Cyanotoxin contamination of semiarid drinking water supply reservoirs

Changing global climatic conditions and the continuous eutrophication of aquatic ecosystems have led to increased frequency, duration and toxicity of cyanobacterial blooms worldwide. This makes the provision of time series information on cyanotoxins extremely crucial for effective monitoring and management of water resources. The objective of the present study was to investigate seasonal and annual changes in microcystins (MCs), cylindrospermopsins (CYNs), saxitoxins (STXs), neo-saxitoxin (neo-STX) and anatoxin-a (ATX-a) concentrations in 11 public water supply reservoirs in the semiarid region of Brazil, from 2004 to 2011. Per time, at least one cyanotoxin was present in all the investigated reservoirs. High levels of MCs, CYNs, STXs and Neo-STX were detected simultaneously in Carpina, Duas Unas, Ipojuca, and Jucazinho reservoirs. All the investigated reservoirs had significant concentrations of MCs. The highest levels of MCs were found in Carpina (303,300.0 ng g^?1) and Duas Unas (122,053.9 ng g^?1) reservoirs, while the lowest concentration of the hepatotoxins was recorded in Ipojuca (10.3 ng g^?1) reservoir. On the other hand, CYN was detected in four reservoirs, STXs and Neo-STX in ten reservoirs and ATX-a in two reservoirs. The first record of CYN in Carpina reservoir was obtained in 2006. In addition, Carpina reservoir had the highest concentration of STXs and Neo-STX in the dry and rainy seasons, respectively. The high concentration of cyanotoxins observed in most samples obtained from semiarid reservoirs in Brazil demonstrates the need for regular monitoring and updated management programs.     

Automatic determination of 3D orientations of fossilized oyster shells from a densely packed Miocene shell bed

International Journal of Earth Sciences - Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to...     

Modeling Geospatial Uncertainty of Geometallurgical Variables with Bayesian Models and Hilbert–Kriging

Mathematical Geosciences - In mine planning, geospatial estimates of variables such as comminution indexes and metallurgical recovery are extremely important to locate blocks for which the energy...     

灌区水资源合理配置研究进展

灌区水资源合理配置是提高灌区水资源利用效率及保障粮食安全的重要途径,也是实现灌区水资源可持续利用的有效调控措施。从灌区水资源管理政策、水资源循环转化规律、水资源优化配置模型与方法和水文生态4个方面,对国内外该领域的研究现状进行了对比分析。研究发现,国内灌区水资源配置主要存在4个方面的问题:水资源合理配置与保护政策落实不到位、水资源的统一管理机制不健全、水资源优化配置模型实用性不强和水资源优化配置基础条件较为薄弱。建议加强灌区水资源的统一管理政策与机制、变化环境下水资源循环转化规律、水资源承载力基础理论与评价新方法、水文生态调控技术、水资源实时风险调度与智能化管理技术以及水资源优化配置耦合技术研究。     

Comment on: “Corrections to the Mathematical Formulation of a Backwards Lagrangian Particle Dispersion Model” by Gibson and Sailor (2012: Boundary-Layer Meteorology 145, 399–406)

We discuss the results of Gibson and Sailor (Boundary-Layer Meteorol 145:399–406, 2012) who suggest several corrections to the mathematical formulation of the Lagrangian particle dispersion model of Rotach et al. (Q J R Meteorol Soc 122:367–389, 1996). While most of the suggested corrections had already been implemented in the 1990s, one suggested correction raises a valid point, but results in a violation of the well-mixed criterion. Here we improve their idea and test the impact on model results using a well-mixed test and a comparison with wind-tunnel experimental data. The new approach results in similar dispersion patterns as the original approach, while the approach suggested by Gibson and Sailor leads to erroneously reduced concentrations near the ground in convective and especially forced convective conditions.     

Depositional history of the Miocene Lake Sinj (Dinaride Lake System,Croatia): a long-lived hard-water lake in a pull-apart tectonic setting

