why anions (meq/L) = cations (meq/L) = approx EC/10 (mS/m)?
How to understand the conversion,why 1/10?
Answers
Answer:
Explanation:
salinity is measured by electrical conductivity (EC) using a conductivity bridge. The total salt content of a soil can be estimated from this measurement. A more precise method involves evaporation of the aqueous extract and weighing the residue (total dissolved solids, TDS).
EC(dS/m)*640=TDS(mg/l) (Accuracy -+10)
in water the TSS is a well-mixed sample is filtered through a weighed standard glass-fiber filteand the residue retained on the filter is dried to a constant weight at 103 to 105°C. The increase in weight of the filter represents the total suspended solids. To obtain an estimate of total suspended solids, calculate the difference between total dissolved solids and total solids.
while ‘Dissolved solids’’ is the portion of solids that passes through a filter of 2.0 µm (or smaller) nominal pore size under specified conditions. ‘‘Suspended solids’’ is the portion retained on the filter.
Sum concentrations (in milligrams per liter) of constituents to calculate the total dissolved solids are as follows: Total dissolved solids = 0.6 (alkalinity*#(2)) + Na+ + K+ + Ca2+ + Mg2+ + Cl−+ SO42− + SiO32− + NO3− + F−
Both the anion and cation sums should be 1/100 of the measured EC value. If either of the two sums does not meet this criterion, that sum is suspect; reanalyze the sample. The acceptable criteria are as follows: 100 × anion (or cation) sum, meq/L = (0.9–1.1) EC
If the ratio of calculated TDS to conductivity falls below 0.55, the lower ion sum is suspect; reanalyze it. If the ratio is above 0.7, the higher ion sum is suspect; reanalyze it. If reanalysis causes no change in the lower ion sum, an unmeasured constituent, such as ammonia or nitrite, may be present at a significant concentration. If poorly dissociated calcium and sulfate ions are present, the TDS may be as high as 0.8 times the EC. The acceptable criterion is as follows: calculated TDS/conductivity = 0.55–0.7
The acceptable criteria for this ratio are from 0.55 to 0.7. If the ratio of TDS to EC is outside these limits, measured TDS or measured conductivity is suspect; reanalyze.