Vol15-2-6_Maquetación 1
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1. S nchez et l At 45 DAE the highest plant cover 455 6 cm was found at site 2 P lt 0 05 At 60 DAE linear contrasts 3 4 and 6 showed significant differences P lt 0 05 with plant cover on plot 2 being higher 803 3 cm than the mean value of the other three sites 498 2 cm At 75 DAE sites 2 and 3 showed the highest values 1150 and 955 cm compared to 667 cm2 for site 1 P lt 0 05 At 90 and 105 DAE there were not significant differences in plant cover among sites Plant cover values for plant species are shown in Table 4 average of 20 observations At 45 DAE A pintoi had a higher plant cover than L virginicum P lt 0 05 which could be associated to the A pintoi initial biomass being greater than that of the other studied species At 60 and 75 DAE linear contrasts showed no significant differences between local and introduced species but at 60 DAE B pilosa had higher plant cover 685 cm than L virginicum P lt 0 05 At 90 and 105 DAE B pilosa continued to show higher plant cover than L virginicum P lt 0 05 Days after establishment L virginicum B pilosa A pintoi Linear contrasts 3 l 60 L virginicum vs B pilosa A 90 1132 4b 2062 6a 1662 6ab 105 1271 6b 2068 8a 1706 5ab Table 4 Plant cover cm as average among four plant species Means with different letters are significantly different from each other P lt 0 05 according to the Duncan test In general plants growing on sites not2. decumbens to 68 47 B pilosa g m at 60 DAE and from 112 8 L virginicum a 357 9 B decumbens at 105 DD Although no significant differences were observed sites or species B decumbens DM production was higher indicating that this Poaceae is a promising alternative for rehabilitation processes due to its vigorous DM production Biomass accumulation by B pilosa and especially L virginicum was not favored by plant structure given their smaller foliar area as compared to B decumbens which grew erect with numerous and vigorous stems Additionally a severe attack of Lepidoptera larvae reduced the biomass production in L virginicum growing in site 3 and although plants recovered from this attack their biomass production was clearly reduced It is clear that DM production strongly affects both HM extraction and the efficiency of the phytoremediation process Plant heavy metal content and extraction Values of HM content mg kg HM plant extraction mg plant and HM extraction mg m all calculated on a dry matter basis 282 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l HM Extraction mg m HM Plant Extraction mg plant HM content mg kg e a Tw Ja pma iara 2 majos foo 09020 19 ma L virginicum Days after establishment Table 7 Dry matter production g m HM conten
3. significant differences between local B pilosa and L virginicum and introduced plant species B decumbens and A pintoi during the period evaluated Judging by plant cover and height all plant species studied showed adequate adaptation Acta biol Colomb Vol 15 N 2 2010 281 Days after establishment Moravia plots Linear contrasts 145 Natives vs Clay High slope vs Flat 2 3 vs 1 Ts 3 y 2 vs 20 Natives vs Clay High slope vs Flat 2 3 vs 1 2 vs 2c High slope vs Flat 2 3 vs 1 1 vs 3 High slope 2 vs 3 LVS 38 2 vs 2c 105 72 3 59 7 65 5 65 6 Natives vs Clay 1 3 vs 2 native 2 clay 60 75 90 Days after establishment L virginicum B pilosa B decumbens Linear contrasts E 60 L virginicum vs B pilosa EE 90 L virginicum vs B pilosa 105 42 70 85 05 69 60 L virginicum vs B pilosa Table 6 Plant height cm observed as average among four plant species P lt 0 05 P lt 0 01 to the Moravia conditions suggesting all these four species could be successfully used in the revegetation process needed at Moravia However based on plant height and cover B pilosa appears to be the most promising plant species Dry matter production Values of DM production g m are presented in Table 7 Plant DM production increased throughout the evaluation period in all plant species with mean values among plant species going from 22 77 B
4. DAE At each sampling time five individuals per plot were randomly selected Plant height was measured in cm by straightening individuals to their fullest length Due to the prostrate growth habit of the species A pintoi this variable was not recorded in A pintoi plots Plant cover of A pintoi B pilosa and L virginicum was measured in cm as the surface projection area of each individual plant according to Steubing et al 2001 Plant cover of B decumbens was evaluated by means of visual scale on the four plots Visual observations for signs of phytotoxicity disease and attack of plagues were also carried out at the same sampling times Production of dry matter DM in plant species was determined at 60 and 105 DAE Briefly the roots and aerial tissues of two randomly chosen plants per plot were 276 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l collected taken to the laboratory and gently washed with tap water Tissues were dried 60 C up to constant weight and DM production estimated as g m HEAVY METAL CONTENT IN RESIDUE MATRIX AND PLANT SAMPLES Total content of Pb Cr and Ni on the RM was determined before planting and when planted species reached 60 and 105 days after establishment DAE In each plot samples of the RM top layer 0 20 cm were collected and transported to the laboratory where large size fragment
