Low Concentrations Of Heavy Metals Research Articles

Appraisal and validation of a method used for detecting heavy metals in poultry feed in Bangladesh.

Low concentrations of heavy metals are toxic and pose a serious threat to human health and the environment. Therefore, regular assessments of the toxic metal content in poultry feed are crucial for evaluating feed quality and customer safety. It is difficult to determine the heavy metals in the poultry feed at the trace amount. Therefore, this study aimed to validate this method through the detection of three heavy metals, chromium (Cr), cadmium (Cd), and lead (Pb), in poultry feed samples. Graphite furnace atomic absorption spectrometry (GF-AAS) method was used to analyze the heavy metals in poultry feed according to the guidelines given by the Council Directive 333/2007/EC, Commission Decision 657/2002/EC. In this study, various parameters such as linearity check, limit of detection (LOD), limit of quantification (LOQ), recovery percentage, precision checks, repeatability, reproducibility, and uncertainty measurement were considered to validate and assess the method following international guidelines. Heavy metals, such as Pb, Cr, and Cd, were analyzed from the feed samples in the laboratory using the GF-AAS method (Model: AA-7000 Shimadzu, Japan) with high purity argon as the inert gas, and the absorbance was read at wavelengths of 283.0, 357.9, and 228.8 nm, respectively. The coefficient of variation (CV%) for system suitability and precision data was <10% for all the metals (Pb, Cr, and Cd) detected in this study. The overall CV% of repeatability and reproducibility ranged from 8.70% to 8.76% and 8.65% to 9.96%, respectively. The linearity of the calibration curves was excellent (r2 > 0.999) at various concentration levels for the three different metals. The recovery (%) was found to be 94.53, 93.97, and 101.63% for Pb, Cr, and Cd, respectively. The LOD values in feed were 0.065, 0.01, and 0.11 mg/kg, and the LOQ values were 0.22, 0.03, and 0.38 mg/kg for Cr, Cd, and Pb, respectively. The values recorded for the measurement uncertainty (%) were 11.48, 4.43, and 12.42% for Cr, Cd, and Pb, respectively. The results show that these study criteria or parameters have met the validated or acceptable range. Therefore, it is a reliable technique that can be used undoubtedly for the routine analysis of heavy metals in poultry feed samples across the globe.

The emerging potential of natural and synthetic algae-based microbiomes for heavy metal removal and recovery from wastewaters

Heavy Metal (HM) bioremoval by microbes is a successful, environment-friendly technique, particularly at low concentrations of HMs. Studies using algae, bacteria, and fungi reveal promising capabilities in isolation and when used in consortia. Yet, few reviews have emphasized individual and collective HM removal rates and the associated mechanisms in natural or synthetic microbiomes. Besides discussing the limitations of conventional and synthetic biology approaches, this review underscores the utility of indigenous microbial taxon, i.e., algae, fungi, and bacteria, in HM removal with adsorption capacities and their synergistic role in microbiome-led studies. The detoxification mechanisms studied for certain HMs indicate distinctive removal pathways in each taxon which points to an enhanced effect when used as a microbiome. The role and higher efficacies of the designer microbiomes with complementing and mutualistic taxa are also considered, followed by recovery options for a circular bioeconomy. The citation network analysis further validates the multi-metal removal ability of microbiomes and the restricted capabilities of the individual counterparts. In precis, the study reemphasizes increased metal removal efficiencies of inter-taxon microbiomes and the mechanisms for synergistic and improved removal, eventually drawing attention to the benefits of ecological engineering approaches compared to other alternatives.

