Assessment of Heavy Metals Accumulation in Shrubs And herbs along some Selected Roads in Mubi, Nigeria
Article Information
Tizhe Tari Dlama1,*, Yusuf Sankem Comfort1, Kwaya Vawanje Bitrus2, James Ussa1, Sunday Bukata Dorathy1
1Department of Botany, Adamawa State University, Mubi, Nigeria
2Department of Biological Sciences, Federal University of Kashere, Gombe State, Nigeria
*Corresponding Author: Dr. Tizhe Tari Dlama, 1Department of Botany, Adamawa State University, Mubi, Nigeria
Received: 20 June 2020; Accepted: 26 June 2020; Published: 02 July 2020
Citation: Tizhe Tari Dlama, Yusuf Sankem Comfort, Kwaya Vawanje Bitrus, James Ussa, Sunday Bukata Dorathy. Assessment of Heavy Metals Accumulation in Shrubs and Herbs along some Selected Roads in Mubi, Nigeria. Journal of Environmental Science and Public Health 4 (2020): 150-160.
View / Download Pdf Share at FacebookAbstract
This study assessed the accumulation of heavy metals in shrubs and herbs along Mubi Mararaba Road (MMRR), Mubi Maiha Road (MMR), Adamawa State University Second Gate (ADSU2G) road and Adamawa State University Ecological Garden (ADSUEG) in Mubi. The fresh leaves samples of the herbs and shrubs in these aforementioned locations were collected at a distance between 0-100 m and 100-200 m away from the road. After identification, the samples were air dried at room temperature and were pulverized into fine powder using wooden pestle and mortar. Analyses of heavy metals were carried out using standard procedures. The investigation revealed varied concentrations of the heavy metals such as Cadmium (Cd), Copper (Cu), Zinc (Zn), Iron (Fe) and Lead (Pb) in both the herbs and shrubs; with those obtained at a distance between 0-100 having higher concentration of most of the metals. The study therefore, concluded that, the concentrations of Cd, Zn, Pb, Fe and Cu at the study areas which were within the ranges of 0.16-0.42 mg/kg, 2.75-7.82 mg/kg, 0.12-0.53 mg/kg, 24.13-69.52 mg/kg and 3.21-9.16 mg/kg respectively in both the herbs and shrubs were within the allowable limit for plants; and the concentrations of these metals were dependent upon distance of the plants from road.
Keywords
Heavy metals; Concentration; Plants; Roadsides
Heavy metals articles, Concentration articles, Plants articles, Roadsides articles
Heavy metals articles Heavy metals Research articles Heavy metals review articles Heavy metals PubMed articles Heavy metals PubMed Central articles Heavy metals 2023 articles Heavy metals 2024 articles Heavy metals Scopus articles Heavy metals impact factor journals Heavy metals Scopus journals Heavy metals PubMed journals Heavy metals medical journals Heavy metals free journals Heavy metals best journals Heavy metals top journals Heavy metals free medical journals Heavy metals famous journals Heavy metals Google Scholar indexed journals Concentration articles Concentration Research articles Concentration review articles Concentration PubMed articles Concentration PubMed Central articles Concentration 2023 articles Concentration 2024 articles Concentration Scopus articles Concentration impact factor journals Concentration Scopus journals Concentration PubMed journals Concentration medical journals Concentration free journals Concentration best journals Concentration top journals Concentration free medical journals Concentration famous journals Concentration Google Scholar indexed journals Plants articles Plants Research articles Plants review articles Plants PubMed articles Plants PubMed Central articles Plants 2023 articles Plants 2024 articles Plants Scopus articles Plants impact factor journals Plants Scopus journals Plants PubMed journals Plants medical journals Plants free journals Plants best journals Plants top journals Plants free medical journals Plants famous journals Plants Google Scholar indexed journals Roadsides articles Roadsides Research articles Roadsides review articles Roadsides PubMed articles Roadsides PubMed Central articles Roadsides 2023 articles Roadsides 2024 articles Roadsides Scopus articles Roadsides impact factor journals Roadsides Scopus journals Roadsides PubMed journals Roadsides medical journals Roadsides free journals Roadsides best journals Roadsides top journals Roadsides free medical journals Roadsides famous journals Roadsides Google Scholar indexed journals Ecological Garden articles Ecological Garden Research articles Ecological Garden review articles Ecological Garden PubMed articles Ecological Garden PubMed Central articles Ecological Garden 2023 articles Ecological Garden 2024 articles Ecological Garden Scopus articles Ecological Garden impact factor journals Ecological Garden Scopus journals Ecological Garden PubMed journals Ecological Garden medical journals Ecological Garden free journals Ecological Garden best journals Ecological Garden top journals Ecological Garden free medical journals Ecological Garden famous journals Ecological Garden Google Scholar indexed