Passing volume calculation system (PVCS): computer software for managing data on watersheds that produce mud flows and the case of Quebrada La Cadena,Antofagasta, Chile

Severe storms in desert regions, especially along the coastal area of the Chilean desert, produce very destructive mud flows that last a few hours and constitute the only surface run-off in these events. To date, there is no simple or practical methodology for assessing such mud flows. Given the settlement of mining fields and creation of desert campgrounds, it is increasingly necessary to understand how these water and/or mud flows behave in order to develop structural and non-structural mitigation plans. Thus, herein, we present software known as PVCS, which provides a system for calculating mud volumes after a strong storm. This hydrological and computer tool allows us to calculate the structure and volume of mud passing through the mouth of a hydrographic watershed after a desert rainstorm. To use this software, it is necessary to know the hydrological, meteorological, and morphometric parameters of the watershed under study. These data are entered into a model that estimates the amount of mud that will pass through the mouth with each hour of rain. Simulations can be done with historical data or data designed for future events, thereby allowing the preparation of measures to protect people and property. We use the watershed Quebrada La Cadena to exemplify the use of this software. This drainage basin is located on the western slope of the Chilean Coastal Range in Antofagasta, a city in northern Chile. Here, rain in June 1991 produced a destructive flood that killed nearly one hundred people living at the main mouth of the watershed and caused huge economic losses. Data from this catastrophe have significantly improved the understanding of such flows, and this has been incorporated into the software. The principal value of PVCS lies in its ability to forecast the volume of mud that will result from a storm and hourly outflows that will pass through a specific populated area, mining camp, or industrial plant located in the mouth of a watershed of any size. This information is used to determine the most critical moment, i.e., the time of the largest outflows, which can then be used to organize timely evacuations to safe places for people, animals, and machines. Moreover, the program is methodologically valuable since, in order to implement PVCS, the user must structure information in a hydrological way. In summary, this program simulates different rain scenarios, thereby allowing us to design structural mitigation projects and contingency plans.     

Temporal Changes in Seawater Carbonate Chemistry and Carbon Export from a Southern California Estuary

Estuaries are important subcomponents of the coastal ocean, but knowledge about the temporal and spatial variability of their carbonate chemistry, as well as their contribution to coastal and global carbon fluxes, are limited. In the present study, we measured the temporal and spatial variability of biogeochemical parameters in a saltmarsh estuary in Southern California, the San Dieguito Lagoon (SDL). We also estimated the flux of dissolved inorganic carbon (DIC) and total organic carbon (TOC) to the adjacent coastal ocean over diel and seasonal timescales. The combined net flux of DIC and TOC (F_DIC?+?TOC) to the ocean during outgoing tides ranged from ??1.8±0.5?×?10³ to 9.5±0.7?×?10³?mol C h^?1 during baseline conditions. Based on these fluxes, a rough estimate of the net annual export of DIC and TOC totaled 10±4?×?10⁶?mol C year^?1. Following a major rain event (36 mm rain in 3 days), F_DIC?+?TOC increased and reached values as high as 29.0 ±?0.7?×?10³?mol C h^?1. Assuming a hypothetical scenario of three similar storm events in a year, our annual net flux estimate more than doubled to 25 ±?4?×?10⁶?mol C year^?1. These findings highlight the importance of assessing coastal carbon fluxes on different timescales and incorporating event scale variations in these assessments. Furthermore, for most of the observations elevated levels of total alkalinity (TA) and pH were observed at the estuary mouth relative to the coastal ocean. This suggests that SDL partly buffers against acidification of adjacent coastal surface waters, although the spatial extent of this buffering is likely small.     

Interspecific introgression and changes in population structure in a flatfish species complex after the Prestige accident

Oil spills cause aggressive impacts on marine ecosystems affecting immense areas and the species inhabiting them. If wastes are not cleaned up properly, the remnants may affect local populations for a long time. This work focuses on the long-term impacts of the Prestige spillage that occurred off Galician coast (Spain) in November 2002. Model species were two sympatric flatfish, the megrims Lepidorhombus whiffiagonis and Lepidorhombus boscii. Samples obtained before and nine years after the Prestige accident from affected and unaffected areas were genotyped for six hypervariable nuclear markers and for the mitochondrial D-loop sequence. The results revealed a high proportion of post-F1 interspecific hybrids in the area affected, and also increased intraspecific population differentiation likely due to such localized introgression of foreign genes. These changes suggest the appearance of a hybrid zone following the accident and emphasize the need of paying special attention to potential evolutionary impacts of oil spills.     

