Nitrate

Nitrate is an essential nutrient, the most common chemical contaminant of groundwater, a good indicator of contamination from human activities, and can be found in groundwater and freshwater from natural and anthropogenic sources. Sources include manures, inorganic fertilizer and on-site sewage disposal systems.

Canadian drinking water standard is set at 10 mg/L of nitrogen as nitrate (NO3 -N) due to human health concerns. Levels of 4 to 5 mg/L or higher are considered harmful to aquatic organisms.

Recent studies in the Salmon River watershed by Westwater Research and students have focussed on nitrate monitoring to demonstrate the extent of movement of water from surface to groundwater and vice versa.

Phosphorus

Phosphorus is an essential nutrient present in soil and water in inorganic and organic forms. Although phosphorus can be a limiting nutrient in freshwater, excessive loadings contribute to algal blooms and eutrophication. Sources can include urban/industrial wastewater and applied soil nutrients such as inorganic fertilizer, manure or sewage sludge. Manure applications based on nitrogen requirements can result in excessive phosphorus application and the potential for runoff.

Past Salmon River studies indicate that levels in the last 20 years are usually below 0.06 mg/L with the higher levels usually in winter when lower temperatures inhibit algal growth. These levels do not appear to contribute to eutrophication. Some areas, below Greater Vancouver Zoological, an area at 56^th bridge, in and below Union Creek, have recorded levels above the 0.1 mg/L recommended for rivers.

Turbidity

Turbidity is a measurement of the cloudiness (light scattering and light absorption) caused by sediment, microscopic organisms, and pollutants. These suspended particles restrict light penetration in the water, which in turn affects algal growth and oxygen production. Sediment can clog gills or other breathing structures of fish and benthic invertebrates. When sediment settles to the stream bottom, it can smother fish eggs and ruin habitat used by fish and aquatic insects.

Some waters are naturally turbid and their communities have adapted to these conditions. Turbidity is high in streams that drain glaciers and streams in geologically young areas.

Turbidity normally increases during and after rain storms or rapid snow melt. Severe problems with turbidity occur in areas where urban development, logging, and agriculture have disturbed the watershed and caused erosion. You can assess the extent of the problem by comparing turbidity before, during, and after times of heavy runoff. You also can compare turbidity upstream and downstream of suspected point sources of pollution.

Turbidity is reported in Nephelometric Turbidity Units (NTU) or in Jackson Turbidity Units (JTU). Both units are equivalent. It is impractical to assign a range of values to turbidity, however, non-detectable turbidity may be approximated by pure distilled water (zero NTU). Values exceeding 1000 NTU may be observed in wastewaters; waters with very high natural turbidity may be in the range of several hundred NTU.

Specific Conductance

Specific conductance (conductivity) is a numerical expression of a water’s ability to conduct an electrical current. It is measured in microsiemens per centimetre (m S/cm) corrected to a standard temperature, usually 25° C. the conductivity of water is dependent on the concentration of dissolved salts and temperature.

Specific conductance provides a good indication of the changes in a water’s composition, especially in its mineral concentration. It is particularly sensitive to variations of dissolved solids, but provides no indication of the relative quantities of the various components. As more dissolved solids are added, the water’s specific conductivity increases. An empirical relationship exists between specific conductance and total dissolved solids; specific conductance multiplied by 0.65 closely approximates total dissolved solids, although this relationship should be derived empirically for each site.

Specific conductance in natural surface waters has been found to range from 50 to 150 m S/cm. Ground water and water in arid regions usually has elevated specific conductance. The conductivity of arid waters is typically 1,000 m S/cm. Industrial wastes can elevate specific conductance of receiving waters to 10,000 m S/cm. No guidelines have been established to regulate specific conductance since the high values are found to correlate with total dissolved solids, which have outlined objectives. Values of high specific conductance reflect the presence of high concentrations of total dissolved solids. (See the section "Total Dissolved Solids".)

Total Dissolved Solids

Total Dissolved Solids (TDS) is an index of the amount of dissolved substances in water. The presence of such solutes alters the physical and chemical properties of water. The base flow of a waterway acquires mineral constituents in the form of dissolved salts in solution, such as sodium, chloride, magnesium, sulphate, etc. In periods of high surface runoff, overland flow contributes dissolved materials to waters. In addition, significant contributions to the TDS load are anthropogenic in the form of municipal and industrial effluents, agricultural runoff, and aerosol fallout.

Basic guidelines on the concentration of TDS which have been established relate to taste and palatability rather than to detrimental health effects on human and aquatic biota. TDS concentrations of 500 mg/L or less have been designated as an objective level for drinking water providing none of the individual dissolved constituents exceed their particular guidelines. If the TDS concentration exceeds 2,000 mg/L laxative effects have been observed in humans. A similar laxative effect has been shown in livestock. For animals, concentrations less than 2,500 mg/L have proven to be satisfactory in most circumstances.

. Acknowledgements

Information on indicators of water quality and parameters has been extracted or summarized from: