Oxidationreduction Redox Potential

The redox potential measures the availability of electrons for exchange between chemical species. This may be viewed as analogous to pH, which measures the availability of protons (H+ ions) for exchange between chemical species. When H+ ions are exchanged, the acid or base properties of the species are changed. When electrons are exchanged, the oxidation states of the species and their chemical properties are changed, resulting in oxidation and reduction reactions. The electron donor is said to...

Carbon Dioxide Bicarbonate And Carbonate

The reactive inorganic forms of environmental carbon are carbon dioxide (CO2), bicarbonate (HCO3), and carbonate (CO32). Organic carbon, such as cellulose and starch, is made by plants from CO2 and water during photosynthesis. Carbon dioxide is present in the atmosphere and in soil pore space as a gas, and in surface waters and groundwaters as a dissolved gas. The carbon cycle is based on the mobility of carbon dioxide, which is distributed readily through the environment as a gas in the...

Soil CO2

Processes such as biodegradation of organic matter and respiration of plants and organisms which commonly occur in the subsurface consume O2 and produce CO2. In the soil subsurface, air in the pore spaces cannot readily equilibrate with the atmosphere, and therefore pore space air becomes lower in O2 and higher in CO2 concentrations. Oxygen may decrease from about 21 (210,000 ppmv) in the atmosphere to between 15 and 0 (150,000 to 0 ppmv) in the soil. Carbon dioxide may increase from about 0.04...

Groundwater flow

Redox Zone Groundwater

FIGURE 4.14b One year later, methane isopleths show that the methane enhanced zone has become larger, as the concentrations of alternative electron acceptors decreased. FIGURE 4.14b One year later, methane isopleths show that the methane enhanced zone has become larger, as the concentrations of alternative electron acceptors decreased. Field Test for Occurrence of Redox Reactions Map groundwater redox potentials at the site. Include at least one location upgradient of the plume. It is important...

Log Cw

FIGURE 4.5 Freundlich isotherm for benzene partitioning between water and soil. The equation of the least-squares fitted line is log Cs 0.941 log Cw - 0.468. Therefore, n 0.941 log Kd -0.468 Kd 0.340 L kg. Values for Kd are extremely site and chemical specific because the extent of sorption depends on several physical and chemical properties of both the soil and the sorbed chemical. For dissolved neutral organic molecules, such as fuel hydrocarbons, sorption to soil is controlled mostly by...

Bod5

BOD5 refers to a particular empirical test, accepted as a standard, in which a specified volume of sample water is seeded with bacteria and nutrients (nitrogen and phosphorus) and then incubated for 5 days at 20 C in the dark. BOD5 is measured as the decrease in dissolved oxygen (in mg L) after 5 days of incubation. The BOD5 test originated in England, where any river contaminant not decomposed within 5 days will have reached the ocean. Water surface turbulence helps to dissolve oxygen from the...

Dissolved Oxygen Do

Sufficient dissolved oxygen (DO) is crucial for fish and many other aquatic life forms. DO is important for high quality water. It oxidizes many sources of objectionable tastes and odors. Oxygen 0 20 40 60 80 100 120 140 160 180 200 FIGURE 3.5 Relation between hardness expressed as mg L and grains per gallon (gpg). becomes dissolved in surface waters by diffusion from the atmosphere and from aquatic-plant photosynthesis. On average, most oxygen dissolves into water from the atmosphere only a...

Hardness

Originally, water hardness was a measure of the ability of water to precipitate soap. It was measured by the amount of soap needed for adequate lathering and served also as an indicator of the rate of scale formation in hot water heaters and boilers. Soap is precipitated as a gray bathtub ring deposit mainly by reacting with the calcium and magnesium cations (Ca2+ and Mg2+) present, although other polyvalent cations may play a minor role. Hardness has some similarities to alkalinity. Like...

