Analysis of transgenic Indian mustard plants for phytoremediation of metal-contaminated mine tailings

Transgenic Indian mustard [Brassica juncea (L.) Czern.] plants overproducing the enzymes gamma-glutamylcysteine synthetase (ECS) or glutathione synthetase (GS) were shown previously to have increased levels of the metal-binding thiol peptides phytochelatins and glutathione, and enhanced Cd tolerance and accumulation. Furthermore, transgenic Indian mustard plants overexpressing adenosine triphosphate sulfurylase (APS) were shown to have higher levels of glutathione and total thiols. These results were obtained with a solution culture. To better examine the phytoremediation potential of these transgenics, a greenhouse experiment was performed in which the transgenics were grown on metal-contaminated soil collected from a USEPA Superfund site near Leadville, Colorado. A grass mixture used for revegetation of the site was included for comparison. The ECS and GS transgenics accumulated significantly (P < 0.05) more metal in their shoot than wild-type (WT) Indian mustard, while the APS plants did not. Of the six metals tested, the ECS and GS transgenics accumulated 1.5-fold more Cd, and 1.5- to 2-fold more Zn, compared with wild-type Indian mustard. Furthermore, the ECS transgenics accumulated 2.4- to 3-fold more Cr, Cu, and Pb, relative to WT. The grass mixture accumulated significantly less metal than Indian mustard: approximately 2-fold less Cd, Cu, Mn, and Zn, and 5.7-fold less Pb than WT Indian mustard. All transgenics removed significantly more metal from the soil compared with WT Indian mustard or an unplanted control. While WT did not remove more metal than the unplanted control for any of the metals tested, all three types of transgenics significantly reduced the soil metal concentration, and removed between 6% (Zn) and 25% (Cd) of the soil metal. This study is the first to demonstrate enhanced phytoextraction potential of transgenic plants using polluted environmental soil. The results confirm the importance of metal-binding peptides for plant metal accumulation and show that results from hydroponic systems have value as an indicator for phytoremediation potential.     

USE OF HEMISPHERIC IMAGERY FOR ESTIMATING STREAM SOLAR EXPOSURE1

ABSTRACT: Solar exposure profoundly affects stream processes and species composition. Despite this, prominent stream monitoring protocols focus on canopy closure (obstruction of the sky as a whole) rather than on measures of solar exposure or shading. We identify a candidate set of solar exposure metrics that can be derived from hemispheric images. These metrics enable a more mechanistic evaluation of solar exposure than can be achieved with canopy closure metrics. Data collected from 31 stream reaches in eastern Oregon enable us to quantify and compare metrics of solar exposure from hemispheric images and a metric of canopy closure with a concave densiometer. Repeatability of hemispheric metrics is generally as good as or better than the densiometer closure metric, and variation in the analysis of hemispheric images attributable to differences between analysts is negligibly small. Metrics from the hemispheric images and the densiometer are typically strongly correlated, at the scale of an individual observation and for 150 m stream reaches, but not always in a linear fashion. We quantify the character of the uncertainty in the relationship between the densiometer and the hemispheric metrics. Hemispheric imagery produces repeatable metrics representing an important ecological attribute; thus those researching the effects of solar exposure on stream ecosystems should consider the use of hemispheric imagery.     

