Seasonal toxicity variation in light-textured soil amended with urban sewage sludge: interaction effect on cadmium, nickel, and phytotoxicity

Exploring Plants with Flowers: From Therapeutic Nutritional Benefits to Innovative Sustainable Uses

Flowers have played a significant role in society, focusing on their aesthetic value rather than their food potential. This study's goal was to look into flowering plants for everything from health benefits to other possible applications. This review presents detailed information on 119 species of flowers with agri-food and health relevance. Data were collected on their family, species, common name, commonly used plant part, bioremediation applications, main chemical compounds, medicinal and gastronomic uses, and concentration of bioactive compounds such as carotenoids and phenolic compounds. In this respect, 87% of the floral species studied contain some toxic compounds, sometimes making them inedible, but specific molecules from these species have been used in medicine. Seventy-six percent can be consumed in low doses by infusion. In addition, 97% of the species studied are reported to have medicinal uses (32% immune system), and 63% could be used in the bioremediation of contaminated environments. Significantly, more than 50% of the species were only analysed for total concentrations of carotenoids and phenolic compounds, indicating a significant gap in identifying specific molecules of these bioactive compounds. These potential sources of bioactive compounds could transform the health and nutraceutical industries, offering innovative approaches to combat oxidative stress and promote optimal well-being.

Aging microplastics in wastewater pipeline networks and treatment processes: Physicochemical characteristics and Cd adsorption

Despite a wealth of information on removal of the microplastics (MPs) in wastewater treatment plants (WWTPs), little attention has been paid to how wastewater treatment process affect the MP physicochemical and adsorption characteristics. In this study, changes in physicochemical property of three MPs, i.e. polyamide (PA), polyethylene (PE) and polystyrene (PS) through the wastewater pipeline, grit and biological aeration tanks were investigated. The results show that compared with virgin MPs, the treated MPs have higher specific surface area and O content, and lower C and H contents, and glass transition temperature, implying that the three treatments cause the chain scission and oxidation of the MPs. Cd adsorption capacities of the MPs are higher than the corresponding virgin MPs after sulfidation in the pipeline (SWPN) and biological treatment in aeration tank (BTAT). Pearson correlation analysis shows that the increase is mainly resulted from the enhancement of the O-containing groups on the MPs. However, Cd adsorption capacities of the MPs decrease after mechanical abrasion in grit tank (MAGT), corresponding to the decrease in carbonyl index. Two dimensional FTIR correlation spectroscopy demonstrates that the NH bond in the PA plays a more important role than CH bond in the adsorption of Cd, but only change of the CH bond is found in the PE and PS. The findings provide new insights into the effect of WWTPs on the MP aging and physicochemical characteristics.

Variation of soil properties with sampling depth in two different light-textured soils after repeated applications of urban sewage sludge

Semi-arid agricultural soils have increasingly been subjected to urban sewage sludge (USS) applications due to accelerated soil depletion and shortages in manure supply. Research studies addressing USS reuse have mostly been conducted in cropping systems and focused on changes in topsoil properties of a given texture. Therefore, sludge-soil interactions could be largely influenced by the presence of plants, soil particle composition and depth. In this field study, two agricultural soils (sandy, S and sandy loam, SL) received simultaneously four annual USS applications of 40, 80, and 120 t ha^-1 year^-1 in absence of vegetation. Outcomes showed the increase of carbon and macronutrients in both soils proportionally to USS dose especially in the topsoil profile (0-20 cm). Subsoil (20-40 cm) was similarly influenced by sludge rates, showing comparable variations of fertility parameters though at significant lower levels. The depth-dependent improvement of soil fertility in both layers enhanced the microbiological properties accordingly, with significant variations in soil SL characterized by a higher clay content than soil S. Besides, positive correlations between increases in sludge dose, salinity, trace metals, and enzyme activities in both soils indicate that excessive sludge doses did not cause soil degradation or biotoxic effects under the described experimental conditions. In particular and despite high geoaccumulation indices of Ni in both soils and profiles, the global concentrations of Cu, Ni, Pb, and Zn were still below threshold levels for contaminated soils. In addition, the maintenance of pH values within neutral range and the increase of organic matter content with respect to control would have further reduced metal availability in amended soils. Therefore, we could closely investigate the effects of texture and depth on the intrinsic resilience of each soil to cope with repetitive USS applications.

