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Heavy metal pollution poses a serious threat to the environment and human health. Guizhou is a province with apparent regional features of heavy metal pollution such as lead, zinc, mercury, and arsenic in agriculture and mining soils. The coefficient of variation results showed that heavy metal pollution in the soils of agricultural planting areas and mine caves was closely related to human activities, and arsenic and zinc were greatly affected by human activities. In the water environment, mercury pollution presents in mine cave water samples, and cadmium, mercury, and lead pollution present in scenic park water samples. The results of single-factor pollution index showed that mercury in mine cave water samples and cadmium, mercury, and lead in scenic park water samples were graded as severe pollution. The results of Nemero pollution index showed the highest comprehensive pollution level of heavy metals was in scenic park water samples. In atmospheric dust fall, cadmium, mercury, lead are the most prominent pollution. Potential risks to ecological environment were identified for cadmium and mercury in all study areas and lead in other areas outside Wanshan. The results of integrated potential ecological risk index indicated a high-risk level of heavy metal pollution in atmospheric dust fall in the current study area. At present, the heavy metal pollutants in the environment of Guizhou are mainly originated from natural factors such as geological background content and soil-forming parent material, and human activities such as mining, metal smelting, agricultural activities, and sewage irrigation. The analysis showed serious heavy metal pollution in the environment of Guizhou, which caused harm to the local environment. It is crucial that environmental protection measures be taken during human activities.
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Industrial waste is released into the environment and leads to various types of heavy metal, which are toxic, mutagenic and carcinogenic in nature. Heavy metals are not biodegradable but accumulated by living organisms and cause diseases at even low concentrations. In this study, we selected four anthropogenic sites from Chambal region, isolated bacteria and investigated its heavy metal removal capability. The bacteria was isolated and identified as Escherichia coli (Ag-5), on the basis of biochemical and 16S rRNA gene sequence. Among the five (cadmium, cobalt, lead, nickel and zinc) heavy metals studied, Ni2+ has been observed to be highly toxic with minimum inhibitory concentration score of 200 ppm. E. coli could tolerate Zn2+ (300 ppm), Cd2+ (400 ppm), Co2+ (400 ppm) and Pb+2 (500 ppm). Heavy metal tolerance capability was also evaluated by UV rays treated E. coli (Ag-5) isolate and compared with wild strain Ag-5. The result indicated that the tolerance capability was enhanced by UV rays treated bacterial isolate as compared to wild strain with respect to all tested heavy metals. Atomic absorption spectroscopy results revealed that wild strain removed 78.2% cadmium nitrate, while UV rays 30 and 60 s. exposed strain removed 85.9 and 83% cadmium nitrate. Wild strain removed 64.4% nickel chloride, while UV rays 30 and 60 s exposed strain removed 66.9 and 74.5% nickel chloride. The results indicate that indigenous E. coli treated with UV rays could serve as heavy metal tolerant bacteria and utilized in bioremediation processes.
ABSTRACT
Heavy metals such as zinc in untreated industrial effluents cause diseases and disorders in living organisms. They cannot be degraded like organic contaminants and hence have to be removed. Though physical and chemical methods are available for their removal, most of them are not economical and eco-friendly. Hence, a suitable technique is necessary to minimize the deleterious effects of dispersion of heavy metals in ecosystems. Though zinc serves as a micronutrient, it becomes toxic in higher concentrations. Bacteria can be used in the removal of zinc and the process is economical and ecofriendly. Hence, in the present study, we tested zinc removal efficiency of Bacillus subtilis (MTCC 2423) for various concentrations viz. 100, 200, 300, 400 and 500 ppm of zinc in nutrient broth for a period of 10 days. Samples were tested for the zinc level every two days in each concentration and the maximum removal was noticed after six days of treatment. With the increase in zinc concentration, both biomass and zinc removal efficiency showed an increase. Autoclaved cells showed maximum zinc removal when compared with other cell types. Among the other heavy metals tested, iron enhanced the biomass of B. subtilis during zinc treatment and the results are discussed.
