The fate of 14C-labeled sulfadiazine (SDZ) in manured soil has been investigated in laboratory test systems. In the first approach, stability of 14C-SDZ in liquid bovine manure has been tested. Only 1% of the initially applied radiotracer was mineralized to 14C-carbon dioxide and 82% were transferred to nonextractable residues within a 102-d incubation period. Test slurries with defined aged residues were prepared and, supplementary to standard solutions, applied to silty-clay soil samples. These tests showed the high affinity of 14C-SDZ residues to the soil matrix. In the second approach, basic data on microbial, chemical, and photoinduced degradability in soil were gathered. The data indicated the formation of nonextractable residues as the predominant process in soil, which was accelerated by the test slurry application. In the third approach, laboratory lysimeter tests were conducted to investigate leaching and degradation as simultaneously occurring processes. The 14C-SDZ residues (64%) mainly were retained in the surface layer as nonextractable residues. Although a high mobility in soil was revealed by a soil/water distribution coefficient of 2 L kg(-1), percolate contamination amounted to only 3% of the initially applied 14C-SDZ. The tendencies of leaching and degradability in soil also were observed in test plot studies under field conditions.

Three test-plot series have been performed to gather information on runoff of sulfonamides from manured arable and grassland after sprinkler irrigation. To prepare test slurries with defined aged residues, liquid bovine manure was fortified with sulfadiazine, sulfadimidine, and sulfamethoxazole and stored short-term. After test-slurry application, the arable land was treated by soil cultivation before irrigation, and the manured grassland was irrigated directly with 50 mm h(-1) for 2 h. The runoff suspensions were sampled at 5- to 10-min intervals, separated into aqueous phase and suspended matter and residue analyzed. Higher runoff emissions were found from manured grassland plots. The discharge volumes ranged from 106 to 252 L and the total runoff emissions ranged from 13 to 28% of sulfonamides applied initially. Within the first 20 min of the irrigation period that represented a rainfall of 17 mm, emissions, on average, were 4%. The loads of sulfonamides predominantly occurred in the runoff water. The only emissions via suspended matter, on average, were 0.02%. On arable land, however, the runoff was reduced by soil cultivation. Discharge volumes and sulfonamide emissions were 36 to 128 L and 0.1 to 2.5%, respectively. Despite the high-intensity sprinkler irrigation, major emissions did not occur until a 60-min delay.

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The fate of 14 C-labeled sulfamethoxazole and acetyl-sulfamethoxazole in soil has been investigated with special respect to possible entry routes of human and veterinary pharmaceuticals into soil environments. Therefore, the stability of the test substances was monitored first in sewage sludge and bovine manure. Within the incubation period of 72 d, 1% at maximum of the initially applied radiotracers was released as 14 C-carbon dioxide while F75% was transferred to non-extractable residues that were operationally defined by the ethyl acetate extraction. Test-sludge and test-manure samples with defined aged residues were prepared and, supplementary to standard solutions, applied to silty-clay soil samples. After standard and test-sludge application, soil/water distribution coefficients of K d a 5 L kg -1 were determined revealing both test substances as potential leachers. In contrast, the sorption of sulfamethoxazole increased after test-manure application (K d A 10 L kg -1 ). In the long-term degradability tests, the metabolic fate of both test substances was characterized by the continuous decrease of extractable residues, resulting in disappearance times of DT 90 f 33 d, and the increase of non-extractable residues. Mineralization reached 11% at maximum. Thereby, the dynamics of these processes differed whether the test substances were applied via standard, test-sludge or test-manure application. This fact emphasized the relevance of entry route specific matrix effects on the fate of both test substances in soil.

Due to the high use of antibiotics and antiparasitics for the treatment of livestock, there is concern about the potential impacts of the release of these compounds into freshwater ecosystems. In this context, the present study quantified the acute toxicity of two antibiotics (sulfadiazine and sulfadimidine), and three antiparasitic agents (flubendazole, fenbendazole, ivermectin) for nine freshwater invertebrate species. These experiments revealed a low degree of toxicity for the sulfonamide antibiotics, with limited implications in the survival of all test species at the highest test concentrations (50 and 100 mg/L). In contrast, all three antiparasitic agents indicated on the basis of their acute toxicity risks for the aquatic environment. Moreover, chronic toxicity data from the literature for antiparasitics, including effects on reproduction in daphnids, support the concern about the integrity of aquatic ecosystems posed by releases of these compounds. Thus, these pharmaceuticals warrant further careful consideration by environmental risk managers.

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The fate of flubendazole and fenbendazole in manure and manured soils was investigated under laboratory and field conditions. In pig manure, both 14 C-labeled benzimidazoles disappeared slowly. After a 102 day incubation period, extractable fractions contained 72% flubendazole or 80% fenbendazole of the radioactivity initially applied. The latter was accompanied by 4% of the corresponding metabolite fenbendazole-sulfoxide. Non-extractable residues amounted to 24 and 13%, respectively. On this basis, test manures with 7 day aged benzimidazole residues were prepared. Mobility tendencies differed for clay and sand soils as well as for standard and test-manure application. Regarding K OC A 1100 L/kg, however, criteria for potential leachers were not fulfilled. The metabolic fate of flubendazole was predominated by the occurrence of the parent compound while fenbendazole was accompanied by fenbendazole-sulfoxide. In clay soil samples after standard application, DT 50 values were 174 and 54 days, respectively. Mineralization and formation of non-extractable residues were of minor relevance. For fenbendazole, these processes were intensified after test-manure application. Due to enhanced formation of fenbendazole-sulfoxide, fenbendazolesulfone, and non-extractable residues, DT 50 thus dropped to 9 days. Similar mobility and degradability tendencies were also found under field conditions. In the sand soil, however, the metabolic dynamics decelerated due to its lower microbial activity.

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