Urban Metal Pollution Research Articles

Source apportionment and emission projections of heavy metals from traffic sources in India: Insights from elemental and Pb isotopic compositions

The study investigates the sources of metals in urban road dusts using elemental concentration and Pb isotopic ratios. The elemental concentrations are also utilized to determine the present heavy metal emissions as well as projected emissions till 2045. Bayesian mixing model for source apportionment highlights the significant contributions of both exhaust and non-exhaust sources to the metal-enriched urban road dusts, with each contributing approximately 40 %. Emission analysis reveals that India’s projected electric vehicle (EV) penetration may not be sufficient to suppress the metal emissions from vehicular exhausts. Further challenge is posed by high metal concentrations in the non-exhaust sources, that dominates the emission of some metals compared to exhaust sources. If the metal concentrations remain unchanged, the emission analysis predicts alarming increases in total emissions from all the exhaust and non-exhaust sources by 174 %, 176 %, 163 % and 184 % for Ni, Cu, Zn and Pb, respectively, from 2022 to 2045. Thus, it is crucial to reduce the metal concentrations in traffic emission sources and also impose better regulatory measures to improve the urban metal pollution scenario.

Using native plants to evaluate urban metal pollution and appoint emission sources in the Brazilian Steel Valley region.

In southeastern Brazil, the city of Ipatinga is inserted in the Steel Valley Metropolitan Region, which hosts the largest industrial complex for flat-steel production in Latin America, while also having one of the largest vehicle fleets in the entire country. Since potentially toxic elements (PTEs) are not emitted solely by industries, yet also by vehicular activity, the predominant emission source can be determined by evaluating the ratio between different elements, which are called technogenic tracers. We performed a biomonitoring assay using two tropical legumes, Paubrasilia echinata and Libidibia ferrea var. leiostachya, aiming to assess chemical markers for the origin of emissions in the region, distinguishing between different anthropogenic sources. Plants were exposed for 90days in four urban sites and in a neighboring park which served as reference. After the experimental period, plants were evaluated for trace-metal accumulation. L. ferrea var. leiostachya retained lower amounts of metals associated with vehicular and industrial emission. The opposite was found with P. echinata, a species which should be recommended for biomonitoring of air pollution as a bioaccumulator. Plants of P. echinata were enriched with Fe, Al, Ni, Cr, and Ba, whereas plants of L. ferrea var. leiostachya were enriched with Fe, Cu, and Co. In both species, Fe was the element with which plants were enriched the most. Plants showed highest iron enrichment at Bom Retiro, the site downwind to the steel industry, which has shown to be the main particle emission source in the region.

Using community science for detailed pollution research: a case-study approach in Indianapolis, IN, USA.

Heavy metal contamination in urban environments, particularly lead (Pb) pollution, is a health hazard both to humans and ecological systems. Despite wide recognition of urban metal pollution in many cities, there is still relatively limited research regarding heavy metal distribution and transport at the household-scale between soils and indoor dusts-the most important scale for actual human interaction and exposure. Thus, using community-scientist-generated samples in Indianapolis, IN (USA), we applied bulk chemistry, Pb isotopes, and scanning electron microscopy (SEM) to illustrate how detailed analytical techniques can aid in interpretation of Pb pollution distribution at the household-scale. Our techniques provide definitive evidence for Pb paint sourcing in some homes, while others may be polluted with Pb from past industrial/vehicular sources. SEM revealed anthropogenic particles suggestive of Pb paint and the widespread occurrence of Fe-rich metal anthropogenic spherules across all homes, indicative of pollutant transport processes. The variability of Pb pollution at the household scale evident in just four homes is a testament to the heterogeneity and complexity of urban pollution. Future urban pollution research efforts would do well to utilize these more detailed analytical methods on community-sourced samples to gain better insight into where the Pb came from and how it currently exists in the environment. However, these methods should be applied after large-scale pollution screening techniques such as portable X-ray fluorescence (XRF), with more detailed analytical techniques focused on areas where bulk chemistry alone cannot pinpoint dominant pollution mechanisms and where community scientists can also give important metadata to support geochemical interpretations.

Soil, dust, and leaf-based novel multi-sample approach for urban heavy metal contamination appraisals in a megacity, Dhaka, Bangladesh

