Degradation of ethylenethiourea (ETU) in oxic and anoxic sandy aquifers

Abstract

Ethylenethiourea is an important degradation product of ethylenebisdithiocarbamate fungicides, which are widely used in different kinds of crops. The ethylenebisdithiocarbamate group includes maneb, zineb and mancozeb. The ethylenebisdithiocarbamates are not highly toxic and degrade rapidly in the presence of moisture and oxygen, forming different compounds. One of these is the polar ethylenethiourea, which is relatively stable. Thus, this compound appears to be a potential contaminant for groundwater. Batch experiments were carried out under biotic as well as abiotic conditions to study the degradation dependence of concentration, temperature and organic matter. The decomposition of ethylenethiourea under abiotic conditions was found to be less than 5% of the degradation under biotic conditions. Further, ethylenethiourea showed to be stable over a period of 150 days at 20 degrees C in tap water as well as in batch with soil sterilized with NaN3. The degradation of ethylenethiourea depends on the concentration in the water implying first order reaction kinetics. The microbial degradation of ethylenethiourea is highly temperature dependent with aerobic Q10 between 2.9 and 4.2, and an anaerobic between 2.1 and 2.5. A minor increase in degradation rates was observed by application of nitrate and manure to the batches. The experiments show extremely complete degradation of ethylenethiourea in the presence of microbial nitrate reduction with pyrite which occurs in deeper parts of the aquifers.

Kinetics of Maneb Degradation during Thermal Treatment of Tomatoes

“…At the same time, the kinetic studies that have been published so far have investigated the decomposition of disodium EBDC (nabam), a water soluble compound sharing the same ligand with the group of the EBDCs but not actually used as pesticide, in buffers ( − ). Limited information on the degradation kinetics of the manganese and zinc complexes of ethylenebisdithiocarbamic acid (maneb, zineb, mancozeb) is available ( − ), although several efforts are recently devoted to the development of oxidative treatments for the efficient degradation of EBDCs and ETU as a means of decontamination ( − ). Notwithstanding, the results obtained with nabam can be extended qualitatively to other EBDCs.…”

Biodegradation of Pesticides

“…ethylenethiourea, which is relatively stable and is a potential contaminant for groundwater. Experiments conducted under biotic and abiotic conditions, showed complete degradation of ethylenethiourea in the presence of microbial nitrate reduction with pyrite, which occurs in deeper parts of the aquifers (Jacobsen & Bossi, 1997). In general, pesticide-degrading microorganisms are isolated via enrichment cultures.…”

Optimization of a matrix solid-phase dispersion method with subsequent clean-up for the determination of ethylene bisdithiocarbamate residues in almond samples

“…They are generally unstable in the presence of moisture, oxygen and in biological systems [3]. Its main products for hydrolysis and photolysis are ethylenethiourea (ETU) and ethylenebis(isothiocyanate) sulphide (EBIS) and other minority degradation products such as ethyleneurea (EU), which is further degraded to CO 2 under aerobic conditions [4,5] and glycine. ETU and EBIS are considered to be the main responsible for the toxic effects of this pesticide group.…”