5. de metales pesados MP creando la necesidad de conducir procesos de restauraci n en dichos lugares En el Morro de basuras de Moravia con 7 6 ha y 45 m de altura conformado por la disposici n de los residuos s lidos de la ciudad de Medell n entre 1974 y 1984 estudios anteriores demostraron alto contenido MP evidenciando la necesidad de identificar mecanismos efectivos para su restauraci n El objetivo de este estudio fue evaluar la adaptaci n crecimiento y capaci dad fitorremediadora de Bidens pilosa Lepidium virginicum Brachiaria decumbens y Arachis pintoi El contenido de MP mg kg en la matriz de residuos de Moravia vari entre 17 y 8 193 para Pb 44 a 564 para Cr 0 2 a 339 para Cd y 77 a 1 679 para Ni Las mediciones de cobertura altura y producci n de materia seca mostraron que todas las especies evaluadas tuvieron un nivel adecuado de adaptaci n y crecimiento a las condiciones del basurero de Moravia La absorci n de MP present el orden Cr gt Cd gt Ni gt Pb Los factores de bioconcentraci n estimados fueron bajos siendo los valores m ximos 0 36 A pintoi Cr 2 96 B pilosa Cd y 0 26 B decumbens Ni Sin embargo nuestras estimaciones del potencial de fitorremediaci n de las plantas evaluadas sugieren que stas poseen baja eficiencia fitorremediadora Debe dirigirse investigaci n con el fin de identificar especies acumuladoras de MP m s eficientes o introducir tecnolog as que aumenten la disponi bilidad d
6. detected and some samples both matrix and plant tissues showed contents that greatly exceeded permissible limits in the Colombian and European normative ICONTEC 2004 ASCP Guidelines 2001 The present work aimed to evaluate in situ plant growth and HM absorption of the plant species Bidens pilosa Lepidium virginicum Brachiaria decumbens and Arachis pintoi grown at four sites in the Moravia dump as a measure of their phytoremediation capacity MATERIALS AND METHODS SITE DESCRIPTION The hill shaped Moravia dump is located at 6 13 N 75 34 W in Northern Medell n Antioquia Northwest Colombia alongside the right margin of the Medellin River The dump has an area of 7 6 ha and a height of 42 5 m from its base The hillsides show 274 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l mean slope values of 10 North South direction and 25 East West direction The phreatic level was determined in 19 8 m highest quote The residue hill started to grow as Medellin government designated a former mine pit as the place for the final disposition of solid residues of domestic industrial agricultural and health care origins Superficial layers 0 40 cm of the RM at Moravia show a dark sandy soil mixture with different proportions of plastics broken glass concrete wood metals semi degraded fabrics and organic matter T
7. from Moravia RM to be low However our expectation of low HM availability should not be interpreted as if the environmental threat that Moravia represents is low In this regard it is important to note that toxic metals can enter the food web not only by plant tissue absorption but also through direct ingestion of particulate material World Health Organization 2007 Hence adequate control measures must be taken as soon as possible to reduce the risk that the Moravia dump currently represents for both human beings and the environment PLANT GROWTH AND HM ABSORPTION Plant cover Mean plant cover values average of 15 observations are shown in Table 3 As the number of DAE increased plant cover increased going from 3 5 to 4 5 cm day m between 45 and 105 DAE R 0 78 Our observations showed that at the end of the evaluation period most ca 90 95 of the plots were covered with the different plant species studied Moravia Plots Linear contrasts 1 2 clay 2 3 448 6 538 0 803 8 507 9 High slope 2 vs 3 1 3 vs 2 native 2 clay 2 vs 2c High slope vs Flat 2 3 vs 1 establishment Table 3 Average plant cover cm2 at the four Moravia Plots Means with different letters are significantly different from each other P lt 0 05 according to the Duncan test 280 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia
8. in July 2008 Test species B pilosa and L virginicum were selected as our previous observations identified them as some of the most abundant plant species spontaneously growing at the Moravia dump area The grass B decumbens had been previously reported as HM accumulator Santos et a 2006 Even though to our knowledge A pintoi has not been reported in any HM absorption study the erosion control and esthetical advantages presented by this legume made A pintoi an attractive alternative to revegetate dump sites In order to obtain the propagation material for planting seeds of plant species B pilosa and L virginicum were harvested from plants growing at Moravia B decumbens seeds were purchased at a agricultural seed supplier and 45 days old A pintoi cuttings were purchased from a local garden supplier The species B pilosa L virginicum and A pintoi were planted to a final density of 6 plants m whereas B decumbens was planted to a final density of 3 kg seed ha Plant species were grown under natural conditions with no addition of amendments or fertilizers although irrigation was provided for the first two weeks after establishment This was done with the purpose of evaluating plant adaptation without adding extra cost to a future remediation process based on the use of these plants PLANT GROWTH Plant height and plant cover were registered at five sampling times corresponding to 45 60 75 90 and 105 days after plant establishment
9. of BCF which were very low and only in exceptional cases greater than 0 2 This low mobility of HM from the matrix to plant species corroborated our previous suggestion of low HM mobility within Moravia dump matrix Liang et al 2009 suggested that high BCF values could be good indicators of the potential for heavy metal accumulation From this point of view plant species tested in this study appear not to be good HM accumulators Likewise the parameters established to classify a plant species as hyperaccumulators do not demonstrate the presence of hyperaccumulators among the plant species evaluated in this study Nonetheless apart from BCF and accumulation capacity additional criteria must be considered when selecting plants for a remediation process Among others a trait that can significantly modify the plant ability to act as an effective HM accumulator is biomass production According to Liang et al 2009 high biomass plants can become effective HM accumulators on a per area basis Plant extraction mg kg and mg m Extraction of Cr mg plant showed significant differences among plant species both at 60 and 105 DAE with B pilosa extracting the most Cr 0 4 and 0 49 mg plant at 60 and 105 DAE respectively When expressing extraction of Cr in terms of mg m statistical differences were only found among plant species at 105 DAE with B decumbens extracting around 31 mg Cr m and absorption significantly greater than that of the oth
