Approximate Field Conditions Research Articles

Analysis of Battery Testing Protocols in the Transition from the Lab to the Field: A Test Case Using Advanced Zn-MnO2 Batteries in Off-Grid Solar Microgrids

Understanding cycling performance of batteries under varying conditions is crucial for continued development of emerging chemistries. Currently much of this work is focused on cycling single cells in well-controlled lab experiments. There are few module cycling studies in the open literature. Studies of full-sized fielded systems are even rarer. As a result of this data gap, there is limited understanding of how single cell cycling can be used to predict performance of fielded systems prior to their deployment.Sandia National Laboratories (SNL) recently deployed an advanced Zn-MnO2 secondary battery energy storage system in an off-grid solar plus storage system. Using this deployment as a test case, we will detail how performance and degradation for batteries can vary between the lab and the field. We will also discuss ways that single cell and module lab cycling can be improved to better predict operation in fielded systems.In preparation for this deployment, SNL conducted single cell cycling experiments in the lab to simulate operation in the field and determine the expected life of the systems. The first test program utilized elements of the IEC 61427-1 standard for photovoltaic off-grid application to simulate the temperature and predicted state of charge (SOC) range the cells will be cycled during field operation. The simulated field cycling targeted SOC ranges of 10 to 40% and 80-100% over 150 cycles with temperature varied between -4 and 35oC to match the ambient conditions in the field during each season. The second type of cycling test was a temperature dependence study to determine how temperature impacted cell degradation. Cells were cycled at C/10 at their full SOC range and at a single temperature until they reached 40% capacity retention. Both cycling studies predicted that low temperature operation would increase the rate of degradation.The system was deployed in May of 2022, and since that time the SNL team has collected a significant amount of performance data to help analyze system level behaviors as compared to observations from cell level testing. These include battery interactions with the solar charge controller, limitations on power inverter settings, and variance between the average system level state of charge and the test protocol. Additionally, the team is analyzing conditions found in the field, with regards to ambient temperature, solar insolation and battery charging rates, and customer usage patterns for comparison with cell-level testing protocol.Observations of the deployed system’s performance indicate there is a need for more nuanced testing protocols for lab testing that can better approximate field conditions. These may include dynamic temperature ranges that vary throughout a charge/discharge cycle, and solar charging assumptions that account for reduced insolation due to cloud cover. This can help further inform the development of charge control algorithms, system hardware and software that can help improve the overall performance of solar microgrid energy storage systems.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2023-02502A

Coriolis-induced instabilities in centrifuge modeling of granular flow

Granular flows are typically studied in laboratory flumes based on common similarity scaling, which create stress fields that only roughly approximate field conditions. The geotechnical centrifuge produces stress conditions that are closer to those observed in the field, but steady conditions can be hardly achieved. Moreover, secondary effects induced by the apparent Coriolis acceleration, which can either dilate or compress the flow, often obscure scaling. This work aims at studying a set of numerical experiments where the effects of the Coriolis acceleration are measured and analyzed. Three flow states are observed: dense, dilute, and unstable. It is found that flows generated under the influence of dilative Coriolis accelerations are likely to become unstable. Nevertheless, a steady dense flow can still be obtained if a large centrifuge is used. A parametric group is proposed to predict the insurgence of instabilities; this parameter can guide experimental designs and could help to avoid damage to the experimental apparatus and model instrumentation.Graphic abstract

Seismic responses and damage mechanisms of the structure in the portal section of a hydraulic tunnel in rock

Tunnel portals, being shallow underground structures, are well known to be more vulnerable to damage during earthquakes because they are generally located in areas of poor geological conditions that likely lead to amplified ground motions; this is especially true for hydraulic tunnel portals, which are additionally subjected to considerable hydrodynamic pressure. In this work, a full three-dimensional (3D) seismic analysis of the portal structure of a hydraulic tunnel is presented. Additionally, the hydrodynamic pressure and the rock-structure interaction (RSI) are both considered in this analysis to approximate actual field conditions, and their impacts on the seismic response and the damage characteristics of the tunnel portal are studied in detail. The numerical results indicate that the hydrodynamic pressure and the RSI contribute to a greater seismic response of the tunnel structure, with the peak displacements likely increasing by 48% when the hydrodynamic pressure is considered. The tunnel sections as far as 40 m from the entrance may suffer severe damage, and the constraint effects of the surrounding rock can efficiently reduce the damage of the tunnel structure. Two typical damage patterns are deduced from the simulation results and can be reasonably interpreted by the corresponding damage mechanisms.

