Conservation agricultural practices for minimizing ammonia volatilization and maximizing wheat productivity

Environmental Science and Pollution Research - A large amount of ammonia volatilization from the agricultural system causes environmental problems and increases production costs. Conservation...     

Open-path tunable diode laser absorption spectroscopy for acquisition of fugitive emission flux data

Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. Environmental Protection Agency (EPA) has developed a ground-based optical remote-sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transform infrared spectroscopy (OP-FTIR) has been the primary technique for acquisition of pollutant concentration data used in this emission measurement method. For a number of environmentally important compounds, such as ammonia and methane, open-path tunable diode laser absorption spectroscopy (OP-TDLAS) is shown to be a viable alternative to Fourier transform spectroscopy for pollutant concentration measurements. Near-IR diode laser spectroscopy systems offer significant operational and cost advantages over Fourier transform instruments enabling more efficient implementation of the measurement strategy. This article reviews the EPA's fugitive emission measurement method and describes its multipath tunable diode laser instrument. Validation testing of the system is discussed. OP-TDLAS versus OP-FTIR correlation testing results for ammonia (R2 = 0.980) and methane (R2 = 0.991) are reported. Two example applications of tunable diode laser-based fugitive emission measurements are presented.     

Effect of concentration,moisture and soil type on the dissipation of flufenacet from soil

Effect of concentration, moisture and soil type on dissipation of flufenacet from soil has been studied under laboratory condition. The treated soil samples (1 and 10 microg/g levels) were incubated at 25+/-1 degrees C. The effect of moisture was studied by maintaining the treated soil samples (10 microg/g level) at field capacity and submerged condition. In general, flufenacet persisted for 60-90 days at lower and beyond 90 days at high rate. The dissipation of flufenacet from soil followed first order kinetics with half-life (DT50) values ranging from 10 to 31 days. The dissipation of flufenacet was faster at low rate than high rate of application. The slow dissipation at high rate could be attributed to inhibition of microbial activity at high rate. There was little overall difference in rate of dissipation in Ranchi and Nagpur soil maintained at field capacity and submerged condition moisture regimes. In Delhi soil net dissipation was faster under field capacity moisture than submerged condition. Soil types greatly influenced the dissipation of flufenacet. Dissipation was fastest in Delhi soil (DT50 10.1-22.3 days) followed by Ranchi soil (DT50 10.5-24.1 days) and least in Nagpur soil (DT50 29.2-31.0 days). The difference in dissipation could be attributed to the magnitude of adsorption and desorption of flufenacet in these soils.     

Parameter estimation for fractional dispersion model for rivers

The fractional dispersion model for natural rivers, extended by including a first order reaction term, contains four parameters. In order to estimate these parameters a fractional Laplace transform-based method is developed in this paper. Based on 76 dye test data measured in natural streams, the new parameter estimation method shows that the fractional dispersion operator parameter F is the controlling parameter causing the non-Fickian dispersion and F does not take on an integer constant of 2 but instead varies in the range of 1.4–2.0. The adequacy of the fractional Laplace transform-based parameter estimation method is determined by computing dispersion characteristics of the extended fractional dispersion model and these characteristics are compared with those observed from 12 dye tests conducted on the US rivers, including Mississippi, Red, and Monocacy. The agreement between computed and observed dispersion characteristics is found to be good. When combined with the fractional Laplace transform-based parameter estimation method, the extended fractional dispersion model is capable of accurately simulating the non-Fickian dispersion process in natural streams.     

Prenatal exclusion of haemophilia a and carrier testing by direct detection of a disease lesion

A novel mutation was detected in the Factor VIII gene of a sporadic case of severe haemophilia A. The lesion, a CGA → TGA transition, converts Arg 795 to Term and adequately accounts for the severe phenotype observed. PCR/direct sequencing was used to confirm the carrier status in the mother. Exclusion of haemophilia A in an at-risk pregnancy was then achieved by demonstration of the absence of this lesion in fetal DNA from a chorionic villus sample. The mutation was also detectable by chemical cleavage of mismatch (CCM), which both confirmed the prenatal diagnosis and established the carrier status of the proband's sister. This example therefore serves to illustrate the potential of direct gene analysis in sporadic cases of haemophilia A and/or in families uninformative for known RFLPs.     

Effects of hexachlorocyclohexane administration on distribution of trace metals in rat tissues

The effects of daily administration of hexachlorocyclohexane (HCH) for 90 days on the distribution of Cu, Zn, Fe and Mn in rat tissues were investigated. The results indicated that HCH caused a significant increase in weight of liver and spleen and decrease in the weight of kidney, heart and brain. The spleen and heart demonstrated the maximum mobilization of metals. Comparing the individual trace elements, zinc appeared to be the most active element. None of the metals assayed registered change in RBC's but there was increase in Zn, Fe and Mn concentration in plasma.     

