Accumulation and translocation of lead in vegetables through intensive use of organic manure and mineral fertilizers with wastewater.

In many countries with wastewater irrigation and intensive use of fertilizers (minerals and organics), heavy metal deposition by crops is regarded as a major environmental concern. A study was conducted to determine the impact of mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse on soil's trace Pb content and edible parts of vegetables. It also evaluated the risk of lead (Pb) contamination in water, soil, and food crops. Six vegetables (Daucus carota, Brassica oleracea, Pisum sativum, Solanum tuberosum, Raphanus sativus, and Spinacia oleracea) were grown in the field under twelve treatments with different nutrient and water inputs. The lead concentrations in soil, vegetables for all treatments and water samples ranged from 1.038-10.478, 0.09346-9.0639 mg/kg and 0.036-0.26448 mg/L, The concentration of lead in soil treated with wastewater in treatment (T6) and vegetable samples was significantly higher, exceeding the WHO's permitted limit. Mineral and organic fertilizers combined with wastewater treatment reduced lead (Pb) concentrations in vegetables compared to wastewater application without organic fertilizers. Health risk indexes for all treatments except wastewater treatment (T6) were less than one. Pb concentrations in mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse treated were determined to pose no possible risk to consumers.

Unveiling long-term combined effect of salinity and Lead(II) on anammox activity and microbial community dynamics in saline wastewater treatment.

The study assessed the effect of salinity and lead (Pb(II)) on the anammox sludge for nitrogen removal from saline wastewater. Results showed decreased nitrogen removal and specific anammox activity (SAA) with elevated salinity and Pb(II). SAA reduced from 541.3 ± 4.3 mg N g-1 VSS d-1 at 0.5 mg/L Pb(II) to 436.0 ± 0.2 mg N g-1 VSS d-1 at 30 g/L NaCl, further to 303.6 ± 7.1 mg N g-1 VSS d-1 under 30 g/L NaCl + 0.5 mg/L Pb(II). Notably, the combined inhibition at salinity (15-20 g/L NaCl) and Pb(II) (0.3-0.4 mg/L) exhibited synergistic effect, while higher salinity and Pb(II) aligned with independent inhibition models. Combined inhibition decreased protein/polysaccharides ratio, indicating more severe negative effect on anammox aggregation capacity. Metagenomics confirmed decreased Candidatus Kuenenia, and enhanced denitrification under elevated salinity and Pb(II) conditions. This study offers insights into anammox operation for treating saline wastewater with heavy metals.

Accumulation of Cd and Pb in sediments and Asian swamp eels (Monopterus albus) from downstream area of Cisadane River, Indonesia.

This study examined the presence of two heavy metals (Cd and Pb) in the sediments and Asian swamp eels (Monopterus albus) in the downstream area of Cisadane River. The average concentrations of Cd and Pb in the sediments from all sampling locations were 0.594 ± 0.230 mg/kg and 34.677 ± 24.406 mg/kg, respectively. These concentrations were above the natural background concentration and the recommended value of interim sediment quality guidelines (ISQG), suggesting an enrichment process and potential ecological risk of studied metals to the ecosystem of Cisadane River. The increase in contamination within this region may be attributed to point sources such as landfill areas, as well as the industrial and agricultural land activities in surrounding area, and experienced an increasing level leading towards the estuary of Cisadane River. Meanwhile, the average concentrations of Cd and Pb in the eels from all sampling locations were 0.775 ± 0.528 µg/g and 28.940 ± 12.921 µg/g, respectively. This study also discovered that gill tissues contained higher levels of Cd and Pb than the digestive organ and flesh of Asian swamp eels. These concentrations were higher than Indonesian and international standards, suggesting a potential human health risk and therefore the needs of limitations in the consumption of the eels. Based on the human health risk assessment, the eels from the downstream of Cisadane River are still considered safe to be consumed as long as they comply with the specified maximum consumption limits.

Bio-stimulating effect of endophytic Aspergillus flavus AUMC 16068 and its respective ex-polysaccharides in lead stress tolerance of Triticum aestivum plant.

