PHYTOREMEDIATION n NEW & UNIQUE n EXPLOITS NATURAL PROPENSITIES OF CERTAIN PLANTS TO REMOVE CONTAMINANTS FROM SOIL/WATER n CAN REMOVE ORGANICS & METALS n NEED A MANAGEMENT GUIDE

PHYTOREMEDIATION (cont) n PLANTS CAN METABOLIZE CONTAMINANTS IN SHOOTS OR n RELEASE CHEMICALS THAT CAN REACT WITH THE CONTAMINANT & DIMINISH THE HAZARD. OR n INDIRECT EFFECTS – INTERACTIONS BETWEEN ROOTS, MICROBES & SUBSTRATES ENHANCE MICROBE ACTIVITY WHICH CAN DEGRADE CONTAMINANTS (RHIZOREMEDIATION) n DIRECT & INDIRECT PROCESS CAN OCCUR CONCURRENTLY.

MANAGER SHOULD KNOW WHETHER n UPTAKE & METABOLISM OF CONTAMINANT WILL RESULT IN COMPLETE REMOVAL & DETOX. OR n A TRANSFORMATION PRODUCT HAS ACCUMULATED IN THE PLANT (CAN BE HAZARDOUS). OR n WHETHER PLANT-MICROBE INTERACTION IN ROOTS HAS DEGRADED CONTAMINANT IN THE MATRIX.

NATURE OF CONTAMINANT WILL: n DETERMINE PARTITIONING INTO WATER PHASE (SOLUBILITY) OR LIPID PHASE IN A MATRIX (FAT SOLUBILITY). n LIPOPHILICITY OF A CONTAMINANT CONTROLS ITS AVAILABILITY & TRANSLOCATION IN A PLANT. n MEASURED AS OCTANOL-WATER PARTITION COEF. (K OW ). n K OW – RATIO: CONTAMINANT CONC. IN ORGANIC SOLVENT TO ITS CONC. IN WATER. n LOW K OW = HIGH WATER SOLUBLE COMPOUND n HIGH K OW = HIGH FAT-SOLUBLE COMPOUND

GENERAL RULE: n UPTAKE OF ORGANICS BY PLANT ROOTS INCREASES WITH INCREASING K OW. n FOR TRANSLOCATION – AN OPTIMUM K OW EXISTS. n COMPOUNDS WITH LOW K OW < 10 ARE NOT READILY UPTAKEN BY ROOTS. CAN FLOW AWAY. n IF LOW K OW ENTERS PLANT, ANY TRANSLOCATION IS LIMITED BY LIPID COMPONENTS OF PLANT TISSUES. n HIGH FAT-SOLUBLE COMPOUNDS, K OW >10 3, HAVE LIMITED DELIVERY TO ROOTS DUE TO LOW WATER SOLUBILITIES & HIGH PARTITIONING TO LIPID PHASES IN THE MATRIX. n COMPOUNDS MOST READILY TAKEN UP AND TRANSLOCATED INTO PLANTS HAVE K OW BETWEEN

IMPORTANT FOR MANAGER: n AN OPTIMUM K OW EXISTS FOR TRANSLOCATION OF ORGANICS. n MANY CHEMICALS & PESTICIDES FALL IN THE RANGE FOR UPTAKE & TRANSLOCATION (K OW ). n PCB’S, HYDROCARBONS, DIOXINS HAVE K OW ’s n MOST SUCCESSFUL WHEN FOCUS IS ON STIMULATION OF RHIZOSPHERE BIODEGRADATION INSTEAD OF PROMOTING PLANT UPTAKE & METABOLISM.

PLANT ENZYMES n CAN CAUSE TRANSFORMATIONS WITHIN THE PLANT. n ENZYMES CAN TRANSFORM CONTAMINANTS OUTSIDE THE PLANT (EXPLANTA). n CAN TRANSFORM MUNITION WASTE (TNT) & ORGANIC DEGREASERS (TCE).

