Heavy metals (As,Cr, Pb,Cd and Ni) concentrations in rice (Oryza sativa) from Iran and associated risk assessment: a systematic review

Rice (Oryza sativa) is the second cereal consumed in Iran. Many studies have been carried out in Iran about the contamination of rice by environmental pollutants such as heavy metals. The aim of present study was:

??to systematically review about Arsenic (As), Chromium (Cr), Lead (Pb), Cadmium (Cd) and Nickel (Ni) concentrations in cultivated rice in Iran and;

??to estimate the non-carcinogenic risk for age and sex groups.

We applied the target hazard quotient (THQ) and total target hazard quotient (TTHQ) to evaluation of the non-carcinogenic risk. International and Iranian databases were searched from January 2008 to October 2016. Data obtained from 27 articles showed that minimum and maximum concentrations of heavy metals were As (0.05?±?0.09?μg/g dry weight) and Ni (0.83?±?0.04?μg/g dry weight), respectively. The rank order of heavy metals based on THQ was As?>?Cr?>?Pb?>?Cd?>?Ni. Also the rank order of consumers rice based on TTHQ were rural females (0.49)?>?urban females (0.461)?>?rural males (0.455)?>?urban males (0.41). Minimum and maximum of TTHQ was related to 35–44 and 15–24 years age groups both males and females, respectively. Since THQ and TTHQ were either lower than 1 value, therefore, consumers were not exposed to carcinogenic risk by consumption of rice cultivated in Iran.     

Potential risk assessment of trace metals accumulation in food,water and edible tissue of rainbow trout (Oncorhynchus mykiss) farmed in Haraz River,northern Iran

This study focuses on the extent of Zn, Cu, Ni, Cd and Pb bioaccumulation in water, fish feed and the muscles of 40 rainbow trout (Oncorhynchus mykiss) from four farmsalong Haraz River, Mazandaran Province, north of Iran. The dependence of bioaccumulation with food chain and environmental heavy metals concentration was specifically addressed. The potential human health risks due to consumption of rainbow trout have been assessed by estimated daily intake (EDI) and target hazard quotient (THQ) of aforementioned metals. The detected concentration ranges of the elements in the muscles, reported as μg.g^?1?dry weight, were as following: Zn (13.92–15.92), Cu (0.54–0.74), Ni (0.12–0.26), Cd (0.008–0.01) and Pb (0.25–0.57). The rank order of the levels of the heavy metals was: in edible tissue Zn?>?Cu?>?Pb?>?Ni?>?Cd; in water Pb?>?Zn?>?Cu?>?Ni?>?Cd; in fish feed Pb?>?Zn?>?Ni?>?Cu?>?Cd. In general, the concentrations of all target metals were positively correlated with fish feed contents, whereas negative correlations were observed between the metal concentrations and water. Risk assessments suggested that there isn’t potential ecological and human health risk.     

Non-carcinogenic risk assessment induced by heavy metals content of the bottled water in Iran

Recently, the exposure to heavy metals from bottled waters raised huge concerns. In this context, for the first time the risk of non-carcinogenic exposure by the heavy metals in Iranian drinking water was assessed. Therefore, by using the obtained data in our previous published study, the target hazard quotient (THQ) and total target hazard quotient (TTHQ) by considering to the sexuality of consumers were calculated. THQ in females were determined as significantly higher (p??Pb?>?Hg?>?Cd?>?Cu, respectively. The minimum and maximum of THQ for the males were observed in age groups of?+65 and 1–3?years, respectively. The minimum and maximum of THQ for females were noted in age groups of 11–14 and 1–3?years, respectively. Since TTHQ for all ages were less than 1 (p?相似文献   

Heavy metal concentration in muscle of pike (Esox lucius Linnaeus, 1758) from Anzali international wetland,southwest of the Caspian Sea and their consumption risk assessment

