River Geochemistry

Chemistry of Rivers of Kerala

There has been a spate of recent studies on the geochemistry of the rivers of Kerala. This is especially timely given the state of affairs as afr as the environment is concerned in Kerala. A recent paper in the Taylor and Francis journal Chemistry and Ecology, Volume 23, Issue 1 February 2007 , pages 13 - 27 is on

Hydrochemistry and dissolved nutrient flux of two small catchment rivers, south-western India. The rivers are Chalakudy and Periyar rivers.

by K.Maya; K. N. Babu; D. Padmalal of

Centre for Earth Science Studies, Thiruvananthapuram, Kerala, India
	b and Department of Marine Geology and Geophysics, Cochin University of Science and Technology, Kochi, Kerala, India

and heavily dammed rivers - Periyar and Chalakudy - of Kerala on the south-west coast of India. The lower reaches of these rivers are affected by sea-water ingression from the Arabian Sea during the non-monsoon season. Human interference through agriculture, urbanization, and industrialization in the lower and middle stretches of the river basins induces marked concentration variations in the hydro-chemical parameters. Except for N & P, all other chemical constituents exhibit high values during the non-monsoon season. Industrial contaminants in specific locations of the Periyar river reduce the pH to lower levels. Nutrients in the two rivers reveal marked seasonal and regional concentration variations. During the monsoon season, dissolved inorganic nitrogen (DIN) predominates over dissolved organic nitrogen (DON), but the reverse trend is observed during the non-monsoon season. The Periyar river shows higher average concentrations of DIN (monsoon 801 g l-1 and non-monsoon 292 g l-1) than Chalakudy river (monsoon 478 g l-1 and non-monsoon 130 g l-1). Dissolved inorganic phosphorus (DIP) has lower average values in the monsoon season (Periyar river, 38 g l-1; Chalakudy river, 42 g l-1) than dissolved organic phosphorus (DOP) values (Periyar river, 107 g l-1; Chalakudy, 62 g l-1). The rivers show a marked difference in nutrient flux due to its difference in water discharge/basin characteristics and point/non-point sources of contaminants. The flux rates of DIN, DIP, and DOP during the monsoon are higher than during the non-monsoon season, while those of dissolved silicon (DSi), dissolved Fe (DFe), and DON are lower. On average, the Periyar river discharges 4953 t y-1 of DIN and 1626 t y-1 of DON to the coastal waters, and the corres-ponding values of the Chalakudy river are 772 t y-1 and 596 t y-1. The Periyar and Chalakudy rivers discharge 245 t y-1 and 70.8 t y-1 of DIP, respectively. The total flux of DOP is considerably higher (Periyar river 703 t y-1 and Chalakudy river 101 t y-1). The discharge of DSi into the Periyar river (40 193 t y-1) is nearly five times higher than that in the Chalakudy river (8275 t y-1). The discharges of DFe through the Periyar and Chalakudy rivers are 257 t y-1 and 36.7 t y-1, respectively. To sum up, this study addresses the water quality and nutrient flux of two tropical rivers and discusses the impact of urbanization and industrialization on river-water quality.

Glacier melting: a new trigger

Veerabhadran Ramanathan [vramanathan@ucsd.edu ]

and Muvva V. Ramana




of the Center for Clouds, Chemistry and Climate, Scripps Institution of Oceanography, UCSD , La Jolla, California 92037, USA along with their colleagues in the NASA Langley Research Center, Hampton, Virginia 23681-0001, USA has proposed that warming trends in Asia have been amplified by brown cloud solar absorption.

Atmospheric brown clouds are mostly the result of biomass burning and fossil fuel consumption. They consist of a mixture of light-absorbing and light-scattering aerosols and therefore contribute to atmospheric solar heating and surface cooling.

The authors used three lightweight unmanned aerial vehicles that were vertically stacked between 0.5 and 3 km over the polluted Indian Ocean. Over a three-week period during March 2006, the scientists took measurements of soot, sulphate and nitrate levels and solar radiation over the Maldive Islands in the Indian Ocean. These unmanned aerial vehicles deployed miniaturized instruments measuring aerosol concentrations, soot amount and solar fluxes.

During 18 flight missions the three unmanned aerial vehicles were flown with a horizontal separation of tens of metres or less and a temporal separation of less than ten seconds, which made it possible to measure the atmospheric solar heating rates directly.

The authors found that atmospheric brown clouds enhanced lower atmospheric solar heating by about 50 per cent. Our general circulation model simulations, which take into account the recently observed widespread occurrence of vertically extended atmospheric brown clouds over the Indian Ocean and Asia, suggest that atmospheric brown clouds contribute as much as the recent increase in anthropogenic greenhouse gases to regional lower atmospheric warming trends.

The combined warming trend of 0.25 K per decade may be sufficient to account for the observed retreat of the Himalayan glaciers