Water distribution system failure: a framework for forensic analysis

The main purpose of a water distribution system (WDS) is to deliver safe water of desirable quality, quantity and continuity to consumers. However, in many cases, a WDS fails to fulfill its goal owing to structural and associated hydraulic failures and/or water quality failures. The impact of these failures can be reduced significantly if preventive actions are taken based on their potential of occurrences or if a failure occurs and is detected within a minimum period of time after its occurrence. The aim of this research was to develop a forensic system for WDS failures. As part of the proposed forensic analysis, a framework has been developed, which investigates structural and associated hydraulic failures as well as water quality failures and integrates all failure investigation under a single platform. Under this framework, four different models have been developed to evaluate and identify structural and associated hydraulic failures and water quality failures. If a failure is detected in the system, the framework is capable of identifying the most probable location of the failure. To investigate the effectiveness of the proposed framework, the developed models have been tested and implemented in different WDSs.     

Insecticide substitutes for DDT to control mosquitoes may be causes of several diseases

Malaria continues to be a public health problem in Bangladesh, despite efforts in the 1960s to eradicate the vectors through the use of DDT. At one point, eradication of malaria was acclaimed but later on it reappeared. The use of DDT is no more legally allowed in Bangladesh, which has been officially replaced by a number organophosphates and/or synthetic pyrethroids and their combinations in addition to the integrated vector management (IVM) package. IVM being a community approach is still to go a long way to be mass popular. Adulticides, larvicides, residual sprays, mosquito coil, insecticide-impregnated curtain, aerosol, etc. still serve as the major weapons of mosquito control. Thus, mosquito control still mostly depends on chemical insecticides. Although the use of DDT is banned in Bangladesh, there are reports on its illegal use in different forms. Moreover, there is tons of leftover DDT in Bangladesh, which is likely to cause several diseases. As per one report, about 500 MTs of DDT stockpiles are lying in the Medical Sub-Depots at Chittagong for over a period of 26 years. DDT is a persistent organic pollutant pesticide, which can cause diseases like cancer, endocrine disorder, disruption of immune system, embryonic abnormality, reproductive disorder, etc. Other chemical insecticides, which are replacing DDT, are also not free of hazardous impacts. IVM thus appears to be a wise approach requiring concerted efforts for the management of mosquito to control malaria. Such an IVM comprises use of Bacillus thuringiensis Berliner var. israelensis, methoprene, biocontrol agents, cleaning of breeding sites, pyrethroid-impregnated curtain, etc. Therefore, a wise effort should be adopted to completely stop the use of DDT, eliminate its stockpiles wherever they are in Bangladesh and to popularise the IVM, not the chemicals-based alternatives throughout the country.     

Thermal venting to recover less-volatile hydrocarbons from the unsaturated zone, 1. Theory

Thermal venting is a remediation technique suitable to the liquid unsaturated zone to enhance recovery of less-volatile residual hydrocarbon contaminants. Thermal venting is different to traditional soil venting because heated air instead of air at ambient conditions is applied to the contaminated zone. The vapor pressure of a less-volatile contaminants is typically increased by temperature causing the gas-phase concentrations to increase by three- to five-fold over a temperature increase of 20–30°C. The work described in this first paper provides the theoretical framework of analysis related to thermal venting. The analysis included nonisothermal gas flow, thermal energy transport and multicomponent mass transport in a multiphase porous medium. The transient gas flow analysis included the effect of temperature on fluid properties and gas compressibility. The heat energy transport analysis was performed under the thermodynamic equilibrium condition with phase-summed effective thermal properties. Multi-component mass transport was performed under local equilibrium for partitioning between phases. Model verification was performed to the extend possible using analytical and available experimental data for different physical processes. The second paper of this two-part series will demonstrate the applicability of thermal venting technique through numerical simulations of hypothetical laboratory and field-scale scenarios.     

