Massimo Fagnano1*, Paola Adamo1, Antonio Di Gennaro2, Fabio Terribile 1 1 Dipartimento di Scienze Agrarie, Università di Napoli Federico II, Via Università, 100 780055 Portici, Napoli
2 Risorsa SrL,Viale Raffaello, 15, 80129 Napoli *[email protected]
Abstract
Italian environmental legislation highlighted several weaknesses in relation to the definition of the actually contaminated soils, mainly as regards agricultural soils. The first one is related to sampling methodologies (i.e setting up the sampling scheme and the depth of the soil layer to be sampled) aimed to perform the environmental characterization of potentially contaminated soils. The second weak point is the absence of specific references to the agricultural use of contaminated soils. In this paper we present a multidisciplinary approach for solving these weak points carried out in the frame of the LIFE11- ENV/IT/275 project and reported in the Ecoremed Handbook (Fagnano, 2017).
For the Environmental characterization we proposed a preliminary series of geophysical measurements to identify anomalies which would then be analysed with direct excavation of pits or soil profiles.
Keywords: contaminated soils; agricultural use; environmental characterization; agronomic approach. Parole chiave: suoli contaminati, uso agricolo; caratterizzazione ambientale; approccio agronomico. Introduction
The definition of contaminated soil is a two-step process. Firstly, we must compare the analytical data of a site with the table of screening values (SV). If some value exceeds the SV, then the site is defined potentially contaminated. In order for a site to be termed “contaminated” we must perform an analysis of health and environmental risks. The procedure as well as the tools available (e.g. Software Risknet 2.0 or ISPRA 2009), however, take into account only the direct risks for those who frequent the site and are therefore related to hours of exposure to contaminated soil particles that can reach the human target through inhalation, ingestion and skin contact. The risks for the environment linked to the leaching of contaminants in groundwater are also considered.
In the case of agricultural soils in addition to the direct risks, we need another step for assessing indirect risks for end users who could consume the products obtained on contaminated sites.
Analysis of Italian environmental legislation highlighted several weaknesses in relation to the definition of the actually contaminated soils, mainly as regards agricultural soils. The first one is related to sampling methodologies (i.e setting up the sampling scheme and the depth of the soil layer to be sampled) aimed to perform the environmental characterization of potentially contaminated soils. In Law Decree 152/06 there are no mandatory rules regarding rational sampling schemes or sampling layers. Normally reference is made to previous laws (Annex 2 to Ministerial Decree 471/99) which establish that 1-2 samples per hectare have to be taken and a composite sample of the 0-1 m layer has to be collected. Clearly, a soil sample 10 cm in diameter cannot be representative of an area of 10,000 m2 and pollution levels, which are often higher in
the top centimeters of soils, could be drastically underestimated if they were diluted in a 1 m layer. The second weak point is the absence of specific references to the agricultural use of contaminated soils.
At this regards Art. 241 of the Single Environmental Text makes the following provision: a “regulation on remediation,
environmental restoration and emergency operative and permanent safety measures, of the areas for agricultural production and husbandry, was adopted by decree of the Minister for the environment and land and sea protection in concert with the Ministers for Industry, Health and Agriculture and Forestry policy”. The above regulation, after 11 years
has not yet been adopted.
Currently, in Italy, agricultural soil pollution standards are based on total or pseudototal PTM content. It represents an excellent criterion to define the extent of metal contamination in soil, but it is of little value for the prediction of ecological impact. In agricultural soils, knowledge of PTM bioavailability is also required for a scientifically based evaluation since total metal content is not directly correlated to the effective absorption by plants. Finally the measurements of PTMs accumulation in plants can give the final assessment of the risks for health of consumers of the crops produced in such sites.
In this paper we present a multidisciplinary approach for solving these weak points carried out in the frame of the LIFE11- ENV/IT/275 project and reported in the Ecoremed Handbook (Fagnano, 2017). This approach was also reported in the regulation drawn up by a technical committee which included the presence of the working group of the Ministerial Directive of December 23, 2013 (Environmental Ministry, 2014).
Materials and Methods
Validation of the proposed methodologies was carried out in a 6 ha field situated in Giugliano in Campania (NA), sequestered from a criminal as it was used for disposal of industrial sludge rich in Cr and Zn.
For the Environmental characterization we proposed a preliminary series of geophysical measurements to identify anomalies which would then be analysed with direct excavation and sampling of pits or soil profiles.
Geophysical modelling provides generalized and nonunique solutions to questions concerning the geometry and physical organization of soil cover. Hence a well-conducted study generally requires complimentary geophysical surveys integrated with field survey and targeted sampling of different soil horizons.
The methodological approach involves the combined use of several indirect surveys to characterize contaminated or potentially contaminated sites:
- Automatic resistivity profiling (ARP);
- Frequency domain electromagnetic induction (Profilers EMP400 and DUAL-EM 642 S) - Gamma-ray spectrometry (compact gamma surveyor – GF instruments);
- X-ray fluorescence (XRF) (Olympus Delta Professional Handheld XRF Analyzers)
The reliability of rapid low-cost methods (XRF) was assessed to design maps of contamination levels so as to guide a subsequent rational sampling scheme of the whole site area (6 ha in this case). XRF data were then compared with the data obtained in the same soil samples with the offical methods.
