Benthic foraminifera and trace metal distribution: a case study from the Burullus Lagoon,Egypt

Benthic foraminifera are widely used to detect the health of their habitat, where they are very sensitive to even slight variations in the ecosystem. Therefore, the main objectives of this study are to examine the benthic foraminiferal assemblages in the sediments of Burullus Lagoon, evaluate the pollution levels and deduce the impact of trace metals on foraminifera. The continuous discharge of trace metals from agricultural, industrial and domestic sources into the lagoon may lead to a severe environmental problem. The concentrations of Mn, Cu, Cd, Zn and Pb within the sediments were measured. Recently, the assessment of contamination is principally based on the contamination indices which provide fast and simple quantitative values on the degree of pollution in a given aquatic environment. Thus, some indices, including the contamination factor, the degree of contamination, pollution load index, geoaccumulation index, ecological risk factor and potential ecological risk index are applied in this investigation. Based on the contamination factors, the sediments are very highly contaminated with Cd, considerably to very highly contaminated with Cu and Zn, moderately contaminated with Mn, low to moderately contaminated with Pb. All sites display very high values for the degree of contamination. Moreover, the values of the pollution load index are higher than 1, indicating that the lagoon is polluted. Depending on the geoaccumulation index, the contaminants are arranged as follows Cd > Zn > Cu > Mn > Pb. It is clear that Cd is the main contributor to the ecological risk factor in Burullus Lagoon. Concerning the richness of the foraminiferal assemblages, it fluctuates between 1–5 species per sample. Because of its higher tolerance to extreme conditions (changes in salinity and pollution), Ammonia tepida is the most abundant species. The occurrence of rare living individuals (25) is restricted only to sites close to El-Boughaz Inlet where higher salinity and lower levels of pollution are recorded. The same trend of distribution is shown by Cribroelphidium excavatum and miliolids, where they occur at sites with higher salinities. The occurrence of test deformities in all the studied sites may be related to the response of benthic foraminifera to trace metal. The forms of deformation include spiroconvex, reduced chambers, twisted tests, twinning, additional chamber and complex forms. The deformation depends on the nature of pollutants. Twinning and reduced chambers are the most dominant forms in areas close to the agricultural drainage (southern drains), while complex forms are abundant in areas close to industrial drainage (El-Gharbia drain). Thus, salinity and pollution may be the most regulatory factors controlling the distribution of foraminifera. This investigation confirmed the role of benthic foraminifera as a good ecological indicator in Burullus Lagoon.     

Distribution and enrichment of heavy metals among sediments,water body and plants in Hengshuihu Wetland of Northern China

In this study, a survey for the spatial distribution of heavy metals in Hengshuihu Wetland of China was conducted. Samples were collected from three compartments, water, sediment, and reed (Phragmites communis Trin), at different sites, and their contents of heavy metals, including mercury (Hg), arsenic (As), chromium (Cr), lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd), were analyzed. The results showed heavy metals in the sediments distributed in the Buffer Zone and Wangkou Sluice area at concentrations relatively higher than those in other areas, while concentrations in the Core Zone were lower. The heavy metal concentrations of water bodies in all areas, except those for Hg and Pb, were lower than the cutoff values for the first-grade water quality that was set as the highest standard to protect the national nature reserves. The heavy metal distributions among the three compartments were significantly different, with the following order: sediment > plant > water. In the reeds, accumulated amounts of different heavy metals varied in the following order: Hg > Zn > As > Cu > Cr. Concentrations of heavy metals only showed weak correlations between the water bodies and the sediments. Concentrations of heavy metals (except Hg and Cr) had no corrections between the sediments and the reeds. The distribution of mercury indicated that it enters the lake mainly from the atmosphere and outside water bodies. The concentrations of As, Hg, Cr, Cu and Zn in different parts of the reeds were detected and their abundances were ranked in the following order: root > leaf > stem.     

