sustainability Article
Potential Sources of Anthropogenic Copper Inputs to European Agricultural Soils Panos Panagos 1, *, Cristiano Ballabio 1 , Emanuele Lugato 1 ID , Arwyn Jones 1 , Pasquale Borrelli 2 , Simone Scarpa 1 , Alberto Orgiazzi 1 and Luca Montanarella 1 1
2
*
European Commission, Joint Research Centre, Directorate for Sustainable Resources, IT-21027 Ispra (VA), Italy;
[email protected] (C.B.);
[email protected] (E.L.);
[email protected] (A.J.);
[email protected] (S.S.);
[email protected] (A.O.);
[email protected] (L.M.) Environmental Geosciences Department, University of Basel, CH-4056 Basel, Switzerland;
[email protected] Correspondence:
[email protected]; Tel.: +39-0332-785574
Received: 8 June 2018; Accepted: 5 July 2018; Published: 9 July 2018
Abstract: In the European Union (EU), copper concentration in agricultural soil stems from anthropogenic activities and natural sources (soil and geology). This manuscript reports a statistical comparison of copper concentrations at different levels of administrative units, with a focus on agricultural areas. Anthropogenic sources of diffuse copper contamination include fungicidal treatments, liquid manure (mainly from pigs), sewage sludge, atmospheric deposition, mining activities, local industrial contamination and particles from car brakes. Sales of fungicides in the EU are around 158,000 tonnes annually, a large proportion of which are copper based and used extensively in vineyards and orchards. Around 10 million tonnes of sewage sludge is treated annually in the EU, and 40% of this (which has a high copper content) is used as fertilizer in agriculture. In the EU, 150 million pigs consume more than 6.2 million tonnes of copper through additives in their feed, and most of their liquid manure ends up in agricultural soil. These three sources (sales of fungicides, sewage sludge and copper consumption for pigs feed) depend much on local traditional farming practices. Recent research towards replacing copper spraying in vineyards and policy developments on applying sewage and controlling the feed given to pigs are expected to reduce copper accumulation in agricultural soil. Keywords: fungicides; slurry; sewage sludge; LUCAS; soil contamination; vineyards
1. Introduction Humans have known about copper (Cu) for at least 10,000 years; it has been used extensively across the world by, for example, Egyptians, Greeks, Romans, Aztecs, Balkans and Chinese cultures [1,2]. Copper is used in construction, machinery, energy, transport, electronics, agriculture and, in recent years, for animal nutrition [3]. In the 1880s, a fungicide (based on a mixture of copper sulfate, lime and water) became widely used to control mildew in grapes vines [2]. In the 1950s, the antifungal properties of copper were demonstrated in laboratories [4]. On a global scale, the use of copper in agriculture increased after 1987 [3]. Soil pollution poses a significant risk to human health, as recognized in a recent review of contaminated sites in Europe [5]. In particular, heavy metals from industrial waste can be a source of contamination of soil and, thus, of drinking water, food and animal fodder [6]. The contamination of agricultural soil with inorganic (copper) and organic pesticides is of particular concern for the state
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of our environment and for food safety [7]. Policy organizations such as the Finnish and Swedish Ministries of Environment [8] and Joint Research Centre [9] together with literature findings [10] propose a concentration of 100 mg kg−1 as a threshold for human health consideration for copper 2018,this 10, x FOR PEER REVIEW 2 of 18 in soil.Sustainability However, threshold value of 100 mg kg−1 can vary from country to country [11]. A long-running debate is whether the underlying parent material [12] or agricultural practices [1] are 45 more important driver of copper accumulation in soil. A recent pan-European study by Ballabio et the more important driver of copper accumulation in soil. A recent pan-European study by Ballabio 46 al. developed a regression model to identify the main soil, climate and geological properties that can et a regression model identify the main climatedistribution and geological 47al. developed influence copper distribution [13].toThis regression modelsoil, for copper in the properties European that can copper distribution [13]. This regression for copper European 48 influence