Peeling the onion: additional layers of regulation in the acid stress response.

Bacteria are capable of withstanding large changes in osmolality and cytoplasmic pH, unlike eukaryotes that tightly regulate their pH and cellular composition. Previous studies on the bacterial acid stress response described a rapid, brief acidification, followed by immediate recovery. More recent experiments with better pH probes have imaged single living cells, and we now appreciate that following acid stress, bacteria maintain an acidic cytoplasm for as long as the stress remains. This acidification enables pathogens to sense a host environment and turn on their virulence programs, for example, enabling survival and replication within acidic vacuoles. Single-cell analysis identified an intracellular pH threshold of ~6.5. Acid stress reduces the internal pH below this threshold, triggering the assembly of a type III secretion system in Salmonella and the secretion of virulence factors in the host. These pathways are significant because preventing intracellular acidification of Salmonella renders it avirulent, suggesting that acid stress pathways represent a potential therapeutic target. Although we refer to the acid stress response as singular, it is actually a complex response that involves numerous two-component signaling systems, several amino acid decarboxylation systems, as well as cellular buffering systems and electron transport chain components, among others. In a recent paper in the Journal of Bacteriology, M. G. Gorelik, H. Yakhnin, A. Pannuri, A. C. Walker, C. Pourciau, D. Czyz, T. Romeo, and P. Babitzke (J Bacteriol 206:e00354-23, 2024, https://doi.org/10.1128/jb.00354-23) describe a new connection linking the carbon storage regulator CsrA to the acid stress response, highlighting new additional layers of complexity.

A review of passive acid mine drainage treatment by PRB and LPB: From design, testing, to construction.

An extensive volume of acid mine drainage (AMD) generated throughout the mining process has been widely regarded as one of the most catastrophic environmental problems. Surface water and groundwater impacted by pollution exhibit extreme low pH values and elevated sulfate and metal/metalloid concentrations, posing a serious threat to the production efficiency of enterprises, domestic water safety, and the ecological health of the basin. Over the recent years, a plethora of techniques has been developed to address the issue of AMD, encompassing nanofiltration membranes, lime neutralization, and carrier-microencapsulation. Nonetheless, these approaches often come with substantial financial implications and exhibit restricted long-term sustainability. Among the array of choices, the permeable reactive barrier (PRB) system emerges as a noteworthy passive remediation method for AMD. Distinguished by its modest construction expenses and enduring stability, this approach proves particularly well-suited for addressing the environmental challenges posed by abandoned mines. This study undertook a comprehensive evaluation of the PRB systems utilized in the remediation of AMD. Furthermore, it introduced the concept of low permeability barrier, derived from the realm of site-contaminated groundwater management. The strategies pertaining to the selection of materials, the physicochemical aspects influencing long-term efficacy, the intricacies of design and construction, as well as the challenges and prospects inherent in barrier technology, are elaborated upon in this discourse.

Enhanced bioremediation of acid mine-influenced groundwater with micro-sized emulsified corn oil droplets (MOD) and sulfate-reducing bacteria (Desulfovibrio vulgaris) in a microcosm assay.

High concentrations of metals and sulfates in acid mine drainage (AMD) are the cause of the severe environmental hazard that mining operations pose to the surrounding ecosystem. Little study has been conducted on the cost-effective biological process for treating high AMD. The current research investigated the potential of the proposed carbon source and sulfate reduction bacteria (SRB) culture in achieving the bioremediation of sulfate and heavy metals. This work uses individual and combinatorial bioaugmentation and bio-stimulation methods to bioremediate acid-mine-influenced groundwater in batch microcosm experiments. Bioaugmentation and bio-stimulation methods included pure culture SRB (Desulfovibrio vulgaris) and microsized oil droplet (MOD) by emulsifying corn oil. The research tested natural attenuation (T 1), bioaugmentation (T2), biostimulation (T3), and bioaugmentation plus biostimulation (T4) for AM-contaminated groundwater remediation. Bioaugmentation and bio-stimulation showed the greatest sulfate reduction (75.3%) and metal removal (95-99%). Due to carbon supply scarcity, T1 and T2 demonstrated 15.7% and 27.8% sulfate reduction activities. Acetate concentrations in T3 and T4 increased bacterial activity by providing carbon sources. Metal bio-precipitation was substantially linked with sulfate reduction and cell growth. SEM-EDS study of precipitates in T3 and T4 microcosm spectra indicated peaks for S, Cd, Mn, Cu, Zn, and Fe, indicating metal-sulfide association for metal removal precipitates. The MOD provided a constant carbon source for indigenous bacteria, while Desulfovibrio vulgaris increased biogenic sulfide synthesis for heavy metal removal.

