also examined. While channelization was found to decrease the storm-time base, it had no significant effect on the relative percentages of the partitioned flow components.     

盘锦市有机食品基地水质状况分析

通过对盘锦市有机食品基地进行监测，结果表明：水稻全生长期灌溉水质均符合标准，以氟化物、硫酸盐、氯化物为首要污染物，稻田水质好于上水线水质，成熟期水质好于其它生长期。