Union (EU), based on 21,682 soil samples, found thatmodel high copper levelsdistribution in vineyards in arethe mostly Union (EU), based on 21,682practices soil samples, found that high copper levels in vineyards are mostly related 49 related to management at regional level (including frequent Cu-based fungicide treatments) 50management [13]. In addition to management the regression modelCu-based [13] foundfungicide that main drivers of high to practices at regionalpractices, level (including frequent treatments) [13]. In 51 copper concentrations are also high clay content, high pH and heavy summer rainfall. The influence addition to management practices, the regression model [13] found that main drivers of high copper 52 of geology are is limited to certain materials tephra and acidic volcanic rocks (high copper concentrations also high clayparent content, highsuch pHasand heavy summer rainfall. The influence of 53 concentration) while sedimentary rocks and fluvial deposits have lower copper levels [13]. The geology is limited to certain parent materials such as tephra and acidic volcanic rocks (high copper 54 present paper follows that study [13], by investigating the anthropogenic activities that lead to copper concentration) while sedimentary rocks and fluvial deposits have lower copper levels [13]. The 55 accumulation, with a specific focus on agriculture. present paper follows study [13], by(1) investigating activities that lead to copper 56 The objectivesthat of this study were: to investigatethe theanthropogenic anthropogenic factors influencing copper accumulation, withinaagricultural specific focus on agriculture. 57 accumulation topsoils; (2) to link land use and agricultural management with copper 58 The concentration; (3) to identify which of the EU the mayanthropogenic be most affected.factors It was not among thecopper objectives and of this study were: (1) areas to investigate influencing 59 objectivesin ofagricultural this study to challenge or regional study has been performed with a with greater accumulation topsoils;any (2)local to link land use andthat agricultural management copper 60 number of soil samples or more precise knowledge of drivers influencing copper values at local scale. concentration; and (3) to identify which areas of the EU may be most affected. It was not among the objectives of this study to challenge any local or regional study that has been performed with a greater 61 2. Materials and Methods number of soil samples or more precise knowledge of drivers influencing copper values at local scale.
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2.1. Geodatabases
2. Materials and Methods
63 The study used the topsoil database from the Land Use/Land Cover Area frame Survey (LUCAS) 64 [14] (known 2.1. Geodatabases as LUCAS Topsoil), which contains records of the physical and chemical properties of 65 21,682 soil samples in 27 EU Member States (excluding Croatia) (Figure 1). The laboratory analysis of study used the topsoil database from copper) the Land Cover Areaincluding frame Survey 66 The the physical and chemical properties (including usedUse/Land standard ISO methods a 67 validation process [15]. The soil samples were taken contains from the uppermost 20 the cm of surveyedand soil and (LUCAS) [14] (known as LUCAS Topsoil), which records of physical chemical 68 moreof details onsoil bothsamples the LUCAS samplingStates scheme and the analysis can(Figure be found recently properties 21,682 in 27topsoil EU Member (excluding Croatia) 1).inThe laboratory 69 published papers [14–16]. analysis of the physical and chemical properties (including copper) used standard ISO methods 70 Surveyors also noted the land cover type (e.g., cropland, forest, and grassland). The LUCAS including a validation process [15]. The soil samples were taken from the uppermost 20 cm of 71 topsoil survey focused mainly on agricultural areas, with cropland samples constituting 45% of the surveyed soil and more details on both the LUCAS topsoil sampling scheme and the analysis can be 72 total (5% of which are located in permanent crops), while grassland and forest samples make up found in recently published papers [14–16]. 73 22.9% and 27.2%, respectively.
74 75 Figure 1. The LUCAS Topsoil database and the links with other datasets (land use and administrative Figure 1. The LUCAS Topsoil database and the links with other datasets (land use and 76 units). administrative units).