Heavy metals in wetland soils along a wetland-forming chronosequence in the Yellow River Delta of China: Levels,sources and toxic risks

Surface soil (0–20 cm) samples were collected from four chronological sequences of wetlands (i.e., >50-yr-old wetlands, 40-yr-old wetlands, 30-yr-old wetlands and 10-yr-old wetlands) in the Yellow River Delta of China in May and June of 2007. Total contents of Al, As, Cd, Cr, Cu, Ni, Pb and Zn were determined using inductively coupled plasma atomic absorption spectrometry (ICP-AAS) to investigate the levels, sources and toxic risks of heavy metals in these wetlands. Our results showed an increasing trend for Pb, Cu and Zn along the wetland-forming chronosequence although their pollution levels were low. Both As and Cd exhibited significant enrichment due to their high enrichment factor (EF) values (EF > 5), especially in older wetlands (i.e., >50-yr-old and 40-yr-old wetlands), whereas other heavy metals were minimally or moderately enriched in this region. The results of principal component analysis showed that 83.09% of total variance based on eigenvalues (eigenvalue > 1) could be explained by three principal components (PCs) in four wetlands. The source of Al, Cu, Pb and Zn was different from Cd, Cr and Ni. According to the sediment quality guidelines (SQGs) of China, soil samples in the younger wetlands, especially the 10-yr-old wetlands, were moderately polluted by As, Cd and Ni. According to the SQGs of US EPA, all soil samples were heavily polluted by As and moderately polluted by Ni and soil samples in the older wetlands were moderately polluted by Cr. However, with the exception of As and Ni, the contents of other heavy metals in the four wetlands did not exceed the probable effect level (PEL) values. As, Cd and Ni were identified as heavy metals of primary concerns in four wetlands, Cr were of moderate concern in older wetlands, and Pb, Cu and Zn should be paid more attention in younger wetland (i.e., 10-yr-old and 30-yr-old wetlands). A new and sensitive toxic risk index (TRI) is developed for the accurate assessment of toxic risk for heavy metals in wetland soils compared with the sum of the toxic units (∑TUs), and As, Cr, Ni and Cd showed higher contributions to TRI.     

Resistance characteristics of Cedrus deodara and Sabina chinensis to heavy metal accumulation under different atmospheric conditions

Cedrus deodara and Sabina chinensis are widely planted in North China. The needles of C. deodara and S. chinensis were sampled in the urban, suburban, and rural districts of Tianjin where the atmospheric conditions are significantly different according to the environmental monitoring results. The Cu, Mn, Zn, and Pb concentrations in the samples were examined via ICP. The resistance indexes, and the malonic aldehyde (MDA), soluble sugar, and free proline levels were also determined. The Pearson coefficients between the resistance indexes and the heavy metal contents were analyzed to compare the two plants abilities to accumulate heavy metal and their resistance characteristics. The results indicated that the heavy metal concentrations had the following significant trend: urban areas > suburban areas > rural areas. In urban areas, the Mn, Zn, and Pb concentrations in C. deodara were as high as 2024.77 mg·kg^? 1, 2397.07 mg·kg^? 1, and 130.07 mg·kg^? 1, significantly higher than in S. chinensis. The Mn, Zn, and Pb concentrations in C. deodara were extremely significantly positively correlated (P < 0.01), but no significant correlations were noted in S. chinensis. The MDA, soluble sugar, and free proline concentrations in C. deodara increased as the heavy metal contents rose along the urban–rural gradient, and were positively correlated with the plant heavy metal contents. They were much higher than the contents in S. chinensis where no differences were noted among the sampling sites. In conclusion, the heavy metal resistance methods used by C. deodara and S. chinensis are different. C. deodara could absorb and accumulate many heavy metals, mainly through increased physiological resistance to stress. In contrast, S. chinensis resistance relied on avoiding contact with the metals and by reducing absorption. These differences are associated with the biological characteristics of C. deodara and S. chinensis, and are closely connected with their coniferous and morphological differences.     

