神农架石笋氧同位素的海拔效应

作为古气候代用指标,石笋氧同位素为亚洲季风演化研究提供了一系列可靠的证据。然而,关于石笋氧同位素指示的气候意义一直存在争论。本文选取了位于神农架地区海拔1250～2250m的黑龙洞、青天洞和三宝洞3个洞穴进行对比分析,发现不同海拔洞穴石笋δ18O在波动形式上相同,但绝对值存在约-0.1‰/100m的系统差,而大气降水的在该地的海拔效应约为-0.2‰/100m。为此,我们认为,石笋δ18O除了受季风降雨的影响外,不同海拔的温度梯度也对石笋δ18O具有较大的贡献。结合洞穴年均温度,初步估算石笋δ18O的温度效应约为-0.25‰/℃,与O’Neil的同位素平衡分馏计算结果相同。      

重庆南山老龙洞地下河流域岩溶地下水DIC和δ13CDIC及其流域碳汇变化特征

以重庆南山老龙洞岩溶地下河流域为例,通过分析地下河水DIC变化特征与来源,估算了流域岩溶碳汇通量,并探讨了自然条件和人类活动对岩溶碳汇的影响。研究结果表明,老龙洞地下河的水化学类型为Ca-HCO3-SO4型,显示其形成过程中受碳酸盐岩碳酸溶蚀和硫酸溶蚀共同控制。地下河水DIC浓度为3.1~6.3mmol/L,其中夏季因受降雨稀释作用影响DIC较冬季的低;地下河水δ13CDIC值介于-3.8‰~-13.1‰之间,且夏季比冬季偏高约2‰。根据地下河水DIC浓度和流域径流量计算出流域岩溶净碳汇通量均值约为167.31×103mol/(km2?a)。降雨条件下,流域岩溶碳汇通量随流域径流量的迅速增加而增加。另外,流域碳酸盐岩溶蚀还受到人类活动产生的硫酸型酸雨影响,使得地下水δ13CDIC值相对偏高,它在一定程度上减少了流域碳汇通量。      

Compound-specific stable carbon isotopic composition of petroleum hydrocarbons as a tool for tracing the source of oil spills

With the increasing demand for and consumption of crude oils, oil spill accidents happen frequently during the transportation of crude oils and oil products, and the environmental hazard they pose has become increasingly serious in China. The exact identification of the source of spilled oil can act as forensic evidence in the investigation and handling of oil spill accidents. In this study, a weathering simulation experiment demonstrates that the mass loss of crude oils caused by short-term weathering mainly occurs within the first 24h after a spill, and is dominated by the depletion of low-molecular weight hydrocarbons (相似文献   

Nitrogen isotope ratios of nitrate as a clue to the origin of nitrogen on the Pacific coast of Japan

To clarify the sources and transformation of NO₃⁻ on the Pacific coast of Japan, observations over the continental shelf were conducted during the summer in 2005 and 2006 when the Kuroshio flowed close to and away from the coastal area, respectively. Below the halocline, there are two prominent salinity peaks that originated in two different waters. In the subsurface layer, the salinity maximum (S_max) was indicative of the Kuroshio Water (KW), while the salinity minimum (S_min) in the middle layer at ∼400 m depth was indicative of the North Pacific Intermediate Water (NPIW). δ¹⁵N_NO3 ranged from 4.1‰ to 5.1‰ with a mean of 4.8±0.4‰ in the deeper water around S_min. Below 50 m depth over the shelf break, δ¹⁵N_NO3 values (3.1±0.8‰ in 2005 and 4.6±0.3‰ in 2006) clearly increased as contribution of NPIW increased in 2006. On the contrary, subsurface δ¹⁵N of NO₃⁻ values (−1.1±0.1‰) remained unchanged in both years, although the contribution of the KW to the subsurface water changed significantly. This suggests that the source of NO₃⁻ has little effect on the δ¹⁵N of NO₃⁻ in this layer. The negative δ¹⁵N values also coincided with the base of the chlorophyll maximum layer suggesting that these isotopic signals must be evidence of active nitrification in the upper layer.     

盐生荒漠土壤水稳定氢、氧同位素组成季节动态

对准噶尔盆地东南缘降水和土壤水稳定氢、氧同位素组成（δ¹⁸O和δD）进行了测定,分析了降水中δ¹⁸O和δD值的季节变化规律,表层土壤水中δ¹⁸O和δD值对降水脉冲的动态响应以及不同深度土壤水中δ¹⁸O和δD值的变化特征。结果表明：该区域大气降水线为δD=7.691δ¹⁸O+4.606;降水与表层土壤水中δ¹⁸O和δD值表现出明显的季节变化特征;表层土壤水中δ¹⁸O和δD值、质量含水量对降水脉冲响应显著,且不同量级的降水导致不同程度的响应。利用LSD法对0~300 cm土层内土壤水中δ¹⁸O和δD值进行多重比较分析,可将土壤在垂直方向上分为3层,表层（0~50 cm）土壤水分活跃,稳定同位素值随深度的增加而迅速减小;中间层（50~180 cm）土壤水分相对活跃,既受到降水入渗和蒸发作用的影响,也有地下水的补给;深层（180~300 cm）水分来源稳定,土壤水中δ¹⁸O和δD值基本不变。     

