Persistence of phorate in soils: role of moisture, temperature, preexposure, and microorganisms

In laboratory incubation studies with three soils of varying physicochemical characteristics, phorate was more persistent in nonflooded (60% water holding capacity) soils than in flooded soils. Phorate sulphoxide was recovered as the only metabolite of phorate in nonflooded soils while three metabolites (diethyl dithiophosphate, triethyl dithiophosphate and an unidentified metabolite) were formed in flooded soils. Study indicates that in nonflooded soils phorate is degraded via oxidation while in flooded soils hydrolysis is the major degradation process. Degradation of phorate was accelerated by an increase in incubation temperature. Preexposure or repeated application of soils to phorate slightly decreased the persistence of phorate or its metabolites. Decreased persistence of phorate and its metabolites formed in nonsterile soils compared to sterile soils suggested the role of microorganisms in their transformation.     

Investigating options for attenuating methane emission from Indian rice fields

The development of methods and strategies to reduce the emission of methane from paddy fields is a central component of ongoing efforts to protect the Earth's atmosphere and to avert a possible climate change. It appears from this investigation that there can be more than one strategy to contain methane emission from paddy fields, which are thought to be a major source of methane emission in tropical Asia. Promising among the mitigating options may be water management, organic amendments, fertilizer application and selection of rice cultivars. It is always better to adopt multi-pronged strategies to contain CH4 efflux from rice wetlands. Use of fermented manures with low C/N ratio, application of sulfate-containing chemical fertilizers, selection of low CH4 emitting rice cultivars, and implementation of one or two short aeration periods before the heading stage can be effective options to minimize CH4 emission from paddy fields. Among these strategies, water management, which appears to be the best cost-effective and eco-friendly way for methane mitigation, is only possible when excess water is available for reflooding after short soil drying at the right timing and stage. However, in tropical Asia, rice fields are naturally flooded during the monsoonal rainy season and fully controlled drainage is often impossible. In such situation, water deficits during the vegetative and reproductive stage may drastically affect the rice yields. Thus, care must be taken to mitigate methane emission without affecting rice yields.     

Financing of wasteland afforestation in India

India has vast tracts of wastelands, which have been lying barren for ages. Most such lands are physically suitable for growing trees and thus could be put to socially productive uses. However, although usually economically viable, afforestation requires massive initial investment, generally beyond the means of the landowners. Also, government budgetary allocations do not cover current needs. In this situation, institutional credit is required. The National Bank for Agriculture and Rural Development (NABARD) of India has recognized this need and has devised a number of different schemes to provide refinance facilities to individuals and organisations. Although the number of forestry schemes refinanced by NABARD has increased rapidly in the past, they currently constitute only about 1% of the total number of loans sanctioned, and only about 2% of NABARD's cumulative loan disbursement to date. In fact, since 1992, the share of afforestation schemes has declined. A number of factors have been identified as major constraints, including time-consuming and complicated procedures for accessing land; restrictions on harvesting and selling trees; delays in sanctioning and disbursement of bank credit; non-remunerative prices for tree products; and flawed public policies and programmes. This article argues that unless these constraints are overcome, NABARD will not be able to play an effective role in speeding up development programmes in the forestry sector. It further argues that most of the current constraints on institutional credit for wasteland afforestation can be removed or relaxed. Practical strategies are suggested to mobilize more funds and channel more institutional credit for wasteland afforestation in India.     

A NEW METHOD FOR ESTIMATING FUTURE RESERVOIR STORAGE CAPACITIES1

ABSTRACT: A new method has been developed for estimating future reservoir storage capacities, allowing for sediment deposition and compaction. Reservoir sedimentation surveys for 117 reservoirs, conducted by the Illinois State Water Survey over the past 60 years, were used to determine regional constants K to represent the severity of sediment deposition in the reservoirs. More than half of the 82 water supply reservoirs investigated had records of reservoir sedimentation surveys, and their K values were calculated by using data from those sediment surveys. The average K values of the remaining non-surveyed water supply reservoirs were estimated from the regional distribution of the K values. Other important factors considered in the estimation of future reservoir storage capacities are the trap efficiency of the reservoirs and the variation of density of sediment deposits due to compaction. The model can also be used for analyzing the economics of alternative sites and of design features that can be incorporated in dams for reducing reservoir sedimentation.     

UNIT HYDROGRAPHS FOR DEVELOPING DESIGN FLOOD HYDROGRAPHS1

ABSTRACT: In Illinois, a procedure has been developed to derive unit hydrographs for generating 100-year and probable maximum flood hydrographs, on the basis of 11 parameters that define the hydrograph shape very well. Regional regressions of these parameters with basin factors show very high correlation. Thus satisfactory values of parameters can be determined for ungaged areas or those with a few years' record. The nonlinearity in unit hydrographs derived from usual floods is largely attributed to mixing within-channel and overbank-flow flood events. To minimize the effects of nonlinearity and to derive unit hydrographa suitable for calculating spillway design floods, use of the proposed method of developing such hydrographs is recommended.     