Bioaccumulation of heavy elements by Armadillidium vulgare (Crustacea,Isopoda) exposed to fallout of a municipal solid waste landfill

This paper reports the response of isopods exposed to fallout of a municipal solid waste landfill located in central Italy. Soil samples and specimens of Armadillidium vulgare were collected at different distances from the landfill and analyzed to determine the concentrations of heavy elements such as As, Cd, Co, Cr, Cu, Ni, Pb, Sb, V and Zn. The isopod analysis was performed on unpurged and purged specimens. Analytical data indicate that the soil contents of heavy elements were quite uniform and within the respective local geochemical background. Slight enrichments of Cu and Pb were found in some soils collected within the solid waste. Purged isopods showed an accumulation of As, Co, Cr, Ni, Sb and V whose body levels decreased as the distance from the landfill increased. Cd, Cu, Pb and Zn concentrations in purged specimens were rather uniform and no significant variation trend occurred. This result probably was due to the fact that the isopods are provided with physiological mechanisms of regulation for these heavy elements. Analytical data also indicate the ability of A. vulgare to adsorb differently the heavy elements according to the following order: As > Co > Ni > Pb > V. The contents of heavy elements in unpurged specimens were higher than in purged ones. This finding suggested that the defecation has marked effects on the tissue levels of heavy elements in isopods. This study indicates that the isopods provide useful information about environmental quality in areas characterized by low and discontinuous emission of heavy elements and their low accumulation in soil.     

Heavy metal pollution in surface water and sediment: A preliminary assessment of an urban river in a developing country

The concentration and chemical fractionation of globally alarming six heavy metals (Cr, Ni, Cu, As, Cd and Pb) were measured in surface water and sediment of an urban river in Bangladesh. The decreasing trend of metals were observed in water as Cr > Cu > As > Ni > Pb > Cd and in sediment as Cr > Ni > Cu > Pb > As > Cd. The level of studied metals exceeded the safe limits of drinking water, indicated that water from this river is not safe for drinking and/or cooking purposes. However, the investigated metals showed low mobility except for Cd and Pb which could pose a severe threat to the aquatic environment. Contamination factor (CF) and geoaccumulation index (I_geo) demonstrated that most of the sediment samples were moderately to heavily contaminated by Cr, As, Cd and Pb. The pollution load index (PLI) values were above one (>1) indicates progressive deterioration of the sediment quality. The extent of pollution by heavy metals in the river Korotoa implies that the condition is much frightening to the biota and inhabitants in the vicinity of the river as well.     

Pollution characteristics and ecological risk assessment of heavy metals in the surface sediments from a source water reservoir

Surface sediment samples were collected from a source water reservoir in Zhejiang Province, East of China to investigate pollution characteristics and potential ecological risk of heavy metals. The BCR sequential extraction method was used to determine the four chemical fractions of heavy metals such as acid soluble, easily reducible, easily oxidizable and residual fractions. The heavy metals pollution and potential ecological risk were evaluated systematically using geoaccumulation index (I_geo) and Hakanson potential ecological risk index (H′). The results showed that the sampling sites from the estuaries of tributary flowing through downtowns and heavy industrial parks showed significantly (p < 0.05) higher average concentrations of heavy metals in the surface sediments, as compared to the other sampling sites. Chemical fractionation showed that Mn existed mainly in acid extractable fraction, Cu and Pb were mainly in reducible fraction, and As existed mainly in residual fraction in the surface sediments despite sampling sites. The sampling sites from the estuary of tributary flowing through downtown showed significantly (p < 0.05) higher proportions of acid extractable and reducible fractions than the other sampling sites, which would pose a potential toxic risk to aquatic organisms as well as a potential threat to drinking water safety. As, Pb, Ni and Cu were at relatively high potential ecological risk with high I_geo values for some sampling locations. Hakanson potential ecological risk index (H′) showed the surface sediments from the tributary estuaries with high population density and rapid industrial development showed significantly (p < 0.05) higher heavy metal pollution levels and potential ecological risk in the surface sediments, as compared to the other sampling sites.     