Drinking Water Standards

Potential Health Effects from Ingestion of Water Increase in blood cholesterol, decrease in blood glucose. system problems, increased risk of cancer. Increased risk of developing benign intestinal polyps. Some people who use water containing chromium well in excess of the MCL for many years could experience allergic dermatitis. Short-term exposure gastrointestinal distress. Long-term exposure liver or kidney damage. Those with Wilson's disease should consult their doctor if their water systems...

Measuring impurities

There are four characteristics of water impurities that are important for an initial assessment of water quality 1. What impurities are present Are they regulated compounds 2. How much of each impurity is present Are any standards exceeded for the water body being sampled 3. How do the impurities influence water quality Are they hazardous Beneficial Unaes-thetic Corrosive 4. What is the fate of the impurities How will their location, quantity, and chemical form change with time The chemical...

Soil Groundwater and Subsurface Contamination

Fulvic Acid Fractions

Steps in the Typical Development of a Soil and Its Profile (Pedogenesis) 4.5 Contaminants Become Distributed in Water, Soil, and Air Air-Water Partition Coefficient Soil-Water Partition Coefficient Determining Kd Experimentally The Role of Soil Organic Matter The Octanol Water Partition Coefficient, Kow Estimating Kd Using Solubility or Kow 4.7 Mobility of Contaminants in the Subsurface Effect of Biodegradation on Effective Retardation Factor A Model for Sorption and Retardation Soil Properties...

Predicting Bond Type From Electronegativities

Intermolecular forces are electrostatic in nature. Molecules are composed of electrically charged particles (electrons and protons), and it is common for them to have regions that are predominantly charged positive or negative. Attractive forces between molecules arise when electrostatic forces attract positive regions on one molecule to negative regions on another. The strength of the attractions between molecules depends on the polarities of chemical bonds within the molecules and the...

Nitrate NO3 CAS 14797558 Nitrite NO2 CAS 14797650 Background see Chapter 3 for a more detailed discussion

Nitrate and nitrite are highly soluble in water. Due to their high solubility and weak retention by soil, nitrate and nitrite are very mobile, moving through soil at approximately the same rate as water. Thus, nitrate and nitrite have a high potential to migrate to groundwater. Because they are not volatile, nitrate and nitrite are likely to remain in water until consumed by plants or other organisms. Nitrate is the oxidized form and nitrite is the reduced form. Aerated surface waters will...

Indicators Of Fecal Contamination Coliform And Streptococci Bacteria

Detecting and preventing fecal contamination is of prime importance for all drinking water systems and recreation water managers. Fecal wastes may contain enteric pathogens (disease-causing organisms from the intestines of warm-blooded animals) such as viruses, bacteria, and protozoans (which include Cryptosporidium and Giardia). Fecal contaminated water is a common cause of gastrointestinal illness, including diarrhea, dysentery, ulcers, fatigue, and cramps. It also may carry pathogens that...

Breakpoint Chlorination For Removing Ammonia

Chlorine Breakpoint Drinking Water

Chlorination can be used to remove dissolved ammonia and ammonium ion from wastewater by the chemical reactions NH3 + Cl2 NH2Cl + Cl- + H+. (6.6a) NH4+ + Cl2 NH2Cl + Cl- + 2 H+. (6.6b) Ammonia is converted stoichiometrically to monochloramine (NH2Cl) at a 1 to 1 molar ratio or a 5 to 1 ratio by weight of Cl2 to NH3-N. NHCl2 (dichloramine), and NCl3 (nitrogen trichloride or Suggested Maximum Parameter Levels in Water Used for Crop Irrigation total dissolved solids (TDS) mg L specific...

Drinking Water Treatment

Clean drinking water is the most important public health factor. But well over 2 billion people worldwide do not have adequate supplies of safe drinking water. Worldwide, between 15 to 20 million babies die every year from water-borne diarrheal diseases such as typhoid fever, dysentery, and cholera. Contaminated water supplies and poor sanitation cause 80 of the diseases that afflict people in the poorest countries. The development of municipal water purification in the last century has allowed...