Heavy metal accumulation is one of the major agronomic challenges that has seriously threatened food safety. As a result, metal-induced phytotoxicity concerns require quick and urgent action to retain and maintain the physiological activities of microorganisms, the nitrogen pool of soils, and the continuous yields of wheat in a constantly worsening environment. The current study was conducted to evaluate the plant growth-promoting endophytic Aspergillus flavus AUMC 16,068 and its EPS for improvement of plant growth, phytoremediation capacity, and physiological consequences on wheat plants (Triticum aestivum) under lead stress. After 60 days of planting, the heading stage of wheat plants, data on growth metrics, physiological properties, minerals content, and lead content in wheat root, shoot, and grains were recorded. Results evoked that lead pollution reduced wheat plants' physiological traits as well as growth at all lead stress concentrations; however, inoculation with lead tolerant endophytic A. flavus AUMC 16,068 and its respective EPS alleviated the detrimental impact of lead on the plants and promoted the growth and physiological characteristics of wheat in lead-contaminated conditions and also lowering oxidative stress through decreasing (CAT, POD, and MDA), in contrast to plants growing in the un-inoculated lead polluted dealings. In conclusion, endophytic A. flavus AUMC 16,068 spores and its EPS are regarded as eco-friendly, safe, and powerful inducers of wheat plants versus contamination with heavy metals, with a view of protecting plant, soil, and human health.

Foliar uptake screening: A promising strategy for identifying wheat varieties with low lead accumulation.

Lead (Pb) contamination in wheat grain is of great concern, especially in North China. Atmospheric deposition is a major contributor to Pb accumulation in wheat grain. Screening low Pb accumulating wheat varieties has been an effective method for addressing Pb contamination in wheat grain. However, identifying wheat varieties with low Pb accumulation based on foliar uptake of atmospheric Pb has been neglected. Therefore, two field trials with distinct atmospheric Pb deposition were conducted to screen for stable varieties with low Pb accumulation. It was verified that YB700 and CH58, which have high thousand-grain weights and stable low Pb accumulation in field 1 (0.19 and 0.13 mg kg-1) and field 2 (0.17 and 0.20 mg kg-1), respectively, were recommended for cultivation in atmospheric Pb contaminated farmlands in North China. Furthermore, indoor experiments were conducted to investigate Pb uptake by the roots and leaves of different wheat varieties. Our findings indicate that Pb accumulation in different wheat varieties is primarily influenced by foliar Pb uptake rather than root Pb uptake. Interestingly, there was a positive correlation (p < 0.05) between the Pb concentrations in leaves and the stomatal width and trichome length of the adaxial epidermal surface. Additionally, there is a positive correlation (p < 0.01) between the Pb concentration in the wheat grain and trichome length. In conclusion, the screening of wheat varieties with narrower stomatal widths or shorter trichomes based on foliar uptake pathways is an effective strategy for ensuring food safety in areas contaminated by atmospheric Pb.

Application of phosphogypsum and phosphate-solubilizing fungi to Pb remediation: From simulation to in vivo incubation.

Phosphogypsum (PG) is the produced solid waste during phosphorus (P) extraction from phosphate rocks. PG is featured by its abundant PO43- and SO42-. This study investigated the utilization of PG as a material for lead (Pb) remediation, with the assistance of functional fungus. Aspergillus niger (A. niger) is a typical phosphate-solubilizing fungi (PSF), which has high ability to secret organic acids. Oxalic acid is its major secreted organic acid, which is often applied to enhance the P release from phosphate minerals. In this study, synthetic oxalic acid increased the immobilization rate of Pb2+ up to >99 % with the addition of PG. Then, it was observed that biogenic oxalic acid from A. niger can achieve comparable remediation effects. This was due to that PG could provide sufficient P for fungal growth, which allowed sustainable remediation. Subsequently, oxalic acid secreted by A. niger significantly increased the release of active P from PG, and then induced the formation of PPb minerals. In addition, other metabolites of A. niger (such as tyrosine-like substance) can also be complexed with Pb2+. Simultaneously, A. niger did not induce evidently elevation water-soluble fluorine (F) as PG contained abundant Ca2+. Moreover, this study elucidated that oversupply of PG promoted the formation of anglesite (Ksp = 1.6 × 10-8, relatively unstable), whereas the formation of lead oxalate (Ksp = 4.8 × 10-10, relatively stable) was reduced. This study hence shed a bright light on the sustainable utilization of PG for fungus-assisted remediation of heavy metals.