journals Environmental pollutants articles Environmental pollutants Research articles Environmental pollutants review articles Environmental pollutants PubMed articles Environmental pollutants PubMed Central articles Environmental pollutants 2023 articles Environmental pollutants 2024 articles Environmental pollutants Scopus articles Environmental pollutants impact factor journals Environmental pollutants Scopus journals Environmental pollutants PubMed journals Environmental pollutants medical journals Environmental pollutants free journals Environmental pollutants best journals Environmental pollutants top journals Environmental pollutants free medical journals Environmental pollutants famous journals Environmental pollutants Google Scholar indexed journals toxic articles toxic Research articles toxic review articles toxic PubMed articles toxic PubMed Central articles toxic 2023 articles toxic 2024 articles toxic Scopus articles toxic impact factor journals toxic Scopus journals toxic PubMed journals toxic medical journals toxic free journals toxic best journals toxic top journals toxic free medical journals toxic famous journals toxic Google Scholar indexed journals chlorophyll articles chlorophyll Research articles chlorophyll review articles chlorophyll PubMed articles chlorophyll PubMed Central articles chlorophyll 2023 articles chlorophyll 2024 articles chlorophyll Scopus articles chlorophyll impact factor journals chlorophyll Scopus journals chlorophyll PubMed journals chlorophyll medical journals chlorophyll free journals chlorophyll best journals chlorophyll top journals chlorophyll free medical journals chlorophyll famous journals chlorophyll Google Scholar indexed journals herbs articles herbs Research articles herbs review articles herbs PubMed articles herbs PubMed Central articles herbs 2023 articles herbs 2024 articles herbs Scopus articles herbs impact factor journals herbs Scopus journals herbs PubMed journals herbs medical journals herbs free journals herbs best journals herbs top journals herbs free medical journals herbs famous journals herbs Google Scholar indexed journals
Article Details
1. Introduction
Environmental pollutants have continued to be a matter of great concern and challenge being faced by all nations globally. These pollutants could be naturally occurring compounds or foreign matter which when in contact with the environment result to adverse changes [1]. Among all the pollutants, heavy metals have received much attention by the environmental chemists due to their toxic nature. Cadmium (Cd), Zinc (Zn), Copper (Cu), Lead (Pb), Iron (Fe) and Arsenic (As) are some of the heavy metals [2]. Some of these metals originate from tyres, engine oil consumption, brake wear and road surface material [3]; and some from anthropogenic activities such as: mining, combustions, vehicular emissions and agro-chemicals [4]. Although, some of these heavy metals are essential for some important processes in many living organisms, including humans [5, 6], however, they are generally toxic when their concentrations exceed certain thresholds.
Plants growing along vehicular roads are exposed to high level of heavy metals pollution. They absorbed these metals through their roots and vascular system. Contaminations by heavy metals could alter the chemical compositions of plants and thus, seriously affecting the quality and efficacy of the natural products produced by plants especially plants that are of medicinal importance [7]. High concentrations of these metals in the plant could also affect the ability of the plant to produce chlorophyll, increase the plant oxidative stress and weaken stomata resistance [8]. Consumption of plants containing heavy metals especially when they are present in higher quantity could posed a great health risk; as some of these metals (Pb, Cd, Zn and Cu) are responsible for certain diseases that have lethal effect on humans [9]. Plants growing in environment contaminated by heavy metals are more affected by the metals than other organisms. Several researchers reported the presence of heavy metals in plants [10, 11]. However, different plant species differ in their strategies to resist pollution, especially of heavy metals.
In the northern part of Nigeria, especially along the major roads linking Mubi to other towns and villages within and outside Mubi North and South local government areas of Adamawa State, Nigeria, farmers are fond of planting crops very close to the roads. This exposed crops to vehicular emissions and other sources of heavy metal pollutants, thus resulting in the accumulation of heavy metals in their tissues. This study, therefore, would help provide information on the level at which plants especially shrubs and herbs situated along vehicular roads could accumulate heavy metals so as to advise the farmers and those who use shrubs and herbs for food and medicinal purposes in that region and elsewhere appropriately.
