Concentrations and ecological risks of metals in surface sediments of some coastal creeks in the Niger Delta,Nigeria

The concentrations of nine metals were measured by atomic absorption spectrophotometry in surface sediments of three coastal creeks, namely, the Ifie, Egbokodo and Ubeji creeks, in the Niger Delta of Nigeria, from August 2012 to January 2013. The aim of the study was to provide information on the spatial and seasonal distribution patterns, degree of contamination, and ecological risks of metals in these sediments. The mean concentrations of the nine metals in these creek sediments ranged from 0.30 to 3.20?mg kg^?1 Cd; 10.7 to 24.7?mg kg^?1 Pb, 125 to 466?mg kg^?1 Cr; 3.1.10 to 14.9?mg kg^?1 Cu; 4.7 to 14.3?mg kg^?1 Co; 61.1 to 115?mg kg^?1 Ni; 106 to 183?mg kg^?1 Mn; 52.0 to 170?mg kg^?1 Zn and 5 469 to 20 639?mg kg^?1 Fe. In general, the metal concentrations were higher in the dry season than the wet season, except for Cr. The concentrations of Cd, Cr, Ni and Zn were above their regulatory control limits in sediment as specified by the Nigerian Regulatory Authority and Cd was identified as the main ecological risk factor. The enrichment factors for the studied metals followed the order: Cd > Cr > Ni > Zn > Pb > Co > Mn > Cu. The average multiple pollution index values indicated that these sediments were severely polluted with significant inputs from Cd, Ni and Cr.     

Evaluation of Mercury Contamination in Fungi Boletus Species from Latosols,Lateritic Red Earths,and Red and Yellow Earths in the Circum-Pacific Mercuriferous Belt of Southwestern China

For the first time, highly elevated levels of mercury (Hg) have been documented for several species of the edible Fungi genus Boletus growing in latosols, lateritic red earths, and red and yellow earths from the Yunnan province of China. Analysis of Hg concentrations in the genus suggests that geogenic Hg is the dominant source of Hg in the fungi, whereas anthropogenic sources accumulate largely in the organic layer of the forest soil horizon. Among the 21 species studied from 32 locations across Yunnan and 2 places in Sichuan Province, the Hg was found at elevated level in all samples from Yunnan but not in the samples from Sichuan, which is located outside the mercuriferous belt. Particularly abundant in Hg were the caps of fruiting bodies of Boletus aereus (up to 13 mg kg^-1 dry matter), Boletus bicolor (up to 5.5 mg kg^-1 dry matter), Boletus edulis (up to 22 mg kg^-1 dry matter), Boletus luridus (up to 11 mg kg^-1 dry matter), Boletus magnificus (up to 13 mg kg^-1 dry matter), Boletus obscureumbrinus (up to 9.4 mg kg^-1 dry matter), Boletus purpureus (up to 16 mg kg^-1 dry matter), Boletus sinicus (up to 6.8 mg kg^-1 dry matter), Boletus speciosus (up to 4.9mg kg^-1 dry matter), Boletus tomentipes (up to 13 mg kg^-1 dry matter), and Boletus umbriniporus (up to 4.9 mg kg^-1 dry matter). Soil samples of the 0–10 cm topsoil layer from the widely distributed locations had mercury levels ranging between 0.034 to 3.4 mg kg^-1 dry matter. In Yunnan, both the soil parent rock and fruiting bodies of Boletus spp. were enriched in Hg, whereas the same species from Sichuan, located outside the mercuriferous belt, had low Hg concentrations, suggesting that the Hg in the Yunnan samples is mainly from geogenic sources rather than anthropogenic sources. However, the contribution of anthropogenically-derived Hg sequestered within soils of Yunnan has not been quantified, so more future research is required. Our results suggest that high rates of consumption of Boletus spp. from Yunnan can deliver relatively high doses of Hg to consumers, but that rates can differ widely because of large variability in mercury concentrations between species and locations.     

