Active carbon-pools in rhizosphere of wheat (Triticum aestivum L.) grown under elevated atmospheric carbon dioxide concentration in a Typic Haplustept in sub-tropical India

Study on active and labile carbon-pools can serve as a clue for soil organic carbon dynamics on exposure to elevated level of CO2. Therefore, an experimental study was conducted in a Typic Haplustept in sub-tropical semi-arid India with wheat grown in open top chambers at ambient (370 micromol mol-1) and elevated (600 micromol mol-1) concentrations of atmospheric CO2. Elevated atmospheric CO2 caused increase in yield and carbon uptake by all plant parts, and their preferential partitioning to root. Increases in fresh root weight, volume and length have also been observed. Relative contribution of medium-sized root to total root length increased at the expense of very fine roots at elevated CO2 level. All active carbon-fractions gained due to elevated atmospheric CO2 concentration, and the order followed their relative labilities. All the C-pools have recorded a significant increase over initial status, and are expected to impart short-to-medium-term effect on soil carbon sequestration.     

Characterization and source identification of polycyclic aromatic hydrocarbons (PAHs) in the urban environment of Delhi

This paper reports on polycyclic aromatic hydrocarbons (PAHs) in the atmospheric particulate matter of Jawaharlal Nehru University campus, an urbanized site of New Delhi, India. Suspended particulate matter samples of 24h duration were collected on glass-fiber filter paper for four representative days in each month during January 2002 to December 2003. PAHs were extracted from filter papers using toluene with ultrasonication method and analysed. Quantitative measurements of polycyclic aromatic hydrocarbons (PAHs) were carried out using the gas chromatography technique. The annual average concentration of total PAHs were found to be 668+/-399 and 672+/-388 ng/m3 in the years 2002 and 2003, respectively. The seasonal average concentrations were found to be maximum in winter and minimum during in the monsoon. The results of principal component analysis (PCA) indicate that diesel and gasoline driven vehicles are the principal sources of PAHs in all the seasons. In winter coal and wood combustion also significantly contribute to the PAH levels.     

Exposure and health risks potentially posed to petroleum storage tank cleaners by volatile organic compounds

This study models and assesses the significance of risks to health potentially posed to individuals exposed to volatile organic compounds (VOCs) due to being occupationally engaged in cleaning petroleum storage tanks. Exposure processes include hydrocarbon vapor inhalation, ingestion via hand-to-mouth contact, and dermal exposure. Under confined space entry regulations, tank cleaners must wear protective clothing and a breathing apparatus. However, such regulations are recent and sometimes violated. Several factors were found to influence exposure of unprotected individuals cleaning tanks. One factor is climate. This paper reports on a study of tanks in south Texas, which is sunny and hot during most of the year. Solar irradiation of metal surfaces may elevate internal temperatures above ambient air temperatures. Vaporization then elevates airborne hydrocarbon concentrations, and ventilation reduces them, producing a dynamic equilibrium. Human entry, however, disturbs this equilibrium by agitating petroleum residuals. Based upon the above considerations, we have modeled petroleum fuel storage tank dynamics in a case study. We considered three cases: manways closed, manways open, and manways actively ventilated. For CASE I, the concentration of each pollutant in the vapor phase was calculated using Raoult's Law. CASE II and CASE III applied Raoult's Law and also evaluated a mass balance via a mass transfer coefficient derived using the Reynolds Number and the Schmidt Number. Based upon empirical data, the velocity of the air within the tank was assumed to be 1.6 mph. Outputs of the case study included the steady-state concentration of each constituent and time required to reach it. Health risk assessment was conducted to quantify non-cancer risks posed by individual substances (the hazard quotient, HQ) and by simultaneous and/or sequential exposure to multiple substances (the hazard index, HI). During hot months, gross exceedances of acceptability criteria for acute and chronic exposures to mixed solvent vapors occurred. The HI exceeded the acceptability criterion by more than three orders of magnitude. The HI for chronic occupational neurological risks exceeded the acceptability criterion by more than two orders of magnitude. This result is consistent with observed neurological deficits among tank cleaners, such as depression of performance on memory tests among crew members who had worked during hot months. Finally, in such instances, eight-hour time-weighted average mixed-solvent vapor concentrations can exceed half of lethal levels, suggesting that tank cleaners can potentially approach lethal exposure routinely during hot seasons.     

