Buildup Of Heavy Metals Research Articles

RHIZOSPHERE MICROBES AS BIOSORBENTS FOR HEAVY METAL REMOVAL

Intense industrial activity in the twentieth century, particularly in developing nations, has resulted in signicant 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

Mitigation of lead and Cadmium from vegetable crops through different biochemical adsorbent treatments at Sanganer industrial area, Jaipur

The most difficult challenge in the world is widespread access to good and healthful food. For the human diet, vegetables are considered as a crucial element and are regarded as natural nutritional reserves. Heavy metals are threatening dietary contaminants, and their consumption causes a variety of health problems. In urban and peri-urban regions people utilize wastewater, particularly sewage effluent, to irrigate agricultural fields because of the scarcity of fresh water. Nevertheless, there is growing worry about the possible health concerns linked with consuming tainted veggies. This scenario is especially concerning in vegetables cultivated in industrial locations, which have a high prevalence of heavy metal build-up. As a result, a research project was launched to determine the long duration impact of polluted water irrigation on concentrations of heavy metals (HMs) in soil and vegetable crops. In soil, vegetable and water samples, a high concentration of Lead and Cadmium was found. In this study, heavy metals were reduced in spinach and kale obtained from peri-urban locations by treating them with various biochemical adsorbent solutions. Using an Atomic Absorption Spectrophotometer (AAS), the amount of heavy metals in soil, vegetable and water samples was evaluated. To find the most effective adsorption therapy for HM'smitigation, the data was statistically analysed. Treatment with several biochemical adsorbent solutions resulted in a considerable decrease in heavy metal concentration. Among various chemical adsorbents, 15% sodium carbonate proved maximum reduction potential and among various biological adsorbents, 15 % orange peel extract proved maximum reduction potential for HMseradication off vegetable sampling.

HEAVY METALS IN THE FOOD CHAIN - CONSEQUENCES OF POLLUTING WATER BODIES

Purpose of the study: Heavy metals in food (vegetables, etc.) are harmful to humans due to their non-biodegradable nature, long biological half-lives, and their potential to accumulate in different body parts. Prolonged consumption of such heavy metal contaminated vegetables through foodstuffs may lead to chronic accumulation of heavy metals in human beings' kidneys and liver, disrupting numerous biochemical processes, leading to cardiovascular, neural, kidney and bone diseases. Method: The study on heavy metal concentrations in vegetables grown in the command areas of Varthur lake, Bangalore. The collected vegetable samples were analyzed using ICP-OES (Inductively Coupled Plasma-Optical Emission Spectroscopy) technique to assess the level of heavy metal in acid digested samples. Main Findings: The study has shown a significant accumulation of heavy metals in vegetables that correlated well with its concentrations in soil and lake water. The prolonged irrigation of vegetables using contaminated lake water has led to soil contamination, which ultimately resulted in contamination of vegetables due to the uptake and accumulation of heavy metals in edible portions of vegetables. Application of the Study: Urgent attention is needed to devise and implement appropriate means of regular monitoring of the toxic heavy metals from domestic sewage and industrial effluent and provide proper advice and support for the safe and productive use of wastewater for irrigation purposes to prevent excessive buildup of heavy metals in the food chain.

Accumulation and bioconcentration of heavy metals in two phases from agricultural soil to plants in Usangu agroecosystem-Tanzania

