Different pH levels in water can support different ecosystems
If a pH is too low or too high, aquatic organisms will die off. Most aquatic organisms require pH levels between 6.5 and 9.0, though some can survive at levels outside of this margin. Additionally, pH can greatly affect how well certain chemicals and heavy metals dissolve in the water, as well as causing some of these substances to become more toxic.
pH levels in drinking water and food can impact our bodies
Our bodies need to maintain a pH of about 7.4 in order to function properly. Acidity (low pH) will decrease the body’s uptake of minerals and nutrients and decrease its ability to detoxify heavy metals. Acidity in the body will also decrease energy production in the cells and limit the body’s ability to restore damaged cells. Additionally, a low pH allows tumor cells to develop in the body.
Alkalinity and pH go hand in hand. Alkalinity, also known as a buffer capacity, measures the ability of a body of water to neutralize acidity caused by acid rain or other pollutants, or in other words, resist changes in pH. Without this ability of a water source to neutralize acidity, the addition of any acidic source, such as acid rain or industrial wastewater, would cause an immediate change in the pH of the water.
The alkalinity of a stream is based on the soil and bedrock in the stream, which contain compounds like Bicarbonates, Carbonates, and Hydroxides. All of these compounds work by removing Hydrogen ions from the water, therefore lowering acidity and raising the pH.
Chloride ions are a result of the splitting of salt ions in water. Salt, or sodium chloride, is made from positive sodium ions bonded to negative Chloride ions, which separate when the ionic compound dissolves in water. Some sources of Chloride Ions include runoff from salted roads, irrigation water returned to streams, and water softeners and chlorinated drinking water in wastewater. Additionally, Chloride can occur naturally in streams when the streambed is made up of salt-containing minerals.
Chloride is harmful to aquatic life. If levels remain high in a stream, they may begin to build up in the aquatic organisms, reaching toxic levels; this is known as bioaccumulation.
Also, Chloride may cause the release of metals from sediments at the bottom of a stream, which leads to metal toxicity in aquatic organisms, causing the animals to suffocate to death. In relation to drinking water, Chloride is not generally harmful at high levels, although it will start to have an unpleasant taste at levels exceeding 250 mg/l. At low levels, Chloride does not harm the human body, though it may cause unwanted taste and odor issues at higher levels.
Dissolved Oxygen enters a stream by two main sources: the atmosphere and aquatic vegetation. Oxygen from the atmosphere uses the movement of the stream to mix into the water, therefore becoming dissolved Oxygen. Faster flowing water tends to have more DO, where stagnant waters such as lakes and ponds will have less. The second source, aquatic vegetation, releases Oxygen into the stream by the process of photosynthesis.
DO levels are generally higher during mid-day, when the sun is at its peak and photosynthesis is occurring, then levels will drop at night when Oxygen is being used for respiration by plants and animals. Both temperature and atmospheric pressure will determine just how much Oxygen can dissolve into the water; lower temperatures result in higher DO, and higher altitudes result in lower DO. Some pollutants that can affect DO in water are acid mine drainage, agricultural runoff, and industrial waste. The last two pollutants mentioned possess organic matter, which must be broken down by microorganisms by a process known as decomposition, which requires the use of Dissolved Oxygen. This process causes a decrease in DO availability for all other aquatic life in the stream. Additionally, the development of land and destruction of vegetation along the stream will cause for less shade cover, resulting in a higher water temperature and therefore less DO.
Why does dissolved oxygen matter?
Aquatic organisms are no different than us, in that they require oxygen to sustain life
Certain organisms, such as mayflies, trout, and salmon, require more DO than others. Some aquatic organisms which can survive at low DO levels include black flies and carp. Oxygen can also affect the physical state of different chemicals in a stream. Some chemicals will remain solid in an Oxygen rich environment; however, if the water lacks Oxygen, the chemical may dissolve into the water, having a toxic effect on the aquatic life.
Ammonia is a form of Nitrogen. Nitrogen is essential in an aquatic environment in order for plants and animals to form amino acids; however, it cannot be used in its molecular form. For this reason, it must be converted to another form, such as ammonia. In water, ammonia is present in two forms. The first form, NH3, is known as unionized ammonia; the second, NH4+, is known as ionized ammonia, or ammonium. Which form is present is dependent upon the temperature and pH of the water. The un-ionized form of ammonia, NH3, is prevalent at higher temperatures and at a pH greater than 8.0. The unionized form is also the more toxic one in relation to aquatic life. Both of these forms make up the Total Ammonia in the water.
Elevated levels of ammonia can lead to increased vegetation and algal growth. It can also lead to nitrification, a process by which ammonia is converted into nitrate by bacteria in the water. This process uses a lot of dissolved oxygen that is necessary for the survival of fish and other aquatic life.
