Total mercury levels in selected tissues of some marine crustaceans from Persian Gulf, Iran: variations related to length, weight and sex

Internal and external spatial analysis of trace elements in local crayfish

Pollution in urban environments is a major health concern for humans as well as the local wildlife and aquatic species. Anthropogenic waste and discharge from storm drainage accumulate nutrients and environmental contaminants in local water systems. Locating contaminated sites using water samples over the vast landscape is a daunting task. Crayfish thrive in urban environments and have been used for biomonitoring pollutants. This study aimed to use crayfish as sentinels to monitor for elements in local environments. In this study, crayfish were used to measure metals and metalloids in lotic environments using ICP-OES analysis of abdominal and exoskeletal tissue. Using cluster analysis, geographical zones of trace element accumulation were determined. Eighteen total elements were analysed providing baseline data on local genera, biometric data, and element concentrations averaging 267.3 mg/kg Mn in the exoskeleton and with Zn averaging 6.88 mg/kg being significantly higher in the abdomen. Correlations of elements with biometric data allowed for internal analyses of elements. The elements As, Cr, Hg, Ni, and Tl demonstrated equivalent concentrations in both tissues. The crayfish locations with high abundance of elements allowed for the determination of contaminated areas with higher accumulations being areas of active urban development. These analyses gave measurable results of metal and metalloid to pinpoint potential sources of pollutants. Since crayfish are consumed globally as a food source, these methods can be used to determine the risk of toxic metals being passed through the food chain to the public.

Bioaccumulation of trace metal ions in the blue swimmer crab tissues Portunus pelagicus (Linnaeus, 1758) in Bahrain, Arabian Gulf

The blue swimmer crab, Portunus pelagicus, is an edible abundant crustacean found in many seas around the world, including the Arabian Gulf. In this study, the concentrations of six metal ions in the white and brown meats of P. pelagicus from four sites in Bahrain were determined. P. pelagicus was found to accumulate Zn2+ and Cu2+ higher than other metal ions in the order of Zn2+ > Cu2+ > Cd2+ > Ni2+ > Cr3+, while Pb2+ was not detected. The overall average concentrations of Zn2+, Cu2+, Cr3+, Ni2+, and Cd2+ in white meat were 236.2, 69.5, 0.109, 0.159, and 0.273 mg/kg, while in brown meat, they were 235.4, 199.2, 0.133, 1.25, and 4.87 mg/kg based on dry weight, respectively. Concentrations of Pb2+ and Cd2+ were safe according to Bahrain's and European Commission guidelines. The estimated weekly intake (EWI) values of Zn2+, Cu2+, Pb2+, and Cd2+ via consumption of crab's white meat (edible tissue) were 102.1, 30.1, 0.042, and 0.12 µg/kg/week, respectively, which are far lower than the maximum recommended values established by the FAO/WHO. The hazard quotient (HQ) values of individual trace metal ions and the synergistic effects of total trace metal ion (hazard index) were below 1, indicating that there is no potential health risk on the consumption of crab edible tissues (white meat). However, elevated levels of Cd2+ (0.05-1.73 mg/kg wet weight) in the brown meat (hepatopancreas) were detected. The female P. pelagicus accumulated high levels of Zn2+ and Cu2+ in the white meat, as well as Cu2+ in the brown meat compared to males. Additionally, it was found that Cu2+ and Cd2+ were significantly higher (p < 0.05) in brown meat compared to white meat. Higher concentrations (p < 0.05) of Zn2+, Cu2+, and Cd2+ were observed in crabs collected from sites that have harsher environmental conditions.

Targeted risk assessment of mercury exposure of recreational fishers: Are nephrops fishers in Norway at risk?