Improving liming mode for remediation of Cd-contaminated acidic paddy soils: Identifying the optimal soil pH, model and efficacies.

Liming has been widely taken to remediate Cd-contaminated acidic paddy soils, whereas liming mode involving in the relevant optimal soil pH, model and efficacies remain unclear. Both soil and field liming experiments were conducted to improve liming mode for precise remediation of Cd-contaminated acidic paddy soils. Soil batch liming experiments indicated soil DTPA-Cd and CaCl2-Cd were piecewise linearly correlated to soil pH with nodes of 6.8-8.0, and decreased respectively by 15.3%37.7% and 80.7%93.8% (P < 0.05) when soil pH raised over the nodes, indicating an appropriate target soil pH 7.0 for liming. Stepwise linear regression revealed that liming ratio (LR, kg ha-1) could be estimated from soil basal pH (pH0) and the interval to the target soil pH (ΔpH), as [LR=exp(1.10 ×ΔpH+0.61 ×pH0-4.98), R2 = 0.97, n = 42, P < 0.01]. The model exhibited high prediction accuracy (95.2%), low mean estimation error (-0.02) and root mean square error (0.20). Field liming experiment indicated liming to target pH decreased respectively soil CaCl2-Cd by 95.2-98.0% and rice grain Cd by 59.8-80.6% (P < 0.01), whereas uninfluenced rice grain yield. Correlation analysis and structural equation models (SEM) demonstrated that great reduction in Cd phytoavailability was mainly attributed to the transformation of soil water-soluble and exchangeable Cd to carbonate-bound Cd and Fe/Mn oxides-bound Cd and reduced Cd in iron plaque as increasing soil pH. However, rice grain Cd of 50% samples met national food safety standards limit of China (0.2 mg kg-1) due to the high soil Cd level (0.8 mg kg-1). In conclusion, liming to target soil pH 7.0 could be considered as a precise and effective remediation mode for Cd-contaminated acidic paddy soils and complementary practices should be implemented for severe pollution. Our results could provide novel insights on precise liming remediation of Cd-contaminated acidic paddy soils.

Systematic characterization of the chemical constituents in vitro and in vivo of Qianghuo by UPLC-Q-TOF-MS/MS.

The Chinese herb Qianghuo is an antiphlogistic herb with many effects and complex components. In this study, the chemical composition of Qianghuo and its components in rat plasma after oral administration were investigated using ultra-high-performance liquid chromatography coupled with quadrupole-time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). The extracts, blank plasma, and plasma containing the drug were analyzed by mass spectrometry, and data collected in both positive and negative ion modes were analyzed using Masslynx software, and the structures were confirmed by combining the compound fragment ions and mass spectrometry cleavage pathways. A total of 62 in vitro chemical components were identified, including 27 coumarins, 18 organic acids, 5 amino acids, 5 glycosides, 2 flavonoids, 4 nucleotides, and 1 ester, which were summarized from the obtained compounds in terms of their possible cleavage patterns. Among the identified 31 compounds in rat plasma, 21 were prototypes, mostly coumarins, organic acids, and flavonoids, and 10 were metabolites, which were mainly generated via hydroxylation and methylation pathways. Based on these, this study provides a theoretical foundation for quality control and basic research on Qianghuo medicinal substances.

Factors controlling accumulation and bioavailability of selenium in paddy soils: A case study in Luxi County, China.