2. Materials and Methods
2.1 Study area
The study was carried out in Mubi, a commercial centre of Adamawa State, Nigeria. It has so many networks of roads linking the main town to many other villages and local government areas such as Maiha, Michika and Hong. The major road networks in Mubi include: Mubi to Mararaba road, Mubi to Maiha road and Mubi to Bazza road. These roads, especially Mubi/Mararaba road usually have very high density of traffic, and farmers during farming season plant their crops very close to the busy roads. Mubi lies within latitude 100 16'52"N of the equator and longitude 13016'48"E of the prime median. It falls within the Sudan Savanna vegetation zone of Nigeria; and the annual rainfall is about 1088 mm and has an average annual temperature of 260C. The land area of Adamawa State University, Mubi campus is 1.039 km2 and its perimeter is 4.73 km (Figure 1).
Figure 1: Map of Adamawa showing study area.
2.2 Sample collections
Samples of the roadsides herbs were collected from four different locations, these include: MMRR, MMR, ADSU2G and ADSUEG. The fourth location served as a control. In each of the sampling locations, the samplings were made between a distances of 0–100 m and 100–200 m away from the roadsides. The samples were collected and placed into a well labeled polythene bag.
2.3 Identification and preparation of plant samples for heavy metals assessment
The herbs and shrubs samples collected were taken to the herbarium unit of the department of Botany, Adamawa State University, Mubi for Identification. The leaves of herb and shrub samples collected were first washed using a running tap water so as to wash off dirt after which they were shade dried at room temperature. Thereafter, the leaves samples were then pulverized into a very fine powder and stored in a black polythene bag pending heavy metals analysis.
2.4 Analysis of heavy metals
Sieved sample (0.5 g) was accurately weighed into 100 cm3 beaker and a mixture of 5 cm3 concentrated nitric acid and 2 cm3 perchloric acid was added and digested on low heat hot plate until the content was about 2 cm3.The digest was allowed to cool, filtered into 50 cm3 standard flask using 0.45 um millipore filter kit. The beaker was rinsed with small portions of distilled water and then filter into the flask. Triplicate digestion of each sample was carried out together with blank digest without the plant sample. Heavy metal quantization was carried out by Atomic Absorption Spectrophotometer (AAS).
3. Results
3.1 Analysis of heavy metals accumulation in shrubs along some selected roads in Mubi
The heavy metals such as: Cd (0.42 mg/kg), Zn (7.75 mg/kg), Pb (0.37 mg/kg), Fe (63.05 mg/kg) and Cu (9.1 mg/kg) of Cassia obtusifolia obtained at a distance between 0-100 m, along Mubi Mararaba road (MMRR) was significantly (at p<0.05) the highest compared to the Cd (0.28 mg/kg), Zn (4.75 mg/kg), Pb (0.23 mg/kg), Fe (55.16 mg/kg) and Cu (6.76 mg/kg) of C. obtusifolia obtained between 100-200 m along the same locaton (MMRR). Similar observations were made for the Cd (0.39 mg/kg), Zn (7.82 mg/kg), Fe (69.52 mg/kg) and Cu (8.34 mg/kg) and Cd (4.85 mg/kg), Pb (0.26 mg/kg) and Fe (53.96 mg/kg) of C. obtusifolia and Waltheria indica respectively, obtained along Mubi/Maiha road (MMR) and Adamawa State University second gate road (ADSU2G) at the same distance (0-100 m). However, the Pb (0.32 and 0.20 mg/kg) content of the C. obtusifolia obtained from these distances (0-100 and 100-200 m) did not differ significantly. The same incidence were observed for the Cd (0.27 and 0.25 mg/kg) and Cu (6.25 and 6.00 mg/kg) of W. Indica obtained also at the distances of 0-100m and 100-200 m respectively. The heavy metals content: Cd (0.21 mg/kg), Zn (2.87 mg/kg), Pb (0.16 mg/kg), Fe (43.63 mg/kg) and Cu (5.13 mg/kg), of plant sample (Guiera senegalensis) from the control location [Adamawa State University Ecological Garden (ADSUEG)] were all lower than those of the shrubs samples obtained from the roadsides (Table 1).
