The pH scale measures how acidic or alkaline a substance is, ranging from 0 to 14. A pH of 7 is neutral; values below 7 indicate acidity, and values above 7 signify alkalinity (basicity). Understanding factors that lead to a high pH is important across various environments, including water, soil, and the human body.
Understanding Alkalinity
pH is rooted in the concentration of hydrogen ions (H+) and hydroxide ions (OH-) within a solution. Neutral water contains an equal balance of these ions. A high pH, indicating alkalinity, means a greater concentration of hydroxide ions or a lower concentration of hydrogen ions.
Substances contribute to alkalinity by releasing hydroxide ions or by accepting hydrogen ions. For example, sodium hydroxide dissolves in water, releasing OH- ions and increasing the solution’s pH. The logarithmic nature of the pH scale means each whole number increase represents a tenfold decrease in hydrogen ion concentration, making even small pH shifts significant.
High pH in Water Systems
Elevated pH levels can stem from several factors in various water systems. One common cause is the presence of dissolved minerals, particularly calcium carbonate and magnesium, common in “hard water” sources. These minerals can leach into the water from surrounding rocks and soil, increasing its alkalinity.
Biological processes also play a role in natural water bodies. Photosynthesis carried out by aquatic plants and algae consumes carbon dioxide (CO2) from the water. Since dissolved CO2 forms carbonic acid, its removal leads to a reduction in acidity and a subsequent rise in pH. In managed systems like swimming pools, aeration can also cause CO2 to off-gas, leading to a pH increase.
Furthermore, the addition of chemicals can raise pH. In swimming pools, sanitizers like calcium hypochlorite and liquid chlorine increase pH. Products used to increase total alkalinity, like baking soda (sodium bicarbonate), can also elevate pH. Aquarium decorations, such as limestone or crushed coral, can leach calcium and raise water pH over time.
High pH in the Human Body
Maintaining pH balance within the human body is crucial for physiological function. Normal blood pH ranges between 7.35 and 7.45, indicating it is slightly alkaline. When the body’s pH rises above this range, it leads to alkalosis, which has two forms: respiratory and metabolic.
Respiratory alkalosis occurs when there is a decrease in carbon dioxide levels in the blood. This often results from hyperventilation. Conditions like anxiety, pain, or certain lung diseases can trigger hyperventilation, causing the body to exhale too much CO2. Since CO2 contributes to blood acidity, its excessive removal leads to increased alkalinity.
Metabolic alkalosis, on the other hand, involves an increase in bicarbonate ions or a significant loss of acid from the body. A common cause is severe or prolonged vomiting, which leads to the loss of stomach contents. Certain kidney conditions can also contribute to metabolic alkalosis. Additionally, the overuse of antacids, which contain alkaline compounds, can introduce excess base, leading to an elevated pH.
High pH in Soil
High soil pH impacts plant growth and nutrient availability. A high pH indicates alkaline soil. Natural geological formations contribute to this, especially in areas with bedrock rich in alkaline minerals like limestone. The weathering of these materials releases basic compounds into the soil. Regions with low rainfall and high evaporation are also prone to alkaline soils because salts and carbonates accumulate rather than being leached away.
Human activities can also induce high soil pH. Over-liming, applying too much calcium carbonate (lime), is one cause. While liming is used to raise pH in acidic soils, excessive application can push the pH beyond desired levels.
Irrigation with water that has a high pH or high mineral content can also contribute to soil alkalinity over time, as the minerals accumulate in the soil. Poor drainage can worsen the issue by preventing the leaching of basic salts, leading to their buildup. When soil pH is too high, it can reduce the availability of plant nutrients such as iron, manganese, and phosphorus. This can result in nutrient deficiencies and impact plant health and growth.