Recreational fishers often consume their catch, which may expose them to environmental contaminants. However, targeted risk assessment for exceeding the tolerable weekly intake (TWI) of a specific contaminant is often lacking, as specific data on the extent of fishing, consumption rates, and contamination of the caught seafood is needed. This study examined recreational fishing for nephrops (Nephrops norvegicus) at several different locations in Western Norway to identify important risk factors. The combination of a field survey to examine actual catches, interviews of recreational fishers about their seafood eating habits, and the analysis of total mercury (Hg, as a proxy for methylmercury (MeHg)) in recreationally captured nephrops allowed to conduct a targeted risk assessment. Recreational fishers consumed on average seven nephrops per meal, and 73% of the fishers ate nephrops once a month or more. The average Hg concentrations in nephrops were below the legal maximum level (100 ± 50 μg/kg wet weight (mean ± SD)). Hg concentrations in female nephrops were significantly higher than in males at the same size, and differed significantly between locations. The recreational fishers in this study were not at risk of exceeding the TWI for MeHg from consuming nephrops only; however, there is a general risk of exceeding TWI for MeHg as 70% of the fishers reported a frequent consumption of fish for dinner. Targeted risk assessments on recreational fishers may reveal particularly vulnerable populations where national dietary surveys may miss the highest seafood consumers.

Mercury and selenium concentrations in the crab Callinectes arcuatus from three coastal lagoons of NW Mexico

Mercury and selenium concentrations and Se:Hg molar ratio in edible muscle and hepatopancreas of the crab Callinectes arcuatus from coastal lagoons of northwest Mexico were determined using atomic absorption spectrophotometry. The three coastal lagoons were Santa María La Reforma (SMLR), Urías (UR), and Huizache-Caimanero (HC); samplings were carried out from December 2016 to October 2017. The mercury ranges in the muscle of C. arcuatus in SMLR, UR, and HC lagoons were 0.31-0.52, 0.15-0.45, and 0.22-0.55 μg g^-1, respectively. In hepatopancreas, the values ranged from 0.08 to 0.15, 0.06 to 0.15, and 0.05 to 0.12 μg g^-1 in SMLR, UR, and HC lagoons, in that order. For selenium concentrations in C. arcuatus muscle, the ranges 11.64-20.14, 14.88-19.71, and 15.27-29.51 μg g^-1 were determined in SMLR, UR, and HC lagoons, respectively. While for hepatopancreas, the ranges were 34.34-44.13, 27.77-40.45, and 15.16-49.80 μg g^-1, in that order. No significant relationships (p > 0.05) between mercury and selenium concentrations (in white meat and hepatopancreas) were observed in C. arcuatus carapace width and length. Se:Hg molar ratio values were 98.1 ± 20.8, 171.4 ± 81.6, and 176.8 ± 51.2 for SMLR, UR, and HC lagoons, in that order. This high ratio (> 1) in C. arcuatus edible muscle indicated that selenium concentration was sufficient to neutralize possible mercury toxicity, so it does not represent danger to humans when it is consumed.

Contamination of Fishery Products with Mercury, Cadmium, and Lead in Tunisia: Level's Estimation and Human Health Risk Assessment

The levels of metallic trace elements were determined in fishery products sampled from Tunisian fishing ports. Mean concentrations were 0.20 ± 0.01, 0.05 ± 0.01, and 0.10 ± 0.01 mg/kg in fish flesh for Hg, Cd, and Pb, respectively. The mean concentrations of these elements were below regulatory thresholds; however, we also detected some specimens with higher levels. The mercury level showed a significant difference between fish categories, region, and year of sampling (p < 0.05). Samples from the center sites had the highest levels of Pb (0.17 ± 0.03 mg/kg; range 0.10; 0.22 mg/kg). Temporal analysis of Pb showed a significant difference between sampling year (p < 0.05). In addition, distribution among fish categories was statistically significant (p = 0.046). The rates of samples exceeding limits of Hg, Cd, and Pb were 5.3, 2.6, and 0.4%, respectively. Through the above results, the maximum weekly and monthly intakes for fish flesh consumption could not exceed the set limits. These data were important to inform consumers about fish content and the risk generated by some of these species.

