Analysis of the concentration of heavy metals in soil, vegetables and water around the bole Lemi industry park, Ethiopia

From contamination to detection: The growing threat of heavy metals

Heavy metals like lead, mercury, cadmium, and arsenic are environmental pollutants that accumulate in ecosystems and pose significant health risks to humans and wildlife, primarily through food chain contamination where plants absorb heavy metals, affecting their growth and threatening consumer health. Cognitive and cardiovascular functions are particularly affected by exposure to heavy metals even at low concentrations through the induction of oxidative stress. Various analytical techniques are used in measuring heavy metals in different environmental and biological samples. The atomic absorption spectroscopy (AAS) offers low cost, simplicity, and portability but lacks sensitivity for certain metals. Although more sensitive, the high cost of inductively coupled plasma mass spectrometry (ICP-MS) may limit laboratory accessibility. The inductively coupled plasma with atomic emission spectrometry (ICP-AES) is known for its broad dynamic linear range and ability to identify minute variations in concentration. Atomic fluorescence spectrometry (AFS) is considered a powerful tool for quantifying heavy metals due to its high sensitivity, low detection limits, and wide linear range. The current article reviews heavy metal pollution's impact on health and spectrometric techniques for the detection of these contaminants. This may help efforts of international, and regional policies towards preventing this health hazard problem.

Presence of Heavy Metals in Vegetables Irrigated with Wastewater-Impacted Rivers and Its Health Risks in Ethiopia: Systematic Review

Background

Vegetables play critical role in human nutrition and overall health. However, consumption of vegetables cultivated through wastewater-impacted river can be source of potentially toxic heavy metals, which can cause detrimental health effects when their concentration exceeds the recommended maximum levels. Despite growing body of evidence highlighting the dangers associated with heavy metal accumulation in vegetables, there remains critical gap in systematic assessments within Ethiopian context. Therefore, objective of this review is to reveal heavy metals concentrations in vegetables grown with wastewater-impacted river and assess associated public health risks.

Methodology

Research articles published in English were identified through systematic searching using electronic databases including PubMed, Google Scholar, WHO/FAO library, and searching from Google manually. The outcomes of interest were mean concentration of heavy metals in vegetables and associated health risks. Cross-sectional studies that met inclusion criteria were considered. Data were extracted by independent reviewers. Methodological quality of included studies was assessed using critical appraisal tools. Moreover, health risks of consumers were assessed through evaluating estimated daily intakes (EDI), Health Risk Index (HRI), and Hazard Index (HI).

Results

Nineteen articles were included in this systematic review. The findings revealed that the mean concentration of Pb, Cr, Cd, As, Hg, Cu, Ni, Zn, Mn, and Fe in tested vegetables ranged from: 0.28-7.68, 0.75-33.01, 0.14-3.93, 0.05-3.13, ND-4.25, 0.92-15.33, 2.13-13.1, 18.27-62.83, 8.83-331.8, and 177.8-1034.3 mg/kg (dry weight), respectively. The EDI of Pb, Cr, Cd, As, Hg, Cu, Ni, Zn, Mn, and Fe in vegetables was range from: 0.00104-0.0286, 0.00279-0.123, 0.00052-0.0146, 0.0000372-0.0116, 0.0124-0.0158, 0.00342-0.0439, 0.0079-0.0487, 0.068-0.23, 0.03-1.23, and 0.53-3.84 mg/kg/day, respectively. The HRI of toxic heavy metals for all vegetable types ranged as; Pb (0.26-7.15), Cr (0.00186-0.0820), Cd (0.52-14.6), As (0.12-38.7), and Hg (1.24-1.58). The HRI due to consumption of all vegetables was 35, 0.168, 46.6, 70, and 2.82 for Pb, Cr, Cd, As, and Hg, respectively indicating severe health impact except for Cr.

Conclusion

This review underscores health implications linked to consumption of vegetables cultivated using wastewater in Ethiopia. It revealed that the concentration of toxic heavy metals in vegetables grown with wastewater-affected water was higher than the maximum allowable safe limit set for edible vegetables by WHO that would be a public health risk.

Identification of different extracts and phytoconstituents of Callistemon viminalis Cheel for their anti-anxiety effects based on pharmacognostic, toxicological, and pharmacological strategies

Background

Psychiatric disorders like depression and anxiety are global challenges, exacerbated by the limitations of synthetic medications, including addiction and toxic side effects.

Methods

This study meticulously investigated the pharmacognostic, phytochemical, toxicological, and pharmacological properties of Callistemon viminalis Cheel. Toxicological assessments, including hemocompatibility assays, LD50 studies, FOB analysis, biochemical parameters, and structural integrity of vital organs, were conducted on aqueous, methanolic, chloroform, and petroleum ether extracts of leaves and stems. Phytochemical profiling via qualitative tests and GC-MS screened extracts for molecular docking against key receptors. Categorically screened extracts were evaluated for therapeutic potential against LPS-induced anxiety in mice.