Spatiotemporal variations of heavy metal historical accumulation records and their influencing mechanisms in the Yangtze River Estuary

Complex transformations of heavy metals in the mega-river-estuary continuum limit our understanding of their pollution history. This study investigated sedimentary compositions of heavy metals, major elements, total organic carbon, grain size, and radionuclides to study spatiotemporal variations in heavy metal accumulation patterns and their controlling mechanisms in four sediment cores (E1-E4) from the Yangtze River Estuary (YRE). Results show that only E3 in the distal YRE front mirrors well the heavy metal pollution history due to its continuous deposition in a stable sedimentary environment, while E1 and E2 record the influence of riverine and estuarine projects and processes apparently. E1 in the proximal YRE front registers intense human disturbance through sediment dredging and dumping activities to produce a thick layer of abnormal low 210Pbex and minor heavy metal concentrations. E2 in the intermediate YRE front demonstrates the recently increasing influence of reduced sediment discharge by its upcore coarsening trend with decreased heavy metal concentrations. Flood and storm events left different imprints in core sediments of E2 and E3 by their coarse stratal units with fewer heavy metal concentrations. The source analysis indicates that heavy metals in estuarine sediments mainly come from natural processes but are significantly affected by human activities. A direct linkage of the heavy metal accumulation history with the socioeconomic development in recent decades is found by a comparison study of core data from the tidal river to the estuary, albeit with a remarkable spatiotemporal difference, which is jointly determined by grain size, offshore distance, hydrodynamic condition, depositional status, and sedimentation rate besides estuarine processes. This warns us to carefully interpret the heavy metal history from single or sparse core data in a mega estuary system with intense natural forces and human disturbances analogous to the YRE.

Comprehensive evaluation of functional components, biological activities, and minerals of yam species (Dioscorea polystachya and D. alata) from China

Yam (Dioscorea spp.) is a multi-species and multi-purpose tuber crop. In this study, the contents of functional components, biological activities, and mineral elements were evaluated in the yam tubers of D. polystachya and D. alata cultivated widely varieties in China. Significant differences in allantoin contents were observed between interspecific and intraspecific yam varieties, and allantoin contents in the four varieties of D. polystachya were significantly higher than those in the D. alata group; however, no significant difference was observed for dioscin levels in all accessions. Furthermore, the phenol and flavonoid contents of D. alata were higher than those of D. polystachya. Protein profiles obtained using nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS) revealed that the levels of proteins related to allantoin, total phenols, and total flavonoids also changed. In addition, both D. polystachya and D. alata tubers contained highly essential minerals, such as high potassium and magnesium, and low heavy metal contents within the specified pollutant content range. This study provides a foundation for the functional food development of Chinese yams and a reference for breeding high-quality yam varieties.

Potential Applications of Frass Derived from Black Soldier Fly Larvae Treatment of Food Waste: A Review.

The disposal of large amounts of food waste has caused serious environmental pollution and financial losses globally. Compared to alternative disposal methods (landfills, incineration, and anaerobic digestion), composting by black soldier fly larvae (BSFL) is a promising alternative for food waste management. Despite extensive research into larval biomass, another valuable by-product generated from BSFL composting is BSFL frass. However, limited information is available for its potential application. The applications of BSFL frass can be intensified by understanding its physicochemical characteristics, benefits, and challenges of BSFL frass derived from food waste. BSFL frass is harvested after 9–23 days of the experiment, depending on the substrate used in the composting process. The generated BSFL frass could exceed 33% of the original weight of the substrate. The physicochemical characteristics of BSFL frass are as follows: the temperature after harvest is 24 °C to 27 °C, pH is 5.6–8.0, moisture content is 30 to 72%, C/N ratio is 8:1 to 27:1, high nitrogen, phosphorus, and potassium (NPK) content, and low heavy metal content. This paper reviews the characteristics, benefits, and application of BSFL frass. It will also investigate the challenges of using food waste substrates to produce BSFL frass, as well as the best way to pre-treat the food waste substrate and post-treat the BSFL frass.