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Surveyors also noted the land cover type (e.g., cropland, forest, and grassland). The LUCAS topsoil survey focused mainly on agricultural areas, with cropland samples constituting 45% of the total (5% of which are located in permanent crops), while grassland and forest samples make up 22.9% and 27.2%, respectively. LUCAS Topsoil is the most comprehensive harmonized soil database for the EU, as it has 13 categories of physical and chemical properties, analysis of 12 heavy metals, and a visible and near infrared spectral library (Figure 1). In addition, LUCAS Topsoil is up to date, as it uses sampling data from 2009 and 2012. LUCAS Topsoil can be linked with other georeferenced data sources, such as the LUCAS land cover survey and the European Union administrative units (Figure 1). The LUCAS land cover survey is a point survey organized by the statistical service of the European Commission (EUROSTAT) every three years [17]. The surveyors visit approximately 270,000 locations and recording the land cover type (forest, grassland, arable, etc.), land use and other landscape features [14]. The Nomenclature of Territorial Units for Statistics (NUTS) is the official EU database for delineating administrative units at different levels (country, region, province and municipality). The NUTS2 geographical regions are often used for developing regional policies and therefore many environmental indicators are presented at this scale. Across the 27 EU Member States, there are 285 NUTS2 administrative units, with areas ranging from 13 km2 to 165,075 km2 and populations of 0.8–3 million inhabitants [18]. 2.2. Statistical Analysis per Geographical Units and Land Cover Types For the copper attribute of the LUCAS Topsoil database, we performed a statistical analysis to assess the mean, median, skewness and percentiles. The copper data were aggregated according to different administrative units such as countries and regions. At country level, we provide the mean, median and the interquartile range (IQR). The IQR is the measure where the average 50% of the values are located and shows where the bulk of an attribute’s value lies. The data are also analyzed by land cover groups aggregated on annual croplands, permanent crops, forests and grasslands. As the objective of the paper is to understand how management practices are influencing copper distribution, we focus on annual and permanent croplands. 2.3. Modeling Copper Use in Relation to Fungicides Sales The EUROSTAT agri-environmental indicator “consumption of pesticides” contains data from EU Member States on the sales of “fungicides and bactericides” [19]. As information on actual applications are not readily available, the data for this indicator may be considered a proxy for copper use in these countries. We estimated the mean consumption as tonnes per country based on the statistics available for 2011–2015 (mean value). According to the EU statistics, 63% of all fungicides in the EU (total 158,800 tonnes) are sold in three countries (Italy, France and Spain), each of which consumes approximately 30,000–37,000 tonnes of fungicides per year. Based on CORINE land cover data for 2012 [20], we estimated the number of hectares under each different land cover in all Member States. The permanent crop cover (i.e. vineyards, olive groves and fruit trees) was around 10.3 million hectares, which corresponds to 6.4% of the total agricultural land of the EU. We developed a model to predict the average fungicide consumption per hectare at EU level in both permanent crops and arable lands. The model consumption rate is “forced” by the sales of fungicides and based on the following formula: ESFi = PCi * PCC + ALi * ALC
(1)
For a given Member State i, the estimated sales of fungicides (ESFi ) were obtained by adding up the fungicides applied to permanent crops (PCi : the hectares of permanent crops in Member State i; and PCC: the rate of permanent crops consumption) and the fungicides applied to arable land (ALi :
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the hectares of arable land in Member State i; and ALC: the rate of arable lands consumption). The model distinguishes between the consumption of fungicides in permanent crops and that in arable lands. The sum of estimated sales of fungicides in the EU should be close to the mean consumption of fungicides available from Eurostat statistics (approximately 158,800 tonnes). Sustainability 2018, 10, x FOR PEER REVIEW 2.4. Modeling the Copper Concentration in Relation to Distance from Mines
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123 The The possible influenceofofmining mining activities topsoil copper levelslevels was investigated using theusing possible influence activitiesonon topsoil copper was investigated 124 mines database databasetaken taken from the Minerals4EU platform[21] (http://minerals4eu.brgmthe mines from the Minerals4EU platform [21] (http://minerals4eu.brgm-rec.fr/ 125 rec.fr/minerals4EU/). The database includes 1080 identified copper mines; of these, 217 haveavailable available data minerals4EU/). The database includes 1080 identified copper mines; of these, 217 have 126 data on past production and activity status. The regression model fits the copper concentration in on past production and activity status. The regression model fits the copper concentration in relation 127 relation to distance from the copper mines in European Union. to distance from the copper mines in European Union.
