The Volatilization of Pollutants from Soil and Groundwater: Its Importance in Assessing Risk for Human Health for a Real Contaminated Site

Transcription

1 Journal of Environmental Protection, 2011, 2, doi: /jep Publihed Online November 2011 ( The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for Pamela Morra, Laura Leonardelli, Gigliola Spadoni Department of Chemical, Mining & Environmental Engineering, Alma Mater Studiorum, Univerity of Bologna, Bologna, Italy. Received July 25 th, 2011; revied Augut 29 th, 2011; accepted October 4 th, ABSTRACT Pollution of different element (air, water, oil and uboil) reulting both from accidental event and from ordinary indutrial and civil activitie caue negative effect on the human health and on the environment. The preent paper examine the analyi of a contaminated ite, focuing the attention on the negative effect for receptor expoed to oil and groundwater contamination caued by indutrial activitie. The cae tudy invetigated i a contaminated area located in the indutrial ditrict of Trento North once occupied by the Italian Carbochimica plant. Pollution in that area i mainly due to contamination of oil and groundwater with polycyclic aromatic hydrocarbon. The methodology applied i the rik evaluation for human health, in term of individual cancer rik and hazard index. In particular the attention ha been focued on a pecific migration way: if pollutant in the oil or in the groundwater undergo a phae change, they pread and get to the oil urface, cauing a diperion of vapor in the atmophere. In thi cae rik aement call for the evaluation of volatilization factor. Among the different model dealing with the etimation of volatilization factor, thoe motly known and ued in the national and international field of Human Health Rik Aement were choen: Jury and Farmer model. A enitivity analyi of model wa performed, in order to identify the mot ignificant parameter to etimate the volatilization factor among the wide range of input parameter for the application of model. Performing an accurate election and data proceing of the contaminated ite, model for the volatilization factor calculation are applied, thu evaluating air concentration and Human Health Rik. The analyi of the reulting etimate i an excellent aid to draw intereting concluion and to verify if the oil and groundwater pollutant volatilization affect the human health coniderably. Keyword: Human Health Rik Aement, Volatilization Model, Soil Contamination, Groundwater Contamination, Cancer Rik, Hazard Index 1. Introduction Pollution of different element (air, water, oil and uboil) reulting both from accidental event and from daily indutrial and civil activitie, implie effect on the human health and on the environment. Through the application of the Human Health Rik Aement methodology in a pecific contaminated ite, it i poible to evaluate the magnitude and probability of negative effect poed to human being caued by expoure to contamination in variou media [1]. The conolidated procedure concerning the rik analyi applie the RBCA approach [2], which refer to a tep method baed on three level of aement. In the following we refer to a tier 2 rik aement, involving ite-pecific data collection and analytical modeling of the fate and tranport of contaminant acro the environmental media involved (in particular unaturated oil, groundwater and outdoor air). Receptor expoure typically are decribed a contact between the chemical of concern (COC) and the body exchange boundarie (kin, lung and gatrointetinal tract) acro which the chemical can be aborbed [3]. Expoure aement alo include the identification and quantification of the multiple pathway and multiple route that characterize the movement of a chemical from it ource to an expoed individual. Frequently, in a itepecific human health rik analyi, among all the potential pathway (inhalation, ingetion and dermal expoure) and migration route, it i poible to identify a few one that have a predominant influence on the evaluation of

2 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1193 final individual cancer rik and hazard index for a receptor group. In the preent paper the attention ha been focued on the pathway of volatilization of hazardou vapor coming from contaminated oil and groundwater into open air and conequent expoure of receptor to COC. The aim of thi tudy are to: 1) identify the parameter that more affect the etimate of the volatilization factor and their uncertainty, 2) evaluate the importance of volatilization of pollutant from oil and groundwater in the rik aement for human health through the application of the model to a real contaminated ite cae-tudy. In order to reach the firt objective, a election of imple and diffuely ued model for the etimation of volatilization factor in rik analyi wa performed thu operating a enitivity analyi on input parameter for the application of model; the econd objective ha been approached through the invetigation of a cae-tudy concerning a contaminated area located in northern Italy, where contamination of oil and groundwater i mainly due to polycyclic aromatic hydrocarbon deriving from the productive cycle in remote indutrial activitie. 2. Vapor Migration modeling 2.1. Volatilization Factor In the aement of human health rik, the etimation of tranport factor i neceary, thu conidering the migration of pollutant from the contamination ource to the target. When the volatilization i regarded, the tranport factor i called volatilization factor (VF) and conider the attenuation phenomena occurring during migration. VF repreent the ratio between the pollutant concentration in the expoure ite (c poe, expreed for example in mg/m 3 ) and the concentration at the contamination ource (c expreed for example in mg/kg), a reulting from oil ample or calculated applying model: c VF c (1) poe Detailed model of contaminant tranport in oil and groundwater include procee uch a diffuion, diperion and convection phenomena for each of the phae preent in the oil. Obviouly, uch model include a large number of contaminated ite parameter and oilpecific parameter that are often not available or not very accurate. Therefore, in mot volatilization phenomena etimate, predictive model are implified in order to allow the application of model even in ituation where a few ite pecific parameter are available [4]. For every oil layer a different volatilization factor i identified: VF (volatilization of outdoor vapor from urface oil), VF d (volatilization factor of outdoor vapor from deep oil), VF gw (volatilization factor of outdoor vapor from groundwater). Thee factor are ued to etimate outdoor air concentration of volatile by uing the known chemical concentration in the groundwater and oil. Among the volatilization model from uburface ource into outdoor air available in literature, two model were elected, widely applied in the Rik Aement for Human Health and Environment and uggeted by EPA [1,5,6], ISPRA [7] and ASTM tandard [2,8]. In detail the volatilization model elected are: - Jury model [9,10], auming a contamination ource with emi-infinite dimenion and time-varying concentration (etimation of VF,J1 and VF,J2 for urface oil and VF d,j for deep oil), - Farmer model [11], with teady-tate aumption (etimation of VF,F for urface oil, VF d,f1, VF d,f2 for deep oil and VF gw for groundwater). Thee model make the following common aumption when calculating volatilization factor: uniform and iotropic oil (fiuring-porou oil i not conidered); the chemical do not biodegrade in oil, in water olution or in vapor phae; no tranport within water, no aborption or production of the gae; the partitioning between the chemical in the groundwater/oil matrix and vapor i linear; chemical loe by biodegradation do not occur between the groundwater/oil and the urface; for outdoor emiion, teady-tate atmopheric diperion of vapor occur within the breathing zone. The calculation of VF, hence the concentration of volatile outdoor, i baed on the movement of volatile from the oil and groundwater up through the capillary zone, through the unaturated zone, and emiion into the breathing zone in outdoor air (Figure 1). The model relationhip are derived from imple onedimenional or integral ma balance, baed on the dif- Wind direction Air Mixing Height Surface oil Deep oil Contaminated groundwater Contaminated ub-oil Contaminated urface-oil Vadoe zone Capillary zone Groundwater Figure 1. Conceptual model of vapor migration to outdoor air.

