How do early successional patterns in man-made wetlands differ between cold temperate and Mediterranean regions?

The early stages of succession in newly created wetlands should be impacted by the region in which the wetland is located, since climate may have filtered the dominant biological strategies of the taxa leading this process and may condition their dynamics. We studied the early successional patterns of macroinvertebrates within man made ponds, located in cold temperate (Scandinavian Peninsula) and Mediterranean regions (Iberian Peninsula), during the first three years following their creation. We predicted (1) non random subsets of the regional species pool (deterministic assembly) guiding the successional process in cold temperate wetlands, and random (stochastic) assembly in the Mediterranean region; (2) higher successional rates in Mediterranean ponds than in the cold temperate ponds, with contrary episodes of highest and lowest change throughout the year; and (3) a significant difference in the composition of biological traits between regions, due to the dominance of traits adapted to hydrological variability in the Mediterranean region. Hypotheses on community structure (1) and the composition of dominant biological traits (3) were mostly supported – deterministic assembly mechanisms in the cold temperate ponds and stochastic assembly in the Mediterranean ponds; and a dominance of different biological traits between regions, explained by the need to overcome hydrological disturbances in the Mediterranean ponds. The dynamics of succession (2) were explained by climatic factors in the cold temperate region but not in the Mediterranean ponds. We suggest that the intrinsic hydrological variability of Mediterranean lentic systems may be a major factor driving community changes in man-made wetlands in this region. In order to generalize the observed patterns, we performed a meta-analysis of the temporal trends of taxonomic distinctness parameters of other successional studies across a latitudinal gradient in Europe, which supported the differences we had observed between latitudinal extremes.     

Estimates of lifetimes against pitch angle diffusion

We consider timescales on which particle distributions respond to pitch angle diffusion. On the longest timescale, the distribution decays at a single rate independent of equatorial pitch angle α₀, even though the diffusion coefficient, and the distribution itself, may vary greatly with α₀. We derive a simple integral expression to approximate this decay rate and show that it gives good agreement with the full expression. The roles of both the minimum and loss cone values of the diffusion coefficient are demonstrated and clarified.     

Development and testing of a new protocol for evaluating the effectiveness of oil spill surface washing agents

As defined by the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), a surface washing agent (SWA) is a product that removes oil from solid surfaces, such as beaches, rocks, and concrete, through a detergency mechanism and that does not involve dispersing or solubilizing the oil into the water column. Commercial products require testing to qualify for listing on the NCP Product Schedule. Such testing is conducted both for toxicity and effectiveness. Protocols currently exist for bioremediation agents and dispersants, but not SWAs. The US Environmental Protection Agency (EPA) is developing a laboratory testing protocol to evaluate the effectiveness of SWAs in removing crude oil from a solid substrate. This paper summarizes some of the defining research supporting this new protocol. Multiple variables were tested to determine their effect on SWA performance. The protocol was most sensitive to SWA-to-oil ratio and rotational speed of mixing. Less sensitive variables were contact time, mixing time, and SWA concentration when total applied mass of active product was constant. EPA recommendations for the testing protocol will be made following round robin testing.     

Electrical Resistivity Characterization of Anisotropy in the Biscayne Aquifer

Electrical anisotropy occurs when electric current flow varies with azimuth. In porous media, this may correspond to anisotropy in the hydraulic conductivity resulting from sedimentary fabric, fractures, or dissolution. In this study, a 28‐electrode resistivity imaging system was used to investigate electrical anisotropy at 13 sites in the Biscayne Aquifer of SE Florida using the rotated square array method. The measured coefficient of electrical anisotropy generally ranged from 1.01 to 1.12 with values as high as 1.36 found at one site. The observed electrical anisotropy was used to estimate hydraulic anisotropy (ratio of maximum to minimum hydraulic conductivity) which ranged from 1.18 to 2.83. The largest values generally were located on the Atlantic Coastal Ridge while the lowest values were in low elevation areas on the margin of the Everglades to the west. The higher values of anisotropy found on the ridge may be due to increased dissolution rates of the oolitic facies of the Miami formation limestone compared with the bryozoan facies to the west. The predominate trend of minimum resistivity and maximum hydraulic conductivity was E‐W/SE‐NW beneath the ridge and E‐W/SW‐NE farther west. The anisotropy directions are similar to the predevelopment groundwater flow direction as indicated in published studies. This suggests that the observed anisotropy is related to the paleo‐groundwater flow in the Biscayne Aquifer.     

