Test system to establish mass balances for 14C-labeled substances in soil-plant-atmosphere systems under field conditions.

A test system has been developed that allows the formation of mass balances for 14 C-labeled organic compounds in soil-plant-atmosphere systems under field conditions. The main focus was the quantification of all different 14 C-labeled gaseous losses from soil and plant surfaces after the application of 14 C-labeled chemicals; therefore, a two-chamber system with specially designed trapping facilities was designed. Volatile 14 C-labeled compounds and 14 CO 2 resulting from the total degradation of the applied 14 C-labeled chemical could be trapped separately, and 14 C gaseous losses from plant and soil surfaces could be determined separately as well. With this test system, it was feasible for the first time to distinguish between 14 C volatile and 14 CO 2 losses from soil surfaces and from plant surfaces in soil monolith systems under real environmental conditions. The system itself was established on surfaces of soil monoliths (lysimeters) to study the above-mentioned processes along with the transport and leaching behavior of the chemicals in soil cores. With the new system, the behavior of organic chemicals was followed up for a whole vegetation period, and a mass balance for the applied chemical was established. Therefore, a better prediction of the long-term behavior of organic chemicals under real environmental climatic conditions was achieved. The first results for the fate of the model herbicide isoproturon in two different types of agricultural soils are presented and compared with results from an extensive laboratory study.