NITROGEN AND PHOSPHORUS CONCENTRATIONS IN FOREST STREAMS OF THE UNITED STATES1

ABSTRACT: Seventy to eighty percent of the water flowing in rivers in the United States originates as precipitation in forests. This project developed a synoptic picture of the patterns in water chemistry for over 300 streams in small, forested watersheds across the United States. Nitrate (NO₃^?) concentrations averaged 0.31 mg N/L, with some streams averaging ten times this level. Nitrate concentrations tended to be higher in the northeastern United States in watersheds dominated by hardwood forests (especially hardwoods other than oaks) and in recently harvested watersheds. Concentrations of dissolved organic N (mean 0.32 mg N/L) were similar to those of NO₃～, whereas ammonium (NH₄⁺) concentrations were much lower (mean 0.05 mg N/L). Nitrate dominated the N loads of streams draining hardwood forests, whereas dissolved organic N dominated the streams in coniferous forests. Concentrations of inorganic phosphate were typically much lower (mean 12 mg P/L) than dissolved organic phosphate (mean 84 mg P/L). The frequencies of chemical concentrations in streams in small, forested watersheds showed more streams with higher NO₃^? concentrations than the streams used in national monitoring programs of larger, mostly forested watersheds. At a local scale, no trend in nitrate concentration with stream order or basin size was consistent across studies.     

SEDIMENT TRAPPING WITHIN FORESTRY STREAMSIDE MANAGEMENT ZONES: GEORGIA PIEDMONT,USA1

ABSTRACT: The effectiveness of streamside management zones (SMZs) was assessed for reducing sediment transport from concentrated overland flow draining two Georgia Piedmont clearcuts that had undergone mechanical and chemical site preparation and planting. Silt fences were used to trap sediment transport from zero‐order ephemeral swales at the edge of and within SMZs. Four control swales and nine treatment swales were studied. A double mass curve approach was used to graphically compare sediment accumulation rates at the edge of SMZs to accumulation rates within the SMZs at a distance consistent with current recommendations for SMZ width in Georgia. SMZ efficiencies for trapping sediment transported by concentrated flow ranged from 71 to 99 percent. No statistical model was found to explain how SMZ efficiencies varied with SMZ and contributing area characteristics. Measured sediment accumulations at the SMZ boundary were compared to Revised Universal Soil Loss Equation (RUSLE) predictions of up‐ slope erosion, and a delivery ratio of 0.25 was calculated. SMZs had a quantifiable and substantial ameliorating effect on sediment transport from concentrated overland flow on the clearcut study sites.     

Predicting River Floodplain and Lateral Channel Migration for Salmon Habitat Conservation1

Abstract: In this article, we describe a method for predicting floodplain locations and potential lateral channel migration across 82,900 km (491 km² by bankfull area) of streams in the Columbia River basin. Predictions are based on channel confinement, channel slope, bankfull width, and bankfull depth derived from digital elevation and precipitation data. Half of the 367 km² (47,900 km by length) of low‐gradient channels (≤ 4% channel slope) were classified as floodplain channels with a high likelihood of lateral channel migration (182 km², 50%). Classification agreement between modeled and field‐measured floodplain confinement was 85% (κ = 0.46, p < 0.001) with the largest source of error being the misclassification of unconfined channels as confined (55% omission error). Classification agreement between predicted channel migration and lateral migration determined from aerial photographs was 76% (κ = 0.53, p < 0.001) with the largest source of error being the misclassification of laterally migrating channels as non‐migrating (35% omission error). On average, more salmon populations were associated with laterally migrating channels and floodplains than with confined or nonmigrating channels. These data are useful for many river basin planning applications, including identification of land use impacts to floodplain habitats and locations with restoration potential for listed salmonids or other species of concern.     

Fate and transport of pathogens in lakes and reservoirs

Outbreaks of water-borne disease via public water supplies continue to be reported in developed countries even though there is increased awareness of, and treatment for, pathogen contamination. Pathogen episodes in lakes and reservoirs are often associated with rain events, and the riverine inflow is considered to be major source of pathogens. Consequently, the behaviour of these inflows is of particular importance in determining pathogen transport and distribution. Inflows are controlled by their density relative to that of the lake, such that warm inflows will flow over the surface of the lake as a buoyant surface flow and cold, dense inflows will sink beneath the lake water where they will flow along the bathymetry towards the deepest point. The fate of pathogens is determined by loss processes including settling and inactivation by temperature, UV and grazing. The general trend is for the insertion timescale to be shortest, followed by sedimentation losses and temperature inactivity. The fate of Cryptosporidium due to UV light inactivation can occur at opposite ends of the scale, depending on the location of the oocysts in the water column and the extinction coefficient for UV light. For this reason, the extinction coefficient for UV light appears to be a vitally important parameter for determining the risk of Cryptosporidium contamination. For risk assessment of pathogens in supply reservoirs, it is important to understand the role of hydrodynamics in determining the timescale of transport to the off-take relative to the timescale of inactivation. The characteristics of the riverine intrusion must also be considered when designing a sampling program for pathogens. A risk management framework is presented that accounts for pathogen fate and transport for reservoirs.     

