大气CO_2浓度升高对植物影响的研究进展

CO2是植物光合作用的底物,也是构成植物生境的一种环境因子。随着现代工农业的发展与人类活动的增加,大气中CO2浓度将会不可避免的呈升高趋势。这种趋势将对植物生长发育及生物产量产生影响,最终将影响人类的生存环境,因此,近年来对其研究逐渐增多。综述了国内外学者对植物的形态学特征、生物量的变化、生理生化机制、根系分泌物及根际微生物等受大气中CO2浓度升高的影响等方面的研究。结果表明,CO2的浓度升高会增加植物的根系面积、增加叶片的厚度、促进根系分泌物的释放,改变根际微生物的多样性,也可能会提高植物的呼吸作用和光合速率。     

Measured deuterium in water vapour concentration does not improve the constraint on the partitioning of evapotranspiration in a tall forest canopy, as estimated using a soil vegetation atmosphere transfer model

Partitioning the evapotanspiration (ET) flux in a forest into its component fluxes is important for understanding the water and carbon budgets of the ecosystem. We use non-linear parameter estimation to determine the vertical profile of the Lagrangian timescale (T_L) and partitioning of ET that simultaneously optimise agreement between modelled and measured vertical profiles of temperature, water vapour, carbon dioxide concentrations, and deuterated water vapour for a two-week period in November 2006. High precision real-time trace gas measurements were obtained by FTIR spectroscopy. Modelled temperature and concentration profiles are generated using a Lagrangian dispersion theory combined with source/sink distributions of HDO, H₂O, sensible heat, and CO₂. These distributions are derived from an isotopically enabled multilayer Soil Vegetation Atmospheric Transfer (SVAT) model subject to multiple constraints. The soil component of the model was tested in isolation using measured deuterium content of soil chamber evaporate, while the leaf component was tested using isotopic analyses of leaf and xylem water, combined with leaf-level gas exchange measurements. Optimisation of T_L and the partition of ET was performed twice: once using only temperature, H₂O and CO₂ profiles and a second time including HDO as well. The modelled vertical concentration profiles resulting from inclusion of HDO in the cost function demonstrate our ability to make consistent estimates of both the scalar source distributions and the deuterium content of the water vapour sources. However, introducing measurements of deuterium in water vapour does not significantly alter resulting estimates of normalised T_L (0.4 ± 0.1 at canopy top) and the partition of ET (85 ± 2% transpiration), suggesting that the additional data and modelling required to use deuterium are not warranted for the purpose of partitioning ET using the framework presented here.     

强烈人为作用下城镇周围汞的空间变异及其积累迁移规律

研究土壤中汞(Hg)元素积累的空间变异和迁移转化规律对土壤利用、环境评价和污染修复具有重要参考价值。本研究选择经济发展迅速的苏南某地为研究区域,对土壤、水稻和大气降尘中的Hg进行了详细分析。结果表明,该区域土壤全汞平均含量达1 345μg kg-1,有效汞(HC l-Hg)平均含量51μg kg-1,水稻Hg平均含量20μg kg-1,大气Hg沉降量为5.13 g km-230 d-1。土壤和水稻高含量Hg主要积聚于城镇周边,随着与城镇距离的增加其含量逐渐减少。大气Hg沉降量在空间上变化不大。进入土壤中的Hg主要在土壤表层0~20 cm范围内富集,但直至60 cm深处依然存在积累现象,整个剖面土壤活性态汞和半活性态汞含量占全汞的比例变化不大。研究区土壤出现了明显Hg积累,导致水稻Hg吸收明显增加,不少样点超过了国家土壤环境质量二级标准(300μg kg-1)和国家食品污染物限量标准(20μg kg-1),可能对环境和人体健康产生危害。较低的大气Hg沉降量和土壤积累的Hg已与土壤条件达到平衡的事实表明,目前Hg的积累已明显减少。今后应采取措施修复污染土壤或者通过改变作物种类来减少土壤Hg含量或抑制作物对Hg的吸收,达到环境治理的目的。     

