Lead remediation by geological fluorapatite combined with Penicillium Oxalicum and Red yeast.

Phosphate solubilizing fungi Penicillium oxalicum (POX) and Red yeast Rhodotorula mucilaginosa (Rho) have been applied in Pb remediation with the combination of fluorapatite (FAp), respectively. The secretion of oxalic acid by POX and the production of extracellular polymers (EPS) by Rho dominate the Pb remediation. In this study, the potential of Pb remediation by the fungal combined system (POX and Rho) with FAp was investigated. After six days of incubation, the combination of POX and Rho showed the highest Pb remove ratio (99.7%) and the lowest TCLP-Pb concentration (2.9 mg/L). The EPS combined with POX also enhanced Pb remediation, which has a 99.3% Pb removal ratio and 5.5 mg/L TCLP-Pb concentration. Meanwhile, Rho and EPS can also stimulate POX to secrete more oxalic acid, which reached 1510.1 and 1450.6 mg/L in six days, respectively. The secreted oxalic acid can promote FAp dissolution and the formation of lead oxalate and pyromorphite. Meanwhile, the EPS produced by Rho can combine with Pb to form EPS-Pb. In the combined system of POX + Rho and POX + EPS, all of the lead oxalate, pyromorphite, and EPS-Pb were observed. Our findings suggest that the combined application of POX and Rho with FAp is an effective approach for enhancing Pb remediation.

Lead remediation is promoted by phosphate-solubilizing fungi and apatite via the enhanced production of organic acid.

Lead (Pb) is one of the most common heavy metal pollutants in the environment, which can indirectly or directly threaten human health. Lead immobilization by apatite can reduce the effectiveness of Pb cations via the formation of pyromorphite (Pyro). However, the formation of Pyro is always depending on the release of phosphorus (P) from apatite. Phosphate-solubilizing fungi (PSF) can secrete large amounts of organic acid to promote the release of P from apatite. Although the combination of PSF and apatite has shown a huge potential in Pb remediation, this pathway needs to be more attention, especially for organic acid secretion by PSF. This research mainly reviews the possible pathway to strengthen Pb immobilization by PSF and apatite. Meanwhile, the limitation of this approach is also reviewed, with the aim of a better stabilizing effect of Pb in the environment and promoting the development of these remediation technologies.

Assessing the effect of four types of direct mail messages to promote the uptake of residential lead remediation funds.

Objective: To examine the efficacy of direct mailing using four types of messaging on promoting the uptake of residential lead remediation (RLR) funds in Lancaster, PA, USA. Study design: We designed a quasi-experiment to assess the effect of 4 RLR messages sent to households in Lancaster, PA by direct mail between September and December 2020: a brief flyer (F); a detailed brochure + the flyer (BF); a health infographic + the flyer (IF); and an application form + the flyer (AFF). Methods: Mailers were sent to addresses in four census tracts; each census tract received a different message. Both English and Spanish versions were sent. The outcomes were the event rate defined as the number of phone call inquiries received, and the number of applications received. The association between type of messaging and household type (owner-vs renter-occupied) was assessed using a chi square test. Results: The event rates for the renter-occupied households were lower than for owner-occupied households, regardless of treatment. The event rates for renter-occupied households in the F, BF, IF and AFF groups were 0.00%, 0.35%, 0.12% and 0.18% respectively compared to 0.93%, 0.45%, 0.86% and 1.32% for homeowners. More applications were received from homeowners, and the event rate of the owner-occupied households was significantly different from that of renter-occupied homes (p-value = 0.001). Conclusions: Event rates and applications received were higher for owner-occupied households than they were for renter-occupied households. Direct mailing of RLR information is feasible especially if households at high risk for lead poisoning are targeted.

Reducing lead exposure in school water: Evidence from remediation efforts in New York City public schools.

