Pesticide Residues in the Environment - Pesticides: Evaluation of Environmental Pollution - page 172

with poultry litter (both the untreated and the γ-irradiated) was the same as that of the
soil+littermixture;nosigniicantconcentrationsoftoxicby-productswereproducedfrom
thebiodegradationofatrazine(GuptaandBaummerIII1996).
Simazine is a chlorotriazine herbicide widely used in agriculture. Simazine may be
hydrolyzed to 2-hydroxy-simazine via both biotic and abiotic processes, which explains
its detection in both sterilized and nonsterilized soils. Urea promoted the formation of
desethyl-simazine.Degradationexperimentswereperformedtoassesswhetherthebio-
degradation of simazine in soil may be inluenced by the presence of urea (Caracciolo
etal.2005).Simazinedegradationratesunderdifferentexperimentalconditions(presence
or absence of urea, microbiologically active/sterilized soil) were assessed together with
formation,degradation,andtransformationofitsmainmetabolitesinsoil.Simazinedeg-
radationwasaffectedbythepresenceofurea,intermsofbothasmallerhalf-life(t 1/2 )and
ahigheramountofthedesethyl-simazineformed.Thesoilbacterialcommunitywasalso
studiedbytheauthors(Caraccioloetal.2005),whoappliedluorescentinsituhybridiza-
tion(FISH)anddetectedallisolatedstrainsasβ-proteobacteria,conirmingtheactiverole
ofthisgroupinsimazinedegradation.Moreover,speciicmolecularprobeshaverecently
beendesigned(Martínez-Íñigoetal.2003),whichtakeintoaccountthesequencedataon
the genes involved in s -triazine catabolism: hydrolytic dechlorination, hydrolytic deam-
ination, and cyanuric acid degradation. The application of these probes by the authors
(Caracciolo et al. 2005) to their soil samples and to isolated pure cultures is in progress
andwillmonitordirectlythepresenceofbacteriathathavespeciicmetaboliccapacities
insomestepsoftriazinedegradation.Caraccioloetal.(2005)suggestthatinsituhybrid-
izationtechniqueisapromisingmethodtodeterminethestructuresandfunctionsofthe
bacterialcommunitiesandmaybeusefultoassess,togetherwiththechemicalanalysis,
the effects of pollutants in the environment. Albarrán et al. (2003) described the effects
of adding an intermediary by-product of olive oil extraction on the sorption, degrada-
tion, and leaching of simazine in a sandy loam soil. Results obtained by these authors
(Albarránetal.2003)showedthatsimazinesorptionisothermsshowedagreatincrease
in herbicide sorption after the addition of solid olive-mill waste (SOMW) to soil; sorp-
tionincreasedwiththeamountofSOMWadded.Incubationstudies(Albarránetal.2003)
showed extended persistence by reduced biodegradation of simazine in soil amended
with SOMW compared with the unamended soil. Although the addition of SOMW to
soil increased the total porosity, breakthrough curves of simazine in hand-packed soil
columns showed that SOMW addition retarded the vertical movement of the herbicide
throughthesoilandreducedthetotalamountofherbicideleached(Albarránetal.2003).
Itappearedthatthelongerresidencetimeofsimazineintheamendedsoilcolumns(>20
days) compared with that in the unamended soil column (<20 days) allowed enhanced
degradationand/orirreversiblesorptionundercolumn-leachingconditions(Albarránetal.
2003).ResultsdescribedbytheseauthorsindicatethatSOMWapplicationtoagricultural
landislikelytoincreasetheresidencetimeofsimazineinthetopsoilbyenhancingsorp-
tionandreducingleachinganddegradationlosses.FragoeiroandMagan(2005)examined
the extracellular enzymatic activity of two white-rot fungi ( Phanerochaete chrysosporium
and Trametes versicolor )inasoilextractbrothinrelationtodifferentconcentrations(0-30
ppm)ofsimazineandpesticidesfromothergroups(dieldrin-cyclodieneinsecticideand
triluralin-dinitroanilineherbicide)underdifferentosmoticstress(−0.7and−2.8MPa)and
quantiiedenzymeproduction,relevanttoPandNrelease(phosphomonoesterase,prote-
ase),carboncycling(β-glucosidase,cellulase),andlaccaseactivityinvolvedinlignindeg-
radation.ResultsobtainedbyFragoeiroandMagan(2005)suggestthat Trametes versicolor
and Phanerochaete chrysosporium havetheabilitytodegradedifferentgroupsofpesticides,