The significance of lake sediments geochemistry in environmental reconstruction of south Hongshan Lake, northwestern Tibetan Plateau during the past 150 years

A 107cm piston-core (SHC-2) was drilled at the site with water depth of 5m in South Hongshan Lake, northwest Tibet in 1998. Based upon the 0.72cm/a of modern sedimentary rate that was tested by 210Pb method and also calibrated by 137Cs method as well as the 1cm interval sample cutting level, a lake sedimentary record of 150-yr old and with a resolution of 1.4 yrs was obtained. Ratio of geochemistry contents (TOC, TN, CaCO3) and concentrations of trace elements such as B, Sr, Ba, Ca, Mg, K, Na, Al, Ti, Cu, Zn, Fe, Mn, Ni, Cr, V, Pb, etc were analyzed. The values of TOC, TN, C/N, CaCO3, Sr/Ba and Fe/Mn had clear environmental significance and well reflected the environmental changes. Geochemical multi-proxies of lacustrine sediments from SHC-2 core showed that the environmental changes in this area during the past 150 years could be reconstructed as follows: Stage 1 (1850s-1880s) was a cold period; Stage 2 (1880s-1920s) was a warm period. But the variation of lake water volume was stable in the two periods. Stage 3 (1920s-1950s) was a fluctuant and transitional period in temperature, but there were a short cold period in the 1920s and a warm period in the 1930s. Stage 4 (1950s-) showed a warming tendency, though there existed a cold period from the mid 1970s to the end of the 1980s. In the view of general trend in the past 150 years, South Hongshan Lake was shrinking gradually. It showed that, from the comparison with the Guliya ice core and meteorological records of adjacent weather stations, there is difference in the variations of temperature and precipitation among different regions and altitudes in Tibetan Plateau. It is necessary to search multi-scale and high-resolution records for environmental reconstruction and comparison.

Environmental changes reflected by the lake sediments of the South Hongshan Lake, Northwest Tibet

The 1.07-m long lake core with 1 cm interval cutting, which was obtained by drilling in the South Hongshan Lake of Northwest Tibet, was dated by the 210Pb and 137Cs methods, and a 150-year consecutive lake sedimentary sequence (1840─1997) with 1.4 year resolution was obtained. Some environmental proxies, such as the total organic carbon (TOC), total nitrogen (TN), ratio of TOC to TN (TOC/TN), trace chemistry elements (TCE), CaCO3, grain size, richness of ostracoda etc. showed that they are of well coincidence. These results implied that the environmental background varied from the cold-wet period in the late 19th century, to the warm-wet period from the end of the 19th century to the 1920s and to the warm-dry period since the 1920s. There were sub-variations since the 1920s: the cold-dry/warm-wet fluctuation from 1922 to 1960, the intensively warm-dry period since 1960 with a short cold-wet period in the mid-1970s to the end of the 1980s. The humid period from the mid-1970s to the end of the 1970s and the dry period beginning from the early 1980s were well documented by climatic data of the nearby weather station records while the grain size was well correlated to the annual precipitation. Compared with the records from Guliya ice core in the same area, the TOC proxy in the lake core indicating warm/cold conditions well corresponded to the ( 18O records representing temperature variations in the ice core. However, the proxies with dry/wet significance in the lake core were different from the variations of snow accumulation reflected by the ice core. It can be concluded that the chosen environmental proxies have clear environmental significance and the lake sediments can reflect climatic and environmental changes at high-resolution.

150年来青藏高原南红山湖的介形类与环境变化

青藏高原西北部南红山湖 2孔湖芯沉积物中的介形类动物群计有 4属 4种 ,据其分布特征划分出 5个组合 ,各组合间的差异表现在介形类动物群丰度和每个种的丰度变化以及特征种的出现。通过分析介形类属种生态特征和组合变化对 150年来的南红山湖环境变化进行了探讨。分析结果表明 :1884年前为有缓慢水流注入的滨岸浅水期 ;1885～ 1970年间为湖水相对温暖期 ,在这期间湖泊环境仍有次一级的变化 ,其中 ,1885～ 190 5年湖面迅速抬升 ,水深增大 ,水温也较高 ,192 3～ 194 4年为湖水温度另一个稍高期 ,196 1～ 196 9年湖面再次出现明显上升 ;1970年以来湖泊退缩、咸化。

近150a来南红山湖的地球化学特征及环境意义

通过对西昆仑山南红山湖的沉积地球化学特征的分析 ,恢复了南红山湖区近 15 0a来的环境变化。 19世纪5 0年代初～ 19世纪 80年代中期 ,气候受小冰期末次波动的影响 ,以冷湿为特点。 19世纪 80年代中期～ 1997年 ,处于小冰期后回暖期 ,以暖干趋势为主。其中 19世纪 80年代中期～ 2 0世纪 2 0年代初 ,以暖干为特点 ;2 0世纪 2 0年代初～ 2 0世纪中叶 ,气候较干燥 ,而且温度与湿度的结合较复杂 ,属于冷干 -暖湿交替的气候类型 ;2 0世纪中叶～ 1997年 ,气候总特征以暖干为主 ,尤其是 1990年以后 ,温度升高趋势明显 ,气候干燥。从近 15 0a湖泊变化的整体趋势看 ,随着时间的推移 ,南红山湖在逐渐萎缩。就湖区的气候变化与西昆仑山古里雅冰芯所恢复的气温、降水变化及与较近的两个站点的气象记录进行了对比 ,认为该地区与古里雅冰芯地区受相同的气候系统控制 ;高原上区域间存在气候差异 ;应开展多尺度、高分辨率的多种代用资料的研究。

贵州安顺虹山湖环境调查及芦苇对湖内生态环境影响探讨

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通过开展甜水海地区红山湖的泉水与湖水水文地球化学相关测试分析,探索区内水化学成分形成过程以及水体地球化学特征与来源,从而获得与油气有关的水文地球化学信息。结果显示:红山湖泉水总体呈弱碱性,以微咸水为主,水体主要离子质量浓度随着矿化度增加而增加,水化学类型为Na-HCO 3型;其主要补给为大气降水,且补给的大气降水在顺断裂或裂隙深循环过程中与围岩发生了水岩作用;矿化度、水化学类型以及泉水特征系数指示其代表的地下水体水动力较弱,且变质程度较深,与油田中油气伴生的地层水特征相似,推断该区地质环境整体利于油气形成与保存。

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安全保障是城市建设思想的重要部分。喀斯特地貌城市由于生态、地理性质、城市结构复杂、城市空间布局分散,其对城市韧性、承灾性要求高。城市“绿心”是安全城市建设功能的重要组成部分,在平灾情况下承载了重要的城市功能,一方面承担防灾减灾、辅助应急避难、提升城市韧性的功能;另一方面起到周转城市慢行空间系统,连结城市廊道的作用。文章结合安顺虹山湖公园规划的实践研究,探索安全城市视角下喀斯特地貌城市“绿心”规划策略。

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城市公园对城市温湿度的调节具有重要作用,同时也是城市居民释放压力、接触自然、休闲健身的不二之选。本文以安顺市虹山湖公园为例,采用实地调查法、访谈法、问卷分析法等,通过对虹山湖公园一天当中早中晚三个时间段的人流量、人员的构成、人员的行为活动,以及公园提供的服务设施等要素进行调查,对虹山湖公园的现状进行使用状况评价(POE),并给出一定的优化建议和策略,为今后城市公园的建设管理、服务设施等提供参考思路。