The role of reduced graphene oxide on mitigation of lead phytotoxicity in Triticum aestivum L.plants at morphological and physiological levels.

Rapid global industrialization and an increase in population have enhanced the risk of heavy metals accumulation in plant bodies to disrupt the morphological, biochemical, and physiological processes of plants. To cope with this situation, reduced graphene oxide (rGO) NPs were used first time to mitigate abiotic stresses caused in plant. In this study, rGO NPs were synthesized and reduced with Tecoma stans plant leave extract through modified Hummer's methods. The well prepared rGO NPs were characterized by ultra-violet visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential, and scanning electron microscopy (SEM). However, pot experiment was conducted with four different concentrations (15, 30, 60, 120 mg/L) of rGO NPs and three different concentrations (300, 500,700 mg/L) of lead (Pb) stress were applied. To observe the mitigative effects of rGO NPs, 30 mg/L of rGO NPs and 700 mg/L of Pb were used in combination. Changes in morphological and biochemical characteristics of wheat plants were observed for both Pb stress and rGO NPs treatments. Pb was found to inhibit the morphological and biochemical characteristics of plants. rGO NPs alone as well as in combination with Pb was found to increase the chlorophyll content of wheat plants. Under Pb stress conditions and rGO NPs treatments, antioxidant enzyme activities like ascorbate peroxidases (APX), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were observed. Current findings revealed that greenly reduced graphene oxide NPs can effectively promote growth in wheat plants under Pb stress by elevating chlorophyll content of leaves, reducing the Pb uptake, and suppressing ROS produced due to Pb toxicity.

Integrated transcriptomics and metabolomics revealed the mechanism of catechin biosynthesis in response to lead stress in tung tree (Vernicia fordii).

Lead (Pb) affects gene transcription, metabolite biosynthesis and growth in plants. The tung tree (Vernicia fordii) is highly adaptive to adversity, whereas the mechanisms underlying its response to Pb remain uncertain. In this work, transcriptomic and metabolomic analyses were employed to study tung trees under Pb stress. The results showed that the biomass of tung seedlings decreased with increasing Pb doses, and excessive Pb doses resulted in leaf wilting, root rot, and disruption of Pb homeostasis. Under non-excessive Pb stress, a significant change in the expression patterns of flavonoid biosynthesis genes was observed in the roots of tung seedlings, leading to changes in the accumulation of flavonoids in the roots, especially the upregulation of catechins, which can chelate Pb and reduce its toxicity in plants. In addition, Pb-stressed roots showed a large accumulation of VfWRKY55, VfWRKY75, and VfLRR1 transcripts, which were shown to be involved in the flavonoid biosynthesis pathway by gene module analysis. Overexpression of VfWRKY55, VfWRKY75, and VfLRR1 significantly increased catechin concentrations in tung roots, respectively. These data indicate that Pb stress-induced changes in the expression patterns of those genes regulate the accumulation of catechins. Our findings will help to clarify the molecular mechanism of Pb response in plants.

The 8-17 DNAzyme can operate in a single active structure regardless of metal ion cofactor.

DNAzymes - synthetic enzymes made of DNA - have long attracted attention as RNA-targeting therapeutic agents. Yet, as of now, no DNAzyme-based drug has been approved, partially due to our lacking understanding of their molecular mode of action. In this work we report the solution structure of 8-17 DNAzyme bound to a Zn2+ ion solved through NMR spectroscopy. Surprisingly, it turned out to be very similar to the previously solved Pb2+-bound form (catalytic domain RMSD = 1.28 Å), despite a long-standing literature consensus that Pb2+ recruits a different DNAzyme fold than other metal ion cofactors. Our follow-up NMR investigations in the presence of other ions - Mg2+, Na+, and Pb2+ - suggest that at DNAzyme concentrations used in NMR all these ions induce a similar tertiary fold. Based on these findings, we propose a model for 8-17 DNAzyme interactions with metal ions postulating the existence of only a single catalytically-active structure, yet populated to a different extent depending on the metal ion cofactor. Our results provide structural information on the 8-17 DNAzyme in presence of non-Pb2+ cofactors, including the biologically relevant Mg2+ ion.