Results

Toxicological evaluations on experimental animals demonstrated the safety of various extracts, evidenced by no in vitro and in vivo toxicity. GC-MS identified numerous phytochemicals that passed "Lipinski's Rule of Five." These compounds were screened for molecular docking, revealing significant binding affinities with CB1, SERT, α2A-AR, and GABAβ2 receptors, suggesting potential therapeutic effects against anxiety. The phytoconstituents with the highest docking scores, particularly in aqueous and methanolic extracts, were further validated for their therapeutic efficacy. Preliminary analysis based on the EPM test and serum cortisol levels confirmed these extracts' superior therapeutic effectiveness.

Conclusion

In conclusion, aqueous and methanolic extracts of Callistemon viminalis Cheel's leaf and stem showed promising potential as therapeutic interventions for anxiety disorders.

Evaluation of Some Potentially Toxic Elements and Associated Ecological and Health Risks in Topsoil Samples Adjacent to an Industrial Zone in Turkey

Potentially toxic element (PTE) pollution as a result of industrial activities remains a global problem that poses serious threats to human and ecological health. PTEs (Al, Fe, Ti, Mn, V, Zn, Cu, Cr, Ni, Pb, Co, and As) are metals or metalloids with biological toxicity. This study analyzed the concentrations of these PTEs and the physicochemical properties of topsoil samples collected from areas near industrial districts in the Samsun province of Turkey to evaluate ecological and health risks, estimating various indexes. The average concentrations of Al, Fe, Ti, Mn, V, Zn, Cu, Cr, Ni, Pb, Co, and As analyzed in 23 topsoil samples by energy-dispersive X-ray fluorescence spectrometry were found as 93,822, 82,410, 6623, 1642, 406, 278, 207, 149, 78, 68, 32, and 10 mg/kg dry weight, respectively. Zn, Cu, Cr, Ni, Pb, and Co levels exceed the maximum contaminant levels in the Turkish Regulation on the Control of Soil Pollution. The average pH values, organic matter, total organic carbon, and nitrogen measured in soil samples were 7.14, 6.11, 0.96, and 0.04%, respectively. The ecological and health evaluation reveals that the studied area is polluted with V, Cu, Zn, As, Ni, and Pb, which may pose a risk to people living in settlements near the industrial district.

Heavy metal pollution indices in soil and plants within the vicinity of the Gosa Dumpsite in Abuja, Nigeria

Heavy metal contamination in the soil and phytoremediation potential of the plants cultivated around the Gosa dumpsite were evaluated using pollution indices. The concentrations of heavy metals in the soil and plant samples were determined using an atomic absorption spectrophotometer (Agilent 280FS AA). The mean heavy metal contents in the upper and lower soil layers ranged from 0.37 to 1662.61 mg/kg and 0.32 to 1608.61 mg/kg, respectively, in ascending order of Cd < Cr < Cu < Ni < Pb < Co < Zn < Fe. The results revealed a steady depthwise decrease in heavy metal contents from the upper to lower soil layers. Co, Pb, Zn and Fe were introduced through geogenic and anthropogenic pathways, while Cr, Ni, Cu and Cd were derived mainly from anthropogenic sources. The mean soil enrichment in the heavy metals ranged from 0.96 to 237.04 in the ascending order of Fe > Co > Pb > Zn > Cu > Cd > Cr > Ni. The soil was moderately polluted with Co, Cu, Pb, Zn, Fe and Cd but heavily polluted with Cr and Ni. The results revealed that 37.5% of the sites studied had pollution load indices greater than 1.0, indicating gradual deterioration in overall soil quality. The concentrations of Pb, Cd and Fe exceeded the recommended limits for the five plant species assessed. The transfer factor (TF) values of okra plant 1 (0.7536), water hyacinth (1.3768), and Amaranthus hybridus (0.9783) indicated excellent Cd phytoremediation potential. Okra Plant, water hyacinth and Amaranthus hybridus had excellent potential for phytoremediation of Cu, Fe and Pb, respectively. The study area was strongly enriched in Fe, Cd, Cr, and Ni, suggesting some degree of soil pollution, while the plants demonstrated an excellent capacity to accumulate Cd, Cu, Fe and Pb. This dumpsite should be adequately monitored while proper remediation measures are adopted by government authorities.

Transformation of heavy metals from contaminated water to soil, fodder and animals

