有关1556年关中大地震几个问题的探讨

本文讨论了1556年关中大地震震中位置、震级和人口伤亡等几个问题。认为震中应在潼关、蒲州之间,震级高于8级,人口伤亡数字无夸大的可能。     

三江平原小叶章湿地生态系统对氮磷的净化效率

选取面积为1 600 m2的小叶章(Deyeuxia angustifolia)湿地进行小区域模拟试验。试验设割草区、1倍浓度区、静态对照区和2倍浓度区4个处理,研究N、P输入浓度,割草和输出径流对三江平原小叶章湿地生态系统净化N、P污染物的影响。结果表明,在小叶章生长期和成熟期,湿地生态系统对N、P保持较稳定的净化,N、P平均去除率分别为85.62%和85.94%。湿地水体中TN和NH4 -N的累积浓度显著相关。输入浓度、割草和输出径流都影响着湿地生态系统对N、P的净化和N、P在系统内的分配。输入浓度增大时,N、P去除率明显降低;割草会降低N去除率,但对P去除率影响不大;少量输出径流对N、P去除影响不大。三江平原小叶章湿地生态系统对输入的N、P具有显著净化作用,总净化率可达97.97%和99.05%。     

中国中部农区乡村重构特征及其地域模式——以江汉平原为例

以人地关系理论为基础,以乡村地域系统内部要素变化解析乡村重构特征、外部环境变化解读乡村重构机理、外源驱动因素与内生响应要素耦合解译乡村重构模式。基于江汉平原的实证研究表明：（1）研究期内乡村地域持续经历重构过程,表现为乡村重构综合指数不断增加,高值区主要沿域内交通干线分布、低值区主要分布长江沿线和平原腹地;（2）乡村重构机制主要表现为工业化、城镇化、市场化等外源驱动因素与经济、社会、空间等内生要素的耦合作用,非农产业规模扩张引发乡村人口外迁和就业转移,进而推动人口、土地和产业等乡村“存量”要素重组;（3）经济—社会重构主导是江汉平原乡村重构的主流模式,产业结构和生产方式变化加剧乡村生态环境和人居环境恶化,乡村振兴及其可持续发展面临水环境污染和水灾害侵袭的双重挑战。研究框架能够揭示江汉平原乡村地理剧变特征,中国中部农产品主产区的乡村重构具有与发达地区不尽相同的图景。研究结果意在为乡村地理研究和乡村振兴实践提供有益启示。     

基于潜在分类模型的湿地生态系统服务公众生态偏好异质性研究

在生态系统服务价值评估研究中,把握公众的生态偏好是当前研究的重要内容。论文以三江平原湿地为研究对象,应用选择实验法获取公众的生态偏好和支付意愿,构建潜在分类模型,探究公众对湿地各项生态系统服务的偏好异质性。研究结果显示：公众对各项湿地生态系统服务存在显著的偏好异质性,资源偏好型的受访者所占比例最大（68.78%）,景观偏好型的受访者对自然景观的支付意愿显著较高,而价格敏感型受访者的支付意愿明显低于其他两类。分析各潜在类别可知,公众的社会经济特征及环境意识对其偏好具有显著影响。教育水平越高的受访者越偏好于资源保护,高收入和到景区旅游次数多的受访者更偏好于景观保护,而价格敏感型受访者的环境意识相对较低。研究不仅为湿地生态系统服务偏好异质性的研究提供新途径,也为相关环境政策的制定提供参考。     

Understanding unusually high levels of peroxyacetyl nitrate (PAN) in winter in Urban Jinan, China