3 1194 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for ferent hypothei of the conidered volatilization model. In particular VF,J1 derive from Jury model, baed on the one-dimenional application of Fick law conidering the following aumption and condition: abence of boundary layer at the interface oil-air, thu auming a perfect mixing ituation in air; no water flow i conidered through the oil (the pollutant lo due to it tranport into the groundwater i thu not conidered and liciviation i therefore conidered apart from volatilization); the oil contaminated column of emi-infinite depth ha homogeneou phyical characteritic; finally a boundary condition conider that the oil concentration at the ground level mut be zero. It worth noting that the condition of equilibrium partitioning i very rarely accomplihed in the uburface, therefore calculated oil vapor value from oil-phae data may clearly overetimate or underetimate actual oil vapor concentration. VF,J2 and VF d,j are the upper limit of Jury model and a a reult are a conervative evaluation. Briefly, they conider a ma balance in which the total value of ma that can enter into the mixing volume (correponding to the total ma of pollutant in the urface oil) i equal to the ma coming out of the mixing volume becaue of the aeolian tranport during expoure time. Therefore the application of thee relation do not take into account the pecific contaminant propertie. VF,F, VF d,f1, VF d,f2, VF gw are obtained in Farmer model. Thi model conider an initial uncontaminated layer of oil (depth L) between the contamination ource top and the ground level. Vapor flux i calculated applying the Fick law in teady-tate condition, o any time reduction in ource contamination due to the volatilizing phenomena are not included. The equation VF,F i not conidered ince the outcome value of outdoor volatilizing factor from urface oil reult extremely conervative for volatile compound and not really conervative for the le volatile one, when compared to the reult of the equation VF,J1. Depite the fact that they come from the ame model, VF d,f1 i different from VF d,f2, ince they apply different hypothei: the econd one conider the air flow from oil, while the firt one count it a negligible. VF gw ue thi lat hypothei, but it i applied to the groundwater characteritic. It worth noting that thee model, though widely ued in rik aement analyi, are baed on implifying hypothei that make them not alway fitting the reality of the cae-tudie. A an example, weaknee and critical apect of the model are related to water oluble compound, contaminated ource with non-homogenou propertie and time-variant volatilization quantitie. Equation of volatilization factor according to Jury and Farmer are reported in the following (ee Figure 2 for conceptual model ued and Table 1 for parameter included in the equation): VF VF 2W DA kg, J1 U air air π 3 m A d kg, J 2 Uair air L 3 m VF d, J 3 Uair air m (2) (3) W d kg (4) 1 kg VF D A VF 1 (5) VF, F A d, F 3 Uair air L L m D kg A A d, F 2 3 L eff m Uair air L D VF H gw 3 Uairair L GW m 1 eff Dw W where the following parameter are included: D D H 2 eff A D w k Ha 1 m eff a w w m Da 2 2 e H e (6) (7) (8) D (9) 1 h 2 eff cap h v m w cap v eff eff Dcap D D h h D eff cap a, cap D w, cap w m Da 2 2 e H e (10) (11) In order to apply model for the volatilization factor aement a wide et of input parameter ha to be con- LGW hv hcap Surface oil Deep oil Groundwater Wind direction LS d U air L d W A Figure 2. Repreentation of ome geometrical parameter in the cheme of conceptual model. δ air

