The effect of fonofos and carbofuran on microbiological population, and persistence of fonofos in four organic soils infested with onion maggot

One hundred days after field-application of fonofos as bands under the onion seed, 39 to 59% of that material was present in 3 moderately humified organic soils of pH varying from 5.4 to 6.7. In a low humified organic soil, only 21 to 24% of the applied fonofos remained. Thus humus enhanced the persistence of fonofos and curtailed the stimulating effect of fonofos on soil microbial populations. An assessment of low damage caused by onion maggot was found in a poorly humified soil with an even higher natural infestation than in a moderately humified soil. The effects of fonofos in other soils and of the low rate of carbofuran applied to four different types of soils on the numbers of fungi, bacteria, and actinomycetes were difficult to assess.     

Bricks as historical record of heavy metals fallout: Study on copper accumulation in Agra soils since 1910

Peat, ice deposits and aquatic sediments, which have been used as a geochemical monitor of atmospheric heavy metal pollution until now, are open and dynamic systems and can be easily affected by climatic variations. In contrast, bricks, which are more compact, can act as a better geochemical monitor. Analysis of Cu, Cr, Ni, Pb and Zn in scores of soil and brick (baked/unbaked) samples, collected from a large area in and around a rapidly growing Indian city, Agra, reveals approximately similar concentrations in soils and bricks, thereby showing insignificant fractionation of these metals during brick making. Further, metals concentration in the core of bricks remains unaffected by any significant amount of acidic and alkaline rain. Thus, the feasibility of a novel role of bricks as a geochemical monitor of atmospheric heavy metal pollution has been tested. Utilizing this concept, an attempt has also been made to trace the history of atmospheric copper depositions in the soils of Agra during the last 100 years.     

Performance and diagnostic evaluation of ozone predictions by the Eta-Community Multiscale Air Quality Forecast System during the 2002 New England Air Quality Study

A real-time air quality forecasting system (Eta-Community Multiscale Air Quality [CMAQ] model suite) has been developed by linking the National Centers for Environmental Estimation Eta model to the U.S. Environmental Protection Agency (EPA) CMAQ model. This work presents results from the application of the Eta-CMAQ modeling system for forecasting ozone (O3) over the Northeastern United States during the 2002 New England Air Quality Study (NEAQS). Spatial and temporal performance of the Eta-CMAQ model for O3 was evaluated by comparison with observations from the EPA Air Quality System (AQS) network. This study also examines the ability of the model to simulate the processes governing the distributions of tropospheric O3 on the basis of the intensive datasets obtained at the four Atmospheric Investigation, Regional Modeling, Analysis, and Estimation (AIRMAP) and Harvard Forest (HF) surface sites. The episode analysis reveals that the model captured the buildup of O3 concentrations over the northeastern domain from August 11 and reproduced the spatial distributions of observed O3 very well for the daytime (8:00 p.m.) of both August 8 and 12 with most of normalized mean bias (NMB) within +/- 20%. The model reproduced 53.3% of the observed hourly O3 within a factor of 1.5 with NMB of 29.7% and normalized mean error of 46.9% at the 342 AQS sites. The comparison of modeled and observed lidar O3 vertical profiles shows that whereas the model reproduced the observed vertical structure, it tended to overestimate at higher altitude. The model reproduced 64-77% of observed NO2 photolysis rate values within a factor of 1.5 at the AIRMAP sites. At the HF site, comparison of modeled and observed O3/nitrogen oxide (NOx) ratios suggests that the site is mainly under strongly NOx-sensitive conditions (>53%). It was found that the modeled lower limits of the O3 production efficiency values (inferred from O3-CO correlation) are close to the observations.     

EFFECTS OF VARIABLE DISCHARGE SCHEMES ON DISSOLVED OXYGEN AT A HYDROELECTRIC STATION1

ABSTRACT: The effects of variable discharges during the summer on the dissolved oxygen (DO) content and water temperature upstream and downstream of the Conowingo Hydroelectric Power Station were investigated. The DO dynamics are controlled primarily by meteorological factors that are independent of the mode of hydrostation operation. DO stratification occurred during the summer in Conowingo Pond, but thermal stratification was not observed. The magnitude and duration of off-peak discharges including a run-of-the-river operation did not affect DO stratification in Conowingo Pond; little vertical mixing occurred. However, strong winds and/or high river flows temporarily destroyed DO stratification. The run-of-the-river operation or off-peak continuous discharge schemes did not provide better DO conditions downstream of the hydrostation than the peaking operation with intermittent off-peak releases. A statistical model predicted that a DO of 5 ppm occurs 0.6 miles downstream of the powerhouse when the natural river flow is consistently greater than 15,000 cfs and water temperature is less than 80°F. A mean daily DO of at least 4 ppm was predicted to occur over 80 percent of the time during the 92-day summer period. Farther downstream (1.3 miles from the powerhouse) a mean daily DO of at least 4 ppm was predicted to occur 90 percent of the time in summer.     