Bioaccumulation of heavy metals (Hg, Cd and Ni) by sentinel crab (Macrophthalmus depressus) from sediments of Mousa Bay, Persian Gulf

The presence of heavy metals (HMs) in the environment can increase their risk of transfer to the food chain. The present study was conducted to investigate the bioaccumulation of HMs including Hg, Cd and Ni in soft and hard tissues of sentinel crab (Macrophthalmus depressus Rüppell, 1830) in sediments of Mousa Bay in northwest of the Persian Gulf. The average (mean ± SD) amounts of Hg, Cd and Ni in the sediments were 6.27 ± 3.66, 3.8 ± 1.48 and 71.6 ± 5.09 μg/g, whereas the relevant amounts for soft tissues were 6.16 ± 4.64, 3.3 ± 1.7 and 19.7 ± 3.96 μg/g, and for hard tissues were, 2.9 ± 1.67, 3.5 ± 1.35 and 10.44 ± 3.1 μg/g, respectively. Accordingly, soft tissues of the crab could be suitable bioindicators of Hg and Cd, whereas the hard tissues could be used as Cd bioindicator. Since the bioaccumulation of Ni was the most, it might have a higher risk among the metals to enter the food chain in the region.

Concentrations of total mercury and methylmercury in red snow crabs (Chionoecetes japonicus) caught off the coast of Japan

The total mercury (T-Hg) and methylmercury (MeHg) concentrations in red snow crabs (Chionoecetes japonicus) caught off the coast of Japan were analyzed. The T-Hg concentration ranged from 0.03 to 0.56 mg/kg (mean: 0.21 mg/kg) in the raw muscle, and 0.02 to 0.74 mg/kg (mean: 0.27 mg/kg) in the boiled muscle. The MeHg concentration ranged from 0.04 to 0.54 mg/kg (mean: 0.20 mg/kg) in the raw muscle. The mean ratio of MeHg to T-Hg was 0.88. The crab body weight was found to significantly correlate with the concentrations of T-Hg (r = 0.488) and MeHg (r = 0.490) (p ≤ 0.01). For the general population in Japan, the intake of MeHg from eating red snow crab was estimated to be lower than 0.013 mg/week, which was less than one-sixth of the tolerable MeHg intake (0.08 mg/week).

Ingestion of inorganic mercury by juvenile black tiger prawns (Penaeus monodon) alters biochemical markers

There is a lack of information regarding the effects on biochemical markers in invertebrates diet-exposed to inorganic mercury. In the present study, juvenile black tiger prawn (Penaeus monodon) were fed with food dosed with mercuric chloride (low: 0.2 mg kg^-1; medium: 0.77 mg kg^-1; high: 1.41 mg kg^-1; higher: 2.52 mg kg^-1) and control (0.03 mg kg^-1) over 12 days. At the end of exposure periods, ventral nerve cord, compound eyes and muscle were dissected for biochemical marker analyses (acetylcholinesterase - AChE; lipoperoxidation - LPO; glutathione S-transferase - GST; catalase - CAT). Prawn muscle showed an increase in total mercury concentration over time for low and high treatments, but did not show an accumulation in comparison to controls. AChE activity tended to decrease over time in all tissues. CAT activity increased over time in controls and lower dose treatments but was suppressed in the higher treatment relative to controls on day 12; indicating that inorganic mercury is impacting the normal stress response by reducing the capacity to degrade hydrogen peroxide. In contrast, no effect was observed in LPO and GST activity. A depuration treatment was performed and compared to medium treatment; only AChE and GST activities from muscle showed significant difference, with AChE activity from depuration treatment lower than medium treatment, while the opposite was observed in GST activity. Overall, the low mercury accumulation observed over 12 days of exposure may have limited the biochemical stress responses, which could also have limited the detection of differences in the depuration treatment relative to medium treatment.

Concentrations of Cadmium, Copper, and Zinc in Macrobrachium rosenbergii (Giant Freshwater Prawn) from Natural Environment

This study analyzed the levels of cadmium (Cd), copper (Cu), and zinc (Zn) by the flame atomic absorption spectrophotometer (FAAS), in the muscle tissues, exoskeletons, and gills from freshwater prawn (Macrobrachium rosenbergii) (n = 20) harvested from natural habitat in Kerang River, Malaysia on 25th November 2015. Significant increase of the metals level in muscle tissue and gill (r > 0.70, p < 0.05) were observed with increase in length except for Cu in gills. No relationship was found between metals level in exoskeleton and length. The concentrations of Cd, Cu and Zn were significantly higher (p < 0.05) in males (muscle tissues and exoskeleton) except for Cd in exoskeleton. In gills, only Cu was significantly higher (p < 0.05) in female than male. All samples contained metals below the permissible limit for human consumption (i.e., Cd < 2.00 mg/kg; Cu < 30.00 mg/kg; Zn < 150 mg/kg). Annual metals monitoring in prawn and environmental samples is recommended to evaluate changes of metals bioaccumulation and cycling in the system, which is useful for resources management.

Hair mercury and risk assessment for consumption of contaminated seafood in residents from the coast of the Persian Gulf, Iran

The health risks of mercury exposure due to the high consumption of aquatic were assessed for fishermen and non-fishermen families living on the Bandar Abbas, Bushehr, and Mahshahr cities located in the coast of Persian Gulf (Iran). The mean hair mercury concentration of people in Bandar Abbas, Bushehr, and Mahshahr cities was obtained 1.56 ± 0.17, 1.97 ± 0.22, and 5.12 ± 0.3 μg g^-1, respectively. Hair mercury concentration in 8.8% of people exceeded the no observed adverse effects level (NOAEL) of 10 μg g^-1 declared by the World Health Organization (WHO). The fish and shrimps consumption, place of living, and fisher and non-fisherman family were variables that significantly effected on mercury levels in the hair. The effect of other factors (age, sex, and number of dental amalgam fillings) on hair mercury was not significant. The mean concentrations of mercury in three fish species in Mahshahr exceeded the recommended maximum standard level (0.5 μg g^-1) set by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA). The estimated weekly intake (EWI) for mercury in some fish species in Bandar Abbas, Bushehr, and Mahshahr was higher than the provisional tolerable weekly intake (1.6 μg kg^-1 bw) set by European Food Safety Authority (EFSA) for some groups. The significant positive correlation between daily mercury intake and hair mercury concentration of people (r = 0.64, P < 0.001) reasserts that the hair mercury concentration could be explained by fish consumption. HQ > 1 was obtained for women in child bearing age in fishermen families in Bandar Abbas and Bushehr cities, children in fishermen families in Bushehr, and for all groups of population except adult in non-fishermen families in Mahshahr. So, the limited consumption of some fish species for these groups of people is recommended. The maximum of allowable fish consumption rate was 0.70 meals/month for Pseudorhombus arsius from Mahshahr fish for women of child bearing age. Also, it is necessary to create and monitor and enforce environmental standards, preventing the entry of pollutants released into the marine aquatic environment without proper early treatment.

Heavy Metals Bioaccumulation in Tissues of Spiny-Cheek Crayfish (Orconectes limosus) from Lake Gopło: Effect of Age and Sex

The aim of the present work was to assess the concentrations of metals in the abdominal muscle and exoskeleton of 3-year-old males and 4-year-old females and males of spiny-cheek crayfish (Orconectes limosus) collected from Lake Gopło. A total of 93 males and 35 females were collected in autumn (October 2014). The analyzes of heavy metals were conducted by means of atomic absorption spectroscopy with a PU9100X spectrometer. The content of mercury was determined using AMA 254 mercury analyser. As analyses indicated heavy metals accumulated in the muscle and exoskeleton in the following sequence: Zn > Cu > Pb > Mn > Ni > Hg and Mn > Pb > Zn > Ni > Cu > Hg, respectively. Statistically significant differences between 3- and 4-year-old males were found for all analyzed metals. Gender dependent differences were calculated only for Ni in the muscle tissue and for Mn and Hg in the exoskeleton. In comparison with the study carried out 2 years ago notably higher concentrations of Pb were found in the muscle and a higher content of Zn, Pb, Mn and Ni was determined in the exoskeleton.

