Gravity: KnowFlow Basic Kit – A DIY Water Monitoring Basic Kit

Conductivity is a measure of the ability of water to allow electricity to flow. This ability is directly related to the concentration of ions in the water. These conductive ions are derived from dissolved salts and minerals such as alkalis, chlorides, sulfides and carbonates.

The more ions there are, the higher the conductivity of the water. Distilled or deionized water can act as an insulator due to its very low (if not negligible) conductivity value. Seawater, on the other hand, has a very high conductivity.

Ions

Ions produce electricity due to their positive and negative charges. When electrolytes dissolve in water, they are divided into positively charged (cations) and negatively charged (anion) particles. As the solutes are separated in water, the concentrations of each positive and negative charge remain equal. This means that although the conductivity of water increases with the addition of ions, it remains electrically neutral.

Conductivity units

Conductivity is usually measured in micro- or millimeters per centimeter (uS / cm or mS / cm).

Tolerance of aquatic organisms

Most aquatic organisms can only tolerate a certain range of salinity. The physiological adaptation of each species is determined by the salinity of its environment. Most species of fish are exclusively freshwater or exclusively saltwater. However, there are some organisms that can adapt to a range of salinities.
Some aquatic organisms may even be sensitive to the ionic composition of water. The inflow of a particular salt can adversely affect a species, regardless of whether the salinity levels remain within an acceptable range.

Salinity tolerances

Salinity tolerances depend on osmotic processes within an organism. Fish and other aquatic animals that live in fresh water (low conductivity) are hyperosmotic. Hyperosmotic determines a cell’s ability to eliminate water and retain ions. Thus, these organisms maintain higher internal ion concentrations than the surrounding water. At the other end of the spectrum, saline (high-conductivity) organisms are subcellular and maintain a lower internal ionic concentration than seawater. Changing the conductivity of the environment by increasing or decreasing salt levels will adversely affect the metabolic capacity of organisms.

Conduction change may indicate contamination
Oil or hydrocarbons can reduce the conductivity of water.
A sudden increase or decrease in conductivity in a body of water may indicate contamination. Agricultural runoff or sewage leakage will increase conductivity due to additional chloride, phosphate and nitrate ions. Leaking oil or adding other organic compounds will reduce the conductivity as these elements do not break down into ions. In both cases, the added solids will have a negative impact on water quality.

pH and Living Organisms

If the pH of the water is too high or too low, the aquatic organisms living in it will die. PH can also affect the solubility and toxicity of chemicals and heavy metals in water. The majority of aquatic creatures prefer a pH range of 6.5-9.0. As pH levels move away from this range (up or down) animal systems can be affected and incubation and survival rates reduced. The more sensitive a species is, the more it is affected by changes in pH. In addition to the biological effects, extreme pH levels usually increase the solubility of elements and compounds, making toxic chemicals more “mobile” and increasing the risk of absorption by aquatic organisms.

pH vs Humans

Aquatic species are not the only ones affected by pH. While people have a higher tolerance for pH levels (drinking levels range from 4-11 with minimal gastrointestinal irritation), there are still concerns. PH values ​​above 11 can cause skin and eye irritation, as can pH below 4. A pH value below 2.5 will cause irreversible damage to the skin and organs. Lower pH levels increase the risk of mobilizing toxic metals that can be absorbed, even by humans, and levels above 8.0 cannot be effectively disinfected with chlorine, causing other indirect hazards. In addition, pH levels other than 6.5-9.5 can damage and corrode pipes and other systems, further increasing the toxicity of heavy metals.

There are many factors that can affect the pH of water, natural and artificial. Most natural changes occur due to interactions with the environment (especially carbonate forms) and other materials. The pH can also fluctuate with sedimentation (especially acid rain) and wastewater or mining waste. In addition, CO2 concentrations can affect pH levels.

Carbon dioxide

Carbon dioxide is the most common cause of acidity in water. Photosynthesis, respiration and decomposition all contribute to pH fluctuations due to their effects on CO2 levels.
Carbonaceous materials and limestone are two elements that can regulate pH changes in water. Calcium carbonate (CaCO3) and other bicarbonates can be combined with both hydrogen and hydroxyl ions to neutralize the pH. When carbonate minerals are present in the soil, the regulating capacity (alkalinity) of the water increases, keeping the pH of the water close to neutral even when acids or bases are added. Extra carbonate materials in addition to this can make neutral water slightly basic.

Anthropogenic causes

Anthropogenic causes of pH fluctuations are usually related to pollution. Acid rain is one of the best known examples of human influence on water pH. Any form of precipitation with a pH level less than 5.0 is known as acid rain. This precipitation results from the reaction of water with nitrogen oxides, sulfur oxides and other acidic compounds, lowering its already slightly acidic pH. These emissions usually come from mining and smelting or burning fossil fuels (coal and cars). Extremely high CO2 levels can also further reduce the pH of rain.

Harmful effects are felt when the pH of the water falls below 5.0 or rises above 9.6. The adverse effects due to acidification are more pronounced in saltwater fish due to their adaptation to higher pH. When the pH is below optimal levels, fish become susceptible to fungal infections and other bodily harm. As the pH of the water decreases, the solubility of calcium carbonate decreases, preventing the growth of the shell in aquatic organisms. In general, fish breeding is affected at pH levels below 5.0 and many species will leave the area. Fish begin to die when the pH drops below 4.0.

Harmfull effects of low pH levels

Low pH levels can encourage the solubility of heavy metals. As the level of hydrogen ions increases, metal cations such as aluminum, lead, copper and cadmium are released into the water instead of being absorbed into the precipitate. As heavy metal concentrations increase, so does their toxicity. Aluminum can limit growth and reproduction while increasing mortality at concentrations as low as 0.1-0.3 mg / L. In addition, mobilized metals can be taken up by organisms during respiration, causing physiological damage. This is especially harmful for species such as iridescent trout.