Ionic composition of waterbodies in central and southern Nepal sampled in spring 1985 differed from that normally found in freshwater. Distinguishing characteristics were: 1) predominance of bicarbonate among the anions — accounting for > 90% of the negative equivalents in two-thirds of the waterbodies, 2) the near absence of sulfates — accounting for < 1 % of the anions in half the samples so that chloride exceeded sulfate (as meq/L) in three-fourths of the waters tested and 3) calcium was the dominant cation, although in certain waters the relative proportion of either magnesium or the monovalent cations was much higher than the world average. Regional patterns in water chemistry were apparent and are largely explained by differences in local geology, inputs from artesian wells or extensive use by humans. Most ionic salinity values were <400 mg/L. Using conventional criteria to assess trophic state, most water-bodies were eutrophic or hypereutrophic when judged by total phosphorus and chlorophyll content but as a whole the lakes sampled were low in nitrogen. Nitrogen: phosphorus ratios (generally < 10) and a significant empirical relation for chlorophyll-nitrogen provide evidence that nitrogen limited algal biomass. Secchi transparency values indicate light regimes were affected by nonalgal materials.

Limnological reconnaissance of waterbodies in central and southern Nepal

Between April 1993 and November 1994, conductivity, cations, anions and suspended solids were measured at multiple sites in Taechung Reservoir, Korea The major mechanism regulating ionic composition was dilution by monsoon rain and a resulting interflow current; these forces caused marked spatial and temporal heterogeneity Ionic dilution was most pronounced in the headwaters during an intense monsoon in 1993 and was accompanied by an increase in the proportion of Na+and Cl−, presumably from rainwater A decrease of >25% in conductivity and cations occurred during summer 1993 at the plunge-point due to a temperature difference between the lake water and an interflow In contrast, the 1994 monsoon was weak, ionic dilution was not apparent, and spatial-temporal variation was modest Overall reservoir salinity was a direct function of water residence time which is regulated by monsoon intensity Differences in hydrology between years also influenced seston composition; inorganic suspended solids dominated total suspended solids in 1993, but in 1994 the organic fraction was the major component

https://link.springer.com/content/pdf/10.1023/A:1026578117878.pdf

Temporal and spatial patterns in salinity and suspended solids in a reservoir influenced by the Asian monsoon.

Pre- and postmonsoon limnological characteristics of lakes in the Pokhara and Kathmandu Valleys, Nepal: With 3 figures and 3 tables in the text

Precipitation samples were collected as wet-fall only and primarily on event basis in Delhi during the monsoon period of 1995. Concentrations of major anions (SO4(2-), NO3- and Cl-) and cations (Ca2+, Mg2+, Na+ and K+) were determined. The pH of the rain water was found to be more than 5.6, showing alkalinity during the early phase of monsoon, but during the late phase of monsoon pH tendency was towards acidity due to lack of proper neutralization of acidic ions. Neutralization is not only due to the local process but also due to the pre-monsoon 'Andhi' which brings Suspended Particulate Matter (SPM) containing Ca2+, Mg2+, Na+ and K+ as well as the local emission of NH3. In the late monsoon the concentration of cations gets reduced because of heavy rainfall and relatively unfavourable condition for their transport from the adjoining areas, whereas the anion concentrations remain unchanged owing to their continuous emission.

Occurrence of acid rain over Delhi.

Airborne submicron particles (PM1) were collected using PM1 sampler during the fog-dominated days (December 2013–January 2014). PM1 values varied between 58.12 μg/m3 and 198.75 μg/m3, and average mass concentration was 162.33 ± 38.25 μg/m3 while total average concentration of particle-associated polycyclic aromatic hydrocarbon (PAHs) determined was 616.31 ± 30.31 ng/m3. This is a signal for an alarming high pollution level at this site situated in the Indo-Gangetic Plain (IGP). PAHs were extracted from filters using toluene and acetonitrile. Quantitative measurements of polycyclic aromatic hydrocarbons (PAHs) were carried out using the high performance liquid chromatography (HPLC) technique. The extracts were analyzed for 16 target polycyclic aromatic hydrocarbons (PAHs) including carcinogenic compound benzo(a)pyrene (19.86 ± 38.98 ng/m3). Fluoranthene, benzo(a)anthracene, anthracene, and fluorene were the predominant compounds found in the samples collected during foggy days. Based on number of rings, four-ring PAH compounds had maximum contribution (43 %) in this fog time collected submicron particles followed by three-ring (21 %), five-ring (20 %), six-ring (13 %), and two-ring (3 %), respectively. In winter and foggy days, wood and coal combustion and biomass burning also significantly contribute to the PAH levels. However, diagnostic ratio suggests diesel emissions as the prime source of PAHs at this sampling site.

Speciation of atmospheric polycyclic aromatic hydrocarbons (PAHs) present during fog time collected submicron particles.

A comparative study of the periodic and aperiodic variations of some physico‐chemical parameters of the open and closed parts of the Loktak Lake, Manipur, India, was carried out for a period of three years from 1976–78 to investigate the effects, if any, of human activities on these variations. The closed part of the lake, used for controlled fishing was well protected, whereas the open part was subjected to considerable human activities. The variation in the physico chemical parameters in the open lake were different from those of the closed lake in that (a) there was distinct seasonal variation in DO which was not evident in the closed lake and (b) there was direct relationship between diurnal variation of CO2 and pH instead of an indirect relationship in the closed lake. The variation in pH, electrical conductivity, bicarbonate, free carbon dioxide and chloride between 1976–78 had a similar pattern in the two parts of the lake.

Comparison of seasonal and diurnal patterns of some physico‐chemical parameters of the open and closed parts of Loktak Lake, Manipur, India

This investigation is concerned with the determination of total polynuclear aromatic hydrocarbons (PAH) in the ambient air of Delhi. Air sampling was done for a period of six months at five sampling stations. PAH was determined by the quinine sulphate method. A city average profile was obtained; seasonal variation of PAH concentration, as well as its correlation with total suspended particulates (TSP) and wind‐velocity, were ascertained.

Polynuclear aromatic hydrocarbons in the ambient air of Delhi

Four‐hourly data were collected for 24 hour periods in the months of December (1977), April (1978), July (1978) and December (1978) in respect of some physicochemical characteristics and plankton population in a protected part of the Loktak Lake (Manipur) India. Highly significant correlations, positive as well as negative, were observed between the diurnal and seasonal variations of physicochemical characteristics with those of total phyto or zooplankton of certain species.

D. K. Banerjee

Papers

Comparison of seasonal and diurnal patterns of some physico‐chemical parameters of the open and closed parts of Loktak Lake, Manipur, India

Polynuclear aromatic hydrocarbons in the ambient air of Delhi

Association between some planktonic species and physicochemical characteristics of the water of Loktak lake, Manipur, India