Selenium (Se) accumulation in rice (Oryza sativa L.) has become a major global concern. Se offers multiple health benefits in humans; however, its inadequate or excessive intake can be harmful. Therefore, determining the factors driving Se abundance and bioavailability in paddy soils is essential to ensure the safety of human Se intake. This study investigated the accumulation, bioavailability, and distribution of Se in 820 paddy soil and rice grain samples from Luxi County, China to assess how soil properties (soil organic matter [SOM], cation exchange capacity [CEC], and pH), geographical factors (parent materials, elevation, and mean annual precipitation [MAP] and temperature [MAT]), and essential micronutrients (copper [Cu], zinc [Zn], and manganese [Mn]) govern Se accumulation and bioavailability in paddy soils. Results showed that the average soil Se content was 0.36 mg kg-1, which was higher than that in China (0.29 mg kg-1). Alternatively, the average rice grain Se content was 0.032 mg kg-1, which was lower than the minimum allowable content in Se-rich rice grains (0.04 mg kg-1). Five studied parent materials all had a significant effect on soil Se content but had little effect on Se bioavailability (p < 0.05). CEC, elevation, and SOM, as well as the soil contents of Cu, Zn, and Mn were positively correlated with soil Se content, but pH, MAP, and MAT were negatively correlated. Correspondingly, Se bioavailability was negatively correlated with SOM and soil Zn content, but positively correlated with MAP and grain contents of Cu, Zn, and Mn. Furthermore, partial least squares path analysis revealed the interactive impacts of the influencing factors on Se accumulation and bioavailability in soils. On this basis, prediction models were established to predict Se accumulation and bioavailability in paddy soils, thereby providing theoretical support for developing efficient control measures to meet Se challenges in agriculture.

Analysis of natural okra extracts as corrosion inhibitors for mild steel in acidic medium.

Plant extracts have been shown to effectively inhibit metal corrosion. Using the Box-Behnken design, gravimetric, and electrochemical techniques, analyses were designed to investigate the anti-corrosion potential of okra in a 1M HCl medium. The inhibition performances derived from the various methods were in good agreement, demonstrating that physio-chemisorption was effective and adhered to the Langmuir isotherm model. The efficiency of okra mucilage extract was 96% at a much lower concentration compared to 91.2% and 88.4% for the unsieved extract and gelly-okra filtrate, respectively. FTIR results showed the presence of several functional groups in the okra mucilage extract that are associated with adsorption, and TGA analysis revealed that the extract has high thermal stability. FESEM analysis also supported evidence of adsorption. It was determined that corrosion inhibition by okra mucilage extract was primarily influenced by temperature, followed by extract concentration, with immersion time having the least effect. From the model optimization, it was observed that okra mucilage extract at 200 ppm, 60°C, and 24 h gave an inhibition efficiency of 89.98% and high desirability. These results demonstrate the high capacity of natural okra as an efficient biodegradable corrosion inhibitor.

Unveiling the anticancer potentiality of single cell oils produced by marine oleaginous Paradendryphiella sp. under optimized economic growth conditions.

Bioprospecting about new marine oleaginous fungi that produce advantageous bioproducts in a green sustainable process is the key of blue bioeconomy. Herein, the marine Paradendryphiella sp. was utilized for single cell oils (SCOs) production economically, via central composite design, the lipid content enhanced 2.2-fold by 5.5 g/L lipid yeild on seawater-based media supplemented with molasses concentration 50 g/L, yeast extract, 2.25 g/L at initial pH value (5.3) and 8 days of static incubation. Subsequently, the fatty acid methyl esters profiles of SCOs produced on optimized media under different abiotic conditions were determined; signifying qualitative and quantitative variations. Interestingly, the psychrophilic-prolonged incubation increased the unsaturation level of fatty acids to 59.34%, while ω-6 and ω-3 contents representing 23.53% and 0.67% respectively. Remarkably, it exhibited the highest EC100 dose by 677.03 µg/mL on normal human lung fibroblast Wi-38 cells. Meanwhile, it showed the highest inhibiting proliferation potential on cancer cell lines of A549, MDA-MB 231 and HepG-2 cells by 372.37, 417.48 and 365.00 µg/mL, respectively. Besides, it elevated the oxidative stress, the expression of key apoptotic genes and suppressed the expression of key oncogenes (NF-κB, BCL2 and cyclin D); implying its promising efficacy in cancer treatment as adjuvant drug. This study denoted the lipogenesis capacity of Paradendryphiella sp. under acidic/alkaline and psychrophilic/mesophilic conditions. Hereby attaining efficient and economic process under seasonal variation with different Egyptian marine sources to fill the gap of freshwater crisis and simultaneously preserve energy.

Acid hydrolysis conditions do affect the non-extractable phenolic compounds composition from grape peel and seed.