Use of Groundwater Levels with the PULSE Analytical Model

The PULSE analytical model, which calculates daily groundwater discharge on the basis of user‐specified recharge, was originally developed for calibration using streamflow data. This article describes a model application in which groundwater level data constitute the primary control on model input. As a test case, data were analyzed from a small basin in central Pennsylvania in which extensive groundwater level data are available. The timing and intensity of daily water‐level rises are used to ascertain temporal distribution of recharge, and the simulated groundwater discharge hydrograph has shape features that are similar to the streamflow hydrograph. This article does not include details about calibration, but some steps are illustrated and general procedures are described for calibration in specific hydrologic studies. The PULSE model can be used to assess results of fully automated base flow methods and can be used to define groundwater recharge and discharge at a relatively small time scale.     

Validation of temperature measurements from MIPAS-ENVISAT with balloon observations obtained by MIPAS-B

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a limb sounding Fourier transform interferometer in the mid-infrared band, on board the polar-orbiting ENVIronmental SATellite (ENVISAT) was launched in March 2002 by the European Space Agency (ESA). For the MIPAS data validation, three balloon flights with MIPAS-B, a balloon version of MIPAS, were carried out on the 24th and 25th of September 2002 from Aire sur l’Adour (France 44°N, 0°E), on the 20th and 21th of March, and on the 2nd and 3rd of July 2003 from Esrange, Kiruna (Sweden 68°N, 21°E). The MIPAS operational data version 4.61 for the temperature vertical profiles were compared with the correlative MIPAS-B measurements via the coincident comparison and the trajectory comparison approaches, respectively. The precision of the MIPAS temperature was estimated to be 1.04–2.48 K in the region 123–8 hPa (15–33 km) and beyond the expectation. The systematic difference shows that the absolute accuracy of the MIPAS temperature is within the total combined errors between 356 and 3 hPa (8–39 km). The agreements in the middle stratosphere are better than in the lower stratosphere and upper troposphere. The maximum difference of 1.9 K (0.9%) was found at 228 hPa (11 km). The biases of MIPAS measurements are ?0.39 K (?0.19%) and +0.25 K (+0.12%) (“+” positive bias, “?” negative bias) corresponding to the altitude regions 143–31 hPa (14–24 km) and 31–5 hPa (24–37 km), respectively.     

Parameter Estimation for Groundwater Models under Uncertain Irrigation Data

The success of modeling groundwater is strongly influenced by the accuracy of the model parameters that are used to characterize the subsurface system. However, the presence of uncertainty and possibly bias in groundwater model source/sink terms may lead to biased estimates of model parameters and model predictions when the standard regression‐based inverse modeling techniques are used. This study first quantifies the levels of bias in groundwater model parameters and predictions due to the presence of errors in irrigation data. Then, a new inverse modeling technique called input uncertainty weighted least‐squares (IUWLS) is presented for unbiased estimation of the parameters when pumping and other source/sink data are uncertain. The approach uses the concept of generalized least‐squares method with the weight of the objective function depending on the level of pumping uncertainty and iteratively adjusted during the parameter optimization process. We have conducted both analytical and numerical experiments, using irrigation pumping data from the Republican River Basin in Nebraska, to evaluate the performance of ordinary least‐squares (OLS) and IUWLS calibration methods under different levels of uncertainty of irrigation data and calibration conditions. The result from the OLS method shows the presence of statistically significant (p < 0.05) bias in estimated parameters and model predictions that persist despite calibrating the models to different calibration data and sample sizes. However, by directly accounting for the irrigation pumping uncertainties during the calibration procedures, the proposed IUWLS is able to minimize the bias effectively without adding significant computational burden to the calibration processes.     

On the material dependence of experimental shear fracture orientation

It is not uncommon to observe shear fractures in ductile rocks oriented at more than 45° with respect to the maximum compression direction. Since these orientations cannot be explained with the classic Mohr-Coulumb or Tresca yield criteria, Zheng et al.(Journal of Structural Geology, 35: 1394–1405, 2011) proposed the maximum effective moment(MEM) failure criterion. This rule suggests that shear fractures in ductile rocks form at ?55° with the maximum compression axis and that this orientation is material-independent and, therefore, universal. Zheng et al.(Science China: Earth Sciences, 57(11): 2819–2824, 2014) used data from our own experiments as supporting evidence of their failure criterion. In this contribution we discuss why shear fracture formation in ductile rocks indeed strongly depends on the mechanical properties of the deforming medium, and why experimental data should not be taken to prove the validity of the MEM criterion. The formation mechanisms and orientations of shear fractures in our experiments significantly vary depending on the material strength and degree and type of anisotropy(composite and intrinsic). We therefore demonstrate using experimental data that a universal failure angle in ductile and anisotropic rocks does not apply. Additionally, we highlight some inconsistencies of the MEM criterion.