Page 52 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

40 CHAPTER 2 The Ocean Environment
2.2.13.2 Oxidation reduction potential
Oxidation reduction potential (ORP) is the measure of the difference in electrical potential between a relatively chemically inert electrode and an electrode placed in a solution. Water quality research- ers use ORP to measure the activity and strength of oxidizers (those chemicals that accept elec- trons) and reducers (those that lose electrons) in order to monitor the reactivity of drinking water and groundwater.
2.2.13.3 Rhodamine
Rhodamine, a highly fluorescent dye, has the unique quality to absorb green light and emit red light. Very few substances have this capability, so interference from other compounds is unlikely, making it a highly specific tracer. Water quality researchers use rhodamine to investigate surface water, wastewater, pollutant time of travel, groundwater tracing, dispersion and mixing, circulation in lakes, and storm water retention.
2.2.13.4 Specific conductance
Specific conductance is the measure of the ability of a solution to conduct an electrical current. However, unlike the conductivity value, specific conductance readings compensate for temperature. In addition, because specific conductance and ion concentration are highly correlated, specific con- ductance measurements are used to calculate ion concentration in solutions. Specific conductance readings give the researcher an idea of the amount of dissolved material in the sample. Water qual- ity researchers take specific conductance readings to determine the purity of water, to watch for sudden changes in natural or wastewater, and to determine how the water sample will react in other chemical analyses.
2.2.13.5 Total dissolved solids
Total dissolved solids (TDS) is the measure of the mass of solid material dissolved in a given vol- ume of water and is measured in grams per liter. The TDS value is calculated based on the specific conductance reading and a user-defined conversion factor. Water quality researchers use TDS mea- surements to evaluate the purity or hardness of water, to determine how the sample will react in chemical analyses, to watch for sudden changes in natural or wastewater, and to determine how aquatic organisms will react to their environment.
2.2.14 Dissolved gases
Just as a soda dissolves CO2 under the pressure of the soda bottle, so does the entire ocean dissolve varying degrees of gases used to sustain the life and function of the aquatic environment. The soda bottle remains at gas
fluid equilibrium under the higher-than-atmospheric pressure condition until the bottle is opened and the pressure within the canister is lowered. At that point, the gas bubbles out of solution until the gas/air mixture comes back into balance. If, however, that same bottle were opened in the high-pressure condition of a saturation diving bell deep within the ocean, that soda would (instead of bubbling) absorb CO2 into solution until again saturated with that gas.
The degree of dissolved gases within a given area of ocean is dependent upon the balance of all gases within the area. The exchange of gases between the atmosphere and ocean can only occur at the air
ocean interface, i.e., the surface. Gases are dissolved within the ocean and cross the air/water