Determination of nickel and thallium concentration in Cynoglossus arel fish in Musa estuary, Persian Gulf, Iran

Heavy metals with high bioaccumulation capacity are considered as important contaminants and may be available in high concentrations in environment and biota samples. The main aim of this study was to determine the concentration of nickel and thallium in Cynoglossus arel fish in Musa estuary. Sixty-seven fish samples were collected from Musa estuary during five intervals of 15 days in summer 2013. After biometric measurements, the concentrations of nickel and thallium were measured by graphite furnace atomic absorption spectrophotometer. The mean concentration of nickel and thallium in muscle tissue of fish samples was 2.458 ± 0.910 and 0.781 ± 1.754 mg kg^-1/ww, respectively. The GLM analysis showed a significant negative relationship between nickel concentration and length. In addition, there was a significant positive relationship between thallium concentration and fish length. Nickel concentration exceeded the allowable standards of WHO and FDA in Cynoglossus arel. Therefore, regarding with high consumption of seafood in this region, it is recommended that these fishes should be consumed under a nutritionist counseling.

The mercury levels in crustaceans and cephalopods from Peninsular Malaysia

This study is to determine total mercury in edible tissues of eight species of cephalopods and 12 species of crustaceans purchased from 11 identified major fish landing ports and wet markets throughout Peninsular Malaysia. The concentration of mercury was measured by cold vapor atomic absorption spectrometry (AAS) technique using the Perkin Elmer Flow Injection Mercury System (FIMS-400). In general, the mercury levels were low with concentrations in cephalopods ranging from 0.099 to 2.715 mg/kg dry weight (or 0.0184-0.505 mg/kg wet weight) and in crustaceans ranging from 0.057 to 1.359 mg/kg dry weight (or 0.0111-0.265 mg/kg wet weight). The mercury levels showed no significant differences (P > 0.05) between species for both cephalopods and crustaceans. There was no significant correlation between mercury concentrations and the body size of individual for both groups as well. Comparisons with mercury levels obtained found from other previous studies and/or species noted that they were of the same magnitude or relatively low compared to various locations reported worldwide.

Determination of mercury and vanadium concentration in Johnius belangerii (C) fish in Musa estuary in Persian Gulf

The main aim of this study was to determine the concentrations of mercury and vanadium in Johnius belangerii (C) fish in the Musa estuary. A total of 67 fishes were caught from the Musa estuary during five intervals of 15days in the summer of 2013. After biometric measurements were conducted, the concentrations of mercury and vanadium were measured in the muscle tissue of fish using a direct method analyzer (DMA) and a graphite furnace atomic absorption spectrophotometer, respectively. The mean concentration of mercury and vanadium in the muscle tissue of fish was 3.154±1.981 and 2.921±0.873mg/kg w.w, respectively. The generalized linear model (GLM) analysis showed a significantly positive relationship among mercury concentration, length, and weight (P=0.000). In addition, there was a significantly negative relationship between vanadium concentration and fish length (P=0.000). A reverse association was found between concentrations of mercury and vanadium. Mercury concentration exceeded the allowable standards of the Environmental Protection Agency (EPA), the World Health Organization (WHO), and the Food and Drug Administration (FDA) in J. belangerii (C).

Mercury content and their risk assessment in farmed shrimp Litopenaeus vannamei from NW Mexico

The main objective of this study was to evaluate the total mercury content in hepatopancreas and edible muscle of the whiteleg shrimp Litopenaeus vannamei cultured along the NW coast of Mexico, and to evaluate the potential human health risk due to their consumption. Samples were obtained between May and June 2010 in 26 shrimp farms from the three most important shrimp-producing states of NW Mexico, and total Hg was analyzed after reduction with SnCl2 in a mercury analyzer. The ranges of Hg concentrations of the hepatopancreas were 0.101±0.03-0.184±0.13 μg g(-1) in Sonora, 0.077±0.055-0.813±0.363 μg g(-1) in Sinaloa and 0.139±0.037-0.791±0.33 μg g(-1) in Nayarit. In the muscle, values were from 0.078±0.02 to 0.539±0.09 μg g(-1) in Sonora, 0.154±0.03-0.861±0.423 μg g(-1) in Sinaloa and 0.121±0.041-1.48±0.44 μg g(-1) in Nayarit. Considering the concentrations of Hg in the muscle and the national consumption rate, shrimp farmed in NW Mexico does not represent a risk for human health (HQ<1).