Industrial hemp (Cannabis sativa L.) can utilize and remediate soil strongly contaminated with Cu, As, Cd, and Pb by phytoattenuation.

Industrial hemp (Cannabis sativa L.) has great application potential in heavy metal-polluted soils owing to its safe non-food utilization. However, the fate of heavy metals in different varieties of hemp planted in strongly contaminated natural soils remains unknown. Here, we investigated the growth, heavy metal uptake, distribution, and transfer of nine hemp varieties in soils strongly contaminated with Cu, As, Cd, and Pb. Hemp variety and metal type were the main factors affecting the growth and heavy metal uptake in hemp. The nine hemp varieties grew well in the contaminated soils; however, differences existed among the varieties. The biomass of Z3 reached 5669.1 kg hm-1, whereas that of Yunma No. 1 was only 51.8 % of Z3. The plant height, stalk diameter, and stalk bark thickness of Z3 were greater than those of the other varieties, reaching 168 cm, 9.2 mm, and 0.56 mm, respectively. Permanova's analysis revealed that the total effects of Cu, As, Cd, and Pb on the growth of the nine hemp varieties reached 60 %, with leaf As having the greatest effect, reaching 16 %. , Even in strongly contaminated soils, the nine varieties showed poor Cu, As, Cd, and Pb uptake. Most of the Cu, As, Cd, and Pb were retained in the root, reaching 57.7-72.4, 47.6-64.7, 76.0-92.9, and 70.0-87.8 %, respectively. Overall, the Cu, As, Cd, and Pb uptake of Wanma No.1 was the highest among the nine varieties, whereas that of Guangxi Bama was the lowest. These results indicate that hemp is a viable alternative for phytoattenuation in soils contaminated with heavy metals because of its ability to tolerate and accumulate Cu, As, Cd, and Pb in its roots, and Guangxi Bama is superior to the other varieties considering the safe utilization of hemp products.

Bioremediation of Pb contaminated water using a novel Bacillus sp. strain MHSD_36 isolated from Solanum nigrum.

The Pb bioremediation mechanism of a multi-metal resistant endophytic bacteria Bacillus sp. strain MHSD_36, isolated from Solanum nigrum, was characterised. The strain tested positive for the presence of plant growth promoters such as indoleacetic acid, 1-aminocyclopropane-1-carboxylate deaminase, siderophores, and phosphate solubilization. The experimental data illustrated that exopolysaccharides and cell hydrophobicity played a role in Pb uptake. The data further showed that the cell wall biosorbed a significant amount (71%) of the total Pb (equivalent to 4 mg/L) removed from contaminated water, compared to the cell membrane (11%). As much as 11% of the Pb was recovered from the cytoplasmic fraction, demonstrating the ability of the strain to control the influx of toxic heavy metals into the cell and minimize their negative impacts. Pb biosorption was significantly influenced by the pH and the initial concentration of the toxic ions. Furthermore, the presence of siderophores and biosurfactants, when the strain was growing under Pb stress, was detected through liquid chromatography mass spectrometry. The strain demonstrated a multi-component based Pb biosorption mechanism and thus, has a great potential for application in heavy metal bioremediation.

Lead and copper removal from sterile dumps by phytoremediation with Robinia pseudoacacia.

In Romania, huge quantities of gangue material from the mining activity practiced in the past were improperly stored and led to the pollution of the environment. Thus, this work is framed to manage the sterile dump of the "Radeș" mine (Alba, Romania) through a 12-week phytoremediation process. The efficient use of Robinia pseudoacacia was studied through the implementation, at the laboratory level, of a phytoremediation experiment based on various variants prepared by mixtures of gangue material, uncontaminated soil, and dehydrated sludge. The prepared variants, all planted with R. pseudoacacia, were watered with tap water, potassium monobasic phosphate, and enzyme solution. The bioconcentration and translocation factors for lead showed values ˂ 1, which indicates a potential presence of an exclusion system for Pb or a reduced Pb bioavailability since the R. pseudoacacia accumulates high concentrations of metals absorbed on and inside the roots. For copper, both factors had values > 1 indicating the suitability of R. pseudoacacia to readily translocate copper into the epigean organs. In the investigated experimental conditions, the highest efficiency in the removal of copper (93.0%) and lead (66.4%) by plants was obtained when gangue material was not mixed with other materials and wetted with enzymatic solution.

