δ13C和δ15N指示不同生态类型湖泊无机氮及有机质来源

为了探讨不同生态类型湖泊(天然湖泊、城市湖泊)中无机氮和有机质来源,分别采集湖泊中水体、表层沉积物、水生植物、底栖动物进行碳、氮同位素特征分析.结果表明:蚌湖水体δ15N-NH4均值为-1.8‰±1.0‰,δ15N-NO3-均值为-0.5‰±1.7‰,说明蚌湖水体氮表现为雨水和农业肥料氮污染;象湖δ15 N-NH4+均值为6.8‰±8.6‰,其中养殖废水和管道排污口δ15N-NH4+值分别为13.5‰和25.4‰,表现出污水氮同位素特征,象湖δ15 N-NO3-均值为-2.9‰±4.2‰,是氨的硝化作用引起的氮同位素分馏所致.蚌湖表层沉积物、水生植物δ15N差别不大,分别为6.6‰±0.3‰、7.1‰±0.7‰,水生植物δ13C均值为-27.5‰±0.3‰,比沉积物δ13C偏负3‰.有机C/N为9.4±0.5,比沉积物C/N明显偏高6,反映水生植物是蚌湖有机质的主要来源.象湖表层沉积物δ15N、δ13C及有机C/N分布范围大,δ15N在3.6‰～8.3‰之间,均值为5.9‰±1.6‰,δ13C在-27.1‰～-24.7‰之间,均值为-26.0‰±1.0‰,有机C/N在2.6 ～10.8之间,均值为6.2±2.7,表明城市湖泊沉积有机质来源复杂.2个湖泊蚌类δ15N组成与各自湖泊表层沉积物δ15N组成相对应.     

南京气溶胶水溶性离子粒径分布及其随高度的变化

2009年1月对南京市河西生活区距地面1．5、54和80m3处同步进行了大气颗粒物采样,并用离子色谱对样品进行了分析。结果显示,随着高度的增加,PM10和PM2.1的质量浓度逐渐降低,而总离子浓度随高度增加而增大。气溶胶中最主要的3种水溶性离子分别为N03、SO4 2-、Ca2＋,且3个高度的NO3-与SO4 2-浓度之比均大于1,表明该生活区移动排放源已经成为大气气溶胶离子的主要来源。3个高度处各离子粒径分布规律为：SO4 2-、NO3-、K＋在0．43-1．1um出现峰值;Ca2＋、Mg2＋、NO2-在4．7～5．8um出现峰值;Na＋、Cl-、F-在0．43～1．1um和4．7～5．8um出现双峰。     

一次大雾天气下PM2.5二次无机粒子的数值模拟

利用多尺度空气质量模式系统（Models-3/CMAQ）对2002年12月1—3日北京及周边地区发生的一次大雾天气进行数值模拟,分析了大雾天气下PM2.5二次无机粒子的演变及其影响。结果表明,白天相对湿度降低,雾滴蒸发脱水后PM2.5二次无机粒子会悬浮在大气中;夜间在水汽凝结成雾滴的过程中,大量的PM2.5二次无机粒子提供了充足的凝结核,促进大雾天气的进一步发展。午后PM2.5二次无机粒子积聚及较高的相对湿度是造成北京及周边地区低能见度的重要原因,并推断该区域很可能是霾天气。     

光谱法测定海水中溶解态无机氮的研究进展

溶解态无机氮(dissolved inorganic nitrogen,DIN)主要由亚硝酸盐-氮(NO^-₂-N)、硝酸盐-氮(NO^-₃-N)和铵氮(NH⁺₄-N)组成,它们在海洋的生物地球化学循环过程中起重要作用。但人类活动向海洋输入了大量无机氮,导致一系列环境问题。为了更好地开展海洋氮循环研究和环境污染管理,需对海水中的DIN进行测定。在众多分析方法中,光谱法因其通用性好、适用范围广、所需设备简单,成为测定海水DIN的首选。本文总结了近10年来基于光谱法测定海水DIN的研究进展,包括紫外分光光度法测定NO^-₃-N、萘乙二胺分光光度法测定NO^-₂-N和NO^-₃-N、次溴酸盐氧化-分光光度法测定NH⁺₄-N、靛酚蓝分光光度法测定NH⁺₄-N...     

长江口及杭州湾邻近海域夏季表层海水中的溶解无机碳

根据2004年8月在长江口、杭州湾附近海域获得的调查资料对表层水中Ph值、总碱度和溶解无机碳的分布特征及其与环境参数的关系进行了研究,并由此得到了溶解无机碳的组成情况.结果表明,HCO3-、CO23-;和CO2(T)占溶解无机碳浓度百分比分别为80.33%～97.75%、0.61%～19.42%和0.25%～2.34%,平均值分别为(93.28±3.68)%、(5.58±4.03)%和(1.14±0.43)%.水文、浮游植物等对各参数的分布具有重要影响,但对不同参数的影响程度不同.     

