Barbara Nisi

Degradation of C2–C15 volatile organic compounds in a landfill cover soil

The composition of non-methane volatile organic compounds (hereafter VOCs) in i) the cover soil, at depths of 30, 50 and 70 cm, and ii) gas recovery wells from Case Passerini landfill site, (Florence, Italy) was determined by GC-MS. The study, based on the analysis of interstitial gases sampled along vertical profiles within the cover soil, was aimed to investigate the VOC behaviour as biogas transits from a reducing to a relatively more oxidizing environment. A total of 48 and 63 different VOCs were identified in the soil and well gases, respectively. Aromatics represent the dominant group (71.5% of total VOC) in soil gases, followed by alkanes (6.8%), ketones (5.7%), organic acids (5.2%), aldehydes (3.0%), esters (2.6%), halogenated compounds (2.1%) and terpenes (1.3%). Cyclics, heterocyclics, S-bearing compounds and phenols are <or=1%. In the wells the VOC composition is characterized by higher concentrations of cyclic (7.6%) and S-bearing compounds (2%) and lower concentrations of O-bearing compounds. The vertical distribution of VOCs in the cover soil shows significant variations: alkanes, aromatics and cyclics decrease at decreasing depth, whereas an inverse trend is displayed by the O-bearing species. Total VOC and CH(4) concentrations at a depth of 30 cm in the soil are comparable, inferring that microbial activity is likely affecting VOCs at a very minor extent with respect to CH(4). According to these considerations, to assess the biogas emission impact, usually carried out on the sole basis of CO(2) and CH(4) emission rates, the physical-chemical behaviour of VOCs in the cover soil, regulating the discharge of these highly contaminant compounds in ambient air, has to be taken into account. The soil vertical distribution of these species can be used to better evaluate the efficiency of oxidative capability of intermediate and final covers.

Distribution of gaseous hg in the mercury mining district of mt.amiata (central italy): a geochemical survey prior the reclamation project.

The Mt. Amiata volcano is the youngest and largest volcanic edifice in Tuscany (central-northern Italy) and is characterized by a geothermal field, exploited for the production of electrical energy. In the past Mt. Amiata was also known as a world-class Hg district whose mining activity was mainly distributed in the central-eastern part of this silicic volcanic complex, and particularly in the municipality of Abbadia San Salvatore. In the present work we report a geochemical survey on Hg(0) measurements related to the former mercury mine facilities prior the reclamation project. The Hg(0) measurements were carried out by car for long distance regional surveys, and on foot for local scale surveys by using two LUMEX (915+ and M) devices. This study presents the very first Hg(0) data obtained with this analytical technique in the Mt. Amiata area. The facilities related to the mining areas and structures where cinnabar was converted to metallic Hg are characterized by high Hg values (>50,000ngm(-3)), although the urban center of Abbadia San Salvatore, few hundred meters away, does not appear to be receiving significant pollution from the calcine area and former industrial edifices, all the recorded values being below the values recommended by the issuing Tuscany Region authorities (300ngm(-3)) and in some cases approaching the Hg background levels (3-5ngm(-3)) for the Mt. Amiata area.

New occurrence of reed bed decline in southern Europe: Do permanent flooding and chemical parameters play a role?

Based on the experimental design proposed in similar studies, macromorphological and ecological traits of common reed beds were analysed at Lake Chiusi (Central Italy), together with selected chemical parameters in sediments and interstitial waters and aerial images of the site, in order to investigate reed decline and search for possible correlations among data. Typical symptoms of the reed dieback syndrome were detected, thus enlarging the occurrence of this phenomenon in southern Europe. Permanently dry, permanently flooded and partially flooded stands show different levels of decline, with the permanent flooding always co-occurring with reed dieback. Only few of the considered chemical parameters seem to play a role in reed decline (nitrates, rubidium, nickel, barium, manganese), although no clear pattern was identified. Data suggest that the co-occurrence of some chemicals with stressing conditions might affect the growth even of an efficient metal accumulator, as reed is generally considered.