Biomonitoring of heavy metals using bottom fish and crab as bioindicator species, the Arvand River

The main aim of this study was to biomonitor mercury (Hg), arsenic (As), cadmium (Cd), lead (Pb) and copper (Cu) concentrations in the Arvand River using Heteropnestis fossilis and Parasesarma persicum. Comparison of heavy metals among the stations indicated that the concentrations of Hg, As, Cd, Cu and Pb in sediment samples were apparently different among the stations. The results of linear regression analyses showed that there were significant correlations ( p < 0.05) between Hg, As and Pb elements in sediment and hepatopancreas of P. persicum and between As in sediment and liver of H. fossilis. These findings showed that P. persicum could be considered as a biomonitor of Hg, As and Pb and H. fossilis as a biomonitor of As contamination in sediment of the Arvand River.

Mercury accumulation in selected tissues of shrimp Penaeus merguiensis from Musa estuary, Persian Gulf: variations related to sex, size, and season

The levels of mercury in tissues of Penaeus merguiensis from Musa estuary, northwest of the Persian Gulf, were investigated. This study assessed the relationship between mercury levels in hepatopancrea, gill, and muscle with sex, size, and season. The order of mercury concentrations in tissues of the shrimp P. merguiensis was as follows: hepatopancreas > gill > muscle. There was a positive correlation between mercury concentrations in shrimp species with sex and size of its food items. We expected to see higher mercury levels in tissues of female species because they are larger and can eat larger food items. Also, there was a positive correlation between mercury concentrations in shrimp species with its food source. Therefore, female species feed more on shrimp and plant and are contaminated with high levels of mercury. There was significant difference (p < 0.05) in mercury levels between different seasons; higher mercury levels were found in July (summer season).

Mercury bioaccumulation and the population dynamics of Mesopodopsis slabberi (Crustacea: Mysidacea) along a mercury contamination gradient

The mercury bioaccumulation and population dynamics of the mysid Mesopodopsis slabberi was assessed along a mercury gradient in Ria de Aveiro (Portugal). M. slabberi is one of the most important mysid species in European temperate coastal shallow waters playing a key ecological role. Nevertheless, no references were found concerning the possible consequences of the Hg on the trophodynamics of these coastal ecosystems. M. slabberi showed a clear bioaccumulation along the Hg gradient and through life, with mature females reaching the highest concentrations. In terms of population structure, higher densities and biomasses of M. slabberi were assessed in the most contaminated areas contrarily to the least polluted areas. Despite the mercury accumulation in its tissues no strong negative effects on the structure and population dynamics of the species were observed. However, mysids might be important in the transfer of metals from the sediments and zooplankton to higher trophic levels such as fishes, most of them with commercial interest.

