Further Development of a Specific Conductivity Approach to Measure Groundwater Discharge Area within Lakes

Groundwater exchanges with most lakes are rarely quantified because there are many technical challenges to quantification. We investigated a lakebed mapping approach to infer the relative areas of groundwater exchange in 12 prairie shallow lakes and five Laurentian mixed forest shallow lakes in Minnesota, USA in 2011. We used a relatively common approach (seepage meters) to provide baseline information on the magnitude and direction of flow at four locations in each lake. To expand from point measurements to the whole‐lake scale, we explored use of specific conductivity as a cheaper and more time efficient proxy for groundwater discharge to lakes. We validated the approach at near shore stations in each lake where seepage meter measurements and specific conductivity surveys overlapped. Specific conductivity surveys provided a similar assessment of groundwater discharge compared to seepage meters for 50% of the lake‐sampling period combinations. The lakebed mapping approach, when validated for a lake with a limited number of seepage meter (or alternative methods) measurements, offers the advantages of being more time and labor efficient over the use of a similar number of seepage meter monitoring locations; seepage meters (or piezometers, for example) are costlier in terms of equipment and labor, even for single‐lake studies. We show the combined approach could provide useful baselines for understanding and mapping groundwater exchange in shallow lakes.     

Chromatographic partitioning of impurities contained in a CO2 stream injected into a deep saline aquifer: Part 1. Effects of gas composition and in situ conditions

A series of laboratory experiments were carried out to examine the chromatographic partitioning of impurities contained in a stream of CO₂ injected into a deep saline aquifer. The experiments were carried out under static (no flow) and dynamic conditions, mainly with H₂S as the impurity in the CO₂ stream, for 2%, 5% and 30% concentrations, and for in situ conditions of high pressure, temperature and water salinity, and also for pure water at a lower pressure and temperature. In addition, experiments were conducted using CH₄, N₂ and SO₂ at 5% concentration as the ‘Impurity’ in the CO₂ stream. The experiments show that gases in an impure stream of CO₂ being injected into a deep saline aquifer will chromatographically partition at the leading edge of the gas advancing through the water-saturated porous medium as a result of differential solubility in aquifer water. The solubility of the impurity gas in the CO₂ stream compared to that of CO₂ is the most dominant factor in regard to the breakthrough time and initial gas concentrations in the effluent. The in situ conditions of pressure, temperature and water salinity also affect the chromatographic partitioning of CO₂ and impurities contained in the injection stream through their general effect on the solubility of all gases. The concentration of the impurity gas in the feed gas stream has a secondary effect on the breakthrough and time lag decreasing with increasing concentration of the impurity gas. These experimental findings are significant for understanding the fate of the injected CO₂ and associated impurities contained in an injection stream, in devising monitoring procedures and protocols, and in developing emergency response plans in case of leakage of CO₂ and associated impurities.     

Whole effluent assessment of industrial wastewater for determination of bat compliance

Background, aim and scope  

The applicability of the Whole Effluent Assessment concept for the proof of compliance with the “best available techniques” has been analysed with paper mill wastewater from Germany by considering its persistency (P), potentially bio-accumulative substances (B) and toxicity (T).     

Identification of trail pheromone compounds from the labial glands of the stingless bee Geotrigona mombuca

Foragers of several species of stingless bees deposit pheromone spots in the vegetation to guide recruited nestmates to a rich food source. Recent studies have shown that Trigona and Scaptotrigona workers secrete these pheromones from their labial glands. An earlier report stated that species within the genus Geotrigona use citral from their mandibular glands for scent marking. Since convincing experimental proof for this conjecture is lacking, we studied the glandular origin of the trail pheromone of Geotrigona mombuca. In field bioassays, newly recruited bees were diverted by artificial scent trails that branched off from the natural scent trail deposited by their nestmates only when they were baited with extracts from the foragers’ labial glands. Compounds extracted from the mandibular glands, however, did not release trail following behavior. This demonstrates that the trail pheromone of G. mombuca is produced in the labial glands, as in Trigona and Scaptotrigona. Furthermore, in chemical analyses citral was identified exclusively in the foragers’ mandibular glands, which disproves its supposed role as a trail pheromone. The labial glands contained a series of terpene- and wax type esters, with farnesyl butanoate as major constituent. We, therefore, postulate that the trail pheromone of G. mombuca is composed of a blend of esters.     

Understanding the impact of hydropower developments in the context of upstream–downstream relations in the Mekong river basin

Hydropower developments along the main stem of the Mekong River and its tributaries cause transboundary effects within the Mekong Basin Region, which comprises parts of six countries. On the one hand, the provision of hydropower triggers economic development and helps to meet the rising energy demand of the Mekong riparian countries, especially China, Thailand, and Vietnam. On the other hand, the negative impact of dam construction, mainly altered water flow and sediment load, has severe impacts on the environment and the livelihoods of the rural Mekong population. Several discrepancies exist in the needs, demands, and challenges of upstream versus downstream countries. Against the common apprehension that downstream countries are powerlessly exposed to mainly negative impacts whereas upstream countries unilaterally benefit from hydropower, the authors argue that upstream–downstream relations are not really clear-cut. This conclusion is based on a consideration of the complex power play between Mekong riparians, with a focus on recent power trade interactions. The article investigates the consequences of hydropower dams for the Mekong region as well as the role of supranational players, such as the Mekong River Commission and the Greater Mekong Subregion Initiative, on the hydropower debate. It is not nations that are the winners or losers in the hydropower schemes in the Mekong, but rather parts of the riparian population: a few influential and powerful elites versus the large mass of rural poor.     

Absch?tzung des Beitrages kommunaler Kl?ranlagen an Schadstoffkonzentrationen in Oberfl?chengew?ssern

Eine Reihe von Produkten wie Waschmittel oder Humanpharmaka gelangen haupts?chlich über kommunale Abw?sser in die Hydrosph?re. Die zu erwartenden Umweltkonzentrationen (PEC) solcher Stoffe werden von der Eliminationleistung der Kl?ranlagen und den Verdünnungsverh?ltnissen in den Vorflutern bestimmt. In diesem Beitrag werden überschl?gige Berechnungen zum Abwasseranteil in deutschen Flie?gew?ssern vorgestellt und Ans?tze für ein komplexeres Modell zur Berechnung der PEC unter Berücksichtigung des Abflu?regimes (Hoch- und Niedrigwasserabflüsse) aufgezeigt.     

Modeling thermoelectric power generation in view of climate change: a comment

Numerous power plants in Europe had to be throttled in summer months of the years 2003 and 2006 due to water shortages and high water temperatures caused by a hot and dry summer. Therefore, the effects of higher temperatures on power plants have received much attention in the last years. One article published in Regional Environmental Change presents a study about ‘Modeling thermoelectric power generation in view of climate change’. In this article, the statement is given that other studies do not include aspects as environmental legislation or cots of water shortages. This comment will show that in at least one article cited these aspects are considered.