Geochemical characterization of the ground waters from the former Hg-mining area of Abbadia San Salvatore (Mt. Amiata, central Italy): criticalities and perspectives for the reclamation process

This study was aimed to geochemically characterize the groundwater system of the Abbadia San Salvatore (Mt. Amiata, Siena, central Italy) former Hg-mining area, whose activity closed at the end of the seventies, in order to accomplish the reclamation process after that the former ownership of the mining concession (E.N.I. National Agency for Hydrocarbons, AGIP Division) passed the property to the Munici pality of Abbadia San Salvatore in 2008. The study area covers a surface of about 65 ha and since February 2013 old and new piezometers were used to assess the main chemical features along with the concentrations of As, Hg and Sb. Four sampling campaigns were carried out up to January 2014 and a relatively large spatial and temporal geochemical variability was observed. Apparently, the working activities related to the construction of an artificial channel (commenced in March 2013 and terminated at the end of 2013), which crosscuts the whole mining area to drain the surface waters in order to minimize the interaction between the meteoric waters and the by-products deriving by the production of metallic mercury, did not affect the groundwater system. Slag, roasted material and other by-products deriving from the local and surrounding Hg mining activities were indeed used to fill the terrain where most of the mining structures lie. The dominating geochemical facies was Ca(Mg)-SO4 and, subordinately, Ca(Mg)-HCO3, while Na-HCO3 compositions were rarely found. Dissolution of gypsum/anhydrite and carbonates and hydrolysis of sulfide minerals are likely the main geochemical process that produced the observed geochemical compositions. The contents of As and Sb only sporadically exceeded the maximum allowable concentrations intended for human consumption (98/83 EC Directive 1998), i.e. 10 and 5 mg L-1. Conversely, those of Hg were constantly above the EC directive, e.g. 1 mg L-1, with the exception of those waters located up- and downstream the groundwater flow. This indicates that the exotic filling terrains in the mining area, mainly consisting of roasting products, likely play a pivotal role in regulating the concentrations of Hg, which reached values up 853 mg L-1. The construction of permeable reactive barriers, located downstream the water flow, appears to be the most promising solution for the removal of Hg, although, according to the literature, several materials, tested with laboratory experiments, can be used and, as a consequence, it is necessary to individuate specific piezometers with different Hg concentrations where pilot investigations are to be carried out before undertaking any remediation actions.

Flux measurements of benzene and toluene from landfill cover soils

Carbon dioxide and CH 4, C6H6 and C7H8 fluxes from the soil cover of Case Passerini landfill site (Florence, Italy) were measured using the accumulation and static closed chamber methods, respectively. Results show that the CH4/CO2, CH4/ C 6H6 and CH4/C7H8 ratios of the flux values are relatively low when compared with those of the ‘pristine’ biogas produced by degradation processes acting on the solid waste material disposed in the landfill. This suggests that when biogas transits through the cover soil, CH4 is affected by degradation processes activated by oxidizing bacteria at higher extent than both CO2 and mono-aromatics. Among the investigated hydrocarbons, C6H6 has shown the highest stability in a wide range of redox conditions. Toluene behaviour only partially resembles that of C6H6, possibly because de-methylation processes require less energy than that necessary for the degradation of C6H6, the latter likely occurring via benzoate at anaerobic conditions and/or through various aerobic metabolic pathways at relatively shallow depth in the cover soil where free oxygen is present. According to these considerations, aromatics are likely to play an important role in the environmental impact of biogas released into the atmosphere from such anthropogenic emission sites, usually only ascribed to CO2 and CH4. In this regard, flux measurements using accumulation and static closed chamber methods coupled with gas chromatography and gas chromatography—mass spectrometry analysis may properly be used to obtain a dataset for the estimation of the amount of volatile organic compounds dispersed from landfills.

Towards the Concept of Background/baseline Compositions: A Practicable Path?

Water geochemistry is often investigated considering a large number of variables, including major, minor and trace elements. Some of these are usually well associated due to coherent geochemical behaviour, but the effect of anthropic factors tends to increase data variability, sometimes obscuring the natural laws governing their relationships. It may thus be difficult to identify geochemical features linked to natural phenomena, as well as to separate geogenic anomalies from the anthropogenic ones, or to define background or baseline concentrations for single chemical elements. This is particularly true at regional level, where numerous phenomena may interact and mix together, forming a complex pattern not easy to interpret. The identification of background or baseline values is particularly difficult due to the compositional nature of chemical variables, so that under the Compositional Data Analysis (CoDA) theory single background or baseline values lose their meaning. However, they are fundamental references for public institutions and government policies. In this contribution a new approach is proposed, aimed at investigating the regionalised structure of the geochemical data by considering the joint behaviour of several chemical elements. The approach is based on the robust CoDA theory, so that the proportionality features of abundance data are fully taken into account, enhancing their relative multivariate behaviour, as well as the influence of outliers. An application example is presented for the groundwater compositions in Tuscany Region, a surface of about 23,000 km\(^2\), where more than 6000 wells have been sampled and analysed. The mapping of robust Mahalanobis distance was able to indicate (1) in which part of the investigated area the pressure toward anomalous behaviour was higher, (2) where the compositions nearest to the barycentre were and (3) if spatial continuity was present in limited portions of the territory.

