Effects of evaporative salt water cooling towers on salt spray and salt deposition on surrounding soils

Vita.Five salt water cooling towers recently constructed near Galveston Bay, Texas have been shown to contribute to salt deposition in the surrounding area. Levels as high as 1200 kg salt/ha/yr were encountered within 100 m of the towers. Deposition rates decreased in a logarithmic fashion with distance to less than 300 kg salt/ha/yr at 434 m with only 16% attributable to the cooling towers. The remaining deposition was caused by natural sea spray which varys widely but averages about 250 kg salt/ha/yr in the study area. Changes in composition of air-borne salts with distance were noted, primarily as a narrowing of the Na:Ca ratio. The soils in the area adjacent to the salt water cooling towers had safe exchangeable Na and total salt levels. Changes in soil salinity due to the cooling towers after their first two years of operation were found only in the closest study plot at 104 m from the towers. A leaching study indicated that the various ions removed from the soil profile were in the same relative proportions as in the soil solution. Continued operation of the salt water cooling towers will eventually lead to relative cation concentrations in the soil solution equal to those in salts deposited from the cooling towers. Therefore, predictions based on cation-exchange equilibria indicate that exchangeable Na levels greater than 15% will be encountered as far away as 200 m from the cooling towers. This could lead to deterioration of soil physical structure, causing further reduction of the already slow internal drainage, thus enhancing salt accumulation problems. Because of the decrease in the Na:Ca ratio and the total amount of salt deposited with distance from the cooling towers, problems at greater distances will be lower and will require longer to develop