Hydrogeochemistry of Two Major Mid-hill Lentic Water Bodies for Irrigation of the Central Himalaya, Nepal

The concentration and composition of different salts in natural water bodies determine the water quality for various purposes. This study assesses the water quality of two mid-mountain lentic water bodies, Lake Phewa and Kulekhani Reservoir. For this purpose, selected physico-chemical parameters along with major ions such as HCO3-, SO42-, PO43-, NO3-, Cl-, Ca2+, Mg2+, Na+, K+, and NH4+ were analyzed. Major ions were analyzed using ion chromatography, anions by DX-600 and cations by Dionex ISC-2500 ion chromatographs. The sources of major ions were determined by using the Gibbs diagram, Piper plot, and Scatter plots. Dissolved oxygen, ammonia and phosphate showed seasonal variations in both lakes. The concentrations of cations are in the order of Ca2+ > Na+ > Mg2+ > K+ in both water bodies. However the trend of anions had small variations for Cl- and SO42- in Lake Phewa (HCO3- > Cl- > SO42- > NO3-) and Kulekhani Reservoir (HCO3- > SO42- > Cl- > NO3-). The Piper plot and equiline plots indicated that the water chemistry is dominantly controlled by the dissolution of carbonate minerals and to a limited extent by weathering of silicate minerals. This is further supported by the Gibbs plot showing bedrock geology as the main source of major ions. The overall study indicates that the hydrogeochemistry of these water bodies is controlled by local geology and is suitable for irrigation purposes

Variations of the Physicochemical Parameters and Metal Levels and Their Risk Assessment in Urbanized Bagmati River, Kathmandu, Nepal

During post-monsoon 2013, surface water samples were collected form 34 sites from the Bagmati River and its tributaries within the Kathmandu Valley to assess the river water quality. The physical parameters were measured on site and major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, SO42-, and NO3-) and 17 elements in water were analyzed in the laboratory. Conductivity ranged from 21.92 to 846 μS/cm, while turbidity ranged from 2.52 to 223 NTU and dissolved oxygen (DO) ranged from 0.04 to 8.98 mg/L. The ionic and elemental concentrations were higher in the lower section where the population density is high compared to the headwaters. The large input of wastewater and organic load created anoxic condition by consuming dissolved oxygen along the lower belt of the river. The concentration of the elements was found to be in the order of Mn > Zn > Ti > Rb > Cr > Cu > Sc > Ni > V > Li > Co > Mo > Cd > Y > Ga > Be > Nb. The concentration of Mn, Cd, Cr, Co, and Zn was particularly higher in urban and semiurban sections. Enrichment factor (EF) calculations for Cd, Co, and Zn showed their highly enriched values indicating that these elements originated from anthropogenic sources. Preliminary risk assessments were determined by the hazard quotient (HQ) calculations in order to evaluate the health risk of the metals. The HQingestion values of elements were found to be in the order Sb > Mn > Cr > V > Co > Cd > Cu > Zn > Ni > Li > Mo with all averaged HQ values less than 1, indicating no or limited health risk of metals from the river to the local residence. However the values of Sb in some parts of the Bagmati were close to unity indicating its possible threat. Anthropogenic activities like industrial activities, municipal waste water, and road construction besides the river appear to control the chemical constituent of the river water. Overall the river was highly polluted with elevated concentrations of major ions and elements and there is a need for restoration projects

Changing Trends in Cultivation Practices and Adoption of Climate Adaptive Farming in Eastern Nepal

Climate change impacts are likely to affect the agricultural production leading to further food insecurity. In this context, the trend of cereal production with climate variables was studied in order to understand the linkages between climate change and crop productivity. The study was conducted in three districts of Sagarmatha zone, namely Solukhumbu (mountain region), Okhaldhunga (hill region) and Saptari (Terai region) representing three ecological zones in Nepal. A household survey (295 households), focus group discussions and key informant interviews were used to collect data on the history of the cultivation systems, varieties of crop grown, trends on crop yield, and adaptation to climate change. Results showed farmers’ introduction of high yielding varieties of crops and vegetables due to economic benefit, while traditional varieties are no longer cultivated. The infestation of pest attack is increasingly seen since two decades, while few pests were reported to be disappeared. Although majority of farmers in Saptari and Okhaldhunga districts used pesticides as per the prescribed doses, pesticide use is still random in Solukhumbu district. The multiple comparisons of means showed that there is a significant difference in the average production of rice and maize since 30 years until recently (p<0.05) in these three districts. The average production of rice, maize and wheat increased with decreasing average annual temperature and rainfall in Saptari district since 30 years. In contrast, in Okhaldhunga and Solukhumbu districts, the average production of three cereal crops increased with increasing average annual temperature and rainfall. With the late arrival of the monsoon, farmers have adopted coping strategies particularly for rice cultivation through occasional shift in crop planting dates and selection of shorter duration crop varieties that can be harvested earl