The build-up of heavy metals (HM) in agricultural soils accelerates the HM uptake by plants, which could potentially affect food quality and food safety. Here we studied the status and bioaccumulation of HM from soils to plant parts (roots, stem, and grains) in Usangu agro-ecosystem-Tanzania. In total 68 soil samples and 42 rice plant samples from six irrigation schemes were studied. The concentrations of cadmium-Cd, chromium-Cr, copper-Cu, lead-Pb, zinc-Zn, nickel-Ni, and iron-Fe were determined to estimate accumulation, distribution, bioconcentration. Total soil HM concentration in soil and plant samples was determined by acid digestion. The concentration of HM in soils samples (in mg/kg) were Cr (4.58–42.76), Co (1.486–6.12), Fe (3513.56–12593.99), Zn (7.89–29.17), Cd (0.008–0.073), Cu (0.84–9.25), Ni (0.92–7.98), and Pb (1.82–18.86). The total HM concentration in plant samples were (in mg/kg) were Cu (5.18–33.56), Zn (57.03–120.88), Fe (963.51–27918.95), Mn (613.15–2280.98), Cd (4.3–17.46), Pb (0.01–28.25), Cr (12.88–57.34) and Ni (9.65–103.33). The concentration of HM in soil and plant parts was observed to vary among locations where high concentrations of HM were detected in stems and roots compared to grains. The ratio HM in plants and soil samples (bioconcentration) was higher than one for some sites indicating higher HM uptakes by plants leading to possible health risk to soil invertebrates, animals, and humans. The bioconcentration factor varied among schemes, with the highest values at Igalako and Mahongole, which could be caused by artisanal gold mining and mining quarry existed in the area. Therefore, steps are needed to reverse the situation to balance the HM in agricultural soils and plant tissues to be within acceptable limits.

Modulation of photosynthesis, nitrogen fixing ability, and yield attributes of Chickpea (Cicer arietinum L.) to interactive effect NPK fertilizers and municipal wastewater irrigation

In recent years, the urban wastewater of marginal quality is increasingly being used to irrigate lands for growing crops. However, water reuse in agriculture needs specific studies to evaluate its safe use depending upon the choice of the crop and soil type. A pot experiment was therefore, conducted to investigate the effect of different fertilizer combinations, that is, nitrogen, phosphorus and potassium (NPK) on chickpea (Cicer arietinum L.) irrigated with sewage wastewater (WW), and ground water (GW). The objective of this experiment was to evaluate optimal fertilizer requirement based on growth, physiological determinants, and the yield of chickpea under wastewater irrigation. Results revealed the positive influence of wastewater and optimal growth and yield of the crop were obtained with a relatively lower fertilizer combination of N30P60K40 when irrigated with wastewater. Physiological parameters of plants being irrigated with wastewater were also enhanced when compared to ground water irrigated plants and it was expressed by significant improvement in the yield parameters of the crop. The nutrients present in wastewater therefore proved beneficial for the crop yield and also reduced the nutritional requirement of the crop to be supplied in the form of fertilizers. It can therefore serve not only as an alternative disposal of wastewater but even supplement the nutritional requirement of the crop. However, its long-term usage needs to be closely monitored for any heavy metal buildup in soil as their presence in wastewater could be a cause of concern.

Impact of heavy metals on physiological health of lichens growing in differently polluted areas of central Assam, North East India

Accumulation of heavy metals on naturally grown epiphytic lichens and its impact on their physiological integrity was examined. Lichen species collected from differently polluted areas (oil refinery, roadside) were compared with the species collected from relatively lesser polluted areas. Heavy metal buildup in lichens were found to have significant damaging effect on their physiological health. Pb, Cd, Zn, Cu, Co, Ni and Cr concentrations were found to be higher in the lichen species collected from both the polluted areas. Metal accumulation in lichen thallus has positive correlation at p ≤ 0.01 (r = 0.417 to 0.772) with the recorded protein concentrations. Whereas, other studied parameters like chlorophyll and carotenoid concentrations, membrane stability and pH documented negative correlation with the accumulated heavy metals. However, abundance of species Dirinaria applanata and Dirinaria sp. at polluted areas with better protein content indicates their tolerance towards heavy metal. Chlorophyll degradation and protein contents in the lichens were found to be efficient physiological parameters to correlate with the air quality of a region. Sensitivity to heavy metals may be the cause of sparsity of species Arthonia cinnabarina, Cryptothecia subnidulans and Lecanora sp. in the polluted areas. However, lesser sensitivity to heavy metals favored the growth of species Dirinaria applanata and Dirinaria sp. even in higher polluted areas.