ABSTRACT
Intense industrial activity in the twentieth century, particularly in developing nations, has resulted in significant environmental pollution, resulting in a vast number and variety of polluted sites that pose a threat to the surrounding ecology. Metal pollution has become one of the most serious environmental problems today as a result of human activities such as metal mining and smelting, electroplating, gas exhaust, energy and fuel production, fertilizer, sewage and pesticide application, municipal waste generation, and so on (Kabata-Pendias and Pendias, 2000). Most plants are affected by an excessive buildup of heavy metals. Heavy metal ions are disproportionately absorbed by roots and translocate to shoots when present at high levels in the environment, resulting in decreased metabolism and growth. In recent years, phytoremediation has gained a lot of market acceptance. Phytoremediation technology appears to be a potential cleanup solution for a wide range of metal-contaminated locations, albeit it does have limitations, according to preliminary study. The rhizosphere is a biologically active zone of the soil around plant roots that contains soil-borne microorganisms including bacteria and fungi. Plant–microbe interactions in the rhizosphere can be advantageous to the plant, the microbes or to neither of them.
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RESUMO A representatividade da amostragem é fundamental para embasar a tomada de decisão, uma vez que a heterogeneidade da matriz é o principal fator para incerteza dos dados nos estudos de gerenciamento de áreas contaminadas. Neste estudo, coletaram-se 112 amostras de solo superficial em malha quadrada de 1 x 1 m, em uma área 15 x 6 m, no campus regional de Resende da Universidade do Estado do Rio de Janeiro. Anteriormente, no terreno funcionaram empresas de produção de filmes radiográficos e purificação de prata metálica. As amostras de solo foram analisadas por pXRF, método de screening para metais. Com base nos dados levantados, calculou-se, por meio de métodos estatísticos, a quantidade de amostras que permitiriam uma caracterização representativa da área, considerando um erro relativo de 20% para dois intervalos de confiança: 95 e 80%. As análises indicaram concentrações superiores aos valores de referência para os parâmetros prata, mercúrio, chumbo, selênio e zinco. Os resultados de mercúrio possivelmente referem-se a ruído espectral, não estando relacionados ao histórico de uso e ocupação. Os coeficientes de variação das concentrações dos elementos analisados variaram de 132 a 225%. Considerando uma distribuição lognormal, calcularam-se 76 amostras para o maior intervalo de confiança e 53 para o menor. Isso seria o equivalente a transectos com espaçamentos de 1,47 e 2,11 m. Os resultados ratificam a necessidade de investigações de alta resolução nas áreas fonte, conforme recomendado pela Decisão de Diretoria da Companhia Ambiental do Estado de São Paulo nº 038/2017/C (DD-038).
ABSTRACT The representativeness of the sampling is fundamental to support decisions, since the heterogeneity of the matrix is the main factor for data uncertainty in contaminated areas management studies. In this study, 112 surface soil samples were collected in a square mesh of 1 x 1 m, in an area of 15 x 6 m, at the Campus Regional de Resende (CRR) of Universidade do Estado do Rio de Janeiro (UERJ). Previously, companies of radiographic films production and metallic silver purification operated in this area. The soil samples were analyzed by pXRF, a screening method for metals detection. Based on the data collected, the number of samples that would allow a representative characterization of the area was calculated, using statistical methods, considering a relative error of 20% for 80 and 95% confidence intervals. The analyses indicated concentrations higher than the reference values for the parameters silver, mercury, lead, selenium, and zinc. The results of mercury possibly refer to spectral noise, not being related to the history of use and occupancy. The coefficient of variation of the soil obtained ranged from 132 to 225%. Considering a lognormal distribution, 76 samples were calculated for the highest confidence interval and 53 for the lowest. This would be the equivalent of transects with spacings of approximately 1.47 and 2.11 m. The results confirm the need for high resolution investigations in the source areas, as recommended by the Executive Board Decision of CETESB No. 038/2017/C (DD-038).