Following the Flint Water Crisis, many states passed legislation requiring schools to measure and remediate lead in school drinking water. In this study, we present new evidence on the level and distribution of lead in school drinking water by examining the case of New York City, which tested water from every public school fixture in the 2016-17 school year, remediated fixtures that showed elevated levels of lead above 15 ppb, and retested a sample of fixtures in 2018-19. Prior to remediation, 8 % of fixtures showed elevated levels of lead; after remediation, 5 % of fixtures did. In both pre- and post-remediation periods, Black children attended schools with a higher proportion of elevated fixtures than White, Asian, and Hispanic children. We observe post-remediation lead exposure reductions that were largest for Black children, though racial disparities in exposure remained. Together, our results show that New York City's remediation efforts significantly reduced lead in its schools' drinking water in a short period of time, providing evidence of the promise of such efforts. However, the continued presence of lead in school drinking water and persistent racial disparities in exposure demonstrate the ongoing challenges to eradicating lead exposure in schools.

Enhanced adsorption of aqueous Pb(II) by modified biochar produced through pyrolysis of watermelon seeds.

A biochar (BC) was obtained by the pyrolysis of watermelon seeds (WM) in nitrogen environment. In addition, a modified biochar (HP-BC) was obtained by means of H2O2 treatment of BC. Later on, both kinds of biochar (BC and HP-BC) were characterized and compared as regards their potential for Pb(II) adsorption from wastewater. Characterization was performed by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), Zeta potential analysis, elemental mapping, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Pb(II) adsorption characteristics for HP-BC and BC as were evaluated as a function of solution pH, contact time and Pb(II) equilibrium concentration, using kinetic and thermodynamic studies, as well as adsorption isotherms. Regarding kinetics, the pseudo-second order model showed good fitting to experimental data. Based on the Langmuir model, the maximum Pb(II) adsorption capacities were calculated as 44.32 mg g-1 and 60.87 mg g-1 for BC and HP-BC, respectively. Thermodynamic study indicated that Pb(II) adsorption onto BC and HP-BC was spontaneous and primarily governed by chemisorption and surface complexation. In view of the results, the H2O2 modification of the watermelon seeds biochar can be considered as a promising and cost effective approach as regards Pb(II) removal from water/wastewater, which would not cause adverse impacts on the surrounding environments. Overall, it can be seen as a procedure promoting the effective recycling of a waste/by-product, in line of the precepts of the circular economy, aiding to protect human and environmental health.

Immobilization of lead in anthropogenic contaminated soils using phosphates with/without oxalic acid.

Understanding the effects of oxalic acid (OA) on the immobilization of Pb(II) in contaminated soils by phosphate materials, has considerable benefits for risk assessment and remediation strategies for the soil. A series of phosphate amendments with/without oxalic acid were applied to two anthropogenic contaminated soils. We investigated the immobilization of Pb(II) by KH2PO4, phosphate rock (PR), activated phosphate rock (APR) and synthetic hydroxyapatite (HAP) at different phosphate:Pb (P:Pb) molar ratios (0, 0.6, 2.0 and 4.0) in the presence/absence of 50 mmol oxalic acid/kg soil, respectively. The effects of treatments were evaluated using single extraction with deionized water or CaCl2, Community Bureau of Reference (BCR) sequential extraction and toxicity characteristic leaching procedure (TCLP) methods. Our results showed that the concentration of water extractable, exchangeable and TCLP-Pb all decreased with incubation time. The concentration of water-extractable Pb after 120 days was reduced by 100% when soils were amended with APR, HAP and HAP+OA, and the TCLP-Pb was <5 mg/L for the red soil at P:Pb molar ratio 4.0. Water-soluble Pb could not be detected and the TCLP-Pb was <5 mg/L at all treatments applied to the yellow-brown soil. BCR results indicated that APR was most effective, although a slight enhancement of water-soluble phosphate was detected at the P:Pb molar ratio 4.0 at the beginning of incubation. Oxalic acid activated phosphates, and so mixing insoluble phosphates with oxalic acid may be a useful strategy to improve their effectiveness in reducing Pb bioavailability.