Field and Greenhouse Evaluations of Cucurbit Rootstocks to Improve Verticillium Resistance for Grafted Watermelon

Grafting watermelon (Citrullus lanatus Thunb.) onto resistant rootstocks is used in many areas of the world to overcome soilborne disease losses including verticillium wilt caused by Verticillium dahliae Kleb. Currently, this disease poses a serious risk to watermelon growers in Washington State. To identify resistant rootstocks, the verticillium wilt reactions (chlorosis, necrosis, and wilting) of 14 nongrafted PI accessions including Benincasa hispida Thunb., Cucurbita moschata Duchesne ex Poir., and Lagenaria siceraria Molina Standl. from the U.S. Department of Agriculture National Plant Germplasm System (USDA NPGS); 11 nongrafted commercially available rootstocks; and, nongrafted ‘Sugar Baby’ watermelon (verticillium wilt–susceptible control) were visually assessed in a field naturally infested with V. dahliae at a rate of 17 colony-forming units (cfu) per gram of soil. Typical symptoms of verticillium wilt were observed on all entries. ‘Sugar Baby’ had the highest relative area under disease progress curve (RAUDPC) value (26.80), which was not significantly different from ‘64-19 RZ’, ‘Marvel’, PI 368638, PI 634982, and PI 642045 (average = 10.16). PI 419060 (1.46) had the lowest RAUDPC value, which was not significantly different from ‘Miniature Bottle Gourd’, PI 326320, PI 419016, PI 536494, PI 636137, ‘Strong Tosa’, ‘Strongtosa’, and ‘TZ 148’ (average = 3.36). The mean RAUDPC value of PI accessions (5.49) did not differ significantly from the mean value of the commercial rootstocks (5.68). Microsclerotia typical of Verticillium spp. were observed in the stems of all but one entry (PI 181913). In a greenhouse study, a subset of 12 entries were inoculated with V. dahliae, and by 22 days after inoculation (DAI), ‘Sugar Baby’ had a significantly higher disease rating than all entries except PI 419060, PI 438548, and ‘Titan’. A strong positive correlation was observed between the field and greenhouse studies. Results indicate that commercial rootstocks as well as PI accessions could be used to successfully manage verticillium wilt in Washington; however, grafting compatibility with watermelon must first be ascertained for the promising PI accessions. Although greenhouse-based verticillium wilt assays can be used to help predict rootstock performance in the field, accurate assessment may require manipulating environmental conditions (e.g., temperature and humidity) to approximate field conditions.

Influence of Diet and Density on Laboratory Cannibalism Behaviors in Gypsy Moth Larvae (Lymantria dispar L.)

The gypsy moth (Lymantria dispar) is an insect folivore that feeds on a broad range of hosts, and undergoes intermittent outbreaks that cause extensive tree mortality. Like many other herbivorous insects, gypsy moth larvae consume a substrate that is low in nitrogen. Gypsy moth larvae have been known to cannibalize under crowded conditions in the laboratory. In this study, we assessed the influence of nitrogen and density on cannibalism behavior in gypsy moth larvae. Cannibalism rates increased with decreased nitrogen and increased density. There was no interaction between these two parameters. Developmental experiments confirmed that low dietary nitrogen is detrimental, in agreement with previous studies. In a second experiment, we assessed the influence of previous cannibalism experiences on subsequent cannibalism behavior. Gypsy moth larvae that had previously cannibalized other larvae subsequently exhibited higher cannibalism rates than those larvae that had not cannibalized. In conclusion, low nitrogen, high larval density, and previous cannibalism experience are important factors contributing to gypsy moth larval cannibalism. Future studies are needed to estimate benefits to larvae, and to more closely approximate field conditions.