Naval derusting wastewater containing high concentration of iron, treated in UV photo-Fenton-like oxidation

The UV photooxidation with Fe(III) and H2O2 was employed to treat a naval derusting wastewater, which contains the high COD (chemical oxygen demand) and various metal concentrations exceptionally with high concentrations of citric acid and iron. Because of its iron containment, the Fenton-like reaction automatically took place with the added amount of H2O2. The decomposition rate was found in a sequence of: UV/H2O2/Fe(III) > UV/H2O2 > Fe(II)/H2O2. Two H2O2 injection methods, single and multiple points, were evaluated. The multiple-point H2O2 injection was more e cient to decompose the citric acid. The decomposition of the synthetic citric acid and the real derusting citric acid wastewater was also compared. The 93% COD reduction of the derusting wastewater was achieved using the UV/H2O2/Fe(III) treatment.     

Harvestmen (Arachnida: Opiliones) from the Middle Jurassic of China

Harvestmen (Arachnida: Opiliones) are familiar animals in most terrestrial habitats but are rare as fossils, with only a handful of species known from each of the Palaeozoic, Mesozoic, and Cenozoic eras. Fossil harvestmen from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China, are described as Mesobunus martensi gen. et sp. nov. and Daohugopilio sheari gen. et sp. nov.; the two genera differ primarily in the relative length of their legs and details of the pedipalps. Jurassic arachnids are extremely rare and these fossils represent the first Jurassic, and only the fourth Mesozoic, record of Opiliones. These remarkably well-preserved and modern-looking fossils are assigned to the Eupnoi, whereby M. martensi demonstrably belongs in Sclerosomatidae. It thus represents the oldest record of a modern harvestman family and implies a high degree of evolutionary stasis among one of the most widespread and abundant groups of long-legged, round-bodied harvestmen.     

Constrained Laboratory vs. Unconstrained Steering-Induced Rollover Crash Tests

Objective: The goal of this study was to evaluate how well an in-laboratory rollover crash test methodology that constrains vehicle motion can reproduce the dynamics of unconstrained full-scale steering-induced rollover crash tests in sand.

Methods: Data from previously-published unconstrained steering-induced rollover crash tests using a full-size pickup and mid-sized sedan were analyzed to determine vehicle-to-ground impact conditions and kinematic response of the vehicles throughout the tests. Then, a pair of replicate vehicles were prepared to match the inertial properties of the steering-induced test vehicles and configured to record dynamic roof structure deformations and kinematic response.

Results: Both vehicles experienced greater increases in roll-axis angular velocities in the unconstrained tests than in the constrained tests; however, the increases that occurred during the trailing side roof interaction were nearly identical between tests for both vehicles. Both vehicles experienced linear accelerations in the constrained tests that were similar to those in the unconstrained tests, but the pickup, in particular, had accelerations that were matched in magnitude, timing, and duration very closely between the two test types. Deformations in the truck test were higher in the constrained than the unconstrained, and deformations in the sedan were greater in the unconstrained than the constrained as a result of constraints of the test fixture, and differences in impact velocity for the trailing side.

Conclusions: The results of the current study suggest that in-laboratory rollover tests can be used to simulate the injury-causing portions of unconstrained rollover crashes. To date, such a demonstration has not yet been published in the open literature. This study did, however, show that road surface can affect vehicle response in a way that may not be able to be mimicked in the laboratory. Lastly, this study showed that configuring the in-laboratory tests to match the leading-side touchdown conditions could result in differences in the trailing side impact conditions.