10. 20 E _ Swiss Regulation for Maximum HM limits in compost E ASCP Guidelines 2001 120 100 1 30 E Table 2 Total HM content mg kg DM in samples collected at four plots ofthe Moravia dump at three different times after plant establishment 0 60 and 105 DAE When comparing total HM contents of the matrix samples against the maximum limits permitted by the Colombian normative for compost ICONTEC 2004 the highest Pb content was 27 times that limit and the highest Ni concentration was 20 times that limit It should be considered that this normative is not as rigorous as similar normative ASCP guidelines 2001 under this normative our results are more disquieting not only for Pb and Ni but also for Cr and Cd The highest concentrations of Pb Cr Cd and Ni values mg kg were found at site 1 which could obey to high exposure to leachates as samples collected at this site came from a region localized under a very steep slope thus receiving a great deal of water infiltrated through the upper ground Besides this there was no other association between HM content and site characteristics The large variation in HM content could be explained in terms of the high heterogeneity of the Moravia dump itself a reflection of the miscellaneous nature and the random disposal of municipal wastes According to Nagendran 2006 landfills constitute a heterogeneous Acta biol Colomb Vol 15 N 2 2010 279 environment as a result of the dive
11. Acta biol Colomb Vol 15 N 2 2010 271 288 BIOMASS PRODUCTION AND HEAVY METAL ABSORPTION BY FOUR PLANTS GROWN AT THE MORAVIA DUMP MEDELLIN COLOMBIA Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia MARIA SOLANGE SANCHEZ Ph D RUB N DAR O TORRENEGRA Quimico HERNAN MARTINEZ Ph D CLAUDIA EUGENIA SALAZAR 1 A ROLANDO BARAHONA B Sc M Sc Ph D 1 Facultad de Ciencias Pontificia Universidad Javeriana Carrera 7 40 62 Bogot Colombia sanchez mariasolange gmail com rtorrene javeriana edu co Escuela de Ingenier a Facultad de Minas Universidad Nacional de Colombia Sede Medell n Medell n Colombia hmartinez unalmed edu co 3 Departamento de Producci n Animal Facultad de Ciencias Agropecuarias Universidad Nacional de Colombia Calle S9A 63 20 Medellin Colombia csalazarbenjumea gmail com rbarahonar unal edu co Presentado 8 de febrero de 2010 aceptado 3 de mayo de 2010 correcciones 19 de agosto de 2010 ABSTRACT Dumps are sites where the presence of high heavy metal HM concentration is a common occurrence creating the need for implementing restoration processes immediately after their closure In the 7 6 ha and 45 m high Morro de Moravia dump arose from the disposal of Medell n solid wastes from 1974 to 1984 previous studies have demonstrated high contents of contaminants including HM prompting the nee
12. K et al Soil contamination by heavy metals Measurements from a closed unlined landfill Bioresour Technol 2008 99 8578 8584 KOTA J STASICKA Z Chromium occurrence in the environment and methods of its speciation Environ Pollut 2000 107 263 283 LIANG HM LIN TH CHIOU JM KUO CHEN Y Model evaluation of the phytoextraction potential of heavy metal hyperaccumulators and non hyperaccumulators Environ Pollut 2009 157 6 1945 1952 NAGENDRAN R SELVAM A KURIAN J CHIEMCHAISRI C Phytoremediation and rehabilitation of municipal solid waste landfills and dumpsites A brief review Waste Manag 2006 26 1357 1369 PANSU M GAUTHEYROU J Handbook of Soil Analysis Mineralogical Organic and Inorganic Methods New York Springer Verlag Berlin Heidelberg 2006 PILON SMITS E Phytoremediation Annu Rev Plant Biol 2005 56 15 39 PRASAD MNV FREITAS H Metal hyperaccumulation in plants biodiversity prospecting for phytoremediation technology Electron J Biotechnol 2003 6 285 321 Available at http www ejbiotechnology info content vol6 issue3 full 6 SANCHEZ MS BARAHONA R SALAZAR C ARROYAVE C BEDOYA A Informe final del grupo de flora fauna y fitorremediaci n In Estudio piloto para la recupe raci n del morro de Moravia Fase Informe final de Proyecto Medell n Escuela de Ingenier a Facultad de Minas Universidad Nacional de Colombia 2009 SANTOS FS HERNANDEZ ALLICA J BECERRIL JM AMARAL SOBRINHO N MAZUR N et al Chelate in
13. M LI YM BROWN SL BREWER EP et al Phytoremediation of soil metals Curr Opin Biotechnol 1997 8 3 279 284 CUESTA PA Producci n y utilizaci n de recursos forrajeros en sistemas de producci n bovina de las regiones Caribe y Valles interandinos Manual T cnico Bogot Corporaci n Colombiana de Investigaci n Agr cola CORPOICA ISBN 958 810 79 8 2005 DAHMANI MULLER H VAN OORT F GELIE B BALABANE M Strategies of heavy metal uptake by three plant species growing near a metal smelter Environ Pollut 2000 109 231 238 EPA Method 3050B SW 846 Acid Digestion of Sediments Sludges and Soils Revision 2 http www epa gov sam pdfs EPA 3050b pdf 1996 Consultado en enero de 2009 IGAC Instituto Geogr fico Agustin Codazzi Propiedades f sicas de los suelos Bogot IGAC 1990 INSTITUTO COLOMBIANO DE NORMAS T CNICAS ICONTEC Norma t cnica colombiana 5167 Productos para la industria agr cola Productos org nicos usados 286 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l como abonos o fertilizantes y enmiendas de suelo Bogot ICONTEC 2004 INTEGRAL Estudio para la recuperaci n ambiental de la zona de Moravia en el municipio de Medell n informe final May Ist volumen 1 3 2000 Medellin rea Metropolitana del Valle del Aburr 2000 KASASSI A RAKIMBEI P KARAGIANNIDIS A ZABANIOTOU A TSIOUVARAS