Theoretical design of phononic crystal cavity sensor for simple and efficient detection of low concentrations of heavy metals in water

Theoretical design of phononic crystal cavity sensor for simple and efficient detection of low concentrations of heavy metals in water

Spectral features of Fe and organic carbon in estimating low and moderate concentration of heavy metals in mangrove sediments across different regions and habitat types

Soil or sediment spectral reflectance do not directly reflect information of spectrally featureless heavy metals. With mangrove sediment samples collected in five regions and four habitat types, this study aimed to explore the spectral features related to spectrally active constituents (Fe and organic carbon (OC)) in estimating low and moderate concentrations of four heavy metals (Cr, Ni, Cu and Pb). A total of 27 modeling strategies using XGBoost (extreme gradient boosting) model were compared for estimating each heavy metal: three types of spectral features (Fe, OC and heavy metal) * three spectral transformation methods (Log(1/R), first derivative (FD) and continuous wavelet transform (CWT)) * three variable selection methods (genetic algorithm (GA), successive projection algorithm (SPA) and recursive feature elimination (RFE)). The results showed that the combination of CWT and RFE was recommended for heavy metal estimation, and the ranking of model accuracy was Cu > Pb > Ni > Cr. The optimal XGBoost model was found using spectral features related to Fe for Cr (RVal2(determination coefficient of independent validation) = 0.42, RMSE (root mean square error) = 0.32 and RPIQ (the ratio of performance to interquartile range) = 1.53) and Cu estimation (RVal2 = 0.87, RMSE = 0.19 and RPIQ = 2.20), spectral features related to OC for Ni estimation (RVal2 = 0.63, RMSE = 0.26 and RPIQ = 2.38) and spectral features related to Pb itself for Pb estimation (RVal2 = 0.82, RMSE = 0.23 and RPIQ = 2.59). Moreover, the XGBoost model transferability across different habitat types outperformed that across different regions and data ranges of Fe and OC. We conclude that the modeling strategy using spectral features related to spectrally active constituents has great potentials in quantifying low and moderate concentration of sediment heavy metals, and the samples with high Fe concentration (31.62–37.29 g kg−1) are recommended to improve estimation accuracy of low and moderate concentrations of heavy metals, which could provide sampling strategy development and early warning of heavy metal pollution in mangrove ecosystem.

Heavy Metal Contamination of Pleurotus Tuberregium Sclerotia (Osu) Consumed in Enugu, South East Nigeria

Heavy metal contamination of food is a global public health problem especially in developing countries. The WHO 2015 report on global burden of food contamination stated that an estimated 600 million people are affected resulting in 420,000 deaths annually with children under 5 years of age constituting 40% of burden and 125,000 deaths annually. The present study was aimed at determining the concentrations of Nickel (Ni), Cadmium (Cd), Lead (Pb) and Chromium (Cr) in some samples of wild type pleurotus tuberregium sclerotia consumed in Enugu, Southeast Nigeria. Heavy metal concentrations were determined using Atomic Absorption Spectrometer (AAS 240FS) Varian, Varian Inc, Japan. The range for concentration of Nickel was (3.29+0.63-3.67+0.00), Cd (0.002+0.01-0.005+0.0), Pb(0.04+0.03)-0.07+0.02) and Cr(0.46+0.26-1.0+0.62),ppm respectively. These are within the WHO tolerable concentrations of Ni, Cd, Pb and Cr in food. These findings shows that pleurotus tuberregium sclerotia consumed in Enugu has lower concentrations of heavy metals compared to the WHO recommended values.

Ecophysiological Parameters of Medicinal Plant Filipendula vulgaris in Diverse Habitat Conditions.