This study evaluated the concentrations of nine heavy metals in muscle specimens of pike (Esox lucius Linnaeus, 1758) from four sites of southwest of the Caspian Sea: Shijan, Abkenar, Hendakhale and Siakeshim. The potential human health risks due to consumption of pike have been assessed by estimated average daily intake (EDI) and target hazard quotient (THQ) of metals. In particular, Cu, Zn, Cd, Pb, Hg, As, Ni, Co and Mn were quantified in the edible tissue of specimens by AAS determination. The average metal concentrations of Cu, Zn, Cd, Pb, Hg, As, Ni, Co and Mn measured in this study were 1.12?±?0.264, 5.37?±?0.702, 0.058?±?0.023, 0.20?±?0.035, 0.005?±?0.002, 0.17?±?0.047, 0.33?±?0.062, 0.28?±?0.034 and 0.20?±?0.035?μg/g w wt, respectively. Our results demonstrate the consumption of muscle of pike for adult and children as less than 1, hence residents of these regions will not be exposed to significant health risks.     

Trace element concentration and its risk assessment in common kilka (Clupeonella cultriventris caspia Bordin, 1904) from southern basin of Caspian Sea

This study evaluated the extent of metal levels of zinc (Zn), copper (Cu), manganese (Mn), chromium (Cr), nickel (Ni), lead (Pb), cadmium (Cd), and mercury (Hg) in edible muscles of common kilka at Babolsar and Amirabad coastal regions from the southern basin of Caspian Sea. These values were compared with the WHO and the UNFAO safety standards regarding the amount of the abovementioned heavy metals in fish tissues (mg/kg w.w.). Results showed that Zn concentrations were highest among the trace elements examined, while concentrations of Hg were generally the lowest in the analyzed tissues. In the other hand, the accumulation of these elements was not significantly different between coastal regions (p?>?0.05). While accumulation of Cu and Mn at edible muscles of Clupeonella cultriventris were significant difference between two coastal regions (p??Cu?>?Cr?>?Cd?>?Ni?>?Mn?>?Pb?>?Hg. Furthermore, Pearson correlation revealed that Zn, Cu, Mn, Ni, Cr, Pb, Cd and Hg in edible muscles of C. cultriventris were not significantly correlated in length (R^2?<^?0.50; p?>?0.05), but it was significantly correlated in weight (p?C. cultriventris consumption.     

Assessment of bioavailability and human health exposure risk to heavy metals in surface soils (Klang district,Malaysia)

In urban area surface soil the heavy metal concentrations followed the order: Pb (76.15?mg/kg) >?Fe (12.96?mg/kg)?>?Cu (11.58?mg/kg)?>?Al (10.3?mg/kg)?>?Zn (6.42?mg/kg)?>?Co (0.21?mg/kg) >?Cd (0.18?mg/kg)?>?Cr (0.07?mg/kg). For the industrial area surface soil, heavy metal concentrations followed the sequence: Pb (55.28?mg/kg)?>?Al (15.5?mg/kg)?>?Fe (14.73?mg/kg)>?Cu (14.68?mg/kg) >?Zn (4.48?mg/kg) >?Co (0.26?mg/kg) >?Cr (0.11?mg/kg)?>?Cd (0.11?mg/kg). PCA output showed that the first and second principal components are attributed due to the presence of “urban metals” in the urban areas while third principal component reflects the anthropogenic factor in the industrial areas. Total Cancer Risk values are more than the incremental lifetime (1.0E???05), showing the likelihood of a cancer threat for adults and children. For non-carcinogenic risks, Hazard Index values <1 one indicating no potential risks.     

