福建省兴化湾大气重金属的干湿沉降

在兴化湾周围采集1年的大气颗粒物及降雨样品,测定分析了Cd,Pb,Zn和Cu 4种重金属的含量及其大气干湿沉降通量随季节的变化规律,并利用Pb同位素对大气颗粒物的来源进行了解析.结果表明:大气重金属的干沉降通量随季节变化不大,而湿沉降通量随季节变化明显.大气干沉降通量中,Cd,Cu随季节变化很小,而Pb,Zn有一定的季节变化,主要是因为降雨对大气颗粒物的去除作用.大气湿沉降通量中,所有重金属元素受降雨量影响显著,另外还与季节和风速有关.除Pb外,Cd,Zn和Cu的湿沉降通量均大于干沉降通量,说明湿沉降在大气对兴化湾重金属的输入过程中起主导作用.而Pb的输入则以颗粒态为主.根据Pb稳定同位素分析,兴化湾大气颗粒物中的重金属主要来源于工业活动.      

大气沉降向华中丘陵区稻田输入硫通量的观测

选取我国华中丘陵区的湖南省长沙县一个典型水稻种植区,对2015与2016年2年雨水样中的SO₄²-S和大气SO₂的沉降量进行监测,分析雨水中SO₄^2-、NO₃^-的关系,解析大气硫沉降的主要来源.结果表明,研究区大气中SO₂-S和雨水中SO₄^2--S的年均浓度分别为8.5 μg/m³和1.1mg/L,大气硫沉降年均总量为26.8kgS/（hm²·a）,其中年均降雨混合沉降量18.2kgS/（hm²·a）,年均干沉降量为8.6kgS/（hm²·a）.研究区域硫素干、混合沉降量存在明显的季节差异,硫素混合沉降春季高于夏、秋、冬季,而硫素干沉降冬季高于春、夏、秋季.雨水中NO₃^-/SO₄^2-的质量比大多小于1,表明研究区大气硫素主要来自固定污染源（燃煤）.华中丘陵区稻田具有较高的硫沉降,但硫沉降量已较21世纪初出现了较大幅度下降,农业生产中需要根据农田硫素收支状况酌情补充硫肥来保证作物高产稳产.     

三峡库区大气活性氮组成及干沉降通量

为了解三峡库区腹地大气中活性氮的组成及干沉降通量,于2015年每个季节选取代表性月份在万州城区采集了气体和颗粒物样品.利用离子色谱法测定氮素浓度,同时结合大叶阻力模型模拟计算的干沉降速率值,估算了不同形态氮素的干沉降通量.结果表明,HNO₃的干沉降速率值最大,年均值为0.39cm/s,约为其它氮素的3~8倍.NO₂和NH₃是大气活性氮的主要赋存形态,年均浓度值分别为（11.7±3.9）和（11.0±5.3）μg N/m³,两者之和约占总无机氮浓度的80%.万州城区总无机氮干沉降总量为8.5kg N/（hm²·a）,其中氧化态氮（NO₂、HNO₃、颗粒态NO₃^-）和还原态氮（NH₃、颗粒态NH₄⁺）干沉降通量分别为3.5,5.0kg N/（hm²·a）,占干沉降总量的41.4%和58.6%.因此,为有效控制三峡库区腹地的氮素污染,应重点关注NH₃的减排.     

沿海滩涂生态型围垦指标体系研究

随着近几年滩涂围垦工程的进行,为了协调围垦开发与生态环境保护之间的矛盾,生态型围垦的理念应运而生。本文对"生态型围垦"的内涵进行了深入辨析,提出了沿海滩涂生态型围垦概念模型,针对围垦工程规划前期、工程实施和运行管理3个阶段的特点,从管理、环境和生态3个方面提出相应指标,初步构架了生态型围垦指标体系,为沿海滩涂围垦的可持续及匡围区域生态环境管理提供技术支撑。     

不同后处理器对DMCC发动机PM排放的影响

在一台整车排放达到国Ⅲ标准的YC4D140电控单体泵增压中冷柴油机上加装甲醇喷射系统,改成柴油甲醇组合燃烧(DMCC)发动机.使用AVL 415S烟度计和DMS 500快速颗粒物光谱仪研究不同后处理器对DMCC发动机颗粒物(PM)排放的影响.试验结果表明,各工况下单独CDPF、DOC+CDPF基本可以消除发动机产生的干炭烟.DOC+CDPF后处理方式与单独CDPF相比,颗粒物捕集效率明显提高,且前者对颗粒物中核态部分的捕集效果更加突出.甲醇掺烧后,炭烟和颗粒物几何平均直径降低.经CDPF和DOC+CDPF处理,415S烟度计测得的炭烟进一步降低;DMS颗粒物光谱仪显示的颗粒物粒径,因其中核态部分大部被氧化捕集而仅余较大几何平均直径的部分.小负荷时经CDPF和DOC+CDPF处理,颗粒物的几何平均直径会增大,大负荷时则相反.各工况下相比于CDPF,DOC+CDPF对核态颗粒物捕集更有效.     