The fast-growing megacities in the South Asian region have been facing environmental issues such as heavy metal load due to anthropogenic activities including Dhaka city. Thus, this study was executed to understand the heavy metal contamination in the urban environment using a novel multi-sample (soil, dust, and tree leaves) approach in Dhaka city, Bangladesh. 13 sites were selected for the analysis of nine heavy metals using AAS. The concentration (ppm) of Cd (4.95 0.06), Zn (254.8 0), Cu (56.25 0.06), and Mn (995.9±0.0) in the soil and Cr (135.500 0.00), Ni (68.35 1.30), Zn (275.73 0.00), Cu (68.35 1.30) and Mn (1076.84 0.00) in the dust exceeded the maximum permissible limit. In tree leaf samples except for Ni all the heavy metals exceeded the standard value. Environmental pollution indices revealed that the study area is mostly contaminated with Cu, Pb, Ni, Zn, Cd, Mn, and Cr. Vehicle emissions were recognized as the major source of Zn, Cu, Pb, Ni in soil; Cr, Pb, Mn, Zn in the dust; and Ni, Mn, Pb, Zn in tree leaves, according to the multivariate statisticalanalysis. Industrial emissions were identified as the primary source of Cd in soil, Cu, Cd, Ni in dust, and Cr, Cd in tree leaves. However, the analysis of metals in tree leaves among five species Ficus aurea, Ficus benghalensis, Ficus religiosa, Ficus rubiginosa, and Polyalthia longifolia revealed that Ficus aurea is a hyperaccumulator of Cd and good accumulator for other metals, making it a suitable candidate for urban greening. Polyalthia longifolia is a better barrier of toxic elements. Cr possesses the highest carcinogenic risk for the inhabitants and Cd was found to cause the highest potential ecological risk. Metals in each sample type in each sampling site reveal almost a nonpareil relationship that indicates the appraisal of the multi-sample approach. Therefore, it can be said that this scientific study provides an effective tool for assessing urban metal pollution.

Induction of hormesis in plants by urban trace metal pollution

Hormesis is a dose–response phenomenon observed in numerous living organisms, caused by low levels of a large number of stressors, among which metal ions. In cities, metal levels are usually below toxicity limits for most plant species, however, it is of primary importance to understand whether urban metal pollution can threaten plant survival, or, conversely, be beneficial by triggering hormesis. The effects of Cd, Cr and Pb urban concentrations were tested in hydroponics on three annual plants, Cardamine hirsuta L., Poa annua L. and Stellaria media (L.) Vill., commonly growing in cities. Results highlighted for the first time that average urban trace metal concentrations do not hinder plant growth but cause instead hormesis, leading to a considerable increase in plant performance (e.g., two to five-fold higher shoot biomass with Cd and Cr). The present findings, show that city habitats are more suitable for plants than previously assumed, and that what is generally considered to be detrimental to plants, such as trace metals, could instead be exactly the plus factor allowing urban plants to thrive.

Low-cost biomonitoring and high-resolution, scalable models of urban metal pollution

As the global toll on human lives and ecosystems exacted by urban pollution grows, planning tools still lack the resolution to identify priority sites where toxic pollution can be most efficiently averted at a spatial scale that matches funding and management. Here we tackle this gap by demonstrating novel scalable methods to monitor and predict urban metal pollution at high resolution (<5 m) across large areas (10,000–100,000 km2) to guide pollution reduction and stormwater management. We showcase and calibrate predictive models of Zn, Cu, and a synthetic index of pollution for the Puget Sound region of Washington State, U.S., a densely urbanized yet important ecosystem of conservation interest, and exemplify their transferability across the entire United States. We leveraged widely and freely available datasets of car traffic characteristics and land use as predictor variables and trained the models with biological monitoring data of metal concentrations in epiphytic moss from >100 trees based on new rapid and low-cost protocols introduced in this study. Our model predictions, showing that 50% of the total Cu and Zn pollution across the Puget Sound watershed is deposited over only 3.3% of the land area, will allow cities to effectively and efficiently target toxic hotspots.

Biomonitoring potential of five sympatric Tillandsia species for evaluating urban metal pollution (Cd, Hg and Pb)

The present study quantifies non essential heavy metals highly toxic for biological systems (Pb, Hg and Cd) in five autochthonous epiphytic plants from Tillandsia genus (T. recurvata, T. meridionalis, T. duratii, T. tricholepis, T. loliacea) according to different traffic levels (reference, low, medium and high polluted sites) in Asunción (Paraguay). The three metals increased in polluted sites following Pb (till 62.99 ppm in T. tricholepis) > Cd (till 1.35 ppm in T. recurvata) > Hg (till 0.36 ppm in T. recurvata) and Pb and Cd levels were directly related to traffic flow. Although the species showed similar bioaccumulation pattern (namely, higher levels of metals in polluted sites), enrichment factors (maximum EF values 37.00, 18.16, and 11.90 for Pb, Hg, and Cd, respectively) reported T. tricholepis as the most relevant bioindicator due to its wide distribution and abundance in study sites, low metal content in control site and high metal contents in polluted sites, and significant correlations with traffic density of Pb and Cd. This study emphasizes the necessity of biomonitoring air pollution in areas out of air monitoring control such as Asunción, where the high levels of metal pollution especially Pb, may represent an increment of risk for the human population inhabiting this urban area.

