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<br />Phytoremediation of selenium
<br />laden soils: A new technology
<br />
<br />G.S. Banuelos, HA Ajwa, N. Terry, and A. Zayed
<br />
<br />ABSTRACT: High concentrations a/soil (Se) are potentially toxic to plams and animals in many
<br />regiort1 0/ the western United Staus. Phytormudiation with diffirent plant species. i.e., Brassica
<br />spp, is an aftanlltive strategy for reducing soi! Se concentrations to non-toxic levels. Se-4cCUmtt-
<br />lIlting plant species which hm't' substantia! ability to absorb, aCCtlmUklte, and volatilize Se have
<br />been slut/ied Ilnd grown on soils to remotle St'. Selenium accwnulated in plant tisme! can then be
<br />Ildrvt'sted and remolled fi'om the contaminated site.
<br />
<br />S clenium (S~) Occurs naturally in many
<br />agricultural soils on the wesc side of
<br />rh< San Joaquin Valley in ccntral Califor-
<br />nia as the result of weathering of Creca-
<br />ceous shales and soils (McNeal and 13al-
<br />iscrieri 1989). Agricultural irrigation of
<br />these alkaline soils concributed (Q the sol-
<br />ubilization of naturally~occurring Se, re-
<br />sulting in high concentracions of Se in
<br />subsurface agricultural drainage wacer
<br />(Fujii ec al. 1988). TiI< drains, ins railed
<br />several meCCts below land surface for salt
<br />managemenc in che soil, diverced these Se-
<br />laden effluencs co sumps chac flow ioco
<br />colleccive drains. In CaJifornia, chis saline
<br />innow from growers in che San Joaquin
<br />Valley was eventually rouced and dis-
<br />charg<d into Kestcrson Narional Wildlife
<br />Refuge from 1981 co 1984 when con.
<br />struction of the San Luis Drainage System
<br />lfor rransporcing effluenr co a delta inlet)
<br />was halted in ceneral California. Conse-
<br />quendy, che weclands receiving irrigation
<br />drainage warer, in the course of being
<br />used as' wildlife habitac, were then operat-
<br />ed as evaporation ponds to concentratc
<br />and reduce the volume of agricultural
<br />wastewater, Deleterious effects on birds
<br />and fish were observed in and around thc
<br />pnnds (Ohlendorf er al. 1986; Presser and
<br />
<br />G.5. Bail/ulo! iJ a plam/Joil Jeien/iIt and H.A.
<br />Ajwa iJ a pONdo((oral auoClal( wirh Agri~'ultural
<br />R~J':.1n'h St:rvia. Us. Depar/nlefl( of AgriCllltllre,
<br />Water Afanagemoj( Reuan'h Laboratory. Fmno.
<br />California, N Tary if a pr()fiJJor and A. Zayed jf
<br />a Pou$x/oral aIJocia/e in the Department of Plam
<br />Biology, Univmity ()fCalifornitl. Berkeley.
<br />
<br />I Soil (wd mlUr Com. 52(6) 426-430
<br />
<br />Ohlendorf 1987), Investigations indicated
<br />that excessively high concentrations of Se
<br />were detecced in both the sediment and
<br />water of Kesterson Reservoir and more
<br />importantly in the biological biota inhab-
<br />iting or frequenting the evaporation
<br />ponds. Alrhough Se ar high concenrra-
<br />dons is presumed to be primarily respon-
<br />sible for disrupting the ecosystem at
<br />Kesterson Reservoir, effective and eco-
<br />nomical technologies for remediadng So:-
<br />laden soils at, this site or other sites or
<br />minimizing movement of soluble Se are
<br />still being investigated. Since the presence
<br />of Se was recognized as an element 'of en~
<br />vironmencal imponance ac high conccn-
<br />trations, its movement has carefully been
<br />monirort:d in at least 10 other sttes in the
<br />western United Scates. These areas include
<br />rhe Tulare Lake Bed Area. California;
<br />Middle Green River Basin, Utah;
<br />Kendrick Reclamation Project Area,
<br />Wyoming; Sun River Basin, Montana;
<br />Stillwarer Wildlife Managemenr Ar<a,
<br />Nevada; Grand Valley Project, Colorado;
<br />and Bdle Fourchc, Sourh Dakota (Eng-
<br />
<br />Interpretive summary
<br />
<br />berg and Sylvester 1993; Presser or "I.
<br />1994).
<br />In central California, Se bioaccumulJ-
<br />cion and the management of chI.: rnllY\:-
<br />rnenc of Se from the soil co agriculturall.:f-
<br />Auene have become primary objt'cti\'l.:s for
<br />state and federal agencies in their <!m:mpr
<br />ro prevenc another "Kesterson dfece" from
<br />occurring. Extensive research on 5e mobili-
<br />ty in Se.laden soils provided rhem wirh
<br />some managemenc options, but mosc were
<br />cosrly and only marginally cff<criv<. Ir was
<br />clear, however, that any approach consid~
<br />ered should include limiting thl.: produc-
<br />cion of effiuenr produced from Sl.:-LiJt:n
<br />soils, which ,can be achieved by improving
<br />water management practices and irrigadon
<br />efficiency practiced in these regions.
<br />The Water Management Research L;\b~
<br />orarory (WMRL) in Fresno, California,
<br />and the Plane Biology Depaitmenc of the
<br />University of California, Berkel~r. t:\'alu-
<br />:Ited, in conjunction with irrigation and
<br />drainage management, an alcernari\'~ ap-
<br />proach for managing Se levels in Se-Iadcn
<br />soils-phytoremediarion, an emerging
<br />technology which is receiving increasing
<br />recognition as a low cost and environ-
<br />mentally.friendly mechod for rhe r<m<di-
<br />acion of other toxic reace e1emenrs (Baker
<br />er al. 1994; Chaney et al. 1994; Ernsr
<br />1988; Kumar er al. 1995; McGrarh or al.
<br />1993; Salr er a!. 1995; Wenczd <, a!.
<br />1993). Both laboratories investigated tht:
<br />possibility chat Se-accumulacor pta.m
<br />species (AstragalUf, Brauica), which have
<br />substantial ability co absorb. accumulate,
<br />and possibly volatilize Se, be grown on St:*
<br />laden soils. The Se accumulated in [heir
<br />planr <issues (up co a 1000 mg So kg'
<br />OM) (ppm) can rhen be harvesred and r<-
<br />moved from the planted site.
<br />
<br />Selenium is a natural-occurring constituent associated with many, soils in the we5t~
<br />side of central California. High concentrations ot selenium found In effluent produced
<br />from these soils led to the death and deformities in waterfowl in the agricultural
<br />ecosystem. Strategies are not readily available for effective reduction of high soil Sa
<br />levels, One alternative strategy recently developed for lowering soil Sa Is phytoreme-
<br />diation, which involves growing selective crops to extract large amounts of Se. Cer-
<br />tain plant species have been proven effective in removing Se from the soil by plant
<br />uptake and/or biological volatilization.
<br />
<br />Key words: phytoremecliation, selenium, volatilization.
<br />
<br />426 jOCHNAL OF SOIL A.'-'O WATER CON'SERVATIO.\;
<br />
<br />Reprinted from 1/'Ie Journal of SOIl a.nd Warer Canserva.llon
<br />November-December 1997 Volume 52 Numb",r 6
<br />
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