Predictive uncertainty analysis of a saltwater intrusion model using null‐space Monte Carlo

Because of the extensive computational burden and perhaps a lack of awareness of existing methods, rigorous uncertainty analyses are rarely conducted for variable‐density flow and transport models. For this reason, a recently developed null‐space Monte Carlo (NSMC) method for quantifying prediction uncertainty was tested for a synthetic saltwater intrusion model patterned after the Henry problem. Saltwater intrusion caused by a reduction in fresh groundwater discharge was simulated for 1000 randomly generated hydraulic conductivity distributions, representing a mildly heterogeneous aquifer. From these 1000 simulations, the hydraulic conductivity distribution giving rise to the most extreme case of saltwater intrusion was selected and was assumed to represent the “true” system. Head and salinity values from this true model were then extracted and used as observations for subsequent model calibration. Random noise was added to the observations to approximate realistic field conditions. The NSMC method was used to calculate 1000 calibration‐constrained parameter fields. If the dimensionality of the solution space was set appropriately, the estimated uncertainty range from the NSMC analysis encompassed the truth. Several variants of the method were implemented to investigate their effect on the efficiency of the NSMC method. Reducing the dimensionality of the null‐space for the processing of the random parameter sets did not result in any significant gains in efficiency and compromised the ability of the NSMC method to encompass the true prediction value. The addition of intrapilot point heterogeneity to the NSMC process was also tested. According to a variogram comparison, this provided the same scale of heterogeneity that was used to generate the truth. However, incorporation of intrapilot point variability did not make a noticeable difference to the uncertainty of the prediction. With this higher level of heterogeneity, however, the computational burden of generating calibration‐constrained parameter fields approximately doubled. Predictive uncertainty variance computed through the NSMC method was compared with that computed through linear analysis. The results were in good agreement, with the NSMC method estimate showing a slightly smaller range of prediction uncertainty than was calculated by the linear method.

Co-evolving delta faces under the condition of a moving sediment source

A fan delta developed under the constraints of a moving point of flow-sediment supply is described. The sediment mixtures used in the experiments were chosen to approximate field conditions, with the coarser fractions depositing to form the topset (subaerial delta surface) and foreset, and the finer fractions forming a turbidity current that plunges near the shoreline, overrides the foreset, and continues into deeper water to emplace a bottomset. The migration rate of the feed point was adjusted so that the base of the lateral foreset along one side just touched the flume wall, so leaving open water on that side. The experiments provide insight into the sedimentation processes associated with these three co-evolving structures of the delta, i.e. its topset, foreset, and bottomset. The results indicate that the lateral delta extent can be controlled via the downstream migration of its sediment source.

Effects of host‐plant species on diapause induction of the Kanzawa spider mite, Tetranychus kanzawai

AbstractIn many herbivorous arthropods, incidence of diapause, which is considered to reflect the timing of diapause, changes depending on the host plants they utilize. Several theoretical studies suggest that the optimal timing of diapause induction depends on life‐history traits; if the development time of the arthropod is short, fecundity is high, or survival rate remains high throughout the season, the optimal timing of diapause induction would be shifted toward the end of the season. For herbivorous arthropods, these life history traits may change among their host plants. Here we examined whether a population of the Kanzawa spider mite, Tetranychus kanzawai Kishida (Acari: Tetranychidae), shows the predicted pattern of diapause induction on two host plants, the kidney bean [Phaseolus vulgaris (Leguminosae)] and Japanese Orixa [Orixa japonica (Rutaceae)], on which the mites show different performances. Rearing conditions were controlled in two ways. In the first experiment, day length and temperature were kept constant throughout the mite lifetime at either of three conditions from mid October to early November. In the second experiment, the conditions were changed from 20 °C and L11.5:D12.5 at immature stages to 18 °C and L11:D13 at adult stage in order to better approximate field conditions. In the first experiment, diapause incidence on P. vulgaris was lower than on O. japonica. This tendency became stronger in the second experiment, suggesting a difference in the timing of diapause induction among host plants. On the other hand, P. vulgaris was proven to allow high performance, i.e., greater lifetime fecundity and shorter development times, although it had no effect on the survival rate. The relationship between diapause incidence and performance is consistent with the prediction of theoretical studies that a short development time or high fecundity delays the timing of diapause induction.