Maintaining the cultivation of vegetables with low Pb accumulation while remediating the soil of an allotment garden (Nantes, France) by phytoextraction.

Lead (Pb) is commonly found in urban soils and can transfer to vegetables. This entails a health risk for consumers of garden crops. The increasing demand of gardening on urban soil linked to the population increase and concentration in urban areas induces an increase in the risk, as people could be forced to cultivate contaminated soils. The aim of this study was to evaluate the performance of a cropping system that allows simultaneously (i) growing eatable vegetables that accumulate few Pb and (ii) cleaning up the soil with other plants by phytoextraction. The tests were carried out in an allotment garden (Nantes, France) where soils are moderately enriched by Pb from geogenic origin (178 mg.kg-1 of dry soil on average). Four vegetables known to accumulate slightly Pb (Solanum lycopersicum, Brassica oleracea cv. "Capitata," Solanum tuberosum, and Phaseolus vulgaris) were grown. The in situ ability of Brassica juncea L. to progressively absorb the phytoavailable Pb of the soil was assessed during four seasons. Analyses of the edible parts of the four vegetables confirmed that they can all be safely cultivated. The accumulation of Pb in B. juncea shoots was too low (ca. 1 mg.kg-1 of dry matter at best) for phytoextraction purposes. Our results confirm that it is possible to grow very low Pb-accumulating vegetables on soils moderately contaminated with Pb, although it was not possible to reduce phytoavailable Pb rapidly enough with B. juncea. This study identifies possible avenues of research to improve this cropping system by using appropriate vegetables that will allow food production to continue on moderately contaminated soil while cleaning it up.

Insights into growth stages and genotypes in airborne Pb accumulation in Oryza sativa L. grains: Utilizing isotope fingerprinting alongside a model study.

Atmospheric exposure is an important pathway of accumulation of lead (Pb) in Oryza sativa L. grains. In this study, source contributions of soil, early atmospheric exposure, and late atmospheric exposure, along with their bioaccumulation ratios were examined both in the pot and field experiments using stable Pb isotope fingerprinting technology combined with a three-compartment accumulation model. Furthermore, genotype differences in airborne Pb accumulation among four field-grown rice cultivars were investigated using the partial least squares path model (PLS-PM) linking rice Pb accumulation to agronomic traits. The findings revealed that during the late growth period, the air-foliar-grain transfer of Pb was crucial for rice Pb accumulation. Approximately 69-82% of the Pb found in polished rice was contributed by atmospheric source, with more than 80% accumulating during the late growth stage. The air accumulation ratios of rice grains were genotype-specific and estimated to be 0.364-1.062 m3/g during the late growth. Notably, grain size exhibited the highest standardized total effects on the airborne Pb concentrations in the polished rice, followed by leaf Pb and the upward translocation efficiency of Pb. The present study indicates that mitigating the health risks associated with Pb in rice can be achieved by controlling atmospheric Pb levels during the late growth stage and choosing Japonica inbred varieties characterized by large grain size.

Co-exposure to lead and high-fat diet aggravates systemic inflammation in mice by altering gut microbiota and the LPS/TLR4 pathway.

This study reports the toxicity of Pb exposure on systemic inflammation in high-fat-diet (HFD) mice and the potential mechanisms. Results indicated that Pb exacerbated intestinal barrier damage and increased serum levels of lipopolysaccharide (LPS) and diamine oxidase in HFD mice. Elevated LPS activates the colonic and ileal LPS-TLR4 inflammatory signaling pathway and further induces hepatic and adipose inflammatory expression. The 16S rRNA gene sequencing results showed that Pb promoted the abundance of potentially harmful and LPS-producing bacteria such as Coriobacteriaceae_UCG-002, Alloprevotella, and Oscillibacter in the intestines of HFD mice, and their abundance was positively correlated with LPS levels. Additionally, Pb inhibited the abundance of the beneficial bacteria Akkermansia, resulting in lower levels of the metabolite short-chain fatty acids (SCFAs). Meanwhile, Pb inhibited adenosine 5'-monophosphate-activated protein kinase signaling-mediated lipid metabolism pathways, promoting hepatic lipid accumulation. The above results suggest that Pb exacerbates systemic inflammation and lipid disorders in HFD mice by altering the gut microbiota, intestinal barrier, and the mediation of metabolites LPS and SCFAs. Our study provides potential novel mechanisms of human health related to Pb-induced metabolic damage and offers new evidence for a comprehensive assessment of Pb risk.

