A 1,100-year palaeoenvironmental record inferred from stable isotope and trace element compositions of ostracode and plant caryopses in sediments of Cattle Pond,Dongdao Island,South China Sea

Abundant ostracode valves (Cyprinotus cingalensis) and caryopses of Urochloa paspaloides, a terrestrial grass, were well preserved in the lacustrine sediments of the Cattle Pond on Dongdao Island, South China Sea. Oxygen and carbon isotopes, and elements (Ca, Mg) were analyzed on ostracode valves and plant caryopses in this study. The δ¹⁸O_ostracode and δ¹³C_ostracode exhibited a positive and statistically significant correlation, and showed a decreasing trend toward the top of sediment sequence with some fluctuations, indicating a gradual increase in effective moisture. The Mg/Ca ratios in the ostracode shells, generally used as a proxy for salinity changes in lake water, showed a trend toward lower values in the upper samples, reflecting a gradual decrease of salinity in the lake. The δ¹³C_org values in the plant caryopses of the upper 14 cm of sediment have lower values than those in the bottom sediments, suggesting less water and salinity stress. These results indicate increasing effective moisture and rainfall intensity over the past ∼1,100 years on Dongdao Island.     

艾比湖二千余年来环境演变的地球化学记录

通过对新疆艾比湖Ash孔二千余年以来沉积的总有机碳含量及其碳同位素、碳酸盐含量及Mg／Ca比值等环境指标综合分析,数据显示：约在公元前500-400年,艾比湖水体面积较小,对应的气候偏干。约公元前400～公元1400年,水体面积较大,处于高水位时期,气候较为湿润,但此时期内的气候也有小幅的冷暖和干湿变化。其中在公元800-1300年期间艾比湖沉积记录显示水生生物对沉积有机质的贡献达到最大,而陆源有机质输入不明显,表明此时湖水水位可能达到二千余年来的最高,这一时段基本对应于中世纪暖期。从碳酸盐含量及Mg/Ca比值指标来看,该地区中世纪暖期可能有一个干湿的波动。公元1400年以来,艾比湖水位下降,其中在15世纪中和19世纪初是两次较为干燥的时期,与其他地区的小冰期气候相对应。     

高山植物稳定碳同位素沿海拔梯度响应机制的研究进展

简要介绍了国内外关于植物δ~(13)C对海拔梯度响应规律的研究情况,叙述了植物叶片δ~(13)C对海拔梯度响应的内在机理.重点介绍了随海拔变化的气压、温度、降水(湿度)、光照等环境因子和植物的叶片厚度、比叶重(LMA)、氮含量、气孔密度、气孔导度等生物因子对高山植物δ~(13)C的影响作用.由于各因子的多变性以及之间的相互作用,任何单一因子都不足以决定植物δ~(13)C的最终变化,也不能解释植物δ~(13)C随海拔的变化趋势,这种趋势可能是众多因子综合作用的结果.最后对本领域取得的一些认识和结论进行了总结,并对存在的一些问题以及今后的研究方向提出了一些见解.     

Spatial variation of nutrients and primary productivity in the Rufiji Delta mangroves,Tanzania

Determinations of spatial and temporal variations in organic matter and nutrient dynamics in water and sediments are crucial for understanding changes in aquatic bodies. In this study, we (i) determine the spatial dynamics of dissolved inorganic nutrients, during the transition from the dry to the rainy season, and (ii) provide future productivity predictions for the Rufiji Delta mangroves, Tanzania, based on the input of various nutrients. Water samples were collected from six locations, three times per year between April 2012 and January 2014, and analysed for dissolved nutrients, total organic and inorganic carbon, chlorophyll a, chlorophyll b and total carotenoids. The prediction of future net primary productivity in the Rufiji mangroves was undertaken using the software STELLA. The mean nutrient concentrations were of the order: nitrate > phosphate > ammonium > silica > dissolved organic carbon. The study revealed that high nutrient concentrations occurred in the northern part of the Rufiji Delta as a result of anthropogenic influence in the watershed. Modelling of nutrient inputs into the delta indicated enhanced primary productivity, which is expected to increase the vulnerability of water quality in the near future due to eutrophication.     

多种水面类型蒸发的研究

分析有水草水面、污水面、受热水面、盐水（盐水）面等特定水面类型的蒸发量，并与清水、淡水对照，求出蒸发比，还计算了太湖地区有水草水面和受热水面的蒸发模型，为确定湖泊的蒸发量提供一新途径，最后建议用水生植物的蒸腾规律来控制水面蒸发，调节水面温度。     

Quaternary changes in delivery and accumulation of organic matter in sediments of Lake Biwa, Japan

A 911-m-long sediment core from Lake Biwa, Japan, provides a record of organic matter delivery and accumulation in this large lake during a succession of tectonic and climatic changes dating back to the latest Pliocene. Sediments deposited since 430 ky are profundal; older sediments vary in setting between shallow-water and fluviodeltaic conditions, with occasional deep-water intervals. C/N ratios identify algal production as the dominant source of organic matter throughout the core, although the proportion of land-derived contributions episodically increases in the fluviodeltaic and shallow-water sediments. Rates of organic matter delivery and burial in lake sediments change in response to glacial-interglacial climate changes over the past 430 ky. Sediments deposited during interglacial intervals have organic carbon mass accumulation rates up to 9 times greater than those from glacial intervals, reflecting interglacial climates that were wetter than glacial climates. Algal production of organic matter increased during interglacial times because of greater wash-in of soil nutrients, and organic matter preservation was enhanced because of faster sedimentation rates.     