Polluted Waters Use in the Urban Agriculture and Its Impact on the Quality of the Grown Vegetables

Urban agriculture has become a common practice in major urban agglomerations, particularly in the mining region of Katanga, in the Democratic Republic of Congo (DRC). However, this agriculture is based on the production of vegetables grown on the soil contaminated by industrial water and domestic wastewater, wherein one finds heavy metals and pathogenic microbes capable of endangering the consumer’s health. This work has been carried out in view of contributing to the consumer’s health protection and endeavours at establishing, based on physicochemical and mineral analyses of water samples, the soil used in the urban agriculture and edible plants, a link between the use of contaminated waters in the urban agriculture, the build-up of heavy metals in the soil and the possible contamination by heavy metals of vegetables grown (amaranths and broccolis) in the Kasungami district and consumed by the population living in the City of Lubumbashi (DRC). The results given by the analyses of water, soils and vegetable samples revealed that, apart from cobalt, other heavy metals were present in water used in the urban agriculture to concentrations below quality standards. As for the soil, it contained heavy metals to concentration reputed phytotoxic. However, only the broccolis were contaminated with lead, contrarily to amaranths in which heavy metals were present to concentrations below quality standards. These findings enabled concluding that urban agriculture of vegetables encountered in the large agglomerations of the DRC could endanger the consumers’ health and measures need to be taken in view of preventing heavy metal from entering the food chain.

Assessment of the health risks of heavy metals in soils and vegetables from greenhouse production systems in Iran

Overuse of chemical and organic fertilizers in greenhouse (GH) crop production may cause the accumulation of heavy metals in soils and risks to human health. The aims of this study were to compare physical and chemical properties of GH with open-field (OF) soils, to clarify the buildup of heavy metals and phosphorus (P) in soils, and to assess the risks of selected heavy metals in soils and cucumber (Cucumis sativus L.) and tomato (Lycopersicon esculentum Mill.) from GH vegetables in Hamedan, western Iran. The average total and Olsen P of GH soils were significantly higher than the OF soils for both vegetables. The order of total and available heavy metal content in tomato GH soils has been set as zinc (Zn) > nickel (Ni) > chromium (Cr) > lead (Pb) > copper (Cu) > cadmium (Cd) and Zn > Cr > Cu > Pb > Ni > Cd, respectively. The same order was found for cucumber GH soils, except that the position of Pb and Cu was changed. The results indicated that in both GH cucumber and tomato soils, the mean content of total and available Zn, available Cu, Ni, and Pb, was extra than in OF soils. There were no significant differences between average total Cr, Cu, Ni, and Pb in GH and OF soils. Tomato vegetables had higher heavy metal content and transfer factors, particularly for Cr than cucumber vegetables. According to the health risk indices, Cr and Pb represented a high potential risk for health through cucumber and tomato consumption. There were limited Cd, Cu, Pb, and Zn inputs from the irrigation waters, while the input of Cr and Ni may be important. However, the amount of manure application and heavy metal content of the manures was significant.

Quantification and risk assessment of heavy metal build-up in soil-plant system after irrigation with untreated city wastewater in Vehari, Pakistan.

In peri-urban areas of district Vehari, farmers are using untreated city wastewater for crop irrigation owing to the scarcity of good-quality irrigation water. This practice may pose severe environmental and health issues to local inhabitants attributed to the high levels of potentially toxic metals in wastewater. The present study evaluated the potential impacts of wastewater irrigation on metals (Cd, Cr, Cu, Fe, Ni, Mn, Pb and Zn) build-up in the soil-plant continuum and associated health risks. In this study, wastewater (n = 17), soil (n = 108) and plant (n = 65) samples were collected from 15 peri-urban sites of three tehsils of district Vehari. Results showed that the mean concentration (mg/L) of Cd (0.02), Mn (0.25) and Fe (1.57) in wastewater samples was higher than their respective threshold values. Similarly, Cd, Mn and Fe concentration in soil was beyond the permissible limits of agricultural soil receiving wastewater irrigation. However, plants showed high accumulation of Pb, Cr and Fe than their respective limits depending on the vegetable/crop species. The health risk parameters showed that Pb and Cd are the major toxic chemical substances to human health, and the daily intake of crop plants can pose a potential health threat due to wastewater-irrigated crop consumption. Results highlighted the necessity of wastewater pretreatment to avoid the soil and vegetable contamination by wastewater irrigation and to reduce the associated health risks.