ENHANCED MICROBIAL ACTIVITY IN PLANT RHIZOPHERES n CAN SPEED UP ANY TRANSFORMATIONS. n NEED SUITABLE PHYSIOCHEMICAL ENVIRONMENTS. n PLANTS ROOT EXUDATES, I.E. CARBOHYDATES & AMINO ACIDS. ENHANCES GROWTH / BIOACTIVITY OF MICROBIAL COMMUNITIES IN SOIL & PROMOTES DEGRADATION. n BIOFILMS ON ROOT SURFACES (PLANT MUCILAGE) PROMOTES DEVELOPMENT OF MICROBES. MICROBIAL RESPIRATORY ACTIVITY CAN REDUCE O 2 CONC. & CREATE REDUCED ENVIRONMENTS. CAN TRANSFORM HIGHLY CHLORINATED COMPOUNDS.

METALS REMEDIATION POTENTIAL n SOILS CONTAMINATED BY METALS: –MINING –MANUFACTURING –URBAN ACTIVITIES n CAN DISRUPT ECOSYSTEMS n CAUSE HEALTH PROBLEMS n INJURE PLANTS n CAUSE ANIMAL FATALITIES n LEAD PROBLEM – CHILDREN

METALS REMEDIATION POTENTIAL (cont) n EXAMINED TECHNOLOGIES –EXCAVATION –ELECTROCHEMICAL –ENCAPSULATING –PHYSICAL n METALS ARE NOT BIODEGRADABLE. n MICROBIAL PROCESSES OFFER PROMISE. n A MICROBIAL PROCESS INVOLVES OXIDATION-REDUCTION REACTIONS n TRANSFORMS METAL SPECIES FROM SOLUBLE, MOBILE AND MORE TOXIC INTO INSOLUBLE, LESS MOBILE & LESS TOXIC FORM. n THEN SEPARATED BY CHEMICAL/PHYSICAL PROCESS. n EX. REDUCTION OF HAZARDOUS, SOLUBLE Cr 6+ to INSOLUBLE, LESS MOBILE & LESS TOXIC Cr 3+, AND CHEMICAL PRECIP. AS Cr (OH) 3.

HYPERACCUMULATORS: n CERTAIN PLANTS CAN REMOVE METALS FROM MATRICES BY UPTAKE, TRANSLOCATION, & ACCUMULATION IN SHOOTS. n A HYPERACCUMULATOR CAN YIELD GREATER THAN OR EQUAL TO 0.1 % Cr, Ni, Co OR GREATER THAN 1.0% Zn or Mn IN ABOVE GROUND SHOOTS ON A DRY WEIGHT BASIS. n ECONOMIC VALUE - CAN LEAD TO PHYTOMINING/PHYTOEXTRACTION n SOME PLANTS CAN ACCUMULATE UP TO 1% OF BIOMASS FOR Zn, Ni, Co, Mn, Ar.

HYPERACCUMULATORS: (cont) n TREES OFFER ADVANTAGE OF HIGH BIOMASS PRODUCTION. n TREES GENERALLY SLOW GROWING & POTENTIAL FOR LEAF DISPERSION. n GRASSES & CROPS HAVE HIGH GROWTH RATES & SOME HAVE HIGH METAL ACCUMULATION. n WITH LOW BIOMASS PRODUCTION, GRASSES TAKE LONGER TO ACCUMULATE METALS. n CROPS ( HIGH BIOMASS) CAN CREATE A HAZARD TO THE FOOD CHAIN.

HYPERACCUMULATORS: (cont) n MOST STUDIED PLANTS ARE: –FAMILY BRASSICACSAE: –GENERA – BRASSICA & THYLASPI n B. JUNCEA- LEAD, CADMIUM, ZINC n T. CAERULESCENS (ALPINE PENNYCRESS) – ZINC, CADMIUM FAVORED WITH LOWERING THE pH. n LOW GROWTH RATE AND LOW YIELD ARE LIMITING FACTORS. n BIOTECHNOLOGY CAN HELP.