Early Miocene transpressional wrenching yielded a series of NW–SE-elongated pull-apart basins in the Dinarides of Croatia and Bosnia and Herzegovina. They accommodated a huge lake system that gave rise to spectacular endemic mollusk radiation. Lake Sinj, moderately sized at 342 km², flooded the south-westernmost basin of this system. Due to the karstic environment, the hard-water, alkaline, long-lived lake developed a sediment infill with an average thickness of 370 m, dominated by authigenic limestone. The studied section represents the upper third of the basinal infill and provides detailed insights into the critical period of the lake and of the basinal evolution during the final stages of its filling. It comprises two large-scale, shallowing-upward cycles, both starting with fossil-poor limestones, gradually passing into coal-bearing carbonate rocks and coal seams. The fossil-poor intervals are interpreted as phases of repetitive acidification events due to changing lake level, which induced periodic drying and flooding of the uppermost littoral zone inhabited by starfruit (Damasonium) meadows. The flooding of the aerated, limy mud plain introduced H+ ions from organic-matter decay reactions into the shallow lake. This decreased its pH level, with catastrophic consequences for its biota. The ecosystem then stabilized during the orbitally-forced, dry climate phases. Based on the mollusk record, streams still influenced the marginal lake environment and rich organic-matter production created swamps and mires. The onset of mollusk radiation in the section correlates with stabilized lake alkalinity, as indicated by the disappearance of starfruits, ongoing authigenic carbonate production and by coal seams representing textbook examples for coal formation in alkaline environments. The inferred basinal setting fits well with the pull-apart basin model, pointing to the presence of an extended shallow ramp in front of a steep, fault-induced hillside of the hinterland.     

Channel response to sediment release: insights from a paired analysis of dam removal

Dam removals with unmanaged sediment releases are good opportunities to learn about channel response to abruptly increased bed material supply. Understanding these events is important because they affect aquatic habitats and human uses of floodplains. A longstanding paradigm in geomorphology holds that response rates to landscape disturbance exponentially decay through time. However, a previous study of the Merrimack Village Dam (MVD) removal on the Souhegan River in New Hampshire, USA, showed that an exponential function poorly described the early geomorphic response. Erosion of impounded sediments there was two‐phased. We had an opportunity to quantitatively test the two‐phase response model proposed for MVD by extending the record there and comparing it with data from the Simkins Dam removal on the Patapsco River in Maryland, USA. The watershed sizes are the same order of magnitude (10² km²), and at both sites low‐head dams were removed (~3–4 m) and ~65 000 m³ of sand‐sized sediments were discharged to low‐gradient reaches. Analyzing four years of repeat morphometry and sediment surveys at the Simkins site, as well as continuous discharge and turbidity data, we observed the two‐phase erosion response described for MVD. In the early phase, approximately 50% of the impounded sediment at Simkins was eroded rapidly during modest flows. After incision to base level and widening, a second phase began when further erosion depended on floods large enough to go over bank and access impounded sediments more distant from the newly‐formed channel. Fitting functional forms to the data for both sites, we found that two‐phase exponential models with changing decay constants fit the erosion data better than single‐phase models. Valley width influences the two‐phase erosion responses upstream, but downstream responses appear more closely related to local gradient, sediment re‐supply from the upstream impoundments, and base flows. Copyright © 2017 John Wiley & Sons, Ltd.     

Subglacial abrasion rates at Goldbergkees,Hohe Tauern,Austria, determined from cosmogenic 10Be and 36Cl concentrations

We report concentrations of cosmogenic ¹⁰Be and ³⁶Cl used to determine erosion depths in the recently deglaciated bedrock at Goldbergkees in the Eastern Alps. The glacier covered the sampling sites during the Little Ice Age (LIA) until c. 1940. The youngest ages calculated from these concentrations match the known exposure time after the post‐LIA exposure of <100 years. The apparent age (no cover, no erosion) of most samples, however, is significantly older. We show that the measured nuclide concentrations represent subglacial erosion depths, rather than exposure times. In particular, erosion depths calculated using ¹⁰Be and ³⁶Cl concentrations of individual samples match well, whereas apparent ³⁶Cl ages are consistently older than ¹⁰Be ages. The bedrock at the ‘youngest’ surfaces was deeply eroded (≥ 297 cm) by the Goldbergkees during the late Holocene. In contrast, bedrock at the margin of the LIA ice extent was eroded ≤35 cm. These values convert to subglacial erosion rates on the order of 0.1 mm/a to >5 mm/a. While modeled erosion rates depend on the duration of glacial cover and erosion intrinsic to the different exposure scenarios used for calculation (700–3300 years), modeled total erosion depths are insensitive (5–20% change). Analysis of erosion depths on the transverse valley profile shows a general trend of greatest erosion part way up the valley side and less erosion under thin ice at the lateral margin. A second profile along the valley axis indicates depth of erosion is greatest where the ice abuts the foot of the investigated bedrock riegel and at its lee side just beyond the crest. Copyright © 2016 John Wiley & Sons, Ltd.