On average, pH rose from 5.88 to 6.56 after liming. Only in The consequences of liming on water chemistry are presented in terms both of the primary changes in pH, calcium and alkalinity and of secondary effects such as the impact on levels of organic materials, nutrients and trace metals. Data for the evaluation have mainly been drawn from the liming data base (KRUT), which is maintained by Swedish county councils and the Swedish Environmental Protection Agency. The condition of limed waters in Sweden and the changes which are taking place in these waters can be described in objective terms and subjected to international comparison.a few cases did the pH exceed 7.5. Overdoses raised the alkalinity to levels above 0.3 meq/1 in 230 lakes. Calcium concentrations increased by 0.22 meq/1 (median value). The median duration of the liming effect for pH in excess of 6.0 was 1.7 years, which corresponds to 2.5 hydrological turnovers. The efficiency of lake liming measures has been evaluated by calculating the transport of calcium on the basis of decay curves and then comparing the results with the dosage. The median value for lake-liming efficiency was 63%.Secondary changes are dependent upon the extent of the treatment and the condition of the water at the time of liming. Water with a high colour value becomes lighter, while lower colour values can involve either an increase or a decrease. Lake liming alone does not result in any improved nutrient status and there is a strong risk that the liming measures which have been undertaken will have no effect. Aluminium concentrations decline in conjunction with liming, a change which depends on the final pH and the level of organic materials. In water with a high level of organic materials, there is little change in the total concentration, but there is a shift fromt toxic forms to more tightly bound and less toxic forms after liming.There are indications of a decrease in the concentrations of iron and manganese after liming. As a rule, levels of other trace metal decline.Effective liming of watercourse can be achieved using dosers or by upstream liming. The dosers cannot provide any security against acid surges when they are out of action, however.Acid deposition affects soil processes so that the composition of the runoff changes. This means that the pre-acidification condition of lakes or watercourses cannot be restored by liming. If this is to be achieved, soil liming in the catchment area must be performed at least once. Soil liming in the discharge zone (wetlands) is more effective that in drier land, but the duration is short — approximately one year — and lake liming has a greater effect. Secondary effects such as reduced aluminium leaching and, to some extent, increased leaching of nutrients, may contribute to lake restoration.A research programme which provides greater insight into the different processes and the links between chemical, biochemical and biological changes is essential if we are to gain a better understanding of the limed ecosystem and establish a platform for future treatment.The objectives of liming are being achieved to a greater extent today than they were ten years ago. Treatment has become more organized so that entire water systems can be covered, rather than individual waters with short turnover periods are being covered than ten years ago.
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- The effects of liming on water chemistry
- Springer Berlin Heidelberg
- Chapter 5