Surface water Rivers and lakes

Rivers and other forms of surface water actually account for a relatively small portion of the planet s water supply, but they loom large in the human imagination as the result of their impact on our lives. The first human civilizations developed along rivers in Egypt, Mesopotamia, India, and China, and today many great cities lie alongside rivers. Rivers provide us with a means of transportation and recrea- 

The chemical composition of river water is significantly different from that of seawater (Table 2.28). At first approximation, seawater is mainly a solution of Na and Cr while river water is a solution of Ca and HCOJ. Interestingly the ratio Na/Cl is the only one which is relatively similar for rivers and oceans, suggesting that both components are within a global cycle from seaspray through cloud transportation to continents and precipitation. Carbonate is approximately in equilibrium with atmospheric CO2 and the concentration difference between river water 

However, most of the sedimentary mass is of detrital origin. Nutrient elements (Si, P, V, N, and trace metals) are removed in the ocean as biological debris to sediments. The main sink of substances is by hydrothermal reactions (volcanic activity) at locations of seafloor spreading and circulation through the ocean crust. Volcanic activities in the oceans are extensive, and produce submarine lava flows which are unstable in seawater. The high temperature (200-400 °C) is not only important for basalt-seawater reactions but also triggers circulation. Subduction (see Chapters 2.2.1.1 and 2.6.4.3) transfers seawater and its constituents back to the magma. 

Because of the large volume of seawater, almost all ions are conservative, meaning it does not change its concentration over geological periods. However, there are differences for example, Cr is the most conservative ion in the climate system because it takes no part in any chemical reaction but Na , the counterpart is involved in rock weathering (it is a major constituent of silicate minerals), cation exchange, and possibly volcanic-seawater reactions and reverse weathering. 

Seawater, compared with all other natural waters, is remarkably constant in composition. However, all elements involved in biological turnovers (oxygen and carbon being the most important) may have variations (and possibly trends), again due to changing key parameters of the climate system, of which the temperature is the most important one. Concerning the global climate, the oceans have two essential functions  

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Rainwater and snowmelt water are primary factors determining the very nature of the terrestrial carbon cycle, with photosynthesis acting as the primary exchange mechanism from the atmosphere. Bicarbonate is the most prevalent ion in natural surface waters (rivers and lakes), which are extremely important in the carbon cycle, accoxmting for 90% of the carbon flux between the land surface and oceans (Holmen, Chapter 11). In addition, bicarbonate is a major component of soil water and a contributor to its natural acid-base balance. The carbonate equilibrium controls the pH of most natural waters, and high concentrations of bicarbonate provide a pH buffer in many systems. Other acid-base reactions (discussed in Chapter 16), particularly in the atmosphere, also influence pH (in both natural and polluted systems) but are generally less important than the carbonate system on a global basis. 

Transport mechanisms include mass movement of soil (soil erosion and landslides), wind, rain, surface waters (rivers and lakes), groundwater, and human intervention. The latter may consist of wastewater pipes, drainage ditches, roads, trains, ships, smoke stacks, etc. 

Surface water (rivers and lakes). Tlie physical composition depends on die river regime while the chemical composition is governed by the vagaries of urban or industrial discharges. 

In general, samples may be obtained from faucet outlets, at different points in pipe systems, from the surface of rivers and lake waters, and at different depths. The most important consideration is that the frequency and duration of sampling be sufficient to obtain a representative and reproducible sample. In some cases, composite samples may be used, in which individual samples taken at frequent intervals are combined. 

The area into which sewage waters are discharged, i.e. waters which have changed their quality after being used, is called the recipient. Mainly surface waters — rivers, brooks, lakes, ponds or seas, and sometimes also groundwaters serve as recipients. 

Natural waters encompass a wide variety of sample matrices including rainwater mineral spring waters groundwaters surface waters (river, stream, lake, and pond waters) soil pore waters runoff waters snow, hail, and sleet ice and ice cores and well and bore waters. 