Elevated CO2, but not defoliation, enhances N cycling and increases short-term soil N immobilization regardless of N addition in a semiarid grassland

Elevated CO₂ and defoliation effects on nitrogen (N) cycling in rangeland soils remain poorly understood. Here we tested whether effects of elevated CO₂ (720 μl L⁻¹) and defoliation (clipping to 2.5 cm height) on N cycling depended on soil N availability (addition of 1 vs. 11 g N m⁻²) in intact mesocosms extracted from a semiarid grassland. Mesocosms were kept inside growth chambers for one growing season, and the experiment was repeated the next year. We added ¹⁵N (1 g m⁻²) to all mesocosms at the start of the growing season. We measured total N and ¹⁵N in plant, soil inorganic, microbial and soil organic pools at different times of the growing season. We combined the plant, soil inorganic, and microbial N pools into one pool (PIM-N pool) to separate biotic + inorganic from abiotic N residing in soil organic matter (SOM). With the ¹⁵N measurements we were then able to calculate transfer rates of N from the active PIM-N pool into SOM (soil N immobilization) and vice versa (soil N mobilization) throughout the growing season. We observed significant interactive effects of elevated CO₂ with N addition and defoliation with N addition on soil N mobilization and immobilization. However, no interactive effects were observed for net transfer rates. Net N transfer from the PIM-N pool into SOM increased under elevated CO₂, but was unaffected by defoliation. Elevated CO₂ and defoliation effects on the net transfer of N into SOM may not depend on soil N availability in semiarid grasslands, but may depend on the balance of root litter production affecting soil N immobilization and root exudation affecting soil N mobilization. We observed no interactive effects of elevated CO₂ with defoliation. We conclude that elevated CO₂, but not defoliation, may limit plant productivity in the long-term through increased soil N immobilization.     

Soil–methane sink increases with soil age in forefields of Alpine glaciers

In upland soils aerobic methane-oxidizing bacteria (MOB) catalyze methane (CH₄) oxidation, and thus regulate the sole terrestrial sink for atmospheric CH₄. While confirmed in mature upland soils, little is known about this important function in young mountainous soils in glacier forefields, which are progressively formed as a result of glacier recession. We assessed four attributes of the soil CH₄ sink, i.e., soil-atmosphere CH₄ flux (J_atm), CH₄ oxidation activity (k), MOB abundance and variation in community composition along the 6–120-yr soil chronosequence in two Alpine glacier forefields on siliceous and calcareous bedrock. At most sampling locations soil CH₄ profiles showed stable uptake of atmospheric CH₄, with J_atm in the range of −0.082 to −2.2 mg CH₄ m⁻² d⁻¹. Multiple-linear-regression analyses indicated that J_atm significantly increased with soil age, whereas k did not. Instead, water content and CH₄ profiles in the youngest soils often indicated dry, inactive top layers with k < 0.1 h⁻¹, and active deeper layers (0.2 h⁻¹ ≤ k ≤ 11 h⁻¹) with more favorable water content. With increasing soil age the zone of highest CH₄ oxidation activity gradually moved upwards and eventually focused in the 10–40-cm layer (0.2 h⁻¹ ≤ k ≤ 16 h⁻¹). Copy numbers of pmoA genes significantly increased with soil age at both sites, ranging from 2.4 × 10³ to 5.5 × 10⁵ copies (g soil w.w.)⁻¹, but also correlated with mineral nitrogen content. Terminal restriction-fragment-length-polymorphism and cluster analyses showed differences in MOB community composition apparently related to bedrock type rather than soil age. Yet, regardless of bedrock type, the soil CH₄ sink established within a few years of soil development, and J_atm increased to values comparable to mature soils within decades. Thus, young mountainous soils have the potential to consume substantial amounts of atmospheric CH₄, and should be incorporated into future estimates of global soil CH₄ uptake.     

