Sorption mechanisms of zinc in different clay minerals and soil systems as influenced by various natural ligands

The bioavailability and fate of Zinc (Zn) in soils is influenced by reactions occurring at the water-mineral interface. Understanding Zn interaction with mineral surfaces is essential to the understanding of Zn fate and toxicity. In this study, adsorption experiments investigated the impact of ligands and pH on the adsorption of Zn to mineral surfaces. X-Ray Absorption Fine Structure Spectroscopy (XAFS) was used to elucidate the adsorption mechanisms of Zn to mineral surfaces as impacted by ligands. Impact of ligands on Zn adsorption was dependent on mineral type and pH of the system. XAFS analysis showed that adsorption mechanisms of Zn were impacted by pH and ligand presence. In the ferrihydrite system, Zn adsorption was enhanced in presence of citrate and phosphate (PO4), reduced in presence desferrioxamine (DFO-B), and reduced in presence of humic acid (HA) at pH\u3e6.0. XAFS analysis showed that Zn formed strong linkages with high affinity edge sites of ferrihydrite in the control and in presence of enhancing ligands (citrate and PO4), whereas formed weaker, low affinity linkages in presence of supressing ligands (DFO-B and HA). From an environmental perspective, Zn was more likely to be desorbed from the ferrihydrite surface in the presence HA and DFO-B. In the kaolinite system, Zn adsorption was reduced in presence of citrate and DFO-B, and increased in presence of HA. Zn formed inner sphere complexes at pH 5.5 in the control and in presence of ligands. At pH 7.5, a Zn-Al layered double hydroxide was formed in the control, that was absent in presence of any ligand, suggesting that ligands suppress the formation of Zn-Al LDH in kaolinite. In the mixed ferrihydrite-gibbsite system, Zn adsorption was enhanced in presence of all ligands, excluding DFO-B. Adsorption mechanisms of Zn to ferrihydrite were unaffected by ligand presence. The impact of organic matter (OM) degradation on heavy metal distribution in sewage sludge was investigated. Cu, Pb and As were bond with the OM fraction of sludge, whereas Zn was bond to Fe/Mn oxide fraction. OM degradation increased mobility and bioavailability of Zn and Cu, whereas it had less impact on Pb and As

Fate and Distribution of Heavy Metals in Wastewater Irrigated Calcareous Soils

Accumulation of heavy metals in Jordanian soils irrigated with treated wastewater threatens agricultural sustainability. This study was carried out to investigate the environmental fate of Zn, Ni, and Cd in calcareous soils irrigated with treated wastewater and to elucidate the impact of hydrous ferric oxide (HFO) amendment on metal redistribution among soil fractions. Results showed that sorption capacity for Zarqa River (ZR1) soil was higher than Wadi Dhuleil (WD1) soil for all metals. The order of sorption affinity for WD1 was in the decreasing order of Ni > Zn > Cd, consistent with electrostatic attraction and indication of weak association with soil constituents. Following metal addition, Zn and Ni were distributed among the carbonate and Fe/Mn oxide fractions, while Cd was distributed among the exchangeable and carbonate fractions in both soils. Amending soils with 3% HFO did not increase the concentration of metals associated with the Fe/Mn oxide fraction or impact metal redistribution. The study suggests that carbonates control the mobility and bioavailability of Zn, Ni, and Cd in these calcareous soils, even in presence of a strong adsorbent such as HFO. Thus, it can be inferred that in situ heavy metal remediation of these highly calcareous soils using iron oxide compounds could be ineffective

Vermiculite bio-barriers for Cu and Zn remediation: an eco-friendly approach for freshwater and sediments protection