Effects of Conversion of Dry Tropical Forest to Agricultural Mosaic on Herpetofaunal Assemblages

Abstract: We explored the impact of forest conversion to agricultural mosaic on anuran, lizard, snake, and turtle assemblages of Neotropical dry forests. Over 2 years, we sampled 6 small watersheds on the west coast of Mexico, 3 conserved and 3 disturbed. The disturbed watersheds were characterized by a mosaic of pastures and cultivated fields (corn, beans, squash) intermingled with patches of different successional stages of dry forest. In each watershed, we conducted 11 diurnal and nocturnal time‐constrained searches in 10 randomly established plots. We considered vulnerability traits of species in relation to habitat modification. Eighteen anuran, 18 lizard, 23 snake, and 3 turtle species were recorded. Thirty‐six species (58%) occurred in both forest conditions, and 14 (22%) and 12 species (19%) occurred only in the conserved and disturbed sites, respectively. Assemblages responded differently to disturbance. Species richness, diversity, and abundance of lizards were higher in disturbed forests. Anuran diversity and species richness were lower in disturbed forest but abundance was similar in both forest conditions. Diversity, richness, and abundance of turtles were lower in disturbed forest. The structure and composition of snake assemblages did not differ between forest conditions. We considered species disturbance sensitive if their abundance was significantly less in disturbed areas. Four anuran (22%), 2 lizard (11%), and 3 turtle (100%) species were sensitive to disturbance. No snake species was sensitive. The decline in abundance of disturbance‐sensitive species was associated with the reduction of forest canopy cover, woody stem cover, roots, and litter‐layer ground cover. Anuran species with small body size and direct embryonic development were especially sensitive to forest disturbance. An important goal for the conservation of herpetofauna should be the determination of species traits associated with extinction or persistence in agricultural mosaics.     

SOME GEOMORPHIC RELATIONSHIPS AND HYDROGRAPH ANALYSIS1

ABSTRACT: First order drainage channels originate when the tractive force exerted by flowing water is sufficient to move surface sediment. The amount of runoff available to move sediment is a function of geologic and climatic characteristics. An experimental analysis showed that soils derived from fine grained rocks had lower infiltration rates and higher runoff volume than soils derived from coarser grained rocks in a semi-arid climate. Root density and penetration increased in a more humid climate and increased infiltration rates. The number of first order channels was inversely proportional to the infiltration capacity of the soil. Each first order channel acts as a source area for surface runoff. The distribution of first order channel distances from the gage determines the timing of the delivery of water to the gage. A comparison of the frequency histogram of first order channel distances for drainage basins in Pennsylvania and their hydxographs of runoff from general storms showed marked similarity. This close correspondence indicated the shape of the surface runoff hydrograph and was largely controlled by the distribution of first order channel distances.     

热带亚热带多雨湿润区旱地土壤氮肥淋溶损失模拟研究

用土柱研究旱地土壤60cm土体夏季的氮肥淋溶损失,结果表明,在土壤施尿素后35d内淋水350mm,在不产生泾流的条件下,淋失率平均为25．5％。还探讨了氮肥淋溶过程中的氮形态变化,以及施氮量和土层深度对氮肥淋浴损失的影响。     

DRY STREAM REACHES IN CARBONATE TERRANES: SURFACE INDICATORS OF GROUND-WATER RESERVOIRS1

ABSTRACT: The method of identifying dry stream reaches in carbonate terrane as surface indicators of potential ground-water reservoirs offers a valuable exploration technique that is more rapid and less expensive than traditional exploration methods involving random test drilling. In areas where dry stream reaches occur, subsurface drainage successfully competes with surface drainage, and sheet-like dissolution openings have developed parallel to bedding creating the ground-water reservoir. The occurrence and hydraulic characteristics of such reservoirs are highly variable, as attested to by the wide range of well yields. Union Hollow in south-central Tennessee is the setting for a case study that illustrates the application of the dry stream reach technique. In this technique, dry stream reach identification is based on two types of readily acquired information: (1) remotely sensed black and white infrared aerial photography; and (2) surface reconnaissance of stream channel characteristics. Test drilling in Union Hollow subsequent to identification of the dry reach proved that a localized ground-water reservoir was present.     

STABILITY AND REACH LENGTH IN WATER SURFACE PROFILE DETERMINATION1

ABSTRACT: Extension of basic step methods of backwater computation to reaches of finite length is examined. Accuracies of commonly accepted hydraulic loss equations under particular water surface profile conditions are compared. Simulation of energy lines within a reach by parabolic curves is found to minimize error provided orientation of the axis of the parabola is selected in accordance with prevailing hydraulic conditions. Theoretical basis for an index reach length beyond which single-step computation from end to end of the reach must be in error is developed. Reduction of this reach length by suitable factors tailored to hydraulic conditions yields a mathematically defined allowable reach length for backwater computation. When reach length does not exceed this allowable reach length, no significant error may be detected. Automatic insertion of synthetic cross sections interpolated between surveyed cross sections when these are inadvertently spaced too far apart enables computation to proceed. This device is error-free for prismatic channls but may introduce error for irregular natural channels. Preliminary trials indicate that results so obtained may be accepted provided the fall in the original reach does not exceed from one to two feet. When this is exceeded, additional cross sections should be surveyed.