Assessment of Soil Arsenic,Chromium, Mercury,and Lead at an Agricultural Landscape Scale

Knowledge of arsenic and heavy metal concentrations and distributions is essential in the design of environmental regulatory strategies. The present study was undertaken as a preliminary survey on soil contamination in a representative agricultural area of southwestern China. The objectives were: (1) to characterize the variability of As, Cr, Hg, and Pb; (2) to assess the effect of land use (vegetable land and paddy fields) on these elements; and (3) to identify their natural or artificial origins. Samples from 119 sites were collected and analyzed in 2006. Land use map units were delineated at a scale of 1:2000 from field survey. Analysis of variance, correlation analysis, factor analysis, and a geographic information system were adopted to investigate the spatial distributions and sources of the elements. The average concentrations of the elements were 6.26 mg As kg^?1, 52.90 mg Cr kg^?1, 0.066 mg Hg kg^?1, and 33.13 mg Pb kg^?1. Mean contents of Hg and Pb were markedly higher than their background levels indicating the risk of mercury and lead pollution (p < 0.05). Mean concentration of Pb was significantly higher in paddy fields than vegetable land (p < 0.05). The variability of Cr was associated with topography, while Hg was controlled by human activities and atmospheric deposition. The high heterogeneities of As and Pb were mainly ascribed to land use and the consequent agricultural management practices. The results of the study will assist planners and policymakers in developing effective policies to protect soils from long-term arsenic and heavy metal accumulation.     

Mercury distribution in sediment profiles from lakes of the high pantanal,Mato Grosso State,Brazil

Sediment cores from lakes located in the Pantanal Swamp, Central Brazil were analysed for the distribution of mercury released by the local gold mining. Atmospheric transport is the only pathway of mercury contamination of these remote lakes. Mercury concentrations were higher at the surface of sediments (62 to 80 ug.kg^–1) decreasing to values of 20 to 30 ug.kg^–1 in deeper layers. Mercury deposition rate was estimated as 90 to 120 ug Hg.m^–2yr^–1 Although mercury concentrations were much lower than in industrialized areas, mercury deposition rate for these Pantanal lakes is of the same order of magnitude of deposition rates measured in lakes in industrialized areas     

Arsenic and Mercury in the Soils of an Industrial City in the Donets Basin,Ukraine

Soil and house dust collected in and around Hg mines and a processing facility in Horlivka, a mid-sized city in the Donets Basin of southeastern Ukraine, have elevated As and Hg levels. Surface soils collected at a former Hg-processing facility had up to 1300 mg kg^?1 As and 8800 mg kg^?1 Hg; 1M HCl extractions showed 74–93% of the total As, and 1–13% of the total Hg to be solubilized, suggesting differential environmental mobility between these elements. In general, lower extractability of As and Hg was seen in soil samples up to 12 km from the Hg-processing facility, and the extractable (1M HCl, synthetic precipitation, deionized water) fractions of As are greater than those for Hg, indicating that Hg is present in a more resistant form than As. The means (standard deviation) of total As and Hg in grab samples collected from playgrounds and public spaces within 12 km of the industrial facility were 64 (±38) mg kg^?1 As and 12 (±9.4) mg kg^?1 Hg; all concentrations are elevated compared to regional soils. The mean concentrations of As and Hg in dust from homes in Horlivka were 5–15 times higher than dust from homes in a control city. Estimates of possible exposure to As and Hg through inadvertent soil ingestion are provided.     

Using Earthworms to Assess Hg Distribution and Bioavailability in Gold Mining Soils

Between 1980 and 2000, the municipality of Cachoeira do Piriá, located in Pará State, Brazil, experienced an intense gold rush with approximately 5,000 artisanal miners discharging more than four tonnes of mercury into soils, air and aquatic systems. Mercury is dispersed across an area of approximately 2,100 ha and concentrations in soils and sediments frequently exceed 1,000 μg.kg^?1. The metallic mercury discharged by miners into the environment has the potential to be transformed into a highly toxic form of mercury, methylmercury. A 28-day bioassay with the earthworm Eisenia fetida was used to assess mercury bioavailability in mine tailings, soils, and sediments. Experiments indicated that the highest Hg concentration in earthworms was associated with low-Hg-organic-rich soils collected from densely vegetated areas despite higher mercury concentrations in organic-poor tailings. This indicates that reaction with organic acids is an important pathway for mercury incorporation into food chains. The quick, inexpensive, and simple bioassay also provided a means to evaluate remedial measures (i.e. by capping “hotspots” with local soils). Earthworm experiments indicate that covering “environmental hotspots” (sites with high Hg bioavailability) with local clay-rich sediments is very effective in terms of preventing uptake of mercury from tailings, while organic-rich sediments are relatively ineffective.     

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.     