The increase in heavy metal contamination in freshwater systems causes serious environmental problems in most industrialized countries, and the effort to find ecofriendly techniques for reducing water and sediment contamination is fundamental for environmental protection. Permeable barriers made of natural clays can be used as low-cost and eco-friendly materials for adsorbing heavy metals from water solution and thus reducing the sediment contamination. This study discusses the application of permeable barriers made of vermiculite clay for heavy metals remediation at the interface between water and sediments and investigates the possibility to increase their efficiency by loading the vermiculite surface with a microbial biofilm of Pseudomonas putida, which is well known to be a heavy metal accumulator. Some batch assays were performed to verify the uptake capacity of two systems and their adsorption kinetics, and the results indicated that the vermiculite bio-barrier system had a higher removal capacity than the vermiculite barrier (?34.4 and 22.8 % for Cu and Zn, respectively). Moreover, the presence of P. putida biofilm strongly contributed to fasten the kinetics of metals adsorption onto vermiculite sheets. In open-system conditions, the presence of a vermiculite barrier at the interface between water and sediment could reduce the sediment contamination up to 20 and 23 % for Cu and Zn, respectively, highlighting the efficiency of these eco-friendly materials for environmental applications. Nevertheless, the contribution of microbial biofilm in open-system setup should be optimized, and some important considerations about biofilm attachment in a continuous-flow system have been discussed.This work has been produced thanks to the collaboration of Dip.SA (University of Bologna) and IBB (University of Minho). A particular acknowledgment is due to Dr. E. Rosales. The work was partially financed by the FCT Strategic Project Pest-OE/EQB/LA0023 and the Project ‘‘BioEnv—Biotechnology and Bioengineering for a sustainable world,’’ co-funded by the Programa Operacional Regional do Norte (ON.2–O Novo Norte), QREN, FEDER

SARS-CoV-2 in the environment: Modes of transmission, early detection and potential role of pollutions

The coronavirus disease 2019 (COVID-19) is spreading globally having a profound effect on lives of millions of people, causing worldwide economic disruption. Curbing the spread of COVID-19 and future pandemics may be accomplished through understanding the environmental context of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and adoption of effective detection tools and mitigation policies. This article aims to examine the latest investigations on SARS-CoV-2 plausible environmental transmission modes, employment of wastewater surveillance for early detection of COVID-19, and elucidating the role of solid waste, water, and atmospheric quality on viral infectivity. Transmission of SARS-CoV-2 via faecal-oral or bio-aerosols lacks robust evidence and remains debatable. However, improper disinfection and defected plumbing systems in indoor environments such as hospitals and high-rise towers may facilitate the transport of virus-laden droplets of wastewater causing infection. Clinical and epidemiological studies are needed to present robust evidence that SARS-CoV-2 is transmissible via aerosols, though quantification of virus-laden aerosols at low concentrations presents a challenge. Wastewater surveillance of SARS-CoV-2 can be an effective tool in early detection of outbreak and determination of COVID-19 prevalence within a population, complementing clinical testing and providing decision makers guidance on restricting or relaxing movement. While poor air quality increases susceptibility to diseases, evidence for air pollution impact on COVID-19 infectivity is not available as infections are dynamically changing worldwide. Solid waste generated by households with infected individuals during the lockdown period may facilitate the spread of COVID-19 via fomite transmission route but has received little attention from the scientific community. Water bodies receiving raw sewage may pose risk of infection but this has not been investigated to date. Overall, our understanding of the environmental perspective of SARS-CoV-2 is imperative to detecting outbreak and predicting pandemic severity, allowing us to be equipped with the right tools to curb any future pandemic

Macroscopic and extended X-ray absorption fine structure spectroscopic investigation of ligand effect on zinc adsorption to kaolinite as a function of pH