3.2 Analysis of heavy metals accumulation in herbs along some selected roads in Mubi
The Cd content of Gomphrena celosoides (0.35 and 0.31 mg/kg), Melochia corchorifolius (0.23 and 0.16 mg.kg), Bidens pilosa (0.26 and 0.20 mg/kg) and Mitracarpus villosus (0.16 mg/kg) obtained at distances between 0-100 and 100-200 m at MMRR, MMR, ADSU2G and ADSUEG respectively, were not significantly different. Similar observation was made for the Pb content, 0.29 and 0.27 mg/kg (MMRR), 0.19 and 0.12 mg/kg (MMR), 0.20 and 0.15 mg/kg (ADSU2G) at distances between 0-100 and 100-200 m respectively, except for the herb sample from ADSUEG (0.53 mg/kg) which was significantly the highest. The Zn and Fe contents of herbs, G. celosoides (6.16 and 68.66 mg/kg), M. corchorifolius (4.12 and 0.19 mg/kg) and B. pilosa (4.59 and 45.75 mg/kg) from MMRR, MMR and ADSU2G sampling locations respectively at distances between 0-100 m were significantly the highest compared to those at distance between 100-200 m and that of the control location (2.78 and 37.13 mg/kg). The Cu content of M. corchorifolius (5.32 mg/kg) and B. pilosa (5.63 mg/kg) from MMR and ADSU2G respectively at distance between 0-100 m were significantly the highest in comparism to herbs at other distance (100-200 m) and sampling locations (MMRR and ADSUEG) (Table 2).
3.3 Comparism of heavy metals accumulation of herbs and shrubs from the same sampling location at different distances
The Cd (0.42 mg/kg), Zn (7.76 mg/kg), Pb (0.37 mg/kg) and Cu (9.16 mg/kg) of shrub (C. obtusifolia) from MMRR sampling location at 0-100 m were significantly the highest compared to those of herb (G. celosoides) at all distances and shrub (C. obtusifolia) at 100-200 m. However, the Fe content (68.05 mg/kg) of G. celosoides, at the same sampling distance (0-100 m) was significantly the highest compared to those at other distances. The significantly lowest content of these heavy metals especially Zn (4.75 mg/kg), Pb (0.23 mg/kg) and Fe (55.16 mg/kg) were observed at distance between 100-200 m in C. obtusifolia (Table 3). The Zn (4.85 mg/kg), Pb (0.26 mg/kg) and Cu (6.25 mg/kg) contents of Waltheria indica from ADSU2G at distance between 0-100 m were significantly the highest compared to Zn (3.65 mg/kg), Pb (0.15 mg/kg) and Cu (5.00 mg/kg) of B. pilosa, which were the lowest significantly at distance between 100-200 m. However, the Cd and Fe contents of the B. pilosa at 0-100 m and all shrubs from 0-100 m and 100-200 m respectively were significantly similar but different from those of B. pilosa at 100-200 m which were significantly the lowest (Table 3).
The Cd (0.39 mg/kg), Zn (7.82 m/kg), Pb (0.32 mg/kg), Fe 69.52 mg/kg) and Cu (8.34 mg/kg) contents of shrub (C. obtusifolia) from MMR sampling location at 0-100 m were significantly the highest in comparism to the Cd (0.16 mg/kg), Zn (2.75 mg/kg), Pb (0.12 mg/kg), Fe (24.13 mg/kg) and Cu (3.21 mg/kg) contents of herb (M. corchorifolius) at 100-200 m from the same sampling location (MMR) which were significantly the lowest (Table 3). In ADSUEG (control) sampling location, the Cd (0.21 mg/kg), Fe (43.63 mg/kg) and Cu (5.13 mg/kg) contents of shrub (G. senegalensis) were significantly the highest compared to the Cd (0.16 mg/kg), Fe (37.13 mg/kg) and Cu (4.16 mg/kg) content of the herb (M. villosus) which were the lowest. The Zn (2.78 and 2.87 mg/kg) content of both the herb (M. villosus) and shrub (G. senegalensis) respectively, were not significantly different. However, the Pb content of M. villossus (0.53 mg/kg) was significantly the highest compared to that of G. senegalensis (0.16 mg/kg) at p<0.05 (Table 3).