常温等离子体诱变选育醋酸发酵菌株

[目的]选育具有耐温特性的醋酸菌,用于醋酸发酵。[方法]从醋醅中筛选具有较好耐温特性的醋酸菌,并且通过常温等离子体诱变提高该菌株的发酵效率。[结果]从山西老陈醋醋醅中筛选获得一株醋酸菌WL021,经鉴定属于巴氏醋杆菌(Acetobacter pasteurianus),最适发酵温度为35℃。对该菌株进行常温等离子体诱变处理,获得在35℃条件下具有较高醋酸发酵效率的菌株WL021-1。利用15 L自吸式发酵罐,在发酵温度35℃、通气量0.15 vvm、乙醇浓度7%的条件下,巴氏醋杆菌WL021-1平均发酵效率为1.10 g/(L·h),与出发菌株相比终酸浓度和酒精转化率没有显著差异,但发酵周期缩短约7 h,发酵效率提高约10%。[结论]选育获得醋酸发酵菌株巴氏醋杆菌WL021-1,最适发酵温度35℃。该菌株的工业应用有利于降低发酵过程降温成本。     

重庆市大气环境多氯萘污染研究

对重庆市大气环境多氯萘污染情况进行了较为系统的调研研究.采集了表征大气环境背景值、典型居民区、校区、工业区等大气质量的11个采样点的大气样品,采用了同位素稀释-高分辨气相色谱质谱法进行了检测,14种目标化合物均有检出,总的多氯萘(PC-Ns)检出浓度为1.20 ～6.13 pg/m3,居民区和校区大气多氯萘含量要明显低于工业区,大气样品中PCNs污染主要贡献者是1～3氯代的低氯代PCNs,多分布在气相中,颗粒物中较少.     

The effect of etching on low-stress mechanical properties of polypropylene fabrics under helium/oxygen atmospheric pressure plasma

Polypropylene nonwoven fabrics were exposed to He/O₂ atmospheric pressure glow discharge plasma. Surface chemical analysis and contact angle measurement revealed the surface oxidation by formation of new functional groups after plasma treatment. Weight loss (%) measurement and scanning electron microscopy analysis showed a significant plasma etching effect. It was investigated in low-stress mechanical properties of the fabrics using Kawabata Evaluation System (KES-FB). The surface morphology change by plasma treatment increased surface friction due to an enhancement of fiber-to-fiber friction, resulting in change of other low-stress mechanical properties of fabric.     

Longwave radiation environment of an irrigation reservoir surrounded by mountains

In areas where irrigation facilities are not available or in mountainous areas, reservoirs are used for paddy rice culture in Japan. Water temperature must be adequately maintained because it affects water quality and has a significant impact on the growth and yield of the rice crop. Stratification of water in a reservoir occurs due to heat storage on the water surface by solar radiation, and destratification results from vertical mixing by wind-induced flow and heat convection. This study used a simple topography model to estimate numerically the spatial distribution of longwave radiation on the water surface of an agriculture reservoir surrounded by mountains. A radiation thermometer was used to estimate global longwave radiation. The spatial and temporal variations of longwave radiation on the water surface were calculated using view factors of objects surrounding the reservoir. The simulation showed that longwave radiation absorbed by the water surface increased with distance from the center of the reservoir. The proposed procedure can be used to estimate the longwave radiation environment and heat balance on a water body such as a reservoir and a stream.     

黑龙江省夏季林火多发年气象条件及环流特征分析

利用黑龙江省夏季林火的火场资料、温度、降水和NCEP再分析资料,在分析黑龙江省夏季林火气候背景与林火发生期和发生前期气象条件的基础上,研究黑龙江省夏季林火多发年大气环流特征,结果表明：进入21世纪以来,黑龙江省夏季林火呈明显增多的趋势;夏季林火发生前期（春季）的气候条件并不是夏季林火是否发生的决定性因素;夏季持续高温少雨天气,为林火的发生提供了有利的气象条件,林火发生期（夏季）的旱涝状况是决定林火是否发生的关键因子;林火多发年高低空大气环流均存在异常变化。高低空大气环流的配置．均不利于黑龙江省夏季降水的出现,从而为夏季林火的发生提供了有利的气象条件。