GEOBASI: The geochemical Database of Tuscany Region (Italy) Acque Sotterranee

In this study the new Regional Geochemical Database (RGDB), called GEOBASI, is presented and illustrated in the framework of a joint collaboration among the three Tuscan universities (Florence, Pisa and Siena), CNR-IGG (Institute of Geosciences and Earth Resources of Pisa), ARPAT (Regional Agency for the Environmental Protection), LAMMA (Environmental Modelling and Monitoring Laboratory for Sustainable Development) Consortium and S.I.R.A. (Territorial and Environmental Informative System of Tuscany). The database has permitted the construction of a repository where the geochemical information (compositional and isotopic) has been stored in a structured way so that it can be available for different groups of users (e.g. institutional, public and private companies). The information contained in the database can in fact be downloaded freely and queried to correlate geochemistry to other non compositional variables. The first phase of the project was aimed at promoting the use of the geochemical data already available from previous investigations through a powerful Web-GIS interface to implement the exploratory statistics graphical-numerical tools used to: 1) analyse the spatial variability of the investigated context, 2) highlight the geographic location of data pertaining to classes of values or single cases, 3) compare the results of different analytical methodologies applied to the determination of the same element and/or chemical species, 4) extract the geochemical data related to specific monitoring plans and/or geographical areas, and finally 5) recover information about data below the detection limit to understand their impact on the behaviour of the investigated variable. Developments of this project will be focused on the definition of rules and standardized methods in a way that external users could also interactively pursue the RGDB. Furthermore, a detailed investigation of the Scarlino-Follonica plain will permit the improvement and test of statistical and geostatistical methods, using open source software (QGIS and R) to support the process of evaluation of the geochemical baseline.

Groundwater Contamination Studies by Environmental Isotopes: A review

Water demand for urban, industrial, and agricultural purposes is a major concern in developed and third world countries. A careful evaluation for an appropriate and sustainable use of water resources is a priority. Geochemical processes can lead to measurable variations of the aquatic environment, which can be studied through the analysis of the dissolved solutes. Even if this review is not meant to be exhaustive, it is intended to give a view on the importance of environmental isotopes in the context of groundwater quality assessments. This is done by briefly recalling some basic notions for each described system, followed by relevant applications and reports about some significant case studies. This review includes well-established isotopic systematics, such as those of O and H in water, C in dissolved inorganic carbon (DIC), S and O in sulfates, and N and O in nitrates and those of boron and Sr, which in the last lustrums have found large application in the field of water geochemistry. This chapter ends with some examples related to nontraditional isotopes, i.e., Fe, Cr, and Cu, in order to highlight the potential of the environmental isotopes to trace sources, fate, and behavior of different solutes and metals in surface water and groundwater.

Monitoring of Soil Gases in the Characterization Stage of CO 2 Storage in Saline Aquifers and Possible Effects of CO 2 Leakages in the Groundwater System

The main objective of this chapter is to describe which analytical methodologies and procedures can be applied at the surface to monitor and verify the feasibility of geologically stored carbon dioxide.

Gaseous Elemental Mercury and Total and Leached Mercury in Building Materials from the Former Hg-Mining Area of Abbadia San Salvatore (Central Italy)

Mercury has a strong environmental impact since both its organic and inorganic forms are toxic, and it represents a pollutant of global concern. Liquid Hg is highly volatile and can be released during natural and anthropogenic processes in the hydrosphere, biosphere and atmosphere. In this study, the distribution of Gaseous Elemental Mercury (GEM) and the total and leached mercury concentrations on paint, plaster, roof tiles, concrete, metals, dust and wood structures were determined in the main buildings and structures of the former Hg-mining area of Abbadia San Salvatore (Siena, Central Italy). The mining complex (divided into seven units) covers a surface of about 65 ha and contains mining structures and managers’ and workers’ buildings. Nine surveys of GEM measurements were carried out from July 2011 to August 2015 for the buildings and structures located in Units 2, 3 and 6, the latter being the area where liquid mercury was produced. Measurements were also performed in February, April, July, September and December 2016 in the edifices and mining structures of Unit 6. GEM concentrations showed a strong variability in time and space mostly depending on ambient temperature and the operational activities that were carried out in each building. The Unit 2 surveys carried out in the hotter period (from June to September) showed GEM concentrations up to 27,500 ng·m−3, while in Unit 6, they were on average much higher, and occasionally, they saturated the GEM measurement device (>50,000 ng·m−3). Concentrations of total (in mg·kg−1) and leached (in μg·L−1) mercury measured in different building materials (up to 46,580 mg·kg−1 and 4470 mg·L−1, respectively) were highly variable, being related to the edifice or mining structure from which they were collected. The results obtained in this study are of relevant interest for operational cleanings to be carried out during reclamation activities.