Simple SummaryDropwort (Filipendula vulgaris Moench) is a perennial plant (hemicryptophyte), growing on xerothermic grasslands Festuco-Brometea and changing-wet Molinia meadows in the Eurasian area. Due to the production of active substances, the species is used in folk medicine and phytotherapy. This study includes determining which of the two different habitats occupied by F. vulgaris creates better conditions for its growth and development. Selected physiological parameters of dropwort plants (PSII activity, chlorophyll content, electrolyte leakage, hydrogen peroxide content, and biomass), the occurrence of mycorrhiza, and soil characteristics were investigated. Soil analysis showed a higher content of nutrients in grasslands, and a higher content of heavy metals in meadows. Plants of F. vulgaris growing in the wet meadows achieved a significantly lower mass compared to plants growing in grasslands. The colonization degree of F. vulgaris by arbuscular mycorrhizal fungi (AMF) from both stands oscillated around high values; dropwort formed the Arum type of mycorrhiza. A much higher content of chlorophylls was observed in plants from grasslands. F. vulgaris showed different photosynthetic activity depending on the habitat. Based on chlorophyll fluorescence imaging, higher activity was found in plants from grasslands, compared to plants from meadows, but in specimens from grasslands, there are symptoms of damage to the PSII system. The analyses carried out showed that better conditions for growth and physiological activity of this species are probably associated with grasslands on a calcareous substrate, although the irradiance stress of excess light is visible, manifested, e.g., by little dysfunction of photosynthetic structures.This study attempts to determine which of the habitats occupied by Filipendula vulgaris creates better conditions for its growth and development. Selected physiological parameters—PSII activity, chlorophyll content, electrolyte leakage, hydrogen peroxide content as well as biomass, the occurrence of mycorrhiza, and soil characteristics—were investigated. Grassland soils had a higher content of macronutrients and a lower concentration of heavy metals. The degree of colonization of F. vulgaris by AMF (Arum type) oscillated around high values in both types of stands. Plants growing on xerothermic grasslands achieved much better fluorescence parameters than those collected from meadows. Similar results were obtained from the analysis of chlorophyll content. The destabilization degree of cell membranes was significantly higher in plants collected in meadows than in grasslands. Biomass analysis showed higher values of these parameters in grassland plants. In the case of the parameters of fluorescence emission, plants growing on grasslands achieved significantly lower values than plants collected from meadows. The analyses carried out showed that better conditions for growth and physiological activity of F. vulgaris are probably associated with grasslands on a calcareous substrate.

Valorization of coffee industry wastes: Comprehensive physicochemical characterization of coffee silverskin and multipurpose recycling applications

Every year, the coffee supply chain produces tons of waste materials from the processing of the coffee bean. Coffee silverskin (CS) is the only waste product from the coffee bean roasting phases but as roasting is a key step in obtaining the coffee beverage, there are tons of CS collected and thrown away by coffee roasting industries. This study is based on the characterization of this integument, with a view to its use in nutritional, nutraceutical and industrial fields. From the results obtained, silverskin can be used in the food sector for its nutritional profile with a good amount of protein (18.9%) and total dietary fiber (34.7%) andits low-fat content (3.0%). Food safety was also determined by evaluating the low levels of contaminants such as ochratoxin A (OTA) and acrylamide (AA), with values < 0.1 mg/kg and <0.02 mg/kg respectively. Low concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) completed the safety-related overview in terms of CS contamination. For the nutraceutical aspect, an in-silico analysis of the peptide fraction was proper to evaluate the presence of angiotensin-converting enzyme (ACE) inhibitory peptides, antioxidants and dipeptidyl peptidase (DPP) IV inhibitors with promising uses for the treatment of diabetes and its side effects. Finally, through morphological-structural characterization of CS, the main constituents such as lignin, cellulose and hemicellulose were identified spectrally by Fourier transform infrared spectroscopy (FT-IR) and solid-state CP/MAS 13C NMR spectroscopy. The CS thermostability was monitored by thermogravimetric (TG) analysis, and the tegument surface was evaluated by Scanning Electron Microscopy (SEM) and volumetric nitrogen adsorption analysis. This information provides a broader view of the possible uses of CS as a filler for biocomposite materials. Therefore, from the perspective of recovering waste materials from food supply chains, coffee silverskin could be a good product to focus on.

