Migration of VOC Plume in the Subsurface Domain at the Y‐12 National Security Site

During the production of thermonuclear fusion weapons at the Y‐12 National Security Complex (Y‐12 NSC) in Oak Ridge, Tennessee, between 1950 and 1963, the regional environment was extensively contaminated by volatile organic compounds (VOCs). Old Salvage Yard (OSY) on the western side of the site has been characterized as the major source of VOCs. In order to analyze the long‐term fate and transport of chlorinated VOC sources, an integrated surface and subsurface flow and transport model was developed for the Y‐12 NSC using the hydrodynamic and transport numerical package MIKE‐SHE. The model was developed considering the recent hydrogeological investigations on preferential flow and transport pathways at the site. The model was calibrated using the recorded groundwater flow and water‐quality data. The modeling simulated migration of the VOC plume for the next 100 years. Considering a range of hydrogeological and transport parameters, uncertainty of the results is discussed. The modeling predicted that tetrachloroethene, trichloroethene, and 1,2‐dichloroethene may exceed human health–related risk levels for the next 10 to 20 years. However, the contamination is unlikely to migrate to surface water under the current hydrogeological conditions and will decay below acceptable risk levels within approximately 20 years. © 2013 Wiley Periodicals, Inc.     

Strategies to evaluate biodegradability: application to chlorinated herbicides

The biodegradability of nitrochlorinated (diuron and atrazine) and chlorophenoxy herbicides (2,4-D and MCPA) has been studied through several bioassays using different testing times and biomass/substrate ratios. A fast biodegradability test using unacclimated activated sludge yielded no biodegradation of the herbicides in 24 h. The inherent biodegradability test gave degradation percentages of around 20–30 % for the nitrochlorinated herbicides and almost complete removal of the chlorophenoxy compounds. Long-term biodegradability assays were performed using sequencing batch reactor (SBR) and sequencing batch membrane bioreactor (SB-MBR). Fixed concentrations of each herbicide below the corresponding EC₅₀ value for activated sludge were used (30 mg L^?1 for diuron and atrazine and 50 mg L^?1 for 2,4-D and MCPA). No signs of herbicide degradation appeared before 35 days in the case of diuron and atrazine and 21 days for 2,4-D, whereas MCPA was partially degraded since the early stages. Around 25–36 % degradation of the nitrochlorinated herbicides and 53–77 % of the chlorophenoxy ones was achieved after 180 and 135 days, respectively, in SBR, whereas complete disappearance of 2,4-D was reached after 80 days in SB-MBR.     

Some toxicological aspects op methamidophos exposure in mice 1

Abstract

Cholinesterase activity in the brain, RBC and plasma of Swiss mice was determined following different routes of administration of methamidophos. Continuous feeding with the insecticide caused a progressive inhibition of both plasma‐ and erythrocyte enzymes. The effect of methamidophos was more pronounced when applied in diet than when administered dermally or intraperitoneally. Following a single injection (i.p.) of methamidophos, the brain enzyme showed maximum inhibition 24 hr following treatment. At the appearance of tremors, the plasma and RBC‐enzymes showed considerable inhibition, the former being more inhibited. The plasma enzyme appears to be the most sensitive enzyme and may be taken as a suitable index for exposure to methamidophos.     

Clinical effects and cholinesterase activity changes in workers exposed to phorate (Thimet)

Abstract

Phorate (Thimet), an aliphatic derivative of phospnorus is a hignly toxic insecticide. In order to implement the safety measures, the clinical manifestations and cholinesterase (ChE) activity were evaluated before and after 2 weeks of exposure to this insecticide in 40 male tormulators.

The 2 week's exposure reveal signs and symptoms of toxicity in 60% of the formulators. Gastrointestinal symptoms and lowering of heart rate (bradycardia) were more prominent as compared to the neurological symptoms. A significant depression in plasma ChE activity was observed at the end of 1st week (55%) and 2nd week (71%) as compared to the respective pre‐exposure values. A recovery up to 79% of the pre‐exposure activity of this enzyme was noticed 10 days after cessation of the above exposure.     