14. at to soils water bodies plants and animals including human beings and indicate an excessive pollution level that should be controlled as soon as possible Fertility wise the matrix at Moravia present little limitations to plant growth as mineral and OM contents PH values and physicochemical properties approximate those of good agricultural soils and that was corroborated by the acceptable growth performance of B pilosa B decumbens A pintoi and L virginicum In addition these local and introduced plant species demonstrated their tolerance to high levels of HM as no significant phytotoxicity symptoms were observed Hence it is possible to state that the evaluated species are good alternatives to revegetate Moravia dump area and to improve its esthetical value Our different approaches to estimate the phytoremediation potential of the assayed species suggested that they possess low remediation efficiency For example results for rough calculations for Cr extraction by B decumbens assuming 11 harvests a year suggest that a total of 4 kg of Cr ha year could be extracted under Moravia conditions Since Cr Acta biol Colomb Vol 15 N 2 2010 285 concentration in the first 20 cm of soil is around 1100 k ha it would take 286 years for complete removal of this HM However phytoremediation ability should be analyzed considering several criteria On one hand high phtytoextraction capacity is highly desired even if the addition of an enha
15. covered with clay had greater plant cover values and this could be related to the higher OM Ca and K contents observed in this site as compared to the clay covered site It is accepted that OM could enhance plant growth On the other hand it is noteworthy to observe that the site with the highest leachate and HM content was the one that had the lowest plant cover for most of the evaluation period Plant height As observed with cover plant height increased as the number of DAE increased with this increase being in average 0 93 cm day plant for all plant species from 45 to 105 DAE R2 0 98 Mean plant height values for sites average of 15 observations are shown in Table 5 and those for plant species average of 20 observations are show in Table 6 There were significant interactions P lt 0 01 between plots and plant species at all sampling times At 45 and 60 DAE height of plants growing on the clay site was greater than those growing on sites not covered with clay P lt 0 05 However at 105 DAE this situation was reversed with plants growing on local sites being in average 13 higher P lt 0 05 At 75 DAE plants growing at site 1 had the highest height values 26 3 and 51 3 cm P lt 0 05 When comparing plant height across species linear contrasts showed significant differences between B pilosa and L virginicum at 60 90 and 105 DAE P lt 0 01 with B pilosa showing the greater plant height at all these sampling times There were no
16. d to identify effective mechanisms to implement its restoration The objective of this study was to evaluate the adaptation growth and phytoremediation capacity of Bidens pilosa Lepidium virginicum Brachiaria decumbens and Arachis pintoi Content of HM mg kg in Moravia residue matrix went from 17 to 8193 for Pb 44 to 564 for Cr 0 2 to 339 for Cd and 77 to 1679 for Ni Measurements of plant cover plant height and dry matter production at all plant species studied suggested adequate growth and adaptation to the Moravia dump conditions Plant absorption of HM showed the pattern Cr gt Cd gt Ni gt Pb Estimated bioconcentration factors were generally low and maximum values were 0 36 in A pintoi Cr 2 96 in B pilosa Cd and 0 26 in B decumbens Ni However our estimations of the phytoremediation potential of the assayed species suggested they possess low remediation efficiency Further investigation should be carried out in order to identify more efficient HM accumulators and to test the use of technologies such as modification of pH rhizoremediation or the use of genetically enhanced accumulators to increase HM availability to plants 272 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l Key words Bidens pilosa Brachiaria decumbens chromium lead phytoremediation RESUMEN En los basureros se observan altas concentraciones
17. duced phytoextraction of metal polluted soils with Brachiaria decumbens Chemosphere 2006 65 43 50 SHANKER AK CERVANTES C LOZA TAVERA H AVUDAINAYAGAM S Chromium toxicity in plants Environ Int 2005 31 739 753 STEUBING L GODOY R ALBERDI M M todos de ecolog a vegetal Santiago de Chile Editorial Universitaria S A 2001 SUN Y ZHOU Q WANG L LIU W Cadmium tolerance and accumulation characteristics of Bidens pilosa L as a potential Cd hyperaccumulator J Hazard Mater 2009 161 808 814 TESFAI M DRESHER S Assessment of benefits and risks of landfill materials for Agriculture in Eritrea Waste Manag 2009 29 851 858 VANGRONSVELD J VAN ASSCHE J CLIJSTERS H Reclamation of a bare industrial area contaminated by non ferrous metals in situ metal immobilization and revegetation Environ Pollut 1995 87 51 59 WEI S TEIXEIRA DA SILVA JA ZHOU Q Agro improving method of phytoextracting heavy metal contaminated soil J Hazard Mater 2008 150 662 668 WORLD HEALTH ORGANIZATION Regional Office for Europe Health risks of heavy metals from long range transboundary air pollution Copenhagen World Health Organization 2007 Acta biol Colomb Vol 15 N 2 2010 287 WSTB WATER SCIENCE AND TECHNOLOGY BOARD Bioavailability of Contaminants in Soils and Sediments Processes Tools and Applications 2003 Available online at http www nap edu YIN Y IMPELLITTERI C YOU SJ ALLEN HE The importance of organic matter distributio
