Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 +/- 0.001 to 0.106 +/- 0.003 day(-1) were obtained at different initial concentration ranging from 10 to 230 microM. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 x 10(2) to 0.15 day with the increasing temperature from 4 +/- 0.8 to 60 +/- 1 degrees C. The presence of Ca(2+) made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 +/- 0.06 day(-1), which is comparable to that of hydrolysis at 60 degrees C. The presence of Ca(2+) accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca(2+). The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment.

Estrogenic hormones are endocrine-disrupting compounds, which disrupt the endocrine system function of animals and humans by mimicking and/or antagonizing endogenous hormones. With the application of sludge biosolid and animal manure as alternative fertilizers in agricultural lands, estrogens enter the soil and become an environmental concern. The degradation kinetics of 17beta-estradiol, an estrogenic hormone of major concern, in a silt loam soil were investigated in this study. It was found that 17beta-estradiol degraded rapidly in nonsterilized soil with a half-life of 0.17 day. The degradation rate constant was proportional to the percentage of nonsterilized soil, indicating that microorganisms are directly responsible for the rapid degradation of 17beta-estradiol in soil. The half-life of 17beta-estradiol in 20% nonsterilized soil was slightly shortened from 1.3 to 0.69 day with the increase of soil moisture from 10 to 20% and was greatly decreased from 4.9 to 0.92 day with the increase of temperature from 15 to 25 degrees C. The coexistence of 40 micromol kg (-1) sulfadimethoxine, a veterinary antibiotic, decreased the degradation rate constant of 17beta-estradiol from 0.750 +/- 0.038 to 0.492 +/- 0.016 day (-1). The degradation kinetics of another three estrogenic hormones, including 17alpha-estradiol, estrone, and estriol, were also investigated and compared. Estrone was identified as a degradation product of 17beta-estradiol and the most persistent hormone among the four investigated estrogens. Estriol was observed in the degradation of estrone and 17alpha-estradiol.

A flexible and convenient approach was developed for the synthesis of 10-deoxymethynolide (1) and narbonolide (2), which are aglycones of the methymycin and the pikromycin families of macrolide antibiotics. These lactones are produced by pikromycin polyketide synthase from Streptomyces venezuelae. Polyketide lactones, 10-deoxymethynolide and narbonolide, which contain 12- and 14-membered rings, respectively, were synthesized efficiently. These target lactones were retrosynthetically divided into three parts and assembled by using an asymmetric aldol reaction, the Yamaguchi esterification, and ring-closing metathesis. The ring-closing metathesis reaction catalyzed by the second-generation Grubbs catalyst is particularly efficient in preparing these macrocyclic polyketide lactones.

With the increased use of the agricultural fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP), it is important that strategies to reduce emissions of these fumigant from soil to the air are assessed to protect air quality. Using an established soil column approach, the following emission reduction strategies were compared to a control: (1) spray application of ammonium thiosulfate to the soil surface; (2) deep injection at 46 cm depth; (3) high density polyethylene sealed over the soil surface; (4) virtually impermeable film sealed over the soil surface; and (5) irrigation with ammonium thiosulfate solution. Relative to the control, 1,3-D emissions were reduced by 26.1, 1.0, 0.01, 94.2, and 42.5%, for treatments 1 through 5, respectively. For CP the reductions were 41.6, 23.3, 94.6, 99.9, and 87.5% for treatments 1 through 5, respectively. Virtually impermeable film gave the greatest reductions for both fumigants, while HDPE was very effective only for CP. Despite offering less significant emission reductions, the lower cost alternatives to tarping, particularly irrigation with ATS solution, may offer substantial benefitwhere tarping is not economically viable.