Discussion of “Mahmodinia,S., & Javan,M. (2021). Vortical structures,entrainment and mixing process in the lateral discharge of the gravity current. Environmental Fluid Mechanics, 21(5), 1035–1067”

Environmental Fluid Mechanics - The authors of the discussed paper presented an interesting study of the lateral gravity currents for the different flow conditions. The authors showed the...     

Coping with the ‘Indian summer’: unique nesting cycle and nest architecture of the paper wasp,Polistes wattii

The Science of Nature - Leaf-cutting ants are highly successful herbivores in the Neotropics. They forage large amounts of fresh plant material to nourish a symbiotic fungus that sustains the...     

Characteristics of chlorofluorocarbons (CFCs) emitted from a municipal waste treatment facility

The emission concentrations of several chlorofluorocarbons (CFCs) were measured from a municipal waste treatment facility (located in Seoul, Republic of Korea) to investigate the emission characteristics of CFCs in the urban environment. To this end, a total of five CFCs (CFC-10, CFC-11, CFC-20, CFC-30, and CFC-113) were analyzed by the thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method. The results of this study indicate that the formation of CFC-11 (8.21 ± 1.68 ppb in spring) and CFC-20 (3.92 ± 3.93 ppb in spring) proceeded very actively within the facility. Moreover, CFC-113 was also found in relatively high concentrations (3.34 ± 1.31 ppb in spring) in the treatment facility. Unlike other CFCs, CFC-10 was observed mainly at ambient (and reference) locations and one point inside the treatment facility. In conclusion, emissions of some important CFCs are a prominent process, as they were measured either frequently or abundantly both in winter and spring. It is further indicated that certain CFCs (like CFC-11 and CFC-30) are subject to highly significant seasonal variations.     

Volatile Organic Compounds in Ambient Air at Four Residential Locations in Seoul, Korea

To investigate the environmental behavior of volatile organic compounds (VOCs) in urban areas, their concentrations were measured at four urban monitoring sites (namely, N, S, E, and W) in Seoul, Korea (February to December 2009). A total of 27 compounds were quantified that consist of four chemical groups: aromatic (AR), halogenated aromatic, halogenated paraffin, and halogenated olefin. Results were evaluated by focusing on these four functional groups just mentioned and their summation term as total VOC (TVOC) along with several individual species (mainly AR species, that is, benzene, toluene, ethylbenzene, and xylene). The highest concentration of chemical groups was found from AR (71.1±42.1?ppbC), while that for individual species confirmed the dominance of toluene (7.48±3.88?ppb). The analysis of spatial distribution indicated that high TVOC levels were recorded at sites N and W, while it was not so significant such as S and E in terms of TVOC budget. Seasonal variation of these VOCs was characterized by the peak values in December to reflect the combined effects of pronounced source activities and meteorological conditions. Analysis of spatial variations in VOC levels between the four urban sites indicated that their distributions are tightly affected by local source processes in each area.     

The recent occurrence of exotic freshwater fishes in the tributaries of river Ganga basin: abundance, distribution, risk, and conservation issues

We record here the recent occurrence, abundance and distribution of six exotic fish species, viz. Oreochromis mossambicus, Cyprinus carpio, Hypopthalmicthys molitrix, Ctenopharyngodon idellus, Clarias gariepinus, and Pterygoplichthys disjunctivus (a new exotic in India) distributed through the four important tributaries of river Ganga basin in India. From the total catch, the abundance index of all exotic species in different rivers ranged from 1.1 to 14.5?% with highest value in River Gomti. The relative abundance of the exotic species in all the four tributaries demonstrated that a single species C. carpio contributed a considerable abundance (43.3?C83?%) than that of the remaining exotic fishes. The Common Carp, C. carpio, was ubiquitous in all the four tributaries of Ganges basin studied and had the highest local distribution (52.63?%). Smaller size groups of endangered (Chagunius chagunio, Chitala chitala, and Tor tor) and migratory species (Bagarius bagarius, Ompok pabda, Wallago attu, and Sperata aor) in the four tributaries were recorded, and the increasing appearance of Common Carp and other exotic fishes is signaling biological invasion. Possible threats to the indigenous fish fauna, as a result of the invasion and proliferation of these exotics, are discussed.     

Synthesis and pesticidal activity of new N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines

A series of novel N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines were synthesized as potential new agents to control pests. Their structures were confirmed on the basis of IR, NMR and elemental analyses. Six new N-alkyl-N-[1-(2-hydroxyphenyl) ethyl]amines were prepared by reduction of corresponding Schiff bases using sodium borohydride in 80–87 % yields. These compounds were tested for their antifungal activity against two pathogenic fungi viz., Rhizoctonia bataticola ITCC 0482 and Sclerotium rolfsii ITCC 5226 and for insecticidal activity against insects of stored grain pest Callosobruchus analis. Fungicidal bioassay revealed that compound N-Decyl-N-[1-(2-hydroxyphenyl)ethyl]amine, was highly effective against R. bataticola (ED₅₀ 6.86 mg L^?1) which was comparable with that of commercial fungicide hexaconazole (ED₅₀ 6.35 mg L^?1). Also compounds N-Heptyl-N-[1-(2-hydroxyphenyl)ethyl]amine, N-Octyl-N-[1-(2-hydroxyphenyl)ethyl]amine and N-Nonyl-N-[1-(2-hydroxyphenyl)ethyl]amine displayed promising fungitoxicity against same pathogen. However, compound N-Heptyl-N-[1-(2-hydroxyphenyl)ethyl]amine was also found to be effective against S. rolfsii (ED₅₀ 4.92 mg L^?1 as against 1.27 mg L^?1 for hexaconazole). Compound N-Hexyl-N-[1-(2-hydroxyphenyl)ethyl]amine was most effective as insecticide followed by compound N-Octyl-N-[1-(2-hydroxyphenyl)ethyl]amine. LC₅₀ values for these compounds were 155.0 and 275.0 mg L^?1 respectively as against 36.70 mg L^?1 for commercial insecticide dichlorovos. The results obtained from bioassays indicate that this class of compounds can be utilized for the design of new substances endowed with pesticidal activities.     