Genetic Variations of GWAS-Identified Genes and Neuroblastoma Susceptibility: a Replication Study in Southern Chinese Children

Neuroblastoma is one of the most commonly diagnosed solid cancers for children, and genetic factors may play a critical role in neuroblastoma development. Previous genome-wide association studies (GWASs) have identified nine genes associated with neuroblastoma susceptibility in Caucasians. To determine whether genetic variations in these genes are also associated with neuroblastoma susceptibility in Southern Chinese children, we genotyped 25 polymorphisms within these genes by the TaqMan method in 256 cases and 531 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of the associations. We performed a meta-analysis to further evaluate the associations. Furthermore, we calculated the area under the receiver-operating characteristic curves (AUC) to assess which gene/genes may better predict neuroblastoma risk. We confirmed that CASC15 rs6939340 A > G, rs4712653 T > C, rs9295536 C > A, LIN28B rs221634 A > T, and LMO1 rs110419 A > G were associated with significantly altered neuroblastoma susceptibility. We also confirmed that rs6939340 A > G (G versus A: OR = 1.30, 95% CI = 1.13-1.50) and rs110419 G > A (A versus G: OR = 1.37, 95% CI = 1.19-1.58) were associated with increased neuroblastoma risk for all subjects. We also found that the combination of polymorphisms in CASC15, LIN28B, and LMO1 may be used to predict neuroblastoma risk (AUC = 0.63, 95% CI = 0.59-0.67). Overall, we verified five GWAS-identified polymorphisms that were associated with neuroblastoma susceptibility alteration for Southern Chinese population; however, these results need further validation in studies with larger sample sizes.     

Geochemical baseline determination and pollution assessment of heavy metals in urban soils of Karachi,Pakistan

Karachi is one of the most populated urban agglomerations in the world. No categorical study has yet discussed the geochemical baseline concentrations of metals in the urban soil of Karachi. The main objectives of this study were to establish geochemical baseline values and to assess the pollution status of different heavy metals. Geochemical baseline concentrations of heavy metals were estimated using the cumulative frequency distribution (CDF) curves. The estimated baseline concentrations of Pb, Cr, Cu, Zn and Fe were 56.23, 12.9, 36.31, 123.03 and 11,776 mg kg⁻¹, respectively. The pollution status of heavy metals in urban soils was evaluated using different quantitative indices (enrichment factor–EF, Geo-accumulation Index–I_geo, and pollution index–PI). Enrichments factors of the selected heavy metals determined by using Fe as a normalizer showed that metal contamination was the product of anthropogenic activities. The urban soils of Karachi were found to have a moderate to moderately severe enrichment with Pb, whereas Cr and Cu has moderate and Zn has minor enrichment. I_geo results indicated moderate soil contamination by Pb at some of the sampling locations. PI for Pb, Cr, Cu and Zn was found in the range of 0.04–3.42, 0.19–1.55, 0.27–2.45 and 0.32–1.57, respectively. Large variations in PI values of Pb revealed that soil in those areas of the city which are influenced by intensive anthropogenic activities have exceptionally high concentrations of Pb. The findings of this study would contribute to the environmental database of the soil of the region and would also facilitate both at the local and the international scales, in a more accurate global environmental monitoring, which will eventually facilitate the development of management and remediation strategies for heavy metal contaminated urban soil.     