Total Dissolved Solids is a measure of all dissolved solids in a water source. Total dissolved solids are made up of inorganic salts, such as calcium, magnesium, potassium, sodium, bicarbonates, chlorides and sulfates, as well as some organic matter. Pure water is odorless and tasteless, whereas water contaminated with high levels of TDS may be bitter, salty, corrosive, and cause precipitates to form. Though these effects are more aesthetic concerns than anything else, high TDS levels should not be ignored, as they may also indicate the presence of toxic ions, such as lead, arsenic, cadmium and nitrate. EPA secondary drinking water standards lists the MCL (Maximum Contaminant Level) for TDS at 500 mg/L, due to a noticeable and unpleasant change in taste, odor and scale deposits. Any water exceeding 1000 mg/L is deemed unfit for consumption.
What are some sources of TDS?
Organic matter can contribute to TDS. Sources may include leaves, silt, plankton, industrial waste, road salt, and agricultural runoff. Sources of inorganic dissolved solids include rocks and atmospheric deposition; much of the latter form salts, which contain both metal and nonmetal, and will dissolve in water to form ions.
TDS and Aquatic organisms
TDS can lead to an increase in salinity (dissolved salt in water) and toxicity of individual ions, as well as changes in ionic compounds. These changes lead to a decrease in biodiversity, with some species benefitting, while other, less tolerant ones will suffer.
Conductivity measures the ability of a water source in passing along an electrical current, which correlates with the number of ions in the water. Pure water, AKA, the universal solvent, containing only H2O and none of the salt or mineral ions that occur in most waters, would measure very low in electric conductivity. In comparison, water with more dissolved salt ions would exhibit a high conductivity measurement. Additionally, a higher temperature leads to an increase in electric conductivity.
How do ions work?
Ionic compounds that dissolve in water are known as electrolytes. Sodium Chloride, or salt, dissolves in water, and the ionic compound breaks down into Na+ and Cl-; their negative and positive charge allow them to conduct electricity. Though conductivity does not pinpoint the exact ion present in the water, a rise in electrical current may indicate the addition of new pollutant discharges, such as nitrates and phosphates, which when present in elevated levels can cause harm to the aquatic life in an ecosystem. In order for a stream to promote biodiversity, conductivity should be between 150-500 µS/cm. Conductivity is also important in the calculations of salinity and TDS.
Coliform bacteria are anaerobic, rod-shaped organisms which are unable to form spores, leaving them subject to destruction by different environmental factors. If they were spore-forming bacteria, then that would mean they were able to form endospores, which are structures that allow the bacteria to rest and withstand difficult environmental conditions; once the conditions become optimal again, the endospores transform into new bacteria.
Coliform bacteria may be more prevalent in a water source due to heavy rainfall or snowmelt, sewage treatment plant effluent, agricultural runoff, stormwater runoff, and food processing plant discharges. Some of these discharges also contain nutrients such as Phosphorus and Nitrogen, which can lead to oxygen depletion and changes in the pH of the water, therefore affecting aquatic life.
Faecal coliform is the bacteria present in human and animal waste. The most tested indicator bacteria for faecal coliform is Escherichia coli, better known as E. coli, which can contain both pathogenic and non-pathogenic bacteria. This type of bacteria thrives at warm temperatures and comes specifically from the fecal matter of warm-blooded organisms. There are microorganisms present in water that destroy these bacteria; however, when bacteria levels exceed the number of microorganisms in the water, it can be assumed that the risk of pathogenic diseases will increase, posing a threat to humans as well as aquatic organisms.
Total coliform, however, is a more general term, including both faecal and non-faecal bacterium, the latter of which come from soil. If tests for Total coliform come back positive in a water source, then it is also possible that there is pathogenic coliform in the water, and the sample should then be tested for E. coli.
Nutrients support an abundance of algae, bacteria, and other microorganisms in a water source. When there is an accumulation of nutrients in water, the result can be excess algae growth. The two main nutrients present in water are Nitrogen and Phosphorous.
Eutrophication is a direct effect of excess nutrients in water. This leads to an explosive growth of algae, which has a negative cascading effect on the aquatic ecosystem. Too much algae will decrease water clarity, making it so that sunlight cannot penetrate to the necessary depth for photosynthesis to occur.
Also, the more algae present, the more respiration that is occurring. Eventually, the algae will die off, at which time microorganisms will act as decomposers of the organic matter. All of these effects of excess nutrients cause oxygen depletion in the water, which in turn effects every organism that lives there. In the summer months, the oxygen depletion may lead to even more deaths of aquatic life due to the fact that warm water already holds less oxygen, and therefore the oxygen demand is even greater in order to compensate and sustain certain species. These nutrients also have the potential to produce toxic algal blooms such as blue-green algae, which is toxic to both aquatic and terrestrial organisms.
Nitrogen is needed for the synthesis of proteins in plants and animals to form tissues. It can be found naturally in the environment, such as in the tissue of living and dead organisms, as well as by anthropogenic means, such as agricultural runoff and sewage discharge.
Phosphorus, on the other hand, is used in cell production, and for changing sunlight into energy by the process of photosynthesis. Phosphorous occurs naturally by the weathering of rocks and minerals in water, but is also largely present today in the form of sewage treatment discharge and agricultural runoff.