Experimental Zn(II) retention in a sandy loam soil by very small columns

The use of column experiments, usually performed to better approximate field conditions, may provide information that is not available from batch experiments. In such experiments heavy metals are often adsorbed until saturation followed by desorption experiments. When the affinity of the metal to soil is high, the retention factor ( R) could be greater than thousands and the duration of experiments can become impractically long. In order to use reasonable laboratory time, the flow rate should be increased or the column size decreased. The increase in flow rate produces undesirable kinetic and dispersion effects, so we used very small soil columns (pore volume = 0.31–0.70 ml) and relatively high flow rates (0.03–0.12 ml min −1) in studies of Zn(II) adsorption and retention in soils. Conservative tracer flow column experiments under saturation conditions were carried out to determine flow parameters for different flow rates. Column pore volume ( V p), Peclet numbers ( Pe) and longitudinal dispersion coefficients ( D L) were determined from breakthrough curves. The effect of type of electrolyte and ionic strength on the Zn(II) retention onto soil was determined. The influence of flow rate and bed height on the retention coefficient and on the mass transfer zone was also studied. The effect of different influent Zn(II) concentrations on the R values obtained was analyzed. Freundlich parameters from column experiments were compared with batch ones. The leaching efficiency of different electrolytes, salts of weak organic acids and EDTA was also studied.

Root architectural tradeoffs for water and phosphorus acquisition.

Root architectural traits that increase topsoil foraging are advantageous for phosphorus acquisition but may incur tradeoffs for the acquisition of deep soil resources such as water. To examine this relationship, common bean genotypes contrasting for rooting depth were grown in the field and in the greenhouse with phosphorus stress, water stress and combined phosphorus and water stress. In the greenhouse, water and phosphorus availability were vertically stratified to approximate field conditions, with higher phosphorus in the upper layer and more moisture in the bottom layer. Under phosphorus stress, shallow-rooted genotypes grew best, whereas under drought stress, deep-rooted genotypes grew best. In the combined stress treatment, the best genotype in the greenhouse had a dimorphic root system that permitted vigorous rooting throughout the soil profile. In the field, shallow-rooted genotypes surpassed deep-rooted genotypes under combined stress. This may reflect the importance of early vegetative growth in terminal drought environments. Our results support the hypothesis that root architectural tradeoffs exist for multiple resource acquisition, particularly when resources are differentially localised in the soil profile. Architectural plasticity and root dimorphism achieved through complementary growth of distinct root classes may be important means to optimise acquisition of multiple soil resources.

Habitat quality and prey size as determinants of survival in post-larval and early juvenile instars of the blue crab Callinectes sapidus

Habitat structure and prey size are important determinants in the outcome of predator-prey interactions. We investigated the role of simulated habitat type and density (simulated Zostera marina [hereafter referred to as 'Zostera']: 500 and 1500 shoots m -2 , and simulated Spartina alterniflora [hereafter referred to as 'Spartina']: 97 and 291 shoots m -2 ) in mediating predator-prey interactions. Proportional survival during predation by the piscene predator Fundulus heteroclitus on 2 successive life-history stages (post-larvae and first juvenile instars) of the blue crab Callinectes sapidus (Rathbun), was quantified under laboratory conditions that closely approximated field conditions. We also examined the effects of juvenile crab size (equal biomass and equal numbers of 2 or 3 prey-size categories, respectively) on survival during adult F. heteroclitus predation in the absence of vegetation. Crab size categories included small (first juvenile instars; 2.1 mm carapace width [cw]), medium (fourth and fifth crab stage juveniles; 6.0 to 9.1 mm cw), and large (sixth and seventh stage juveniles; 9.2 to 12.6 mm cw) in the equal numbers experiments and small and medium crabs for the equal biomass experiment. Mean proportional survival was higher for both life-history stages in simulated Zostera, with first-instars exhibiting higher proportional survival than post-larvae at the experimental densities tested (post-larvae: no grass = 0.23, low-density grass = 0.44, high-density grass = 0.57; first-instars: no grass = 0.47, low-density grass = 0.87, high-density grass = 0.87). Mean proportional survival did not differ significantly among life-history stages in the simulated Spartina treatments, although proportional survival between treatments was higher for first-instars than post-larvae (post-larvae: no Spartina = 0.17, low-density Spartina = 0.18, high-density Spartina = 0.19; first-instars: no Spartina = 0.46, low-density Spartina = 0.43, high-density Spartina = 0.48). Finally, size-refuge experiments with equal numbers or biomass of prey demonstrated significant differences between each size or/and biomass category tested. Crabs exhibited increasing proportional survival with increasing crab size (small = 0.34, medium = 0.66, large = 0.97) or weight (small = 0.18, medium = 0.67) in the presence of F. heteroclitus, suggesting that C. sapidus attains a refuge in size from predation by adult F. heteroclitus at approximately 9.2 to 12.6 mm. Our findings suggest that the influence of habitat structure on crab survival (possibly as a function of surface area) varies with simulated habitat type, crab density and crab stage (post-larvae versus first-instar), providing additional evidence of the importance of seagrasses in the early life-history stages of blue crabs.