Peroxyacetyl nitrate(PAN), as a major secondary pollutant, has gained increasing worldwide attentions, but relevant studies in China are still quite limited. During winter of 2015 to summer of 2016, the ambient levels of PAN were measured continuously by an automatic gas chromatograph equipped with an electron capture detector(GC–ECD) analyzer at an urban site in Jinan(China), with related parameters including concentrations of O3, NO, NO_2, PM_(2.5), HONO,the photolysis rate constant of NO_2 and meteorological factors observed concurrently. The mean and maximum values of PAN concentration were(1.89 ± 1.42) and 9.61 ppbv respectively in winter, and(2.54 ± 1.44) and 13.47 ppbv respectively in summer. Unusually high levels of PAN were observed during severe haze episodes in winter, and the formation mechanisms of them were emphatically discussed. Study showed that high levels of PAN in winter were mainly caused by local accumulation and strong photochemical reactions during haze episodes, while mass transport played only a minor role. Accelerated photochemical reactions(compared to winter days without haze) during haze episodes were deduced by the higher concentrations but shorter lifetimes of PAN, which was further supported by the sufficient solar radiation in the photolysis band along with the high concentrations of precursors(NO_2, VOCs) and HONO during haze episodes. In addition, significant PAN accumulation during calm weather of haze episodes was verified by meteorological data.     

江汉平原石家河谭家岭遗址新石器时代环境考古

通过对位于江汉平原北部石家河古城内谭家岭遗址地层孢粉、碳氮地球化学和磁化率代用指标的综合分析表明,石家河文化早期(4.6—4.4 ka BP),孢粉浓度较高且种类多,特别是喜暖湿的孢粉科属含量较大,植被覆盖较好,说明遗址及周边地区受人类活动干扰较少;TOC、TN和C/N偏高,δ~(13)C_(org)偏低,表明当时以C_3植物为主,气候较为温暖湿润;该时期遗址区域可能积水较多,磁化率值总体较低,发生过水域面积增大但持续时间不长的变化,石家河古城在防御洪水及外敌入侵方面发挥了较大作用。石家河文化中晚期(4.4—4.0 ka BP),孢粉种类和浓度减小,TOC、TN和C/N也持续减小,δ~(13)C_(org)则偏高,气候凉干,降水减少,遗址区域积水减少并逐渐演变成古人的居住用地,受人类活动影响磁化率值明显增高;由于河湖、地下水位下降,石家河古城防御洪水与外侵的功能消失并逐渐废弃。4.2 ka BP前后气候持续凉干,极端灾害事件频繁发生,影响了当地农业和渔猎业的发展,使得石家河文化发展停滞,这是导致本区石家河文化衰落的重要环境因素。     

Field scale interaction and nutrient exchange between surface water and shallow groundwater in the Baiyang Lake region, North China Plain

Fertilizer input for agricultural food production, as well as domestic and industrial surface water pollutants in the North China Plain, increases pressures on locally scarce and vulnerable water resources. In order to: (a) understand pollutant exchange between surface water and groundwater, (b) quantify nutrient loadings, and (c) identify major nutrient removal pathways by using qualitative and quantitative methods, including the geochemical model PHREEQC, a one-year study at a wheat (Triticum aestivum L.) and maize (Zea mays L.) double cropping system in the Baiyang Lake area in Hebei Province, China, was undertaken. The study showed a high influence of low-quality surface water on the shallow aquifer. Major inflowing pollutants into the aquifer were ammonium and nitrate via inflow from the adjacent Fu River (up to 29.8 mg/L NH₄-N and 6.8 mg/L NO₃-N), as well as nitrate via vertical transport from the field surface (up to 134.8 mg/L NO₃-N in soil water). Results from a conceptual model show an excess nitrogen input of about 320 kg/ha/a. Nevertheless, both nitrogen species were only detected at low concentrations in shallow groundwater, averaging at 3.6 mg/L NH₄-N and 1.8 mg/L NO₃-N. Measurement results supported by PHREEQC-modeling indicated cation exchange, denitrification, and anaerobic ammonium oxidation coupled with partial denitrification as major nitrogen removal pathways. Despite this current removal capacity, the excessive nitrogen fertilization may pose a future threat to groundwater quality. Surface water quality improvements are therefore recommended in conjunction with simultaneous monitoring of nitrate in the aquifer, and reduced agricultural N-inputs should be considered.     