Transient design of landfill liquid addition systems

This study presents the development of design charts that can be used to estimate lateral and vertical spacing of liquids addition devices (e.g., vertical well, horizontal trenches) and the operating duration needed for transient operating conditions (conditions until steady-state operating conditions are achieved). These design charts should be used in conjunction with steady-state design charts published earlier by Jain et al., 2010a, Jain et al., 2010b. The data suggest that the liquids addition system operating time can be significantly reduced by utilizing moderately closer spacing between liquids addition devices than the spacing needed for steady-state conditions. These design charts can be used by designers to readily estimate achievable flow rate and lateral and vertical extents of the zone of impact from liquid addition devices, and analyze the sensitivity of various input variables (e.g., hydraulic conductivity, anisotropy, well radius, screen length) to the design. The applicability of the design charts, which are developed based on simulations of a continuously operated system, was also evaluated for the design of a system that would be operated intermittently (e.g., systems only operated during facility operating hours). The design charts somewhat underestimates the flow rate achieved and overestimates the lateral extent of the zone of impact over an operating duration for an intermittently operated system. The associated estimation errors would be smaller than the margin of errors associated with measurement of other key design inputs such as waste properties (e.g., hydraulic conductivity) and wider variation of these properties at a given site due to heterogeneous nature of waste.     

Concentrations of selected metals in blood,serum, and urine among US adult exclusive users of cigarettes,cigars, and electronic cigarettes

Data from National Health and Nutrition Examination Survey for 2013–2014 were used to compare observed levels of selected metals in blood, serum, and urine among US adults aged ≥20 years for exclusive cigar, cigarettes, and e-cigarette users. Adjusted geometric means for e-cigarette users were found to be higher than for cigar users for blood manganese (10.3 vs. 7.9 µg/L, p = 0.02). Cigar users were found to have lower adjusted geometric means than cigarette users for urine cobalt (0.22 vs. 0.4 µg/L, p = 0.04) and urine antimony (0.03 vs. 0.06 µg/L, p = 0.03). Adjusted levels of blood selenium, serum copper, selenium, and zinc, and urine arsenic, barium, molybdenum, tin, strontium, thallium, tungsten, and uranium were found to be comparable among cigarettes only, cigar only, and electronic cigarettes only users. However, irrespective of the comparative levels of these metals among cigar, cigarette, and e-cigarette users, focus must be to assess the short- and long-term health effects of the exposure to these metals particularly nanoparticles via inhalation from e-cigarette aerosols.     

“NEW” resource recovery from wastewater using bioelectrochemical systems: Moving forward with functions

Bioelectrochemical systems (BES) have been extensively studied for resource recovery from wastewater. By taking advantage of interactions between microorganisms and electrodes, BES can accomplish wastewater treatment while simultaneously recovering various resources including nutrients, energy and water (“NEW”). Despite much progress in laboratory studies, BES have not been advanced to practical applications. This paper aims to provide some subjective opinions and a concise discussion of several key challenges in BES-based resource recovery and help identify the potential application niches that may guide further technological development. In addition to further increasing recovery efficiency, it is also important to have more focus on the applications of the recovered resources such as how to use the harvested electricity and gaseous energy and how to separate the recovered nutrients in an energy-efficient way. A change in mindset for energy performance of BES is necessary to understand overall energy production and consumption. Scaling up BES can go through laboratory scale, transitional scale, and then pilot scale. Using functions as driving forces for BES research and development will better guide the investment of efforts.