Evaluation of trace metals concentration and human health implication by indigenous edible fish species consumption from Meghna River in Bangladesh

This study is focused on the determination of trace metals (Cr, Cu, Zn, As, Pb, and Cd) concentrations of nine different indigenous fish species of Meghna River in Bangladesh to know the possible risk in human consumption. Fishes' wet muscles samples were analyzed to evaluate the level of trace metal concentrations. The concentrations (mg kg⁻¹ w/w) of the six selected trace metals were in the order Zn (1.42 ± 0.12) > Cr (1.31 ± 0.08) > Cu (0.92 ± 0.09) > Pb (0.54 ± 0.07) > Cd (0.51 ± 0.07) > As (0.47 ± 0.02). The results revealed that all the selected trace metals were below the maximum permissible limits recommended by the reference standards. The fish species may pose no risk with respect to the Estimated Daily Intake (EDI). Target hazard quotient (THQ) values for Cr, Cu, Zn, Pb, and Cd in all the fish species were <1.0, except for As which is dominantly organic in fishes. Both adults and children are vulnerable to carcinogenic health threat due to Cd exposure.     

Distribution and ecological assessment of heavy metals in surface sediments of the East Lake, China

Concentrations and risk assessment of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd) and mercury (Hg) were investigated in 106 samples of surface sediments from the East Lake, China in this study. The mean concentration of Zn was highest among the eight heavy metals (225 mg kg^?1), followed by As (191 mg kg^?1), Cr (145 mg kg^?1), Cu (55 mg kg^?1), Ni (27.1 mg kg^?1), Pb (7.93 mg kg^?1), Cd (0.94 mg kg^?1) and Hg (0.21 mg kg^?1). Niuchao Hu was less polluted by heavy metals compare to the other four lakelets of the East Lake. The correlations among these heavy metals and the results of principal component analysis indicated that the distribution of Cd, Pb and Hg was related to anthropogenic activities, whereas Cu, As and Cr were affected by the parent rocks. Zinc and Ni were influenced both by anthropogenic activities and parent rocks. Based on the Sediment Quality Guidelines, the results of toxicity assessment indicated that adverse effects caused by Cr and As would be expected frequently. Nickel, Zn, Cd and Hg may cause adverse effects occasionally and Cu and Pb may cause toxicity infrequently. Arsenic was found to have the highest acute toxicity by toxic units (TUs), followed by Cr, Ni, Zn, Hg, Cu, Cd and Pb. The potential ecological risk index analysis indicated that As, Cd and Hg had considerable or high ecological risk, whereas Cr, Ni, Cu, Zn and Pb had low ecological risk. The potential ecological risk index (RI) of the heavy metals in the surface sediments of East Lake was 483, indicating considerable ecological risk. Close attention should be paid to pollution of the heavy metals in East Lake, China.     

Risk assessment of heavy metals bioaccumulation: fished shrimps from the Persian Gulf

Although, several benefits can be offered by the consumption of marine products, the heavy metals bioaccumulation inside of their body can put the health of consumers at a high level of risk. In this context, however, the Persian Gulf contentedly is polluted by waste water, solid waste and petroleum activities residues, due to an increasing trend in consumption of fished aquatic organisms such as fish and shrimp, the safety of marine products is a source of concern. The current review was established in order tracing the metals concentrations in the muscle of fished shrimps from the Persian Gulf as well as conducting the health risk assessment. The reviewed literature was based on the internal and external databases. According to the results of 23 studies, the maximum and minimum heavy metals concentrations were determined as Zn (8.56?±?34.68?μg/g) and Hg (0.08?±?0.04?μg/g), respectively. Moreover, the heavy metal levels in the 32.5% of studies were higher than premiered limit by the WHO/FDA guidelines. Based on the calculated median for heavy metals concentrations, Total target hazard quotient (TTHQ) for the adults and children were reported as 0.466 and 0.311, respectively. The order of the concentration of the heavy metals can be demonstrated as following: Co?>?As?>?Cd?>?Pb?>?Cu?>?Zn?>?Mn?>?Ni?>?Hg?>?Cr. Considering the results of risk assessment, no potential human health risk for the consumer's shrimps of the Persian Gulf was observed.