REMOVAL BY PLANT ROOTS n RHIZOFILTRATION - –REMOVES METALS FROM SURFACE & GROUNDWATER BY: ABSORPTION CONCENTRATION PRECIPTATION n TERRESTRIAL PLANTS ARE BEST: –LONG, FIBROUS ROOTS –LARGE SURFACE AREA –EX. CONSTRUCTED WETLANDS SHALLOW LAGOONS GW/WASTE WATER PUMPING

PHYTOSTABILIZATION: n INTERIM CONTAINMENT STRATEGY FOR SITES WITH LOW METAL LEVELS BELOW RISK THRESHOLDS. n LARGE SCALE REMOVAL ACTION NOT FEASIBLE. PLANTS WITH HIGH TOLERANCE FOR METALS IN SOIL & LOW ACCUMULATION. n VIGOROUSLY GROWING & EXERT HYDRAULIC CONTROL OVER TRANSPORT OF METALS.

MATRIX CONTROLS: n PLANT ESTABLISHMENT, PROLIFERATION, & PERFORMANCE. n PH, OXIDATION-REDUCTION. n COMPOSITION & DISTRIBUTION OF REACTIVE SURFACES. n PRESENCE OF MULTIPLE & MIXED CONTAMINATION n INTERACTION WITH CLIMATE FACTORS

CLIMATE – TEMPERATURE n TEMPERATE REGIONS - LIMITED TO WARMER PARTS OF YEAR. n SHORT- TIME AVAILABLE. n OK WHEN NO IMMEDIATE THREAT EXISTS. n WARMING TECHNOLOGIES EXIST/QUESTIONABLE ECONOMIES.

SOIL MATRIX: n MADE UP OF SOIL PHASES n PHYSIOCHEMICAL PROPERTIES OF pH & REDOX. n CAN INFLUENCE MOBILITY. n CAN REGULATE CONTAMINANT EXPOSURE & SUSCEPTIBILITIES TO BIOLOGICAL TRANSFORMATION /REMOVAL PROCESSES. n CONTROL PROCESSES THAT ELIMINATE/REDUCE EFFECTS OF CONTAMINANTS IN ENVIRONMENT. n IMPACT ORGANICS & METALS DIFFERENTLY.

COLLOIDAL NATURE EFFECTS REACTIVITY OF SOIL PHASES (INORGANIC & ORGANIC) n SOIL COLLOIDS ARE: –EXTREMELY SMALL SIZE –LARGE SURFACE AREA –NEGATIVELY CHARGED SURFACE AREA – INFLUENCE ATTRACTIONOR REPULSION BETWEEN SOIL & CONTAMINANT.

ORGANIC PHASE IN SOIL: n HIGH ORGANIC CONTENT IN SOIL n CAN RESULT IN MODERATE TO HIGH LIPOPHILOC ORGANIC TOXICS BEING TRAPPED IN ORGANIC MATTER. n UNAVAILABLE FOR PLANT UPTAKE. n CAN ENHANCE DEGRADATION IN RHIZOPHERES BY STIMULATING MICROBIAL GROWTH & BIOACTIVITY n METALS CAN BOND WITH ORGANICS & REDUCE AVAILABILTY FOR PLANT UPTAKE. n METAL BONDING WITH ORGANICS CAN ASSIST IN SITE STABILIZATION.

ORGANIC PHASE IN SOIL: (cont) n EX. LEAD STABILIZATION n AVAILABILITY OF METALS IN CLAYS WITH HIGH COLLOIDAL SOLIDS WILL BE REDUCED COMPARED WITH SAND SOILS. n BECAUSE: –POSITIVE CHARGED CATIONS OF CONTAMINANTS ATTRACTED TO NEGATIVE CHARGED MINERAL SURFACES. –CHELATING AGENTS ARE BEING RESEARCHED TO IMPROVE METAL AVAILABILITY.

MATRIX (SOIL) pH n EXERTS GREATER IMPACT ON METALS. n PLANTS ABSORB METALS IN IONIC FORM. n METAL CONCENTRATION INCREASES WITH DECREASING pH. (INCREASES HYDROGEN IONS ACTIVITY). n MAY BE TOXIC TO PLANTS. n RESEARCH IS ON ACIDIFIERS. n EX. SULFUR.