3.4 Comparism of the heavy metals accumulation of herbs and shrubs from all sampling locations at different distances
In comparism of the heavy metals content of roadside shrubs and herbs from all sampling locations (MMRR, MMR, ADSU2G AND ADSUEG) and at different sampling distances (0-100 and 100-200 m), it was observed that, the Cd (0.42 mg/kg) content of C. obtusifolia at 0-100 m from MMRR was significantly the highest followed by that of C. obtusifolia (0.39 mg/kg) from MMR at the same sampling distance (0-100 m). The significantly lowest Cd content were the ones of M. villosus (0.16 mg/kg) and M. corchorifolia (0.16 mg/kg) all at 100-200 m from ADSUEG and MMR sampling locations respectively. The Zn (7.82 mg/kg) and Pb (0.53 mg/kg) contents of C. obtusifolia at 0-100 m and M. villosus from MMR and ADSUEG respectively were the highest significantly whereas the Zn (2.75 mg/kg), Fe (24.13 mg/kg), Cu (3.21 mg/kg) and Pb (0.12 mg/kg) contents of M. corchorifolia at 100-200 m all from MMR were the lowest. However, the Fe (69.52 mg/kg) content of C. obtusifolia at 0-100 m still from same location (MMR) was the highest significantly, but not different from that of G. celosoides at 0-100 m from MMRR. The Cu (9.16 mg/kg) at 0-100 m from MMRR was the highest, but also not significantly different from that of C. obtusifolia (8.33 mg/kg) also at 0-100 m from MMR (Table 4).
Means along the column of plants from the same sampling location without a superscript asterisk (*) are not statistically significantly different at p<0.05.
Key: MMRR= Mubi Mararaba Road; MMR= Mubi Maiha Road; ADSU2G= Adamawa State University Second Gate; ADSUEG= Adamawa State University Ecological Garden; CO=Cassia obtusifolia; WI=Waltheria indica; GS=Guiera senegalensis; Cd= Cadmium; Zn= Zinc; Pb= Lead; Fe= Iron; Cu= Copper.
Table 1: Analysis of heavy metals accumulation in shrubs along some selected roads in Mubi.
Means along the column of plants collected from the same location without a superscript asterisk (*) are not statistically significantly different at p<0.05.
Key: MMRR= Mubi Mararaba Road; MMR= Mubi Maiha Road; ADSU2G= Adamawa State University Second Gate; ADSUEG= Adamawa State University Ecological Garden; MV=Mitracarpus villosus; GC=Gomphrena celosoides; MC=Melochia corchorifolius; BP=Biden pilosa ; Cd= Cadmium; Zn= Zinc; Pb= Lead; Fe= Iron; Cu= Copper.
Table 2: Analysis of heavy metals accumulation in herbs along some selected roads in Mubi.
Means with the same superscript letter(s) along the column are not statistically significantly different at p<0.05.
Key: MMRR= Mubi Mararaba Road; MMR= Mubi Maiha Road; ADSU2G= Adamawa State University Second Gate; ADSUEG= Adamawa State University Ecological Garden; CO=Cassia obtusifolia; WI=Waltheria indica; MV=Mitracarpus villosus; GS=Guiera senegalensis; GC=Gomphrena celosoides; MC=Melochia corchorifolius; BP=Bidens Pilosa; Cd= Cadmium; Zn= Zinc; Pb= Lead; Fe= Iron; Cu= Copper.
Table 3: Comparism of heavy metals accumulation of herbs and shrubs from the same sampling location at different distances.
Means with the same superscript letter(s) along the column are not statistically significantly different at p<0.05.
Key: MMRR= Mubi Mararaba Road; MMR= Mubi Maiha Road; ADSU2G= Adamawa State University Second Gate; ADSUEG= Adamawa State University Ecological Garden; CO=Cassia obtusifolia; WI=Waltheria indica; MV=Mitracarpus villosus; GS=Guiera senegalensis; GC=Gomphrena celosoides; MC=Melochia corchorifolius; BL=Bidens Pilosa; Cd= Cadmium; Zn= Zinc; Pb= Lead; Fe= Iron; Cu= Copper.
Table 4: Comparism of the heavy metals accumulation of herbs and shrubs from all sampling locations at different distances.