18. dvantages of phytoremediation its low cost in comparison to other cleaning methods and a public acceptance as a green technology are reported Using phytoremediation technologies the extent of pollution can be reduced and soil chemical properties and biological activity could be improved Vangronsveld et al 1995 Nagendran et al 2006 A drawback of this body of scientific research is that a considerable fraction of these studies has been conducted under controlled conditions adding HM to non contaminated soils in greenhouse experiments thus differing from actual field conditions The open dump known as Morro de Moravia Moravia dump hereafter was the designated final disposal site for all sources of municipal wastes in Medellin from 1970 to 1984 Starting as a 30 m mine pit the residue matrix grew to a hill of 45 m high and became a serious threat to the environment and public health in the city Since the beginning of the dump operation Moravia dump has been inhabited and a population of near 5000 people still resides there After the dump s closure municipal authorities conducted a series of preliminary studies in order to assess the pollution level as well as to decide about the adequate measurements to restore Moravia Integral 2000 Ina more detailed study S nchez et al 2009 aimed to determine the content of Hg Pb Cr Cd and Ni in the local residue matrix RM and spontaneous vegetation samples High levels of these five HM were
19. e los MP tales como la modificaci n del pH rizorremediaci n o el uso de plantas acumuladoras gen ticamente modificadas Palabras clave Bidens pilosa Brachiaria decumbens cromo fitorremediaci n plomo INTRODUCTION The term heavy metals HM is commonly used in literature to refer to a group of metals with a density greater than 6 g cm with biological functions not yet fully understood and recognized as human health and environmental threats Among this group of contaminants As Cd Hg Pb Tl y U represent a great threat to the environment since accumulation of these elements is associated to soil air and water pollution around the world Although micronutrients such as Ni and Cr do not meet the criteria described above they are also included in the HM group since high contents of these elements are associated with adverse effects on the environment Alloway 1995 Kota and Stasicka 2000 Shanker et al 2005 Content of HM on non polluted soils is low However in some regions of the world considerable high contents have been reported as a result of several industrial or waste disposal activities Concerns related to accumulation of HM relate to the fact that they might enter the food web through different mechanisms and could bioaccumulate in higher organisms Such condition poses a threat not only to the environment but also to human health with several negative conditions such as neurological and respiratory system damages lun
20. eably increases HM extraction per unit of area In this regard Chaney et al 1997 concluded that the success of phytoextraction depends mostly upon identification of suitable plants that not only concentrate metals to high levels but also produce abundant biomass In this study the highest Cr extraction ca of 31 mg m was observed with the plant species of the greatest dry matter production B decumbens In previous reports the grass B decumbens has been shown to tolerate high Al contents in soils while displaying high biomass production fast growing characteristics and absence of phytotoxicity symptoms suggesting its potential as a phytoremediator species Santos et al 2006 CONCLUSIONS Few of the HM phytoremediation studies found in the literature have been conducted under field conditions where the effect of soil buffering capacity influences nutrient availability to plants Chaney et al 1997 This could obey to the fact that under real conditions results are difficult to understand given the high number of potential interactions As the current study was conducted in situ and in spite of the fact that under such experimental conditions predictions of plant HM absorption are often difficult our observations are quite valuable in providing a realistic idea about the adaptation growth and phytoremediation potential of the evaluated plant species Current HM concentrations in Moravia residue matrix represent a great pollution thre
21. ears that Moravia being closed for more than 20 years still provides more than adequate plant growth conditions for plants Cuesta 2006 The site covered with clay showed very low OM content which in turn is associated to low availability of N and thus plant growth could be reduced Property Site 1 Site 2 Site 2c Site 3 Sand o ep e z Time 09 z3 cay To Classification Sandy loam Ca moler 73 Mig emote E K femal ta 137 ECEC emoleg JE 6 Organic maner 73 Table 1 Physicochemical properties of the Moravia residue matrix 278 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l TOTAL HM CONTENT IN RESIDUE MATRIX SAMPLES The total HM content in samples collected at the four sites of the Moravia dump is shown in Table 2 There were not significant differences in content of any of the assayed HM among sites as SEM values of HM concentration both between sites and sampling times were high _ Sampling Time Plot Pb Cr Cd Ni First 0 DAE i 873 3 1537 Second 60 DAE 1 8755 8 2 766 Third 105 DAE 1 151 8 3 17357 Mean Value 983 3 SEM 747 0 718 2 Normal range in soils World Health Organization 2007 10 30 14 70 0 07 1 1 3 1000 e Reported mean values in a landfill in Eritrea Tesfai and _ Dresher 2009 87 7 0 Colombian Regulation for Maximum HM limits in 0 compost ICONTEC 2004 4