Research highlights

• Maximum and minimum of heavy metals concentrations in the shrimps were determined as Zn and Hg, respectively, in the Bushehr, Khuzestan, Bandar Abbas, Qeshm Island, Kuwait and Qatar.

• Total target hazard quotient for the adults and children were less than 1 value.

• Overall, potential health risk of heavy metals does not threaten consumer’s heath.

     

Study of heavy metal levels in indoor dust and their health risk assessment in children of Ahvaz city,Iran

The concentration of heavy metals in household dust and their health risks on children living in different areas of Ahvaz city was investigated during November 2013 to October 2014 in Iran. Totally, 108 dust samples were taken from their houses in three different areas including S₁ (industrial), S₂ (heavy traffic) and S₃ (residential zone far away from industrial and traffic emission sources). The samples were analyzed for eight selected heavy metals (Cr, Ni, Cu, Mn, Pb, Zn, Co and Cd) using an inductively coupled plasma optical emission spectroscopy (ICP-OES, Spectro Arcos Model, Germany). Exposure and risk assessment of these metals were estimated using USEPA’s exposure parameters. Results showed that the mean values of all heavy metals in tempered months were significantly higher than the other months (p?<?0.05). Cancer risk and non-carcinogenic risk (hazard index) of Ni, Cr, Cd and Pb from indoor dust exposure were estimated for children via three exposure pathways (ingestion, inhalation and dermal contact). The non-cancer risks to children in all samples were lower than acceptable level of 1, while the potential cancer risks from Ni intake in S₁ and S₂ were 1.57E???06 and 1.19E???06, respectively, and for Cr in S₁ and S₂, it was 1.43E???06 and 1.15E???06, respectively, which these values were slightly higher than the acceptable level (1?×?10^?6). In conclusion, household dust of Ahvaz city would probably have a significant potential to cause cancer in most exposed children.     

Potential human health risks from metals (Hg, Cd, and Pb) and polychlorinated biphenyls (PCBs) via seafood consumption: Estimation of target hazard quotients (THQs) and toxic equivalents (TEQs)

Edible marine species (fish, cephalopod molluscs, crustaceans) from the Adriatic Sea were analyzed for content in heavy metals (Hg, Cd and Pb) and polychlorinated biphenyls (PCBs). Health risks to human via dietary intake of seafood were assessed by the target hazard quotients (THQs) and the toxic equivalent factors (TEFs). Mercury maximum concentrations corresponded to fish (0.07-1.56 microg g(-1)w.w.), followed by cephalopod molluscs (0.10-0.55 microg g(-1)w.w.), and crustaceans (0.27-0.33 microg g(-1)w.w.). Cadmium levels in cephalopods (0.18-0.59 microg g(-1)w.w.) were higher than those in fish (0.01-0.05 microg g(-1)w.w.) and crustaceans (0.02-0.04 microg g(-1)w.w.), while for Pb the concentrations were generally low (fish: ND-1.18 microg g(-1)w.w., cephalopods: ND-0.17 microg g(-1)w.w., crustaceans: ND-0.03 microg g(-1)w.w.). For PCBs, concentrations in fish, cephalopods and crustaceans ranged between 141 and 3,406 ng g(-1)l.w., 190 and 542 ng g(-1)l.w., and 202 and 429 ng g(-1)l.w., respectively. Cd and Pb THQ values as well as estimates of PCB TEQ exposure indicated the absence of health risks through consumption of the various seafood. In contrast, mercury TEQs values due to consumption of certain fish species (albacore, rosefish and thornback ray) indicated that human health risk might be of concern.     

