Mauricio Molina-Roco

Soil redox oscillations strongly regulate the speciation and mobility of trace metals, yet little is known about how engineered nanoparticles (ENPs) interact with these dynamic conditions in copper-enriched Mollisols. In this study, we evaluated the effects of CuO, Fe, and Ag nanoparticles (CuONPs, FeNPs, and AgNPs) on soil suspension chemistry (pH, Eh, electrical conductivity) and on Cu2+ dynamics (free and complexed fractions) during oxic–suboxic cycles. The results revealed contrasting functional roles: CuONPs acted as a sustained source of Cu2+, mobilising up to 55% of the non-labile pool and showing limited reversibility under reducing conditions. FeNPs did not contribute Cu directly but modulated redox-driven pulses, releasing and re-adsorbing Cu2+ episodically in synchrony with Eh fluctuations. AgNPs exhibited minimal direct impact on Cu2+ mobilisation, although their potential antimicrobial effects suggest indirect influences on redox-sensitive pathways. Mass balance analysis confirmed that soils with lower organic matter and buffering capacity (MA) were more vulnerable to Cu2+ accumulation, while higher organic matter soils (MB) attenuated release through complexation. These findings provide mechanistic insight into how ENPs interact with redox dynamics, highlighting the cumulative risk of CuONPs and the episodic behaviour of FeNPs. The results underscore the need to integrate redox variability into risk assessment frameworks for the use of nanoparticles in agricultural soils.

Soil redox oscillations strongly regulate the speciation and mobility of trace metals, yet little is known about how engineered nanoparticles (ENPs) interact with these dynamic conditions in copper-enriched Mollisols. In this study, we evaluated the effects of CuO, Fe, and Ag nanoparticles (CuONPs, FeNPs, and AgNPs) on soil suspension chemistry (pH, Eh, electrical conductivity) and on Cu2+ dynamics (free and complexed fractions) during oxic–suboxic cycles. The results revealed contrasting functional roles: CuONPs acted as a sustained source of Cu2+, mobilising up to 55% of the non-labile pool and showing limited reversibility under reducing conditions. FeNPs did not contribute Cu directly but modulated redox-driven pulses, releasing and re-adsorbing Cu2+ episodically in synchrony with Eh fluctuations. AgNPs exhibited minimal direct impact on Cu2+ mobilisation, although their potential antimicrobial effects suggest indirect influences on redox-sensitive pathways. Mass balance analysis confirmed that soils with lower organic matter and buffering capacity (MA) were more vulnerable to Cu2+ accumulation, while higher organic matter soils (MB) attenuated release through complexation. These findings provide mechanistic insight into how ENPs interact with redox dynamics, highlighting the cumulative risk of CuONPs and the episodic behaviour of FeNPs. The results underscore the need to integrate redox variability into risk assessment frameworks for the use of nanoparticles in agricultural soils.

Water quality is a fundamental aspect of public health and environmental sustainability. In rural areas, the physicochemical and microbiological quality of drinking water depends not only on hydrogeological conditions but also on anthropogenic activities carried out on the surface of the basin. This study aimed to identify natural and anthropogenic influences related to the quality of drinking water in rural areas of southern Chile. In order to perform this, six rural drinking water systems were evaluated. A total of two types of catchment sources (groundwater and surface water) that were located in a longitudinal gradient were used, where coverage and sequences of rocks and soils could be differentiated. The results show that the water delivered by the majority of rural drinking water systems studied was of good quality, meeting the standards of Chilean and international regulations. No fecal coliforms or Escherichia coli were recorded. In addition, we recorded that turbidity, color, pH, concentration of total dissolved solids and fecal coliforms showed significant differences between groundwater and surface water. We also recorded that in two groundwater systems, iron and manganese levels slightly exceeded the regulations, endangering the acceptability of the water. These increases can be related to the natural origins of the metals, linked to the presence of oxides in Andisol- and Utisol-type volcanic soils.

The progressive influx of engineered nanoparticles (ENPs) into the soil matrix catalyses a fundamental transformation in the equilibrium dynamics between the soil and the edaphic solution. This all-encompassing investigation is geared towards unravelling the implications of an array of ENP types, diverse dosages and varying incubation durations on the kinetics governing Cd²⁺ sorption within Ultisol soils. These soils have been subjected to detailed characterizations probing their textural and physicochemical attributes in conjunction with an exhaustive exploration of ENP composition, structure and morphology. To decipher the intricate nuances of kinetics, discrete segments of Ultisol soils were subjected to isolated systems involving ENP dosages of 20 and 500 mg ENPs·kg⁻¹ (AgNPs, CuNPs and FeNPs) across intervals of 1, 3 and 6 months. The comprehensive kinetic parameters were unveiled by applying the pseudo-first-order and pseudo-second-order models. At the same time, the underlying sorption mechanisms were studied via the intra-particle diffusion model. This study underscores the substantial impact of this substrate on the kinetic behaviours of contaminants such as Cd, emphasizing the need for its consideration in soil-linked economic activities and regulatory frameworks to optimize resource management.

The frequent use of phosphorus (P) fertilisers accompanied by nitrogen and potassium sources may lead to a serious long-term environmental issue because of the presence of potentially hazardous trace metals (TM) in P fertilisers and unknown effects on the TM chemical fractions in agricultural soils. A 16-month-long column experiment was conducted to investigate the mobility and chemical forms of Cd, Cu, Cr, Ni, and Zn introduced into a Mollisol and an Andisol through surface incorporation (0–2 cm) of triple superphosphate (TSP) fertiliser. The effects of urea and potassium chloride (KCl) applications were investigated as well. After 15 cycles of 300-mm irrigation, TSP addition increased the 4 M HNO₃ extractable TM concentration in the upper (0–5 cm) section of soils. Beyond this depth, metals showed no significant mobility, with minimal leaching losses (< 1.9%, 25-cm depth). The TM chemical forms in the 0–5 cm section were significantly (p < 0.01) affected by the soil type and fertilisers addition. Cadmium, Ni, and Zn were the elements which appeared in a larger proportion (up to 30%) in the most labile fraction (KNO₃ extractable) in fertilised soils. The impact of urea depended on the nitrification-related changes in soil pH, while fertilisation with KCl tended to increase the KNO₃ fraction of most metals probably due to K⁺ exchange reactions. Chromium remained minimally affected by the urea and KCl applications since this contaminant is strongly bound to the less labile solid phases. The low mobility of TM was governed mainly by their interaction with the solid phases rather than by their speciation at soil pH. The mass balance showed that the geochemical processes underwent in time by the P fertiliser increased the amount of TM extracted by the chemical fractionation scheme, therefore the reaction period of TSP with soil particles should be taken into account for evaluating TM availability. Long-term soil fertilisation could inadvertently contribute to an increased concentration and availability of these P fertilisers-born contaminants in the cultivated layer of acidic soils.