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The remediation of heavy-metal (HM) contaminated soil using hyperaccumulators is one of the important solutions to address the inorganic contamination widely occurred worldwide. Hyperaccumulators are able to hyperaccumulate HMs, but their planting, growth, and extraction capacities are greatly affected by HM stress. The application of arbuscular mycorrhizal fungi (AMF) enhances the function of hyperaccumulators by combining the functional advantages of both, improving the efficiency of remediation, shortening the remediation cycle, and maintaining the stability and persistence of the remediation. Thus, the combined use of AMF with hyperaccumulators has broad prospects for application in the management of increasingly complex and severe HM pollution. This review starts by defining the concept of hyperaccumulators, followed by describing the typical hyperaccumulators that were firstly reported in China as well as those known to form symbioses with AMF. This review provides a systematic and in-depth discussion of the effects of AMF on the growth of hyperaccumulators, as well as the absorption and accumulation of HMs, the effects and mechanism on the hyperaccumulator plus AMF symbiosis to absorb and accumulate HMs. AMF enhances the function of hyperaccumulators on the absorption and accumulation of HMs by regulating the physicochemical and biological conditions in the plant rhizosphere, the situation of elements homeostasis, the physiological metabolism and gene expression. Moreover, the symbiotic systems established by hyperaccumulators plus AMF have the potential to combine their abilities to remediate HMs-contaminated habitat. Finally, challenges for the combined use of remediation technologies for hyperaccumulator plus AMF symbiosis and future directions were prospected.
Subject(s)
Biodegradation, Environmental , Metals, Heavy , Mycorrhizae/chemistry , Plant Roots/chemistry , Soil Pollutants , SymbiosisABSTRACT
BACKGROUND@#Arsenic and heavy metals are the main cause of water pollution and impact human health worldwide. Therefore, this study aims to assess the probable health risk (non-carcinogenic and carcinogenic risk) for adults and children that are exposed to arsenic and toxic heavy metals (Pb, Ni, Cr, and Hg) through ingestion and dermal contact with drinking water.@*METHOD@#In this study, chemical analysis and testing were conducted on 140 water samples taken from treated drinking water in Mashhad, Iran. The health risk assessments were evaluated using hazard quotient (HQ), hazard index (HI), and lifetime cancer risk (CR).@*RESULTS@#The results of the HQ values of arsenic and heavy metals for combined pathways were below the safety level (HQ < 1) for adults, while the HI for children were higher than the safety limit in some stations. Likewise, Cr showed the highest average contribution of HI (55 to 71.2%) for adult and children population. The average values of total carcinogenic risk (TCR) through exposure to drinking water for children and adults were 1.33 × 10 and 7.38 × 10, respectively.@*CONCLUSION@#Overall, the CR through exposure to drinking water for children and adults was borderline or higher than the safety level of US EPA risk, suggesting the probability of carcinogenic risk for the children and adults to the carcinogenic elements via ingestion and dermal routes. Therefore, appropriate purification improvement programs and control measures should be implemented to protect the health of the residents in this metropolitan city.
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In recent years, plant extracts have been widely developed and used, but the pollution of heavy metals has threatened the safe application of plant extracts. Therefore, effective removal of heavy metal pollution in plant extracts has become an urgent problem to be solved and a research hotspot at home and abroad. At present, the widely used heavy metals removal technologies include flocculent precipitation, adsorption, molecular sieve and so on. Other new technologies and materials are also being applied to the removal of heavy metals from plant extracts, such as microbiological methods, nanotechnology, ion/molecular imprinting techniques, biomimetic materials, etc. This paper reviews the related literature about the principle and application of removal of heavy metals in plant extracts in recent years, summarizes the characteristics of each method, and prospects the development trends and prospects for the future.
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With the extent of contamination in water and soil today, possibility of presence of toxic heavy metals in plants in everyday life can not be ruled out. In this context, understanding the influence of exogenenous factors on such plants gains importance. Here, we investigated expression of metallothioneins genes MT1 and MT2 in Rapeseed Brassica napus L. as representatives of MT gene type 1, type 2 (BnMT1 and BnMT2), respectively to explore such influence, if there any. Seedlings of 7-day-old were exposed to various exogenous factors including plant hormones, heavy metals, abiotic and biotic stresses. The basal expression levels of two BnMT genes were determined using water-treated samples (control). Each treatment was replicated 3 times for statistical validity. SPSS computer software was used for statistical analyses. Expression profiles of BnMT1 and BnMT2 were generated by semi-quantitative RT-PCR (sqRT-PCR) to monitor stress-response gene expression of both genes. The BnMT1 and BnMT2 genes were expressed at the same level in control samples. In general, BnMT1 gene was better expressed in most treatments compared to BnMT2 throughout the 48 h experimental period. Moreover, BnMT2 expression was not affected by heavy metal stress. The results provide considerable insights into the molecular mechanism of MTs responses to environmental stress in B. napus which can be utilized for future plant manipulations to improve its ability to accumulate higher metal concentration from the soil.
