大气高CO2浓度对油菜氮素同化累积与植株生长的影响

为了指导高CO2浓度条件下甘蓝型油菜Brassica napus L.合理施氮、创建油菜高产高效以及进一步探明油菜氮代谢的调节机制提供理论依据,本研究采用微区试验,研究2个油菜品种（沪油15-33号和742-2）在2个CO2浓度水平（自然CO2摩尔分数400μmol·mol-1和高CO2摩尔分数（800±20）μmol·mol-1）和2个氮素水平（施氮与不施氮）条件下,氮素同化酶（NR和GS）活性和可溶性蛋白含量的变化,以及油菜地上部干物质量和氮素累积量的响应。试验结果表明,高CO2浓度会提高NR和GS活性;在氮素处理的影响方面,NR活性的变化与油菜的品种和生育时期不同有关：在高CO2浓度条件下,品种A在各时期的施氮处理的酶活性高于不施氮处理;品种B只在抽薹期的施氮处理低于不施氮处理,其他时期则升高;对于GS酶活性,在自然CO2浓度条件下施氮会提高GS酶活性,高CO2浓度条件下施氮则降低其活性（苗期除外）。CO2浓度升高会降低叶片中可溶性蛋白含量（盛花期除外）;在正常CO2浓度下,增施氮肥会提高叶片中可溶性蛋白含量,而在高CO2浓度下,增施氮肥会降低叶片中可溶性蛋白含量。CO2浓度升高和增施氮肥都会提高油菜地上部干物质量与氮素累积量,油菜干物质量与氮素累积量总体上与上述测定指标呈极显著相关。     

广州市园林绿化植物苗木对二氧化硫和二氧化氮吸收能力分析

采用人工模拟熏气法,研究了36种广州市园林绿化植物对SO2和NO2气体吸收净化能力,以系统聚类分析方法为依据,将参试植物的吸收净化能力划分为强性、较强、中等、较弱及弱5个等级。结果显示,在不同SO2质量浓度（0.259和0.448 mg.m-3）环境下,黄槐、鸡冠刺桐、红花银桦、木棉、红千层、大花紫薇、复羽叶栾树吸收SO2能力具有强或较强的能力,而罗汉松、竹柏、深山含笑、乐昌含笑、观光木、樟树、阴香、双翼豆、印度紫檀、大花五桠果、长芒杜英、五月茶、海南蒲桃、芒果、海南红豆、糖胶树和幌伞枫吸收SO2能力表现为较弱或弱;在NO2质量浓度（0.149和0.428 mg.m-3）环境下,黄槐、黄葛榕、红花银桦、红千层、麻楝、复羽叶栾树、大花紫薇和小叶榄仁吸收净化NO2能力为较强或强,而深山含笑、五月茶、芒果、海南红豆、糖胶树和桂花叶片对NO2吸收能力表现为较弱或弱。在不同SO2和NO2浓度环境下,黄槐、红花银桦、红千层、复羽叶栾树和大花紫薇叶片对SO2和NO2吸收净化能力表现为强或较强,而深山含笑、五月茶、芒果、海南红豆、糖胶树叶片对SO2和NO2吸收净化能力为较弱或弱。研究结果为珠三角城市功能型园林植物选择和广东生态景观林带建设提供科学依据。     

The representation of cyanobacteria life cycle processes in aquatic ecosystem models

Two simplified versions of a numerical life cycle model for diazotrophic cyanobacteria (of the order Nostocales) are developed and evaluated. Both consider two-life cycle stages, one growing, nitrogen-fixing stage and one stage that combines the resting, germinating and vegetative stages. The versions differ in the vertical resolution of the non-diazotrophic stage: version 1 collects the biomass in one layer at the bottom, version 2 considers sinking and rising of biomass explicitly. The results of the two versions are compared with a complex cyanobacteria life cycle model which describes four different life cycle stages each with two internal quotas for energy and nitrogen. The two simplified approaches show a good agreement with respect to the main characteristics of cyanobacteria dynamics (timing and duration of blooms, magnitude of nitrogen fixation, interannual variability). Our model study shows that both simplified approaches are suitable to be implemented into three-dimensional coastal or lake models.     