4 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1195 Table 1. Lit of parameter in volatilization factor model. d Thickne of contamination ource in the urface oil m d Thickne of contamination ource in the deep oil m h cap Height of capillary zone m h v Height of unaturated zone m L Depth to uburface oil contamination ource m L GW Depth to groundwater (= h cap + h v ) m L Extenion of contamination ource in acro-wind direction m W Width of contamination ource area parallel to wind direction or groundwater flow direction m A Contamination ource area m 2 ρ Soil bulk denity kg/m 3 θ e Effective terrain poroity in unaturated zone dimenionle θ w Volumetric water content dimenionle θ a Volumetric air content dimenionle θ w,cap Volumetric water content in the capillary zone dimenionle θ a,cap Volumetric air content in the capillary zone dimenionle k S Soil-water orption coefficient m 3 H 2 O/kg oil eff D eff D w eff D cap Effective diffuion coefficient in oil baed on vapor-phae concentration m 2 / Effective diffuion coefficient between the groundwater and oil urface m 2 / Effective diffuion coefficient through capillary zone m 2 / D a Diffuion coefficient of the ubtance in air m 2 / D w Diffuion coefficient of the ubtance in water m 2 / H Henry Law contant dimenionle δ air Ambient air mixing zone height m U air Wind peed above the ground urface in the ambient mixing zone m/ τ Average duration time of vapor flux idered, characterizing geometry of contamination, the contaminated oil and the above air characteritic, and the phyicochemical pollutant propertie. An analyi of the volatilization factor wa carried out in the open literature in order to etablih the mot uitable tranport factor for every environment ection. Both for the urface oil and the deep oil, the approach propoed by tandard ASTM 1739/95 [2], PS 104/98 [8] and by Handbook Unichim 196/01 [12] wa adopted. Between the two evaluation VF,J1 and VF,J2, in particular the firt equation i uggeted for the le volatile compound while the econd one i ued for very volatile compound. The ame choice i uggeted alo by the oftware RBCA Tool Kit [13], BP-RISC [14] and GIU- DITTA [15]. A regard the deep oil both the equation VF d,f1 and the equation VF d,f2 gave nearly the ame reult. Following the approach uggeted by Unichim Handbook 196/01 [12], the equation VF d,f2 and VF d,j were conidered. In particular VF d,f2 wa adopted for the le volatile compound while VF d,j for thoe very volatile. A a matter of fact the value upplied by the equation VF d,f2 were too high and thu too conervative if applied to very volatile compound. Thi kind of approach i adopted by oftware GIUDITTA [15] and RBCA Tool Kit [13]. It worth noting that the model analyi evidenced that the incongruou ituation may occur in which the VF for urface oil value i lower than the VF value for deep oil, but the reaon of thi lay obviouly on the different hypothei at the bai of the two different model typologie. Regarding aturated oil only a volatilizing factor VF gw wa conidered. Thi equation i uggeted by tandard ASTM 1739/95 [2], PS 104/98 [8], by Unichim Handbook 196/01 [12] and by all the oftware examined (BP- RISC ver. 4.0, RBCA Toolkit ver. 1.2., GIUDITTA ver. 3.1 and ROME ver. 2.1) Senitivity Analyi of Volatilization Model The enitivity analyi i a common technique ued in

5 1196 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for the modeling iue to ae the effect of variability and uncertainty of parameter on the reult obtained from the application of a pecific mathematical model [16]. In particular, in thi ection the aim i the enitivity analyi of the tranport factor previouly decribed, thu identifying the variable that motly affect thee factor and therefore the human health. A explained in the previou ection the elected volatilization factor are: VF,J1 and VF,J2 for urface oil, VF d,j and VF d,f2 for deep oil, VF gw for groundwater. In the analyi, a typical volatile ubtance (benzene) and a le volatile one (benzo(a)pyrene) are taken into account, in order to conider both the expreion for urface oil and deep oil. In particular VF,J1 and VF d,f2 are applied for benzo(a)pyrene, while VF,J2 and VF d,j are applied for benzene. VF gw i uitable for both compound. A preliminary analyi of which parameter are involved in the variou volatilization factor i pecified in Table 2. In the lit, ome parameter are not reported becaue they are not independent, but are correlated a follow: A and L (A/L = W); θ a (θ a = θ e θ w ); θ acap (θ acap = θ e θ wcap ); h v (h v = LGW h cap ). A brief remark ha to be noted for the oil-water orption coefficient k : thi parameter define the ubtance partitioning property between the olid phae (oil) and the water phae. It i evaluated a the partition oil-water coefficient (k d ) that correpond to (k OC f oc ) for organic compound, where k OC i the carbon-water partition coefficient and f oc repreent the organic carbon fraction in unaturated oil. In thi cae, only f oc i conidered in the variability analyi, wherea the carbon-water partition coefficient i examined a a fixed parameter, a the other pecific compound propertie D a, D w and H. Table 3 how all the pecific compound propertie utilized in the preent enitivity analyi (bold font) and in the cae tudy after decribed. The application of the enitivity analyi to the volatilization factor attempt to provide a ranking of the model input baed on their relative contribution to model output variability and uncertainty. A enitivity indicator the Senitivity Ratio (SR), alo called elaticity and the Senitivity Score (SS) are taken into account [16]. The Senitivity Ratio (SR) i the change in model output per unit change in an input variable, a hown in the following equation. Y2 Y ref X2 X ref SR Y (12) ref X ref where X ref and Y ref are the reference etimate for an input variable and the correponding value of the output variable, while X 2 and Y 2 repreent the value of the input variable after changing and the correponding value of the output variable. The enitivity ratio aume different value if different reference value are taken into account: for thi reaon etimation with minimum, maximum and mean value ha been performed. The Senitivity Score (SS) i a variation of the enitivity ratio approach; it may provide more information, but it require additional information for the input variable. Thi core i the SR weighted by a normalized meaure of the variability in the input variable, a hown in the following equation. Xmax Xmin SS SR (13) X mean where X max and X min are the maximum and minimum value repectively, of an input variable, while X mean i the mean or reference value of an input variable. The VF etimate are conidered mot enitive to input variable that yield the highet abolute value for SR and SS. In order to evaluate thee preliminary enitivity indicator, the poible minimum, maximum and mean value aumed by the involved parameter have been examined and reported in Table 4. In particular the range of value taken into conideration derive from an analyi of all poible terrain typologie and environment condition and the le and mot probable value aumed by the parameter are the minimum and maximum value. For thoe parameter for which were not poible the evaluation of a maximum value, the enitivity core ha not been calculated. The Senitivity Ratio (SR, with a change of 10% in the input parameter) and the Senitivity Score (SS) near the minimum value, mean value and maximum value ha been calculated for benzene and benzo(a)pyrene. The evaluated SR and SS are utilized to rank the involved parameter, according to ranking criteria derived from national guideline [7]. The enitivity core i the preferred indicator; for parameter without SS, the enitivity ratio i taken into account. Table 5 how the level of enitivity of volatilization factor for each parameter, conidering an average ituation among the enitivity ratio and core etimated near minimum, mean and maximum parameter value. Obviouly for SR etimation the ame form of dependency of ome parameter for different volatilization factor, reult in a imilar behavior of the enitivity ranking. It reult that among the oil and groundwater parameter, volumetric water content (θ w ), volumetric water content in the capillary zone (θ w,cap ) and organic carbon fraction f oc are relevant for the enitivity of volatilizetion factor, beide thoe parameter eay predictable a

