水质五日生化需氧量(BOD5)测定不确定度的评定

水质五日生化需氧量测量的关键是用碘量法测水中溶解氧的含量,经过分析碘量法测定水中溶解氧含量测量不确定度的影响因素,认为测量的重复性的不确定度分量最大,其次是样品中溶液的体积,滴定溶液的体积和滴定溶液的浓度等不确定度分量.计算得到水中五日生化需氧量的测定结果的合成不确定度为6.4mg/L,扩展不确定度为12.8mg/L.     

Measurement of tropospheric HO2 radical using fluorescence assay by gas expansion with low interferences

An instrument to detect atmospheric HO₂ radicals using fluorescence assay by gas expansion (FAGE) technique has been developed. HO₂ is measured by reaction with NO to form OH and subsequent detection of OH by laser-induced fluorescence at low pressure. The system performance has been improved by optimizing the expansion distance and pressure, the influence factors of HO₂ conversion efficiency are also studied. The interferences of RO₂ radicals were investigated by determining the conversion efficiency of RO₂ to OH during the measurement of HO₂. The dependence of the conversion of HO₂ on NO concentration was investigated, and low HO₂ conversion efficiency was selected to realize the ambient HO₂ measurement, where the conversion efficiency of RO₂ derived by propane, ethene, isoprene and methanol to OH has been reduced to less than 6% in the atmosphere. Furthermore, no significant interferences from PM_2.5 and NO were found in the ambient HO₂ measurement. The detection limits for HO₂ (S/N = 2) are estimated to 4.8 × 10⁵ cm^?3 and 1.1 × 10⁶ cm^?3 (${\rho }_{\mathrm{H}{\mathrm{O}}_2}$= 20%) under night and noon conditions, with 60 sec signal integration time. The instrument was successfully deployed during STORM-2018 field campaign at Shenzhen graduate school of Peking University. The concentration of atmospheric HOx radical and the good correlation of OH with j(O¹D) was obtained here. The diurnal variation of HOx concentration shows that the OH maximum concentration of those days is about 5.3 × 10⁶ cm^?3 appearing around 12:00, while the HO₂ maximum concentration is about 4.2 × 10⁸ cm^?3 appearing around 13:30.     

水中悬浮物干扰溶解氧测定结果的探讨

通过滤液和混样测定溶解氧的对比实验，探讨和分析悬浮物对溶解氧测定结果的干扰．     

水样中铵氮测量的不确定度评定

通过对铵氮测定过程的分析,找出了影响测定结果的各个分量。影响测定结果的分量主要有:标准溶液、回归曲线、试样平行试验、纳氏试剂分光光度法、分光光度计,取样等。在此基础上对测量的不确定度进行了评定,并按照计量技术规范,给出了标准的表示法。     

以微型计算机为基础的现场尘粒浓度测量仪

本文提出一种对有害尘粒污染源排放实施现场连续监测系统。仪器具有光电收发对称式尘粒浓度探测头、光学界面沾染自校正单元以及可编程锁相放大器。微机作为中心控制单元，完成光源调制、电机驱动、相移和灵敏度自动调整，实现数据采集与处理，发布测量结果并协调各单元运行。最后，给出了由比较性测量所得实验数据。     

Sample support and related scale issues in composite sampling

Composite sampling offers the great promise of efficiency and economy in environmental decision making. However, if careful attention is not paid to matching the support of the sample to that required for making the desired decision, the promise is unfulfilled. Obviously this attention must be applied in the design phase of a composite sampling strategy. Less obvious is the potential for alteration of the design sample support during sample collection and assay. The consequences of not paying attention to these aspects of sample design and assay are discussed in this issue paper illustrated with a series of examples taken from the authors consulting experience.     

Settlement patterns of female barn swallows Hirundo rustica across different group sizes: access to colorful males or favored nests?

In most avian species, individuals are faced with two critical decisions at the start of a breeding season: choosing a breeding site and a mate. An analysis of these decisions in light of population-level patterns, such as group size variation in social breeders, can illuminate the causes and patterns of habitat selection behavior. Group sizes are variable in barn swallows; however, no clear and consistent benefits of group breeding have been found in this species, and it is puzzling as to why individuals breed socially. Previous analyses demonstrated that individuals aggregate to gain access to nests that were constructed during previous seasons; however extra-pair matings are also prevalent in this species, raising questions about the mate-selection strategies of females across different group sizes. In this paper, I address the question of how females make their first site-selection decisions in terms of two features known to be causally related to seasonal reproductive success: (1) colorful males or (2) old nests. Using experimental and observational data, I tested, but found no support for, the hypotheses that propose female settlement decisions are a function of (1) the prevalence of colorful males or (2) the increased opportunity for extra-pair matings at group sites. Instead, it is apparent that female settlement patterns are strongly tied to the availability of old nests at a site. Extra-pair fertilizations are equally common across all group sizes in this population, suggesting that females do not face a trade-off between old nests and the possibility of extra-pair mating decisions when making settlement decisions.     

冷原子吸收法对水中汞溶液浓度测量结果的不确定度评定

对冷原子吸收法测量水中汞溶液浓度的影响因素作了全面分析,对各因素的不确定度进行评估,评定了冷原子吸收法对水中汞溶液浓度测量结果的不确定度。     

A PRELIMINARY QUANTIFICATION OF THE IMPACTS OF ASPEN TO CONIFER SUCCESSION ON WATER YIELD - I. HEAT PULSE METHODOLOGY FOR MODEL CALIBRATION1

ABSTRACT: Twenty-six aspen (Populus tremuloides Michx.), 20 subalpine fir (Abies lasiocarps (Hook.) Nutt.), and 20 Engelmann spruce (Pices engelmanil (Parry) Engelm.) of various sizes were cut under water and suspended in permanent reserviors at a northern Utah site. The reservoirs were asealed so that all water loss was due to consumption by the trees. Sap velocities, as computed from heat pulse velocities, were related to conducting areas of the tree trunks. Computed transpiration volumes were then correlated with actual water losses from the reservoirs. Coefficients of determination (R²) of 0.87, 0.86, and 0.82 were obtained for the fir, aspen, and sprucs, respectively. Reservoir water loss for each species for each season was then used to adjust a plant activity index for computing transpiration within ASPCON, a model describing the hydrology of aspen to conifer succession. The plant activity index reflects the variation in the capability of a plant community to transpire water over the year. Assumptions and limitations of the heat pulse velocity technique are also outlined.     

CHEMICAL PRECIPITATION-COAGULATION FOR ORGANIC COLOR REMOVAL FROM GOUNDWATERS1

ABSTRACT: Many wells produce water that is highly colored by organic substances. Colored water may cause aesthetic, economic, and health problems for the cities using it as a municipal supply. Characterization of water from a number of wells showed that the color causing compounds were hydroxylated aromatic carboxylic acids which were precipitated below pH 4.5 and were almost completely ionized above pH 4.5. Through jar tests, a chemical precipitation-coagulation treatment system was developed. The optimal sequence of chemical addition was alum first, followed by pH adjustment and addition of a polyelectrolyte. Rapid mix tests demonstrated the need for a reaction period after alum and after acid addition, and that the rapid mix time controlled floc size for a given flocculation period. Flocculation tests, varying both the floc time and mean velocity gradient, G, showed that an optimum G exists for each floc time and that the residual color decreased with decreasing values of velocity gradient.