新疆罗布泊地区水硝碱镁矾和钠硝矾的矿物学研究

本文报道了我国新发现的两个硝酸盐-硫酸盐复盐矿物——水硝碱镁矾和钠硝矾。水硝碱镁矾呈假四方双锥状,属三方晶系,解理{0001}完全,一轴负晶,折光率为ω=1.474,ε=1.436:晶胞参数α=1.0894nm,c=2.4396nm,粉晶图的强衍射线为:2.813(100),8.096(19)1.991(18),3.391(10),2.199(8),8.751(8)。钠硝矾为板状,板柱状,解理{010}完全,{100}不完全。聚片双晶平行(100),二轴负晶,折光率为:α=1.487,β=1.481,γ=1.391;-2V=28°。矿物属单斜晶系,晶胞参数为:α=1.0565nm,b=0.6922nm,c=0.5194nm。粉晶图的强衍射线为:10.3(100),3.46(35),2.594(30),2.871(30),2.856(30),4.13(20)。文中还列出了两矿物的差热和红外吸收光谱等资料。     

What controls levels of dissolved phosphate and ammonium in surface waters?

Dissolved inorganic nutrient pools are small relative to particulate pools, and dissolved pools turnover rapidly. It has been observed that pools change little from day to day on the sampling scales usually employed. A simple model is presented where uptake and regeneration rates balance to cause a local steady state concentration for dissolved inorganic nutrients. Enrichment and dilution perturbation experiments with lake water support the idea of steady state nutrient concentrations. Although inorganic nutrient concentrations are often controlled by biota, the absolute concentrations present tell little about the activity of that biota.     

Assessment of the Uncertainties in the NO2 and O3 Measurements by Visible Spectrometers

The column amounts of nitrogen dioxide (NO2) and ozone (O3) were measured using a visible spectrometer based on the twilight zenith-sky technique at two observatories located at similar latitudes in the northern part of Japan separated by a distance of 150 km. The measurements began in April 1991 at the Moshiri Observatory (44.4°N, 142.3°E) and in April 1994 at the Rikubetsu Observatory (43.5°N, 143.8°E). Since weather conditions and the possible influence from tropospheric pollution were not always identical at these two observatories, the overall accuracy of the measurements was studied comparing these data sets. The first year data obtained at a solar zenith angle of 90 degrees indicated that the NO2 slant column values at sunrise and sunset agreed within 0.36 and 0.54 × 1016 cm-2, respectively, corresponding to 5 % (June) and to 12 % (December) of the columns. The O3 values agreed within 0.76 × 1019 cm-2, corresponding to 4 % (March) 6 % (August) of the columns, although a part of the difference was systematic. The O3 column amounts were also compared to those obtained by the Dobson spectrometer at Sapporo (43.5°N, 143.8°E), whose latitude is similar to these observatories. When an air mass factor of 17.5 was used, the two-year Moshiri vertical column values agreed with the Dobson direct sun values to within 15 Dobson Units, or 3 6 % of the column. The difference between the two values was found to be due partly to the change in the air mass factor caused by seasonal and day-to-day changes in the shape of the O3 vertical profiles. These results confirm the reliability of the NO2 and O3 measurements by visible spectrometers at these sites for the Network for the Detection of Stratospheric Change (NDSC).     

半微量凯氏法测定土壤全氮量的不确定度评定

以半微量凯氏法测定土壤中全氮量为例，对测定结果的不确定度来源进行了详细分析，对测定过程中的主要不确定度分量进行了合理评定，包括样品和标准物质硼砂的称量引入的不确定度，硼砂的纯度引入的不确定度，容量瓶、移液管和滴定管的体积引入的不确定度．相关元素的摩尔质量引入的不确定度以及测量的重复性引入的不确定度。最后合成标准不确定度．通过乘以95％置信概率下的扩展因子2获得测量结果的扩展不确定度。     

离子色谱法测定水果和蔬菜中硝酸盐

利用DIONEX-2020i离子色谱仪、IonPac AS3分离柱对蔬菜和水果中硝酸盐进行测定。通过．等冀合适的前处理方法，获得纯清溶液。提出只使用分离柱，以提高灵敏度、缩短出峰时间和改善峰形。方法精密度好、检出限低、操作简便快速，用于实际样品的检测，10次测定的相对标准偏差小于2％，加标回收率为97％～98％。     

多目标地球化学调查土壤样品中氮和碳的快速测定

详细研究了元素分析仪的工作条件，建立了直接固体进样同时测定多目标地球化学调查土壤样苎支氮、碳的方法。方法简便、快速，检出限为氮14．5μg／g、碳0．013％。经土壤国家一级标准物质分析验证，测定值与标准值相符，精密度（RSD，n=12）为氮1．49％-3．27％、碳0.64％～3.63％。     

The Atmospheric Oxidation of the HS Radical: Reaction with NO2

The atmospheric reaction between HS and NO₂ was theoretically investigated at 298 K and 1 atm of pressure. Our results show that the first reaction step will lead to the formation of HSNO₂ or HSONO, spontaneously and exothermically. HSONO easily decomposes into HSO + NO. On the other hand, HSNO₂ can hardly dissociate in the reactants, and its isomerization to other adducts is much hindered. Production of HNO + SO and SNO + OH was found to be unfavorable. Thus, the main products would be HSO + NO and HSNO₂, and new investigations focusing on the atmospheric fate of HSNO₂ are suggested. A general discussion of the fate of HS under atmospheric conditions is presented. Recent investigations indicate that NO₂, O₂ and N₂O should be the most important oxidants of HS, while the O₃ influence will not be significant.     

Potential salinity limitations on nitrogen fixation in sediments from Mono Lake, California

Mono Lake is a hypersaline alkaline lake in the high altitude Great Basin desert of eastern California. Algal productivity of the lake is nitrogen-limited, and a contributing source is derived from benthic nitrogen fixation. Lake level and salinity have fluctuated with natural climatic variations but have also been affected by the diversion of tributary streams. This research examines the influence of varied salinity and lake level on the potential for benthic nitrogen fixation in Mono Lake. A sediment-surface microbial mat community was exposed directly, and in acclimated cultures, to a range of Mono Lake salinities under anaerobic incubations and the activity of nitrogenase assayed by acetylene reduction. Activity was stimulated in light, but also occurred in darkness. Over an experimental salinity range from 50 to 150 g L⁻¹ TDS, nitrogenase activity was reduced by 90 per cent, with the activity persisting at the highest salinity being attributable to dark fixation alone. Between a salinity of 50 g L⁻¹, occurring in Mono Lake over 50 years ago, and 100 g L⁻¹, nitrogenase activity was reduced by nearly half. Changes in the area of the littoral zone at varied lake levels also affect the total amount of potential benthic nitrogen fixation in the lake. An accounting of yearly inputs of nitrogen to Mono Lake suggests N₂-fixation could contribute as much as 76–81 percent of the total. Inhibition of nitrogen fixation rates by increased salinity could limit the long-term nutrient supply and benthic primary productivity of this ecosystem.