As regards the evaluation of the suitability of agricultural use of potentially contaminated soils, it is necessary to evaluate the bioavailability of MPT. Extraction with 1 mol L-1 ammonium nitrate is commonly used to determine the readily soluble and bioavailable content of PTMs in soil. In Germany, this procedure is recognized as official standard (DIN 19730, 1997) and is used to assess the risk of transfer of PTMs from the soil to plants in the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV, 1999).
In each area defined as critical on the basis of the prevoius analyses, pairs of soil-vegetation samples have to be set up in order to assess variations in both the bioavailable fraction of PTEs in soil, and the accumulation of contaminants in plant organs. The vegetative sample must be collected from the plants present on the site. If the area is regularly cultivated, field crops must be collected and analysed to evaluate any potential hazards for consumers (EC Reg. 1881/2006); if the area is not cultivated, the wild species have to be sampled to evaluate the possible hazards, assimilating them to forage crops (EC Dir. 32/2002). For the contaminants not governed by legislation, health risk assessment can be made by estimating exposure of the population through the intake of the most commonly used foods in normal diets, of the ISS (2013) study, relating to the tolerable daily intake (TDI).
For monitoring the suitability of a site for the agricultural use the approach to follow is the so-called “worst case”, which means growing a crop which under normal conditions is able to accumulate high concentrations of one or more PTEs in the more polluted hot spots of a site and analysing the edible parts of such crops. If it thus proves safe, we would consider that the site is free of contamination risk of the food chain.
Results and Discussion
SOIL CHARACTERIZATION
Figure 1. Identification of anomalous areas and example of a soil profile in which industrial sludge were found.
Figura 1. Identificazione delle aree anomale ed esempio di trincea in cui sono stati rinvenuti sversamenti di fanghi industriali.
Opening a soil profile also allowed the stratigraphy and the presence of contaminated materials to be analyzed, thus making it possible to choose the layers most representing the form of contamination. For example, from the data gained from “Trench 5” it is evident that the most contaminated layers are only those between 50 and 80 cm: in this case the average sample of the 0-1 m layer, according to current legislation, would have underestimated the level of contamination.
Figure 2 shows that with a measurement campaign conducted with X-ray fluorescence (XRF), it was possible to identify, in a few days’ work, the areas severely contaminated by chromium, on which then to perform direct sampling for analyses with the official methods.
The data obtained with the two methods resulted significantly correlated (R2= 0.93 for Cr and 0.96
for Zn).
EVALUATION OF SUITABILITY TO AGRICULTURAL USE
Single chemical extractions revealed that Zn, although present on average at a lower total concentration, was more mobile and bioavailable than Cr. The readily bioavailable (extracted by 1 mol L-1 NH4NO3; DIN 19730, 1997) amounts of Cr were always much lower than those of Zn,
which in some cases were higher than the trigger value of 2 mg kg-1, adopted by some European countries in agricultural
areas (Carlon, 2007). In the most contaminated soil samples, even the NH4NO3-extracted amounts of Pb, Cu and Cd were
higher than the trigger values adopted by some European countries for agricultural areas (1 mg kg-1 for Cu, 0.1 mg kg-1 for Pb; 0.04 or 0.1 mg kg-1 for Cd). These findings were confirmed by the analyses of vegetables that showed low
concentrations of Cr and high levels of Zn and Cu, but with values lower than the TDI. Instead accumulation of Pb in vegetables represented a higher risk for contamination of food-chain.
Conclusions
The proposed approach resulted much more appropriate and precise than current methods for the characterization of contaminated sites and also more economically sustainable because knowledge of detailed contamination geography enables site-specific remediation techniques to be performed and thus avoids treatment of non-contaminated soils.
The information obtained can then steer direct sampling (core samples to determine concentrations of contaminants with official analytical methods), thus reducing the number of samples and costs of analysis, and increasing the accuracy in delineating site-specific problems (e.g. volume of soil contamination).
The proposed method for assessing the suitability for the agricultural use, confirmed the uselessness of total content of PTM in the soils, highlighting an unexpected risk due to the presence of Pb (whose concentration was lower in this site) while allowing to exclude any risk due to Cr and Zn (whose total concentrations were very higher).
Finally, we should highlight the absolute need to improve existing legislation: the current formulation fails to guarantee proper characterization of the geospatial nature of contaminated sites and hence it is indeed very hard to ensure proper site restoration.
References
BBodSchV, 1999. Bodenschutz- und Altlastenverordnung [Federal Soil Protection and Contaminated Sites Ordinance]. 12 July 1999, Germany.
Carlon C., 2007. Derivation methods of soil screening values in Europe. EC-JRC, Ispra EUR 22805-EN, 306 pp. DIN 19730, 1997. Bodenbeschaffenheit–Extraktion von Spurenelementen mit Ammoniumnitratlösung. Beuth Verlag Berlin.
Fagnano M., 2017 (Ed). Operative handbook for eco-compatible remediation of degraded soils. LIFE-Ecoremed. ISPRA 2009. http://www.isprambiente.gov.it/it/temi/siti-contaminati/analisi-di-rischio.
ISS, 2013. http://www.iss.it/iasa/?lang=1&tipo=41.
Environmental Ministry, 2014. http://www.bonifiche.minambiente.it/contenuti%5Cgruppi%5Caree_agricole% 5CREGOLAMENTO_A_MISE_SALUTE_E_MPAAF.pdf.
Risknet 2.0. http://www.reconnet.net/Risknet%202_download.html.
Figure 2. Levels of chromium as measured by XRF (left) and the official method of ICP-MS (right).
Figura 2. Livelli di cromo determinati con l’XRF (sinistra) e con l’ICP-MS (destra).