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Recent years, with the rapid development of industrialization in China, the contamination of heavy metal was worsening, and traditional Chinese medicinal materials (TCMM) were also suffered. The data were collected in the literatures in the past five years, and Green Trade Standard of Importing & Exporting Medicinal Plants & Preparations was used as the standard to evaluate the pollution conditions of lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), and copper (Cu). The five heavy metals exceeded the limits of the standard and the percentages were 9.66%, 26.35%, 13.0%, 9.32%, and 16.09%, respectively. Moreover, statistics on the residues of the heavy metals in different categories of TCMM from various origins were also carried out in this paper. The results showed that the contamination of heavy metals in TCMM differently depended on the origins and categories. Studies on the rapid detection methods and the limit standards of heavy metal should be established immediately. At the same time, the regulations should be formulated timely and supervision also should be intensified. To solve the problems of excessive amounts of heavy metals in TCMM, necessary measures should be taken to control the contamination of TCMM.
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A biomonitoring study was conducted to assess the levels of atmospheric heavy metal pollution in Katni and Rewa cities of Madhya Pradesh, state in central India. The Pyxine cocoes and Phaeophyscia hispidula, two epiphytic foliose lichen were used as bioindicators in the present study and seven metals (As, Al, Cd, Cr, Fe, Zn, Pb) were analyzed in naturally growing thallus. The concentrations of these metals was observed to be in higher range as maximum values of Al, Cd, Cr and Zn were reported from the lichen samples from Rewa city which was 561.8±2.4, 6.8±0.8, 35.2±1.4, 214.6±2.0 @g g-1 dry weight respectively. Whereas As, Fe and Pb were reported maximum in the lichen samples collected from Katni city areas with 33.4±0.05, 689.4±2.6, 13.3±0.5 @g g-1 dry weight respectively. However the accumulation of Cd and Pb from both the cities are more or less similar in concentration. The selectivity sequence of metals were Fe>Al>Zn>As>Cr>Pb>Cd in Katni city, and Al>Fe>Zn>Cr>As>Pb>Cd in Rewa city. The findings of this study indicates that extent of heavy metal pollution in the atmosphere of the two cities which may lead to adverse health affects.
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Mercury toxicity in tilapia, Oreochromis niloticus, (Linnaeus, 1758) was investigated by the hematological parameters after long-term (14 days) exposure to various Hg concentrations (0.02, 0.002, 0.0002mg/L Hg). Test groups were set up with three replicates for each concentration, plus the control group. Blood samples were collected from six individuals for each concentration at 0, 3, 7, 10 and 14 days of exposure. The hematological parameters analyzed were: total red blood cell count (RBC), hemoglobin concentration (Hb), hematocrit (Ht), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), total white blood cell count (WBC) and differential leukocyte counts and total thrombocyte count (Tr). There were no significant differences among the mean hematological values at the different Hg concentrations indicating that Hg at the concentrations studied was not toxic to tilapia.
A toxicidade do mercúrio foi avaliada em tilápia, Oreochromis niloticus (Linnaues, 1758) através da análise dos parâmetros hematológicos após exposição a diferentes concentrações sub-letais, durante um período de 14 dias. O bioensaio foi conduzido no laboratório de toxicologia do Instituto de Pesca, SP. Foram utilizados alevinos (12.44 ± 0.84 cm, e 27.13 ± 4.67 g) e aquários com capacidade para 50 litros e preenchidos com água declorada e mais a quantidade de solução de mercúrio (HgCl2) correspondendo as seguintes concentrações: 0,02; 0,002; 0.0002 mg.L-1 Hg. Foram utilizadas 3 repetições de cada concentração e grupo controle. Amostras de sangue foram coletadas de seis animais de cada concentração nos tempos 0, 3, 7, 10 e 14 dias de exposição. Foram avaliados: a contagem de eritrócitos (RBC), concentração de hemoglobina (Hb), hematócrito (Ht), volume corpuscular médio (VCM), hemoglobina corpuscular média (HCM) e concentração de hemoglobina corpuscular média (CHCM), trombócitos totais (Tr), contagem diferencial e total de leucócitos (Lc). Os resultados demonstram que as concentrações de Hg testadas, não alteraram significativamente os parâmetros hematológicos, permitindo concluir que a quantidade de Hg na água não foram suficientes para afetar o quadro hematológico de Oreochromis niloticus.