22. er species evaluated P lt 0 05 Extraction of Cd mg plant was low when compared to that of Cr and there were not significant differences among plant species at 60 DAE Plants extracted from 0 001 to 0 07 mg Cd plant In turn extraction of Ni mg plant and mg m did not show significant differences among plant species at any sampling time Plant Ni extraction 284 Art culo Producci n de biomasa y absorci n de metales pesados por cuatro plantas crecidas en el basurero Morovia Medell n Colombia S nchez et l varied from 0 13 to 0 24 mg plant and from 0 79 to 12 97 mg m with the highest value corresponding to B decumbens collected at 105 DAE Finally absorption of Pb was very low regardless the plant species or the site evaluated This was expected as Moravia residue matrix properties are not associated with high HM bioavailability However a very high level of Pb was detected in A pintoi sample collected at site 1 suggesting that microenvironment conditions such as leachate exposure could favor the absorption of lead into plant tissues The extraction plant and extraction m could give a better idea of the phytoextraction potential of a given plant species In our study B pilosa demonstrated the highest capacity to extract considerable amounts of Cr However B pilosa Cr extraction plant did not relate to its Cr extraction m This was due to differences in biomass production and plant density as high biomass production notic
23. exposure to leachates Site 2 Local RM 22 of slope and no leachate exposure Site 2 clay RM covered with a clay layer 22 of slope and no leachate exposure Site 3 Local RM slope of 34 and a medium leachate exposure Selected sites were manually cleaned and weeded and large solid residues were removed At each site four plots of 6 m were arranged as to plant four different plant species which were randomly allocated among the plots PHYSICO CHEMICAL PROPERTIES AND HEAVY METAL CONTENT OF THE RESIDUE MATRIX Four samples of the RM corresponding to the four sites were analyzed for physical and chemical properties following standard procedures texture was determined by Bouyoucos methodology IGAC 1990 pH was determined in water 1 1 exchangeable Ca Mg K contents were determined by the ammonium acetate method the effective cation exchange capacity ECEC was estimated as the sum of Ca Mg K in cmol kg and organic matter OM was determined according to the method reported by Walkley and Black Pansu and Gautheyrou 2006 These analyses were carried out as they may contribute to explain HM bioavailability Acta biol Colomb Vol 15 N 2 2010 275 ZONA DE ESTUDIO BARRIO MORAVIA MUNICIPIO DE MEDELLIN DIVISION POLITICA POR COMUNAS Figure 1 Moravia dump localization in Medellin Antioquia Colombia PLANT SPECIES SELECTION ESTABLISHMENT AND EVALUATION Plant species were planted
24. g and kidney cancer and dermatitis among others being associated to the exposure ingestion or inhalation of HM World Health Organization 2007 Acta biol Colomb Vol 15 N 2 2010 273 Plant absorption of HM depends on several factors inherent to soil and plant characteris tics High mobility and bioavailability of HM in soils is normally related to low pH values lt 5 and low organic matter content in soils Alloway 1995 In turn different groups of plants among ornamental crops and wild species have been identified as HM accumula tors Such species include several families among which Asteraceae Brassicaceae Caryophyllaceae Cyperaceae Cunouniaceae Fabaceae Flacourtiaceae and Lamiaceae are the most common Prasad y Freitas 2003 Pilon Smits 2005 Wei et a 2008 Due to their purpose final disposal of municipal wastes landfills and dumps usually contain high amounts of HM thereby becoming a threat to human health and to the environment Associated risks are even greater in situations where dump operations do not include a residue separation program or a leachate treatment Natural or man directed revegetation following the closure of landfills and dumps can be very important to control erosion improve the aesthetic value and contribute to the decontamination of these places The use of plants to clean polluted sites known as phytoremediation has received a great deal of attention during the lasts two decades Among the a
25. hese layers also contain various types of pipes for drinkable and residual water transport around the inhabited houses As it is common in most open dumps the Moravia dump does not have a drainage system or a system for the treatment of leachates According to 2008 calculations the dump is producing a total leachate effluent of 1 78m day S nchez et al 2009 Due to the progressive reallocation of Moravia inhabitants conducted by Medell n municipal authorities several plots in Moravia dump have been emptied and a revegetation process both spontaneous and man influenced is currently taking place In such plots it is evident the predominance of the herbaceous stratum In our previous study S nchez et al 2009 it was determined that B pilosa and Urochloa maxima were the most abundant plant species A final feature of the Moravia dump is the presence of a clay covered plots originated when municipal authorities placed a 20 cm thick clay layer on top of the RM in an attempt to diminish soil erosion and thus dispersion of pollution SELECTION OF PLANTING SITES Figure 1 shows the localization of the four sites selected for the evaluation Criteria for site selection included presence no presence of a clay superficial layer slope gradient and exposure to leachates Sites were designated by numbers 1 to 3 and had the following characteristics Site 1 Local RM this is residue matrix without a clay layer 15 of slope and high