Triggering antibacterial activity of a common plant by biosorption of selected heavy metals.

The presented study proposes an efficient utilization of a common Thymus serpyllum L. (wild thyme) plant as a highly potent biosorbent of Cu(II) and Pb(II) ions and the efficient interaction of the copper-laden plant with two opportunistic bacteria. Apart from biochars that are commonly used for adsorption, here we report the direct use of native plant, which is potentially interesting also for soil remediation. The highest adsorption capacity for Cu(II) and Pb(II) ions (qe = 12.66 and 53.13 mg g-1, respectively) was achieved after 10 and 30 min of adsorption, respectively. Moreover, the Cu-laden plant was shown to be an efficient antibacterial agent against the bacteria Escherichia coli and Staphylococcus aureus, the results being slightly better in the former case. Such an activity is enabled only via the interaction of the adsorbed ions effectively distributed within the biological matrix of the plant with bacterial cells. Thus, the sustainable resource can be used both for the treatment of wastewater and, after an effective embedment of metal ions, for the fight against microbes.

Responses to lead stress in Scrophularia striata: insights into antioxidative defence mechanisms and changes in flavonoids profile.

Lead (Pb) induces oxidative stress in plants, which results in different responses, including the production of antioxidants and changes in the profile of secondary metabolites. In this study, the responses of Scrophularia striata exposed to 250mgL-1 Pb (NO3 )2 in a hydroponic environment were determined. Growth parameters, oxidative and antioxidative responses, redox status, and the concentration of Pb were analysed in roots and shoots. Malondialdehyde and hydrogen peroxide (H2 O2 ) levels in the roots were significantly increased and reached their highest value at 72h after Pb treatment. Superoxide dismutase, catalase, and peroxidase, as an enzymatic antioxidant system, were responsible for reactive oxygen species scavenging, where their activities were increased in the shoot and root of Pb-treated plants. Enzymatic antioxidant activities were probably not enough to remove a significant H2 O2 content in response to Pb treatment. Therefore, other defence responses were activated. The results stated that the flavonoid components of S. striata progressed towards the increase of isoflavone, flavanol, and stilbenoid contents under Pb treatment. In general, S. striata stimulates the enzymatic defence system and activates the non-enzymatic system by modulating the profile of flavonoids toward the production of flavonoids with high antioxidant activity, such as quercetin and myricetin in response to Pb stress.

Current situation of lead (Pb) exposure in raptors and waterfowl in Japan and difference in sensitivity to in vitro lead exposure among avian species.

Although lead (Pb) poisoning in wild birds has been considered a serious problem in Japan for over 30 years, there is little information about Pb exposure and its sources throughout Japan except for Hokkaido. Furthermore, to identify and effectively prioritize the conservation needs of highly vulnerable species, differences in sensitivity to Pb exposure among avian species need to be determined. Therefore, we investigated the current situation of Pb exposure in raptors (13 species, N = 82), waterfowl (eight species, N = 44) and crows (one species, N = 6) using concentration and isotope analysis. We employed blood or tissue samples collected in various Japanese facilities mainly in 2022 or 2023. We also carried out a comparative study of blood δ-ALAD sensitivity to in vitro Pb exposure using blood of nine avian species. Pb concentrations in the blood or tissues displayed increased levels (>0.1 µg/g blood) in two raptors (2.4%), ten waterfowl (23%) and one crow (17%). Among them, poisoning levels (>0.6 µg/g blood) were found in one black kite and one common teal. The sources of Pb isotope ratios in ten blood samples with high Pb levels were determined as deriving from shot pellets (N = 9) or rifle bullets (N = 1). In the δ-ALAD study, red-crowned crane showed the highest sensitivity among the nine tested avian species and was followed in order by five Accipitriformes species (including white-tailed and Steller's sea eagle), Blakiston's fish owl, Muscovy duck and chicken, suggesting a genetically driven variance in susceptibility. Further studies on contamination conditions and exposure sources are urgently needed to inform strict regulations on the usage of Pb ammunition. Furthermore, detailed examinations of δ-ALAD sensitivity, interspecific differences, and other factors involved in the variability in sensitivity to Pb are required to identify and prioritize highly sensitive species.