FACTORS INFLUENCING HEAVY METAL REMOVAL BY MICROALGAE-A REVIEW

The build-up of heavy metals in soils and waters continues to create serious global health concerns, as these metals cannot be degraded into nontoxic forms, but persist in the ecosystem. It is essential to remove or reduce heavy metal contamination in order to prevent or reduce contaminating the environment. Bioremediation utilizes inherent biological mechanisms to eliminate hazardous contaminants using microorganisms and plants. Algae have been applied to heavy metal removal because of their high sorption capacity. This review addresses the different factors influencing heavy metal removal by algae and its corresponding application in bioremediation. Based on the earlier reports, microalgae have the potential to become an effective and economical bio sorbent for the bioremediation of heavy metal. Further, the development of technology for simultaneous detection and removal of toxic metals using microalgae will assist in bioremediation of toxic metal from contaminated sites and from industrial effluents.

Influence of urbanisation characteristics on the variability of particle-bound heavy metals build-up: A comparative study between China and Australia

Heavy metal pollution of urban stormwater poses potential risks to human and ecosystem health. The design of reliable pollution mitigation strategies requires reliable stormwater modelling approaches. Current modelling practices do not consider the influence of urbanisation characteristics on stormwater quality. This could undermine the accuracy of stormwater quality modelling results. This research study used a database consisting of over 1000 datasets to compare the characteristics of heavy metal build-up (one of the most important stormwater pollutant processes) on urban surfaces under the influence of anthropogenic and natural factors specific to different urban regions from China (Shenzhen) and Australia (Gold Coast), using Bayesian Networks. The outcomes show that the differences in heavy metals build-up loads between the two regions (mean value for Shenzhen – mean value for Gold Coast)/mean value for Shenzhen) were 0.45 (Al), 0.88 (Cr), 0.99 (Mn), 0.68 (Fe), 0.98 (Ni), 0.24 (Cu), 0.47 (Zn) and 0.13 (Pb), respectively. The research outcomes also confirmed that the influence of traffic on the build-up of different sized particles varies between Shenzhen and Gold Coast, and traffic plays distinct roles as a source and as a factor that drives heavy metal re-distribution. The road surface roughness was also found to influence build-up process differently between the two regions. More importantly, the assessment of inherent process uncertainty revealed that heavy metal build-up between different road sites in Shenzhen varies over a wider range than in Gold Coast. The study highlighted a clear distinction in the influence of sources and key anthropogenic factors on the variability of particle-bound heavy metals build-up between geographically different urban regions. The study outcomes provide new knowledge to enhance the accuracy of urban stormwater quality modelling.

Mapping potential risks of long-term wastewater irrigation in alluvial soils, Egypt

In Egypt, wastewater has been used for irrigation in areas with fresh water scarcity; however, continuous applications may cause potential risks. Thus, the current study aims to map the spatial distribution of soil contamination and human risks of long-term wastewater irrigation due to the exposure of heavy metals. Soils from nine sites in Al-Qalyubia Governorate, Egypt, were sampled and analyzed. Wastewater irrigation resulted in a buildup of heavy metals in soils compared to Nile fresh water-irrigated soil. The pollution index (PI) showed the decreasing order of Cd > Zn > Ni > Cu > Co > Pb > Cr. The soils were out of the safe domain, as the integrated pollution index of Nemero’s (IPIN) exceeded the safe limit of 0.7. The enrichment factor (EF) exceeded 1.0, proving anthropogenic effects. The geo-accumulation index (Igeo) indicated high threats associated with Cd. The calculated hazard index (HI) indicated that humans exposed to such contaminated soils would have a potential health risk, particularly children. It is recommended to perform a treatment to the wastewater used in irrigation to avoid such threats.