Health risk assessment of heavy metals in the water environment of Zhalong Wetland,China

Concentrations of the Cu, Cd, Cr, As, Zn and Ni in water samples from 272 sampling stations in the water environment of Zhalong Wetland, China were studied. Health risk assessment associated with six heavy metals and metalloid was conducted using health risk assessment model from United States Environmental Protection Agency. It can be concluded that the mean concentrations of Cu, Ni, Zn, As, Cd and Cu were 0.19, 0.45, 0.52, 4.9, 0.12 and 0.24 μg L^?1, respectively. The carcinogenic risk of Cr, As and Cd in the discharged area, experimental area, buffer area and core area were lower than the maximum allowance risk level recommended by International Commission on Radiological Protection (ICRP 5.0 × 10^?5 a^?1). The non-carcinogenic risks (Cu, Zn, Ni) was also lower than the maximum allowance levels recommended by ICRP. Though it was lower than the level, it was very approaching to maximum acceptable risk level, need to draw attention to the relevant departments.     

Metal bioaccumulation in selected tissues of barb (Barbus sp.) and common carp (Cyprinus carpio,Linnaeus 1758) from the Keban Dam Lake,Turkey

Abstract

The aquatic life has been negatively influenced by harmful effects of environmental toxic elements, including heavy metals. The elevated concentrations of metals may be harmful for aquatic animals and human health. Herein, the present study deals with assessment of the bioavailability of metals [cadmium (Cd), chrome (Cr), copper (Cu), zinc (Zn), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), and selenium (Se)] in organs such as muscle, gills, liver, kidney, and gonad of the commercially consumed Barbus sp. and Cyprinus carpio (Linnaeus, 1758) collected from Keban Dam Lake, eastern Turkey. The fish were captured from four different stations of Keban Dam Lake. Our results indicated that Fe and Zn concentrations were the highest in all tissues of two fish species while Cd concentrations were the lowest levels. In addition, detected metals accumulated in the muscle of common carp at higher levels compared to Barbus sp. The results from the present study also demonstrated significant variations and considerable differences in the concentrations of all 10 elements between the four stations and different fish tissues. Overall, the concentrations of detected metals in the muscle were many folds higher than the permissible level prescribed by some national and international legislation, which raises health risk concerns.     

Potential health risks due to heavy metal uptake via consumption of Thunnus thynnus from the northern Levantine Sea

The potential human health risks of copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) in Thunnus thynnus from the northern Levantine Sea were assessed. The mean concentrations (mg/kg) of metals were found as 0.819 for Cu, 8.344 for Zn, 2.102 for As, 0.002 for Cd, 0.001 for Hg and 0.115 for Pb. Even though these values were below the permitted levels, 11% of the samples contained Pb above the limits. Estimated weekly intakes were conspicuously lower than the PTWI values. The target hazard quotients (THQs) of each metal and total THQ of combined metals remained well below 1, showing no public health risk for an average consumer.     

Trace metal dynamics in zooplankton from the Bay of Bengal during summer monsoon

Trace metal (Fe, Co, Ni, Cu, Zn, Cd, and Pb) concentrations in zooplankton from the mixed layer were investigated at 8 coastal and 20 offshore stations in the western Bay of Bengal during the summer monsoon of 2003. The ecotoxicological importance of trace metal uptake was apparent within the Bay of Bengal zooplankton. There was a distinct spatial heterogeneity of metals, with highest concentrations in the upwelling zones of the southeast coast, moderate concentrations in the cyclonic eddy of the northeast coast, and lowest concentrations in the open ocean warm gyre regions. The average trace metal concentrations (μg g^?1) in coastal zooplankton (Fe, 44894.1 ± 12198.2; Co, 46.2 ± 4.6; Ni, 62.8 ± 6.5; Cu, 84.9 ± 6.7; Zn, 7546.8 ± 1051.7; Cd, 46.2 ± 5.6; Pb, 19.2 ± 2.6) were higher than in offshore zooplankton (Fe, 3423.4 ± 681.6; Co, 19.5 ± 3.81; Ni, 25.3 ± 7.3; Cu, 29.4 ± 4.2; Zn, 502.3 ± 124.3; Cd, 14.3 ± 2.9; Pb, 3.2 ± 2.0). A comparison of average trace metal concentrations in zooplankton from the Bay of Bengal showed enrichment of Fe, Co, Ni, Cu, Zn, Cd, and Pb in coastal zooplankton may be related to metal absorption from primary producers, and differences in metal concentrations in phytoplankton from coastal waters (upwelling zone and cyclonic eddy) compared with offshore waters (warm gyre). Zooplankton showed a great capacity for accumulations of trace metals, with average concentration factors of 4 867 929 ± 569 971, 246 757 ± 51 321, 337 180 ± 125 725, 43 480 ± 11 212, 1 046 371 ± 110 286, 601 679 ± 213 949, and 15 420 ± 9201 for Fe, Co, Ni, Cu, Zn, Cd, and Pb with respect to dissolved concentrations in coastal and offshore waters of the Bay of Bengal. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2009.     