Degradation of Commercial Biodegradable Packages under Real Composting and Ambient Exposure Conditions

The use of long-lasting polymers as packaging materials for short lived applications is not entirely justified. Plastic packaging materials are often soiled due to foodstuffs and other biological substances, making physical recycling of these materials impractical and normally unwanted. Hence, there is an increasing demand for biodegradable packaging materials which could be easily renewable. Use of biopolymer based packaging materials allows consideration of eliminating issues such as landfilling, sorting and reprocessing through taking advantage of their unique functionality, that is compostability. Composting allows disposal of biodegradable packages and is not as energy intensive compared to sorting and reprocessing for recycling, although it requires more energy than landfilling. The aim of this work was to study the degradation of three commercially available biodegradable packages made of poly (ld-lactide) (PLA) under real compost conditions and under ambient exposure by visual inspection, gel permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. A novel technique to study the degradability of these packages and to track the degradation rate under real compost conditions was used. The packages were subjected to composting for 30 days, and the degradation of the physical properties was measured at 1, 2, 4, 6, 9, 15 and 30 days. PLA packages made of 96% l-lactide exhibited lower degradation than PLA packages made of 94% l-lactide, mainly due to their highly ordered structure, therefore, higher crystallinity. The degradation rate changed as the initial crystallinity and the l-lactide content of the packages varied. Temperature, relative humidity, and pH of the compost pile played an important role in the total degradation of the packages. A first order degradation of the molecular weight as a function of time was observed for the three packages.     

Degradation of a Terephthalate-containing Polyester by a Thermophilic Microbial Consortium

Biomax^® is an aliphatic-aromatic polyester. The biodegradability of Biomax^® was studied at 58 °C using a laboratory scale bioreactor. The bioreactor was inoculated with bacteria derived from compost and supplemented with powdered Biomax^® and an additional energy source. After a period of acclimation, the microorganisms in the bioreactor were capable of metabolizing the major components of the polymer, i.e., TPA and ethylene glycol. TPA and ethylene glycol were detected in the bioreactor only when they were added. Degradation and disintegration of the powdered Biomax^® was monitored by laser diffraction. The particle size distribution of the powdered polymer progressively shifted toward smaller sizes until the diameters of the polymer particles were indistinguishable from bacteria. The types of microbes in the bioreactor were determined by analyzing 16S rRNA gene sequences. The bacteria belonged to 35 different groups, and the majority of the bacteria appeared to represent new species.     

ROLE OF BASEFLOW IN RAINFALL-RUNOFF RELATIONS1

ABSTRACT. The role of initial baseflow, or the baseflow at the beginning of storm precipitation, in modifying mathematical rainfall-runoff relations is analyzed by using data from 95 storms over a drainage basin in Illinois. A regression model is set up with total runoff, surface runoff, baseflow runoff, and peak flow as dependent variables, and storm precipitation, initial baseflow, effective and total storm durations, and highest and lowest temperatures during the storm as independent variables. Stepwise regression analyses show that storm precipitation and initial baseflow are the most important variables for making dependent variable estimates. The standard error estimates using only storm precipitation and initial baseflow as predictors show a seasonal trend with a peak in July, August, or September. An understanding of the role of baseflow as an indicator of average soil moisture condition over the basin can be of great help in short-term reservoir regulation and flood warning.     

Vertical and horizontal movement of phorate and its metabolites in field soil under cropped and uncropped conditions

Vertical and horizontal movement of phorate and its metabolites in field microplots was studied under cropped and uncropped conditions in winter and summer seasons. Phorate bands were placed 2.5 cm below the soil surface and were subject to leaching by irrigation and rain. The crops used were peas, in winter, and maize, in summer. Periodic analyses of samples showed that total phorate residues (TPR) were significantly more mobile under cropped conditions than in fallow conditions in both seasons. The peak concentration depth remained at 7.5 cm throughout most of the experimental period. Irrespective of treatments, downward movement of TPR was greater in winter. Horizontal movement of TPR was greater under cropped conditions in summer. Differences in lateral mobility were insignificant in two seasons under cropped conditions. However, under uncropped conditions, horizontal movement was relatively more in the summer season. TPR persisted in the soil for 120 and 90 days in winter and summer, respectively. The TPR persistence was almost the same in the two crops. Maize and pea plants at harvest had residues below the legal health tolerance limit. Half-life values of TPR in maize and pea plants were 38 and 42 days, respectively.     

Total bacterial and fungal population after chlorpyrifos and quinalphos treatments in groundnut (Arachis hypogaea L.) soil

Short-term inhibitory effect on the total bacterial population was observed after chlorpyrifos and quinalphos applications in the groundnut fields, which recovered within 60 days after seed treatment and by 45 days of soil treatment. The fungal population was significantly enhanced after chlorpyrifos treatment whereas quinalphos inhibited the fungal population during the initial days of treatment but no effect was observed after 60 days of treatment. The residues of chlorpyrifos and quinalphos in the treated soil were not persistent and their half-lives ranged from 7.0 to 9.2 days and 13.2 to 20.6 days, respectively.