Environmental Engineering Reference
In-Depth Information
(Singh2008).Leachinglossesofmetribuzinweredrasticallyreducedfrom93%incontrol
soil(T-0)to65%(T-1)and31%(T-2)inbiocompost-amendedsoils(Singh2008).Biocompost
from sugarcane distillery efluent can be used effectively to reduce downward mobility
of metribuzin in low-organic-matter sandy loam soil (Singh 2008). Bending et al. (2002)
described degradation of contrasting pesticides by white-rot fungi and its relationship
withligninolyticpotential.Therewasconsiderablevariationamongthewhite-rotfungiin
theirabilitytodegradethepesticides.Moreover,therewerenorelationshipsbetweenpre-
sumptiveligninolyticactivityandthedegradationofanyofthepesticides(e.g.,chlorotri-
azine herbicides: atrazine and terbuthylazine; phenylurea herbicides: diuron). The three
membersofthePolyporaceaeusedinBendingetal.(2002)studyshoweddifferencesinthe
extenttowhichtheywereabletodegradethepesticides,with Coriolus versicolor showing
strongdegradativeabilitiesand Dichomitus squalens and Pleurotus ostreatus havinglimited
degradativepotential.When Coriolus versicolor , Hypholoma fasciculare ,and Stereum hirsutum
weregrowninbiobedmatrix,theywereallabletodegradethepesticides,althoughthere
were differences in the relative degradative capacities of the fungi in liquid and biobed
media(Bendingetal.2002).
6.4.4.3  Phenylurea Herbicides
Phenylureasareimportantherbicidesandareusedworldwidetocontrolweedsinvari-
ouscrops.Ratesofdegradationofphenylureaherbicides(isoproturonanddiuron)and
triazinylsulfonylureaherbicides(metsulfuron-methyl)weremeasuredintwosoilsincu-
batedattwotemperatures(5°Cand25°C)withsoilmoistureatametricpotential−5kPa
(WalkerandJurando-Exposito1998).Withisoproturonanddiuron,thechangesintime
weresimilaratthetwoincubationtemperatures.Thisindicatesthattheapparentchanges
intheadsorptionwiththesetwocompoundswerenotcausedbypreferentialdegrada-
tioninthesoilsolution,butbyaslowequilibrationwiththeadsorptionsites(Walkerand
Jurando-Exposito1998).TheresultsobtainedbyWalkerandJurando-Exposito(1998)with
theweaklyadsorbedherbicides,metsulfuron-methyl,however,suggestedthepossibility
of preferential degradation in the solution phase because, when degradation was slow,
the absolute amounts adsorbed remained constant or increased slightly, even although
solution concentrations declined. Saison et al. (2010) applied 3-(3,4-dichlorophenyl)-1,1-
dimethylurea( 14 C-diuron)tothesoilsurfacetotraceitsresiduesinwater-extractable(W),
methanol-only-extractable(MO),andnonextractable(N)fractionsandinrunoffwaters.
Mass-balance calculations were itted to the observed data to determine the quantities
degradedortransferredwithinandbetweeneachofthecompartmentsstudiedbySaison
etal.(2010).Schematicmodelusedforthecalculationofdegradationandtransfersinand
betweensoilfractionsispresentedin Figure6.7 (Saisonetal.2010).Theauthors(Saison
etal.2010)consideredthefollowingmass-balanceapproach,whichdifferentiatesseveral
compartments (Figure 6.7): W, water-extractable fraction in the 0-2 cm soil layer; MO,
methanol-only-extractable fraction in the 0-2 cm soil layer; N, nonextractable fraction
inthe0-2cmsoillayer;M,methanol-extractablefractioninthe2-6cmsoillayer;andR,
fractionlostinrunoff(Saisonetal.2010).Pesceetal.(2009)describedastudythatpro-
videsastrongsuggestiveevidenceforhighdiuronbiodegradationpotentialthroughout
its course, from the pollution source to the inal receiving hydrosystem, and suggests
that, after microbial adaptation, grass strips may represent an effective environmental
tool for mineralization and attenuation of the intercepted pesticides (Pesce et al. 2009).
Degradation of phenylurea herbicide isoproturon and herbicide bentazon in peat- and
compost-based biomixtures was described by Coppola et al. (2011). Compost-based
Search WWH ::




Custom Search