Biochar Derived from Domestic Sewage Sludge: Influence of Temperature Pyrolysis on Biochars’ Chemical Properties and Phytotoxicity

The pyrolytic conversion of domestic sewage sludge (SS) into biochar is a promising method to reduce its large volume and recycle its high-value fuel gas as renewable energy and the use of its chemicals as soil fertilizers. Even though the effects of pyrolysis temperature on energy recovery have been extensively studied, little information has been found on nutrient recovery and biochar’s phytotoxicity before its reuse as a soil amendment. This study aims to investigate the ideal pyrolysis temperature that guarantees higher fertility levels as well as meeting quality standards for land disposal. Accordingly, air-dried domestic sewage sludge has been pyrolyzed at 260°C (PSS1), at 420°C (PSS2), and at 610°C (PSS3) with a residence time of 20, 40, and 60 minutes, respectively. The raw sewage sludge and the produced biochars have been analyzed to determine their volatile organic matter (VOM), mineral content (MC), nutrients’ level (total nitrogen TN, available phosphorus P, and potassium K), alkalinity (pH), and salinity (electrical conductivity EC and Na). The toxic effect of biochars derived from SS has been evaluated through the analysis of trace metals (Pb, Cr, Cd, Cu, and Zn) and their toxicity by measuring root elongation inhibition (REI). As expected, pyrolysis temperature has a significant impact on the biochars’ characteristics. This has been justified by higher VOM, TN, and P in the sewage sludge (SS) and the biochar (PSS1) produced at low temperature (260°C). However, higher pH, EC, Na, and K have been found in the biochars (PSS2 and PSS3) produced at higher temperature (420 and 610°C). The effect of pyrolysis temperature on trace metals concentrations has shown different patterns from one element to another, which indicates lower levels in the biochar (PSS2) produced at 420°C. As a result, the lowest REI has been observed in PSS2 compared to that in SS, PSS1, and PSS3, which highlights that 420°C is the ideal pyrolysis temperature for the safe reuse of SS as a soil amendment.

Cadmium Pollution Impact on the Bacterial Community Structure of Arable Soil and the Isolation of the Cadmium Resistant Bacteria

Microorganisms play an important role in the remediation of cadmium pollution in the soil and their diversity can be affected by cadmium. In this study, the bacterial community in arable soil samples collected from two near geographical sites, with different degrees of cadmium pollution at three different seasons, were characterized using Illumina MiSeq sequencing. The result showed that cadmium is an important factor to affect the bacterial diversity and the microbial communities in the high cadmium polluted area (the site H) had significant differences compared with low cadmium polluted area (the site L). Especially, higher concentrations of Cd significantly increased the abundance of Proteobacteria and Gemmatimonas whereas decreased the abundance of Nitrospirae. Moreover, 42 Cd-resistant bacteria were isolated from six soil samples and evaluated for potential application in Cd bioremediation. Based on their Cd-MIC [minimum inhibitory concentration (MIC) of Cd²⁺], Cd²⁺ removal rate and 16S rDNA gene sequence analyses, three Burkholderia sp. strains (ha-1, hj-2, and ho-3) showed very high tolerance to Cd (5, 5, and 6 mM) and exhibited high Cd²⁺ removal rate (81.78, 79.37, and 63.05%), six Bacillus sp. strains (151-5,151-6,151-13, 151-20, and 151-21) showed moderate tolerance to Cd (0.8, 0.4, 0.8, 0.4, 0.6, and 0.4 mM) but high Cd²⁺ removal rate (84.78, 90.14, 82.82, 82.39, 81.79, and 84.17%). Those results indicated that Burkholderia sp. belonging to the phylum Proteobacteria and Bacillus sp. belonging to the phylum Firmicutes have developed a resistance for cadmium and may play an important role in Cd-contaminated soils. Our study provided baseline data for bacterial communities in cadmium polluted soils and concluded that Cd-resistant bacteria have potential for bioremediation of Cd-contaminated soils.