First Report of Botryotinia fuckeliana on Kerguelen Cabbage on the Sub-Antarctic Marion Island.

Pringlea antiscorbutica R. Br. (the Kerguelen cabbage) is a monotypic species endemic to five sub-Antarctic islands. It does not occur elsewhere and is the only brassica found in the sub-Antarctic region as a whole (1). On Marion Island (46° 54'S, 37° 45'E) the distribution and abundance of the cabbage has declined alarmingly over the past 20 years and the plants increasingly are showing symptoms of microbial pathogen attack. Leaves display brown, water-soaked lesions and sometimes whole plants collapse into a black, slimy residue. Small sections of lesions were sampled, surface sterilized, and placed on water agar and potato dextrose agar (PDA) to which streptomycin (0.1 g/liter) was added. Nonsterilized sections were placed in petri dishes on moist, sterilized, filter paper. Plates were incubated at 15°C in the dark. Botryotinia fuckeliana (de Bary) Whetzel (conidial state; Botrytis cinerea Pers.:Fr) was consistently isolated. Gray to white mycelium grew rapidly on PDA and after 10 days abundant black sclerotia (2 to 16 mm long) were observed on the medium. To confirm pathogenicity, four detached leaves of P. antiscorbutica were each inoculated with a single, 5-mm-diameter PDA plug of B. fuckeliana. Four leaves with noncolonized PDA plugs were used as controls. The leaves were placed with their petioles in sterile water in a transparent incubation chamber. Chamber temperature (minimum 3.9°C, maximum 7.7°C and mean 6.4°C) and light (100 µmol s-1 m-2 photosynthetic photon flux density) approximated field conditions quite closely but relative humidity (annual mean for the island, 81%) was on average 10% higher in the chamber. First symptoms were observed after about 48 h. After 5, 7, and 8 days, brown, water-soaked lesions averaged 14 × 7, 28 × 11, and 36 × 18 mm, respectively. Control leaves showed no symptoms. Reisolations from lesions produced B. fuckeliana. Identity of the pathogen was confirmed by the South African National Collection of Fungi Biosystematics Division, Pretoria. The sub-Antarctic climate is probably conducive to the rapid spread of B. fuckeliana and to its ability to infect P. antiscorbutica. Other factors, such as the recent introduction of the diamondback cabbage moth (Plutella xylostella) to the island and grazing damage by an introduced slug species (Deroceros caruanae) probably exacerbate the threat offered by the fungus to this plant species, one of the last and perhaps the only, remaining relic of an extensive circum-Antarctic flora. Reference: (1) A. J. Dorne and R. Bligny. Polar Biol. 13:55, 1993.

Simulated sea level change alters anatomy, physiology, growth, and reproduction of red mangrove (Rhizophora mangle L.).

Tropical coastal forests - mangroves - will be one of the first ecosystems to be affected by altered sea levels accompanying global climate change. Responses of mangrove forests to changing sea levels depend on reactions of individual plants, yet such responses have not been addressed experimentally. We report data from a long-term greenhouse study that assessed physiological and individual growth responses of the dominant neotropical mangrove, Rhizophora mangle, to levels of inundation expected to occur in the Caribbean within 50-100 years. In this study, we grew potted plants in tanks with simulated semidiurnal (twice daily) high tides that approximated current conditions (MW plants), a 16-cm increase in sea level (LW plants), and a 16-cm decrease in sea level (HW plants). The experiment lasted 2½ years, beginning with mangrove seedlings and terminating after plants began to reproduce. Environmental (air temperature, relative humidity, photosynthetically active radiation) and edaphic conditions (pH, redox, soil sulfide) approximated field conditions in Belize, the source locale for the seedlings. HW plants were shorter and narrower, and produced fewer branches and leaves, responses correlated with the development of acid-sulfide soils in their pots. LW plants initially grew more rapidly than MW plants. However, the growth of LW plants slowed dramatically once they reached the sapling stage, and by the end of the experiment, MW plants were 10-20% larger in all measured growth parameters. Plants did not exhibit differences in allometric growth as a function of inundation. Anatomical characteristics of leaves did not differ among treatments. Both foliar C:N and root porosity decreased from LW through MW to HW. Relative to LW and HW plants, MW plants had 1-7% fewer stomata/mm2, 6-21% greater maximum photosynthetic rates, 3-23% greater absolute relative growth rates (RGRs), and a 30% higher RGR for a given increase in net assimilation rate. Reduced growth of R. mangle under realistic conditions approximating future inundation depths likely will temper projected increased growth of this species under concomitant increases in the atmospheric concentration of CO2.