Myriophyllum aquaticum as a biomonitor of water heavy metal input related to agricultural activities in the Xanaes River (Córdoba,Argentina)

The aim of the present study was to assess the temporal variation of the heavy metal content (Co, Cu, Fe, Mn, Ni, Pb, and Zn) in surface water and sediments in relation to agricultural practices in the Xanaes River (Córdoba, Argentina). A second objective was to analyze possible relationships between the input of heavy metals on surface water and sediment, heavy metal accumulation and physiological changes in the aquatic plant Myriophyllum aquaticum. Samples were taken from the river at two contrasting sites (between April 2010 and August 2010): (1) a pristine area (mountain site), and (2) an area with intensive agricultural activity located at 60 km down river (agricultural site). The total concentration of heavy metals in surface water was higher in samples collected at the agricultural site but in sediments only the Mn concentration was higher than at the mountain site. The Fe and Mn concentrations in surface water at the agricultural site exceeded the recommended values for Argentinean Legislation of 300 μg L⁻¹ for Fe and 100 μg L⁻¹ for Mn. The accumulations of Zn and Mn in M. aquaticum were higher at the agricultural site and more elevated than the Zn and Mn concentrations in sediments at the same sites and sampling times. At the agricultural site, temporal variations of Cu, Fe and Zn were relatively similar for plants and water column, but the levels of the metals in plants were displaced over time. These results suggest that the levels of pollutants in the river came in pulses from the riverbank. These results show the potential use of M. aquaticum as a suitable accumulation biomonitor at the early stages of heavy metal pollution in rivers.     

Removal of nutrients and heavy metals from wastewater with mangrove Sonneratia apetala Buch-Ham

Mangrove wetlands are important in the removal of nutrients, heavy metals, and organic pollutants from wastewater within estuarine systems due to the presence of oxidized and reduced conditions, periodic flooding by incoming and outgoing tides, and high clay and organic matter content. This study investigated the removal efficiency of nutrients and heavy metals from wastewater by the mangrove Sonneratia apetala Buch-Ham in a simulated wetland. Eight different treatments, namely, three concentration levels of wastewaters, with and without planting of the mangrove species, and one control (with salted water) each for both with and without planting of the mangrove species, were employed in this study. Results showed that the amounts of total mangrove biomass from different treatments were in the following order: PL-TW (planted with ten times higher-than-normal wastewater concentration) > PL-FW (planted with five times higher-than-normal wastewater concentration) > PL-SW (planted with normal wastewater concentration) > PL-NW (planted with no wastewater), whereas the magnitude of the heavy metal contents in the biomass was in the following order: Cu > Pb > Cd > Zn. Very good linear correlations existed between the biomass and the nutrients or heavy metals. The Sonneratia apetala Buch-Ham species had its own selectivity for uptake of heavy metals regardless of the initial heavy metal contents and was more effective in the removal of nutrients than heavy metals. Our study suggested that mangrove wetlands with Sonneratia apetala Buch-Ham species had great potential for the removal of nutrients and heavy metals in coastal areas.     

Distribution of Metals (Cu,Zn, Pb,and Cd) in Sediments of the Anzali Lagoon,North Iran

Concentrations of four metals (Cu, Zn, Pb, and Cd) in the sediments of the Anzali Lagoon in the northern part of Iran were determined to evaluate the level of contamination and spatial distribution. The sediments were collected from 21 locations in the lagoon. At each lagoon site a core, 60 cm long, was taken. The ranges of the measured concentrations in the sediments are as follows: 17–140 mg kg^?1 for Cu, 20–113 mg kg^?1 for Zn, 1–37 mg kg^?1 for Pb and 0.1–3.5 mg kg^?1 for Cd in surficial (0-20 cm) and 16–87 mg kg^?1 for Cu, 28.5–118 mg kg^?1 for Zn, 3–20 mg kg^?1 for Pb and 0.1–3.5 mg kg^?1 for Cd in deep (40–60 cm) sediments. The results of the geoaccumulation index (I_geo) show that Cd causes moderate to heavy pollution in most of the study area. Environmental risk evaluation showed that the pollution in the Anzali Lagoon is moderate to considerable and the ranking of the contaminants followed the order: Cd > Cu > Pb > Zn. Some locations present severe pollution by metals depending on the sources, of which sewage outlets and phosphate fertilizers are the main sources of contaminants to the area.     