Assessment of physico-chemical parameters of rainbow trout farms for the evaluation of potential threat to natural streams in Nepal

 Three trout farms from Nepal were studied to investigate the changes in physico-chemical parameters and their potential threat to natural water bodies receiving the effluents. Reference and impact sites were determined in each farm so as to find out the level of impacts due to farming activities. Some of the parameters such as dissolved oxygen, turbidity, conductivity, and total dissolve solids were significantly changed in the impacted zones compared to reference sites. Similarly, concentrations of some major ions such as calcium and sodium were increased in the impacted zones. On the other hand, some of the parameters such as pH and potassium did not change in the impacted zone although their concentrations were different among farms studied. Nevertheless, the overall changes in the physico-chemical parameters did not pose health risk to the aquatic ecosystems receiving effluents from these fish farms as the concentrations were below the prescribed levels by Environmental Protection Agency (EPA) as well as Nepal Environment Statistics. This is an indication that, although fish farming activities are degrading water qualities, there is no threat to the water quality receiving the effluents yet probably due to small scale farming. The increase in number of fish farms in the same area, however might pose risk to the ecological health in the region which warrants regular monitoring.  INTERNATIONAL JOURNAL OF ENVIRONMENTVolume-6, Issue-2, Mar-May 2017, Page: 43-55</p

Health risk assessment of atmospheric polycyclic aromatic hydrocarbons over the Central Himalayas

<p>Carcinogenic risk assessments of polycyclic aromatic hydrocarbons (PAHs) in four sites from the Central Himalayas (Bode, Lumbini, Pokhara, and Dhunche) were performed. Lifetime Average Daily Dose (LADD), Lifetime lung cancer risk (LLCR) and Incremental lifetime cancer risk (ILCR) were calculated in order to evaluate the cancer risk. PAHs levels were converted to BaP equivalent concentrations (B[a]Peq), and models of health risk assessment were applied. B[a]Peq concentrations exceeded the standard limited value (1 ng/m³) in all the four sites. The human health risk assessment (HHRA) demonstrated high carcinogenic risk on residents of Bode and Lumbini. Further, LLCR in all sites were over the acceptable range (1.15E-03, 7.90E-04, 1.40E-04 and 9.96E-05, respectively); however, ILCR ranking exhibited acceptable range in Lumbini, Pokhara, and Dhunche (7.10E-06, 1.26E-06, and 8.95E-07). The risk variation among the sites is due to the difference in pollution status. The study shows health risk due to atmospheric PAHs via inhalation prevails all the seasons throughout, differing only seasonally; nevertheless, the concentration and carcinogenic risk decreased remarkably from south-north transect of the central Himalaya. Keeping some uncertainties aside, this study provides noble insights and helps to formulate new advance assessment on the carcinogenic risk of atmospheric PAHs over the Central Himalayas.</p

Mercury Concentrations in Commercial Fish Species of Lake Phewa, Nepal

Mercury (Hg) concentrations in four commercial fish species (Tilapia Oreochromis niloticus, Spiny Eel Mastacembelus armatus, African catfish Clarias gariepinus, and Sahar Tor putitora), were investigated in Lake Phewa, Nepal. Mean values of total mercury (THg mg kg(-1), ww) in these fishes were 0.02, 0.07, 0.05, and 0.12 respectively. Methylmercury contributed 82 % of THg. The lowest value was detected in O. niloticus, an exclusive plant feeder. The biomagnification rate of Hg through the fish community was 0.041 per delta N-15 (aEuro degrees). The present investigation produced an important baseline data of Hg pollution in the fish community in this region

Concentration and risk assessments of mercury along the elevation gradient in soils of Langtang Himalayas, Nepal

<p>The fragile Himalayan region could be regarded as the sink for various pollutants transported from urbanized and polluted areas of South Asia. Therefore, in order to understand the concentrations, spatial distribution, pollution, and risk assessments of toxic heavy metal, mercury (Hg), surface soil samples were taken from the central Himalayas in the Langtang region. The average THg concentration in the Langtang Himalayas was 35.75 ± 24.41(ngg⁻¹), which is comparable to the Tibetan top soil values and slightly lower than world average soil values. In addition, an inverse relationship of THg with elevation were observed (i.e. decrease in concentration with increase in elevation) in the Langtang Himalayan soils. Meanwhile, THg concentrations and TOC% were significantly positively correlated at both the depths (0–10 and 10–20 cm), inferring the sorption capacity of organic carbon for Hg. The results of the geo-accumulation index (<i>I</i>_geo), enrichment factor (EF), and pollution index (PI) indicated limited or no pollution by Hg in the Himalayan soils. Further, surface soils had a low potential ecological risk in the region. Therefore, the Hg value from this study could be used for the further evaluation and calculation of I_geo, EF, and PI for water, soil, and aerosol in the Himalayan region as background reference value. However, Hg pollution from long-range transport and atmospheric deposition (wet/dry) in future could not be ignored in the Himalayan region.</p