Magnesium Mg CAS 7439954 Background

Magnesium is used in the textile, tanning, and paper industries. Lightweight alloys of magnesium are used extensively in molds, die castings, extrusions, rolled sheets and plate forgings, mechanical handling equipment, portable tools, luggage, and general household goods. The carbonates, chlorides, hydroxides, oxides, and sulfates of magnesium are used in the production of magnesium metal, refractories, fertilizers, ceramics, explosives and medicinals. Magnesium is abundant in the earth's crust...

Cadmium Cd CAS 7440439 Background

Cadmium is usually present in all soils and rocks. It occurs naturally in zinc, lead, and copper ores, in coal, and other fossil fuels and shales. It often is released during volcanic action. These deposits can serve as sources to groundwaters and surface waters, especially when they are in contact with soft, acidic waters. The adsorption of cadmium onto soils and silicon or aluminum oxides is strongly pH-dependent, increasing as conditions become more alkaline. When the pH is below 6-7,...

Mercury Hg CAS 7439976 Background

Mercury is a liquid metal found in natural deposits of ores containing other elements. Mercury deposits occur in all types of rocks igneous, sedimentary, and metamorphic. Although cinnabar (HgS) is the most common mercury ore, mercury is present in more than 30 common ore and gangue minerals. Mercury exists in the environment as the elemental metal, as monovalent and divalent salts, and as organic mercury compounds, the most important of which are methyl mercury (HgCH3+) and dimethyl mercury...

Lead Pb CAS 7439921 Background

Lead minerals are found mostly in igneous, metamorphic and sedimentary rocks. The most abundant lead mineral is galena (PbS). Oxide, carbonate, and sulfate minerals are lanarkite (PbO), cerrusite (PbCO3), and anglesite (Pb(SO4), respectively. Commercial ores have concentrations of lead in the range 30-80 g kg. Metallic lead and the common lead minerals have very low solubility. Most environmental lead (perhaps 85 ) is associated with sediments the rest is in dissolved form. Although some lead...

Nitrogen Ammonia Nh3 Nitrite No2 And Nitrate No3

Solubility Curve

Nitrogen compounds of greatest interest to water quality are those that are biologically available as nutrients to plants or exhibit toxicity to humans or aquatic life. Atmospheric nitrogen (N2) is the primary source of all nitrogen species, but it is not directly available to plants because the N N triple bond is too strong to be broken by photosynthesis. Atmospheric nitrogen must be converted to other nitrogen compounds before it can become available as a plant nutrient. The conversion of...

Acidity And Alkalinity

Diagram Alkalinity

The alkalinity of water is its acid-neutralizing capacity. The acidity of water is its base-neutralizing capacity. Both parameters are related to the buffering capacity of water the ability to resist changes in pH when an acid or base is added . Water with high alkalinity can neutralize a large quantity of acid without large changes in pH on the other hand, water with high acidity can neutralize a large quantity of base without large changes in pH. Acidity is determined by measuring how much...

Ph And Water Quality

Scale Common Substances

Pure water always contains a small number of molecules that have dissociated into hydrogen ions H and hydroxyl ions OH , as illustrated by Equation 3.1. The water dissociation constant, Kw is defined as the product of the concentrations of H and OH- ions, expressed in moles per liter where enclosing a species in square brackets is chemical symbolism that represents the species concentration in moles per liter. Because the degree of dissociation increases with temperature, Kw is temperature...

National Recommended Water Quality Criteria

Adapted from EPA 822-Z-99-001, April 1999. Section 304 a 1 of the Clean Water Act requires the EPA to develop, publish, and revise water quality criteria so that they accurately reflect the latest scientific knowledge. These criteria are based solely on a scientific interpretation of data concerning the relation between pollutant concentrations and environmental and human health effects. Considerations of technological feasibility or economic impacts of attaining the recommended criteria are...