Morphological variations,biomass and ion accumulation of the aboveground shoots of Desmostachya bipinnata (L.) Stapf

The present study aimed to evaluate the morphological characteristics and biomass of Desmostachya bipinnata and their relation to the environmental variables in three main habitats (canal banks, railway and roadside shoulders) where it is found in Egypt. In addition, the ability of this plant is evaluated to accumulate nutrients and heavy metals in its aboveground shoots. Twenty five quadrats (1 m × 1 m per quadrat) were selected along five sites representing the different habitats of D. bipinnata for this study. The aboveground shoots displayed considerable morphological variations, differing in the different habitats. The above ground biomass, number of spikes and leaves, rachis length and diameter, leaf length, width and area, leaf sheath length, and spike length and diameter were in the order: road sides > canal banks > railway shoulders. A regression equation: biomass = (67.37 × density) + 108.2, was used to estimate the shoot biomass from the plant growth density. Metal uptake capability from soil to grass is in the order Fe > Zn > Cu > Mn, and all of them are in safe concentration ranges. These heavy metals had a transfer factor more than unity, which indicates that D. bipinnata is a powerful accumulator for heavy metals. In addition, the plant shoots exhibit high accumulation of inorganic and organic nutrients.     

From water to edible fish. Transfer of metals and metalloids in the San Roque Reservoir (Córdoba,Argentina). Implications associated with fish consumption

The concentration of Mn, Fe, Zn, Cu, Cd, Cr, Ni, Ag, Mo, Nd, Al, Ce, As, Sr, Pb, Pt and Hg was analysed in water, sediments, and aquatic organisms from the San Roque Reservoir (Córdoba-Argentina), sampled during the wet and dry season, to evaluate their transfer through the food web. Stable nitrogen (δ¹⁵N) isotopes were used to investigate trophic interactions. According to this, samples were divided into three trophic groups: plankton, shrimp (Palaemonetes argentinus) and fish (Silverside, Odontesthes bonariensis). Liver and gills are the main heavy metal storage tissues in fish. Hg and As concentrations in the muscle of O. bonariensis exceed the Oral Reference doses for metals established by USEPA (2009). Trophic magnification factors (TMFs) for each element were determined from the slope of the regression between trace element concentrations and δ¹⁵N. Calculated TMFs showed fundamental differences in the trophodynamics of the studied elements during the wet and dry season in the San Roque Reservoir. Concentrations of Ni, Cd, Cr, Al, Mn, Fe, Mo, Ce, Nd, Pt and Pb during both seasons, and Sr during the dry season, showed statistically significant decreases (TMF < 1) with increasing trophic levels. Thus these elements were trophically diluted in the San Roque food chain. Conversely, Cu, Ag and As (dry season) showed no significant relationships with trophic levels. Among the elements studied, Hg in the wet season, and Zn in the dry season were the only ones showing a statistically significant increase (TMF > 1) in concentration with trophic level. Current results trigger the need for further studies to establish differential behaviour with different species within the aquatic web, particularly when evaluating the transfer of toxic elements to edible organisms, which could pose health risks to humans.     

Activation and ecological risk assessment of heavy metals in dumping sites of Dabaoshan mine,Guangdong province,China

In Dabaoshan mine, dumping sites were the largest pollution source to the local environment. This study analyzed the activation and ecological risk of heavy metals in waste materials from five dumping sites. Results indicated that the acidification of waste materials was severe at all dumping sites, and pH decreased below 3.0 at four of the five sites. There was a drastic variation in Cu, Zn, Pb, and Cd concentrations in different sites. Site A with 12915.3 mg kg^?1 Pb and 7.2 mg kg^?1 Cd and site C with 1936.2 mg kg^?1 Cu and 5069.0 mg kg^?1 Zn were severely polluted. Higher concentrations of water-soluble Cu were probably the critical constraint for local pioneer plants. A significant positive correlation was found between the concentrations of water-soluble and HOAc-extractable elements, and the regression analysis showed that, compared with Cu, Zn and Cd, Pb was more difficult to be transformed from HOAc extractable to water soluble. Concentration of water soluble metals should be an important index, same as concentration of HOAc extractable metals, in assessing ecological risks, availability, and toxicity of heavy metals. The modified ecological risk index indicated that all dumping sites had very high potential ecological risks. It is necessary to decrease the availability of heavy metals to reduce the impact of waste materials on environment.     

