Looking for ways to limit radiation damage to farm land. Scientists say topsoil could be be stripped, turned over, or treated
While the extent of radiation damage to Soviet agriculture is not yet known, scientists say some actions can be taken to reduce the impact of radiation fallout on crops and pasturage. ``You have two basic options with contaminated land. You can either peel it off or plow it under,'' says James E. Newman, a climatologist at Purdue University who has studied radioactive fallout. ``The land closest to the reactor will simply have to be taken out of production.''
Each option carries its own problems. Peeling the top of the soil off the land poses a disposal problem. The resulting storage and nuclear waste management needs would be enormous.
Deep plowing land takes the top 18 to 20 inches of soil and turns it upside down. Since the majority of crops have root structures that go no deeper than 8 to 12 inches, deep plowing can reduce the amount of contaminants that could be absorbed by the plants.
According to Dr. Newman, the application of potasium fertilizer with calcium compounds would also reduce the amount of contaminants (strontium and cesium) absorbed by the plants.
All three procedures are extremely energy intensive and might not be possible considering the amount of acreage covered by the plume. Which corrective measures, if any, are chosen will depend on the amount of fallout from the accident.
Boris Yeltsin, the Moscow Communist Party chief, said over the weekend that the reactor blaze had been extinguished and that the accident was unlikely to seriously affect Soviet agriculture.
US officials forming an interagency task force on the accident estimated on Friday that land within a three-mile radius of the plant would be exposed to lethal levels of radiation. Land within a seven-mile radius would have extremely dangerous levels, they said.
``The amount of deposition [fall-out] depends on three factors: particle size, length of exposure, and meteorological conditions such as amount of rain fall, wind speed, and direction,'' according to Philip Gustafson of Argonne National Laboratory near Chicago.
Initially, winds from the south were pushing the radioactive plume from the Chernobyl reactor northward, away from the mature winter wheat crop. Due to the colder climate, crop land in the north has not been planted and is therefore less vulnerable to contamination.
US government meteorologists reported late last week that the winds were moving southward. As of Sunday, they were headed eastward.
The southern wind shift might compound the problem for the Soviets and other East and West European countries, especially those that depend a great deal on export cash crops to keep their economy going. Last Friday Italy banned the sale of leafy vegetables and advised against the consumption of milk by children. Other countries have suggested washing radiation-exposed vegetables.
``There has been quite a bit of testing on the effects of nuclear fallout on animals and agriculture in the US,'' commented Argonne scientist Gustafson, ``especially in the late 1950s and early 1960s centering around the testing of radioactive weapons in the atmosphere.''
Some components of the radioactive plume have been determined from air samples, and others can be determined from the plant design and fuel type.
Of primary concern are: barium 140, iodine 131, cesium 137, and strontium 90. All of these elements emit radiation which can cause changes in human and animal cells. They are ``active'' for various lengths of time, refered to as their ``half-life.'' The first two substances, barium and iodine, have relatively short half-lives of less than two weeks. Strontium and cesium, however, have half-lives of approximately 30 years.
Once contaminants are deposited on pasture land they move quickly through the cattle and into the milk. Dairy cattle have traditionally been used as a sampling mechanism for air pollutants since the results are so immediate and samples can be taken daily.
``Basically, if you can keep the cattle off pasturage and feed them with uncontaminated forage, the problem with barium and iodine will pass in a few weeks,'' says Dr. Gustafson. ``The situation with longer half-life substances is a different story. Strontium and cesium will be present for a much longer time, depending on the level of contamination.''