Search

With the climate warming leading to thawing permafrost, the trace metal releasing from the permafrost is of increasing importance. The source area of the Yellow river (SAYR) in Tibet Plateau, underlain by permafrost which provides important source water, was investigated. One hundred and eleven water samples across SAYR were collected in April 2014, when permafrost thawing began and the precipitation season had not arrived yet. It was found that the arsenic concentration level was relatively higher than other pristine surface water in the world, but similar to other source regions on the Tibetan Plateau, showing SAYR is pristine and can serve as a reference region for determining the human influence on permafrost-affected landscapes. The positive correlation of arsenic with sulfate suggested that the arsenic was predominantly derived from the weathering process of arsenic-rich sulfides. Climate warming enhanced thawing depth of permafrost may accelerate the release and mobilization of arsenic to the surface water. [ABSTRACT FROM AUTHOR]

The differences between δ18O and δ2H in throughfall and open rainfall were studied for a selected typhoon event in a watershed within the Taihu Lake drainage basin, eastern China. In this event, the isotopic composition of precipitation exhibited a strong temporal variation. Comparison results show that an isotopic composition difference existed not only between gross rainfall and average incremental rainfall, but also between different calculation methods used to derive average. The differences between incremental precipitation and throughfall isotopic composition were observed in this study. Considering the temporal variation in rainfall and throughfall during this typhoon event, the incremental value can have an effect on hydrograph separation more accurately in evaluating the importance of ‘new’ water. In addition, isotopic fluctuations of surface water and groundwater differed from those of rainfall and throughfall throughout the event. [ABSTRACT FROM PUBLISHER]

Contaminated sediments, as a secondary pollution source in rivers and lakes, are of critical importance to water quality. More and more attention thus has been paid to understand the release mechanisms of nutrients from river sediments, especially in estuary and water transfer areas. In this work, flume experiments were conducted to measure the release characteristics of total dissolved phosphorus (TDP) and nitrogen (TDN) from sediments collected from a river bed near Lake Tai under various flow conditions. The release of TDP and TDN was the most dramatic in the initial 30 min, then slowed down from 30 to 60 min, and finally achieved equilibria. Total amount of TDP and TDN released and their equilibrium concentrations were all significantly increased with the increase of flow rate, but slow down after a critical velocity was reached, which could be described as a Logarithmic relationship. A process-based mathematical model was established to describe the distribution of nutrients in the water columns and model simulations matched experimental data well. The re-suspension of sediments induced by flow rate higher than the threshold, is the dominant process affecting nutrient release from sediments. [ABSTRACT FROM PUBLISHER]

In order to investigate the effects of macrobenthos on the abundance and community composition of ammonia-oxidizing prokaryotes under different temperature conditions, laboratory microcosms containing two kinds of macrobenthos (Corbicula flumineaandTubificidworms) were constructed. Real-time polymerase chain reaction (PCR) and clone libraries were applied to analyze the ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities in the surface sediments. The lowest abundances of the archaeal and bacterialamoAgene were found in the samples cultured under 28 °C (archaealamoAgene abundance, 2.71 × 106copies/g dry sediment; bacterialamoAgene abundance, 1.17 × 107copies/g dry sediment) of theC. flumineagroup. However, there was no significant difference in terms of the abundance of archaealamoAgene in allTubificidworms treatment groups. Compared to the community composition of AOB, greater variations in the community composition of AOA were observed among the three different temperature groups. [ABSTRACT FROM PUBLISHER]

Ammonium oxidation is both the first and a rate-limiting step in the nitrification process that can be catalysed by ammonia-oxidizing archaea (AOA) or ammonia-oxidizing bacteria (AOB). In this study, the abundance and community composition of AOA and AOB in the rhizosphere sediments of two submerged macrophytes (Ceratophyllum demersumandPotamogeton malainus) were investigated. Physicochemical parameters, including pH, total nitrogen, total phosphorus, ammonia nitrogen, nitrate and organic matter, were measured. The number of copies of both the archaeal and bacterialamoAgene was quantified by real-time PCR and clone libraries were constructed for both AOA and AOB. The abundance of archaealamoAgene ranged from 3.83 × 106to 4.23 × 106copies per gram of dry sediment and no significant difference was found among the three treatment groups (one control group and two submerged macrophyte groups). The abundance of bacterialamoAgene ranged from 2.68 × 106to 8.05 × 107copies per gram of dry sediment. Bulk sediment maintained significantly higher copy numbers of bacterialamoAgene than those ofC. demersumrhizosphere sediment. The diversity of archaealamoAgene was higher in the rhizosphere sediment ofC. demersum; however, the diversity of bacterialamoAgene was relatively lower in rhizosphere sediment of both macrophytes. [ABSTRACT FROM PUBLISHER]

Copyright of Hydrological Sciences Journal/Journal des Sciences Hydrologiques is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Spatial and temporal changes of the benthic macroinvertebrate (BMI) community composition and secondary production provide valuable information about the current ‘health’ of aquatic systems. We analyzed seasonal and inter-annual changes in BMI communities at five sites along an elevation and land use gradient in the Walker River, NV, USA. In addition, bimonthly collections ofBaetismayflies were made at two sites to assess the effect of nutrient enrichment onBaetissecondary production. BMI community composition changed spatially and temporally in response to the physicochemical environment. BMI diversity was positively correlated to substrate size and stream width but negatively correlated with stream temperature and organic pollutants. Cluster analysis based on BMI community composition revealed a similar community structure along the river, except at one site which was located below the outflow of a eutrophic reservoir. The BMI community in the river was dominated by collector–gatherers while shredders were absent through most of the downstream and impaired sites. Secondary production ofBaetiswas almost twice as high at the nutrient-enriched site (1.3 g dry mass m−2yr−1) than at the undisturbed site (0.7 g m−2yr−1), most likely the consequence of warmer water temperatures and superior food quality. Results from this study imply that a variety of anthropogenic activities have altered disparate reaches of the Walker River and that BMI community composition would change towards natural conditions with an increase in discharge and reduced water temperature and nutrients. This work also underscores the importance of considering biotic indices and secondary production to effectively assess stream ecosystem health and to design successful restoration strategies. [ABSTRACT FROM AUTHOR]

Climate change is expected to impact water quality and ecosystem health in water bodies. In this study, a modeling framework was developed to assess the response of environmental variables to climate change scenarios in Lake Taihu, China. A coupled hydrodynamic-water quality-sediment flux model was employed to simulate water quality processes under future climate scenarios projected from a general circulation model (GCM) forced by the Representative Concentration Pathway 8.5 (RCP 8.5). The results showed that the climate change impacted physico-chemical parameters and biological interactions in Lake Taihu. The annual average water temperature increased by 0.96, 2.09, and 3.2 °C by the 2020s, 2050s, and 2080s, respectively. Daily temperature stratification tended to occur earlier and the period of stratification increased, especially in summer during calm wind conditions. The sediment flux increased and dissolved oxygen (DO) concentration decreased with climate change. Additionally, climate change increased the onset time, duration, and areas of algal blooms. The results showed that the blooms activation time advanced approximately six days per decade. The onset time of algal blooms of 2080s was in February and March and the elevated concentration of chlorophyll a lasted until late autumn in the west lake region. The chlorophyll a concentration in summer did not increase substantially (about 10–15 μg/L). Overall, water management strategies and ecological restoration plans in Lake Taihu, mainly based on nutrient load reduction and hydrodynamic modification, should incorporate anticipated effects of climate change. [ABSTRACT FROM AUTHOR]