Effect of the presence of lead on the biosorption of copper,cadmium and nickel by anaerobic biomass

Heavy metals are toxic pollutants released into the environment as a result of industrial, mining and agricultural activities. The biosorption of Pb, Cu, Cd, and Ni from single and binary metal systems were studied in equilibrium systems and in a flow-through column packed with a calcium-saturated anaerobic sludge biosorbent, respectively. The single-metal sorption uptake capacity of the biomass for Pb was slightly inhibited by the presence of Cu and Cd cations (by 6%) and by the presence of nickel (by 11%). The affinity order of anaerobic biomass for the four metals was established as: Pb > Cu > Ni > Cd. Factors such as hydration effects, hydrolysis effects and covalent binding of the metal ions may contribute to this result. By studying the breakthrough curves obtained from a fixed bed column fed with an equimolar mixture of Pb, Cd, Cu, and Ni, it was determined that lead was the last metal to break through the column at the 150 bed volume mark compared to 4, 15, 30 bed volume marks for Ni, Cd, and Cu, respectively.     

Metal uptake by medicinal plant species grown in soils contaminated by a smelter

The hypothesis tested in this study was if medicinal plants could be grown as alternative crops in heavy metal polluted soils without contamination of the final marketable produce. Furthermore, medicinal crops may offer a phytoremediation option for mildly heavy metal polluted agricultural soils. The effect of metal-enriched soils was evaluated in five medicinal species (Bidens tripartita L., Leonurus cardiaca L., Marrubium vulgare L., Melissa officinalis L. and Origanum heracleoticum L.). Soils were sampled in the vicinities of the Non-Ferrous Metals Combine (Pb–Zn smelter) near Plovdiv, Bulgaria, from plots at 0.5 km (soil 1), 3 km (soil 2), 6 km (soil 3) and 9 km (control soil) from the smelter. Cadmium, Pb and Zn concentration in soil 1 were above the critical total (HNO₃-extractable) concentrations for these elements in soils. Generally, heavy metals in soil 1 decreased dry mater yields of the five species relative to the control. However, the essential oil content of M. vulgare, M. officinalis and O. heracleoticum was within the usual range for respective species and was not affected by the treatments. The overall metal uptake was in the order: B. tripartita > M. vulgare > O. heracleoticum > L. cardiaca > M. officinalis for Cd, L. cardiaca = M. vulgare > B. tripartita = M. officinalis = O. heracleoticum for Pb, L. cardiaca = M. vulgare > O. heracleoticum > B. tripartita = M. officinalis for Cu and B. tripartita > L. cardiaca = M. vulgare > M. officinalis = O. heracleoticum for Mn and Zn. Overall, metal concentration in plant parts was in the order: roots > leaves > flowers > stems for Cd, Pb and Cu, leaves > roots > flowers > stems for Mn and Zn. The concentration of Cd, Pb, Cu and Zn in plant tissue correlated to the exchangeable (EXCH) and the carbonate (CARB) bound fractions of metals in soil. Heavy metals caused disruptions of the plasma membrane of some root cortical cells and alterations in chloroplasts thylakoids in plants grown in soil 1. Metal content in teas prepared from the species was negligible, the essential oils were free of metals. Generally, the transfer factor (TF) was less than 1, indicating the tested species did not have a significant phytoextraction potential. This study demonstrated the three essential oil species M. vulgare, M. officinalis and O. heracleoticum can be grown as alternative high-value crops in metal polluted agricultural soils around the smelter and provide metal-free marketable produce.     

