Freshwater and Groundwater

Freshwater is the term used to denote natural waters that have low concentrations (less than 500 ppm) of dissolved salts and solids. Freshwater includes the waters of lakes, rivers, ponds, and streams. The United States is fortunate in its abundance of freshwater—1.7 X 10 L (660 trillion gallons) is the estimated reserve, which is renewed by rainfall. An estimated 9 X 10 L of freshwater is used every day in the United States. Most of this is used for agriculture (41%) and hydroelectric power (39%), with small amounts for industry (6%), household needs (6%), and drinking water (1%). An adult drinks about 2 L of water per day. In the United States, our daily use of 

Freshwater is the term used to denote natural waters that have low concentrations (less thcui 500 ppm) of dissolved salts and solids. Freshwater includes the waters of 

How would you expect the temperature variation to affect the density of seawater in the range 0 to 100 m depth  

As water runs off the land on its way to the oceans, it dissolves a variety of cations (mainly Na , K , Mg , Ca, and Fe ), anions (mainly Cr, S04 , and HC03 ), and gases (principally O2, N2, and CO2). As we use water, it becomes laden with additional dissolved material, including the wastes of human society. As our population and output of environmental pollutants increase, ever-increasing amounts of money and resources must be spent to guarantee a supply of freshwater. 

The availability and cost of fresh water that is clean enough to sustain daily life varies greatly among nations. To illustrate, daily fresh water use in the United States approaches 600 L/person, whereas in the relatively underdeveloped nations of sub-Sahara Africa it is only about 30 L. To make matters worse, for many people, water is not only scarce, it is so contaminated that it is a continuing source of diseases. 

Approximately 20% of the world s freshwater is under the soil, in the form of groundwater. Groundwater resides in aquifers, which are layers of porous rock that hold water. The water in aquifers can be very pure, and accessible for human consumption if near the surface. Dense imderground formations that do not allow water to readily penetrate can hold groundwater for years or even millennia. When their water is removed by drilling and pumping, such aquifers are slow to recharge via the diffusion of surface water. 

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The water budget of the modern Earth The water budget of the modern Earth might be loosely divided into the outer Earth reservoirs and the mantle. In the outer Earth reservoirs there is about 1.4 X 1021 kg of water currently stored at the Earth s surface as the oceans, ice, freshwater, and groundwater. This makes up 0.0002 of the Earth s mass and is equivalent to 1.515 X 1023 g of hydrogen (Lecuyer et al., 1998). Assessing the water content of the mantle is more difficult and depends mostly upon experimental studies of the solubility of water in mantle minerals and melts. These concentrations are low, for... 

We examine the global water cycle, which describes how water moves from the ground to surface water to the atmosphere and back into the ground. We compare the chemical compositions of seawater, freshwater, and groundwater. 

Describe the properties that most clearly distinguish among saltwater, freshwater, and groundwater. [Section 18.3]... 

Nonreplenishable (fossil) groundwater can be tapped, but such extraction depletes reserves in much the same way as extractions from oil wells do. The terrestrial renewable freshwater supply, RFITTj, equals precipitation on land, which then subdivides into two major segments evapotranspiration from the land, and mnoff to the sea, T. Because groundwater and surface water are often hydrauhcaHy coimected, soil infiltration and groundwater... 

Zinc concentrations in freshwater, seawater, groundwater, sewage sludge, sediments, and soils are listed in Table 9.3. These data are considered reliable, although clean-laboratory techniques suggest that dissolved Zn concentrations in nonpolluted rivers may be 10 to 100 times lower than previously reported (Shiller and Boyle 1985). 

Dissolved humic substances (DHS) are the main constituents of the dissolved organic carbon (DOC) pool in surface waters (freshwaters and marine waters), groundwaters, and soil porewaters and commonly impart a yellowish-brown color to the water system. Despite the different origins responsible for the main structural characteristics of DHS, they all constitute refractory products of chemical and biological degradation and condensation reactions from plant or animal residues and play a crucial role in many biogeochemical processes. 

Aside from desalinators used in some regions of the world that have severe insufficiencies of rain and freshwater and thus must depend upon purified saline waters, drinking water and the water required by industry for a plurality of reasons come from two classes of natural sources. The first is surface waters from ponds, streams, rivers, lakes, waterfalls, and glaciers. Natural water precipitation (rain and snow) is the result of Earth s natural hydrologic cycle. Precipitation also reaches below Uie surface to collect or flow in aquifers and thus is referred to as groundwater. See also Desalination. 

Brunke, M., and T. Gonser. 1997. The ecological significance of exchange processes between rivers and groundwater. Freshwater Biology 37 1-33. 

The types of media extrapolations routinely required and used in risk assessments include air-water, air-soil, water-sediment, and groundwater-soil. Matrix extrapolations include saltwater-freshwater, hard water-soft water, river-lake-stream-pond, and soil type adjustments. There are, in fact, a large number of different extrapolations possible, each with its own unique problems to be taken into account. 

As the world s population continues to grow, the demand for fresh water will certainly increase. Seventy five percent of the Earth s surface is covered with water. Out of this 75%, almost 97% of the world s water is salty and not readily drinkable. The other 2% is locked as solids, in the form of ice caps and glaciers, leaving us with about 1% of freshwater that is available for all humanity s need. This small amount of freshwater can be found in the form of surface water and groundwater. Of the 1% of freshwater available, 96% is in the form of groundwater. From 1940 to 1990, withdrawals of fresh water from rivers, lakes, reservoirs, and other sources have been augmented fourfold [28]. 

Similary, in freshwater and non-sulfidic brackish environments with strong O2 demand, dissolved ferrous-iron may accumulate in groundwaters and anoxic bottom waters. Significant iron oxidation will occur where the water... 

Drinking water is necessary for people, livestock, wildlife, crop irrigation, and for recreation. Although 70% of the Earth s surface is covered with water, most is salt water (salinity of 3.5%) and not fit to drink. Only 3% of the water on the Earth is freshwater (water that contains only minimal quantities of dissolved salts) and much of this water is in snow and ice (e.g., glaciers) as well as lakes, streams and groundwater. In some places in the world, freshwater is plentiful (e.g., the Great Lakes) however, in many places water is scarce. Wars have been fought over freshwater resources. 

Harm criteria for a major accident to the environment are also important. Both the built environment and the natural environment have to be considered. Major accidents can damage historic buildings or monuments, although these will be associated more with the physical consequences of the event than with chemical interactions. Damage to nature reserves, areas of natural beauty and freshwater and marine habitats, as well as groundwater and aquifer contamination all need careful examination when dealing with the natural environment In some cases individual rare species may be sufficiently important to merit special attention. The relevant criteria for use in the United Kingdom have been published by the Department of the Environment [22]. 

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