The reason a heavy object can float on water is due to the fact that in order for the latter to sink, it must overcome the surface forces. Of course, if one merely drops the metal object, it will overcome the surface tension force and sink, which one generally observes. This clearly shows that at any liquid surface, there exists a tension (surface tension), which needs to be broken when any contact is made between the liquid surface and the material (here the metal needle). One notices ample of examples on the surfaces of rivers and lakes, where stuff is seen floating about. Based on the same... 

Global warming would also be expected to influence surface waters such as lakes and streams, through changes induced in the hydrologic cycle. However, the last published report of the IPCC states no clear evidence of widespread change in annual streamflows and peak discharges of rivers in the world (IPCC, 1995, p. 158). Wliile lake and inland sea levels have fluctuated, the IPCC also points out that local effects make it difficult to use lake levels to monitor climate variations. 

Several studies have been conducted to measure methyl parathion in streams, rivers, and lakes. A U.S. Geological Survey (USGS) of western streams detected methyl parathion in five river samples taken from four states during a 14-month period in 1970 and 1971. The amount of methyl parathion detected ranged from 0.04 to 0.23 pg/L (Schultz et al. 1973). A later and more extensive USGS study analyzed water samples from major rivers of the United States four times yearly in the period of 1975-1985. Of the 2,861 water samples, 0.1% had detectable levels of methyl parathion (Gilliom et al. 1985). In a study of Arkansas surface waters, samples of lake and river/stream water were collected and analyzed over a three-year period (Senseman et al. 1997). Of the 485 samples collected, methyl parathion was found in one river/stream sample at a maximum concentration of 3.5 pg/L. Results from an EPA study in California detected methyl parathion in 3 of 18 surface drain effluent samples at concentrations of 10-190 ng/kg. Subsurface drain effluent water had concentrations of 10-170 ng/kg in 8 of 60 samples (lARC 1983). 

Hydrological cycle The cyclic transfer of water vapor from the Earth s surface via evapotranspiration into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into the oceans (U.S. Geological Survey, 2003). 

All point source and nonpoint source wastewaters at an industrial site must be properly managed for source separation, waste minimization, volume reduction, collection, pretreatment, and/or complete end-of-pipe treatment [39,47]. When industrial waste is not disposed of properly, hazardous substances may contaminate a nearby surface water (river, lake, sea, or ocean) and/or groundwater. Any hazardous substance release, either intentionally or unintentionally, increases the risk of water supply contamination and human disease. Major waterborne contaminants and their health effects are listed below. 

All water that is below Earth s surface is called groundwater. (Liquid water that is on the surface—in streams, rivers, and lakes—is called, naturally enough, surface water.) Any water-bearing soil layer is called an aquifer, which can be thought of as an underground water reservoir. Aquifers underlie the land in many places and collectively contain an enormous amount of fresh water— approximately 35 times the total volume of water in fresh water lakes, rivers, and streams combined. More than half the land area of the United States is underlain by aquifers, such as the Ogallala Aquifer stretching from South Dakota to Texas and from Colorado to Arkansas ... 

Water is the commonest compound on this planet. More than 70% of the Earth s surface is covered with sea, and the land masses are dotted with rivers and lakes (Figure 11.26a). It is vital to our existence and survival because it is one of the main constituents in all living organisms. For example, your bones contain 72% water, your kidneys are about 82% water and your blood is about 90% water (Figure 11.26b). 

Silver levels of less than 0.000001 mg silver per cubic meter of air (mg/m3), 0.2-2.0 parts silver per billion parts water (ppb) in surface waters, such as lakes and rivers, and 0.20-0.30 parts silver per million parts soil (ppm) in soils are found from naturally occurring sources. Silver compounds are also found in groundwater and at hazardous waste sites throughout the United States. Drinking water supplies in the United States have been found to contain silver levels of up to 80 ppb. Surveys show that one - tenth to one - third of samples taken from drinking water supplies (both groundwater and surface water) contain silver at levels greater than 30 ppb. For more information on exposure to silver see Chapter 5. 

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