Rain/river/ surface

O Water covers about 71 percent of the surface of the earth. Most of it is in the oceans and ice at the North and South Poles, but water is also in clouds, rain, rivers, lakes, and in underground aquifers. 

Lu JY, Chakrabarti CL, Back MH, et al. 1996. Speciation of some metals in river surface water, rain and snow, and the interactions of these metals with selected soil matrices. J Anal Atom Spectrom 11 1189-1201. 

Sekaly, A.L.R., C.L. Chakrabarti, M.H. Back, D.C. Gregoire, J.Y. Lu, and W.H. Schroeder. 1999. Stability of dissolved metals in environmental aqueous samples Rideau River surface water, rain and snow. Anal. Chim. Acta 402 223-231. 

Water may be found in nature as vapor and humidity in the atmosphere as a liquid in rain as surface water in rivers, streams, ponds, lakes, watersheds, and interior seas or forming part of seas and oceans. It is also found as groundwater, in vadose or unsaturated zones, occluded as interstitial water in the free spaces of soil and sediments, in springs and aquifers, or forming part of minerals as hydrates. It exists as a solid in glaciers, icebergs, hail, snow, and ice. Natural water may contain varying amounts of a myriad of chemical com-... 

The fallout of acid rains of surface waters has been studied for the last 15 years because of the impact on life in the lakes and rivers of Scandinavia, Scotland, and Canada as well as in the northeastern regions of the United States (Kramer and Tessier, 1982 Hilleman, 1983b). 

High concentrations of SO, can produce tempo-rai y breathing difficulties in asthmatic children and in adults who are active outdoors. Sulfur dioxide also can directly damage plants and has been shown to decrease crop yields. In addition, sulfur oxides can be converted to sulfuric acid and lead to acid rain. Acid rain can harm ecosystems by increasing the acidity of soils as well as surface waters such as rivers, lakes, and streams. Sulfur dioxide levels fell, on average, by 39 percent between 1989 and 1998. 

Much of the rain that reaches the ground runs off the surface of the land and flows into streams, rivers, ponds and lakes. Small streams lead to bigger ones, then to rivers, and eventually back to the oceans where the evaporation process begins all over again. 

Table II summarizes analytical data for dissolved inorganic matter in a number of natural water sources (J3, 9, J 9, 20, 21). Because of the interaction of rainwater with soil and surface minerals, waters in lakes, rivers and shallow wells (<50m) are quite different and vary considerably from one location to another. Nevertheless, the table gives a useful picture of how the composition of natural water changes in the sequence rain ->- surface water deep bedrock water in a granitic environment. Changes with depth may be considerable as illustrated by the Stripa mine studies (22) and other recent surveys (23). Typical changes are an increase in pH and decrease in total carbonate (coupled), a decrease in 02 and Eh (coupled), and an increase in dissolved inorganic constituents. The total salt concentration can vary by a factor of 10-100 with depth in the same borehole as a consequence of the presence of strata with relict sea water. Pockets with such water seem to be common in Scandinavian granite at >100 m depth.

Transport in water is an important mechanism for transfer of biogeochemical elements between the atmosphere, land, and oceans. In particular, rain is the primary means of removal from the atmosphere for many substances, and rivers (and to some extent groundwater) convey weathering products and runoff from the land surface to the oceans. 

Unlike other biogeochemical elements, phosphorus does not have a significant atmospheric reservoir. Thus, while some amount of phosphorus is occasionally dissolved in rain, this does not represent an important link in the phosphorus cycle. River runoff is the primary means of transport between the land surface and oceans, and unlike the other elements discussed. 

The Water Cycle. The evaporation of water from land and water surfaces, the transpiration from plants, and the condensation and subsequent precipitation of rain cause a cycle of transportation and redistribution of water, a continuous circulation process known as the hydrologic cycle or water cycle (see Fig. 86). The sun evaporates fresh water from the seas and oceans, leaving impurities and dissolved solids behind when the water vapor cools down, it condenses to form clouds of small droplets that are carried across the surface of the earth as the clouds are moved inland by the wind and are further cooled, larger droplets are formed, and eventually the droplets fall as rain or snow. Some of the rainwater runs into natural underground water reservoirs, but most flows, in streams and rivers, back to the seas and oceans, evaporating as it travels. 

However, salinity values are easily obtained with a salinometer (which measures electrical conductivity and is appropriately calibrated with standard solutions and adjusted to account for T effects). The salinity of seawater increases if the loss of H2O (evaporation, formation of ice) exceeds the atmospheric input (rain plus rivers), and diminishes near deltas and lagoons. Salinity and temperature concur antithetically to define the density of seawater. The surface temperature of the sea reflects primarily the latitude and season of sampling. The vertical thermal profile defines three zones surface (10-100 m), where T is practically constant thermoclinal (100-1000 m), where T diminishes regularly with depth and abyssal... 

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