26. ield conditions on soils contaminated with other HM in addition to Cd in an ongoing process of more than 20 years The pattern of Cd content in plant tissue suggests that the plants tested absorb Cd very actively during their first stages of growth thus resulting in early accumulation of this metal in their tissues However as plant development continues Cd absorption stops and via an apparent dilution effect Cd concentration diminished in plant tissues Bioconcentration factors BCF were calculated as the ratio between HM content in plant tissue and that in the residue matrix data not shown Although there were no statistical differences among BCF values estimated for either plant species or sites great variability was observed for these values For example the maximum BCF values observed were 0 36 in A pintoi in the case of Cr 2 96 in B pilosa in the case of Cd and 0 26 in B decumbens in the case of Ni Overall HM absorption by plants under the conditions of the Moravia dump had the following order Cr gt Cd gt Ni gt Pb It is commonly understood that high HM content in the soil does not necessarily relates to high content of HM in plant tissues ever since the process of plant absorption depends upon several interacting physicochemical soil properties Pilon Smits 2005 In our study HM absorption in plant tissues was low when compared to the HM contents in the residue matrix This observation was corroborated with the calculations
27. ies there were two linear contrasts made Ls1 B pilosa and L virginicum vs B decumbens or A pintoi this is the comparison between plant species previously found among the spontaneous vegetation vs plant species introduced to the Moravia dump Ls2 B pilosa vs L virginicum RESULTS AND DISCUSSION PHYSICAL AND CHEMICAL PROPERTIES There were great differences in physical and chemical properties Table 1 between samples obtained from the RM sites and the sample collected from the site covered with clay Samples of the RM were classified as sandy loam whereas the clay covered site was classified as clay loam In what refers to cation content Ca contents were high in all RM samples being almost three times higher than the clay covered site In turn contents of Mg were low in RM average 1 8 cmolc kg and about 6 times higher in samples obtained from the clay covered site Potassium content was high for RM sites and low in the clay covered site ECEC values ranged from 21 9 cmolc kg site 2 clay to 33 3 cmolc kg site 2 Organic matter content varied greatly going from 7 8 to 12 9 in RM samples with the corresponding value for site 2 clay being only 1 According to Cuesta 2006 OM content values greater that 5 in semitropical climate are considered high Soil pH showed a narrow range going from 7 0 site 3 to 7 6 sites 1 2 and 2c Since properties such as texture pH and OM content are good estimators of fertility it app
28. n and extract soil solution ratio on the desorption of heavy metals from soils Sci Total Environ 2002 287 1 2 107 119 ZHANG XH LIU J HUANG HT CHEN J NIAN ZY WANG DQ Chromium accumulation by the hyperaccumulator plant Leersia hexandra Swartz Chemosphere 2007 67 1138 1143
29. ncer is required On the other hand economical factors as the management of harvested plant material containing high levels of HM should also be evaluated and additional factors such as the value of revegetation for erosion control and improvement of esthetical characteristics must be factors to consider when deciding the goals of a plant based landfill dump restoration program Finally it should be kept in mind that low HM plant absorption observed within this study does not eliminate other risks of entrance of toxic metals to the food web such as ingestion of particulate material World Health Organization 2007 Further investigation should be carried out in order to identify more efficient HM accumulators and to test the use of technologies designed to increase HM availability to plants such as modification of soil pH rhizoremediation or the use of genetically enhanced accumulators ACKNOWLEDGMENTS We gratefully acknowledge the Area Metropolitana del Valle de Aburr and the Empresa para el Desarrollo Urbano in Medellin Antioquia for providing the financial support for this project BIBLIOGRAPHY ALLOWAY BJ Heavy Metals in Soils 2ed London Blackie Academic Professional 1995 ASCP GUIDELINES Quality Criteria for Composts and Digestates from Biodegradable Waste Management Schoenbuehl ASCP 2001 Available at the web site http www kompostverband ch acrobatreader vks_richtlinie_english pdf March 2009 CHANEY RL MALIK
30. om 21 1 to 32 8 60 DDE and from 7 4 a 24 4 105 DDE mg kg on a DM basis There were no significant differences among sites or plant species However there were differences between the two sampling times P 0 007 Cadmium Detectable Cd contents were observed at 60 DAE with values ranging from 1 3 mg kg A pintoi to 8 2 mg kg B decumbens However Cd content decreased considerably at the end of the evaluation 105 DAE and was only found in detectable concentrations in L virginicum and B pilosa 0 09 y 0 71 mg kg respectively Statistical analysis for 60 DAE samples did not show significant differences P gt 0 05 between plant species or sites but showed significant differences between the first and second sampling times P 0 004 Plants can be classified as HM hyperaccumulators if they accumulate more than 100 Cd 1000 Ni Pb y Cu or 10000 Zn o Mn mg kg of DM Dahmani Muller et al 2000 Sun et al 2009 reported B pilosa as a hyperaccumulator as more than 100 mg kg of Cd were detected in aerial organs of this plant species In our study B pilosa Acta biol Colomb Vol 15 N 2 2010 283 had high absorption of Cd and Cr but not to the same extent as described by Sun et al 2009 These differences could be associated to differences in soil properties and microenvironment since the reported study was conducted on non contaminated soils that had recently received and addition of Cd and our study was conducted under f
