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.     

Widespread waterborne pollution in central Swedish lakes and the Baltic Sea from pre-industrial mining and metallurgy

Metal pollution is viewed as a modern problem that began in the 19th century and accelerated through the 20th century; however, in many parts of the globe this view is wrong. Here, we studied past waterborne metal pollution in lake sediments from the Bergslagen region in central Sweden, one of many historically important mining regions in Europe. With a focus on lead (including isotopes), we trace mining impacts from a local scale, through a 120-km-long river system draining into Mälaren - Sweden's third largest lake, and finally also the Baltic Sea. Comparison of sediment and peat records shows that pollution from Swedish mining was largely waterborne and that atmospheric deposition was dominated by long-range transport from other regions. Swedish ore lead is detectable from the 10th century, but the greatest impact occurred during the 16th-18th centuries with improvements occurring over recent centuries, i.e., historical pollution > modern industrial pollution.     

太湖沉积物重金属污染及生态风险性评价

对1993年～1999年所采集的太湖表层沉积物中重金属含量进行了统计分析和生态风险性评价.结果表明,太湖沉积物的pH值呈中性至弱碱性,较适合于沉积物中粘土矿物及腐殖质对重金属的吸附;太湖大部分地区沉积物未受到重金属污染,且沉积物中重金属处于安全状态.沉积物生态风险性指数评价结果也表明,太湖大部分地区目前无重金属生态危害.     

Global fallout Pu recorded in lacustrine sediments in Lake Hongfeng, SW China

Studies on the distribution and isotope compositions of fallout Pu are important for source characterization of possible future non-fallout Pu contamination in aquatic environments, and useful for dating of recent sediments to understand the pollution history of environmental contaminants. We present the historical record of atmospheric Pu fallout reconstructed from a sediment core from Lake Hongfeng, China. The Pu activity profile was in agreement with the 137Cs profile. Inventories were 50.7 Bq m(-2) for 239+240Pu and 1586 Bq m(-2) for 137Cs. The average 240Pu/239Pu atom ratio was 0.185+/-0.009, indicating that Pu originated from global stratospheric fallout rather than from direct tropospheric or close-in fallout from the Chinese nuclear testing conducted in the 1970s. Our data suggested that Lake Hongfeng would be an ideal setting for monitoring atmospheric fallout and environmental changes in this region.     

太湖地区“禁磷”措施的效果及在富营养化控制中的作用

通过太湖地区采取“禁磷”措施前后城市生活污水、主要入湖河水和湖体水域中磷浓度与富营养化指数变化的分析 ,证实“禁磷”措施对降低居民生活污水中磷浓度的作用较为明显 ,降幅为 2 4 %左右 ,但对入湖河道和湖体水域中磷浓度与水体富营养化的影响则不明显。表明太湖富营养化的改善 ,除了实施“禁磷”措施外 ,尚需结合流域内其它污染治理措施 ,进行综合治理 ,才能取得较好的效果。     

南漪湖沉积物磷的赋存形态及对上覆水的影响

以宣城市南漪湖为例,采用改进的无机磷分级提取方法对全湖共39个点位沉积物中磷(P)赋存形态进行系统研究,并分析其与上覆水体、间隙水等相互关系.结果表明,南漪湖水体磷污染水平已经处于高位,沉积物间隙水磷与上覆水体磷空间分布特征具有密切关系.南漪湖沉积物中总磷(TP)含量变化范围为463.3～1016.6mg/kg,其中各形态磷空间分布具有明显的差异性,与外源磷输入等密切相关.赋存形态含量大小、相对比例顺序依次为:钙结合态磷(Ca-P)>铁结合态磷(Fe-P)>铝结合态磷(Al-P)>还原剂可溶性磷(RS-P)>残渣态磷(Res-P)>弱吸附态磷(L-P).沉积物中TP含量与Fe-P、RS-P、Res-P极显著正相关,与L-P含量显著正相关.外源磷输入和水产养殖对南漪湖沉积物内源磷中Fe-P和RS-P贡献可能较大.南漪湖沉积物内源磷对上覆水体的潜在风险较高,其中生物有效性较高的L-P、Al-P、Fe-P和Rs-P的总和相对比例可达60%左右.沉积物中磷形态与间隙水磷浓度关系较密切,其中Al-P、Ca-P对间隙水中磷迁移转化具有重要影响.南漪湖主要出入湖河口沉积...     

南京南湖底泥疏浚后水质演化规律调查

对疏浚后的南京南湖底泥的TP、TN和COD释放规律、补水后的水质状况以及藻类演替规律进行了调查。结果表明,上覆水中TP平均质量浓度基本不随自来水补入量的增加而发生变化,TN和COD质量浓度随自来水补入量的增加而增大;水体中的TP、TN和COD含量总体呈上升趋势;从2005年3月中旬起,出现藻类的大量繁殖,在2005年7月发生水华,藻类优势种由裸藻、隐藻和小环藻演替为裸藻、栅藻和韦斯藻,藻类总量由2005年3月的3.7×106L-1上升到2006年4月的1.5×107L-1。     

喻家湖水质时空分布特征和影响因子分析

通过设计合理的水质监测网,采用多元统计分析,并结合地理信息技术对武汉市喻家湖在2011年-2012年期间12个监测点、13个水质参数监测值进行水质时空分布特征研究.结果表明,喻家湖13个水质指标概括为4个主成分:第一主成分代表喻家湖的重金属污染,第二主成分代表其富营养化水平,第三主成分代表有机污染程度,第四主成分间接指示富营养化程度;在时间和空间变化上都可分为二组,显著性指标的时空差异较明显,水质污染程度从南至北逐渐减弱,湖溪河是喻家湖的最主要污染源.并对水质参数,监测点位和频次进行了优化.     

阳澄湖浮游藻类现状调查及水质评价

对苏州阳澄湖2009年-2011年的浮游藻类现状进行调查,采用硅藻指数和Shannon-wiener指数两种生物学指数评价阳澄湖水体污染状况.结果表明,在阳澄湖发现浮游藻类219种(包括变种),秋季的浮游藻类种类数多于春季;阳澄湖水质尚好,东湖南富营养化程度较为严重.目前阳澄湖的有机污染处于缓慢上升的态势,富营养化水平也不断提高.     

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。