## 1 Introduction
In the face of this, it is likely that there will not be a similar increase in land use for agricultural purposes (primarily cereals) if we consider that over almost 60 years, from 1961 to 2018, in a context of growth of almost 240% of cereal production and around 145% of the population, there was an increase in land use for cereals of only almost 12.5% [3]. Moreover, drought and soil salinity are the main factors responsible for reducing yield. Additionally, the COVID-19 pandemic has negatively impacted traditional agriculture due to border closures, quarantines, and disruptions to supply chains. From this picture emerges the need both to increase crop productivity and to have it nearer by using innovative approaches, and indoor farming could be a significant help. In this context, chemical-environmental parameters such as pH, conductivity, leaching of heavy metals, antibacterial properties, and cytotoxicity become of primary importance for those materials engineered for the applications described and which involve an important handling, with possible storage and use in confined environments. The pH is a scale of measurement of the acidity or basicity of an aqueous solution, while the electrical conductivity is directly linked to the presence of salts in solution, the dissociation of which generates positive and negative ions which are responsible for the transport of electrical energy when the solution is subjected to an electric field. They are both constitute very important data since the agricultural purpose for which the manufactured products are destined requires that values of these quantities are respected so as not to interfere with the growth of plants. A material intended for crops must in fact have a pH as close as possible to neutrality in order to be compatible with almost all plants. Agricultural soils considered neutral have pH values ranging between 6.8 and 7.3, and in them the absorption of nutrients is maximized. In general, the widest acceptable range for plants is that which goes from 5.5 to 8.5; for values beyond these, they would hardly be able to adapt. The measurement of electrical conductivity, on the other hand, is used to determine the presence of salts in the soil by measuring their presence in the saturated aqueous extract taken from it. The weak point of this technique, however, is the ability to indicate the quantity but not the quality of the salts present, being a non-specific parameter. Indeed, it is not possible to know whether it is given by a useful salt, such as calcium nitrate, or by a harmful one, such as sodium chloride. In general, however, too high conductivity values are dangerous for plants because the greater presence of salts implies greater difficulty in the absorption of water by the root system of plant organisms. Conductivity is expressed in dS/m, referring to the saturated extract of the soil. Ideal values for each type of crop are those that do not exceed 2 dS/m, while the danger of crop depression increases up to 4 dS/m. Beyond this value, any type of crop, even the most tolerant, risks deterioration. The tests carried out are regulated by the UNI EN 13037: 2012 (pH) (\"UNI EN 13037\" 2012) and UNI EN 13038: 2012 (conductivity) (\"UNI EN 13038\" 2012) standards. The relationship between soil and water in the extraction determines how much the salts contained in the soil are diluted in the water and therefore the EC value. The result can therefore be evaluated only by knowing the extraction ratio. The most commonly used extractions in Italy are: saturated pasta (impractical execution and not always used), the ratio 1:2 (soil/water), and the ratio 1:5 (soil/water). The effect of heavy metal pollution on plant organisms induces a stressful condition, and thus influence the processes of growth, development, and productivity. Plants present articulated and dynamic systems of response to stimuli from stresses that are more complex than those found in animals.