Health Risk Assessment of Heavy Metals via Dietary Intake of Vegetables Grown in Wastewater Irrigated Areas of Jagjeetpur, Haridwar India

The present study was conducted to appraise the human health risk due to dietary intake of heavy metals contaminated vegetables viz., cabbage (Brassica oleracea var. capitata), cauliflower (Brassica oleracea var. botrytis) and spinach, (Spinacia oleracea) grown in the municipal wastewater irrigated soil in the proximity of sewage treatment plant (STP), Jagjeetpur, Haridwar. The results showed that Cd, Fe and Mn concentrations in B. oleracea var. capitata, B. oleracea var. botrytis and S. oleracea were found beyond the safe limit of the Indian and WHO/FAO standards for heavy metals in the vegetables. The contamination factor of these heavy metals in the soil was recorded in the order of Fe > Mn > Zn > Cu > Cr > Cd after irrigation of municipal wastewater. The higher values of metal pollution index in different vegetables as B. oleracea var. capitata (14.82; B. oleracea var. botrytis (10.48) and S. oleracea (12.59) showed more health risk index for Cd, Fe and Mn in these vegetables cultivated in the wastewater irrigated soil. Therefore, dietary intake of these heavy metals contaminated vegetables may pose a significant threat to the human health. However, cauliflower contained less heavy metal as compared to the cabbage and spinach, but health risk was more due to higher role in the diet. Even though there were low concentrations of heavy metals in the municipal wastewater used for the irrigation, but long term use of the municipal wastewater may cause gradual buildup of heavy metals in the vegetables grown in the municipal wastewater irrigated soil and leads to health risk of consumers due to intake of heavy metals contaminated vegetables.

Impact of Long-Term Application of Patranala Sewage on Carbon Sequestration and Heavy Metal Accumulation in Soils

There is a gradual decline in good quality irrigation water for crop production. Farmers are forced to use poor quality water for crop production in peri-urban areas. Among the wastewater, sewage water generally contains higher amount of plant nutrients and dissolved organic matter. A case study was conducted to investigate the impact of untreated sewage water application on physicochemical properties and carbon sequestration in soil. For this purpose, peri-urban agricultural lands irrigated with sewage water from Patranala, Bhopal were selected. Such lands around both sides of the Patranala were being irrigated with sewage water for more than last 50 years. The soil samples were collected at various soil depths i.e., 0–15, 15–30, 30–45 and 45–60 cm from these fields; and sampling points were at about 2 km intervals along the channel direction and also at the distance interval of about 0.5, 1.0, 1.5 and 2.0 km away from the sewage carrying channel. The soil microbial population and enzymatic activities were considerably higher in the sewage irrigated fields as compared to those in tubewell irrigated area. Concentrations of heavy metals in surface soils were also higher in sewage irrigated fields. Maximum soil organic carbon (SOC) contents were found in surface layer (0–15 cm), which decreased with depth at all the locations. Net stock of carbon in upper 60 cm of the soil depth was higher in sewage irrigated lands as compared to those irrigated with tubewell water. Thus, long-term application of sewage water for crop production enhanced sequestration of sewage borne carbon in soil profile, which otherwise could pollute the surface water bodies and emit in the atmosphere as greenhouse gases. However, heavy metals build-up in the sewage irrigated area is a major concern.

Heavy Metal Contamination in Agricultural Soil at DEPZA, Bangladesh

Higher accumulation of toxic heavy metals in rice grown in agricultural soil may lead to health disorder. The present study was carried out to assess the levels of different heavy metals like potassium, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc in agricultural soil. The soil samples were collected by soil auger from the arable fields of Nolam near Dhaka Export Processing Zone Area (DEPZA), Savar, Dhaka of Bangladesh. The samples were irradiated using 3MV Van de Graaff Accelerator at the Atomic Energy Centre, Dhaka and Proton Induced X-ray Emission (PIXE) technique was employed for the analysis. The results indicated a substantial build-up of heavy metals in surface soil andsub-surface soil. Average metal concentrations were calculated and compared with reference values. The persistence of heavy metals in surface soil was higher than the sub-surface soil and it exceeded the standard safe limit. Uptake and translocation factor of heavy metal from surface soil to sub-surface soil were quite distinguished for almost all elements examined. In terms of health risk, the observed highest concentrations of these elements in soil could have an effect on human health which may pose public health hazards and for this pretreatment process of waste water is necessary for reducing the amount of heavy metals before using it to the agricultural soil. Wastewater from industries or other sources carries an appreciable amount of toxic heavy metals therefore their discharge into the environment must be minimized and carefully controlled.