Assessment of Total and Organic Mercury Levels in Blue Sharks (Prionace glauca) from the South and Southeastern Brazilian Coast

Mercury occurrence was evaluated in samples of edible muscle tissue of 27 blue sharks (Prionace glauca) caught in the Atlantic Ocean, adjacent to the south and southeastern Brazilian coast, indicating a slight increase in comparison with previous data obtained for the same studied area and being higher than those fish caught at different sites of the Atlantic Ocean. Total Hg concentrations ranged from 0.46 to 2.40 mg kg^?1 with the organic Hg fraction ranging between 0.44 and 2.37 mg kg^?1. A negative correlation between total Hg concentration in muscle tissue and blue shark size was obtained, and 40 % of samples analyzed had Hg concentrations higher than 1.0 mg kg^?1 Hg, the maximum concentration permitted in Brazilian predator fish. Data obtained showed that total Hg can be used as a reliable predictor of organic Hg in blue shark muscle because 95 to 98 % of the total Hg measured was found to be organic mercury. The wide range of Hg concentrations obtained for our set of samples can be explained by the heterogeneity of sampled population and the large size of the studied area. Given the adverse toxicological effects of Hg on animals and humans, a regular monitoring program of Hg contamination in Brazilian marine ecosystem can be recommended.     

Integrated assessment of the heavy metal pollution status and potential ecological risk in the Lagos Lagoon,South West,Nigeria

This study was carried out to assess the heavy metal pollution status and potential ecological risk in the Lagos lagoon, Nigeria. The concentrations of twelve heavy metals commonly associated with environmental pollution were determined in the sediments of the lagoon by Atomic Absorption Spectrophotometry (AAS) and the cold vapor method was employed for Mercury (Hg). Nonempirical risk indices and empirical Sediment Quality Guidelines (SQGs) were used to assess the ecological risk associated with heavy metal in the sediments. The nonempirical risk indices showed that Hg, Arsenic (As), and Cadmium (Cd) are the major contributors to the ecological risk associated with heavy metal pollution in the ecosystem. Comparison of heavy metal concentrations to the Screening Quick Reference Table (SQuiRT) showed that mean concentration of Cd (5.22 and 4.88 mg kg^?1 in dry and rainy seasons, respectively) exceeds the effect range low (ERL) value (1.20 mg kg^?1) in effect to biota. Industries sited around the lagoon have effluent output points in the lagoon serving as a major source of heavy metals coupled with indirect discharges from other sources. Heavy metals are nonbiodegradable, toxic and have the potential to alter ecosystem health, thus pollution sources should be effectively monitored and contained.     

Characterization of Pb and Cd contamination in the feces and feathers of rook (Corvus frugilegus) and the scalp hair of residents in Qiqihar,northeastern China

The concentrations of Pb and Cd, and trace elements (Cu and Zn) in the urban topsoil, rook (Corvus frugilegus) feces and feathers and human scalp hair were analyzed to examine the potential ecological risk posed by Pb and Cd on local residents of Qiqihar City, northeastern China. Results revealed that the Cd concentrations in the topsoil were ranged from 0.14 to 3.55 mg kg^?1 dry weight (dw). The maximal geoaccumulation indices [a value from logarithmic (a measured metal content/1.5 × background content of the metal in this region), introduced by Muller] of Cd exceeded 3.5, which suggested that this region was seriously contaminated by Cd. The corresponding average detectable concentrations in C. frugilegus feathers and feces were 1.38 and 3.97 mg kg^?1 dw for Pb and 1.04 and 0.69 mg kg^?1 dw for Cd. High Pb and Cd concentrations, respectively, ranging from 7.46 to 24.9 mg kg^?1 dw and from 0.35 to 0.92 mg kg^?1 dw were also detected in the human scalp hair samples. These high Pb and Cd concentrations in C. frugilegus and local people were possibly associated with local industrial wastes and vehicle exhausts. The external tissues (feces and feather) of the rook species can be considered as an indicator of potential Cd toxic risk in this species; however, the human scalp hair is not a reliable biomarker for risk of Pb and Cd in the human being. Effective measures should be established to reduce the inputs of Pb and Cd into the urban environment and to protect the health of local people.     

Mercury in the marine food chain in the Southern Ocean at Macquarie Island: an analysis of a top predator,Patagonian toothfish (<Emphasis Type="Italic">Dissostichus eleginoides</Emphasis>) and a mid-trophic species,the warty squid (<Emphasis Type="Italic">Moroteuthis ingens</Emphasis>)