Hazardous gas emissions from the flanks of the quiescent Colli Albani volcano (Rome,Italy)

Gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent Colli Albani volcano. These zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth. All extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells. The gas, mainly composed of CO₂ (>90 vol.%), contains appreciable quantities of H₂S (0.35–6 vol.%), and both represent a potentially high local hazard. Both gases are denser than air and accumulate near ground where they may reach hazardous concentrations, and lethal accidents frequently occur to animals watering at local ponds. In order to evaluate the rate of degassing and the related hazard, CO₂ and H₂S diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber. The viscous gas flux of some important discrete emissions has been evaluated and the CO₂ and H₂S air concentration measured by portable devices and by Tunable Diode Laser profiles. The minimum potential lethal concentration of the two gases (250 ppm for H₂S and 8 vol.% for CO₂) is 320 times higher for CO₂, whereas the CO₂/H₂S concentration ratio in the emitted natural gas is significantly lower (15–159). This explains why H₂S reaches hazardous, even lethal, concentrations more frequently than CO₂. A relevant hazard exists for both gases in the depressed zones (channels, excavations) particularly in the non-windy early hours of the day.     

Hydrothermal alteration,fluid inclusions and stable isotope systematics of the Alvo 118 iron oxide–copper–gold deposit,Carajás Mineral Province (Brazil): Implications for ore genesis

The Alvo 118 iron oxide–copper–gold (IOCG) deposit (170 Mt at 1.0 wt.% Cu, 0.3 g/t Au) lies in the southern sector of the Itacaúnas Shear Belt, Carajás Mineral Province, along a WNW–ESE-striking, 60-km-long shear zone, close to the contact of the ~2.76-Ga metavolcano-sedimentary Itacaiúnas Supergroup and the basement (~3.0 Ga Xingu Complex). The Alvo 118 deposit is hosted by mafic and felsic metavolcanic rocks and crosscutting granitoid and gabbro intrusions that have been subjected to the following hydrothermal alteration sequence towards the ore zones: (1) poorly developed sodic alteration (albite and scapolite); (2) potassic alteration (biotite or K-feldspar) accompanied by magnetite formation and silicification; (3) widespread, pervasive chlorite alteration spatially associated with quartz–carbonate–sulphide infill ore breccia and vein stockworks; and (4) local post-ore quartz–sericite alteration. The ore assemblage is dominated by chalcopyrite (~60%), bornite (~10%), hematite (~20%), magnetite (10%) and subordinate chalcocite, native gold, Au–Ag tellurides, galena, cassiterite, F-rich apatite, xenotime, monazite, britholite-(Y) and a gadolinite-group mineral. Fluid inclusion studies in quartz point to a fluid regime composed of two distinct fluid types that may have probably coexisted within the timeframe of the Cu–Au mineralizing episode: a hot (>200°C) saline (32.8‰ to 40.6 wt.% NaCl eq.) solution, represented by salt-bearing aqueous inclusions, and a lower temperature (<200°C), low to intermediate salinity (<15 wt.% NaCl eq.) aqueous fluid defined by two-phase (L_H2O + V_H2O) fluid inclusions. This trend is very similar to those defined for other IOCG systems of the Carajás Mineral Province. δ ¹⁸O_H2O values in equilibrium with calcite (−1.0‰ to 7.5‰ at 277°C to 344°C) overlap the lower range for primary magmatic waters, but the more ¹⁸O-depleted values also point to the involvement of externally derived fluids, possibly of meteoric origin. Furthermore, sulphide δ ³⁴S values (5.1‰ to 6.3‰), together with available boron isotope and Cl/Br–Na/Cl data provide evidence for a significant component of residual evaporative fluids (e.g., bittern fluids generated by seawater evaporation) in this scenario that, together with magma-derived brines, would be the main sources of the highly saline fluids involved in the formation Alvo 118 IOCG deposit. The restricted high temperature sodic alteration, the pervasive overprinting of the potassic alteration minerals by chlorite proximal to the ore zones, ore breccias with open-space filling textures in brittle structures, microthermometric and stable isotope data indicate, collectively, that the Alvo 118 IOCG system developed at structurally high levels and may be considered the shallower representative of the IOCG systems of the CMP.     

Assessment of perfluorinated compounds (PFCs) in plasma of bottlenose dolphins from two southeast US estuarine areas: relationship with age, sex and geographic locations

Plasma PFCs were measured in 157 bottlenose dolphins (Tursiops truncatus) sampled from two US southeast Atlantic sites (Charleston (CHS), SC and Indian River Lagoon (IRL), FL) during 2003-2005. ∑PFCs, perfluoroalkyl carboxylates (∑PFCAs), perfluoroalkyl sulfonates (∑PFSAs) and individual compounds were significantly higher in CHS dolphins for all age/sex categories compared to IRL dolphins. Highest ∑PFCs concentrations occurred in CHS juvenile dolphins (2340 ng/g w.w.); significantly higher than found in adults (1570 ng/g w.w. males; 1330 ng/g w.w. females). ∑PFCAs were much greater in CHS dolphins (≈ 21%) compared to IRL dolphins (≈ 7%); ∑PFSAs were 79% in CHS dolphins versus 93% in IRL dolphins. PFOS, the dominant compound, averaged 72% and 84%, respectively, in CHS and IRL dolphins. Decreasing PFC levels occurred with age on the bioaccumulation of PFCs in both sites. These observations suggest PFC accumulation in these two dolphin populations are influenced by site-specific exposures with significantly higher levels in CHS dolphins.     