Application of Composited Municipal Refuse Dump Site Soil, Orange, Potato and Pineapple Peels in the Control of Root Knot Nematode (Meloidogyne Incognita) Infecting Carrots (Daucus Carota L.)

Meloidogyne incognita is known to be a foremost pest of carrot in Nigeria. It is a component to appraise in carrot production. Application of synthetic nematicides as control measures is unsafe to humans and detrimental to the environment. Development of safe control process is worthwhile. Effect of three peels (potato, pineapple, orange) and composited soil from municipal refuse dump site was assessed and compared with carbofuran a standard synthetic nematicide at four different doses (0, 1500, 2000, 2500g and 2.0kg/a. i/ha, 1.5kg/a. i/ha, 1.0kg/a. i/ha and 0kg/a. i/ha for carbofuran) on carrot plants. The concentrations of heavy metals like Cd, Pb, Ni, Cu, Cr, Mn, Zn and Fe in the composited soil was determined with Atomic Absorption Spectrophotometer (AAS). Experimental pots were inoculated with approximately 2000 M. incognita juveniles, in a randomized complete block design experiment. The composited municipal refuse soil was analysed for the presence of fungi and bacteria using molecular methods based on 16S rRNA gene sequencing. Reproduction and multiplication of M. incognita was significantly (p&lt;0.05) low with all the treatment materials. Best inhibitory effect was observed in the soil of carrot plants treated with composited soil which had 49 nematode populations at harvest rather than 4606 recorded in untreated plants. Equally, heavier carrots were harvested in plants administered with composited soil (1309.6 gram), while the control plants had poor weight (312.7 gram). Performance of each waste material was quantity dependent. Gene sequencing revealed the presence of Pseudomonas alcaligenes strain ATCC 14909, P. putida strain ATCC 12633, P. aeruginosa strain ATCC 10145, Pseudomonas stutzeri NBRC 14165, Acinetobacter venetianus ATCC 31012, Enterobacter cloacae ATCC 130047, Streptomyces spp B7-3TC02, Bacillus subtilis NBRC 13719, Aspergillus niger strain MPVCT 158, Penicillium georgiense strain EV 24 and Rhizopus oryzae strain ATCC 20344, which are beneficial soil microorganisms. The metal concentration analysis of the composited municipal refuse dump soil exhibited low concentrations of heavy metals which ranges from 0.002-1.03 mg/kg with Zinc (Zn) having the highest concentration. The waste materials are cheap and ecofriendly option that can be adopted as soil amendment in M. incognita infested fields to significantly boost yield in carrot production and reduce reliance on mineral fertilizer. The peels, as well as composited municipal refuse dump soil can be used to improve soil properties and substitute lost nutrients to enhance crop production, and at the same time mitigate the environmental consequences of inappropriate waste disposal problems in Nigeria.

Porosity of municipal solid waste incinerator bottom ash effects on asphalt mixture performance

Dispose and utilization of municipal solid waste incinerator bottom ash (MWSIBA) is one of the imperative issues in environmental protection. The applicability of substitution for natural aggregate with MWSIBA in asphalt mixture was investigated by the performance and micro structure of asphalt mixtures with diverse porosity levels of MWSIBA (varying the replacement percentage). The effects of porosity of MWSIBA on asphalt mixture performance were captured by determination of Marshall stability, tensile strength, dynamic stability and the maximum flexural-tensile strain. The horizontal vibration extraction procedure test was implemented for the heavy metal leaching concentration to evaluate the environmental safety of MWSIBA asphalt mixture. Chemical and micro-morphologic characterization for MSWIBA were conducted to explore the mechanism of moisture damage resistance of asphalt mixture. Results indicated that porosity and replacement rate of MWSIBA exerted impacts on properties of asphalt mixture. The rutting resistance of asphalt mixture decreased due to the addition of MWSIBA, resulting in a reduction in high temperature performance. MWSIBA with porosity no less than 19% was beneficial to the improvement of moisture susceptibility and low temperature performance of asphalt mixture, while high mixing amount of MWSIBA was unfavorable to the properties of asphalt mixture. The water immersion stimulated the hydration reaction in MWSIBA, leading to the formation of C-(A)-S-H gel with strong cementation property, which enhanced the adhesion between MWSIBA and asphalt binder. MWSIBA asphalt mixture presented lower heavy metal concentration and better environmental safety than MSWIBA.