4. Discussion
Analysis of heavy metals content of shrub samples collected along roadsides of MMRR, MMR, ADSU2G and ADSUEG based on their distances from road showed variation in their contents of heavy metals such as Cd, Zn, Pb, Fe and Cu. Shrubs (C. occidentalis and W. indica) obtained along the roadsides from all sampling locations between 0-100 m from the roadsides had significantly higher content of all the heavy metals than those of shrubs collected between 100-200 m. The higher content of these heavy metals in shrubs obtained between 0-100 m might be attributed to their nearness to roadsides as soil and plants close to roads are the major recipient of large amount of heavy metals from vehicular emissions [12, 13]. Emission from vehicles contain heavy metals that could accumulate in roadside plants [14]. The heavy metals content of shrub (G. senegalensis) from the control location (ADSU ecological garden) were significantly the lowest compared to those of shrubs from roadsides. This justify the reports that concentrations of heavy metals in plants are closer to roads than sites away from roads [15]. The concentrations of these heavy metals in shrubs obtained from roadsides, which varied between 0.23 to 0.42 mg/kg (Cd), 4.55 to 7.82 mg/kg (Zn), 0.20 to 0.37 mg/kg (Pb), 43.79 to 69.52 mg/kg (Fe) and 5.53 to 9.16 mg/kg (Cu) from all sampling distances (0-100 m and 100-200 m) and locations were all within the allowable limit of 20, 2, 100 and 10 mg/kg for Zn, Pb, Fe and Cu respectively in plants. Concentration of heavy metals that are within the allowable limit for plants was similarly reported by Alexander (2015) in the leaves sample of Sida acuta obtained along Mubi/Mararaba and Mararaba/Michika roads. Contrary findings were, however, reported by [9, 11]. When they observed higher concentrations of Cu, Fe, Zn and Pb that ranges between 11.8 to 15.5 µg/g, 167.4-181.4 µg/g, 42.9-88.5 µg/g and 4.86 – 8.94 µg/g respectively, which were far above the thresholds for plants. Contradiction in the concentrations of heavy metals in plants reported in this study and those of [9, 11], could be due to differences in distances from roads from which these plants samples were collected, availability of these metals in soils of sampling locations [16] , type of plant species analyzed for presence of heavy metals [17] and density of traffic along the sampling locations [18].
Similar observations were made for the heavy metals content of herbs (G.celosoides, M. corchorifolius, B. pilosa and M. villosus) from the same sampling locations where those shrubs were collected. Virtually all the heavy metals where significantly higher in herbs (G.celosoides, M. corchorifolius and B. linn) obtained between 0-100 m from the roads. Unlike in shrubs (C. occidentalis and W. indica) obtained between 0-100 m, the Cd content of herbs (G.celosoides, M. corchorifolius and B. pilosa) in that same locations and distance were higher, but not significantly different from those of herbs (G.celosoides, M. corchorifolius and B. pilosa) collected between 100-200 m. The Pb content of herb from control location was significantly higher than those of herbs from all sampling locations and distances. This might be due to differences in species.
Comparism of the effect of distance from roadsides on heavy metals content of roadside herbs and shrubs obtained from the same location showed that, shrub (C. occidentalis) collected from MMRR, the most busiest road in the study area, significantly had the highest concentrations of all the heavy metals analysed (Cd, Zn, Pb and Cu) except Fe at distance between 0-100 m compared to those of the herb (G. celosoides) at the same distance. The same was observed for C. occidentalis and M. corchorifolius both at the same distance (0-100 m) and location (MMR). The heavy metals content of G. senegalensis from the control location (ADSUEG) were also mostly observed to be significantly higher than those of M. villosus. This could be a justification of the reports that concentration of heavy metals differ for different plant species collected from the same location [19].
Comparism of the heavy metals content of herbs and shrubs from all sampling locations showed that, MMRR sampling location had higher contents of most of the heavy metals which include: Cd (0.42 mg/kg), Fe (68.66 mg/kg) and Cu (9.16 mg/kg) than other sampling locations (MMR, ADSUEG and ADSU2G). MMR had significantly higher content of Zn (7.82 mg/kg) and Cu (8.33 mg/kg), which was significantly similar to that of MMRR. The higher content of most of these heavy metals in herb and shrub from MMRR might be attributed to the fact that they were exposed to higher concentration of vehicular emissions than those in other locations; as MMRR is the most busiest vehicular road in the study area with heavy traffic.