Occurrence of phthalic acid esters in Gomti River Sediment, India

Cadmium and lead are important environmental pollutants with high toxicity to animals and human. Soils, though have considerable metal immobilizing capability, can contaminate food chain via plants grown upon them when their built-up occurs to a large extent. Present experiment was carried out with the objective of quantifying the limits of Pb and Cd loading in soil for the purpose of preventing food chain contamination beyond background concentration levels. Two separate sets of pot experiment were carried out for these two heavy metals with graded levels of application doses of Pb at 0.4–150 mg/kg and Cd at 0.02–20 mg/kg to an acidic light textured alluvial soil. Spinach crop was grown for 50 days on these treated soils after a stabilization period of 2 months. Upper limit of background concentration levels (C _ul) of these metals were calculated through statistical approach from the heavy metals concentration values in leaves of spinach crop grown in farmers’ fields. Lead and Cd concentration limits in soil were calculated by dividing C _ul with uptake response slope obtained from the pot experiment. Cumulative loading limits (concentration limits in soil minus contents in uncontaminated soil) for the experimental soil were estimated to be 170 kg Pb/ha and 0.8 kg Cd/ha. Based on certain assumptions on application rate and computed cumulative loading limit values, maximum permissible Pb and Cd concentration values in municipal solid waste (MSW) compost were proposed as 170 mg Pb/kg and 0.8 mg Cd/kg, respectively. In view of these limiting values, about 56% and 47% of the MSW compost samples from different cities are found to contain Pb and Cd in the safe range.     

Vegetation exposure to ozone over the continental United States: Assessment of exposure indices by the Eta-CMAQ air quality forecast model

The main use of air quality forecast (AQF) models is to predict ozone (O₃) exceedances of the primary O₃ standard for informing the public of potential health concerns. This study presents the first evaluation of the performance of the Eta-CMAQ air quality forecast model to predict a variety of widely used seasonal mean and cumulative O₃ exposure indices associated with vegetation using the U.S. AIRNow O₃ observations. These exposure indices include two concentration-based O₃ indices, M7 and M12 (the seasonal means of daytime 7-h and 12-h O₃ concentrations, respectively), and three cumulative exposure-based indices, SUM06 (the sum of all hourly O₃ concentrations ≥ 0.06 ppm), W126 (hourly concentrations weighed by a sigmoidal weighting function), and AOT40 (O₃ concentrations accumulated over a threshold of 40 ppb during daylight hours). During a three-month simulation (July–September 2005), the model over predicted the M7 and M12 values by 8–9 ppb, or a NMB value of 19% and a NME value of 21%. The model predicts a central belt of high O₃ extending from Southern California to Middle Atlantic where the seasonal means, M7 and M12 (the seasonal means of daytime 7-h and 12-h O₃ concentrations), are higher than 50 ppbv. In contrast, the model is less capable of reproducing the observed cumulative indices. For AOT40, SUM06 and W126, the NMB and NME values are two- to three-fold of that for M7, M12 or peak 8-h O₃ concentrations. The AOT40 values range from 2 to 33 ppm h by the model and from 1 to 40 ppm h by the monitors. There is a significantly higher AOT40 value experienced in the United States in comparison to Europe. The domain-wide mean SUM06 value is 14.4 ppm h, which is about 30% higher than W126, and 40% higher than AOT40 calculated from the same 3-month hourly O₃ data. This suggests that SUM06 and W126 represent a more stringent standard than AOT40 if either the SUM06 or the W126 was used as a secondary O₃ standard. Although CMAQ considerably over predicts SUM06 and W126 values at the low end, the model under predicts the extreme high exposure values (>50 ppm h). Most of these extreme high values are found at inland California sites. Based on our analysis, further improvement of the model is needed to better capture cumulative exposure indices.     

Performance and Diagnostic Evaluation of Ozone Predictions by the Eta-Community Multiscale Air Quality Forecast System during the 2002 New England Air Quality Study

Abstract

A real-time air quality forecasting system (Eta-Community Multiscale Air Quality [CMAQ] model suite) has been developed by linking the National Centers for Environmental Estimation Eta model to the U.S. Environmental Protection Agency (EPA) CMAQ model. This work presents results from the application of the Eta-CMAQ modeling system for forecasting ozone (O₃) over the Northeastern United States during the 2002 New England Air Quality Study (NEAQS). Spatial and temporal performance of the Eta-CMAQ model for O₃ was evaluated by comparison with observations from the EPA Air Quality System (AQS) network. This study also examines the ability of the model to simulate the processes governing the distributions of tropospheric O₃ on the basis of the intensive datasets obtained at the four Atmospheric Investigation, Regional Modeling, Analysis, and Estimation (AIRMAP) and Harvard Forest (HF) surface sites. The episode analysis reveals that the model captured the buildup of O₃ concentrations over the northeastern domain from August 11 and reproduced the spatial distributions of observed O₃ very well for the daytime (8:00 p.m.) of both August 8 and 12 with most of normalized mean bias (NMB) within [H11006]20%. The model reproduced 53.3% of the observed hourly O₃ within a factor of 1.5 with NMB of 29.7% and normalized mean error of 46.9% at the 342 AQS sites.The comparison of modeled and observed lidar O₃ vertical profiles shows that whereas the model reproduced the observed vertical structure, it tended to overestimate at higher altitude. The model reproduced 64 –77% of observed NO₂ photolysis rate values within a factor of 1.5 at the AIRMAP sites. At the HF site, comparison of modeled and observed O₃/nitrogen oxide (NO_x) ratios suggests that the site is mainly under strongly NO_x-sensitive conditions (>53%). It was found that the modeled lower limits of the O₃ production efficiency values (inferred from O₃-CO correlation) are close to the observations.