OXIDATION-REDUCTION n MANY ELEMENTS ARE MORE MOBILE DEPENDING ON OXIDATION STATE. n EX. CHROMIUM – Cr 6 IS HIGHLY OXIDIZED FORM & IS MORE TOXIC, MORE SOLUBLE & MOBILE THAN Cr 3+ (REDUCED FORM). n PHYTOREMEDIATION MAY FAVOR PRESENCE OF Cr 6. n OTHER REMOVAL SCHEME MAY BE TO REDUCE Cr 6 TO Cr 3 AND PRECIPITATE AS INSOLUBLE, IMMOBILE HYDROXIDE, Cr(OH) 3. n THE CHOICE IS THE MANAGER’S.

DEEP ROOTED PLANTS n EARLY ASSUMPTION THAT PHYTOREMEDIATION DEPTH WAS LIMITED TO CM. n RESEARCHERS ARE DEVELOPING DEEP ROOTED PLANT SYSTEMS. n EX. –HYBRID POPLAR TREES. –GROUNDWATER CONTAINING ATRAZINE AND TNT.

METALS ARE DIFFICULT DUE TO: n LOW SOLUBILITY n ATTRACTION TO SOIL SURFACES n TEND TO REMAIN IN ROOT ZONES

PRESENCE OF OTHER TOXICS n EASILY OVERLOOKED VARIABLE THAT CAN IMPEDE REMEDIATION n MOST CONTAMINATED SITES CONTAIN MIXTURES OF COMPOUNDS (ORGANICS & INORGANICS). n AN EXAUSTIVE CHARCTERIZATION MAY BE REQUIRED FOR DECISION.

MANAGEMENT AIDS n REQUIREMENTS: –POTENTIAL SUCCESS OF TECHNOLOGY –STAKEHOLDER CONCERNS –CAREFUL PLANNING (TEAM OF EXPERT) –SCHEDULING –BUDGETING –IMPLEMENTATION –MONITORING –CONTROLLING

MANAGEMENT AIDS (cont) n PRODUCES EXPECTED RESULTS. n PLANNING: –SITE CONDITIONS –LEGAL REQUIREMENTS –OBJECTIVES & TARGETS n IMPLEMENTATION: –RESPONSIBILITIES/AWARNESS –COMMUNICATION –DOCUMENTATION OF PROCESS n MONITORING: –MEETING OBJECTIVES & TARGETS –ANY CORRECTIVE ACTION

TEAM OF EXPERTS n TECHNICAL EXPERTISE REQUIRED –MICROBIAL BIOLOGY –SOIL SCIENCE/GEOLOGY –HYDROLOGY –PLANT PHYSIOLOGY –PROJECT MANAGEMENT

RECOVERY OF CONTAMINANTS n HARVEST CONTAMINATED PLANTS n LOW GRADE ORE (PHYTOMINING) n RECYCLED n UNDISTURBED ENVIRONMENT

ESTIMATED FINANCIAL RECOVERIES: n HYPERACCUMULATOR PRODUCE TONS BIOMASS/HECTARE/YR WITH VOLUME 10O KG/HECTER/YR (FOR NICKEL, WOULD RECOVER $550/HECTARE AT MARKET VALUE OF $2.50/LB.) n $960/HECTARE WITH ALFALFA PRODUCTION OF 500 KG OF Zn/HECTARE AT $1.92/KG.

ESTIMATED COMPARISON COSTS TECHNOLOGYCOST/TON PHYTOREMEDIATION$25 – 100 ELECTROKINETICS20 – 200 SOIL FLUSHING40 – 190 SOIL WASHING LANDFILLING100 – 400 VITRIFICATION400 – 850

CONCLUSIONS n PHYTOREMEDIATION : –PERMANENT IN-SITU OPTION –PHYTOMINING CAN BE PROFITABLE –MANY PLANTS HAVE ABILITY TO CONCENTRATE CONTAMINANTS IN SHOOTS & LEAVES –DEPENDENT ON CLIMATE, MATRIX, pH, REDOX POTENTIAL, K OW, ORGANIC MATTER. –PLANNING, SCHEDULE, BUDGET, CONTROLS, MONITORING SYSTEM, PROJECT MANAGER, TEAM OF EXPERTS, TOP SUPPORT SUPPORT. –RECYCLING CAN DEFRAY COSTS.