亮红外星系NGC 1614中多谱线示踪的致密分子气体

利用高空间分辨率的¹²CO(1-0)、¹³CO(1-0)、¹²CO(3-2)、¹²CO(6-5)、HCN(3-2)、\lk HCN(4-3)、 HCO⁺(3-2)和HCO⁺(4-3)分子谱线的ALMA (Atacama Large Millimeter/ submillimeter Array)归档数据, 来研究近邻亮红外星系NGC 1614的分子气体性质, 尤其是致密分子气体的性质. 在高分辨率分子气体谱线的积分强度图中, 在星系中心区域($<$ 1kpc)可以看到环状结构, 分子气体主要分布于星系中心区域, 核区分子气体含量较少. ¹²CO(1-0)显示出向南部、 北部以及东南部的延展结构, 高阶的CO ($J \ge$ 3, J为转振能级量子数)分子谱线和致密分子HCN、HCO⁺谱线显示, 较致密的分子气体主要集中于星系中心区域. HCN(4-3)/¹²CO(1-0)和HCN⁺(4-3)/¹²CO(1-0)积分强度比值图显示, 致密分子气体主要集中于中心区域的环状结构上. HCN/HCO⁺强度比值的分布变化表明星暴环的不同区域可能具有不同的激发条件. HCN/HCO⁺(4-3)强度比值分布在环的东、西部(sim0.44 pm 0.04)高于环的南、北部(sim0.35 pm 0.03). HCN/HCO⁺(3-2)强度比值较高的区域(sim0.38 pm 0.04)分布在HCN(3-2)峰值位置, 而环的西北、东南部强度比值相对较低(sim0.3 pm 0.03). 对于中心不同区域 HCN/HCO⁺比值变化的原因进行了讨论.     

Correction factors for estimating suspended sediment export from loess catchments

This study focuses on problems related to estimating the exact exported suspended sediment quantity and quality from flow‐proportional samples taken at a fixed height at the outlet of a small, agricultural catchment in central Belgium. First, a correction factor is introduced to estimate the real suspended sediment concentration. This factor depends on the stream depth and the grain size distribution of the sediment and is necessary because of the presence of a concentration gradient in the stream. Secondly, water depth is corrected for the sediment volume, and thirdly, the grain size distribution of the exported sediment is corrected. The application of these correction factors leads to a reduction of the estimated total sediment export by 18 per cent (from 4810 Mg over a period of three years to 3930 Mg). Furthermore, the importance of small grain size fractions increases, leading to higher enrichment ratios for the clay fraction and lower ratios for the sand fraction. Suspended sediment export is thus more selective than was previously thought. Due to the overestimation of the sediment export, total phosphorus losses from the catchment are also overestimated by 17 per cent. This paper therefore emphasizes that point sampling of suspended sediment is biased and that a method should be incorporated to correct the sediment export in terms of quantity and quality. Copyright © 2001 John Wiley & Sons, Ltd.     

科尔沁沙地退化植被恢复过程中碳氮化学计量特征的变化

为研究沙地退化植被恢复过程中碳氮化学计量特征的变化,分别于2011年、2013年和2015年8月中旬对流动、半固定、固定沙丘和草地进行植被调查,并测定植被—土壤系统的碳氮化学计量特征。结果表明：（1） 随着沙地退化植被的恢复,地上植物、凋落物和根系的C、N含量及C/N比波动变化,土壤（0～10 cm）C和N含量及C/N比显著增加（P <0.05）。（2）沙地4种生境上的地上植物、凋落物、根系、土壤的C、N含量及C/N比年际间变化显著（P <0.05）。（3） 沙地退化植被恢复过程中地上植物、凋落物、土壤的C/N比与物种丰富度呈正线性关系（P <0.01）。沙地退化植被恢复过程中优势植物演替导致植被—土壤系统中C、N化学计量特征的变化,植被恢复过程中植物的氮素利用效率也在逐渐增强,而封育时间的增加能够促进沙地土壤中N的积累。     

通用地图投影选择研究

在分析现有的地图投影选择、评价标准和地图投影形变量之间关系的基础上,尝试引入形状比、长度比和面积比的概念,作为通用地图投影的选择、评价的基本度量指标,并通过层次分析法确定其权重,为通用地图投影的选择提供了思路,并通过实验验证了该方法的可行性与合理性。