Identifying outliers and assessing the accuracy of amino acid racemization measurements for geochronology: I. Age calibration curves

Numerical ages derived from amino acid racemization (AAR) geochronology are typically based on calibration curves that relate the extent of AAR to the age of independently dated specimens. Here, we compare options for developing calibration curves and quantifying age uncertainties using AAR data from 481 late Holocene shells, and AMS ¹⁴C analyses of 36 shells of four molluscan taxa (Ethalia, Natica, Tellina, and Turbo) collected from shallow sediment cores from a back-reef lagoon of the central Great Barrier Reef. The four taxa differed substantially in the quality of their geochronogical results. Explicitly including data from specimens alive at the time of collection improves calibration curves, but weighting numerical ages based on their uncertainty has no effect. Calibration curve statistics do not adequately assess calibration uncertainty. The relation between ages inferred from different amino acids is recommended for identifying aberrant specimens and quantifying the uncertainty of inferred ages. For this study, the AAR ages based on two amino acids (aspartic acid and glutamic acid) exceed 200 yr or 20% of their mean inferred age in 15% of the specimens. Once these were removed, the mean age error (1σ) for individual specimens based on two amino acids analyzed in duplicate subsamples ranged from 53 to 142 yr for Tellina and Turbo, respectively, or about a 30% age error for these relatively young shells. This compares favorably with analytical errors estimated at 50 yr or 5%. The presence of notable outliers undetectable using data from single amino acids emphasizes the importance of analyzing multiple amino acids.     

非饱和土热力学参数确定的探讨

研究非饱和土热力学的力学性质,必须建立能量守恒方程,表征能量的两个基本物理力学参数（体积比热系数和热传导系数）的确定是求解能量守恒方程的重要因素。对于不同颗粒组成的土体,对其干燥颗粒有效热力学参数进行了分析,对固体、液体和气体三相共存的热力学参数进行了研究,并对计算结果进行了对比分析,在此基础上,提出了较适合计算热传导系数的方法,并将此方法和体积平均法、自洽法及Hashin-Strikman方法进行了比较。经与试验结果对比表明：提出的方法能较好地描述非饱和土的热力学参数特性。     

球形颗粒紧密堆积状态时的吸力分析

根据圆液面假设和热力学基本原理,研究了球形颗粒紧密堆积模式在水封闭状态（状态2）时的吸力特性,得到了状态2中3类吸力和3类等效吸力与饱和度的定量关系和以接触角和饱和度或饱和半径为参数的吸力比表达式。进一步的研究表明,在状态2中吸力比都小于1,与基于松散堆积模式在水封闭状态（状态1）时得到的结果比较后可知,随着颗粒排列密实度的增大,相对于基质吸力,张力吸力的作用将有所降低但仍然不可忽视。另外,随饱和度变化,状态2中的3类吸力,特别是3类等效吸力的变化趋势与基于状态1得到的结论基本一致。在状态2中,对数吸力比与饱和半径呈明显的线性关系,吸力比与饱和度也呈明显的线性关系,前者与状态1中的吸力演化规律一致,而后者则存在较大不同。     

湖北宜昌×××条带状磷块岩选矿试验研究

×××磷矿属海相沉积型磷块岩矿床,主要具有胶状泥晶结构和磷质砂屑结构,以条带状构造为主。采用单一反浮选选矿工艺,使用硫酸为抑制剂、中化地质矿山总局地质研究院研制的K-02为捕收剂,在常温条件下取得较好的选矿工艺指标。进行了实验室重液浮沉试验。     

热带珊瑚礁区红腹海参及绿刺参食物来源分析——脂肪酸标志法

沉积食性海参通过大量摄取沉积物在热带珊瑚礁生态系统中发挥重要的生态功能,但其食物来源组成尚不清楚.本文研究了海南三亚近岸典型珊瑚礁海域红腹海参(Holothuria edulis)及绿刺参(Stichopus chloronotus)脂肪酸组成,利用脂肪酸标志法探讨了夏季和冬季两种海参的食物来源异同.结果表明,红腹海参...     