Depuration of Heavy Metals with Nanoparticle-Sized Active Charcoal from Coconut Shell (Cocos nucifera) in Blood Cockles (Anadara granosa)

Anadara granosa are one of the benthic organisms that are frequently reported because contained heavy metals because of water pollution. This is because A. granosa is a feeder filter so that accumulates heavy metals in its body. Reduce the levels of heavy metals with activated charcoal from coconut shells in the absorbance process using the depuration method. It is re-optimized with the use of nano-active charcoal. The goal was to determine the effect of concentrations of nano-active charcoal from coconut shells on the heavy metal content of A. granosa. Stages of this reserch, namely charcoal activation, ultrasonication, SEM testing, blood shell depuration, and heavy metal testing. Based on the results of the Scanning Electron Microscope (SEM) Test it is known that the charcoal particles are sized 10-9 nm. The types of heavy metals found included hydrargyrum (Hg) 0.0009 mg/kg, cadmium (Cd) 0.62 mg/kg, and plumbum (Pb) 1.82 mg/kg. Heavy metals with lowest content is found in P5 (active charcoal concentration of 15% of the sample weight) of mercury (Hg) 0.0002 mg/kg; cadmium (Cd) 0.1 mg/kg; and lead (Pb) 0.373 mg/kg. This shows that the higher concentraion of activated charcoal given, the lower heavy metal content.

Influence of Spirulina Platensis in the composition of feed on the content of heavy metals in rabbit meat

An important area for the further development of animal husbandry is to provide humanity with environmentally friendly food. One way to reduce the content of heavy metals in livestock products in general and meat in particular is to feed some feed products that have sorbent properties. For this purpose, a scientific and economic experiment was conducted to study the effect of feeding compound feeds containing 0.5–2% Spirulina platensis to rabbits raised for meat. The experimental period of the research lasted from the 60th to the 120th day of life of young rabbits and ended with a control slaughter. During this period, the live weight of the rabbits, their safety and the amount of feed consumed were monitored. During the control slaughter, the chemical composition of the longest back muscle was studied, as well as the content of Lead and Cadmium. According to the results ofthe experiment it was found that the introduction of compound feed rabbits Spirulina platensis in doses of 0.5–2.0% helps to improve their growth, reduce the content of Cadmium and Lead in meat, reduce the fat content in it and increase the proportion of dry matter and protein. It should be noted that the highest productivity of rabbits was achieved at a feed content of 1.5% of Spirulina platensis, ahead of control counterparts by 7.8% (P&lt;0.01). Instead, the lowest concentration of heavy metals in meat was recorded at the content of 2.0% of the specified feed: Cadmium by 34.1% (P&lt;0.01), and Lead – by 25.9% (P&lt;0.001) less than the control indexes. As for the chemical composition of meat, the highest protein and the lowest fat in it was recorded at 1.5% Spirulina platensis in the feed. Compared to control animals, rabbit meat in this group contained 1.2% more protein and 0.7% (P&lt;0.01) less fat. Thus, 1.5% of Spirulina platensis in the feed for rabbits raised for meat can be considered the optimal proportion. Key words: rabbits, Spirulina platensis, live weight gain, productivity, Cadmium, Lead, meat.