6 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1197 Table 2. Dependency of parameter in the volatilization factor. Source and ite pecific parameter Soil pecific parameter Outdoor parameter Compound pecific parameter d d L L gw W ρ h ca θ e θ w θ w,ca f oc δ ai U air τ D D w H k d /k oc VF,J1 VF,J2 VF d,j VF d,f2 VF gw Table 3. Compound-pecific parameter [1]. Compound D a (cm 2 /) D w (cm 2 /) H K OC (cm 3 /g) Carcinogenic/Toxic propertie Volatility Acenaphthene T +/- Anthracene T +/- Benzene C/T + Benz(a)anthracene C/T - Benzo(a)pyrene C/T - Benzo(b)fluoranthene C/T +/- Benzo(g,h,i)perylene T - Benzo(k)fluoranthene C/T - Chryene C/T +/- Dibenz(a,h)anthracene C - Ethylbenzene T + Fluoranthene T - Fluorene T +/- Indeno(1,2,3 c,d)pyrene C/T - Naphthalene C/T + Pyrene T - Toluene T + Xylene T + Table 4. Range of value for parameter taken into account in the enitivity analyi. Minimum value Maximum value Mean/Default value Meaure unit d m d 0 n.a. (L GW -1) 2 m h cap m L 1 n.a. (L GW - d ) 2 m L GW 1 n.a. 3 m W 0 n.a. 30 m ρ kg/m 3 θ e dimenionle θ w dimenionle θ w,cap dimenionle f oc dimenionle δ air m U air m/ τ (reidential); 25 (indutrial) year

7 1198 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for Table 5. Senitivity ranking of parameter for the volatilization from oil and groundwater of benzene and benzo(a)pyrene. Volatilization factor a decribed in 2.1. d d VF,J1 VF,J2 VF d,j VF d,f2 VF gw Sot. B Sot. A Sot. A Sot. B Sot. A Sot. B M/H H h cap M/H M/L L L GW L H W H H H H H H ρ L L L L θ e L M/L M M θ w H H M/L M θ w,cap H L f oc M H δ air M/H M/H M/H M/H M/H M/H U air M M M M M M τ L M/L M/L Subtance A: benzene; Subtance B: benzo(a)pyrene; SS enitivity criteria: 0 < SS 0.5 Low (L); 0.5 < SS 1 Middle/Low (M/L); 1 < SS 1.5 Middle (M); 1.5 < SS 2 Middle/High (M/H); SS > 2 High (H) SR enitivity criteria: 0 < SR 0.33 Low (L); 0.33 < SR 0.66 Middle (M); SR > 0.66 High (H). H priori a the contamination ource geometry (W, d, d, L ) and the ambient air mixing zone heigth (δ air ). A a final tep of the enitivity analyi, a Monte Carlo Simulation ha been performed, auming a Gauian probability ditribution for the variability of input parameter to derive a probability ditribution of outcome. Thi approach allow multiple input variable to vary imultaneouly in order to rank ordering the input variable contribution to variability in the outcome etimate. The graph (Figure 3) extracted by the application of the Crytal Ball oftware [17] how both the relative magnitude and direction of influence (poitive or negative) for each variable in the calculation of Volatilization Factor (Contribution to Variance). The imulation wa performed with 100,000 trail and correlated aumption have been applied. The Gauian probability ditribution of each input parameter are et up fitting minimum, mean and maximum value or fitting value for different oil typologie [18-21]. In particular in order to build the Gauian ditribution, it ha been aumed the mean of the ditribution a the mean/default value a indentified before and the tandard deviation a about one third of the ditance between the mean and the minimum or the maximum value. The oftware Crytal Ball calculate enitivity by computing Spearman rank correlation coefficient [22], which meaure the trength and direction of aociation between input variable and output etimate while the imulation i running. Correlation coefficient provide a meaningful meaure of the degree to which output and input change together. If an input and an output have a high correlation coefficient, it mean that the input ha a ignificant impact on the output; poitive coefficient indicate that an increae in the input i aociated with an increae in the output while negative coefficient imply the oppoite ituation. The larger the abolute value of the correlation coefficient, the tronger the relationhip. In addition, to help interpret the rank correlation, Crytal Ball compute the Contribution to Variance (a repreented in the above cited graph) that deignate what percentage of the variance in the target output i due to the pecific input; it i calculated by quaring the rank correlation coefficient and normalizing them to 100%. The analyi of contribution to variance in enitivity chart almot confirm the reult obtained in the etimation of the implified analyi with SR and SS etimation: in the cae of le volatile compound, the volumetric water content (θ w ) ha a predominant role among parameter in volatilization factor from oil and groundwater, followed by f oc in the volatilization from oil and L GW in the volatilization from groundwater; in the cae