Ground Based FTIR Measurements of Stratospheric Species from Harestua, Norway During Sesame and Comparison with Models

Vertical columns of HF, HCl, HNO3, ClONO2, N2O, ClO and COF2 were measured at Harestua, Norway (60.22° N, 10.75° E, Elevation 600 a.s.l.) beginning on 24 November 1994 and concluding on 1 May 1995 during Phase-III of the SESAME (Second European Stratospheric Arctic and Mid-latitude Experiment) measurement campaign. The vertical columns of HCl, HNO3 and ClONO2 measured on 81 days were compared with columns calculated by the 3-D Cambridge model SLIMCAT. In addition the results were also interpreted by comparison with a photochemical trajectory model. Good agreement was seen for HCl while the nitrogen compounds showed larger discrepancies, especially for ClONO2. Evidence for chlorine activation was seen with 65% reduction of the chlorine reservoirs (HCl + ClONO2) while the levels of ClO were greatly enhanced. Interpretation of the loss with the trajectory model indicated condensation of chlorine on PSCs. The vertical column ratio of COF2 and HF was measured to 0.21 outside the vortex and a factor of two lower inside. The recovery of ClONO2 was seen to be much faster than that of HCl in the early spring.     

上海地区酸雨气候特征及成因分析

基于宝山及浦东两个气象站的酸雨历史观测资料,分析了上海地区酸雨长期变化的气候特征及其形成原因,并对比分析降水酸度的空间分布差异。宝山站降水总体上呈弱酸性,多年平均pH值为5.21,酸雨率为24%。降水pH值年际变化仅呈现微弱下降趋势,电导率K值呈明显地逐年上升变化,平均每年增加2.0 μs·cm^-1,而酸雨率波动较大,由2004年8%增至2009年48%。降水pH值在冷季较低,暖季较高,电导率K值正相反。浦东酸雨平均pH值4.38,低于宝山的5.08,酸雨率浦东79.5%,远高于宝山的33%。大气污染物SO₂、NO₂及PM₁₀浓度与酸雨pH值呈负线性相关,而与电导率K值呈正相关。大气颗粒物含量、污染物化学组成、降水量、风向等对降水pH值及酸雨率变化具有重要的影响作用。     

NaCl Aerosol Particle Hygroscopicity Dependence on Mixing with Organic Compounds

Organic compounds in the atmosphere can influence the activation, growth and lifetimes of haze, fog and cloud droplets by changing the condensation and evaporation rates of liquid water by these aqueous aerosol particles. Depending on the nature and properties of the organic compounds, the change can be to enhance or reduce these rates. In this paper we used a tandem differential mobility analyzer (TDMA) to examine the effect of tetracosane, octanoic acid, and lauric acid on the hygroscopic properties of NaCl aerosol particles at relative humidities (RH) between 30 and 95%. These organic compounds have been identified in ambient aerosol particle samples. A slight lowering of the deliquescence relative humidity (DRH) and suppression of hygroscopic growth for the NaCl-organic compound mixtures were observed when compared to pure NaCl particles. The growth of pure NaCl particles was 2.25 in diameter at 85% RH while the growth of the mixed particles was 1.3 to 1.7 in particle diameter at 85% RH with organic mass fraction of 30–50%. This shows that these organic compounds have to be present in rather large mass fractions to effect the hygroscopic behavior to a similar degree observed for ambient aerosol during field measurements. Despite the mixing of the organic material with NaCl, hysteresis was observed for decreasing RH histories, suggesting the formation of metastable droplets. These laboratory results are strikingly similar to ambient field results. For example, if the total organic mass fraction of the particles is between 0.30 and 0.50, the particle growth at 85% RH is about a factor of 1.4 for the laboratory and field measurements. Such reduction in growth compared to the pure inorganic salt is in contradiction to speculations concerning significant effects by organic compounds on cloud condensation nuclei and thus formation on clouds.     

南宁市酸雨特征及来源分析

通过对酸雨观测资料和污染源资料的统计分析，并利用拉格朗日烟团模式计算表明，南宁市酸雨的频率较高，pH值较小；南宁市酸雨的来源构成以外来源为主。运用天气学诊断方法，对气象要素影响酸雨来源进行了分析，结果表明，南宁市酸雨主要受东北方污染源影响，且冬春两季的影响最大，风频及逆温对酸雨的影响较大。在上述分析的基础上，总结出近两年大气环流影响酸雨的几种类型，其中以高空槽锋面型为最多，酸雨影响程度也最严重。     

中国西南典型地区酸雨形成过程研究

本文根据云水和雨水化学特性的观测和雨水酸化模式的模拟计算，研究了中国西南地区酸雨的形成过程。结果表明:在重庆和贵阳等重污染城市，云下过程对雨水的酸化起主要作用，在污染较轻的中小城镇和乡村地区，雨水酸度主要决定于云内过程。 但是云下过程对雨水中的主要酸碱离子浓度都有不可忽视的明显影响。雨水的酸化主要是由于SO2与H2O2和O3的氧化，气溶胶起较弱的缓冲碱化作用。在重庆和贵阳等地，当地SO2浓度已高达饱和，其值增减50％，都不会对该地雨水酸度有明显影响，起控制作用的是氧化剂浓度。