Long-term irrigation with zinc smelter effluent affects important soil properties and heavy metal content in food crops and soil in Rajasthan, India

ABSTRACTUse of wastewater for irrigating agricultural crops is on the rise, particularly in the developing countries. The present study was undertaken to assess the long-term effect of irrigation with zinc smelter effluent on important soil properties including heavy metal status. Metal concentration in the edible parts of the crops grown on smelter effluent-irrigated soils was also measured. For this purpose, the agricultural lands which have been receiving the zinc smelter effluent irrigation for about five decades at Debari, Udaipur, India were selected. The adjacent tubewell water-irrigated fields were selected as reference. Long-term irrigation with smelter effluent resulted into significant buildup of ethylenediaminetetraacetic acid extractable Zn (57.7 fold), Cu (4.51 fold), Fe (3.35 fold), Mn (1.77 fold), Ni (1.20 fold), Pb (45.1 fold), and Cd (79.2 fold) in soils over tubewell water-irrigated fields. Total Zn, Cu, Mn, Ni, Pb, and Cd content in effluent-irrigated soils was also increased by 27.0, 1.60, 1.40, 1.30, 26.2, and 167 fold, respectively. Risk assessment indicated a very high to moderate potential ecological risk due to Cd, Pb, and Zn in soils close to the immediate vicinity of the smelter plant. Cadmium and Pb concentrations in edible parts of almost all the crops grown on effluent-irrigated soils were above the safe limit of CODEX commission. On an average, soil pH dropped by 0.31 units due to smelter effluent irrigation. Smelter effluent irrigation resulted into significant increase in soil organic carbon, electrical conductivity, and CaCO3 content. On an average, there was decrease in available N (21.0%) and P (20.8%) content in effluent-irrigated soils over the tubewell water-irrigated ones. An increase in available K (102%) and S (26.0 fold) was recorded in effluent-irrigated soils. Long-term irrigation with zinc smelter effluent resulted into reduced microbial activities in soil as evidenced from the level of microbial biomass carbon and dehydrogenase activity. In view of the buildup of heavy metals and subsequent imbalance in essential plant nutrients in smelter effluent-irrigated soils, appropriate remediation-cum-fertilization strategy needs to be adopted for better soil health and plant nutrition.

Signs for secondary buildup of heavy metals in soils at the periphery of Athens International Airport, Greece.

Emissions from civil airports are similar to those observed in industrial and urban areas. While air pollution and noise levels are regularly monitored and assessed, information on the status of heavy metals in soils close to airport facilities is limited. In this study, we monitored and assessed heavy metal distribution in soils close to Athens International Airport (AIA) in Attica, Greece. Following a grid sampling scenario, topsoil samples were collected from 86 sites at the periphery of AIA and total and available forms of Cu, Zn, Fe, Mn, Ni, Cr, Pb, and Ba concentrations were determined in aqua regia and DTPA soil extracts, respectively. Median concentration values for both metal forms are not considered as particularly high. However, 90th percentile concentration values for some metals are high, indicating soil enrichment. Evaluation of enrichment factor (EF) and availability ratio (AR) values and EFs spatial distribution have led to consistent conclusions of secondary and ongoing metal accumulation in the soils of the studied area. Tessier sequential extraction procedure was applied to 10% of the soil samples and the results showed high potential availability of Pb, Mn, Cu, and Ni, further supporting the continuous metal accumulation in the studied soils.

