Water Chemistry Lab Tests
Alkalinity – The result of this test indicates the water’s buffering capacity. Water with adequate buffering capacity can limit dangerous pH swings caused by the introduction of highly acidic substances, such as acid rain and pollution, the affects of which can be compounded by the subsequent loss of plant, algal, and other aquatic life.
Ammonia – If Ammonia is present in significant quantities, it can indicate that the water column does not have sufficient oxygen to oxidize Ammonia to Nitrite and Nitrate. Ammonia can be toxic to fish and other animals. The level of toxicity however is based on the total ammonia concentration, pH, and temperature. When levels are higher than 1.0 mg/L, it is likely that the pond is being exposed to unusual discharges (such as treated wastewater). In such case, multiple management strategies may be required to reduce Ammonia levels. Ammonia concentrations below 0.30 mg/L significantly help to limit plant and algae growth in low phosphorus lakes. Reduced fertilizer applications near shorelines can sometimes help prevent increases in this and other nutrient levels, but much of the Ammonia and phosphate present in older lakes (5+ years) is recycled from the sediment. Both aeration and dredging can reduce this internal loading.
Chloride/Salinity – The Chloride ion is one of the major inorganic anions in water and wastewater. In coastal communities Chloride levels may be high due to saltwater intrusion or urban and agricultural runoff. Although chloride is essential to plants in very low amounts, it can cause toxicity to sensitive crops at high concentrations. Irrigation systems should not exceed 350ppm for chloride to prevent damage to foliage.
Salinity is the measure of dissolved salt content in water and is expressed in ppm (mg/L). For the protection of lake and watershed health, freshwater salinity should remain at or below 0.5 ppm. Water with high salinity is toxic to plants and may become hazardous to the ecosystem.
High levels of Chloride or Salinity may be caused by the proximity of the lake to the ocean or low water levels which cause salts to become more concentrated within the water body. If irrigation water receives reclaimed water high in salt content, it may pose a problem for turf grass and surrounding plants.
Color – The measured value for color reflects decomposition of organic matter in the lake. This organic matter may be the result of decaying plankton and aquatic plants or other inputs from the surrounding watershed. Freshwater color levels are expected to range from 0-300 mg/L. High color values may be indicative of low light penetration in the water column which may have adverse effects on aquatic life. Such an effect could reduce light penetration, thereby restricting photosynthetic abilities of phytoplankton and aquatic plant growth.
Conductivity and total dissolved solids (TDS) – These measurements estimate the total concentration of ionized substances dissolved in the water. Total Dissolved Solids (TDS) is a measure of ionized substances dissolved in water. The inorganic anions dissolved in water include carbonates, chlorides, sulfates and nitrates, while inorganic cations include sodium, potassium, calcium and magnesium. The capacity of water to conduct an electrical current is related to the type and amount of ions in the water and conductivity is a measure of this capacity. There is therefore a relationship between total dissolved solids and conductivity, whereby the concentration of dissolved substances can be estimated based on the water’s ability to conduct an electrical current.
Lake water TDS and Conductivity levels vary naturally based on the specific characteristics of the lake (e.g. geology, proximity to the sea, etc). For example, freshwater generally exhibits conductivity less than 500 μS/cm. If levels above this are observed, it may be an indication of pollution or simply be due to some marine influence. A significant and acute increase in conductivity may indicate a recent increase in domestic or industrial pollution. High dissolved solids may cause irrigation water to stain vehicles and other surfaces in the general vicinity.
Hardness/Alkalinity – Alkalinity indicates the water’s buffering capacity; i.e. the water’s capacity to resist changes in pH. Good buffering capacity can limit dangerous pH swings caused by the introduction of highly acidic or basic substances. Total hardness is defined as the concentration of calcium and magnesium in the water. Calcium is necessary for proper fish egg and fry development. Closely related to alkalinity and pH, sufficient hardness levels can help decrease ammonia and pH toxicity.
Iron – When concentrations exceed 0.1 mg/L, iron precipitates on exposure to air, decreasing pond clarity, potentially clogging irrigation pipes, and encouraging iron bacteria, this affects the flavor of fish and water. Levels greater than 0.3 mg/L can cause staining on buildings and sidewalks when the water is used for irrigation.
pH – The pH value of a body of water expresses its tendency to donate or accept hydrogen ions on a scale of 0 (very acidic) to 14 (very basic). Natural waters generally range from pH 6.5 to pH 8.5 but can vary. Areas with calcium carbonate substrates tend to have higher, or more basic pH levels; such is the case with many Florida ponds and lakes. pH levels can also fluctuate throughout the day in response to respiration rates (which lowers pH) and photosynthesis rates (which increases pH). Any major pH deviations over time for a given water body could indicate the onset of intrusion of strongly acidic or alkaline wastes.
Water with long-term pH readings below 5.5 or above 9.5 can be corrosive, causing potential problems with irrigation equipment or other manmade structures in a water body. When pH is higher we might suspect some marine influence and when pH is lower the water may not have enough buffering capacity. Aquatic animals are greatly affected by changes in pH. An abrupt change of 1 or 2 pH units is enough to mortality in some species. In itself, a pH outside of the desirable range is not necessarily a concern unless the other parameters in the lake suggest problems.
Phosphate – Total phosphorus (TP) refers to all the various forms of phosphorus in the water, while phosphate (PO43-) refers specifically to the dissolved form of phosphorus in the water column. Phosphate is the most biologically active form of phosphorus. Phosphate levels are expected to range from 0.01 to 0.05 mg/L for healthy freshwater systems.
Total Phosphorus – Phosphorus is a naturally occurring component of aquatic systems and it is necessary for a balanced ecosystem. Elevated levels of phosphorus, however, can cause shifts in this balance and is the most common cause of undesirable growth of aquatic weeds and algae. The discharge of treated wastewater and agricultural drainage into a lake will increase a lake’s phosphorus levels. Lawn and landscape fertilizer runoff is another major source of phosphorus in lakes and their use should be avoided near the water. Acceptable range numbers for TP are based on commonly used wastewater guidelines for discharge of treated wastewater. Phosphorus levels above 0.45 mg/L are very high for retention ponds and tend to cause significant algae blooms, but levels this high are not uncommon. When levels are higher than 1.0 mg/L, it is likely that the pond is being exposed to unusual discharges (such as treated wastewater). In such case, multiple management strategies may be required to lower phosphorus levels.
Turbidity – Lack of clarity, known as turbidity, in natural waters is caused by the presence of suspended solids such as silt, clay, fine organic and inorganic matter, plankton and other microscopic organisms. The turbidity test measures an optical property of the water sample and is used as an index of water clarity. Turbidity values of 10 N.T.U.’s (Nephelometric Turbidity Units) or more indicate high levels of suspended solids. Elevated turbidity levels are often due to increased runoff, higher flow, or construction activity in the drainage basin. The degree to which turbidity affects wildlife depends on both the level of turbidity and the duration of exposure. Turbidity levels as low as 5 NTU can begin to stress fish within a few hours.
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