Distribution and risk assessment of heavy metals in river surface sediments of middle reach of Xijiang River basin,China

Xijiang River is the main surface water source in Guangxi province, South China. This study was carried out to investigate the distribution and potential ecological risks of seven heavy metals (Cu, Pb, Zn, As, Cd, Ni, and Cr) in surface sediments in Xijiang River basin. The results illustrated that the average concentrations of Zn, Pb, Cd, Cu, As, Ni, and Cr were 483.9, 207.5, 13.35, 23.50, 312.1, 28.75, and 50.62 mg/kg, respectively. Among them, Zn, Pb, Cd, and As were the major heave metals with concentration exceeding Class 3 threshold value of Chinese national standard. The result also showed samples with high ecological risk were mainly located in the upstream of Xijiang River basin as Diaojiang River, Hongshui River, Jincheng River, and Dahuan River. Based on the pollution risk assessment, the area manifested composite pollution of heavy metals in the sediments, signifying As, Pb, and Cd as the dominant heavy metals, and there were high ecological risk in sediments for these metals. According to correlation matrix and factor analysis (FA), the seven heavy metals were divided into three types/classes, Cd, as and Zn attributed by anthropogenic sources, natural sources corresponds for Ni and Cr while both natural and anthropogenic sources were attributed to Cu.     

Assessment of heavy metal pollution and ecological risk in marine sediments (A case study: Persian Gulf)

This study was made to determine the pollution status and potential ecological risk of heavy metals in sediment of Persian Gulf. Surface sediments were collected seasonally by Peterson grab, and the concentrations of heavy metals were measured by using inductively coupled plasma–optical emission spectrometry (ICP–OES). The range concentrations obtained in mg/kg were 10,800–22,400 for Fe, 5.32–10.12 for Pb, 24.63–42.38 for Ni, 22.52–39.46 for Cu, and 31.64–47.20 for Cr. The concentrations of Pb, Ni, Cu, and Cr have been found lower than the Interim Sediment Quality Guidelines and probable effect level values suggesting that heavy metal contents in sediments from area of study would not be expected to cause adverse biological effects on the biota. The obtained enrichment factor values for various metals were between minimal enrichment (Pb = 0.5) and extremely enrichment (Cu = 3.11). The values of I_geo for Pb, Ni, Cu, and Cr were characterized under no pollution (0). The highest value of potential ecological risk index (RI) (8.36) was observed at St. 4 while the lowest value (5.25) was detected at station 6. Based on potential ecological RI, the Persian Gulf had low ecological risk.     

Seasonal variations in the body composition and bioaccumulation of heavy metals in Nile tilapia collected from drainage canals in Al-Ahsa,Saudi Arabia

The body composition of Nile tilapia (Oreochromis niloticus) collected from drainage canals in Al-Ahsa, Saudi Arabia and the concentration of four heavy metals; zinc (Zn), cadmium (Cd), cobalt (Co) and lead (Pb) in both fish muscles and the water collected from this environment were assessed across the four seasons. The body composition was found to change with the seasons, with the best body composition being recorded in autumn and winter, where higher levels of protein (17.24, 17.65%), and fat (0.58, 0.71%) and lower water content (80.15, 79.86%) respectively were noted. The concentration of heavy metals in both fish muscles and the water body also varied significantly with the seasons. In the fish muscles, the highest content of Zn (0.409 mg/kg dry weight) and Cd (4.140 mg/kg dry weight) was recorded in winter, however, the highest concentration of Co (0.318 mg/kg dry weight) and Pb (1.96 mg/kg dry weight) was observed in spring and summer respectively. On the other hand, the water samples collected in autumn showed the maximum concentration of Cd (1.385 mg/L), Co (0.762 mg/L) and Pb (0.18 mg/L) however, the maximum concentration of Zn (0.0041 mg/L) was recorded in winter. With the exception of Cd, the accumulation of the studied heavy metals in fish muscles was within the safe limits for seafood recommended by various organizations.