Modelling heavy metals build-up on urban road surfaces for effective stormwater reuse strategy implementation

Urban road stormwater is an alternative water resource to mitigate water shortage issues in the worldwide. Heavy metals deposited (build-up) on urban road surface can enter road stormwater runoff, undermining stormwater reuse safety. As heavy metal build-up loads perform high variabilities in terms of spatial distribution and is strongly influenced by surrounding land uses, it is essential to develop an approach to identify hot-spots where stormwater runoff could include high heavy metal concentrations and hence cannot be reused if it is not properly treated. This study developed a robust modelling approach to estimating heavy metal build-up loads on urban roads using land use fractions (representing percentages of land uses within a given area) by an artificial neural network (ANN) model technique. Based on the modelling results, a series of heavy metal load spatial distribution maps and a comprehensive ecological risk map were generated. These maps provided a visualization platform to identify priority areas where the stormwater can be safely reused. Additionally, these maps can be utilized as an urban land use planning tool in the context of effective stormwater reuse strategy implementation.

Heavy metal accumulation and health risk assessment in wastewater-irrigated urban vegetable farming sites of Addis Ababa, Ethiopia

BackgroundWastewater irrigation for vegetable production is a highly prevalent practice in Addis Ababa and a number of articles have been published on wastewater-irrigated soils and vegetables contaminated with heavy metals. However, to the best of our knowledge, an insight into assessment of human health risks associated with the consumption of vegetable crops grown on wastewater-irrigated soils is non-existent in the city. Long-term effect of wastewater irrigation on the build-up of heavy metals in soils and selected vegetable crops in Addis Ababa urban vegetable farming sites (10) was evaluated. By calculating estimated daily intakes (EDIs) and target hazard quotients (THQs) of metals, health risk associated with the consumption of the analyzed vegetables was also evaluated.ResultsThe heavy metal concentrations in irrigation water and soils did not exceed the recommended maximum limits (RMLs). Moreover, Cd, Co, Cr, Cu, Ni and Zn concentrations in all analyzed vegetables were lower than the RML standards. In contrast, Pb concentrations were 1.4–3.9 times higher. Results of two way ANOVA test showed that variation in metals concentrations were significant (p < 0.001) across farming site, vegetable type and site x vegetable interaction. The EDI and THQ values showed that there would be no potential health risk to local inhabitants due to intake of individual metal if one or more of the analyzed vegetables are consumed. Furthermore, total target hazard quotients (TTHQs) for the combined metals due to all analyzed vegetables were lower than 1, suggesting no potential health risk even to highly exposed local inhabitants.ConclusionsThere is a great respite that toxic metals like Pb and Cd have not posed potential health risk even after long term (more than 50 years) use of this water for irrigation. However, intermittent monitoring of the metals from irrigation water, in soil and crops may be required to follow/prevent their build-up in the food chain.

Risk Assessment of Heavy Metals via Consumption of Contaminated Vegetables Collected from Different Agricultural Fields and Market Sites

The present study was conducted with an aim to compare heavy metals (Cu, Zn, Cd and Pb) accumulation potential of some of the commonly grown vegetables like brinjal, cauliflower, spinach and coriander collected from different agricultural (production) and market sites of Katihar city. The accumulation of Cd, Pb, Cu and Zn in test vegetables was higher in market sites then those at all agricultural lands and elevated by 47.84, 64.84, 21.3, and 9.91% in brinjal, 36.19, 78.09, 21.83, and 6.50% in cauliflower, 34.52, 49.50, 9.1, and 9.97% in spinach and 27.86, 47.05, 10.34, and 6.13% in coriander, respectively and was observed maximum in brinjal (143.89%) followed by cauliflower (142.61%), spinach (103.09%), and coriander (91.38%). The population load index (PLI), transfer factor (TF), daily intake of metals (DIM) and health risk index (HRI) were also studied. The maximum value of PLI was found for Zn (35.06%) and minimum for Pb (0.178%) in soil collected from production sites. The TF of heavy metals in vegetable collected from market sites was found to be higher than vegetable collected from production sites and could be one of the possible reasons for health risk in human via their consumption. The average daily intake of Cd, Pb, Cu and Zn, by adults in vegetables collected from market sites were 5.38, 1.20, 4.606 and 0.336% of provisional tolerable daily intake. The HRI value of all individual vegetables was below 1.0. Therefore, it is suggested that regular monitoring of heavy metals in vegetables is essential to prevent excessive build-up of heavy metals in the food chain and appropriate precautions should also be taken at the time of transportation and marketing of vegetables.