The characteristics and habitat of the Patagonian toothfish (Dissostichus eleginoides) are typical of fish that accumulate high concentrations of mercury. In this study, mercury determinations were made on samples of muscle tissue from Macquarie Island toothfish and the Southern Ocean deepwater warty squid (Moroteuthis ingens). The analysis of mercury in the biological tissues was made by cold vapour-atomic absorption spectrometry following acid digestion. Performance of the analytical procedure was assessed by analysis of certified reference material (DORM-2, dogfish muscle). Mercury concentrations of 16 Macquarie Island toothfish ranged from 0.12 mg kg^–1 (550 g, 381 mm TL) to 0.59 mg kg^–1 (6,100 g, 823 mm TL), with a mean concentration of 0.33±0.12 mg kg^–1. A significant correlation was found between mercury and either toothfish weight or total length. The fish analysed were juveniles, which suggests that larger individuals would have higher mercury concentrations well exceeding food standard code limits for mercury in fish (typically 0.5 mg kg^–1). Warty squid, also from around Macquarie Island, had a low mean mercury concentration of 0.086 mg kg^–1 in mantle tissue; no significant correlation existed between mercury concentration and either squid mantle length or total weight. It is postulated that the squid have a mechanism, possibly involving the digestive gland, that prevents bioaccumulation of mercury in the mantle, and presumably other body tissues.     

Selenium Accumulation by Brassica Napus Grown in Se-Laden Soil From Different Depths of Kesterson Reservoir

Selenium (Se) may be present in soils and sediments in high concentrations and yet not be mobile or available for plant uptake. Phytoremediation of Se by canola (Brassica napus) was evaluated in sediment from Kesterson Reservoir at three different depths (0 to 30, 30 to 60, 60 to 90?cm) under greenhouse and field conditions. In the greenhouse study, total soil Se concentrations at preplant ranged from 10 to 112?mg kg^?1. Shoot Se concentrations of canola were 182, 53, and 19?mg kg^?1 DM in the 0 to 30, 30 to 60, and 60 to 90?cm depths, respectively. Percentages of Se accumulated by canola relative to total Se loss in the soil at postharvest were as high as 24%. In the field study, total soil Se concentrations were as high as 26?mg kg^?1 soil. Field-grown canola accumulated approximately 50?mg kg^?1 DM, which accounted for less than 10% of total Se lost in the soil at postharvest. Phytoremediation of Se-laden soils under field conditions was about 50% of that observed under controlled greenhouse conditions. This relationship may be useful for prediction of field remediation operation using greenhouse generated data.     

Cd AND Zn ACCUMULATION IN PLANTS FROM THE PADAENG ZINC MINE AREA

Significant cadmium (Cd) contamination In soil and rice has been discovered in Mae Sot, Tak province, Thailand where the rice-based agricultural systems are established in the vicinity of a zinc mine. The prolonged consumption of Cd contaminated rice has potential risks to public health and health impacts of Cd exposed populations in Mae Sot have been demonstrated. The Thai government has prohibited rice cultivation in the area as an effort to prevent further exposure. Phytoextraction, the use of plants to remove contaminants from soil, is a potential option to manage Cd–contaminated areas. However, successful phytoextraction depends on first identifying effective hyperaccumulator plants appropriate for local climatic conditions. Five sampling sites at Padaeng Zinc mine, Tak province were selected to collect plant and soil samples. Total Cd and Zn concentrations in sediments or soils were approximately 596 and 20,673 mg kg^?1 in tailing pond area, 543 and 20,272 mg kg^?1 in open pit area, 894 and 31,319 mg kg^?1 in stockpile area, 1,458 and 57,012 mg kg^?1 in forest area and 64 and 2,733 mg kg^?1 in Cd contaminated rice field. Among a total of 36 plant species from 16 families, four species (Chromolaena odoratum, Gynura pseudochina, Impatiens violaeflora and Justicia procumbens) could be considered as Cd hyperaccumulators since their shoot Cd concentrations exceeded 100 mg Cd kg^?1 dry mass and they showed a translocation factor > 1. Only Justicia procumbens could be considered as a Zn hyperaccumulator (Zn concentration in its shoot more than 10,000 mg Zn kg^?1 dry mass with the translocation factor > 1).     

Occurrence and distribution of organochlorine pesticide residue levels in water,sediment and aquatic weeds in the Nyando River catchment,Lake Victoria,Kenya

Samples of water, sediments and aquatic weeds were collected from 26 sites in the Nyando River catchment of the Lake Victoria basin in 2005–2006. The objective was to investigate levels of organochlorine pesticides that have either been banned or are restricted for use in Kenya. The pesticides investigated were lindane, aldrin, endosulfan, endrin, dieldrin, DDT, heptachlor and methoxychlor. These pesticides had previously found wide applications in public health and agriculture in Kenya for control of disease vectors and crop pests respectively. