汉江上游金水河悬浮物及水体碳氮稳定同位素组成特征

金水河位于南水北调中线工程水源地的汉江上游,研究其污染物来源及分布规律对水源地水资源保护尤为重要。研究了不同水文季节金水河中悬浮颗粒物C和N稳定同位素值、水体硝酸盐与铵盐含量及其N稳定同位素特征。结果表明:金水河流域可溶性氮素与悬浮颗粒物的来源具有明显的空间性和季节性差异,并且流域内叶绿素浓度、水体浊度、悬浮物浓度都会对河流碳氮素稳定同位素值造成影响,主要体现在环境因子的变化制约着水体中硝化和反硝化生物对氮素的可利用性。结果显示:1)水体中悬浮颗粒物的碳稳定同位素为-8.03‰-14.57‰,平均值为2.59‰;氮稳定同位素范围为-7.50‰-7.34‰,平均值为:4.33‰,表明悬浮颗粒物的来源主要为外源性土壤有机质与内源性水生植物残体的混合;2)河流水体中铵盐与硝酸盐N-稳定同位素范围分别为-5.86‰-17.20‰,平均值为5.02‰及-1.48‰-15.86‰,平均值为5.75‰;水体可溶性氮素主要来源为大气沉降、河流水生生物以及地表径流所带入的化肥农药等;3)悬浮颗粒物含量不仅随着河流径流量的季节性变化而变化,还随着人为干扰强度的加强而呈递增的趋势,水体悬浮颗粒物含量最高达到(9.883±3.45)mg/L。而NH_4~+及NO_3~-的浓度也呈现出相同的趋势,含量分别为0.07-0.45 mg/L,平均值为0.25 mg/L;0.08-0.44 mg/L,平均值为0.37 mg/L。稳定同位素测定为河流生态系统提供了一个整合时空氮素来源和转移循环过程的综合指标,揭示了环境因子对河流生态系统氮循环的影响过程与机制。     

太湖五里湖富营养化的碳同位素记录

通过太湖五里湖表层沉积物柱样中总有机碳、总氮、总磷的变化,探讨了五里湖营养盐磷输入的历史记录,结合总有机碳碳同位素的分析,揭示了该湖富营养化和初级生产力的演化过程.总有机碳碳同位素值为-27.0‰～-26.3‰,平均-26,6‰,从底部向上波动变化,在深度12 cm处最大,然后向上逐渐减小,5 cm处降至最小,随之向上逐渐增大,反映了随着人为活动强度的加大,该湖水体富营养化程度逐渐加剧的特点,并且总有机碳碳同位素与有机碳、氮原子比值记录了湖泊水生植物群落由水草为主-草藻结合-藻类为主的演替过程.

Abstract：

Through the analysis of total organic carbon, total nitrogen, and total phosphorus con-centrations in surface sediment cores from Wuli Bay of Taihu Lake, the historical record of phos-phate input in the Bay was studied, and in combining with the analysis of carbon isotope value of bulk sedimentary organic matter, the evolution process of the primary productivity and eutrophi-cation in the Bay was revealed. The carbon isotope value of the sediment total organic C was -26. 6‰ on average, with a variation between-27.0‰ and-26. 3‰. It was decreased with depth up to the lowest value at 5 cm, subsequently increased gradually up to the highest value at 12 cm, and then fluctuated downward with the depth, which suggested that the evolvement of eu-trophication, productivity, and primary producer was associated with the increasing phosphorus input from human activities. Moreover, the concentrations of total phosphorus and the C/N atom-ic ratios of total organic carbon to total nitrogen recorded the succession process of aquatic plant community from float grass to float grass + algae to algae.     

生态转换系统中土壤有机质变化的稳定碳同位素示踪研究进展

由于气候变异、人类活动等因素影响 ,全球各生态系统间短期内正经历着前所未有的区域性转变 ,由此导致的一系列生态环境问题如区域气候变迁、荒漠化、水土流失等广受关注[2 ] ,而其中土壤有机质的变化起着极为关键的作用。据估计 ,地表土壤层中有机碳的总量为大气的 2～ 4倍 ,土壤有机质的变化对大气ＣＯ2 浓度的影响甚大[15] ;同时 ,土壤有机质又是维护土壤结构 ,保持土壤肥力的重要组成部分。因此 ,生态系统的转变对土壤有机质产生的影响为各国科学家所重视。尽管稳定碳同位素是示踪有机质变化过程最有效的手段之一 ,并且Ｎｉｓ ｓｅｎｂ…     

太湖沉积物有机碳与氮的来源

选取太湖梅梁湾和湖心柱状沉积物,研究了其有机碳同位素（δ13C）和氮同位素（δ15N）、C/N、总有机碳(TOC)、总氮(TN)、总磷（TP）含量,并结合210Pb和137Cs沉积物年代测定技术,探究了近百年太湖沉积物有机质和氮的来源。结果表明：太湖梅梁湾湖区在近百年来,其有机质来源总体以自生为主。50年代以前,湖区受到人类活动的影响较小,沉积物有机质主要来自于湖泊自身水生植物的沉积;50年代到70年代,湖泊内部环境发生变化,湖区逐渐出现藻类大量死亡并沉积的现象,有机质主要来自于水生植物和藻类的共同沉积;70年代到80年代沉积物机质藻类贡献进一步增大;90年代后到现在,则以藻类的沉积为主要来源方式。梅梁湾湖区沉积物氮素的来源在50年代以前主要以流域土壤流失和大型水生植物的死亡为主;50年代到70年代,人类活动的加剧导致大量工业废水、生活污水的输入,藻类开始大面积爆发,氮主要来自于外源的输入、大型植物和藻类的死亡沉积;90年代后到现在,外源氮的输入得到有效地控制,藻类对沉积物氮的贡献相对显著。湖心区域沉积物有机质和氮的来源主要来自于湖泊内部水生植物的沉积。70年代前,沉积物有机质和氮的来源主要来自于水生植物的沉积和水土流失作用;70年代至今,虽然湖泊受到人类活动外源物质输入影响逐渐增大,但总体来讲贡献较小,沉积物有机质和氮的来源仍以湖泊自生为主。     

碳稳定同位素技术在植物水分胁迫研究中的应用

植物体的碳稳定同位素组成主要由植物本身的生物学特性决定 ,但环境胁迫对其影响也十分明显。综述了碳稳定同位素技术在研究植物水分利用效率、生物量高低及判断历史气候依据等研究领域的进展 ,阐明了植物体的 δ1 3C值对干旱、盐分及其它环境因素的变化所引起的水分胁迫的响应 ,并对碳稳定同位素对水分胁迫的响应机理进行了归纳和推断     

基于稳定碳同位素分析宁夏典型林分土壤有机碳分布格局及影响因素

选择宁夏自北向南方向的贺兰山、罗山和六盘山(3座山的降水量呈现逐渐增加的趋势)共有的青海云杉林和油松林土壤作为研究对象,分析两种针叶林土壤有机碳特征[土壤有机碳(SOC)含量、稳定碳同位素组成(δ13C)和有机碳分解速率(β值)]的变化情况,并采用冗余分析法分析土壤化学指标对土壤有机碳特征的影响作用,探究干旱半干旱区土...     

2010年夏季珠江口海域颗粒有机碳的分布特征及其来源

于2010年8月对珠江口海域20个站位的颗粒有机碳(POC)进行采样,分析了POC的空间分布特征,讨论了POC与环境因子之间的关系,并利用碳稳定同位素(δ13C)分析了POC的来源及其贡献率。结果显示,研究区域POC的浓度范围98.5—1929.8μg/L,平均浓度541.9μg/L,空间分布总体呈现自北部海域向中部海域逐渐降低,中部海域至南部海域又逐渐升高,底层大于表层的特点。总悬浮颗粒物、叶绿素a、水动力是影响POC空间分布的重要原因。研究区域总悬浮颗粒物δ13C值的变化范围-27.05‰—-21.03‰,平均为-24.57‰,反映出珠江口海域颗粒有机碳为陆源和水生源混合来源,其分布呈现沿盐度梯度自口门内向口门外逐渐递增,底层高于表层的特点。陆源输入和海洋生物生产是影响δ13C值分布的主要原因。运用二元混合模型计算得知,珠江口北部和中部海域POC以陆源有机碳为主,贡献率平均为64%;南部海域POC以水生源有机碳为主,贡献率平均为68%。与20多年前相比,POC的分布特征与来源已经发生了改变,珠江口海域含沙量减少与营养盐含量增加可能是导致POC组成发生变化的主要原因。     

典型滨岸草地生态系统碳稳定同位素组成及分布特征

通过测定上海市青浦区东风港百慕大、白花三叶草、高羊茅和白茅等4种典型滨岸草本植物各组织以及不同垂直深度土壤有机质δ¹³C值,对滨岸草地生态系统的植物-土壤碳稳定同位素特征进行了分析.结果表明: 白花三叶草、高羊茅属于C3植物,百慕大、白茅属于C4植物,其茎叶、凋落物和根系各组织间δ¹³C值无显著差异.C3和C4植物样带表层土壤有机质δ¹³C值随着土壤深度递增而呈现截然不同的变化特征,这与样带本底δ¹³C值以及碳稳定同位素分馏效应有关,同时还受植物根系分布深度的影响.植物输入是土壤有机碳(SOC)的最主要来源,植物有机体δ¹³C组成对土壤有机质δ¹³C值有直接影响,植物各组分δ¹³C值与土壤有机质δ¹³C值均存在极显著相关.4种草本植物样带SOC含量与δ¹³C值均呈极显著相关,其中,C3植物样带SOC含量与δ¹³C值呈线性负相关,C4植物样带SOC含量与δ¹³C值呈线性正相关.     

样品预处理对有机碳同位素分析结果的影响

文中主要阐述样品预处理方法不同对于有机碳同位素分析结果将产生重要影响,并直接关系到由此而得出研究结论的可靠性。分析样品采自扬子地台震旦纪蓝田组剖面,并对相同岩石样品采取两种不同的预处理方法。分析结果显示,得到的两套数据之间存在明显的差值。这种分析差主要是来源于分析样品中残存的碳酸盐。因此,在对全岩分析样品实施有机碳同位素测定之前,务必将分析样品中无机碳除尽。此外,针对目前应用于有机碳同位素分析的样品预处理方法可能存在的问题提出看法。     

黄河口湿地有机碳来源及其对碳埋藏提升策略的启示

滨海湿地是地球上具有多种独特功能的生态系统,是地球上重要的碳库之一,其在全球碳循环中的作用在近年来越来越受到人们的重视。总结了用C/N、稳定碳同位素和生物标志物等方法追踪黄河口湿地有机碳来源的研究成果,并据此探讨了黄河口湿地的固碳提升策略。黄河口湿地是我国典型的滨海湿地,碳来源复杂,但各种示踪方法均表明有机碳的来源中陆源输入较海源输入优势明显,而且陆源输入以地表径流和植被为主,但海源输入从内陆向近海逐渐增强,碳的来源有明显的时空变化并且受到人类活动的强烈干扰。从有机质来源看,提升黄河口湿地的碳埋藏能力应该从合理调配河流淡水资源、保护植被、加快植物群落演替等方面入手。目前有机碳来源的研究还存在覆盖区域有限、碳源区分粗略、影响因子研究较少等问题,缺乏系统性,多限于观测,对机制的理解十分薄弱,因此难以对碳埋藏能力的提升提供定量化的指导。今后的研究要从以下几个方面加强:1)不同区域和不同环境条件之间的比较研究;2)探寻更具特异性的生物指标、优化数据模型,使来源区分更细致;3)不同来源有机质在沉积物中埋藏效率的对比研究;4)构建湿地碳埋藏能力评估体系,综合考虑各方面因素研发和集成能够最大限度提高滨海湿地碳埋藏能力的技术。     

Variability and transport of suspended sediment,particulate and dissolved organic carbon in the tidal freshwater Hudson River

Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.Examining downstream changes in transport showed that there was significant production of both suspended matter and POC within the study reach during the ice-free season. Tributary loadings within the study reach do not appear to be the cause of these increases in downstream transport. Dissolved organic carbon behaved conservatively in that there was no evidence for net production or net consumption within the river.The spatial/temporal patterns and analyses of transport suggest that suspended matter and POC, but not DOC, were controlled to a significant extent by processes occurring within the river and were not simply related to loadings from outside.     

Assessment of the C/N ratio as an indicator of the decomposability of organic matter in forest soils

The usefulness of the C/N ratio as an indicator of the decomposability of organic matter in forest soil was assessed. The assessment was based on the relationship between the C/N ratio and the contents of soil organic carbon (SOC), soil nitrogen (total N), dissolved total organic carbon (DTOC) and dissolved inorganic nitrogen (DIN). SOC, total N, DTOC and DIN were determined in soils sampled in coniferous and coniferous–deciduous forest sites from genetic horizons of 48 soil profiles. The variability of the above soil parameters was determined and the correlation between these parameters and the C/N values were calculated. It was found that the C/N ratio in soil was shaped by the difference in the mobility of both elements, whereas the decrease in the C content in subsequent horizons was mostly higher than the decrease in the N content, which means that the C/N value decreased with the depth of a soil profile. When the loss of SOC and total N contents occurs at a similar rate, the C/N ratio is maintained at a more or less stable level despite the advancing SOM mineralization. When the rate of the carbon release from SOM differs from that of nitrogen or when there is an N input from external sources, the C/N ratio does not adequately describe the process of SOM mineralization as well. The correlation coefficients between the C/N ratio and other parameters indicate that the relationships between them are not significant or that there is no correlation at all. It was found that the percentage of DTOC in SOC seemed to be a better indicator of SOM mineralization than the C/N ratio.     

Forest soil carbon inventories and dynamics along an elevation gradient in the southern Appalachian Mountains

Soil organic carbon (SOC) was partitioned between unprotected and protected pools in six forests along an elevation gradient in the southern Appalachian Mountains using two physical methods: flotation in aqueous CaCl2 (1.4 g/mL) and wet sieving through a 0.053 mm sieve. Both methods produced results that were qualitatively and quantitatively similar. Along the elevation gradient, 28 to 53% of the SOC was associated with an unprotected pool that included forest floor O-layers and other labile soil organic matter (SOM) in various stages of decomposition. Most (71 to 83%) of the C in the mineral soil at the six forest sites was identified as protected because of its association with a heavy soil fraction (> 1.4 g/mL) or a silt-clay soil fraction. Total inventories of SOC in the forests (to a depth of 30 cm) ranged from 384 to 1244 mg C/cm2.The turnover time of the unprotected SOC was negatively correlated (r = –0.95, p < 0.05) with mean annual air temperature (MAT) across the elevation gradient. Measured SOC inventories, annual C returns to the forest floor, and estimates of C turnover associated with the protected soil pool were used to parameterize a simple model of SOC dynamics. Steady-state predictions with the model indicated that, with no change in C inputs, the low- (235–335 m), mid- (940–1000 m), and high- (1650–1670 m) elevation forests under study might surrender 40 to 45% of their current SOC inventory following a 4°C increase in MAT. Substantial losses of unprotected SOM as a result of a warmer climate could have long-term impacts on hydrology, soil quality, and plant nutrition in forest ecosystems throughout the southern Appalachian Mountains.     

Aerial decay influence on the stable oxygen and carbon isotope ratios in tree ring cellulose

Sub-fossil wood is often affected by the decaying process that introduces uncertainties in the measurement of oxygen and carbon stable isotope composition in cellulose. Although the cellulose stable isotopes are widely used as climatic proxies, our understanding of processes controlling their behavior is very limited. We present here a comparative study of stable oxygen and carbon isotope ratios in tree ring cellulose in decayed and non-decayed wood samples of Swiss stone pine (Pinus cembra) trees. The intra-ring stable isotope variability (around the circumference of a single ring) was between 0.1 and 0.5‰ for δ¹⁸O values and between 0.5 and 1.6‰ for δ¹³C values for both decayed and non-decayed wood. Observed intra-tree δ¹⁸O variability is less than that reported in the literature (0.5–1.5‰), however, for δ¹³C it is larger than the reported values (0.7–1.2‰). The inter-tree variability for non-decayed wood ranges between 1.1 and 2.3‰ for δ¹⁸O values, and between 2 and 4.7‰ for δ¹³C values. The inter-tree differences for δ¹⁸O values are similar to those reported in the literature (1–2‰ for oxygen and 1–3‰ for carbon) but are larger for δ¹³C values. We have found that the differences for δ¹⁸O and δ¹³C values between decayed and non-decayed wood are smaller than the variation among different trees from the same site, suggesting that the decayed wood can be used for isotopic paleoclimate research.