This study aimed to evaluate the effect of hydrolysis conditions on non-extractable phenolic compounds (NEPC) composition of grape peel and seed powder. The effect of temperature (50-90 °C), hydrochloric acid concentration (0.1-15.0 %), and time (5-20 min) were evaluated to understand their impact on NEPC release/extraction and degradation. The use of 1.0 and 8.0 % of HCl concentrations (v/v) and temperatures of 65 and 80 °C produced extracts with higher concentrations and a larger set of compounds. These conditions promoted a balance between release/extraction and degradation processes, thereby maximizing the NEPC content in the extracts. Furthermore, the results suggest that hydrolysis conditions can be set to modulate the release of specific classes. Non-extractable proanthocyanidins showed higher concentrations when intermediate values of temperature and acid concentration were applied. Hydrolysable tannins and hydroxybenzoic acids, on the other hand, were better extracted using higher acid concentrations and higher temperatures. The results suggest that the concentration and composition of NEPC are influenced by the hydrolysis conditions and the type of matrix. Hence, it is crucial to account for this compositional variation when conducting research on the biological effects of NEPC and when using this fraction as supplements or food ingredients.

Root microbiota confers rice resistance to aluminium toxicity and phosphorus deficiency in acidic soils.

Aluminium (Al) toxicity impedes crop growth in acidic soils and is considered the second largest abiotic stress after drought for crops worldwide. Despite remarkable progress in understanding Al resistance in plants, it is still unknown whether and how the soil microbiota confers Al resistance to crops. Here we found that a synthetic community composed of highly Al-resistant bacterial strains isolated from the rice rhizosphere increased rice yield by 26.36% in acidic fields. The synthetic community harvested rhizodeposited carbon for successful proliferation and mitigated soil acidification and Al toxicity through extracellular protonation. The functional coordination between plants and microbes offers a promising way to increase the usage of legacy phosphorus in topsoil. These findings highlight the potential of microbial tools for advancing sustainable agriculture in acidic soils.

Chemometrics-based investigation of non-volatiles/volatiles flavor of tencha (Camellia sinensis cv. Yabukita, Longjing 43 and Baiye 1).

The increasing demand for tea consumption calls for the development of more products with distinct characteristics. The sensory quality of tencha is significantly determined by innate differences among tea cultivars. However, the correlations between the chemical composition and sensory traits of tencha are still unclear. To enhance the understanding of the flavor formation mechanism in tencha and further to develop new cultivars resources, we investigated non-volatiles and volatile metabolites as well as sensory traits in tencha from different tea cultivars (Camellia sinensis cv. Yabukita, Longjing 43 and Baiye 1); the relationships between the flavor traits and non-volatiles/volatiles were further evaluated by partial least squares - discriminate analysis (PLS-DA), multiple factor analysis (MFA) and multidimensional alignment (MDA) analysis. A total of 64 non-volatiles and 116 volatiles were detected in all samples, among which 71 metabolites were identified as key flavor-chemical contributors involving amino acids, flavonol glycosides, flavones, catechins, ketones, alcohols, hydrocarbons, aldehydes, esters and acids. The levels of taste-related amino acids, flavonol glycosides and gallic acid varied significantly among the tencha samples made from different tea cultivars. All the samples exhibited typical quality characteristics of tencha. The tencha from Camellia sinensis cv. Longjing 43 and Camellia sinensis cv. Baiye 1 (cultivated in the open) exhibited higher levels of amino acids and gallic acid, which were associated with the umami taste and mellow taste of tea infusion. Abundant flavonol glycosides were related to the astringency, while partial tri-glycosides specifically quercetin-3-O-galactoside-rhamnoside-glucoside and total of flavonol galactoside-rhamnoside-glucoside were associated with mellow taste. The floral alcohols were identified as significant contributors to the refreshing aroma traits of tencha. The green, almond-like, acidic and fruity odorants were associated with a green and fresh aroma, while the green, cheesy and waxy odorants such as ketones, esters, acids and hydrocarbons were associated with seaweed-like aroma. This study provides insight into sensory-related chemical profiles of tencha from different tea cultivars, supplying valuable information on flavor and quality identification for tencha.

Study on the removal of iron (II) and manganese (II) in acidic mine drainage by red mud: Performance and mechanism.

