Introduction
Soil is an important part of the natural environment and its effect on wine quality and grape composition is highly complex because it has an influence on mineral nutrition in the grapevine, the uptake of water, root depth and rhizosphere temperature. In this respect, analysis of elements could be used (Greenough et al. 2005) since it is believed that these chemical elements present in the soil can be transferred to the plant and subsequently to the harvested grapes (Protano and Rossi 2014). The topic, however, is now being discussed further because it has not been demonstrated how these elements act on the sensory attributes of wines (Maltman 2013).
In viticulture, micronutrient deficiencies are corrected by the addition of trace elements that are essential for plant growth, e.g., Cu, Zn, Fe, Mn and B. Treatment of plants with fungicides, pesticides and herbicides also inputs chemicals into the vineyard soil. However, the presence of trace elements of natural origin in grapes and wine is mainly dependent on the mineralogical content of the soils, which are developed from various types of rocks.
Trace elements, including potentially toxic elements (PTEs, Hooda 2010), are found naturally in soils and they can also be introduced and accumulated due to anthropogenic influences in agricultural, urban and industrial areas. The extensive use of fertilizers and fungicides (Kment et al. 2005; Komárek et al. 2010; Geana et al. 2013; Wightwick et al. 2013) leads to the accumulation of trace elements in vineyard soils and the bioavailability of such elements may be increased for plants. Other sources of trace elements include industrial pollution of sites (Moreno et al. 2007; Pohl 2007; Geana et al. 2013). It is not surprising, therefore, that numerous studies on viticultural areas have focused on the identification of the main macro- and microelements in the soil, grapes and wine (Huzum et al. 2012; Bora et al. 2013, 2015; Geana et al. 2013; Ungureanu et al. 2017).
The probability of anthropogenic contamination and the toxicological health risks associated with soil pollution can be evaluated by considering various indices (Mehr et al. 2017). Indeed, trace element data can be used, through predictive indices (such as the enrichment factor EF or Geocumulation Index, I-geo), to evaluate risks based on their total contents and toxicity (Gu et al. 2016; Müller 1969). On the other hand, the bioaccumulation coefficient (BAC) provides information about the capacity of a plant to uptake nutrients and this parameter can be measured in any plant tissue (root, leaf or fruit) (Kabata-Pendias 2001).
Although terroir studies have generally focused on heavily populated regions, a few studies have been conducted in smaller rural locations. In this respect, the objectives of this study were to provide an overview of the contents of some major and trace elements (including PTEs) in vineyard soils in a small and traditional rural location, namely Alcubillas (a small municipality of La Mancha, Central Spain), with special attention paid to those elements that under particular environmental circumstances may become toxic. The specific goals were (i) to provide a database for the studied macro- and microelements, (ii) to establish an ecological risk assessment for some PTEs in order to contribute to sustainable management of this agricultural area and (iii) to determine if certain elements are present in significant quantities in grapevine leaves in relation to soil composition.