Heavy metal bioaccumulation in different fish species in the coast of the Persian Gulf,Iran

This study project aimed to determine the concentrations of five heavy metals (Al, As, Cd, Hg and Pb) in different fish species in the coast of the Persian Gulf in Iran. Ninety samples divided to three types’ fish including Rastrelliger kanagurta, Tenualosa ilisha and Scomberomorus commerson. The investigation performed by ICP-OES technique. The estimated daily intake of heavy metals compared with allowable daily intake of these. Also, the means compared with the allowable limit regulated by national Iranian standards. Results showed that the heavy metal contamination of these was in the standard limit, except Pb in R. kanagurta (43.33%), T. ilisha (23.33%) and S. commerson (13.3%) had greater than European Union limit (300?μg L^?1). Therefore, monitoring of the heavy metals contents, specially Pb is very important yet because of the presence of these in soils due to increase of industrial activity and use pesticides and fertilizers.     

Antioxidant responses and metal accumulation in tissues of Nile tilapia Oreochromis niloticus under Zn,Cd and Zn + Cd exposures

We investigated the effects of Zn, Cd and a Zn + Cd mixture on antioxidant parameters and metal accumulation in Oreochromis niloticus. Fish were exposed to 0.5 and 5.0 mg l^?1 Zn, 0.1 and 1.0 mg l^?1 Cd, and 0.5 mg l^?1 Zn + 0.1 mg l^?1 Cd and 5.0 mg l^?1 Zn + 1.0 mg l^?1 Cd mixtures for 7 and 28 days to determine Zn and Cd accumulation, reduced glutathione (GSH) level and glucose‐6‐phosphate dehydrogenase (G6PD) activity in gill and liver. There was increasing accumulation of the metals in the tissues with increasing concentrations of metals in the exposure medium and with increasing duration of exposure (except at the lower concentration of Zn). Concentration of metals in the tissues of fish exposed to the Zn + Cd combination were significantly lower than in fish exposed to the single metal. The highest metal accumulation was observed in the liver. Exposure to the heavy metals affected the antioxidant parameters in the tissues, with both GSH level and G6PD activity in the gill and liver being increased under Zn, Cd and Zn + Cd exposures, especially in their higher concentrations. These increases in the antioxidant responses were higher with the Cd alone, and in combination with Zn, than with Zn alone. Furthermore, GSH level and G6PD activity increased with increasing exposure period only for Cd alone, and in Cd combination with Zn. The results indicate that O. niloticus resisted oxidative stress induced by heavy metal exposure by antioxidant mechanisms. Copyright © 2008 John Wiley & Sons, Ltd.     

Health risk assessment induced by chloroform content of the drinking water in Iran: systematic review