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3. Results
3. Results
129 The section 3.1 provides the main descriptive statistics on copper from the LUCAS Topsoil Section 3.1the provides thedescribes main descriptive statistics on copper fromby theadministrative LUCAS Topsoil 130 The database. Then, section 3.2 the geographical distribution of copper database. Then, the Section 3.2 describes the geographical distribution of copper by 131 unit. The copper distribution in forests and grasslands is described briefly, followed byadministrative a detailed unit. analysis The copper distribution forests and grasslands is described briefly, followed by a isdetailed 132 of croplands, with ain focus on permanent crops. The copper concentration in vineyards of 133 great because of athe elevated values here crops. compared otherconcentration croplands. analysis ofconcern croplands, with focus on permanent Thewith copper in vineyards is of great concern because of the elevated values here compared with other croplands.
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3.1. Descriptive Statistics
3.1. Descriptive Statistics 135 The mean copper concentration from the LUCAS Topsoil database is 16.86 mg kg-1 and the 50th
136 The percentile 11.57 mg kg-1, with a positive skewness. of the total samples have copper −1 aand meaniscopper concentration from the LUCASAlmost Topsoil19% database is 16.86 mg kg the 50th -1, and 44% of samples have a concentration of less than 10 mg kg-1 137 concentration of less than 5 mg kg − 1 percentile is 11.57 mg kg , with a positive skewness. Almost 19% of-1 the total samples have a copper 138 (Figure 2). The majority of samples (55%) fall in the range 5–20 mg kg . Finally, three quarters of the concentration of less than 5 mg kg−1 , and 44% of samples-1have a concentration of less than 10 mg kg−1 139 samples have a Cu concentration of less than 20 mg kg . Considering−that the copper threshold at 1 . Finally, three quarters of the (Figure 2). The majority of samples (55%) in the range 5–20mg mg -1[8,9], 140 which soil is considered to be at risk forfall human health is 100 kgkg only 1.1% of the samples samples have Cu concentration of less than 20 mg kg−1 . Considering that the copper threshold at 141 should be afurther assessed as being at risk. which soil is considered to be at risk for human health is 100 mg kg−1 [8,9], only 1.1% of the samples should be further assessed as being at risk. 142
143 144
Figure Numberofofsamples samples per per Cu category. Figure 2. 2. Number Cuconcentration concentration category.
145
3.2. Overview of Geographical Distribution of Copper by Administrative Unit
146 147 148 149
At country level, Cyprus is estimated to have the highest mean copper concentration in topsoil (53.41 mg kg-1), followed by Italy (41.22 mg kg-1), Malta (33.11 mg kg-1), Greece (27.97 mg kg-1), Bulgaria (27.71 mg kg-1) and Romania (23.38 mg kg-1). The lowest mean values are found in the Baltic states, Poland, Sweden and Denmark (all less than 10 mg kg-1). In all countries, the median values are
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150 lower than the mean values, as the distribution is positively-skewed due to many low Cu values and 151 few outliers. 3.2. Overview of Geographical Distribution of Copper by Administrative Unit 152 As for the mean, the highest median Cu concentration is found in Cyprus (37.5 mg kg-1), followed 153 At by Italy (30.86 mgCyprus kg-1), Malta (27.43 mg to kg-1have ), Greece mgmean kg-1) and Bulgaria (22.15 mg kg-1in ). topsoil country level, is estimated the (22.91 highest copper concentration -1 − 1 − 1 − 1 154 mg Thekg lowest median Cuby concentration is found (4.36 mg kgmg ), followed by Latvia (4.95 mg (53.41 ), followed Italy (41.22 mg kgin Poland ), Malta (33.11 kg ), Greece (27.97 mg kg−1 ), 155 kg-1), Sweden (5.76 kg–1), Estonia (5.95 mg kg–1), Lithuania (7.62 mg kg–1), Finland (8.55 mg kg-1) Bulgaria (27.71 mg kg−1mg ) and Romania (23.38 mg kg−1 ). The lowest mean values are found in the 156 and Denmark (8.79 mg kg–1) (Figure 3). Baltic states, Poland, Sweden and Denmark (all less than 10 mg kg−1 ). In all countries, the median 157 High Cu concentration in Cyprus was also confirmed by Zissimos et al. [22] and is closely related values loweractivities. than theInmean values, as the positively-skewed tothan many 158 are to mining France, the median Cudistribution concentrationis(12.11 mg kg -1) is muchdue lower the low Cu -1 values outliers. 