APPLICATION OF A MULTIPURPOSE UNEQUAL PROBABILITY STREAM SURVEY IN THE MID‐ATLANTIC COASTAL PLAIN1

ABSTRACT: A stratified, spatially balanced sample with unequal probability selection was used to design a multipurpose survey of headwater streams in the Mid‐Atlantic Coastal Plain. Objectives for the survey include unbiased estimates of regional stream conditions, and adequate coverage of unusual but significant environmental settings to support empirical modeling of the factors affecting those conditions. The design and field application of the survey are discussed in light of these multiple objectives. A probability (random) sample of 175 first‐order nontidal streams was selected for synoptic sampling of water chemistry and benthic and riparian ecology during late winter and spring 2000. Twenty‐five streams were selected within each of seven hydrogeologic subre‐gions (strata) that were delineated on the basis of physiography and surficial geology. In each subregion, unequal inclusion probabilities were used to provide an approximately even distribution of streams along a gradient of forested to developed (agricultural or urban) land in the contributing watershed. Alternate streams were also selected. Alternates were included in groups of five in each subregion when field reconnaissance demonstrated that primary streams were inaccessible or otherwise unusable. Despite the rejection and replacement of a considerable number of primary streams during reconnaissance (up to 40 percent in one subregion), the desired land use distribution was maintained within each hydrogeologic subregion without sacrificing the probabilistic design.     

不同开垦年限湿地土壤铁变化特征研究

以三江平原不同开垦年限的湿地土壤为对象,研究了土壤全铁含量、氧化铁游离度、活化度和络合度的时空变化趋势.结果表明,耕层(0～20 cm)土壤较中下层(20～100 cm)土壤、开垦初期(0～1a)较开垦后期(1～25 a)铁所受影响更为显著.土壤全铁与有机质呈极显著负相关,相关系数为-0.620,而与全磷和pH值的相关程度较低.土层1(0～10 cm)全铁含量于开垦前7 a快速增长,13 a后趋于平稳;而土层2(10～20 cm)的快速增长期为8 a,15 a后进入平稳期.土层1比土层2的响应时间更短,规律性更强.土壤氧化铁的游离度在开垦之后迅速升高,而后降低再升高.活化度和络合度随开垦年限的增加都呈指数衰减趋势,其中土层1的活化度在开垦前4 a迅速降低,6 a后趋于平稳,土层2的活化度则在开垦1 a内迅速降低而后一直保持平稳;而络合度的上述年限分别为6 a、14 a和2 a.土壤中全铁的相对含量、氧化铁的活化度和络合度的拟合方程都可反推出土壤的开垦年限,可见铁对土壤环境变迁具有一定的指示作用.     

湖南澧阳平原黑褐色土的稀土元素地球化学特征及其环境意义

通过对澧阳平原大量的野外考察、典型剖面玉成(YC)黑褐色土壤剖面的系统取样和室内粒度、稀土元素地球化学分析,以及OSL和AMS14C年代测定,探讨了黑褐色土的稀土地球化学特征,揭示了黑褐色土的形成年代、形成过程与形成环境.研究结果表明,黑褐色土层XREE变化范围分布在184.63-264.261μg·g-1,其平均值为207.93μg·g-1;低于剖面的∑REE总平均值219.87Pμg·g-1,与洞庭盆地的红土∑REE平均值(211.6μg·g-1)大体相当,但明显高于镇江下蜀黄土(207.7μg·g-1)和黄土高原黄土(159.2μg·g-1),表明YC剖面黑褐色土上经过了相对较强的风化成壤作用.YC剖面黑褐色土的稀土分布模式与该剖面黄土层、黄土高原黄土、镇江下蜀黄土和洞庭盆地风成红土等典型风成沉积物的分布模式具有一致性,而与河流沉积物、湖泊沉积物和基岩风化红土在稀土的分布模式上具有明显差别.而且,YC剖面沉积物粒度频率曲线呈明显的单峰分布,与典型河流相的双峰粒度频率分布存在显著差异;YC剖面位于澧阳平原中部台地上,比周边高5-10m,不可能是洪水作用沉积物;野外调查进一步表明,沉积物无水流作用痕迹;OSL和AMS14C年代测定表明,黑褐色土层形成的年代对应于23.8-10.6 ka BP,此年代对应于末次冰期的晚期,其形成于相对冷湿的气候环境.因此,黑褐色土层及其上、下部的黄土层均为风成堆积物.