Assessment of Heavy Metals Contamination in Fish Cultured in Selected Private Fishponds and Associated Public Health Risk Concerns, Dar es Salaam, Tanzania

Environmental pollution caused by the increase of heavy metals concentration in aquatic and terrestrial environments is a growing global concern due to their nature and toxicity. This paper aimed to undertake an assessment of the quality of fish cultured in individual-owned fishponds in Dar es Salaam city and their associated health risks. Data collection involved sampling and quantification of the quality of two species of fish, which were African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus), from three selected fish ponds in Dar es Salaam and chemical analysis involved heavy metals analysis in gills, fins, guts, and muscles. The concentrations of heavy metals were analyzed using Atomic Absorption Spectrophotometer (AAS). Results of this study indicated that the concentrations of trace metals in fish tissues varied considerably. The fish gills had higher concentrations of Cr, Zn, Cu, and Pb than the fins and guts, while muscles had the lowest concentrations of heavy metals in all fish species. A highly significant difference in the heavy metal concentrations measured in both catfish and tilapia tissues was observed with a P value of less than 0.05. Individual risk assessment showed that there was a minimal risk caused by the concentrations of Cr, Zn, and Cu upon consumption of fish; however, the combined effect was higher caused by the high concentration of Pb in fish organs. Monitoring of fish quality in privately owned fish ponds is recommended to safeguard consumers.

Fabrication of hollow-fiber nanofiltration membrane with negative-positive dual-charged separation layer to remove low concentration CuSO4

To apply membrane separation technology to the treatment of low-concentration heavy metal ion wastewater, it is essential to fabricate a nanofiltration (NF) membrane with high flux and excellent rejection. In this work, organics (polyethyleneimine, gallic acid, trimesic acid, and polyacrylic acid) with different charges were successively introduced onto the outer surface of hollow-fiber NF membranes via chemical modification. That regulated the membrane surface charge under the premise of maintaining a loose separation layer. A negative-positive dual-charged membrane with a large mean effective pore size and long charged channels was successfully constructed. The evolution regularity of the microstructure of the separation layer was explored. The relation between a microstructure for a negative-positive dual-charged layer and low-concentration CuSO4 removal was interpreted. An effective removal (94.2%) was achieved while maintaining a high permeability (29.6 L m−2 h−1 bar−1). Also, the as-prepared membrane showed good acid resistance and an excellent anti-fouling property and regeneration ability after cleaning by sulfuric acid. The flux recovery ratio and rejection recovery ratio were as high as 96.9% and 99.2% respectively. This work provides a reference for fabricating high performance hollow-fiber NF membranes to effectively remove heavy metal ions with low-concentration.

Assessment of vegetation, soil nutrient dynamics and heavy metals in the Prosopis juliflora invaded lands at semi-arid regions of Southern India

Prosopis juliflora is one among the dominant invasive plant species widely distributed in arid and semi-arid regions of the world. The invasion inflicts varying degrees of ecological implications, albeit certain socio-economic benefits are being derived by the local community. In Southern India, the vast semi-arid plains lying east of the Western Ghats mountain range, has ideally favored extensive invasion of P.juliflora. In last three decades, the invasion had spread to the pasture and arable lands that are lying disconnected from the mainstream irrigation system. Therefore, in the context of worsening food security, ecological imbalance, increasing soil degradation and the climate change, the prospects of converting the P.juliflora invaded lands to silivicultural/agricultural activity has been envisaged as a viable alternative. In this scenario, present study is an imperative attempt to understand the coexisting vegetation, soil nutrient profile and heavy metal concentrations in the P.juliflora invaded lands at Tiruchirappalli and Pudukkottai regions of Southern India. Composite soil samples were collected from 60 sites (spread across 4800 km2 including urban–rural gradient) at the depths 0 – 10, 10 – 20, and 20–30 cm. The influence of P.juliflora stand density, litter fall, species diversity, soil texture on the soil physico-chemical properties including soil pH, electrical conductivity (EC), available macro nutrients (N, P and K), organic carbon and heavy metals [Fe, Cu, Cd, Cr, Ni, and Pb] were investigated. The results revealed considerable enrichment of macronutrients in the invaded lands, in contrast to non-invaded lands (p < 0.001***). Of the observed attributes, step wise regression indicated stand density and litter fall as prominent factors (R = 0.7903 and 0.6479 respectively) augmenting soil macro nutrients. In the case of heavy metals, observations along the urban–rural gradient indicated comparatively lower concentrations of heavy metals in the P.juliflora invaded lands of urban areas, hinting the possible of bio-sorption capacity of P.juliflora. Overall, the results infer an optimistic note for potential conversion of the P.juliflora invaded lands to silivicultural maneuvers, prioritizing the native flora.

