Zeolitized tuffs in pedotechniques to improve soil resilience against the impact of treatment by municipal sewage: balance of nutrient and noxious cations

Abstract

Two zeolitized tuffs (ZTs), viz. a Neapolitan yellow tuff (NYT) and a clinoptilolite-bearing tuff (ZCL), were tested as pedotechnical materials to improve soil resilience against the impact of treatment by a ‘dirty’ municipal sewage system (DSW). Soils (surface horizon) were a sandy, alkaline Entisol (Typic Xeropsamment), and a sandy-loam, sub-acidic Alfisol (Ultic Palexeralf). Results showed that the presence of ZTs resulted in several favourable effects. Electrical conductivity (EC) decreased and pH was buffered. Ammonium was selectively taken up from the DSW, making the zeolitized tuffs almost saturated by NH4+, by exchanging both beneficial cations, such as K+ and Ca2+, thus improving their potential availability to plants, and undesirable cations such as Na+, thereby hindering the exchangeable sodium percentage (ESP) increase and concurrent soil salinization-alkalinization. At the same time, NH4+ was stored as a potentially slow-release nitrogen fertilizer. The mobility of Pb, Cu and Zn dropped off to a large extent. NYT produced the best effects, and the Entisol gained the greatest benefit from treatments.

Issues concerning soils treated with wastewater: Pedotechnical management with zeolitized tuffs as an option for turning N and P pollutants into potential fertilizers

“…Conversely, NH 4 + -N concentration was always significantly greater than that initially measured in the respective DMW samples (Tables 3-5). As seen in a previous research project [16] the behavior of NH 4 + -N was outwardly odd, depending greatly on both the type and amount of ZT present in the samples. More specifically: (i) mean [NH 4 + ] in SSs was greater than DMW and, on average, greater in OT than in CV suspensions; (ii) mean [NH 4 + ] in ZT suspensions was greater than the respective DMWs and, on average, greater in ZCL than in NYT suspensions; and (iii) SSs/ZT samples showed trends ranging from SSs alone to ZTs alone, approaching the latter as ZT content in SSs/ZTs increased.…”

“…Indeed, it is well known that both clinoptilolite [42] and NYT [43] show pronounced selectivity for ammonium. Furthermore, in addition to phillipsite and chabazite, NYT also hosts smectite, which is a phyllosilicate clay mineral with a high affinity for ammonium [16]. As already argued by Capra et al [16], it is highly improbable that all the effects observed are simply a consequence of some, or one, predominant factors.…”

“…In order to present an accurate, comprehensive picture of nitrogen behavior, the discussion dealing with N forms also considers the data on NH 4 + -N obtained in the previous research [16]. With the sole exception of NH 4 + -N, the concentration of both NO 3 À -N and N total was generally lower than that initially measured in the respective DMW samples (Tables 3-5).…”

“…From this perspective, Buondonno et al [15] and Capra et al [16] extensively reviewed the chemical-physical properties of zeolitized tuffs (ZTs) as suitable materials to be exploited as soil amendments [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] and to be used to restore degraded and polluted soils [32][33][34][35][36][37]. These investigations showed the potential use of ZT as exchange conditioners, added directly to the soil to improve soil resilience, making it durable against the impacts of irrigation using sewage and wastewater [15,16]. Indeed, while a number of studies have been carried out on the use of ZTs either in agriculture as soil amendment or as a filter/ barrier in WW treatment, the combined perspective for the exploitation of ZTs as pedotechnical amendment for soils subjected to repeated/long-term treatments with municipal sewage and wastewater has only recently been illustrated [15,16].…”

“…These investigations showed the potential use of ZT as exchange conditioners, added directly to the soil to improve soil resilience, making it durable against the impacts of irrigation using sewage and wastewater [15,16]. Indeed, while a number of studies have been carried out on the use of ZTs either in agriculture as soil amendment or as a filter/ barrier in WW treatment, the combined perspective for the exploitation of ZTs as pedotechnical amendment for soils subjected to repeated/long-term treatments with municipal sewage and wastewater has only recently been illustrated [15,16]. The results of these investigations have revealed that soils treated with WW can benefit from several advantages obtained through the addition of [phillipsite + chabazite]-or clinoptilolite-bearing tuffs.…”