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Effect of hypoxia on the circulating levels of essential mineral elements in rats

Changes occurring in concentrations of certain trace metals and electrolytes viz. chromium, copper, zinc, sodium, potassium, calcium, magenesium and chloride in plasma of rats exposed to intermittent hypobaric hypoxia were evaluated. Batches of Sprague-Dowley rats (12 in each group) were exposed for 1, 7,14 and 21 days to a simulated altitude 7,620 m for 6 h per day and one group of unexposed animals was kept as control. There was a significant rise of 153% in plasma chromium levels of 1 day exposed group in comparison to the unexposed group which tends to normalise on subsequent exposure. There was a gradual increase in plasma copper levels of 9.0, 28.2, 62.6 and 65.6% respectively in 1,7,14 and 21 days exposed rats in comparison to unexposed rats. On the other hand plasma zinc levels were seen to be decreasing during entire exposure. Plasma sodium levels decreased initially in 1 and 7 day exposed rats and increased in later groups whereas plasma potassium levels of exposed groups remained low in comparison to unexposed group. Chloride levels were found to be elevated in 14 and 21 day exposed groups. The plasma calcium and magnesium levels were higher in all exposed groups over unexposed groups. Changes in chromium, copper and zinc observed in the present study during exposure to hypoxic stress may be responsible for the hyperglycemia and anorexia encountered during intial phase of high altitude acclimatisation.     

Heavy metal content in soil reclaimed from a municipal solid waste landfill

Residues reclaimed from a municipal solid waste (MSW) landfill were characterized for the concentrations of a number of heavy metals. The residue fractions analyzed included a fine fraction (<0.425 mm), an intermediate fraction (>0.425 and <6.3 mm) and a fraction consisting of paper products that could ultimately degrade to a smaller size. The intermediate fraction appeared to be organic in nature, while the fine fraction was more soil-like. In general, the metal concentrations were greatest in the intermediate fraction and lowest in the fine fraction. The effect of sample age on the elemental content was also investigated. The concentrations of several elements were greater in older samples (sample approximately 8 years in age) when compared to newer samples (sample approximately 3 years in age). Limitations associated with the land application of residual soil (composed of the fine and intermediate fractions) were assessed by comparing measured concentrations to regulatory threshold values. In general, most metal concentrations were below regulatory thresholds for use in unrestricted settings. At the concentrations measured, however, several elements might limit reuse options, depending on which regulatory threshold serves as a benchmark. Elevated concentrations of arsenic presented the greatest limitation with respect to common US thresholds while elevated cadmium concentrations presented the greatest limitation when compared to UK thresholds. The source of the arsenic was determined to be the waste, not the cover soil.     

Mitigating nitrous oxide and methane emissions from soil in rice-wheat system of the Indo-Gangetic plain with nitrification and urease inhibitors

Mitigation of methane (CH4) and nitrous oxide (N2O) emissions from soil is important to reduce the global warming. Efficacy of five nitrification inhibitors, i.e. neem (Azadirachta melia) cake, thiosulphate, coated calcium carbide, neem oil coated urea and dicyandiamide (DCD) and one urease inhibitor, hydroquinone, in mitigating N2O and CH4 emissions from fertilized soil was tested in rice-wheat system in the Indo-Gangetic plains. The closed chamber technique was used for the collection of gas samples, which were analyzed using gas chromatography. Reduction in N2O emission on the application of nitrification/urease inhibitors along with urea ranged from 5% with hydroquinone to 31% with thiosulphate in rice and 7% with hydroquinone to 29% with DCD in wheat crop. The inhibitors also influenced the emission of CH4. While application of neem coated urea, coated calcium carbide, neem oil and DCD reduced the emission of CH4; hydroquinone and thiosulphate increased the emission when compared to urea alone. However, the global warming potential was lower with the inhibitors (except hydroquinone) as compared to urea alone, suggesting that these substances could be used for mitigating greenhouse gas emission from the rice-wheat systems.