Evaluating the SWAT's snow hydrology over a Northern Quebec watershed

The snow treatment becomes an important component of Soil and Water Assessment Tool (SWAT)’s hydrology when spring flows are dominated by snow melting. However, little is known about SWAT's snow hydrology performance because most studies using SWAT were conducted in rainfall‐driven catchments. To fill this gap, the present study aims to evaluate the ability of SWAT in simulating snow‐melting‐dominated streamflow in the Outardes Basin in Northern Quebec. SWAT performance in simulating snowmelt is evaluated against observed streamflow data and compared to simulations from the operationally used Streamflow Synthesis and Reservoir Regulation (SSARR) model over that catchment. The SWAT 5‐year calibration showed a satisfactory performance at the daily and seasonal time scales with low volume biases. The SWAT validation was conducted over two (17‐year and 15‐year) periods. Performances were similar to the calibration period in simulating the daily and seasonal streamflows again with low model biases. The spring‐snowmelt‐generated peak flow was accurately simulated by SWAT both in magnitude and timing. When SWAT's results are compared to SSARR, similar performances in simulating the daily discharges were observed. SSARR simulates more accurately streamflow generated at the snowmelt onset whereas SWAT better predicts streamflow in summer, fall and winter. SWAT provided reasonable streamflow simulations for our snow‐covered catchment, but refinement of the process‐driven baseflow during the snowmelt onset could improve spring performances. Therefore, SWAT becomes an attractive tool for evaluating water resources management in Nordic environments when a distributed model is preferred or when water quality information (e.g. temperature) is required. Copyright © 2013 John Wiley & Sons, Ltd.     

An optimized use of limited ground based topographic data for river applications

A prime requirement for hydrological applications,such as sediment budgeting or numerical modelling,is that produced Digital Terrain Models(DTMs)accurately represent the shape of landforms,especially for river reaches where data are not homogeneous.DTM error is a function of data point measurement accuracy and density and also of the field survey strategy when limited amounts of data will be acquired.This paper aims to advance the importance of the field survey strategy for the specific,but common cases,where only limited topographic data will be available.This methodology is based on the idea that any feature can be properly described by a set of cross sections and breaklines describing both main and secondary directions of the flow.Then,a longitudinal linear interpolation can be applied to the defined homogeneous zones.This morphologically oriented(MO)method that includes data acquisition strategy and interpolation,was validated using a reference DTM derived from LiDAR measurements.An estimation of the uncertainties also is suggested based on the distance of the nearest point and the local slope using a geographically weighted regression.The proposed MO method is typically applicable to Alpine river reaches characterized by multiple channels that may always be underwater and not navigable such as an alternate bar system with secondary and transverse channels.     

Effective Accuracy of Satellite-Derived Hourly Irradiances

Summary  Estimates of hourly global irradiance based on geostationary satellite data with a resolution of several (2 to 10) kilometres reproduce ground-measured values with a Root Mean Square Error (RMSE) of typically 20% to 25%. The different components of this RMSE have been enumerated by several authors but, due to the lack of adequate measurements, their respective importance is not well settled. In the present study we attempt to quantify these components from a practical point of view, that is from the point of view of users having to rely on time/site specific irradiance data. We conclude that the intrinsic, or “effective” RMSE is more along the line of 12%. This effective RMSE is the measure of the methodological imprecision (satellite-to-irradiance conversion models). The remaining part of the overall RMSE is the amount by which spatially averaged satellite-derived estimates are, by their very nature, bound to differ from ground-measured local insolation. Received August 15, 1997 Revised March 4, 1998     

Land use and the spatial distribution of perfluoroalkyl compounds as measured in the plasma of bottlenose dolphins (Tursiops truncatus)

The distribution of perfluoroalkyl compounds (PFCs) in the environment is well documented with higher concentrations observed in wildlife located in industrial and urban areas. This study examined the distribution of PFCs in relation to land use using blood samples collected from bottlenose dolphins during capture-release health assessment surveys conducted in Charleston, SC. The study area was partitioned into three subareas (ACW, CHS, and SRE) based upon habitat and land use characteristics. The ACW and CHS subareas are characterized by high degrees of industrial and urban land uses, while the SRE subarea is more residential and characterized by a lower degree of developed land use. Long-term monitoring data from photo-identification surveys were used to group bottlenose dolphins based on their proportions of sightings in the different subareas. Dolphins affiliated with both the ACW and CHS subareas were observed to have significantly higher mean plasma concentrations of perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid (PFUnA) than those affiliated with the SRE subarea. Dolphins affiliated with the ACW subarea were found to have a significantly higher mean plasma concentration of PFUnA than those affiliated with the CHS subarea. Further examination of the distribution of the PFCs revealed positive correlations with developed land uses and negative correlations with wetland/marsh land cover. A positive correlation was also observed between PFUnA and agricultural land use. The variability and scale of the observed contaminant burdens have important implications for the conservation and management of living marine resources and illustrates the importance of long-term monitoring of free-ranging wildlife species.