8 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1199 Figure 3. Senitivity chart for Volatilization Factor reulting from Monte Carlo Simulation (Contribution to Variance). of very volatile compound a benzene, thickne of contamination ource i the prevailing parameter in volatilization from oil, while h cap in volatilization from groundwater. In both cae the dimenion of the contamination ource W ha a medium weight in the contribution of variance differently from the high enitivity ranking evaluated by the SR and SS evaluation; otherwie the wind velocity, which the SR and SS etimation evaluated in all cae with a medium ranking, ha in the Monte Carlo analyi a medium contribute to variance for volatilization of very volatile compound and a lower contribute for volatilization of le volatile compound. 3. Cae Study: North Trento 3.1. Site Decription A cae tudy, regarding a contaminated area in Trentino Alto Adige, i hereby analyzed. The area in exam i in the elf-governing province of Trento, in the abandoned indutrial area of north Trento, once occupied by the Carbochimica Italiana plant (42,700 m 2 ) which ha been the lat owner of the ite. The plant activity wa initially tar ditillation for road work and waterproofing and wa then extended to the production of naphthalene, oil for wood, pitch for electrode, phthalic anhydride and fumaric acid. In 1983, after a declining of activity and the economic inability to invet in proce water depuration, the plant wa cloed. In the middle of the 80 plant of Carbochimica Italiana were demolihed and the indutrial ite wa dimied. The ite i in the lit of priority of the contaminated ite of national interet. In 2001 a barrier ha been realized a environmental contingency action for groundwater, in order to put a hydraulic confine for the contamination diperion. Since September 2004 experimentation about reclamation on demontrative cale ha begun, in order to tet the reult

9 1200 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for of the chemical oxidation by mean of ozone technology [23]. The area i till characterized by oil and groundwater pollution a a conequence of the productive activity that took place in the area without a proper control of productive cycle. The ite ha been analyzed with a monitoring campaign in which a large amount of data ample have been produced: 219 urvey, 879 ample and 23,738 chemical analye for about a hundred of chemical compound. Among thee, eighteen ubtance have been analyzed, extracting the one with higher concentration, wore toxicity propertie and more extenive detection. The lit of ite contamination ubtance i reported in the Table 3, in which compound-pecific parameter are reported. For each analyzed ubtance carcinogenic and/ or toxic claification and volatility characteritic are reported. Mot of the analyzed compound exceed the limit value of the contaminated ite etablihed by national regulation for oil and for ome ubtance groundwater limit, too Conceptual Model: Contaminated Site, Soil and Groundwater Characterization The tratigraphy of uboil in the north Trento area i characterized by a urface oil 1 meter depth of filling terrain (SS in VF calculation), the beneath deep oil of andy loam texture and, at about 2.5 m (h v ) from terrain level, the aturated area. The piezometric ocillation of groundwater level can be conidered ± 1.5 m. The monitored data ample have been et apart a contamination in urface oil and in deep oil. The urface oil and the deep oil have been conidered conervatively a fully contaminated (d = 1 m, d = 1.5 m). Capillary height for andy loam texture i aumed a 0.25 m [24]. The contaminated area i chematized to a rectangle of dimenion 140 m 300 m (W parallel and L orthogonal to wind direction). The groundwater direction i the ame a the wind one ince both groundwater and wind direction follow the Adige Valley direction (from north-wet to outh-eat). Wind velocity U air and direction are obtained from the meteorological tation of Trento-Roncafort (194 m a..l.). A value of 1.37 m/ ha been calculated a the mean wind velocity, meauring data of a recent year with an anemometer localized at 10 m of height, o for conervative approximation a mean value of about 1 m/ ha been aumed at the ambient air mixing zone height (2 m). Soil propertie are aumed a thoe typical of andy loam texture. A uggeted in the national guideline [7], the mean duration time of vapor flux i poed coinciding with the expoure duration of receptor. For indutrial/commercial area the conidered value i 25 year. The contamination ditribution mapping ha been realized arranging a georeferenced databae with the concentration mean value of the different pollutant in the urface oil and in the deep oil in 171 ampling point. A regard the groundwater concentration value, a homogeneou mean ditribution ha been conidered, taking into account a few available monitoring point in proximity of the indutrial area. The analyzed ite ha been ubdivided in a number of cell with ide parallel and orthogonal to the wind direction, which coincide with the groundwater flux direction; the dimenion of the cell are W = 16 m parallel and L = 15 m orthogonal to wind direction. An etimation of urface oil, deep oil and groundwater contamination ha been poible for each identified cell of the ite, in thi way allowing the calculation of the volatilization factor in the entire area. Since the oil propertie are conidered uniform in the analyzed contaminated ite, a decribed above, the calculation of the volatilization factor reult in a contant VF for each ubtance, evaluated for each cell of the ite Volatilization and Human Health Rik Reult Volatilization factor for urface oil, deep oil and groundwater have been calculated from the conceptual model built up on the bai of the available information about the contaminated ite. The concentration of each contaminant i in air c air,i i conervatively calculated by umming the contribution of the volatilization from urface oil, deep oil and groundwater: c VF c VF c VF c (14) air, i, i, i d, i d, i gw, i gw, i where c,i, c d,i and c gw,i are repectively the concentration of the compound i in the urface oil, deep oil and groundwater, while VF,i, VF d,i, VF gw,i are the correponding volatilization factor. Among the VF relation, a explained before, the election i a follow: VF,J1 for the le volatile compound and VF,J2 for very volatile compound about the urface oil, VF d,f2 for the le volatile compound and VF d,j for thoe very volatile a regard the deep oil, VF gw for groundwater. The application of Jury and Farmer model reult in VF that range from kg/m 3 (calculated for indeno(1,2,3-c,d)pyrene) to kg/m 3 for very volatile compound; VF d range from kg/m 3 (calculated for indeno(1,2,3-c,d)pyrene) to the maximum value of kg/m 3 for very volatile compound; finally VF gw range from l/m 3 (calculated for dibenz(a,h)anthracene) to