Red mud is an environmental burden during the alumina production process. To mitigate the hazards associated with red mud storage, this study investigated the utilization of alkaline red mud as a treatment agent for acidic mine drainage (AMD) with high concentrations of Fe(II) and Mn(II). This study explored the influence of reaction times, addition amounts of red mud, and pH values on the removal efficiency of Fe (II) and Mn(II) from high-concentration AMD. Various parameters such as suspended solids levels, effluent pH, and zeta potentials were measured to meet discharge standards. The adsorption mechanism of red mud was examined using SEM, XRD, EDX, XPS, and 3D-EEM analysis. Optimal conditions were determined as a reaction time of 2 h, pH value of 5.01 and the addition of 100 g/L red mud, achieving effective removal of Fe(II) (reduced from 1000 to 0.224 mg/L) and Mn (II) (reduced from 20 to 1.03 mg/L). The treated AMD meets discharge standards with reduced suspended matter content of 37.4 mg/L. These findings provided valuable insights for the utilization of red mud waste in engineering applications.

Microbiome and transcriptome analyses reveal the influence of calcined dolomite application on Eriocheir sinensis in a rice-crab co-culture system.

Co-culture systems of rice and aquatic animals can contribute to the ecological intensification of agriculture by reducing nutrient loss and the need for N fertilizer application and by enhancing nutrient-use efficiency. However, the input of high-protein diets into paddy fields, to facilitate the growth of aquatic animals, has been found to increase N pollution and acidification of the soil. Although soil amendments have been widely used to ameliorate acidic soils, reduce N2O emissions, and improve agronomic production, the relationship between soil amendments and aquatic animal remains unclear. Therefore, this study investigated the effects of calcined dolomite (hereafter referred to as dolomite) as an acidic soil amendment and Ca-Mg supplement in rice-crab co-culture using Eriocheir sinensis crabs (Chinese mitten crabs). High-throughput sequencing was used to examine crab bacterial community composition and crab hepatopancreas biology. Although the water pH was significantly increased in the dolomite group, the number, composition, and diversity of bacteria identified in crab gut microbiome did not vary significantly between the dolomite and control groups. In the dolomite group, the probiotic agents Candidatus Hepatoplasma and Lactobacillus were highly abundant in the crab gut, and immune- and retinol metabolism-related genes were significantly upregulated in the crab hepatopancreas. Overall, dolomite application increased crab health and water pH. Dolomite is a low-cost amendment, with better stability, compared to other soil amendments, thus making it ideal for sustainable and clean rice-aquatic animal co-culture.

Acidogenic fermentation of potato peel waste for volatile fatty acids production: Effect of initial organic load.

As a renewable carbon source produced from organic wastes by acidogenic fermentation, volatile fatty acids (VFAs) are important intermediates in chemical and biological fields and beneficial to resource recovery and carbon neutrality. Maximizing VFA production by some strategies without additional chemicals is critical to increasing economic and environmental benefits. In this study, the effects of initial organic load (OL) on the performance of VFA production, variations of intermediate metabolites, and the thermogravimetric properties of potato peel waste (PPW) during batch acidogenic fermentation were studied. The results showed that the concentration of VFAs increased with the increase of initial OL, while the VFA yield decreased with the increase of initial OL. When the initial OL was in the range of 28.4 g VS/L-91.3 g VS/L, the fermentation type of PPW was butyric acid fermentation. The highest butyric acid proportion of 61.3% was achieved with the initial OL of 71.5 g VS/L. With the increase of initial OL, the proportion of acetic acid and the utilization rate of protein in the PPW decreased. VFAs were produced from proteins and carbohydrates in the early stage and mainly produced from carbohydrates in the later stage. The production efficiency of VFA was relatively high with the initial OL of 71.5 g VS/L, because more easily-biodegradable compounds were solubilized. The results showed that suitably increased initial OL could accelerate acidogenesis, reduce hydrolysis time, and increase the proportion of butyric acid. The findings in this work suggest that PPW is a promising feedstock for butyric acid biosynthesis and appropriate initial OL is beneficial to VFA production.

Study of okra pectin prepared by sweeping frequency ultrasound/freeze-thaw pretreatment on corrosion inhibition of ANSI 304 stainless steel in acidic environment.

