Emission of CO2, CH4 and N2O from lakeshore soils in an Antarctic dry valley

We measured soil profile concentrations and emission of CO₂, CH₄ and N₂O from soils along a lakeshore in Garwood Valley, Antarctica, to assess the extent and biogeochemical significance of biogenic gas emission to C and N cycling processes. Simultaneous emission of all three gases from the same site indicated that aerobic and anaerobic processes occurred in different layers or different parts of each soil profile. The day and location of high gas concentrations in the soil profile corresponded to those having high gas emission, but the pattern of concentration with depth in the soil profile was not consistent across sites. That the highest gas concentrations were not always in the deepest soil layer suggests either limited production or gas diffusion in the deeper layers. Emission of CO₂ was as high as 47 μmol m⁻² min⁻¹ and was strongly related to soil temperature. Soil respiration differed significantly according to location on the lakeshore, suggesting that factors other than environmental variables, such as the amount and availability of O₂ and nutrients, play an important role in C mineralization processes in these soils. High surface emission (maximum: 15 μmol m⁻² min⁻¹) and profile gas concentration (maximum: 5780 μL L⁻¹) of CH₄ were at levels comparable to those in resource-rich temperate ecosystems, indicating an active indigenous population of methanogenic organisms. Emission of N₂O was low and highly variable, but the presence of this gas and NO₃ in some of the soils suggest that denitrification and nitrification occur there. No significant relationships between N₂O emission and environmental variables were found. It appears that considerable C and N turnover occurs in the lakeshore soils, and accurate accounting will require measurements of aerobic and anaerobic mineralization. The production and emission of biogenic gases confirm the importance of these soils as hotspots of biological activity in the dry valleys and probable reservoirs of biological diversity.     

Effects of residue management and controlled traffic on carbon dioxide and water loss

Management of crop residues and soil organic matter is of primary importance in maintaining soil fertility and productivity and in minimizing agricultural impact on the environment. Our objective was to determine the effects of traffic and tillage on short-term carbon dioxide (CO₂) and water (H₂O) fluxes from a representative soil in the southeastern Coastal Plain (USA). The study was conducted on a Norfolk loamy sand (FAO classification, Luxic Ferralsols; USDA classification, fine-loamy siliceous, thermic Typic Kandiudults) cropped to a corn (Zea mays L.) — soybean (Glycine max (L.) Merr) rotation with a crimson clover (Trifolium incarnatum L.) winter cover crop for eight years. Experimental variables were with and without traffic under conventional tillage (CT) (disk harrow twice, chisel plow, field cultivator) and no tillage (NT) arranged in a split-plot design with four replicates. A wide-frame tractive vehicle enabled tillage without wheel traffic. Short-term CO₂ and H₂O fluxes were measured with a large portable chamber. Gas exchange measurements were made on both CT and NT at various times associated with tillage and irrigation events. Tillage-induced CO₂ and H₂O fluxes were larger than corresponding fluxes from untilled soil. Irrigation caused the CO₂ fluxes to increase rapidly from both tillage systems, suggesting that soil gas fluxes were initially limited by lack of water. Tillage-induced CO₂ and H₂O fluxes were consistently higher than under NT. Cumulative CO₂ flux from CT at the end of 80 h was nearly three times larger than from NT while the corresponding H₂O loss was 1.6 times larger. Traffic had no significant effects on the magnitude of CO₂ fluxes, possibly reflecting this soil’s natural tendency to reconsolidate. The immediate impact of intensive surface tillage of sandy soils on gaseous carbon loss was larger than traffic effects and suggests a need to develop new management practices for enhanced soil carbon and water management for these sensitive soils.     

Bimembrane diffusion probe for continuous recording of dissolved and entrapped bubble gas concentrations in peat

Peatlands are significant sources of the important greenhouse gas CH₄ and generally known as sinks for atmospheric CO₂ through peat accumulation. Accurate measurements of the subsurface concentrations of these gases are of pivotal importance for experimental studies improving our understanding of the dynamics and controls on the exchanges of these gases between peat soils and the atmosphere. In this paper we first briefly outline examples of different probe-based techniques for the determination of subsurface gas concentrations and thereafter we document the development and testing of two different membrane probe systems. Finally we discuss a few applications of the probes and show some results obtained by testing them in the laboratory.     