Inaccuracy of three-finger pinch method of determining salt content in homemade sugar salt solutions.

Oral rehydration therapy (ORT) has dramatically reduced the morbidity and mortality associated with acute infectious diarrhea. Commercial oral rehydration salt (ORS) solutions with sodium concentrations of 30-90 mmol/L are ideal for both the prevention and treatment of dehydration. However, logistic issues impede their universal availability and homemade sugar salt (HSS) solutions are widely used in some areas of the world. The least accurate methods of preparing HSS solutions utilize a three-finger pinch of salt. The present study demonstrates the inconsistency and inaccuracy of this method among 15 health workers who participated in an ORT training seminar conducted in a situation that approximated field conditions. Similar studies with different subjects, instructions, and milieu describe results similar to those we obtained. In all studies, including the present one, a substantial number of the solutions prepared by this method had dangerously high or low sodium concentrations. Health providers should consider the use of selected home-available fluids rather than HSS solutions for the prevention of dehydration in children with diarrhea. However, ORS solutions should be used to correct established dehydration.

Measurement of Trichloroethylene Diffusion as a Function of Moisture Content in Sections of Gravity‐Drained Soil Columns

AbstractExperiments were conducted on discrete sections of gravity‐drained sand columns to determine the relationship between the effective diffusion coefficient of trichloroethylene and moisture content in variably saturated porous media. The columns were gravity drained to closely approximate field conditions and the moisture content within each column ranged from field capacity near the top to saturation near the bottom. Measured effective diffusion coefficients were compared with theoretical coefficients calculated using Millington's expression for tortuosity, modified to incorporate diffusion in both the gas and aqueous phases. Agreement between the measured and theoretical effective diffusion coefficients was good for all moisture contents investigated.

Pepper (Capsicum annuum) Cultivar Response to Metolachlor in Three New Mexico Soils

Field experiments in 1988, 1989, and 1990 evaluated the response of four pepper cultivars to PPI applications of metolachlor at Las Cruces and Artesia, New Mexico. Metolachlor at ≥ 2.2 kg ai ha–1in 1988 and 4.5 kg ha–1in 1990 reduced overall green pepper yields only in a Harkey very fine sandy loam soil at Artesia. Metolachlor at ≥ 2.2 kg ha–1reduced the yield of the jalapeno cultivar ‘TAM’ and at 4.5 kg ha–1reduced the yield of New Mexico cultivar ‘NM 6-4’ and a proprietary New Mexico cultivar in 1988. Metolachlor did not reduce the yield of any cultivar in 1989 or 1990. Metolachlor bioactivity on NM 6-4 pepper was similar in the three soils regardless of irrigation water source. Emergence of peppers was ranked Belen clay loam = Rakor loam > Harkey very fine sandy loam when the greenhouse temperature approximated field conditions. Under conditions where germination and emergence of peppers was reduced by an interaction between soil factors and temperature, further stand reduction due to metolachlor treatment caused yield reductions.

The Sensitivity of Four Monitoring Well Sampling Systems to Low Concentrations of Three Volatile Organics

AbstractFour state‐of‐the‐art ground water sampling systems were analyzed to determine their reliability in providing representative samples of the volatile chlorinated hydrocarbons trichloroethylene (TCE), perchloroethylene (PCE), and 1,1,1‐trichloroethane (TCA) from a simulated monitoring well. The sampling systems studied represent four commonly used devices, including a stainless steel and Teflon® piston pump, a Teflon bailer, a Teflon bladder pump, and a PVC air‐lift pump.Controlled laboratory sampling experiments were conducted in a tank and well test chamber designed to approximate field conditions. A well purging and sampling procedure was used in the test apparatus to determine the accuracy and precision of each device for detecting low concentrations of the compounds in ground water. The compounds selected are some of the most ubiquitous hazardous contaminants found in shallow aquifers near hazardous waste sites throughout the United States.No significant statistical difference was found among the four sampling systems in detecting the compounds.