Role of Amino Acids on <Emphasis Type="Italic">In Situ</Emphasis> Photografting of Jute Yarn with 3-(Trimethoxysilyl) Propylmethacrylate

To improve the mechanical performance of natural lignocellulosic jute yarn, grafting with [3-(trimethoxysilyl) propylmethacrylate] (TMSPM) monomer has been performed on in situ UV radiation and optimized the monomer concentration (30%) and irradiation time (30 min). Effect of various amino acids (1%) as additives in TMSPM with photografted jute yarn at optimized system has been studied. The polymer loading (PL) and tensile properties like tensile strength (TS) and elongation at break (Eb) of treated samples were enhanced by incorporation of amino acids and the highest properties (TS = 300% and Eb = 386%) achieved by the sample treated with l-Arginine (Arg) with 32.5% PL value. Weak acid like 3% acetic acid and inorganic acid like 1% sulfuric acid were also incorporated in the optimized system of TMSPM grafting and compared their effect on the tensile properties with amino acid treated samples. Water absorption and weathering resistance of treated and untreated samples were also performed and treated sample showed lesser water uptake as well as less weight loss and mechanical properties as compared to untreated samples.     

Contrasting structure and composition of the understory in species-rich tropical rain forests

In large samples of trees > or = 1 cm dbh (more than 1 million trees and 3000 species), in six lowland tropical forests on three continents, we assigned species with >30 individuals to one of six classes of stature at maturity (SAM). We then compared the proportional representation of understory trees (1-2 cm dbh) among these classes. The understory of the three Asian sites was predominantly composed of the saplings of large-canopy trees whereas the African and American sites were more richly stocked with trees of the smaller SAM classes. Differences in class representation were related to taxonomic families that were present exclusively in one continent or another. Families found in the Asian plots but not in the American plot (e.g., Dipterocarpaceae, Fagaceae) were predominantly species of the largest SAM classes, whereas families exclusive to the American plots (e.g., Melastomataceae sensu stricto, Piperaceae, and Malvaceae [Bombacacoidea]) were predominantly species of small classes. The African plot was similar to Asia in the absence of those American families rich in understory species, while similar to America in lacking the Asian families rich in canopy species. The numerous understory species of Africa were chiefly derived from families shared with Asia and/or America. The ratio of saplings (1-2 cm dbh) to conspecific canopy trees (>40 cm dbh) was lower in American plots than in the Asian plots. Possible explanations for these differences include phenology, moisture and soil fertility regimes, phyletic constraints, and the role of early successional plants in forest development. These results demonstrate that tropical forests that appear similar in tree number, basal area, and the family taxonomy of canopy trees nonetheless differ in ecological structure in ways that may impact the ecology of pollinators, dispersers, and herbivores and might reflect fundamental differences in canopy tree regeneration.     

Graphical estimation of the dual-enzyme kinetic parameters for Cr(VI) reduction

Chromium(VI) (Cr(VI)) contamination of soil and groundwater is a major environmental concern. Bioreduction of Cr(VI) by Shewanella oneidensis MR-1 (MR-1) can be considered a feasible option to reduce the toxic and mobile Cr(VI) to the less toxic and less mobile chromium(III) (Cr(III)). The reaction rate expression for Cr(VI) reduction is nonlinear and the rate constants are evaluated by employing nonlinear optimization techniques. The outcome of the optimization techniques, in general, depends on the initial estimate of the kinetic parameters which is not always available. A graphical approach based on sound mathematical reasoning has been developed which is accurate, simpler to use, and can provide the best initial estimate for nonlinear optimization.     

Nanocarrier-mediated co-delivery systems for lung cancer therapy: recent developments and prospects

Environmental Chemistry Letters - Research has recently focused on combinational therapy using nanocarriers to overcome the obstacles associated with conventional therapy of lung cancer. The...     