丙·氰25%乳油的气相色谱分析

[目的]在同柱同条件下,对丙.氰25%乳油中丙溴磷和氰戊菊酯2种组分的分离测定方法进行研究,为企业生产的质量控制及质检机构提供参考。[方法]以5%OV-101色谱柱固定相,邻苯二甲酸双环己酯为内标物,用FID检测器,利用程序升温方法对丙.氰25%乳油中2种组分进行气相色谱分离和测定。[结果]丙.氰25%乳油中2种组分及杂质得到了有效分离,丙溴磷、氰戊菊酯标准偏差分别为0.065、0.047;变异系数分别为0.52%、0.37%;回收率分别为99.06%～100.72%,99.25%～100.63%;线性相关系数分别为0.999 8、0.999 6。[结论]该方法测定丙.氰25%乳油2种有效成分的质量分数,具有分离效果好,准确度、精密度高,线性关系好,符合定量要求,是一种可行的分析方法。     

几个稻米品种（系）中脂肪酸含量的研究

[目的]为植物油品质的改良提供参考,同时为稻米资源的开发利用提供理论依据。[方法]利用气相色谱法对津川2号、盐丰-47、中作_93、E．28、津N-45稻米品种（系）中脂肪酸组成及含量进行分析。[结果]稻米品种（系）中脂肪酸主要为棕榈酸、油酸和亚油酸,其中盐丰47油酸含量最高为35．7％,而津川2号亚油酸含量最高,达到43．1％。[结论]5种稻米的不饱和脂肪酸含量均较高,具有较耋柏苷兼偷梏如井右箭导一高的营养价值和开发前景。     

气相及气相色谱质谱法测定食品中非法添加的石蜡

[目的]建立食品中违法添加石蜡的检测方法。[方法]分别采用气相色谱及气相色谱质谱法对食品中非法添加的石蜡进行检测。[结果]分别建立了食品中石蜡的定性与定量检测方法,确定了以正二十六烷,正二十七烷、正二十八烷、正二十九烷加和峰面积对石蜡进行定量检测的方案。[结论]该方法简便、稳定、适用性强,可用于食品中的石蜡的准确测定。     

Physiological responses of chickpea genotypes to terminal drought in a Mediterranean-type environment

Two field experiments were carried out to investigate the effects of terminal drought on chickpea grown under water-limited conditions in the Mediterranean-climatic region of Western Australia. In the first experiment, five desi (small angular seeds) chickpeas and one kabuli (large round seeds) chickpea were grown in the field with and without irrigation after flowering. In the second experiment, two desi and two kabuli cultivars were grown in the field with either irrigation or under a rainout shelter during pod filling. Leaf water potential (Ψ_l), dry matter partitioning after pod set and yield components were measured in both experiments while growth before pod set, photosynthesis, pod water potential and leaf osmotic adjustment were measured in the first experiment only.

In the first experiment, total dry matter accumulation, water use, both in the pre- and post-podding phases, Ψ_l and photosynthesis did not vary among genotypes. In the rainfed plants, Ψ_l decreased below −3 MPa while photosynthesis decreased to about a tenth of its maximum at the start of seed filling. Osmotic adjustment varied significantly among genotypes. Although flowering commenced from about 100 days after sowing (DAS) in both experiments, pod set was delayed until 130–135 DAS in the first experiment, but started at 107 DAS in the second experiment. Water shortage reduced seed yield by 50 to 80%, due to a reduction in seed number and seed size. Apparent redistribution of stem and leaf dry matter during pod filling varied from 0 to 60% among genotypes, and suggests that this characteristic may be important for a high harvest index and seed yield in chickpea.     

气辅成型注气压力的PID控制应用研究

建立了注气压力曲线的控制模型，对注气压力曲线的PID控制算法进行了研究，提出了提高注气压力控制精度的扩充临界比例带法的PID参数计算公式，并在研制的小型气辅装置上进行了实验验证.结果表明：扩充临界比例带法是一种基于系统临界振荡参数的闭环整定法，可以优化参数，提高控制精度。     

基于ARM9的电子鼻系统设计与应用

提出了一种基于嵌入式电子鼻的设计方案,主要包括传感器阵列、模数转换和微处理器3大模块.采用Figaro公司TGS813、TGS825、TGS880 3个气敏传感器组成的传感器阵列采集样品信号;利用MAXIM公司的MAX1270芯片进行模数转换;CPU采用SAMSUNG公司的S3C2410微处理器,并在其上移植了WINCE操作系统.软件设计对采集信号进行对数拟合,采用引进BP神经网络对拟合后的曲线参数进行训练,建立模型并对样本进行识别.利用该系统对4种不同生产日期的意大利巴马臣干酪和3家公司的纯牛奶进行了测试,识别准确率均达到100%.结果表明该系统具有体积小、重量轻、使用方便灵活且识别准确率高等优点.     

汽车加速过程噪声分析与控制

提出了基于变时基短时傅里叶变换来分析和处理时变信号的技术。运用该技术对某汽车的加速噪声进行测量和分析,发现发动机进气噪声是该车主要的加速噪声源。通过对该车进气系统的改进设计,使该车车外加速噪声达到了限值要求。