Predicting Streambed Sediment and Water Column Escherichia coli Levels at Watershed Scale

A sub‐model for the Soil and Water Assessment Tool (SWAT) is developed to predict Escherichia coli levels in the streambed sediment as well as in the water column. New formulations to estimate the levels of E. coli in streambed sediment and the water column are derived. These equations include calculations of E. coli resuspension from the streambed sediment to the water column, E. coli deposition from the water column to the streambed sediment, E. coli growth in the streambed sediment and the water column, and instream E. coli routing. These formulations were programmed in FORTRAN and integrated into SWAT. The modified SWAT model was applied to Squaw Creek Watershed, Iowa, to predict E. coli levels in the stream. Escherichia coli concentrations in the streambed sediment and the water column were monitored extensively in this watershed, and observations were used to verify the model predictions. The model proposed here can predict E. coli concentrations in streambed sediment as well as in the water column. Approximately 58% of the predictions of E. coli levels in the bed sediment were within 1 order of magnitude from the observed value, and in the water column 83% of the predictions of E. coli levels were within 1 order of magnitude. Results suggest that the proposed model will help predictions of instream bacterial contamination.     

Urgency for sustainable development in coastal urban areas with reference to weather pattern,land use,and water quality

Water pollution is one of the most critical problems affecting mankind. Weather pattern and land use of catchment area have significant role in quality of water bodies. Due to climate change, there is frequent variation in weather pattern all over the world. There is also rapid change in land use due to increase in population and urbanization. The study was carried out to analyze the effect of change in weather pattern during the monsoon periods of 2008 and 2012 on water quality of a tropical coastal lake system. The nature and extent of variation in different water quality parameters namely electrical conductivity (EC), magnesium (Mg), sodium (Na), chloride (Cl), sulphate (SO₄), turbidity, Secchi disk depth, biochemical oxygen demand (BOD), phosphate (PO₄), calcium (Ca), and water temperature as well as the effect of various land use activities in the lake basin on water quality have also been studied. There is significant reduction in precipitation, EC, Mg, Na, Cl, SO₄, turbidity, and Secchi disk depths whereas a significant rise in the BOD, PO₄, Ca, and water temperature were observed in 2012. This significant reduction in electrical conductivity during 2012 revealed that because of less precipitation, the lake was separated from the sea by the sandbar during most of the monsoon period and thereby interrupted the natural flushing process. This caused the accumulation of organic matter including phosphate and thereby resulting reduction in clarity and chlorophyll-a (algae) in the lake. The unsustainable development activities of Thiruvanathapuram city are mainly responsible for the degradation of water bodies. The lack of maintenance and augmentation activities namely replacement of old pipes and periodical cleaning of pipe lines of the old sewer system in the city results in the bypass of sewage into water bodies. Because of the existence of the old sewerage system, no effort has been taken by the individual establishment/house of the city to provide their own treatment system for sewage and sullage and the untreated wastes are discharged into these old sewer pipes and ultimately the wastes reach the water bodies. In this context, decentralized treatment of sewage, sullage, and garbage by individual houses/establishments/hotels/hospitals is a better option for the developing countries. With the rapid developmental activities, and due to the variation of precipitation due to climate change, it is highly essential to provide proper waste treatment/augmentation facilities in urban lake system because a slight variation in the weather pattern can result in serious implications in the already polluted water bodies.     

Limnochemistry and nutrient dynamics in Upper Lake, Bhopal, India

In limnetic ecosystem, water quality depends upon physical, chemical, and biological factors. Effects of temperature, light scattering, and absorption by suspended and dissolved matter, transport, and mixing of nutrients within the lake are the significant factors as far as water quality is concerned. Nutrient loading into the lake and internal cycling of nutrients is always a matter of concern and critical to number of processes. During the winter season, heat and momentum transfer at the lake surface and the temperature-density relation of water destabilize the water column and drive vertical mixing and transport processes. The deepening of the surface layer produces nutrient transfer from the hypolimnion into the euphotic zone of epilimnion. It may also resuspend sediments that would have settled under stratified conditions, or redistribute particles that may still be in suspension. Thus, there exists a complex connection between the hydrodynamics and water quality issues. Present study is an effort to understand how seasonal changes in the limnetic ecosystem regulate the limnochemistry and movement of nutrient. The study revealed that significant variations of nutrients and organic load were observed between epilimnion and hypolimnion during summer season, and the lake was found in hyper-eutrophic condition throughout the study period.