Climate change and soil salinity: The case of coastal Bangladesh

This paper estimates location-specific soil salinity in coastal Bangladesh for 2050. The analysis was conducted in two stages: First, changes in soil salinity for the period 2001–2009 were assessed using information recorded at 41 soil monitoring stations by the Soil Research Development Institute. Using these data, a spatial econometric model was estimated linking soil salinity with the salinity of nearby rivers, land elevation, temperature, and rainfall. Second, future soil salinity for 69 coastal sub-districts was projected from climate-induced changes in river salinity and projections of rainfall and temperature based on time trends for 20 Bangladesh Meteorological Department weather stations in the coastal region. The findings indicate that climate change poses a major soil salinization risk in coastal Bangladesh. Across 41 monitoring stations, the annual median projected change in soil salinity is 39 % by 2050. Above the median, 25 % of all stations have projected changes of 51 % or higher.     

Managing mangroves in Bangladesh: A strategy analysis

Bangladesh, favoured by a tropical climate, houses the world’s largest stretch of mangroves forests (Sundarbans Reserved Forest) and plantations. Around half of the forests of the country occur in the coastal zone. People extract various goods and services from the mangroves. Nevertheless the mangrove forests are depleting. Although the extent of the Sundarbans forest has not changed much, its decline is of a qualitative nature. Mangrove plantations are increasing in area but they are losing growing stock. To arrest this, Bangladesh has adopted several strategies. The ‘Sustainable Ecosystem Management’ strategy has now been adopted instead of the ‘Sustained Yield Principle’. Biodiversity conservation and enhancement has been taken as a key management goal. A zoning system is being developed for both production and protection purposes. The government facilitates alternative income for the local people by generating activities for the communities which are dependent on the forest. Different non-governmental organizations collaborate with the government in reducing the local people’s dependence on the forest. Coastal plantations are erected to protect people from cyclones and to make the land more suitable for habitation. Through this greening of the coastal belt tree plantation is encouraged in coastal villages. Coastal embankments are being planted and leased to poor settlers in exchange for routine maintenance of the embankments. Plantations on newly accreted mud flats help in stabilizing the land, which can later on be settled by victims of erosion elsewhere. These adopted management measures do not only contribute to forestry resource management but also to the social, environmental and economic wellbeing of the coastal communities. These efforts are at present being integrated into an Integrated Coastal Zone Management (ICZM) project.     

Seasonal occurrence of the yellow stem borer Scirpophaga incertulas (Walker) on deepwater rice in Bangladesh and Thailand

Deepwater rice is grown in South and Southeast Asia on 11 million hectares flooded deeply during the monsoon. Surveys for the incidence of stem borers in deepwater rice in Bangladesh from 1977 to 1980, and in Thailand during 1981 and 1982, showed that borer incidence and species composition were remarkably similar. Scirpophaga incertulas (Walker) usually comprised more than 90% of the borer population and was almost exclusively present during the main flooding period. Chilo polychrysus (Meyr.) comprised 11% and Sesamia inferens (Walker) 6% of the population in the pre-flood and ripening stages.Low borer activity in the early part of the season was explained by a low nucleus population, the synchronous planting of deepwater rice, and severe moisture stress and high temperatures in the pre-flood period. In Bangladesh, a severe drought in 1979 limited Scirpophaga incertulas populations to unusually low levels until the flowering stage. In Thailand, drier conditions, the lack of an intervening rice crop in the dry season and a longer pre-flood period, appeared to severely restrict early season borer activity. The onset of flooding and stem elongation provided a more favourable environment for S. incertulas. Borer activity increased steadily during the first 3–4 months of flooding, to average 23% damaged stems (26 m^?2) and 13 borer immature stages/100 stems (13 m^?2) by the flowering stage. Borer activity continued at about the same level as the water receded, to reach maximum annual levels of 38–44% damaged stems (35 m^?2) at the late-ripening stage. At harvest, 60% of the fields were at outbreak level (>40% damaged stems). Such high levels of damage are explained by the long growth period of deepwater rice, favourable weather during the flooding period, and the optimum habitat of the elongated stem. S. incertulas populations then crashed to low levels; the larvae entering diapause in the field stubble. Although related to actual damage, the deadheart and whitehead symptoms grossly under-estimated the extent of stem damage.