Responses of plankton community to threshold metal concentrations of cadmium and lead in a mesocosm experiment at Bay of Bengal.

Metals are essential at trace levels to aquatic organisms for the function of many physiological and biological processes. But their elevated levels are toxic to the ecosystem and even brings about shifts in the plankton population. Threshold limits such as Predicted No Effect Concentration (PNEC - 0.6 µg/l of Cd; 2.7 µg/l of Pb), Criterion Continuous Concentration (CCC - 3.0 µg/l of Cd; 4.5 µg/l of Pb) and Criterion Maximum Concentration (CMC - 23 µg/l of Cd; 130 µg/l of Pb) prescribed for Indian coastal waters were used for the study. Short-term mesocosm experiments (96 h) were conducted in coastal waters of Visakhapatnam to evaluate responses of the planktonic community on exposure to threshold concentrations of cadmium and lead for the first time. Four individual experimental bags of 2500 L capacity (Control, PNEC, CCC & CMC) were used for the deployment and ambient water samples were analysed simultaneously to evaluate the impacts of the threshold levels in the natural waters. Chaetoceros sp. were dominant group in the control system whereas, Prorocentrum sp. Ceratium sp. Tintinopsis sp. Chaetoceros sp. and Skeletonema sp. were major groups in the test bags. Throughout the experiment the phytoplankton community did not show any significant differences with increased nutrients and plankton biomass (Chl-a <8.64 mg/m3). Positive response of plankton community was observed in the experimental bags. High abundance of diatoms were observed in PNEC, CCC & CMC bags at 48 h and the abundance decreased with shift in the species at 72-96 h. The catalase activity in phytoplankton (5.99 nmol/min/ml) and the zooplankton (4.77 nmol/min/ml) showed induction after exposure to PNEC. The present mesocosm study is confirmed that short-term exposure to threshold metal concentration did not affects the phytoplankton community structure in PNEC, but CCC and CMC affects the community structure beyond 24 h. The insights from this study will serve as a baseline information and help develop environmental management tools. We believe that long-term mesocosm experiments would unravel metal detoxification mechanisms at the cellular level and metal transfer rate at higher trophic levels in real-world environment.

Biotransformation of Pb and As from sewage sludge and food waste by black soldier fly larvae: Migration mechanism of bacterial community and metalloregulatory protein scales.

The accumulation and transformation of lead (Pb) and arsenic (As) during the digestion of sewage sludge (SS) by black soldier fly larvae (BSFL) remain unclear. In this study, we used 16 s rRNA and metagenomic sequencing techniques to investigate the correlation between the microbial community, metalloregulatory proteins (MRPs), and Pb and As migration and transformation. During the 15-day test period, BSFL were able to absorb 34-48 % of Pb and 32-45 % of As into their body. Changes in bacterial community abundance, upregulation of MRPs, and redundancy analysis (RDA) results confirmed that ZntA, EfeO, CadC, ArsR, ArsB, ArsD, and ArsA play major roles in the adsorption and stabilization of Pb and As, which is mainly due to the high contribution rates of Lactobacillus (48-59 %) and Enterococcus (21-23 %). Owing to the redox reaction, the regulation of the MRPs, and the change in pH, the Pb and As in the BSFL residue were mainly the residual fraction (F4). The RDA results showed that Lactobacillus and L.koreensis could significantly (P < 0.01) reduce the reducible fraction (F2) and F4 of Pb, whereas Firmicutes and L.fermentum can significantly (P < 0.05) promote the transformation of As to F4, thus realizing the passivation Pb and As. This study contributes to the understanding of Pb and As in SS adsorbed by BSFL and provides important insights into the factors that arise during the BSFL-mediated migration of Pb and As.