Contributions to ecological chemistry CXII balance of conversion of buturon‐14C in wheat under outdoor conditions 1

Abstract

The urea herbicide buturon (N‐[p‐chlorophenyl] ‐N’ ‐methyl‐N’ ‐isobutinyl‐urea), ¹⁴C‐labeled, was sprayed on winter wheat as an aqueous formulation (2.98 kg/ha) under outdoor conditions. Upon harvest (three months after application), a total of 49. 2% of the applied radiocarbon was recovered: 2.0% in the plants, 46.9% in the soil, and 0.3% in the leaching water (depth > 50 cm); less than 0.1% was in the grains (0.464 ppm). Only about half of the radioactivity present in plants could be recovered under mild extraction conditions; about half of this was unchanged buturon. In straw and husk extracts, the following metabolites were identified by gaschromatography/mass spectrometry: N‐(p‐chlorophenyl)‐N‐methyl‐O‐methyl‐carbamate (metabolite I), N‐phenyl‐N’ ‐formyl‐urea (metabolite II), two unstable metabolites giving (p‐chlorophenyl)‐isocyanate upon purification (metabolites III and IV), N‐(p‐chlorophenyl)‐N’ ‐methyl‐N’ ‐isobutenylol‐urea (metabolite V), p‐chloroformanilide (metabolite VI) and biologically bound p‐chloroaniline (metabolite VII). In the root and basal stem extract, the following metabolites were identified by gas chromatography/mass spectrometry: N‐(p‐chlorophenyl)‐O‐methyl‐carbamate (metabolite VIII) and N‐(p‐chlorophenyl)‐N’ ‐methyl‐urea (metabolite IX).     

Effect of some xenobiotics on kynurenine hydrolase and kynurenine aminotransferase of mouse liver

Abstract

The effects of some xenobiotics on the activity of the B₆‐dependent kynurenine hydrolase (KH) and kynurenine aminotransferase (KATE) in mouse liver, were investigated. Polychlorinated biphenyl (Aroclor 1254) (400mg/kg/day ×4) markedly decreased the activity of both enzymes. Benzo(a)pyrene (BP) and 3‐methylcholanthrene (3‐MC) (40mg/Kg/day ×1) as well as phénobarbital (PB) (75mg/kg/day ×3) did not alter the activity of KH, while that of KATE was mildy reduced. The response of the two enzymes to treatment with chlorpromazine (CPZ) (5mg/Kg/day ×5) were opposite with marked elevation of KH and inhibition of KATE activities. Treatment with B‐naphthoflavone (B‐NF) (80mg/Kg/day ×2), Pyrazole (200mg/Kg/day ×1) or indole (400mg/kg/day ×1) produce no change in the activity of either enzyme. It, seems therefore, that Aroclor(1254) and chlorpromazine may cause disordered kynurenine metabolism through alterations in the activities of its metabolizing enzymes. This, in turn, might affect nicotinamide adenine dinucleotide biosynthesis and/or the accumulation of some tryptophan metabolites suspected of being carcinogenic or co‐carcinogenic.     

Aerosol species concentrations and source apportionment of ammonia at Rocky Mountain National Park

Changes in ecosystem function at Rocky Mountain National Park (RMNP) are occurring because of emissions of nitrogen and sulfate species along the Front Range of the Colorado Rocky Mountains, as well as sources farther east and west. The nitrogen compounds include both oxidized and reduced nitrogen. A year-long monitoring program of various oxidized and reduced nitrogen species was initiated to better understand their origins as well as the complex chemistry occurring during transport from source to receptor. Specifically, the goals of the study were to characterize the atmospheric concentrations of nitrogen species in gaseous, particulate, and aqueous phases (precipitation and clouds) along the east and west sides of the Continental Divide; identify the relative contributions to atmospheric nitrogen species in RMNP from within and outside of the state of Colorado; identify the relative contributions to atmospheric nitrogen species in RMNP from emission sources along the Colorado Front Range versus other areas within Colorado; and identify the relative contributions to atmospheric nitrogen species from mobile sources, agricultural activities, and large and small point sources within the state of Colorado. Measured ammonia concentrations are combined with modeled releases of conservative tracers from ammonia source regions around the United States to apportion ammonia to its respective sources, using receptor modeling tools.

