渤海南部海域柱状沉积物中氮的形态与有机碳的分解

海洋沉积物中氮形态的研究是研究其生物地球化学循环的重要前提,柱状沉积物中氮的形态分布在一定程度上反映了其早期成岩作用的进程及结果.利用分级浸取分离方法首次对渤海南部海域自然粒度下5个柱状沉积物样品进行了分析,依据是否可由试剂提取将其分为可转化态和非转化态,系统地研究了可转化态中各形态氮的分布特征及早期成岩作用.研究表明,渤海南部海域自然粒度下柱状沉积物中,OSF-N和IEF-N是可转化态氮的优势形态.各形态氮的含量随深度变化趋势不同,成岩作用亦不同.沉积物中有机氮的分解速率常数为15.51×10-3a,且对各生源要素的分解速率常数有N>P>C>Si;OC/TN比值远小于OC/ON,说明沉积物中保留了大量无机氮(IN)和非转化的有机氮,OC/ON值随深度增加而减小是由于沉积物中富集了ON;柱状沉积物中,表层比深层可转化态氮占其总量的比例高,在局部区域由于深层沉积物中氮的“再活化”导致二者几乎相同.     

近海沉积物中氮磷的生物地球化学研究进展

通过对国内外学者十几年来在近海沉积物氮磷地球化学方面研究工作的综述，阐明了该方面的最新进展。主要包括：沉积物中氮磷的形态及分布特点，各种形态间的分配关系，以及与氮磷迁移转化相关的循环过程。最后对该领域今后的发展方向进行展望。     

条斑紫菜单细胞固体培养的初步研究

成熟条斑紫菜叶状体酶解后获得单细胞,分别培养于添加了不同浓度N,P营养盐的0．5％和10％的琼胶培养基上,观察细胞的分化发育情况。结果显示：(1)营养细胞大部分先发育为细胞团,细胞团放散孢子,再由孢子萌发形成小苗。其余营养细胞极性分裂形成正常细胞苗或带假根的形状不规则的片状体。孢子茁和营养细胞直接形成的幼苗生长到一定大小均可放散单孢子,单孢予能够正常萌发形成单孢子苗。(2)在0．5％的琼胶培养基上或较高浓度的营养盐中,细胞发育快。添加5mg／L NO3-N和0．5mg／L H2PO4—P营养盐不能满足细胞生长发育的需要,培育20d绝大部分仍为单细胞,不能形成正常幼苗。     

Quantifying nitrogen cycling beneath a meander of a low gradient,N‐impacted,agricultural stream using tracers and numerical modelling

In watersheds impacted by nitrate from agricultural fertilizers, nitrification and denitrification may be decoupled as denitrification in the hyporheic zone is not limited to naturally produced nitrate. While most hyporheic research focuses on the 1–2 m of sediment beneath the stream bed, there are a limited number of studies that quantify nitrogen (N) cycling at larger hyporheic scales (10s of metres to kms). We conducted an investigation to quantify N cycling through a single meander of a low gradient, meandering stream, draining an agricultural watershed. Chemistry (major ions and N species) and hydrologic data were collected from the stream and groundwater beneath the meander. Evidence indicates that nearly all the shallow groundwater flowing beneath the meander originates as stream water on the upgradient side of the meander, and returns to the stream on the downgradient side. We quantified the flux of water beneath the meander using a numerical model. The flux of N into and out of the meander was quantified by multiplying the concentration of the important N species (nitrate, ammonium, dissolved organic nitrogen (DON)) by the modelled water fluxes. The flux of N into the meander is dominated by nitrate, and the flux of N out of the meander is dominated by ammonium and DON. While stream nitrate varied seasonally, ammonium and DON beneath the meander were relatively constant throughout the year. When stream nitrate concentrations are high (>2 mg litre^?1), flow beneath the meander is a net sink for N as more N from nitrate in stream water is consumed than is produced as ammonium and DON. When stream nitrate concentrations are low (<2 mg litre^?1), the flux of N entering is less than exiting the meander. On an annual basis, the meander hyporheic flow serves as a net sink for N. Copyright © 2007 John Wiley & Sons, Ltd.     

离子色谱法测定地下水中有机氮

本文探讨了K_2S_2O_8氧化离子色谱法测定有机氮的实验条件,考察了淋洗剂离子价态及淋洗剂总离子强度对低浓度NO_3~-与高浓度SO_4~2-分离的影响;测定了11种含氮有机化台物有机氮的回收率。本法测定地下水中有机氮的结果与经典蒸馏法结果较为一致,具有操作简便、快速、准确,效率高的特点。     

Using an inverse modelling approach with equifinality control to investigate the dominant controls on snowmelt nutrient export