Biomarkers of oxidative stress in the land snail, Theba pisana for assessing ecotoxicological effects of urban metal pollution

This study investigates the biomarkers of oxidative stress and heavy metal accumulation for assessing ecotoxicological effects of urban metal pollution in Alexandria city, Egypt. This investigation was performed in the digestive gland of roadside Theba pisana snails obtained from six different sites in the city. Relationships between heavy metal (Zn, Cu, Pb and Cd) concentrations and oxidative stress indicators were also examined. The results showed that mean concentrations of the measured elements (μg g −1 dry weight) were higher in polluted sites when compared to the background levels of the reference site. The pattern of metals accumulation at all sites was Zn > Cu > Pb > Cd. In the metal polluted sites, snails displayed higher mean of catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities, lower reduced glutathione (GSH) content and higher levels of lipid peroxidation (LPO) compared to snails from the reference site. All oxidative stress parameters were positively correlated to heavy metal concentrations except GSH content which exhibits negative correlation with the concentrations of these metals. Our results suggest that the tested antioxidant defenses are sensitive parameters that could be useful as oxidative stress biomarkers in snails exposed to the actual metals in the environment. These biomarkers when complemented with metal accumulation in the digestive gland of snails may provide a powerful biomonitor for the assessment of environmental metal pollution.

Monitoring urban heavy metal pollution using the House Sparrow (Passer domesticus)

The House Sparrow (Passer domesticus) is one of the most successful birds in the urban environment, and has a global distribution. The present study aims to provide baseline data about metals in sparrows from urban environments in the West Bank and to investigate the possibility of using the House Sparrow to monitor metal pollution in urban environments. Concentrations of Cu, Cd, Pb and Zn were measured in different tissues and organs of male and female juvenile (1-4 weeks old) and adult House Sparrows from the West Bank. Tissues and organs had the following order of metal richness: liver > stomach > bone > lung, feathers > muscles > egg contents, brain > heart > egg shell. Significant correlation coefficients were observed for the concentrations of Cu, Pb, and Zn in the egg shell and for the egg contents. Male and female Sparrows showed no significant differences in their metal concentrations. Adult Sparrows collected from rural areas were found to have significantly less Cu, Pb, and Zn (but not Cd) concentrations than those from urban environments. In order to investigate metal accumulation with age, metal concentrations were plotted against age stage (egg, 1-, 2-, 3-, and 4-week-old juveniles and adults). Significant relationships were observed between age stage and Cu, Pb, and Zn concentrations. The results provide some evidence for the potential of the House Sparrow as a biomonitor for urban heavy metal pollution. However, further issues regarding metal physiological regulation and the correlations between metals in the environment and those in tissues of the House Sparrows have to be addressed before recommending this bird as a biomonitor for urban metal pollution.

Radioisotope excited X-ray fluorescence analysis of Asellus Aquaticus (Crustacea: Isopoda) from Istanbul as an indicator of environmental metal pollution

Some metal contents of the freshwater isopod: Asellus aquaticus (Crustacea:Isopoda), collected from the pool of the botanical garden of Istanbul University(at the vicinity of old city center of Istanbul), were analysed, in orderto investigate urban metal pollution. The analysis of the homogenized sampleof isopods indicated that it contained K, Ca, Mn, Fe, Cu, Ni, Zn, Pb, Br,Rb, Sr, Y, Zr, Ba, Cd, Cs and Hg in different amounts. The results were comparedwith those of other isopods and various organisms.

Associations between Trace Metals in Sediment, Water, and Guppy, Poecilia reticulata (Peters), from Urban Streams of Semarang, Indonesia

The present study aims to answer the question whether the amount of metal in aquatic biota reflects the concentrations in the sediment and water, and whether the physico-chemical properties of the water and sediment have any influence on the suspected relationship. A study was made of 101 small streams in the city of Semarang, Central Java, Indonesia. Data on fish occurrence in 63 streams of the greater Semarang indicated that the guppies did not avoid the highly polluted sites. No significant difference in body weight between sites was found. Significant differences were found in metal body concentrations (Pb and Zn) between fish collected from sites with different degrees of pollution. A significant declining trend of Pb concentrations with increasing organism size was observed, whereas for two other metals, Zn and Cu, the concentrations did not depend on the body weight. Apparently, body concentrations of these two metals are regulated and maintained at a certain concentration. For the relationships between metal concentrations in water, sediment and fish, water and sediment parameters, and fish dry weight, the presence of significant multiple correlations and bivariate correlation (in 17 of 91 pairs of variables) indicated that, in general, abiotic parameters and body size had no influence on the metal flux from sediment to water, and into fish. Results of partial correlation analyses further suggested that metal concentrations in the sediments were the most important factor governing the metal body concentrations of fish. The present study indicates that the guppy Poecilia reticulata from urban streams is a potential bioindicator for urban metal pollution, especially with respect to their (1) spatial distribution over sites of all pollution regimes and (2) variation in metal accumulation levels reflecting the degree of pollution.