Implications: Increased deposition of nitrogen in RMNP has been demonstrated to contribute to a number of important ecosystem changes. The rate of deposition of nitrogen compounds in RMNP has crossed a crucial threshold called the “critical load.” This means that changes are occurring to park ecosystems and that these changes may soon reach a point where they are difficult or impossible to reverse. Several key issues need attention to develop an effective strategy for protecting park resources from adverse impacts of elevated nitrogen deposition. These include determining the importance of previously unquantified nitrogen inputs within the park and identification of important nitrogen sources and transport pathways.     

A theoretical overview of the relationship between the resource curse and genuine savings as an indicator for “weak” sustainability

This paper shows the strong relation between the factors that lead to the resource curse (RC) and factors that lead to a decline of genuine savings (GS). There is substantial empirical evidence that economies that rely predominantly on their natural resources are also characterized by slower economic growth. This so‐called RC is commonly traced back to the fact that natural resources' generate rents that are independent of a country's economic performance, which can lead to suboptimal reinvestments of this consumed natural capital. We argue that the factors responsible for the RC also have a negative effect on GS, a concept that measures “weak” sustainable development by considering reinvestment of natural capital rents in physical and human capital. We discuss whether the RC hampers possibilities for resource abundant countries to obtain sufficiently high rates of GS, and find indeed many reasons why resource‐dependent countries have problems achieving positive GS rates. We survey both areas of research, emphasizing the influence of the exogenous and endogenous determinants of economic growth, which are usually used to theoretically and empirically explain the RC on the three different forms of capital considered by GS. We specify why most countries suffering from the RC have negative GS rates and explain in detail where the linkages are. This overview could help with potential advancements in the explanation of GS through the inclusion of RC effects.     

Reconstructions of Soil Moisture for the Upper Colorado River Basin Using Tree‐Ring Chronologies1

Anderson, SallyRose, Glenn Tootle, and Henri Grissino‐Mayer, 2012. Reconstructions of Soil Moisture for the Upper Colorado River Basin Using Tree‐Ring Chronologies. Journal of the American Water Resources Association (JAWRA) 48(4): 849‐858. DOI: 10.1111/j.1752‐1688.2012.00651.x Abstract: Soil moisture is an important factor in the global hydrologic cycle, but existing reconstructions of historic soil moisture are limited. We used tree‐ring chronologies to reconstruct annual soil moisture in the Upper Colorado River Basin (UCRB). Gridded soil moisture data were spatially regionalized using principal components analysis and k‐nearest neighbor techniques. We correlated moisture sensitive tree‐ring chronologies in and adjacent to the UCRB with regional soil moisture and tested the relationships for temporal stability. Chronologies that were positively correlated and stable for the calibration period were retained. We used stepwise linear regression to identify the best predictor combinations for each soil moisture region. The regressions explained 42‐78% of the variability in soil moisture data. We performed reconstructions for individual soil moisture grid cells to enhance understanding of the disparity in reconstructive skill across the regions. Reconstructions that used chronologies based on ponderosa pines (Pinus ponderosa) and pinyon pines (Pinus edulis) explained more variance in the datasets. Reconstructed soil moisture data was standardized and compared with standardized reconstructed streamflow and snow water equivalent data from the same region. Soil moisture and other hydrologic variables were highly correlated, indicating reconstructions of soil moisture in the UCRB using tree‐ring chronologies successfully represent hydrologic trends.