Mercury in the atmospheric and coastal environments of Mexico

In Mexico, published studies relating to the occurrence of Hg in the environment are limited. Among the main sources of Hg in Mexico are mining and refining of Auand Hg, chloralkali plants, Cu smelting, residential combustion of wood, carbo electric plants, and oil refineries. Hg levels are highly variable in the atmospheric compartment because of the atmospheric dynamics and ongoing metal exchange with the terrestrial surface. In atmospheric studies, Hg levels are usually reported as total gaseous Hg (TGM). In Mexico, TGM values ranged from 1.32 ng m-3 in Hidalgo state (a rural agricultural area) to 71.82 ng m-3 in Zacatecas state (an area where brick manufacturers use mining wastes as a raw material).Published information on mercury levels in the coastal environment comprise 21 studies, representing 21 areas, in which sediments constituted the substrate that was analyzed for Hg. In addition, water samples were analyzed for Hg in nine studies.Few studies exist on Hg levels in the Caribbean and in the southwest of the country where tourism is rapidly increasing. Hence, there is a need for establishing baseline levels of mercury in these increasingly visited areas. In regions where studies have been undertaken, Hg levels in sediments were highly variable. Variations in Hg sediment levels mainly result from geological factors and the varying degree of anthropogenic impacts in the studied areas. In areas that still have pristine or nearly pristine environments (e.g., coast, Baja California, Todos Santos Bay, and La Paz lagoon), sediment Hg levels ranged from <0.006 to 0.35 j.lg g-1 on a dry wt basis.When higher levels exist (0.34-57.94 j.lg g-1 on a dry wt basis), the environment generally shows the influence of inputs from mining, oil processing, agriculture,geothermal events, or harmful algal bloom events (e.g., Guaymas Bay and Coatzacoalcos estuary). From chronological studies performed in selected coastal lagoons in NW Mexico, it is clear that Hg fluxes to sediments have increased from2- to 15-fold in recent years. Since the 1940s, historical increases of Hg fluxes have resulted from higher agricultural waste releases and exhaust from the thermo electric plants. The levels of Hg in water reveal a moderate to elevated contamination of some Mexican coastal sites. In Urias lagoon (NW Mexico), moderate to high levels were found in the dissolved and suspended fraction, and these are related to shipping, the fishing industry, domestic effluents, and the presence of a thermoelectric plant. In Coatzacoalcos (SE Mexico), extremely elevated Hg levels were found during the decade of the 1970s. Low to moderate levels of Hg were measured in waters from the Alvarado lagoon (SE Mexico); those concentrations appear to be associated with river waters that became enriched with organic matter and suspended solids inthe brackish mixing zone.Regarding the Hg content in invertebrates, the use of bivalves (oysters and mussels)as biomonitors must be established along the coastal zones of Mexico, because some coastal lagoons have not been previously monitored. In addition, more research is needed to investigate shrimp farms that are associated with agricultural basins and receive effluents from several anthropogenic sources (e.g., mining activity and urban discharges). Hg residues in several vertebrate groups collected in Mexico have been studied.These include mammals, birds, reptiles, and fish. In elasmobranch species, the highest Hg concentration (27.2 flg g-1 dry wt) was found in the muscle of the smooth hammer head shark (Sphyrna zygaena). Teleost fish are the vertebrate group that has been most studied, with regard to Hg residue content; the highest value (5.67 11g g-1dry wt) was detected in the striped marlin (T. audax). Among reptiles, only marine turtles were studied; Hg levels found ranged from 0.795 in the liver to 0.0006flg g-1dry wt in the blood of L. olivacea. In birds, the highest Hg concentration (5.08 flg g-1dry wt) detected was in the liver of the olivaceous cormorant (P. olivaceous).Specimens from stranded marine mammals were also analyzed; levels of Hg ranged from 70.35 flg g-1 dry wt in the liver of stranded spinner dolphin (S. longirostris ), to0.145 flg g-1 dry wt in the muscle of gray whale (E. robustus). The presence of Hgin these marine animals is not thought to have caused the stranding of the animals.Other organisms like macroalgae and vestimentiferan tube worms were used to monitor the occurrence of Hg in the aquatic environment; levels were comparable to data reported on similar organisms from other areas of the world. Few investigation shave been carried out concerning the mercury content in human organs/tissues in Mexico. Considering the potential deleterious effects of Hg on kidney, lung, and the central nervous system, more information about human exposure to organic and inorganic forms of mercury and their effects is needed, both in Mexico and elsewhere.

Analysis of heavy metals concentration in water and sediment in the Hara biosphere reserve, southern Iran

This study determined the concentration of heavy metals (Al, Cr, Cu, and Zn) in water and sediments at nine sites in the Hara biosphere reserve of southern Iran during the summer and winter 2010. Determination of Al, Cr, Cu, and Zn in water was carried out by graphite furnace atomic absorption spectrometer (Shimadzu, AA 610s) and in sediment by flame atomic absorption spectrometer (Perkin Elmer, AA3030). Results showed that the heavy metal concentrations in the water samples decreased in the sequence of Zn > Al > Cu > Cr, while in sediment samples were Cr > Zn > Cu > Al. Data analysis indicated that with the exception of Al, there was a Pearson's correlation coefficient between pH and Cu, Zn, and Cr at α = 0.01, 0.05, and 0.001 in sediment (in winter), respectively. There were also significant differences between heavy metals of Cr, Cu, and Zn during the two seasons (p < 0.001) in the water and sediment.