10 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1201 l/m 3 etimated for xylene. The tranfer factor for le volatile compound reult everal order of magnitude lower than thoe for very volatile one, but the relative concentration in air obviouly depend alo by the contamination level in oil and groundwater. A the ditribution of pollutant in groundwater i conidered uniform in the contaminated ite, the term related to the groundwater, i.e. concentration in air due to volatilization from groundwater, i contant. The contribute of the polluted groundwater to the total value of air concentration i null or limited (up to 3%) for a dozen of ubtance, medium-level for acenapthene and pyrene (up to 11%) and naphthalene (up to 41%), and high/ prevailing for thoe ubtance for which the contmination of urface and deep oil i localized in only a few monitoring point (benzene, benzo(k)fluoranthene, ethylbenzene, toluene and xylene). Uing the potentiality of the map calculation in Gi ytem, the total concentration in air i calculated and mapped for each of the eighteen conidered ubtance. A an example in Figure 4 Benzo(a)pyrene concentration (in µg/m 3 ) ditribution in air due to the contribution of urface oil, deep oil and groundwater volatilization i repreented, a calculated from the available data in monitored point ample. In order to calculate the human health rik caued by the analyzed contaminated ite, among all the poible expoure cenario, the ingetion, dermal contact and outdoor inhalation cenario are taken into account, a chematized in the conceptual model in Figure 5. In performing the human health rik analyi, the receptor conidered a potential target of the contamination are indutrial worker localized on the dimied area. Thi choice wa dictated by conideration about the actual utilization of the ite: ince the dimiing of the plant, the ex-indutrial area wa abandoned, but periodically upervied and ubjected to maintenance and numerou monitoring campaign. In order to calculate the expoure intake for the identified receptor, the tandard procedure in human health rik aement have been utilized [5,16]. The expoure intake are expreed a ma of ubtance in contact with the organim, normalized by time unit and body weight (mg/(kg d)); a ummary of the relation ued in the procedure can be found in [25]. Human health rik aement conit in the quantification of Individual Cancer Rik and Hazard Quotient for the expoed population, i.e. the computation of the upperbound exce lifetime cancer rik and noncarcinogenic hazard for each of the pathway and receptor identified in the area of interet. Cancer rik i defined a the probability that a receptor will develop cancer in hi lifetime, auming a unique et of expoure, model, and toxicity propertie. In contrat, hazard i quantified a the potential for developing noncarcinogenic health effect a a reult of expoure to COC, averaged over an expoure period. It i worth noting that hazard i not a probability but, more exactly, a meaure of the magnitude of a receptor potential expoure relative to a tandard expoure level. The individual cancer rik of a receptor j et by expoure to multiple carcinogenic chemical i, can be cal- Figure 4. Benzo(a)pyrene concentration (in µg/m 3 ) ditribution in air due to the contribution of urface oil, deep oil and groundwater volatilization.

11 1202 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for Figure 5. Conceptual model of the human health rik aement: expoure cenario. culated, for low doe expoition hypothei, through the following equation: Individual _ CancerRik j LADDi, jcsfi (15) where: LADD ij i Lifetime Average Daily Doe for a lifetime expoure of 70 year (mg/kg day) through multiple expoure pathway CSF i i the Cancer Slope Factor for COC i (mg/kg day) 1. Comparing an expoure etimate to a Reference Doe (RfD), the potential for noncarcinogenic health effect reulting from expoure to a chemical i evaluated. A RfD i defined a a daily intake rate that i etimated to caue no appreciable rik of advere health effect, even to enitive population, over a pecific expoure duration [5]. Generally, the more the Hazard Quotient value exceed 1, the greater i the level of concern. Baed on imilar COC toxicological characteritic and additive health effect, the Hazard Quotient (HQ) for receptor j expoed to multiple chemical i, i calculated a: ADDi, j HQ j [16] RfD i where ADD ij i the Average Daily Doe averaged for the expoure duration relative to the toxic i for the receptor j (mg/kg day) through multiple expoure pathway RfD i i the COC i Reference Doe (mg/kg day) below which there are no advere effect. The parameter value adopted for the etimation of the expoure intake are thoe typically utilized for the human health rik aement in the cae of worker receptor [26]. The etimation of the expoure time and expoure frequency reult from the conideration that the area i dimied ince year and that maintenance work are not requeted every day. A a reaonable hypothei, it ha been conidered a total number of 1500 hour of expoure for worker receptor. Table 6 how the carcinogenicity and toxicity value i i of the conidered ubtance utilized for the etimation of Individual Cancer Rik and Hazard Quotient, extracted from U.S. EPA IRIS Databae. Summing the contribution of all the carcinogenic ubtance and all the toxic ubtance, the ditribution of total individual cancer rik and total hazard quotient, repectively, ha been etimated on the conidered zone, a repreented in Figure 6(a) and Figure 7(a). A expected, for receptor located and directly expoed on contaminated ite, total individual cancer rik ha quite high value, epecially in the north ide of the area. The hazard quotient approache the value of 1 only in a very limited pot of the area. It worth noting that the calculated cancer rik and hazard quotient value don t take into account any protection of the receptor, thu reulting exceively conervative and unrealitic. It i evident that worker uually ue Peronal Protective Equipment (PPE) conforming to the regulation in force for afety ubject during maintenance and monitoring activitie in contaminated ite. The ue of PPE a glove and mak can be taken into account in the etimation of rik by conidering a reduction factor. A regard the inhalation expoure, if a mak giving protection from dut and ga with mean aigned protection factor i conidered, a reduction factor of 1/30 can be uppoed (EN 133, EN 529 tandard). For dermal contact expoure wearing glove (EN tandard) and for ingetion expoure wearing a afety mak, a reduction factor of 1/100 can be conervatively hypotheized. The reult conequently obtained adopting the protection reduction factor are repreented in Figure 6(b) and Figure 7(b), where it i evident an average decreae of rik of about 2 order of magnitude. In particular for total individual cancer rik, value above the limit typically conidered a threhold acceptability, 10 5, are almot diappeared, while for hazard quotient, value are all reduced under 0.01 etimate. The analyi of the contribution of pathway to both cancer rik and hazard quotient put in evidence that total cancer rik i mainly due to the dermal contribution Thi aement can be ued a a ignificant criterion to elect the more appropriate PPE in order to reduce rik of expoed worker. In thi pecific cae the inhalation pathway contribution due to volatilization of COC from oil and groundwater doe not contitute the prevailing concern of the contaminated ite, but a particular regard ha to be poed to dermal contact and therefore to a good choice of afety glove during maintenance and monitoring activitie on the polluted area. Finally the analyi of the contribution of the conidered ubtance how that in the etimation of cancer