Heavy Metals Behavior in Soil/Plant System after Sewage Sludge Application

One of the possibilities of removing heavy metals (HMs) from soil is the use of phytoremediation techniques supported with biosolids, which also allow for their disposal. Therefore, the objective of the research was the determination of the sewage sludge suitability after its application to urban soil in order to increase the phytoremediation efficiency of contaminated soil. A field experiment was established on lawns in Białystok (Poland) in two locations with different traffic. The research plots were fertilized with sludge in doses of 14.5 t DM/ha and 29 t DM/ha. A mixture of lawn grasses was sown on the prepared plots. During two years of experiment soil/plant samples were collected, and pH, organic matter, dehydrogenase and catalase activity (soil), the total content of Cd, Cr, Cu, Mo, Ni, Pb, Zn, and Hg (soil/plant), and their fractions (soil) were determined. The HMs in soil were present mainly in residual and reducible fractions. Zn had the highest share in acid-soluble fractions (17–45%). The efficiency of urban soil phytoremediation was determined by the calculation of bioconcentration (BCF) and translocation (TF) factors. The highest values for BCF and TF were obtained for Mo (1.97 and 1.99, respectively). In the presented study, sludge amendment caused an immobilization of heavy metals.

Potassium affects the phytoextraction potential of Tanzania guinea grass under cadmium stress

The supply of potassium (K) is a strategy to increase the tolerance of plants exposed to Cd toxicity. The aim of this study was to verify the influence of K on the growth and potential of Tanzania guinea grass (Panicum maximum Jacq. cv. Tanzania (syn. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs)) for Cd phytoextraction as well as to evaluate nutritional attributes of this grass under conditions of Cd stress. The experiment was conducted in a randomized complete block design, using a 3 × 4 factorial arrangement, with three replications. Three rates of K (0.4, 6.0, and 11.6 mmol L^-1) were combined with four rates of Cd (0.0, 0.5, 1.0, and 1.5 mmol L^-1) in nutrient solution. Two plant growth periods were evaluated. The increase in K supply to plants exposed to Cd rates of up to 1.0 mmol L^-1 caused increase in morphogenic and production attributes, as well as reduction in tiller mortality rate, in the second growth period. K concentrations (in both harvests) increased, while calcium and magnesium concentrations in the second harvest decreased with increasing Cd rates. The high availability of Cd (1.5 mmol L^-1) in the nutrient solution caused decrease in relative chlorophyll index (RCI) in both harvests. The high supply of K to plants exposed to Cd resulted in high shoot dry mass production, reducing Cd concentration in the photosynthetic tissues (which means great tolerance of the plant) and increasing the accumulation of this metal in the shoots that can be harvested. Therefore, K increases the Cd phytoextraction capacity of Tanzania guinea grass.

Biochemical and transcriptomic response of earthworms Eisenia andrei exposed to soils irrigated with treated wastewater

In order to ensure better use of treated wastewater (TWW), we investigated the effect of three increasing doses of TWW, 10%, 50%, and 100%, on biochemical and transcriptomic statuses of earthworms Eisenia andrei exposed during 7 and 14 days. The effect of TWW on the oxidative status of E. andrei was observed, but this effect was widely dependent on the dilution degree of TWW. Results showed a significant decrease in the catalase (CAT) activity and an increase in the glutathione-S-transferase (GST) activity, and considerable acetylcholinesterase (AChE) inhibition was recorded after 14 days of exposure. Moreover, malondialdehyde (MDA) accumulation was found to be higher in exposed animals compared to control worms. The gene expression level revealed a significant upregulation of target genes (CAT and GST) during experimentation. These data provided new information about the reuse of TWW and its potential toxicity on soil organisms.

The suitability of growing mulberry (Morus alba L.) on soils consisting of urban sludge composted with garden waste: a new method for urban sludge disposal

Efficient disposal of urban sewage sludge, material that typically contains high concentrations of heavy metals, has become a significant concern worldwide. The empirical purpose of the current study is to investigate physical and chemical parameters of composted sludge and garden waste at different ratios. Results reveal that nutrient content has significantly increased after the application of composts as compared to the controlled sample. Composting garden waste with sewage sludge at a 1:1 ratio promoted plant growth and gradually showed superiority in the later period. The maximum plant height, total biomass, and crown width of mulberry trees increased by 12.1, 33.5, and 45.7%, respectively, compared with the control treatment. The bound to organic matter of Hg, Cr, and Pb in the sewage sludge increased after composting with garden waste, and the mulberry exhibited a high ability to accumulate Ni and Cd from the soil. Conclusively, compared to using the two soil mediums separately, composting garden waste and sewage sludge together is beneficial for soil improvement and vegetation growth.