159 and meanfew (19.23 mg kg ) because there are few outliers (Figure 3). Similarly, Portugal has a wide 160 Asdispersion of values high variability. Some countries have is similar mean and median values for the mean, thewith highest median Cu concentration found in Cyprus (37.5 mg kg−1 ), -1 -1 1 ), Malta −1 ), Greece 1 ) and 161 because there(30.86 are no outliers: Ireland (mean(27.43 17.49 mg , median 16.11 mg kg ), Belgium 15.9 followed by Italy mg kg− mgkgkg (22.91 mg kg−(mean Bulgaria -1, median 14.62 mg kg-1) and Hungary (mean 15.39 mg kg-1, median 14.12 mg kg -1). 162 mg kg− 1 − 1 (22.15 mg kg ). The lowest median Cu concentration is found in Poland (4.36 mg kg ), followed 163 In Figure 3, horizontal line indicates values 1.5 times the −IQR. According to this −1 the 1 ), Lithuania by (4.95 mg kg ), Sweden (5.76 mg concentrations kg−1 ), Estonia mg kg Slovakia, mg kg−1 ), 164Latvia interpretation, the highest middle quartile are(5.95 in Romania, Belgium(7.62 and the 1 ) and Denmark (8.79 mg kg−1 ) (Figure 3). Finland (8.55 mgwith kg−the 165 countries lowest median values (Figure 3).
166 167 Figure 3. Figure 3. Statistics Cu concentration (mgkg kg−-11))by The right column showsshows the number of Statistics of Cuofconcentration (mg bycountry. country. The right column the number of 168 samples per country. The boxplot is the interquartile range (IQR) expressed as the difference between samples per country. The boxplot is the interquartile range (IQR) expressed as the difference between 169 the 25th (Q1) and 75th percentiles (Q3); the left line is the result of the operation: Q1 - 1.5 * IQR and (Q1)line and 75th percentiles (Q3); the left line is the result of the operation: Q1 − 1.5 * IQR and 170 the 25thright is the result of the operation: Q3 + 1.5 * IQR. Dots outside the lines are considered outliers. right line is the result of the operation: Q3 + 1.5 * IQR. Dots outside the lines are considered outliers.
171 A simple geographic distribution of Cu concentration can be assessed using the mean value for 172 each NUTS2 region (Figure 4). For convenience, the term “region” is used to describe this level of High Cu concentration in Cyprus was also confirmed by Zissimos et al. [22] and is closely related 173 geography. For 33 NUTS2 regions (mainly metropolitan cities), we had no soil samples, while for 19 to mining activities. In France, the median Cu concentration (12.11 mg kg−1 ) is much lower than 174 other regions we had fewer than five LUCAS samples because of reduced sampling coverage (they −1 because there are few outliers (Figure 3). Similarly, Portugal has a wide the mg 175mean are(19.23 denoted as kg “few )samples” on the legend of Figure 4). For 63 regions, we had >100 available dispersion of values with high variability. Some and, countries similar median 176 samples; for 69 regions, we had 50–100 samples; for the have remaining 101 mean regions,and we had 5–50 values − 1 − 1 177 samples. because there are no outliers: Ireland (mean 17.49 mg kg , median 16.11 mg kg ), Belgium (mean 15.9 mg kg−1 , median 14.62 mg kg−1 ) and Hungary (mean 15.39 mg kg−1 , median 14.12 mg kg−1 ). In Figure 3, the horizontal line indicates values 1.5 times the IQR. According to this interpretation, the highest middle quartile concentrations are in Romania, Slovakia, Belgium and the countries with the lowest median values (Figure 3). A simple geographic distribution of Cu concentration can be assessed using the mean value for each NUTS2 region (Figure 4). For convenience, the term “region” is used to describe this level of geography. For 33 NUTS2 regions (mainly metropolitan cities), we had no soil samples, while for 19 other regions we had fewer than five LUCAS samples because of reduced sampling coverage (they are denoted as “few samples” on the legend of Figure 4). For 63 regions, we had >100 available samples; for 69 regions, we had 50–100 samples; and, for the remaining 101 regions, we had 5–50 samples.