12 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1203 Table 6. Carcinogenicity and toxicity value for the conidered ubtance. inhalation ingetion dermal inhalation ingetion dermal CSF (mg/kg-d) 1 CSF (mg/kg-d) 1 CSF (mg/kg-d) 1 RfD (mg/kg-d) RfD (mg/kg-d) RfD (mg/kg-d) Acenaphtene n.a. n.a. n.a Anthracene n.a. n.a. n.a Benzene Benz(a)anthracene Benzo(a)pyrene Benzo(b)fluoranthene Benzo(g,h,i)perylene n.a. n.a. n.a Benzo(k)fluoranthene Chryene Dibenz(a,h)anthracene n.a. n.a. n.a. Ethylbenzene n.a. n.a. n.a Fluoranthene n.a. n.a. n.a Indeno(1,2,3-c,d)pyrene Naphthalene Pyrene n.a. n.a. n.a Toluene n.a. n.a. n.a Xylene n.a. n.a. n.a Figure 6. Total Individual Cancer Rik for worker localized directly on the contaminated dimied area, without PPE (a) and with PPE (b).

13 1204 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for Figure 7. Total Hazard Quotient for worker localized directly on the contaminated dimied area, without PPE (a) and with PPE (b). rik benzo(a)pyrene i the main caue, while the hazard quotient i mainly originated by naphthalene, followed by pyrene and chryene. 4. Concluion To quantify the negative effect to receptor expoed to oil and groundwater contamination, human health rik aement methodology i uually applied, to evaluate individual cancer rik and hazard index. The paper examined in particular the diperion of contaminant vapor through volatilization from oil and groundwater in the atmophere. Volatilization factor have been etimated applying Jury and Farmer model. The enitivity analyi of model, performed with the Senitivity Ratio, Senitivity Score and Monte Carlo Simulation, identified the mot ignificant parameter: volumetric water content, thickne of the contamination ource and height of capillary zone among the wide range of input parameter for the application of model. Finally a cae tudy regarding a contaminated area located in the indutrial ditrict of Trento North wa invetigated. A conceptual model of the ite wa built up, proceing the available monitored data; the concentration of everal contaminant in air were evaluated through the etimation of volatilization factor. Individual Cancer Rik and Hazard Quotient have been calculated for worker receptor localized on the contaminated ite, analyzing the inhalation, ingetion and dermal pathway. In the coni- dered contaminated ite, the volatilization of compound from contaminated oil and groundwater doe not contitute the main concern: the dermal contribution reult the prevailing pathway for rik and the obtained reult can advie the appropriate ue of PPE that enable the coniderable decreae of the rik for the expoed receptor. Adopting conervative reductive factor accounting for the protection of PPE, the reulting individual cancer rik and hazard quotient are clearly below the acceptability limit. 5. Acknowledgement We would like to acknowledge the autonomou province of Trento for the upport during thi tudy and for providing the monitoring data relative to the contaminated ite of Trento North. REFERENCES [1] U.S. EPA, Soil Screening Guidance: Technical Background Document and Uer Guide, Office of Solid Wate and Emergency Repone, Wahington D.C., EPA/540/R-95/128, [2] ASTM, American Society for Teting and Material Standard Guide for Rik-Baed Corrective Action Applied at Petroleum Releae Site, E , Wet Conhohocken, PA, [3] U.S. EPA, Guideline for Expoure Aement, Federal Regiter, Vol. 57, No. 104, 1992, pp