Meta-analysis of mock crime studies of the control question polygraph technique.

A review of results obtained from standard guilty and innocent treatment conditions in 14 mock crime studies of the control question polygraph technique revealed accuracies ranging from chance to 100% correct. The present study examined several factors that may have contributed to the observed variability in detection rates across studies. Those included sampling error, differences in the populations from which subjects were drawn (Subjects), differences in the nature of incentives provided to subjects for passing the polygraph test (Incentives), and differences in the methods for diagnosing truth or deception (Decision Policy). A meta-analysis revealed that approximately 24% of the variance in detection rates could be attributed to sampling error, and detection rates were correlated with types of Subjects (r=.61). Incentives (r=.73), and Decision Policies (r=.67). The highest diagnostic accuracies were obtained from nonstudent subject samples, when both guilty and innocent subjects were offered monetary incentives to convince the examiner of their innocence, and when conventional field methods were used for interpreting the physiological recordings and diagnosing truth and deception. Together, differences in Subjects, Incentives, and Decision Policies may account for as much as 65% of the observed variance in detection rates. The present findings highlight the importance of conducting mock crime experiments that closely approximate field conditions.

TOXICITY OF DISPERSED AND UNDISPERSED PRUDHOE BAY CRUDE OIL FRACTIONS TO SHRIMP AND FISH

ABSTRACT Many previous studies of oil toxicity used high oil concentrations and water soluble fractions (WSF). The aim of this study was to approximate field conditions, in which weathering and chemical dispersions reduce the volatile fractions of spilled crude oil. The objective was to determine the extent of toxicity reduction produced by decreased concentrations of monoaromatics and diaromatics. The study measured the relative toxicity of fresh Prudhoe Bay crude (PBC) oil and two distillation fractions (Stage I and Stage II) and their chemical dispersions to the shrimp Pandalus danae and the fish Ammodytes hexapterus (sand lance). The hydrocarbon composition of the three oils, the WSF of the oils, and the chemical dispersions were measured. Distillation of fresh PBC oil produced a Stage I oil containing very low amounts of monoaromatics (benzene and alkylbenzenes) but with the diaromatics relatively unchanged. Further distillation produced a Stage II oil which contained only higher molecular weight aromatics of three rings (phenanthrenes) and greater. Saturate hydrocarbons with corresponding boiling points also were removed. Bioassays on shrimp with dispersed oils showed that the removal of monoaromatics (Stage I) reduced toxicity about sevenfold. The WSF of Stage I oil and both WSF and dispersions of Stage II oil were not toxic to shrimp. Toxicity from fresh PBC oil WSF and dispersions was likely the result of the combination of monoaromatic and diaromatic compounds. Sand lance (Ammodytes hexapterus) mortality did not correlate with the aromatic content of the oils, but appeared to be affected by dispersed oil droplets of all three oils to about the same degree. The fish were more resistant to dispersed oil than the shrimp (higher toxicity index). However, when latent mortality is considered, the data show that the fish may be more sensitive than shrimp to dispersed oil.

A Field Comparison of Transient Drain Spacing Equations in a Southern Alberta Lacustrine Soil

ABSTRACT PREDICTIONS of water-table positions and drain spacings computed using theoretical transient drain spacing equations were compared with the measured performance of subsurface drains installed in a relatively shallow lacustrine soil in southern Alberta, Canada. Results from empirical drain spacing equations, which were developed by measuring the performance of subsurface drains installed at depths of 0.76, 1.22 and 1.68 m, were compared with computations using theoretical drainage equations. The Bouwer and van Schilfgaarde equation, using a C-factor of 1.0, most closely predicted the measured performance of the existing drains under all conditions. The accuracy of the equations, and the range in average absolute deviation in drain spacing predictions (in brackets), was Bouwer and van Schilfgaarde, C=1.0 (4 to 9%) > van Schilfgaarde (6 to 13%) > Modified Glover (10 to 16%) > Bouwer and van Schilfgaarde, C=0.8 (11 to 19%) > Glover for drains placed on the barrier (23 to 40%) > Hammad, thick layers (40 to 59%) > Hammad, thin layers (35 to 110%). Individual equations generally predicted according to theory, provided the theoretical assumptions of the equations approximated field conditions.