Long-term intake of water with high content of trihalomethanes (THMs) such as chloroform (CHCl₃) is hazardous for human health. Some studies have shown that clinical effects of THMs in drinking water may be yet observed to doses lower to standard limit. In our study, we performed a meta-analysis to assess both the mean concentration of CHCl₃ in Iranian drinking water and the relative health effects by long-term exposure to safe dose of CHCl₃ in the male and female age groups and in female categories. We applied the Target Hazard Quotient (THQ) for the evaluation of the noncarcinogenic risk of CHCl₃. Meta-analysis (14 studies) showed that the average concentration of CHCl₃ was 24?µg/l (95%CI:18.1–30.1?µg/l), I²?=?99.88, p?3 was related to Mashhad (3.5?±?0.5?µg/l) and Mazandaran (57.3?±?13.1?µg/l) province, respectively. The average concentration of CHCl₃ in the all studied provinces was lower than USEPA (70?µg/l) and national standard limits (200?µg/l). The minimum and maximum THQ was related to?<0.5 and 15–19?years age groups in both the males and females. The rank order of THQ in the female categories was females aging 15–44 (0.074)>?non-pregnant and non-lactating females age 4–15 (0.071)?>?pregnant (0.071)?>?lactating (0.043). The THQ in the females was higher than males, non-significantly (p?>.05). Except Mazandaran province, in other provinces both males and females, for all age groups, were not exposed to significant risks by non-carcinogenic exposure of CHCl₃ in drinking water (THQ <1).     

Heavy metal concentration in feathers of Little Egret (<Emphasis Type="Italic">Egretta garzetta</Emphasis>) nestlings in three coastal breeding colonies in Spain

The colonial ardeid Little Egret (Egretta garzetta), which is is protected under the European Birds Directive (2009/147/EC), can be a reliable bioindicator of aquatic environmental pollution. Concentrations of the heavy metals Cd, Cr, Cu, Hg, Ni, Pb and Zn in nestling feathers were assessed for three different breeding colonies of Little Egret on the Spanish coast during 2013 (5 individuals in Urdaibai, 10 in Santoña and 26 in Odiel). There were no significant differences in mean tissue residues of Cd, Ni, Pb and Zn between the colonies; however, mean concentration of Hg in Odiel nestlings was approximately three times lower than that of the other colonies, while Cr and Cu were significantly higher. In general, Little Egret nestlings from the three study sites had low levels of most of the measured metals, and thus the breeding populations did not appear to be at risk from heavy metal pollution. Baseline metal concentration in feathers derived from this study and calculated as the 90th percentile values were: 0.02 μg Cd g^?1 dw, 0.42 μg Cr g^?1 dw, 1.63 μg Hg g^?1 dw, 0.40 μg Pb g^?1 dw and 122 μg Zn g^?1 dw. However, mean Cu residues attained relatively high levels (17.6–26.9 μg Cu g^?1 dw) compared with data reported elsewhere, which raises concern and indicates a need for further research.     

Speciation and distribution characteristics of heavy metals and pollution assessments in the sediments of Nashina Lake,Heilongjiang, China

Sediment core samples from Nashina Lake, Heilongjiang, China were collected using a gravity sampler. The cores were sliced horizontally at 1 cm each to determine the particle size, total concentrations and speciation of Cd, Cr, Cu, Mn, Ni, Pb, and Zn. Total concentrations of heavy metals were extracted using an acid mixture (containing hydro fluoric acid, nitric acid, and sulphuric acid) and analyzed using an inductively coupled plasma spectrometry. A sequential extraction procedure was employed to separate chemical species. Analysis of results indicate that the concentrations of heavy metals in the sediments of Nashina Lake in descending order are Mn, Cr, Zn, Pb, Ni, Cu, and Cd. The ratios of the average concentrations of four heavy metals (e.g.Cr, Cu, Ni, Zn) to their background values were >1; and those of Mn, Cd, and Pb were >1. Moreover, some toxic metals were mainly distributed in bioavailable fractions. For instance, both Cd and Mn were typically found in Acid-extractable species or Fe–Mn oxide species, and thus can be easily remobilized and enter the food chain. Finally, the analysis of geo-accumulation index showed that anthropogenic pollution levels of Cr, Cu, Mn, Ni, Zn were low, but those of Pb and Cd were at the moderate level. As both Pb and Cd are toxic metals, it is highly necessary to prohibit their transformation and accumulation in the sediments.