14 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for 1205 [4] J. Grifoll and Y. Cohen, Chemical Volatilization from the Soil Matrix: Tranport through the Air and Water Phae, Journal of Hazardou Material, Vol. 37, No. 3, 1994, pp doi: / (93)e0100-g [5] U.S. EPA, Rik Aement Guidance for Superfund, Volume I: Human Health Evaluation Manual. Interim Final, Office of Emergency and Remedial Repone, Wahington D.C., OSWER Directive /a, [6] U.S. EPA, Soil Screening Guidance: Technical Background Document, [7] APAT, Criteri Metodologici per l Applicazione Dell Analii Aoluta di Richio ai Siti Contaminati. rev.2, Roma, 2008 (in Italian). [8] ASTM, American Society for Teting and Material Standard Proviional Guide for Rik-Baed Corrective Action, Report PS104-98, [9] W. A. Jury, W. F. Spencer and W. J. Farmer, Behaviour Aement Model for Trace Organic in Soil: I. Model Decription, Journal of Environmental Quality, Vol. 12, No. 4, 1983, pp doi: /jeq x [10] W. A. Jury, D. Ruo, G. Streile and H. E. Abd, Evaluation of Volatilization by Organic Chemical Reiding below the Soil Surface, Water Reource Reearch, Vol. 26, No. 1, 1990, pp doi: /wr026i001p00013 [11] W. J. Farmer, M. S. Yang, J. Letey and W. F. Spencer, Hexachlorobenzene: It Vapor Preure and Vapor Phae Diffuion in Soil, Proceeding of Soil Science Society of America, Vol. 44, 1980, pp doi: /aj x [12] Unichim, Manuale n.196/01 Suoli e Falde Contaminati, Analii di Richio Sito-Specifica, Criteri e Parametri, 2002 (in Italian). [13] RBCA Tool Kit 1.2, RBCA Tool Kit for Chemical Releae, Groundwater Service Inc., Texa, [14] RISC 4.0, Rik-Integrated Software for Clean-up Uer manual, BP-Amoco Oil, Sunbury UK, [15] GIUDITTA 3.1, Manuale d uo/allegati, Provincia di Milano-URS Dame and Moore, 2006 (in Italian). [16] U.S. EPA, Rik Aement Guidance for Superfund: Volume III Part A, Proce for Conducting Probabilitic Rik Aement, OSWER 9285, EPA 540-R , 2001, pp [17] Deciioneering, Inc., Crytal Ball Uer Manual, 2005 [18] R. F. Carel and R. S. Parrih, Developing Joint Probability Ditribution of Soil Water Retention Characteritic, Water Reource Reearch, Vol. 24, No. 5, 1988, pp doi: /wr024i005p00755 [19] J. A. Connor, C. J. Newell and M. W. Malander, Parameter Etimation Guideline for Rik-Baed Corrective Action (RBCA) Modeling, NGWA Petroleum Hydrocarbon Conference, Houton, November [20] M. Th. Van Genuchten and P. J. Wierenga, Ma Tranfer Studie in Sorbing Porou Media: I. Analytical Solution, Soil Science Society of America Journal, Vol. 40, No. 4, 1976, pp doi: /aj x [21] M. Th. Van Genuchten, A Cloed-Form Equation for Predicting the Hydraulic Conductivity of Unaturated Soil, Soil Science Society of America Journal, Vol. 44, No. 5, 1980, pp doi: /aj x [22] E. L. Lehmann, Nonparametric: Statitical Method Baed on Rank, New York, Springer, [23] G. Andreottola and C. Simonini, Tet di Ozonizzazione in itu di Terreni Contaminati da IPA. Riultati Preliminary, Proceeding of Conference in Nuovi Indirizzi Nella Bonifica dei iti Contaminati - La Prai, la Normativa, le Nuove Tecnologie, Provincia di Milano, 2004 (in Italian). [24] C. W. Fetter, Applied Hydrogeology, 3rd Edition, Prentice Hall, Engelwood Cliff, [25] P. Morra, S. Bagli and G. Spadoni, The Analyi of Human Health Rik with a Detailed Procedure Operating in a Gi Environment, Environment International, Vol. 32, No. 4, 2006, pp doi: /j.envint [26] U.S. EPA, Expoure Factor Handbook, National Center for Environmental Aement, Wahington D.C., EPA/600/R-09/052A, 2009

15 1206 The Volatilization of Pollutant from Soil and Groundwater: It Importance in Aeing Rik for Notation δ air ambient air mixing zone height ρ oil bulk denity θ a volumetric air content θ a,cap volumetric air content in the capillary zone θ e effective terrain poroity in unaturated zone θ w volumetric water content θw,cap volumetric water content in the capillary zone τ average duration time of vapor flux A contamination ource area ADD Average Daily Doe averaged for the expoure duration c poe pollutant concentration in point of expoure c pollutant concentration at the contamination ource COC Chemical of Concern CSF Cancer Slope Factor d thickne of contamination ource in the urface oil d thickne of contamination ource in the deep oil DA diffuivity D a diffuion coefficient of the ubtance in air D capeff effective diffuion coefficient through capillary zone D w diffuion coefficient of the ubtance in water D eff effective diffuion coefficient in oil baed on vapor-phae concentration D weff effective diffuion coefficient between the groundwater and oil urface foc organic carbon fraction H Henry law contant h cap height of capillary zone h v height of unaturated zone k d partition oil-water coefficient k OC carbon-water partition coefficient k oil-water orption coefficient L extenion of contamination ource in acro-wind direction L GW depth to groundwater L depth to uburface oil contamination ource LADD Lifetime Average Daily Doe for a lifetime expoure of 70 year R fd Reference Doe U air wind peed above the ground urface in the ambient mixing zone VF volatilization factor of outdoor vapor from urface oil VF d volatilization factor of outdoor vapor from deep oil VF gw volatilization factor of outdoor vapor from groundwater W width of contamination ource area parallel to wind or groundwater flow direction