河岸缓冲区氮素截留研究进展

河岸缓冲区对氮素的有效截留以阻止其进入河流已得到广泛的认可,是美国资源局所认可的一种最佳管理措施。总结河岸缓冲区中氮素截留的主要机制、影响因素及缓冲区的管理原则。最主要截留机制为反硝化作用与植物吸收,相应的最主要影响因素是缓冲区的水文特征。为达到较好的氮素截留效率,必须重建退化的缓冲区、保护缓冲区的完整性与不受干扰,并与其他流域管理措施相结合。     

Evaluation of nitrogen retention and microbial populations in poultry litter treated with chemical, biological or adsorbent amendments

Poultry litter is a valuable nutrient source for crop production. Successful management to reduce ammonia and its harmful side-effects on poultry and the environment can be aided by the use of litter amendments. In this study, three acidifiers, two biological treatments, one chemical urease inhibitor and two adsorber amendments were added to poultry litter. Chemical, physical and microbiological properties of the litters were assessed at the beginning and the end of the experiment. Application of litter amendments consistently reduced organic N loss (0-15%) as compared to unamended litter (20%). Acidifiers reduced nitrogen loss through both chemical and microbiological processes. Adsorbent amendments (water treatment residuals and chitosan) reduced nitrogen loss and concentrations of ammonia-producing bacteria and fungi. The use of efficient, cost-effective litter amendments to maximum agronomic, environmental and financial benefits is essential for the future of sustainable poultry production.     

Modelling above- and below-ground mass loss and N dynamics in wooden dowels (LIDET) placed across North and Central America biomes at the decadal time scale

This article focuses on modelling above and below-ground mass loss and nitrogen (N) dynamics based on the wooden dowels (Gonystylus bancanus [Miq.] Kurz) of the decadal Long-term Intersite Decomposition Experiment (LIDET) data. These dowels were placed at 27 locations across North and Central America, involving tropical, temperate and boreal forests, grasslands, wetlands and the tundra. The dowel, inserted vertically into the soil with one half remaining exposed to the air, revealed fast mass and N losses under warm to humid conditions, and slow losses under wet as well as cold to dry conditions. The model formulation, referred to as the Wood Decomposition Model, or WDM, related these losses to (i) mean annual precipitation, mean monthly January and July air temperatures, and (ii) mean annual actual evapotranspiration (AET) at each location. The resulting calibrations conformed well to the time-in-field averages for mass remaining by location: R² = 0.83 and 0.90 for the lower and upper parts, respectively. These values dropped, respectively, to 0.41 and 0.55 for the N concentrations, and to 0.28 and 0.43 for N remaining. These reductions likely refer to error propagation and to as yet unresolved variations in N transference into and out of the wood specific to each individual dowel location. Recalibrating the model parameters by ecosystem type reduced the R² values for actual versus best-fitted mass loss by about 0.15. Doing the same without location- or ecosystem-specific adjustments reduced the R² values further, by about 0.3.     

Modelling N mineralization from green manure and farmyard manure from a laboratory incubation study

Predicting N mineralization from organic manures like farmyard manure (FYM) is more difficult than from fresh organic materials like crop residues, as the manures vary greatly in composition. A laboratory incubation experiment was carried out for 98 days at 30 °C under aerobic conditions to study the effects on N dynamics of Gliricidia (Gliricidia sepium, Jacquin) and FYM application to soil at 5 and 10 g kg⁻¹. Application of Gliricidia induced N mineralization from the start of incubation period, with the amount of N mineralized increasing with rate of application. In contrast, application of FYM resulted in immobilization of mineral N in soil, irrespective of the rate of application. The initial net immobilization from FYM was limited by availability of N in the soil for the higher rate of application.We used the APSIM SoilN module to simulate these contrasting patterns of mineralization of N from Gliricidia and from FYM. The prediction of N mineralized from Gliricidia was better than FYM. The default model parameters specify that the fresh organic matter pools (FPOOL1, FPOOL2 and FPOOL3) have the same C:N ratio and this assumption was ineffective in predicting N mineralized from FYM. The predictive ability of the model improved when this default assumption was modified based on the size of the individual pools (FPOOL1, FPOOL2 and FPOOL3), and the pool's C:N ratios. The modelling efficiency, a measure of goodness of fit between the simulated and observed data, improved markedly for the modified model. The discrepancy between the modelled and observed data was a tendency for the model to underestimate the rate of re-mineralization at the lower rate of application of FYM in the later part of incubation. Unfortunately the appropriate modification to the size and C:N ratios of the FPOOLs could not be determined on the basis of chemical analysis alone. Thus, a true predictive application of the model to a new FYM material is not yet possible.     