Adsorption of zinc (Zn) to mineral surfaces is affected by various factors including naturally occurring ligands in soil environment. This study was conducted to elucidate the influence of citrate, humic acid (HA), siderophore desferrioxamine B (DFO-B) and phosphate (PO4) on Zn adsorption to kaolinite at varying pH using macroscopic adsorption isotherm and extended X-ray absorption fine structure spectroscopy. Zinc was adsorbed in kaolinite suspensions at Zn:ligand ratio of 1:1 and pH 4.5 to 7.5. Humic acid and PO4 enhanced Zn adsorption throughout the pH range, whereas citrate and DFO-B slightly increased Zn adsorption at approximately pH 5.7 or less but greatly suppressed it at greater than pH 5.7. Extended X-ray absorption fine structure analysis revealed that, at pH 5.5, Zn was adsorbed to kaolinite forming inner-sphere edge-sharing bidentate linkages in the absence (control) and presence of citrate, HA, and DFO-B. With pH increase to 7.5, the same adsorption geometry was evident in the presence of HA and DFO-B, whereas Zn was incorporated into a Zn-aluminum LDH surface precipitate in the control and formed outer-sphere complexes in the citrate presence. Phosphate precipitated Zn across the pH range studied. Overall, Zn adsorption mechanism of kaolinite varied with specific ligand and pH. Copyright © 2011 by Lippincott Williams & Wilkins

Elemental quantification, chemistry, and source apportionment in golf course facilities in a semi-arid urban landscape using a portable X-ray fluorescence spectrometer

This study extends the application of the portable X-ray fluorescence (PXRF) spectrometry to the examination of elements in semi-arid urban landscapes of the Southern High Plains (SHP) of the United States, focusing on golf courses. The complex environmental challenges of this region and the unique management practices at golf course facilities could lead to differences in concentration and in the chemistry of elements between managed (irrigated) and non-managed (non-irrigated) portions of these facilities. Soil samples were collected at depths of 0–10, 10–20, and 20–30 cm from managed and non-managed areas of seven different facilities in the city of Lubbock, Texas, and analyzed for a suite of soil properties. Total elemental quantification was conducted using a PXRF spectrometer. Findings mostly indicated no significant differences in the concentration of examined elements between the managed and non-managed areas of the facilities. However, strong positive relationships (<i>R</i> = 0.82&minus;0.91, <i>p</i> < 0.001) were observed among elements (e.g., Fe on the one hand and Cr, Mn, Ni, and As on the other; Cu and Zn; As and Cr) and between these elements and soil constituents or properties such as clay, calcium carbonate, organic matter, and pH. The strengths of these relationships were mostly higher in the non-managed areas, suggesting a possible alteration in the chemistry of these elements by anthropogenic influences in the managed areas. Principal component and correlation analyses within the managed areas suggested that As, Cr, Fe, Mn, and Ni could be of lithogenic origin, while Cu, Pb, and Zn could have anthropogenic influences. Only one possible, likely lithogenic, source of the elements was identified within the non-managed areas. As evidenced by the study, the PXRF spectrometer can be a valuable tool for elemental quantification and rapid investigation of elemental interaction and source apportionment in semi-arid climates

Availability of Cu and Zn in an acidic sludge-amended soil as affected by zeolite application and liming

Purpose Acidic soils exhibit high trace element availability compared to neutral pH soils, and thus, when trace metals are added (e. g. due to sewage sludge application), measures should be taken to reduce their mobility. In this experiment, we tested two such methods, liming and zeolite addition. The aim was to measure the availability, in ryegrass (Lolium perenne L.), of heavy metals (Cu and Zn) added to soil with sewage sludge in both acidic and limed soil. Materials and methods Thus, in this pot experiment, we used a soil at two pH values (original soil at pH 3.56 and limed to 6.5), two rates of sewage sludge (0 and 50 Mg ha(-1)) and three rates of zeolite (0, 2 and 5 Mg ha(-1), referred to as Z-0, Z-1 and Z-2, respectively). Results and discussion We found that metal concentrations in plant decreased significantly with liming but zeolite did not further reduce metal levels. In metal extractions with DTPA, zeolite additions reduced metal concentrations. In the second sampling time (on day 100), metal levels were significantly reduced at Z-0 and Z-1 compared to day 50, but at Z-2, metals were either only slightly reduced or even unchanged. Conclusions We concluded that zeolite hindered metals from being strongly and irreversibly bound onto soil colloids. Zeolite at Z-2 kept metal availability relatively high over time, while metal availability at Z-0 and Z-1 was being reduced due to liming