Analytical solution of two-dimensional advection–dispersion equation with spatio-temporal coefficients for point sources in an infinite medium using Green’s function method

In the present study analytical solutions of a two-dimensional advection–dispersion equation (ADE) with spatially and temporally dependent longitudinal and lateral components of the dispersion coefficient and velocity are obtained using Green’s Function Method (GFM). These solutions describe solute transport in infinite horizontal groundwater flow, assimilating the spatio-temporal dependence of transport properties, dependence of dispersion coefficient on velocity, and the particulate heterogeneity of the aquifer. The solution is obtained in the general form of temporal dependence and the source term, from which solutions for instantaneous and continuous point sources are derived. The spatial dependence of groundwater velocity is considered non-homogeneous linear, whereas the dispersion coefficient is considered proportional to the square of spatial dependence of velocity. An asymptotically increasing temporal function is considered to illustrate the proposed solutions. The solutions are validated with the existing solutions derived from the proposed solutions in three special cases. The effect of spatially/temporally dependent heterogeneity on the solute transport is also demonstrated. To use the GFM, the ADE with spatio-temporally dependent coefficients is reduced to a dispersion equation with constant coefficients in terms of new position variables introduced through properly developed coordinate transformation equations. Also, a new time variable is introduced through a known transformation.     

Spatial economic theory of pollution control

In February 1972 the Nixon Administration proposed a tax on sulfur oxide emissions, beyond the Federal standards, of electric power plants. It was hoped that such a tax would discourage power plant locations in heavily polluted areas like urban areas. Assuming that such a tax varies over space because pollution is not invariant over space, the spatial theory of the firm is presented in this paper cast doubt on the efficacy of such a polltuion tax to achieve the desired goal of the administration. In particular it is shown that the cost-minimizing spatial firm would abate its pollution in response to a tax by either changing its location or by reducing waste through process change or by using a transportable abatement good if the tax savings due to the change in marginal abatement through location change per unit change in abatement is greater than or equal to transport rate on the abatement good. If the goal of the firm is to maximize profits, the desired outcome would follow if in addition to the fulfillment of the above condition the percentage change in the delivered price of raw material (situated at one end of the linear location space) per unit distance is greater than or equal to the percentage change in net marginal revenue, i.e., marginal revenue net of transport cost per unit of output. In simple terms, the conclusions of this paper raise doubts regarding the effectiveness of a pollution tax in curtailing pollution of a firm which is operating in a space economy. This outcome is peculiar to a spatial firm. Sufficient conditions also have been obtained when land input is included in the production function of the firm.     

Identifying and Evaluating a Suitable Index for Agricultural Drought Monitoring in the Texas High Plains

Drought is a complex and highly destructive natural phenomenon that affects portions of the United States almost every year, and severe water deficiencies can often become catastrophic for agricultural production. Evapotranspiration (ET) by crops is an important component in the agricultural water budget; thus, it is advantageous to include ET in agricultural drought monitoring. The main objectives of this study were to (1) conduct a literature review of drought indices with a focus to identify a simple but simultaneously adequate drought index for monitoring agricultural drought in a semiarid region and (2) using the identified drought index method, develop and evaluate time series of that drought index for the Texas High Plains. Based on the literature review, the Standardized Precipitation‐Evapotranspiration Index (SPEI) was found to satisfy identified constraints for assessing agricultural drought. However, the SPEI was revised by replacing reference ET with potential crop ET to better represent actual water demand. Data from the Texas High Plains Evapotranspiration network was used to calculate SPEIs for the major irrigated crops. Trends and magnitudes of crop‐specific, time‐series SPEIs followed crop water demand patterns for summer crops. Such an observation suggests that a modified SPEI is an appropriate index to monitor agricultural drought for summer crops, but it was found to not account for soil water stored during the summer fallow period for winter wheat.     

Chronotype differences in Drosophila are enhanced by semi-natural conditions

Morning and evening chronotypes of sleep/wake cycles in humans are often metaphorically termed as ‘larks’ and ‘owls’. We derived Drosophila populations early and late, displaying lark- and owl-like emergence chronotypes by imposing selection for adult emergence during morning and evening hours. Preference for morning and evening emergence in these populations was accompanied by divergence in their circadian period (τ) and photic phase response curve. To test if lark- and owl-like emergence chronotypes displayed by these flies under weak environmental cycles of the laboratory would also persist in nature where several zeitgebers are present in the strongest form, we examined the emergence rhythm of early and late flies under semi-natural conditions. The early and late flies not only continued to exhibit divergent emergence waveforms under semi-natural conditions, the differences became even more prominent. However, phases of early and late emergence waveforms did not match natural morning and evening transitions, unlike that observed under laboratory conditions. These results thus provide evidence consistent with the notion that chronotypes are the result of interactions between circadian clocks and natural environmental cycles.