Four kinds of capping materials for controlling phosphorus and nitrogen release from contaminated sediment using a static simulation experiment

• Lanthanum modified bentonite (LMB) can effectively absorb phosphorus (P). • Water treatment plant sludge (WTPS) capping is effective for controlling P release. •Aluminum-based P-inactivation agent (Al-PIA) is an efficient P control material. •The P adsorbed by WTPS and Al-PIA is mainly in the form of NAIP. We determined the effects of quartz sand (QS), water treatment plant sludge (WTPS), aluminum-based P-inactivation agent (Al-PIA), and lanthanum-modified bentonite (LMB) thin-layer capping on controlling phosphorus and nitrogen release from the sediment, using a static simulation experiment. The sediment in the experiment was sampled from Yundang Lagoon (Xiamen, Fujian Province, China), which is a eutrophic waterbody. The total phosphorus (TP), ammonium nitrogen (NH₄⁺-N), and total organic carbon (TOC) levels in the overlying water were measured at regular intervals, and the changes of different P forms in WTPS, Al-PIA, and sediment of each system were analyzed before and after the test. The average TP reduction rates of LMB, Al-PIA, WTPS, and QS were 94.82, 92.14, 86.88, and 10.68%, respectively, when the release strength of sediment TP was 2.26–9.19 mg/(m²·d) and the capping strength of the materials was 2 kg/m². Thin-layer capping of LMB, WTPS, and Al-PIA could effectively control P release from the sediment (P<0.05). However, thin-layer capping of LMB, Al-PIA, and QS did not significantly reduce the release of ammonium N and organic matter (P > 0.05). Based on our results, LMB, Al-PIA, and WTPS thin-layer capping promoted the migration and transformation of easily released P in sediment. The P adsorbed by WTPS and Al-PIA mainly occurred in the form of NAIP.     

Semi-closed synthesis of nitrogen and oxygen Co-doped mesoporous carbon for selective aqueous oxidation

Heteroatom-doped meso/micro-porous carbon materials are conventionally produced by harsh carbonization under an inert atmosphere involving specific precursors, hard/soft templates, and heteroatom-containing agents. Herein, we report a facile synthesis of N and O co-doped meso/micro-porous carbon (NOMC) by template-free carbonization of a small-molecule precursor in a semi-closed system. The semi-closed carbonizaiton process yields hydrophilic NOMCs with large surface area in a high yield. The porous structure as well as the elemental composition of NOMCs can be modulated by changing the holding time at a particular temperature. NOMCs as metal-free heterogeneous catalysts can selectively oxidize benzyl alcohol and its derivatives into aldehydes/ketones with>85％conversion in aqueous solution, which is much higher than that of the control sample obtained in tube furnace (21％conversion), mainly due to their high N content, high percentage of pyridinic N, and large surface area. The presence of O-containing moieties also helps to improve the hydrophilicity and dispersion ability of catalysts and thus facilitates the mass transfer process during aqueous oxidation. The NOMC catalysts also dispayed excellent activity for a wide range of substrates with a selectivity of>99％.     

Analysis of the relationship between ambient levels of O3, NO2 and NO as a function of NOx in the UK

Monitoring data from the UK Automatic Urban and Rural Network are used to investigate the relationships between ambient levels of ozone (O₃), nitric oxide (NO) and nitrogen dioxide (NO₂) as a function of NO_x, for levels ranging from those typical of UK rural sites to those observed at polluted urban kerbside sites. Particular emphasis is placed on establishing how the level of ‘oxidant’, OX (taken to be the sum of O₃ and NO₂) varies with the level of NO_x, and therefore to gain some insight into the atmospheric sources of OX, particularly at polluted urban locations. The analyses indicate that the level of OX at a given location is made up of NO_x-independent and NO_x-dependent contributions. The former is effectively a regional contribution which equates to the regional background O₃ level, whereas the latter is effectively a local contribution which correlates with the level of primary pollution. The local oxidant source has probable contributions from (i) direct NO₂ emissions, (ii) the thermal reaction of NO with O₂ at high NO_x, and (iii) common-source emission of species which promote NO to NO₂ conversion. The final category may include nitrous acid (HONO), which appears to be emitted directly in vehicle exhaust, and is potentially photolysed to generate HO_x radicals on a short timescale throughout the year at southern UK latitudes. The analyses also show that the local oxidant source has significant site-to-site variations, and possible reasons for these variations are discussed. Relationships between OX and NO_x, based on annual mean data, and fitted functions describing the relative contributions to OX made by NO₂ and O₃, are used to define expressions which describe the likely variation of annual mean NO₂ as a function of NO_x at 14 urban and suburban sites, and which can take account of possible changes in the regional background of O₃.