There is great interest in modelling the export of nitrogen (N) and phosphorus (P) from agricultural fields because of ongoing challenges of eutrophication. However, the use of existing hydrochemistry models can be problematic in cold regions because models frequently employ incomplete or conceptually incorrect representations of the dominant cold regions hydrological processes and are overparameterized, often with insufficient data for validation. Here, a process‐based N model, WINTRA, which is coupled to a physically based cold regions hydrological model, was expanded to simulate P and account for overwinter soil nutrient biochemical cycling. An inverse modelling approach, using this model with consideration of parameter equifinality, was applied to an intensively monitored agricultural basin in Manitoba, Canada, to help identify the main climate, soil, and anthropogenic controls on nutrient export. Consistent with observations, the model results suggest that snow water equivalent, melt rate, snow cover depletion rate, and contributing area for run‐off generation determine the opportunity time and surface area for run‐off–soil interaction. These physical controls have not been addressed in existing models. Results also show that the time lag between the start of snowmelt and the arrival of peak nutrient concentration in run‐off increased with decreasing antecedent soil moisture content, highlighting potential implications of frozen soils on run‐off processes and hydrochemistry. The simulations showed TDP concentration peaks generally arriving earlier than NO₃ but also decreasing faster afterwards, which suggests a significant contribution of plant residue Total dissolved Phosphorus (TDP) to early snowmelt run‐off. Antecedent fall tillage and fertilizer application increased TDP concentrations in spring snowmelt run‐off but did not consistently affect NO₃ run‐off. In this case, the antecedent soil moisture content seemed to have had a dominant effect on overwinter soil N biogeochemical processes such as mineralization, which are often ignored in models. This work demonstrates both the need for better representation of cold regions processes in hydrochemical models and the model improvements that are possible if these are included.     

胶州湾沉积物中氮的地球化学特征及其环境意义*

通过分级浸取的方法获得了胶州湾沉积物中不同形态的氮,将可转化态氮分为离子交换态(IEF-N)、弱酸浸取态 (WAEF-N)、强碱浸取态(SAEF-N)和强氧化剂浸取态(SOEF-N),讨论了其地球化学特征和控制因素,并结合²¹⁰ Pb测年计算了不同年代氮的埋藏通量。在此基础上,分析了胶州湾沉积物中氮给出的环境信息。结果表明,强氧化剂浸取态氮是胶州湾沉积物中可转化态氮主要赋存形态,NO₃-N是胶州湾沉积物中氮的优势形态,氮的含量及埋藏通量的分布受到pH、盐度、温度、生物扰动、沉积物粒度、沉积速率等多种因素的影响。受人为活动的影响,目前每年排入胶州湾的固体垃圾和污水中的悬浮颗粒物的量已超过河流来沙,成为胶州湾主要的沉积物来源。在20世纪初由于污染情况较轻,并且受人为活动的影响较小,胶州湾沉积物各形态氮的埋藏通量较低,但自从20世纪80年代开始,环胶州湾地区的工农业迅猛发展,氮的埋藏通量急剧增加,胶州湾地区的环境一度恶化,但由于近年来采取的较为得力的治污与排放措施,胶州湾的环境状况已有明显改观。     

小城镇街道灰尘中氮磷含量研究

以上海市的枫泾镇(FJ)、松江新城(SJ)和朱家角镇(ZJJ)为例,研究了小城镇街道灰尘中氮磷的含量水平和分布特征,结果表明:小城镇街道灰尘中总无机氮的含量为11.9-1040.6μg/g,平均含量为117.5.μg/g;可溶磷的含量为15.8～65.8μg/g,平均含量为48.7μg/g;各小城镇街道灰尘中的氮磷含量表现为:FJ＞ZJJ＞SJ.各小城镇街道灰尘中氮磷含量的空同分布差异较大,位于城镇中心和风景区内采样点的氮磷含量明显较高,而城镇周边乡村地区含量较低.对各小城镇街道灰尘氮磷含量的季节变化分析表明,秋季小城镇街道灰尘中氮磷的含量明显高于冬季和夏季,温度、降雨量可能是其季节变化的主要影响因子.     

东山湖水体无机氮年际变化及其来源分析

总结了城市湖泊总无机N及各无机氮素的年际变化和不同水期的年际变化，结果表明：总无机N年际变化呈波浪式；不同水期中，总无机N与NH4^＋-N以枯水期为最丰，而NO3^--N及NO2^-N则以平水期为相对最丰。同时分析了水体无机氮素的来源，结果显示汛期水流中营养物的滞留及底泥含氮成分的释放是湖泊水体无机氮素的主要来源，并计算了滞留系数及内源性负荷，分别为0．507、10．3％。此外，拟合分析了水体无机氮素间的关系，总无机N与NH4^＋-N有明显正相关关系，相关系数达0．997。     

非对称天然沸石陶瓷膜的制备及其性能表征

利用天然沸石为主要原料,制备出具有过滤功能和重金属离子吸附功能的天然沸石非对称陶瓷膜。非对称膜中支撑体、中间层膜和顶层膜的平均孔径分别为6.6μm、0.6μm和0.1μm。非对称膜单位压力降(1 MPa)下的氮气通量和水通量分别为:24.69×103m3/(m2h)和1.87×103m3/(m2h);对重金属离子(铅离子)吸附交换能力为7.13 mg/g。