Alkalinity and dissolved inorganic carbon exports from tropical and subtropical river catchments discharging to the Great Barrier Reef,Australia

Dissolved inorganic carbon (DIC) transport by rivers is an important control on the pH and carbonate chemistry of the coastal ocean. Here, we combine DIC and total alkalinity (TAlk) concentrations from four tropical rivers of the Great Barrier Reef region in Australia with daily river discharge to quantify annual river loads and export rates. DIC in the four rivers ranged from 284 to 2,639 μmol kg⁻¹ and TAlk ranged from 220 to 2,612 μmol kg⁻¹. DIC:TAlk ratios were mostly greater than one suggesting elevated exports of free [CO₂*]. This was pronounced in the Johnstone and Herbert rivers of the tropical wet north. The largest annual loads were transported in the two large river catchments of the southern Great Barrier Reef region, the Fitzroy and Burdekin rivers. The carbon stable isotopic composition of DIC suggests that carbonate weathering was the dominant source of DIC in the southern rivers, and silicate weathering was likely a source of DIC in the northern Wet Tropics rivers. Annual loads and export rates were strongly driven by precipitation and discharge patterns, the occurrence of tropical cyclones, and associated flooding events, as well as distinct seasonal dry and wet periods. As such, short-lived hydrological events and long-term (seasonal and inter-annual) variation of DIC and TAlk that are pronounced in rivers of the tropical and subtropical wet and dry climate zone should be accounted for when assessing inorganic carbon loads to the coastal ocean and the potential to buffer against or accelerate ocean acidification.     

轻型无机基质新材料设计施工应用案例分析

种植屋面用轻型无机基质按用途分为:营养基质和蓄排水基质,这种基质具有轻量、洁净、排水通透、保水保肥、施工简便、等优良特性。另外,定量设计的阳离子交换能力(CEC)使其能有效控制树木的快速生长,缓解荷重增加与建筑荷载之间的矛盾。     

Origin of methane in high-arsenic groundwater of Taiwan – Evidence from stable isotope analyses and radiocarbon dating

Groundwaters in the confined aquifers of the Chianan and Ilan coastal plains of Taiwan are rich in dissolved methane (CH₄). Serious endemic “blackfoot disease”, which occurred in the Chianan plain, especially during AD1950-1970, has been demonstrated to have arisen from drinking highly reducing groundwater with abnormal arsenic and humic substance levels. In order to explore the origin of CH₄ and its hydrological implications, stable carbon isotope ratios (δ¹³C) and radiocarbon (¹⁴C) ages of exsolved CH₄, dissolved inorganic carbon (DIC), and sedimentary biogenic sediments from a total of 34 newly completed water wells at 16 sites were determined. The main results obtained are as follows: (1) The δ¹³C_CH4 (−65‰ to −75‰) values indicate that, except for one thermogenic sample (δ¹³C_CH4=38.2‰) from the Ilan plain, all CH₄ samples analyzed were produced via microbially mediated CO₂ reduction. Many δ¹³C_DIC values are considerably greater than −10‰ and even up to 10‰ due to Rayleigh enrichment during CO₂ reduction. (2) Almost all the ¹⁴C ages of CH₄ samples from the shallow aquifer (I) (<60 m depth) are greater than the ¹⁴C ages of coexisting DIC and sediments, suggesting the presence of CH₄ from underlying aquifers. (3) The ¹⁴C ages of coexisting CH₄, DIC and sediments from aquifer (II) of the Chianan plain are essentially equal, reflecting in-situ generation of CH₄ and DIC from decomposition of sedimentary organic matter and sluggishness of the groundwater flow. On the other hand, both CH₄ and DIC from each individual well of the relatively deep aquifers (III) and (IV) in the Chianan plain are remarkably younger than the deposition of their coexisting sediments, indicating that current groundwaters entered these two aquifers much later than the deposition of aquifer sediments. (4) Each CH₄ sample collected from the Ilan plain is older than coexisting DIC, which in turn is distinctly older than the deposition of respective aquifer sediments, demonstrating the presence of much older CO₂ and CH₄ from underlying strata.     

单生卵囊藻对DIC的利用及其对CaCO3沉积影响的研究

以生长在钙华池中的单生卵囊藻（Oocystis solitaria Wittr）为研究对象,利用pH漂移方法,探讨了封闭系统中单生卵囊藻在岩溶水和非岩溶水环境下对溶解无机碳（DIC）利用及其对水体Ca^2＋沉积影响的差异。结果表明,单生卵囊藻在低CO2浓度时,通过胞外碳酸酐酶的催化,以HCO3^-作为无机碳源进行光合作用。在岩溶水环境下单生卵囊藻DIC利用能力要高于非岩溶水环境（4．78倍）,而在此过程中对水体中Ca^2＋沉积的影响也更高（2．13倍）。在岩溶水（非岩溶水）环境下,有42．6％（8．9％）的Ca^2＋通过物理化学效应以CaCO3形式沉积,其余Ca^2＋可能被藻体生长而吸收利用．．     

Total Solar Irradiance Measurement and Modelling during Cycle 23

During solar cycle 23, which is now close to its end, variations of the total solar irradiance were measured by six different instruments, providing four independent time series of the irradiance variation over the complete solar cycle. A new composite time series constructed using five of these six instruments provides unprecedented instrument stability for the study of the open question of solar irradiance variations between minima. An independent analysis of the different composite time series is performed through an empirical proxy model fit. The new composite is fitted with 0.96 correlation (R ²=93%) and RMS error of 0.15 W m⁻², thus reaching the limit of the individual instrument stabilities. Both the measurements and the model indicate that for the current cycle the minimum irradiance level has not yet been reached. Therefore we use the model to extrapolate measurements up to 2008 when the minimum irradiance level is expected. If we assume that there will be no changes in the solar irradiance from 2006 to 2008 that are not captured by the regression model, it can be predicted that there will be no variation of the solar minimum irradiance level during cycle 23 with an uncertainty of ±0.14 W m⁻².