31. raction of HM in terms of mg plant and mg m2 were calculated on a DM basis and were also carried out at 60 and 105 DAE For the first estimate mg plant the DM value was multiplied for the mg kg of HM in dry plant tissues whereas for the second estimate mg metal m the mg metal plant was multiplied by the density of plants per m STATISTICAL ANALYSIS Data obtained for the different variables and estimates were subjected to an analysis of variance ANOVA using a randomized block design with four treatments corresponding to the four plant species evaluated For each variable plant cover plant height and plant HM content an independent analysis for each sampling time was conducted Where significant differences were observed mean values were separated by means of the Duncan test When the ANOVA analysis showed a significant P lt 0 05 interaction between sites and plant species linear contrasts were calculated in order to compare mean values for both sites and plant species Linear contrasts L for sites were conducted by the criteria described below L1 Site 2c clay covered vs local RM sites 1 2 and 3 Acta biol Colomb Vol 15 N 2 2010 277 L2 Sites 2 and 3 slope gt 20 vs L3 Sites 2 2c and 3 with slope lt 20 vs Site 1 with slope lt 20 L4 Sites within the same localization within the dump 2 and 2 clay vs distant plots 3 1 L5 Site 1 vs Site 3 L6 Site 2 vs Site 2 clay For plant spec
32. rsity of the residues they receive Likewise Kasassi et al 2008 explained the high variation in Ni values observed in landfills as the result of the random disposition of batteries and electric equipment waste Such condition could also explain the extremely high Pb values observed in the present study A practical consideration for this high variation in HM content across Moravia is that it adds difficulty to the selection of a single plant species for any phytoremediation approach being more likely for a plant consortium to be needed for the efficient extraction of the HM present there Characteristics of the Moravia residue matrix such as OM content pH and ECEC values can be used to estimate HM bioavailability In this regard several studies have reported that soils with high clay content have superficial negative charges that efficiently adsorb soil cations including HM By contrast low lt 5 soil pH values are associated to high concentrations of H ions that can replace HM cations leaving these in solution and ready to be absorbed by plants Normal ECEC values ranged from 0 to 60 cmolc kg and exhibit an inverse relationship with cation availability High contents of OM are inversely correlated to HM bioavailability since OM increases the soil absorption capacity towards metals Alloway 1995 Yin et al 2002 WSTB 2003 Pilon Smits 2005 According to our determinations for these parameters it should be expected for HM bioavailability
33. s were removed The remaining substrate was mixed to obtain a representative sample from each plot thus collecting a total of 16 soil samples corresponding to one sample per plot Content of Pb Cr Cd and Ni in plant tissues was determined at 60 and 105 DAE Two individual plants randomly selected per plot were prepared in the same way as described for the DM determination Determination of HM both in residue matrix and plant tissues was carried out at the GDCON Laboratory University of Antioquia following standard procedure methodology SW 846 3050B EPA 1996 Briefly 1 g samples were subjected to calcination at 450 C and the resulting ashes were subjected to acid digestion using a 1 1 mixture of HNO and HCIO4 Concentration of HM was determined by means of atomic absorption using a GBC 932spectrophotometer and HM content estimated as mg kg of DM Detectable limits mg kg were 0 001 for Hg 0 125 for Pb 0 250 for Cr and Ni and 0 050 for Cd ESTIMATION OF THE BIOCONCENTRATION FACTOR AND HEAVY METAL EXTRACTION The bioconcentration factor BCF is defined as the ratio between the HM concentration in the plant tissue and the soil or substrate in which the plant is growing BCF is an estimate of species ability to take up HM from soils Plant species with BCF greater than 1 are considered to have phytoremediation potential Sun et al 2009 Zhang et al 2007 In this study the estimation of BCF was conducted at 60 and 105 DAE The ext
34. t mg kg and HM extraction mg m in plant species grown in four plots at Moravia dump are presented in Table 7 No acute toxicity due to HM absorption was evident in B pilosa B decumbens and L virginicum However there was an initial chlorosis in A pintoi plants which occurred at 45 and 60 DAE after which plants fully recovered With regard to the tolerance of plant species to HM contamination Sun et al 2009 reported high tolerance of B pilosa to soils artificially contaminated with 100 mg kg of Cd In their study plants only had a 22 reduction in chlorophyll content and other physiological parameters did not change significantly from the values observed in the control plants Absorption of HM exhibited the following patterns Lead In all samples collected at 60 DAE Pb content was under the detection limit 0 05 mg kg However at 105 DAE in five of the 16 plant tissue samples detectable Pb concentrations were found which ranged from 0 77 to 32 38 mg kg data not shown Nickel Ni absorption in plant tissues followed a similar pattern as that of Pb with Ni not being detected in plant tissues collected at 60 DAE However at 105 DAE most of the analyzed samples showed different contents of this metal with values ranging from 4 4 to 11 0 mg kg although no significant differences were observed across plant species or sites P gt 0 05 Chromium Most collected samples contained detectable amounts of Cr at 60 and 105 DAE ranging fr
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