A serious environmental problem that threatens soil quality, agricultural productivity, and food safety is heavy metal pollution in water sources. Heavy metal pollution is the main problem in tehsil Pasrur, Sialkot, Pakistan. Present study was arranged to notice the heavy metals in water, soil, forages and buffalo milk. There are seven sites that were used for this experiment. Highest malondialdehyde (MDA) contents (3.00 ± 0.01) were noticed in barseem roots at site 7. Ascorbate Peroxidase (APX) was reached at its peak (1.93 ± 0.01) at site 7 in the fresh barseem. Maximum protein contents (0.36 ± 0.01) were observed in fresh plant samples at site 2. Site 3's buffalo milk samples had the highest Ni content (7.22 ± 0.33 ppm), while Site 3's soil samples had the lowest Cr content (8.89 ± 0.56 ppm), Site 1's plant shoots had the lowest Cr content (27.75 ± 1.98 ppm), and Site 3's water had the highest Cr content (40.07 ± 0.49 ppm). The maximum fat content (5.38 ± 2.32%) was found in the milk of the animals at site 7. The highest density (31.88 ± 6.501%), protein content (3.64 ± 0.33%), lactose content (5.54 ± 0.320%), salt content (0.66 ± 0.1673%), and freezing point (- 0.5814 ± 0.1827 °C) were also observed in the milk from animals at site 7, whereas site 5 displayed the highest water content (0.66 ± 0.1673%) and peak pH value (11.64 ± 0.09). In selected samples, the pollution load index for Ni (which ranged from 0.01 to 1.03 mg/kg) was greater than 1. Site 7 has the highest conductivity value (5.48 ± 0.48). Values for the health risk index varied from 0.000151 to 1.00010 mg/kg, suggesting that eating tainted animal feed may pose health concerns. Significant health concerns arise from metal deposition in the food chain from soil to feed, with nickel having the highest health risk index.

Soil pollution indices and health risk assessment of metal(loid)s in the agricultural soil of pistachio orchards

Elevated levels of metal(loid)s in soil may pose potential threats to the ecosystem and can be harmful for human health. The concentrations of As, Cd, Pb, Cr and Ni were determined in agricultural soil collected from 45 pistachio orchards around Feizabad city, Khorasan Razavi province, Iran using ICP-OES. Also, soil pollution indices including contamination factor (CF), pollution load index (PLI) and geo-accumulation index (Igeo) were evaluated. In addition, non-carcinogenic and carcinogenic risk indices were estimated. The mean concentrations of metal(loid)s were in the order of Ni = 466.256 > Cr = 120.848 > Pb = 12.009 > As = 5.486 > Cd = 0.394 mg/kg. Concentrations of As, Cd and Pb in the soil samples were within their respective permissible limits set by World Health Organization (WHO). But concentrations of Cr and Ni in 84.4 and 100% of the samples, respectively exceeded the WHO allowable limits. The CF, PLI and Igeo showed that soil of some of the pistachio orchards was contaminated with some metals. The possible sources of the metals in the soil are application of pesticides, chemical fertilizers, manures as well as irrigation water. Hazard quotient (HQ) ad Hazard index (HI) values from soil of all the orchards were found to be well below the respective threshold limit (1), suggesting that there is no immediate non-cancer threat arising from the contamination at all the orchards with metal(loid)s for children and adults. The highest cancer risk values (1.13E-02 for children and 1.25E-03 for adults) were estimated for Ni in the soil. Collectively, this study provides valuable information to improve the soil in the pistachio orchards to reduce metal(loid)s contamination and minimize the associated health risks to the population in the area.

Combined effect of endophytic Bacillus mycoides and rock phosphate on the amelioration of heavy metal stress in wheat plants

BACKGROUND

Zinc (Zn) and nickel (Ni) are nutrients that are crucial for plant growth; however, when they are present at higher concentrations, they can cause toxicity in plants. The present study aimed to isolate plant growth promoting endophytic bacteria from Viburnum grandiflorum and assess its plant and defense promoting potential alone and in combination with RP in zinc (Zn) and nickel (Ni) toxic soil. The isolated endophytic bacteria were identified using 16s rRNA gene sequencing. For the experiment, twelve different treatments were applied using Zn, Ni, isolated endophytic Bacillus mycoides (Accession # MW979613), and rock phosphate (RP). The Ni, Zn and RP were used at the rate of (100 mg/kg) and (0.2 g/kg) respectively. A pot experiment with three replicates of each treatment was conducted using a complete randomized design (CRD).

RESULTS

The results indicated that Ni (T5 = seed + 100 mg/kg Ni and T9 = seed + 100 mg/kg Zn) and Zn concentrations inhibited plant growth, but the intensity of growth inhibition was higher in Ni-contaminated soil. Bacillus mycoides and RP at 100 mg/Kg Zn (T12 = inoculated seed + 100 mg/kg Zn + RP0.2 g/kg.) increased the shoot length, leaf width, protein and sugar content by 57%, 13%, 20% and 34%, respectively, compared to the control. The antioxidant enzymes superoxide dismutases (SOD), peroxidase (POD) were decreased in contaminated soil. Furthermore, Ni and Zn accumulation was inhibited in T11 (seed + 100 mg/kg Zn + RP0.2 g/Kg) and T12 (inoculated seed + 100 mg/kg Zn + RP0.2 g/Kg) by 62 and 63% respectively. The Cu, Ca, and K, contents increased by 128, 219 and 85, Mn, Na, and K by 326, 449, and 84% in (T3 = inoculated seed) and (T4 = inoculated seed + RP 0.2 g/Kg) respectively.

CONCLUSIONS

Ni was more toxic to plants than Zn, but endophytic bacteria isolated from Viburnum grandiflorum, helped wheat (Triticum aestivum) plants and reduced the toxic effects of Ni and Zn. The effect of Bacillus mycoides was more prominent in combination with RP which promoted and suppressed heavy-metal toxicity. The reported combination of Bacillus mycoides and RP may be useful for improving plant growth and overcoming metal stress.