Ra–Po–Pb isotope systematics in waters of Sambhar Salt Lake,Rajasthan (India): geochemical characterization and particulate reactivity

The Sambhar Salt Lake hydrological system, including river waters, groundwaters, evaporating pans and sub-surface brines, has been analyzed for the salt content (TDS) and naturally occurring radionuclides (²¹⁰Po, ²¹⁰Pb and ^226,228Ra). The abundance of these radionuclides and their activity ratios show a wide variation in different hydrological regimes, which helps to geochemically characterize the lake system. A significantly lower Ra to total dissolved solids (TDS) ratio in the brines (by two to three orders of magnitude), when compared to the groundwaters and river waters, suggests removal of dissolved Ra by co-precipitation with Ca–Mg minerals at an early stage of the brine evolution. The concentration of Ra in evaporating lake/pan waters saturates at a value of about 35 Bq L⁻¹ over the salinity range of 100–370 g L⁻¹; attributable to its equilibration with the clay minerals. The two distinct regimes, saline lake system (lake water, evaporating pans and sub-surface brines) and groundwaters have been identified based on their differences in the distribution of ^226,228Ra isotopes. This observation points to the conclusion that the groundwaters and the lake brines are not intimately coupled in terms of their origin and evolution. The abundances of ²¹⁰Po and ²¹⁰Pb along with their activity ratios (²¹⁰Po/²¹⁰Pb) are markedly different among the surface lake waters/evaporating pans, sub-surface lake brines and groundwaters. These differences are explained in terms of different geochemical behaviour of these nuclides in presence of algae and organic matter present in these water regimes.     

玄武湖挺水植物区与敞水区浮游甲壳动物昼夜水平迁移初探

浮游甲壳动物昼夜垂直迁移(DVM)是深水湖泊中的一种常见的现象,在浅水湖泊中,没有明显的下层滞水层为浮游甲壳动物提供避护所,浮游甲壳动物的垂直迁移活动不明显。但浅水湖泊挺水植物的存在为浮游甲壳动物提供了区别于敞水带的生境,结合理化、浮游植物和鱼的因素,对浅水湖泊玄武湖挺水植物区与敞水区浮游甲壳动物的昼夜水平迁移进行了研究。结果得出：浅水湖泊玄武湖中理化环境（如温度、溶解氧和pH)在荷花区、敞水区、荷花区与敞水区的交界区差异不大,对浮游甲壳动物的昼夜水平迁移不起主导作用。荷花区的浮游植物在质量和数量上低于敞水区,浮游甲壳动物在夜间捕食压力小的情况下会向敞水区移动。敞水区、交界区浮游甲壳动物在白天被捕食的风险要大于荷花区,因而白天时间浮游甲壳动物会迁移到荷花区聚集.     

利用中巴地球资源卫星数据反演武汉市湖泊营养状态指数

以武汉市主要湖泊为例,研究了利用中巴地球资源卫星（CBERS2）数据反演水体营养状态指数（TLI）。研究旨在评估利用中巴地球资源卫星数据来估算内陆水体富营养化程度的可能性。首先利用地面水质监测数据计算武汉市某些湖泊监测点的“真实的”营养状态指数（包括综合营养状态指数和修正的Carlson营养状态指数）,同时,在事先经过辐射校正和几何校正的CBERS2图像上,以9×9像元为采样窗口,提取各个对应地点的灰度值均值（从波段1至波段4）;然后,采用多元逐步回归分析,以各波段灰度值均值为自变量,建立营养状态指数经验遥感反演模型;最后,利用模型对整个湖泊水体的营养化状态指数进行反演,并绘制了其空间分布图。 结果显示,营养状态指数的自然对数值与CBERS2图像各波段灰度值之间存在较好相关关系,回归系数平方值(R²)为0.51。利用反演模型反演得到的湖区水质分布与实际情况基本相符。由于CBERS2图像数据可以从我国许多数据分发中心免费获取,这为低成本的水质遥感监测提供了一条途径。     

基于加权叠加模型的高原湖泊流域重要生态用地识别——以星云湖流域为例

生态用地在维持区域生态平衡和保障区域生态安全具有重要意义。以云南星云湖流域为研究区,运用层次分析法和GIS技术,从水土保持、地质灾害规避与防护、生物多样性保护和水资源安全4个方面,构建了流域重要生态用地识别指标及其识别方法,并识别出流域重要生态用地空间分布。结果表明:(1)加权叠加模型更适用于高原湖泊流域重要生态用地识别;(2)根据生态用地重要性分为核心型、辅助型、过渡型和非重要生态用地,面积分别为75.98 km~2、105.05 km~2、89.47 km~2和65.11 km~2,分别占流域生态用地总面积的22.64%、31.30%、26.66%和19.40%。识别结果能较好地反映重要生态用地维护流域的生态安全。以星云湖流域作为高原湖泊流域的典型,为高原湖泊生态保护提供科学方向,以期协调流域经济发展与生态保护的矛盾,促进可持续发展。     

At the intersection of disaster risk and religion: interpretations and responses to the threat of Tsho Rolpa glacial lake