Green and efficient metal corrosion inhibitors are very essential, and natural okra pectin (OP) can fulfill this need with rational use of resources. OP was prepared by water-alcohol extraction method after freeze-thaw pretreatment (FTP)/sweeping frequency ultrasound pretreatment (SFUP), and used for corrosion inhibition of ANSI 304 stainless steel (304 SS) in 1 M hydrochloric acid (HCl). The molecular weight, hydrodynamic diameter and monosaccharide composition of OP were analyzed to determine the factors on the corrosion inhibition of 304 SS. During SFUP of okra, the time-domain variation of ultrasound field was monitored by piezoelectric film sensor, its frequency-domain variation was monitored by a hydrophone, and analyzed respectively by oscilloscope and spectrum analyzer. Static weight-loss method, electrochemical and microscopic analyses were used to evaluate the corrosion inhibition efficiency of OP at temperatures (25, 30, 40, 50 °C) and concentrations (0, 0.2, 0.5, 1, 2 g·L-1) to optimize corrosion inhibition performance. It was found that OP by FTP and SFUP had higher corrosion inhibition efficiency on metals in acidic environment. According to static weight-loss method, the corrosion inhibition efficiency of OP with concentration of 2 g·L-1 (25 °C) was improved to 90.27 % in the FTP group and 93.53 % in the SFUP group, which 5.14 % and 8.93 % higher than Control (without pretreatment). Meanwhile, the corrosion inhibition efficiency decreased gradually as the temperature increased. OP corrosion inhibition performance fit Langmuir adsorption isothermal model as a mixed adsorption based on physical adsorption. It was a mixed inhibitor to protect 304 SS from corrosion.

Effect of Mg-Modified Waste Straw Biochar on the Chemical and Biological Properties of Acidic Soils.

Biochar is important for soil improvement, fertilizer innovation, and greenhouse gas reduction. In this paper, Mg-modified biochar was prepared from rice and corn straw and mixed with soil at a 1% (w/w) addition in an indoor soil simulation experiment to study the effect of Mg-modified biochar on the chemical properties of acidic soil. The results showed that the addition of Mg-modified biochar reduced soil acidity and improved soil fertility. Compared with the control group, the Mg-modified biochar treatment significantly increased the concentrations of available potassium, available phosphorus, total phosphorus, organic carbon and exchangeable calcium and magnesium in the soil, and effectively increased the concentration of total nitrogen. Rice straw Mg-modified biochar treatment was more effective in increasing the soil-available potassium, available phosphorus, total phosphorus and exchangeable magnesium concentration, while corn straw Mg-modified biochar was more effective in increasing the soil organic carbon and exchangeable calcium concentration. In addition, the high pyrolysis temperature of Mg-modified biochar was more effective in promoting the soil-available potassium, available phosphorus and total nitrogen concentration, while the low pyrolysis temperature of Mg-modified biochar was more effective in promoting soil alkaline nitrogen, exchangeable calcium and magnesium.

Rare earth elements in tea garden soils and their bioavailability to tea buds in Taiwan.

Tea (Camellia sinensis) is a widespread beverage plant that prefers aluminum-enriched acidic soils. However, rare earth elements (REEs) might be highly phyto-available in these soils. With the increasing demands for REEs in high-technology industries, understanding the dynamics of REEs in the environment is essential. Thus, this study identified the total concentration of REEs in the root-zone soils and corresponding tea buds (n = 35) collected from tea gardens in Taiwan. Additionally, the labile REEs in the soils were extracted with 1 M KCl, 0.1 M HCl, and 0.05 M ethylenediaminetetraacetic acid (EDTA) to elucidate the fractionation tendency of REEs in the soil-plant system and the relationships between REEs and Al in the tea buds. The concentration of light REEs (LREEs) was higher than those of medium REEs (MREEs) and heavy REEs (HREEs) in all soil and tea bud samples. According to the upper continental crust (UCC) normalization, MREEs and HREEs were more abundant than LREEs in the tea buds. Furthermore, REEs remarkably increased with increasing Al in the tea buds, whereas the linear correlations between Al and MREEs and HREEs were stronger than between LREEs. Compared with LREEs, the extractabilities of MREEs and HREEs by all single extractants in the soils were higher, coinciding with their higher UCC-normalization-based enrichments in the tea buds. Moreover, the 0.1 M HCl- and 0.05 M EDTA-extractable REEs were affected by soil properties and significantly correlated with the total REEs in the tea buds. The concentration of REEs in the tea buds was successfully predicted by empirical equations of extractable REEs with 0.1 M HCl and 0.05 M EDTA, as well as general soil properties including pH, organic carbon, dithionite-citrate-bicarbonate-extractable iron, aluminum, and phosphorus. However, this prediction should be further verified using many soil and tea types in the future.