5. Conclusion
From the findings of this study, the researchers concluded the following:
Herbs and Shrubs along Mubi/Mararaba road had higher concentration of Cd, Fe and Cu. The concentrations of heavy metals such as: Cd, Zn, Cu, Fe and Pb in herbs and shrubs along Mubi/Mararaba, Mubi/Maiha, ADSU second gate roads and ADSU ecological garden are within the allowable limit for plants. Concentrations of heavy metals in herbs and shrubs along vehicular roads are dependent upon the distance from roadsides. Accumulation of heavy metals in plants from the same sampling location and distance are determined by the type and kind of plant species.
Conflicts of Interest
The authors declared no conflicts of interest.
References
- Masindi V, Muedi KL. Environmental contamination by heavy metals. Open access peer-reviewed chapter ( 2018): 116-133.
- Herawati N, Suzuki S, Hayashi K, et al. Cadmium, copper and zinc levels in rice and soil of Japan, Indonesia and China by soil type. Bulletin of Environmental Contamination and Toxicology 64 (2000): 33-39.
- Zhang F, Yan X, Zeng C, et al. Influence of traffic activity on heavy metal Concentrations of roadside farmland soil in mountainous areas. International Journal of Environmental Resources and Public Health 9 (2012): 1715-1731.
- Al-khashman OA. Heavy metal distribution in dust, street dust and soils from the work place in Karak Industrial estate, Jordan. Atmospheric Environment 38 (2004): 6803-6811.
- Juvanovic S, Carrot F, Deschamps N, et al. A study of the air pollution in the surroundings of an aluminium smelter using Epiphytic and Lithophytic Lichens. Journal of Trace Microprobe Techniques 13 (1995): 43-47.
- Lapitals G, Greg U, Dunemann L, et al. ICP-MS in the determination of trace and ultra trace elements in the human body. International Laboratory 5 (1995): 21-27.
- Gopal NM, Tejaswini J, Mantry S, et al. International standards of medicinal plants. International Journal of Innovation and Pharmaceutical Sciences Resources 2 (2014): 2498-2532.
- Ashraf MA, Maah J, Yusoff I. Heavy metals accumulation in plants growing in extin mining catchment. International Journal of Environmental Science and technology 8 (2011): 401-416.
- Obaseki OO, Amoo IA, Ayesanmi AF, et al. Effects of traffic density on heavy metal content of soil and vegetation along roadsides leading to Akure-Ondo State, Nigeria. FUTA Journal of Research in Sciences 1(2014):35-42.
- Alexander P. Assessment of heavy metals in roadside surface soil and vegetable along Mubi Michika major road in Adamawa State, Nigeria. International Journal of Applied Sciences and Biotecnology 3 (2015): 545-551.
- Kirpik M, Buyuk G, Inan M, et al. The heavy metal content of some herbal plants on the roadside of Adana-Gaziantep highway. Journal of Agricultural Faculty of Gaziosmanpasa University 34 (2017): 129-136.
- Jose A, Faz A, Martinez-Martinez S. Identification of heavy metals sources by multivariable analysis in a typical Mediterranean city. Environmental Monitoring Assessment 169 (2009): 519-530.
- Saeedi M, Hosseinzadeh M, Jamshidi A et al. Assessment of heavy metals contamination and leaching characteristics in highway side soils, Ira Environmental Monitoring Assessment 151 (2009):231-241.
- Feng J, Wang Y, Zhao J, et al. Source attributions of heavy metals in rice plant along highway in Eastern China. Journal of Environmental Science 23 (2011): 1158-1164.
- Carlosena A, Andrade J, Prada D. Searching For Heavy Metals Grouping Roadside Soils as a Function of Motorized Traffic Influence. Talanta 47 (1998): 753-767.
- Khan MA, Ahmad I, Rahman I. Effect of environmental pollution on heavy metals content of Wilthania somnifera. Journal of the Chinese Chemical Society 54 (2007): 339-343.
- Zhao S, Duo L. Bioaccumulation of cadmium, copper, zinc and nickel by weed species from municipal solid waste compost. Polish Journal of Environmental Studies 24 (2015): 413-417.
- Nabuloa G, Oryem-Oroga H, Diamond M. Assessment of lead, cadmium and zinc contamination of roadside soils, surface frilms and vegetations in Kampala city, Uganda. Environmental Research 101 (2006): 41-52.
- Annan K, Dickson RA, Isaac K, et al. The heavy metal contents of some selected medici-nal plants sampled from different geographical locations. Pharmacognosy Resources 5 (2013): 103-108.