Over the last several decades, the scientific community has replaced the ‘acts of god’ explanations for disasters with a view that disasters are actually ‘acts of nature,’ and more recently, ‘acts of human behavior and decision making.’ Despite the secular orientation of contemporary disaster research, religious beliefs still govern people’s interpretations of natural events across many continents and cultures. Using a case study of a rural Sherpa community in Nepal, this paper responds to the challenge of linking religion and disaster risk in the context of a climate change-induced glacial lake outburst flood hazard. Data collection employed ethnographic techniques including participant observation and 53 interviews with community members. Results indicate that the case study community’s religious belief system influences how they interpret and respond to the glacial lake hazard, although their beliefs co-exist with more scientific interpretations of risk. Rather than being immobilised by their belief system, we found that religious aspects like rituals and prayer can enhance social cohesion and contribute to capacities for coping with fear and uncertainty in this community. We assert that religion can yield valuable resources to glacial lake risk reduction strategies, which will benefit from incorporating social-cultural factors more profoundly.     

The Contribution of Marsh Zones to Water Quality in Dutch Shallow Lakes: A Modeling Study

Many lakes have experienced a transition from a clear into a turbid state without macrophyte growth due to eutrophication. There are several measures by which nitrogen (N) and phosphorus (P) concentrations in the surface water can be reduced. We used the shallow lake model PCLake to evaluate the effects of three measures (reducing external nutrient loading, increasing relative marsh area, and increasing exchange rate between open water and marsh) on water quality improvement. Furthermore, the contribution of different retention processes was calculated. Settling and burial contributed more to nutrient retention than denitrification. The model runs for a typical shallow lake in The Netherlands showed that after increasing relative marsh area to 50%, total phosphorous (TP) concentration in the surface water was lower than the Maximum Admissible Risk (MAR, a Dutch government water quality standard) level, in contrast to total nitrogen (TN) concentration. The MAR levels could also be achieved by reducing N and P load. However, reduction of nutrient concentrations to MAR levels did not result in a clear lake state with submerged vegetation. Only a combination of a more drastic reduction of the present nutrient loading, in combination with a relatively large marsh cover (approximately 50%) would lead to such a clear state. We therefore concluded that littoral marsh areas can make a small but significant contribution to lake recovery.     

羊角月芽藻摄取磷形态的动力学研究

将湖水中的磷分成总溶解磷,溶解反应磷,总反应磷、溶解的水解性磷,溶解的光解性磷。研究其在羊角月芽过程中的变化。     

射阳湖浮游动物群落结构特征及其与环境因子相关性研究

2016—2017年对射阳湖开展浮游动物群落结构和水质指标逐月监测。结果表明,射阳湖共鉴定出浮游动物61种,其中原生动物、轮虫、枝角类和桡足类分别为25种、24种、7种和5种。浮游动物种类数呈现春夏季多于秋冬季的变化趋势。浮游动物优势种数量较多、分布广,群落结构相对复杂且稳定。运用Shannon-Wiener指数、均匀度指数和B/T指数对射阳湖水质作评价,结果表明,该湖处于轻度—中度污染状态,生物学指标评价法与常规水质评价结果一致。浮游动物群落结构与水质指标相关性分析表明,水温、透明度、Chl-a和DO是影响射阳湖浮游动物群落结构的主要水质指标。     

镧改性膨润土对底泥内源磷控制效果

以商业化的锁磷材料—镧改性膨润土(Phoslock?)为对象,研究了Phoslock?对磷的吸附动力学和等温线,同时研究了材料对上覆水体以及底泥内源磷释放的控制效果.结果表明,Phoslock?对磷的吸附可以用Langmuir模型拟合,相关性达到0.96,模型计算磷的最大吸附量为10.4mgP/g,且磷吸附符合拟一级和...     

REVIEW OF A SEVENTEEN-YEAR CHLOROPHYLL RECORD AS IT PERTAINS TO THE TROPIIIC STATUS OF LAKE OKEECHOBEE,FLORIDA, USA1

ABSTRACT: A 17-year record of chlorophyll a at eight limnetic sampling stations was used to evaluate putative changes in the trophic status of Lake Okeechobee, a shallow polymictic lake located in the subtropical environment of South Florida. Significant spatial differences were observed in the temporal patterns and variability of chlorophyll a concentrations. The highest chlorophyll a values were found in the northern and northwestern regions of the lake. The center of the lake, subject to high levels of non-algal suspended solids, exhibited relatively low chlorophyll a values and coefficient of variation. The lowest chlorophyll a values were observed at the southernmost sampling station in the lake. This was also the station that showed a significant upward trend in annual mean chlorophyll a values over the 17-year period of record. Examination of the relationship between chlorophyll a and three key environmental variables (i.e., total phosphorus concentration, phosphorus loading, and lake stage) revealed significant correlations at two out of the eight stations. The overall results of this study indicate that spatial and temporal disparities in the distribution and dynamics of chlorophyll a in Lake Okeechobee mandate more temporally and spatially intense approaches to the evaluation of trophic state than used in previous studies.