Denitrification-nitrification process in permeable coastal sediments: An investigation on the effect of salinity and nitrate availability using flow-through reactors

Permeable coastal sediments act as a reactive node in the littoral zone,transforming nutrients via a wide range of biogeochemical reactions.Reaction rates are controlled by abiotic factors,e.g.,salinity,temperature or solute concentration.Here,a series of incubation experiments,using flow-through reactors,were conducted to simulate the biogeochemical cycling of nitrate (NO_3~?) and phosphorus (P) in permeable sediments under differentNO_3~?availability conditions (factor I) along a salinity gradient (admixture of river and seawater,factor II).In an oligotrophic scenario,i.e.,unamendedNO_3~?concentrations in both river and seawater,sediments acted as a permanent net source ofNO_3~?to the water column.The peak production rate occurred at an intermediate salinity(20).IncreasingNO_3~?availability in river water significantly enhanced netNO_3~?removal rates within the salinity range of 0 to 30,likely via the denitrification pathway based on the sediment microbiota composition.In this scenario,the most active removal was obtained at salinity of 10.When both river and seawater were spiked with NO_3~?,the highest removal rate switched to the highest salinity (36).It suggests the salinity preference of theNO_3~?removal pathway by local denitrifiers (e.g.,Bacillus and Paracoccus) and thatNO_3~?removal in coastal sediments can be significantly constrained by the dilution relatedNO_3~?availability.Compared with the obtained variation forNO_3~?reactions,permeable sediments acted as a sink of soluble reactive P in all treatments,regardless of salinity andNO_3~?input concentrations,indicating a possibility of P-deficiency for coastal water from the intensive cycling in permeable sediments.Furthermore,the net production of dissolved organic carbon (DOC) in all treatments was positively correlated with the measuredNO_3~?reaction rates,indicating that the DOC supply may not be the key factor forNO_3~?removal rates due to the consumption by intensive aerobic respiration.Considering the intensive production of recalcitrant carbon solutes,the active denitrification was assumed to be supported by sedimentary organic matter.     

饮用水NO-3污染与食管癌发病率及死亡率相关性探讨--以河南省林州安阳地区为例

阐明了林州市食管癌流行的4个特征。根据46个饮用水的NO3^-分析资料，论证亚硝胺的前体物NO3^-的分布与食管癌的地理分布具有明显的相关性：林州市的发病率是北部高于南部；林州市－安阳县－范县的发病率是西部大于东部。居民饮用NO3^-超标的浅层地下水，旱井水是导致食管癌的重要原因之一。70年代以来，大量施用化肥是引起饮用地下水NO3^-污染的根本原因，它导致的后果是林州市食管癌发病率和死亡率下降缓慢。指出了必须坚持“防霉、去胺、施钼肥、治增生、改变不良饮食习惯”五项预防措施，特别要把饮用水治理好。     

非点源污染研究中土壤溶解性无机氮的提取方法选择

用2M KCl溶液(5:1)、饱和CaSO4溶液(5:1)、0.01M CaCl₂溶液(20:1,100:1) 和去离子水(20:1,100:1)4种提取液、6种提取方式,采用Auto-analyzerⅢColorimeter (Bran Luebbe),水杨酸-次氯酸盐法和Griess-Ilosvay法测定并对比了北京地区4种天然土样的溶解性氨氮和硝态氮的含量。研究结果表明:溶解性硝态氮的测定结果不受提取液和水土比(小于100:1)的影响,而溶解性氨氮测定结果受影响较大。在非点源污染研究中,对于土壤中可向水体迁移的溶解性无机氮含量的测定,应根据来水水源特征和研究目的选择适宜的浸提剂和水土比。     

一氧化氮和过氧化氢对万寿菊不定根形成的影响

以万寿菊（Tagetes erecta L.）为试材,研究了一氧化氮（NO）和过氧化氢（H2O2）对植物不定根形成中的影响及其相互关系。结果表明,外源NO供体肖普纳（SNP）和H2O2可显著地促进万寿菊外植体不定根的形成,且呈现明显的剂量效应,最适的SNP和H2O2浓度分别为50 μM和200 μM。NO和H2O2共同处理的万寿菊不定根的数量和根长显著高于NO或H2O2单独处理。NO在H2O2诱导万寿菊不定根形成的信号途径中起了重要作用;同时,H2O2包含在NO诱导不定根形成途径中。NO引起万寿菊外植体内源H2O2含量增加,H2O2亦促进内源NO积累。可见,NO和H2O2在万寿菊不定根形成过程中具有协同诱导效应,两者在促进不定根形成过程中可能通过互作反应提高各自的信号水平。     

The boundary layer characteristics in the heavy fog formation process over Beijing and its adjacent areas