Recent developments in microextraction techniques for detection and speciation of heavy metals

Analysis of heavy metals and their species in complex samples such as environment, biology and medicine is be of paramount importance due to their toxicity, persistence, and bioaccumulation. Considering the complexity of the sample matrix and the low concentration of heavy metals, sample preparation step should be exerted before analysis. Microextraction techniques have received extensive attention due to its miniaturization, quickness, low cost, environmental friendliness, and satisfactory extraction performance. So far, various formats based on microextraction techniques have been developed and applied to entrap heavy metals and related species. This review mainly concentrates on the recent development and applications of microextraction techniques including solvent-based liquid-phase microextraction and sorbent-based solid-phase microextraction for the detection and speciation of heavy metals in water, food, sediment, soil, hair, urine, and serum samples.

Bacterial community response to chronic heavy metal contamination in marine sediments of the East China Sea

Marine sediments act as a sink for various heavy metals, which may have profound impact on sedimentary microbiota. However, our knowledge about the collaborative response of bacterial community to chronic heavy metal contamination remains little. In this study, concentrations of seven heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn) in sediments collected from the East China Sea were analyzed and Illumina Miseq 16 S rRNA sequencing was applied to characterize the structure of bacterial community. Microbiota inhabiting sediments in the East China Sea polluted with heavy metals showed different community composition from relatively pristine sites. The response of bacterial community to heavy metal stress was further interrogated with weighted correlation network analysis (WGCNA). WGCNA revealed ten bacterial modules exhibiting distinct co-occurrence patterns and among them, five modules were related to heavy metal pollution. Three of them were positively correlated with an increase in at least one heavy metal concentration, hubs (more influential bacterial taxa) of which were previously reported to be involved in the geochemical cycling of heavy metals or possess tolerance to heavy metals, while another two modules showed opposite patterns. Our research suggested that ecological functional transition might have occurred in East China Sea sediments by shifts of community composition with sensitive modules majorly involved in the meaningful global biogeochemical cycling of carbon, sulfur, and nitrogen replaced by more tolerant groups of bacteria due to long-term exposure to low-concentration heavy metals. Hubs may serve as indicators of perturbations of benthic bacterial community caused by heavy metal pollution and support monitoring remediation of polluted sites in marine environments.

Spatial Distribution and Migration Characteristics of Heavy Metals in Grassland Open-Pit Coal Mine Dump Soil Interface.

The open-pit coal mine dump in the study area contains many low-concentration heavy metal pollutants, which may cause pollution to the soil interface. Firstly, statistical analysis and geostatistical spatial interpolation methods described heavy metal pollution’s spatial distribution. The mine dump heavy metal pollution distribution is strongly random due to disorderly piles, but it is closely related to slope soil erosion. Furthermore, the soil deposition area is where pollutants accumulate. For example, all heavy metal elements converge at the bottom of the dump. Usually, the pollution in the lower part is higher than that in the upper part; the pollution in the lower step is higher than the upper step; the pollution in the soil deposition locations such as flat plate and slope bottom is higher than the soil erosion locations such as slope tip and middle slope. Finally, the hyperspectral remote sensing method described heavy metals pollution’s migration characteristics, that the pollutants could affect the soil interface by at least 1 km. This study provides a basis for preventing and controlling critical parts of mine dump heavy metal pollution and pollution path control.