Pradeep M. Dangol

Assessment of biogenic secondary organic aerosol in the Himalayas

Environmental context Secondary organic aerosols derived from biogenic gases are ubiquitous in the atmosphere. We found that biogenic secondary organic aerosol in Nepal accounted for 6 to 23 % of organic carbon. Primary and secondary biogenic sources combined accounted for approximately half of the observed organic aerosol, suggesting that additional aerosol sources or precursors are significant in this region of the Himalayas. Abstract Biogenic contributions to secondary organic aerosol (SOA) in the South-East Asian regional haze were assessed by measurement of isoprene, monoterpene and sesquiterpene photooxidation products in fine particles (PM2.5) at a mid-latitude site in the Himalayas. Organic species were measured in solvent extracts of filter samples using gas chromatography–mass spectrometry (GCMS) and chemical derivatisation; this analysis was used to quantify molecular markers for primary aerosol sources – including motor vehicles, biomass burning and detritus – and SOA tracers. Authentic standards of most SOA products were not commercially available at the time of this study, so surrogate standards were used for semiquantitation. Using an empirical approach to uncertainty estimation based on homologous series of atmospherically relevant model compounds, analytical uncertainties ranged from 32 % for SOA tracers with structurally similar surrogates to more than 100 % for tracers with a poorly matched surrogate. Biogenic SOA contributions to PM2.5 organic carbon content in the 2005 monsoon and post-monsoon season ranged from 2–19 % for isoprene, 1–5 % for monoterpenes and 1–4 % for sesquiterpenes. High concentrations of isoprene derivatives in aerosol, particularly in the late summer months, point to biogenic SOA as a significant source of organic carbon in the Himalayan region.

Rainfall amount and intensity in a rural catchment of the middle mountains, Nepal

Abstract Though rainfall intensity is the most important parameter for the investigation and prediction of flood generation and soil erosion, only limited information on this characteristic is available in the Nepal Himalaya. The People and Resources Dynamics of Mountain Watersheds in the Hindu Kush-Himalaya Project (PARDYP) is maintaining several high-density raingauge networks in mesoscale catchments of the Hindu Kush-Himalayan middle mountains. The first results from the network in the Jhikhu Khola catchment (JKC), where the longest data series is available, are presented here. In general, the catchment experiences monsoon type rainfall with about 78% of the annual rainfall occurring during the monsoon season. During the remainder of the year, rainfall is variable and erratic. The highest rainfall intensity occurs in the pre-monsoon season followed by the monsoon season and the same pattern is observed in the case of the erosivity. About 90% of the total annual rainfall has the potential to contribute to runoff generation and about 87% contributes towards sediment mobilization. Spatially, there is no distinct difference between the rainfall event parameters visible during the events, which cause the largest flood events at the outlet of the catchment. Rainfall in the lower lying JKC is generally lower. For extrapolation of the intensity information the intensity—duration—frequency (IDF) relationships were calculated. It is showed that the IDFs used to date heavily underestimate the short-duration intensities and their recurrence.

Assessing Renewable Water Resources and Water Use in Angola

“Nature” is one of the culturally most loaded concepts. It is one of the central concepts for human understanding and structuring of the surroundings (Glacken, 1967). The concept of nature is deeply embedded in our understanding of the world, so deep that we seldom reflect its central role in our thinking. With impulses from symbol theory (Elias, 1991), environmental history (Berntsen, 1994; Nash, 1982) and social sciences (Berger and Luckmann, 1987), this article examines nature, not as a physical reality, but as a symbol of ideas, norms and values in society. “Nature” is understood and interpreted in a historical, social and cultural context.

Water Management Issues in Middle Mountain Catchments of the Nepal Himalayas: The Downstream Perspective

Middle mountain catchments in the Hindu Kush-Himalayan region are the heavily populated and mainly rainfed headwaters of many smaller, but not less important rivers, and the tributaries of the larger North-South rivers draining the mountain system. The catchments are in a fragile and vulnerable region from the perspective of water scarcity, flooding and soil erosion. It is these catchments which caused the theory of the ”Himalayan Environmental Degradation” (Eckholm, 1976).

Water accounting in two rural meso‐scale catchments of the middle mountains in Nepal

Abstract: This study assesses water needs and uses in two middle mountain catchments in Nepal, the Jhikhu Khola and the Yarsha Khola. It concludes that the amount of annual water available is adequate for the current water demands, and that rainwater stored to use it during the dry season can be useful to increase cropping intensity and change cropping patterns, if efficient irrigation methods are applied.