Nano-Zero-Valent Zinc-Modified Municipal Sludge Biochar for Phosphorus Removal.

Municipal sludge biochar (MSBC) can be used to absorb phosphorus in water for waste treatment. Nano-zero-valent zinc (nZVZ) was uniformly attached to MSBC to obtain a highly efficient phosphorus-absorbing composite material, nZVZ-MSBC. Characterization by FTIR, XPS, XRD, and BET showed that nZVZ was uniformly dispersed on the surface of the MSBC. Zinc loading was able to greatly improve the adsorption performance of MSBC for phosphorus. Adsorption experiments illustrated that the adsorption process conformed to the Langmuir model, and the maximum adsorption amount was 186.5 mg/g, which is much higher than that for other municipal sludge biochars. The adsorption process reached 80% of the maximum adsorption capacity at 90 min, and this gradually stabilized after 240 min; adsorption equilibrium was reached within 24 h. The optimum pH for adsorption was 5. The main adsorption mechanism was chemical adsorption, but physical adsorption, external diffusion, internal diffusion, and surface adsorption also played roles. The potential for application as an efficient adsorbent of phosphorus from water was confirmed. In addition, a novel strategy for municipal sludge disposal and resource utilization is provided.

Nutrient recovery and valorisation from pig slurry liquid fraction with membrane technologies.

Livestock slurry has been reported to be a potential secondary raw material as it contains macronutrients ­nitrogen, phosphorus and potassium-, which could be valorised as high-quality fertilizers if proper separation and concentration of valuable compounds is performed. In this work, pig slurry liquid fraction was assessed for nutrient recovery and valorisation as fertilizer. Some indicators were used to evaluate the performance of proposed train of technologies within the framework of circular economy. As ammonium and potassium species are highly soluble at the whole pH range, a study based on phosphate speciation at pH from 4 to 8 was assessed to improve the macronutrients recovery from the slurry, resulting in two different treatment trains at acidic and alkaline conditions. The acidic treatment system based on centrifugation, microfiltration and forward osmosis was applied to obtain a nutrient-rich liquid organic fertilizer containing 1.3 % N, 1.3 % P2O5 and 1.5 % K2O. The alkaline path of valorisation was composed by centrifugation and stripping by using membrane contactors to produce an organic solid fertilizer -7.7 % N, 8,0 % P2O5 and 2.3 % K2O-, ammonium sulphate solution -1.4 % N- and irrigation water. In terms of circularity indicators, 45.8 % of the initial water content and <50 % of contained nutrients were recovered - 28.3 % N, 43.5 % P2O5 and 46.6 % K2O - in the acidic treatment resulting in 68.68 g fertilizer per kg of treated slurry. 75.1 % of water was recovered as irrigation water and 80.6 % N, 99.9 % P2O5, 83.4 % K2O was valorised in the alkaline treatment, as 219.60 g fertilizer per kg of treated slurry. Treatment paths at acidic and alkaline conditions yield promising results for nutrients recovery and valorisation as the obtained products (nutrient rich organic fertilizer, solid soil amendment and ammonium sulphate solution) fulfil the European Regulation for fertilizers to be potentially used in crop fields.

Assessment of potential contamination and acid drainage generation in uranium mining zones of Peña Blanca, Chihuahua, Mexico.

Potential pollution of mining environmental liabilities' locations can be preliminarily and efficiently assessed by the potential generation of acid mine drainage and indices of contamination. This research evaluates the potential pollution by potentially toxic elements at locations with uranium mining liability evidence, using the net acid generation test and determining the background values to estimate acid mine drainage and indices of contamination. Sixty soil samples were collected, and the mineralogy and potentially toxic elements' total contents were determined by x-ray diffraction and optical spectrometry. The findings suggest that the soils related to a specific lithology might not present potential acid mine drainage generation but potential soil and sediment contamination. Future research is recommended on applying leaching tests to identify which potentially toxic elements are effectively being solubilized. Finally, it can be concluded that the study area's potential contamination is relatively low overall.