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−1 ) by NUTS2 region in EU-27. FigureFigure 4. Mean copper distribution 4. Mean copper distribution(mg (mg kg kg-1) by NUTS2 region in EU-27.
180 According to this regional analysis, the mean Cu concentration in topsoil is higher than 50 mg to this regional analysis, the mean Cu concentration in topsoil is higher than 181 According kg-1 in Trentino-Alto Adige, Emilia-Romagna and Lazio in Italy (and Veneto has a mean value of 49 −1 in Trentino-Alto Adige, Emilia-Romagna and Lazio in Italy (and Veneto has a mean value 50 mg kg -1 182 mg kg ); in the Languedoc-Roussillon region in France; and in Cyprus (the locations mentioned are of 49 mgreported kg−1 ); in Supplement the Languedoc-Roussillon in France; and in Cyprus (the locations mentioned 183 Figure S1). In the region other Italian regions, Malta, west Greece, east Bulgaria, -1. 184reported Catalonia (Spain) and Algarve theother meanItalian Cu concentration is between 30Greece, and 50 mg kgBulgaria, are in Supplement Figure(Portugal), S1). In the regions, Malta, west east 185 By (Spain) contrast, and the majority regions in Northern andCu Eastern Europe have concentrations Catalonia Algarveof(Portugal), the mean concentration isCu between 30 andbelow 50 mg kg−1 . 186 20 mg kg-1 (the locations mentioned are reported in Supplement Figure S1). By contrast, the majority of regions in Northern and Eastern Europe have Cu concentrations below 20 mg kg−1 (the locations mentioned are reported in Supplement Figure S1). 3.3. Copper Distribution in Forests and Grasslands For the EU, the mean Cu concentration in grasslands is 18.23 mg kg−1 , while in forests it is significantly lower (11.98 mg kg−1 ). In comparison by countries (Figure 5), the mean Cu concentration in croplands or permanent crops is higher than forests or grasslands with the exception of Cyprus
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and Malta. Broadleaf forests (e.g., acacia, beech, oak and eucalyptus) have almost double the mean Cu concentration of coniferous forests (e.g., spruce, hemlock, pine and fir): 17.66 mg kg−1 and 9.37 mg kg−1 , respectively. Compared with a coniferous forest, a broadleaf wood has a very thin forest floor, so the deposited Cu tends to be retained mostly in the top mineral layer [23]. The highest mean Cu concentration in broadleaf forests is in Italy, with 42.65 mg kg−1 , followed by Romania with 26.72 mg kg−1 and Bulgaria with 24.17 mg kg−1 . In Sweden, Germany, Finland and Spain, the mean Sustainability is 2018, 10, x FOR PEER(50 ha-1gyear found in Italy, Germany, − 1 − 1 ) were found in Italy, Germany, noted that the highest copper deposition rates (>50 g ha year 387 England and Wales. The copper industry in Europe is economically important, employing more than England and Wales. The copper industry in Europe is economically important, employing more than 50,000 people directly and indirectly, sustaining millions of jobs [53]. Furthermore, the sector has made much progress in reducing heavy metal emissions [41,54]. In addition, particles from the wear of automobile brakes are a significant source of copper emissions [48]. Brake pads can contain copper, zinc and brass. In a study of pollution in roadside soil, the copper concentration in soil closer to highways (
