Hydrochemistry and dissolved solute load of meltwater in a catchment of a cold-arid trans-Himalayan region of Ladakh over an entire melting period

The hydrochemical study of meltwater draining from a catchment dominated by snowmelt in a cold-arid trans-Himalayan region of Ladakh, India, was carried out for an entire melting season (May–September) during the year of 2010. Cation concentration in the meltwater shows a consistent trend of Ca > >Mg > Na > K for this period. Carbonate weathering has been identified as the dominant process controlling the dissolved ion chemistry of meltwater in the study area. There are indications that atmospheric aerosols contain alkaline dust, sea salt and anthropogenic aerosols like NO3 and SO4 that might have also added some solute to the system. Meltwater chemistry has been showing an intra-annual variation with highest concentration for most of the dissolved solutes during the late melt period, pointing towards the contribution of ground ice melt to the catchment runoff. The lowest concentration during the peak melt period is due to higher contribution from snow melt which has less residence time to interact with rock. Cationic denudation rate for this catchment has been estimated as 778 meq m−2 a−1, while the average total dissolved solids flux for early, peak and late melt period is 0.64 t day−1, 3.02 t day−1, 1.31 t day−1, respectively.

The impact of atmospheric wet deposition on roof runoff quality in an urbanized area

Understanding the sources of chemical components in roof runoff can help to prevent water quality problems in rooftop rainwater harvesting. To identify the contribution of wet deposition to the mass of components in roof runoff, the samples from air, rainwater, dust buildup and roof runoff were collected from an urban site in Shenzhen of China in 2011–2012. The results indicate that: (1) wet deposition has a dominant contribution to the mass of total organic carbon (TOC), NH4+, NO3–, Cl– and organic acids in the roof runoff, while the mass of NH4+, acetic acid and formic acid in the roof runoff may be greatly reduced by the neutralization between the components with alkaline dust buildup on the rooftop; and (2) wet deposition partially contributes to the mass of Na+, K+, Mg2+, Ca2+, F– and SO42– in the roof runoff, while other factors like dust buildup on the rooftop and chemical reactions also have a non-negligible impact. Furthermore, TOC, NH4+, NO3– and organic acids in the wet deposition are mainly influenced by the atmospheric pollution due to fast increase in fossil fuel consumption (e.g. vehicle emissions). Therefore, the effects of wet deposition should be carefully considered for rooftop rainwater harvesting in urbanized areas.