Water sources of plants and groundwater in typical ecosystems in the lower reaches of the Heihe River Basin

Stable oxygen and hydrogen isotopic compositions （δ18O and δD） of soil water and shallow groundwater of a riparian forest, an artificial shrub forest, and Gobi of the lower reaches of the Heihe River Basin are used to study the recharge water sources of those ecosystems. IsoSource software is used to determine the δ180 values for root water of Populous euphratica and Tamarix ramosissima in the riparian forest ecosystem, Haloxylon ammodendron in the artificial shrub forest, and Reaumuria soongorica in the Gobi, as well as for local soil water and groundwater, and precipitation in the upper reaches of the Heihe River Basin. Our results showed that soil water and shallow groundwater of the riparian forest and the artificial shrub forest were recharged by river water which originated from precipitation in the upper reaches, and strong evaporation occurred in the artificial shrub forest. Soil water of the Gobi was not affected by Heihe River water due to this area being far away from the river channel. The main water sources of Populous euphratica were from 40-60-cm soil water and groundwater, and of Tamarix ramosissima were from 40-80-cm soil water in the riparian forest ecosystem. In the artificial forest, Haloxylon ammodendron used 200-cm saturated-layer soil water and shallow groundwater. The Reaumuria soongorica mainly used soil water from the 175-200-cm depth in the Gobi. Therefore, soil water and groundwater are the main water sources which maintain survival and growth of the plants in the extremely arid regions of the lower reaches of the Heihe River Basin.     

4个代表站点的珊瑚δ18O数据对热带印度洋气候变率的反演能力分析*

珊瑚中的δ¹⁸O含量可以高精度地记录热带海洋中的气候变率及气候变化信息, 从而弥补器测观测时间长度有限的缺陷, 为反演过去长期的气候状况提供了可能。热带印度洋的气候模态通过海气相互作用影响周边区域甚至全球的气候, 具有重要的研究意义。本文对比分析了1880—1999年间热带印度洋4个站点(肯尼亚、坦桑尼亚、塞舌尔、明打威)的珊瑚δ¹⁸O数据, 研究了其对热带印度洋气候的反演情况。结果显示, 珊瑚δ¹⁸O对海表温度(sea surface temperature, SST)的长期变化趋势反演良好, 珊瑚δ¹⁸O与局地SST在季节循环中保持一致, 且在低温季节对SST的变化更为敏感。此外, 4个站点的珊瑚δ¹⁸O对印度洋海盆模态(Indian Ocean Basin Mode, IOBM)和印度洋偶极子模态(Indian Ocean Dipple Mode, IODM)有一定的表征能力, 并且δ¹⁸O记录的热带印度洋年际变率受年代际变率调制。本文的研究结果表明, 珊瑚δ¹⁸O数据对于了解古气候时期热带印度洋气候变率具有重要的指示意义, 但同时也需要综合考虑不同站点的信息来完整地反映印度洋在历史时期的气候变化情况。     

湖相沉积物有机地球化学在古环境研究中的应用

湖相沉积物中的有机质蕴含着丰富的地球化学信息,是古环境研究中必要的基础资料之一。文章综述了近年来湖相沉积物有机地球化学在古环境研究中的应用,结果表明:1在应用有机地球化学信息探讨古环境时,首先要根据有机质组成特征区分其来源,不同来源的有机质,其地球化学特征存在差异;2有机质碳同位素(δ13Corg)是研究古气候变化的常用指标,在区分暖湿、暖干、冷湿、冷干气候类型时需结合沉积物中总有机质丰度(TOC)、总有机氮丰度(TN)、自生碳酸盐氧同位素(δ18O)等资料;3脂肪酸不饱和度可作为恢复古环境温度的定性指标,UK37和UK37'在定量恢复古湖水表层温度中有较好的应用效果,TEX86有望应用在古湖水表层温度的重建;4生物标志化合物可较好地区分沉积物中有机质的来源、沉积水体的盐度及氧化还原性。可见,有机地球化学是研究古环境常用且有效的技术手段,多项有机地球化学参数相互验证能够更精确地重建古环境并预测其演化趋势。     

即墨温泉地热水的氢氧同位素特征及其地质意义

青岛市即墨温泉水是含有多种微量元素的一种具特殊医疗作用的地热水。通过对即墨温泉地区在不同季节采集的温泉地热水、地下水、地表水、大气降水和近岸海水分别进行氢、氧同位素的测定。结果表明，即墨温泉水的氢、氧同位素值皆小于大气降水来源的地表水、地下水和雨水；即墨温泉地热水占δD-δ^18O相关点沿大气降水线展布表明其主要来源和补给源为大气降水，估算的循环深度约为2017．6m。在有利的构造部位和良好的储水条件下，大气降水经深循环加热和水岩反应淋滤盐分，并沿断裂上升出露地表，形成矿化度较高的温泉。