By utilizing the Atmospheric Boundary Layer (ABL) observational data made available from the project "973" under the auspices of the Ministry of Science and Technology of the People's Republic of China - entitled the Beijing City Air Pollution Observation Field Experiment (BECAPEX), including the measurements by a wind profiler, captive airships, tower-based boundary layer wind and temperature gradient observational instruments (ultrasonic anemometers and electronic thermometers), air composition samplers, conventional upper-air, surface and Automatic Weather Stations (AWS) observations, this paper herewith analyzes, in a comprehensive manner, the occurrence of a heavy fog event over Beijing in February 2001, including its formation, development, persistence, dynamic and thermodynamic features as well as evolving stratification structures within the boundary layer at different stages. The results suggested: (i) as a typical case of urban heavy fog, before the fog onset over Beijing, a temperature inversion existed in the lower atmosphere, the smokes and the pollutants like SO2 and NO2 had been accumulated at a lower level. Proceeding the fog event, with the increase of SO2 and NO2 concentrations, condensability increased sharply. On the contrary, during the fog process, with increasing condensability, SO2 and NO2 concentrations decreased. This indicated that, acting as condensation nucleus, these accumulated pollutants were playing a key role in catalyzing the fog condensation. (ii) By analyzing mean gradient-, pulsation- and turbulence-distribution patterns derived from the wind measurements taken by the aforementioned tower-based instruments, they all indicated that about 10 hours before the fog onset, a signal foretelling potential strong disturbances in the lower boundary layer was detected, and a significant rise of both mean and disturbance kinetic energies was observed, revealing that the low-level wind shear was strengthened before the fog onset, consequently creating a favorable condition for the outbreak of turbulences. This strong signal seemed to be very meaningful in monitoring and predicting fog occurrence and its development. (iii) Once the fog was in shape, its condensation feedback effects tended to lift the height of temperature inversion layer within the mid and upper levels of the lower atmosphere, which in return determined the fog persistence and restructuring process.     

Mutual effects of nitric oxide and iron on the growth of marine algae

Experiments on the effects of nitric oxide （NO） and iron on the growth of marine microalgae Skeletonema costatum were conducted. The results are as follows： exogenous NO could increase the growth rate of marine algae and raise the biomass remarkably under iron-deficient conditions. But it was a complicated process that the phytoplankton growth was influenced by NO and iron, which was controlled by the NO concentration, the nutrition level of the culture medium and the iron concentration, etc. Meanwhile, the iron concentration in the medium also has a direct influence on the growth and NO release capacity of the algae. Therefore, the effects of NO and iron on the growth of marine phytoplankton were mutual.     

南宁市空气质量状况特征研究

通过对南宁市 5个空气质量观测站可吸入颗粒物、二氧化硫、二氧化氮的观测资料进行分析 ,发现 :南宁市首要污染物为可吸入颗粒物 ,5个观测站可吸入颗粒物具有很好的变化趋势一致性 ,二氧化硫变化趋势一致性较差 ,二氧化氮基本没有变化     

南海东北部沉积物间隙水氮和硅的研究

测定了南海东北部沉积物间隙水中ＮＯ３－Ｎ，ＮＯ２－Ｎ和ＳｉＯ３－Ｓｉ的含量。６个站位的５─１０ｃｍ层的ＮＯ３－Ｎ，ＮＯ２－Ｎ和ＳｉＯ３－Ｓｉ的含量分别为０．４７—１．７０，０．８４—２．６０和１０．１７—１１．６９μｍｏｌ／Ｌ。研究了上述物质含量在５０号站的深度分布。估算了ＮＯ２－Ｎ和ＳｉＯ３－Ｓｉ从间隙水向上覆水扩散的通量分别为０．０３３和０．０１９ｍｍｏｌ／ｍ２·ｄ。     

南极冰盖NO－3浓度记录研究进展

综述了近年来南极冰盖雪冰中NO－ 3浓度的影响因素、NO－ 3的来源、沉积后变化及其浓度的时空变化特征的最新研究进展。尽管质子事件、超新星活动、陨石事件、火山喷发和核试验等各种突发事件都可能对南极雪冰中NO－ 3浓度产生影响,但综述和模拟结果表明中低纬度对流层闪电和极地平流层来源可能是南极雪冰中NO－ 3浓度本底的主要来源。综合研究表明,南极冰盖雪冰中记录的NO－ 3浓度可能是其来源、传输路径、沉积过程以及沉积后变化等的综合反映。     

The effect of nitric oxide on the growth of marine phytoplankton

The incubation experiments of Skeletonema costatum, Dicrateria zhanjiangensis nov. sp., and Platymonas sub-cordiformis, and those of Emiliania huxleyi were carried out in the Marine Physical Chemistry Laboratory in Ocean University of China and in the Marine Organic Geochemistry Laboratory in the University of Georgia respectively. Nitric oxide was added into the media when these marine microalgae were growing. We found the growth of these four microalgae were promoted or inhibited when nitric oxide of different concentrations was added one or two times each day during the cultivation process. The results are consistent with the influence of nitric oxide on the growth of high plants. The results show that nitric oxide may be a new factor of regulation and control for the phytoplankton growth in seawater.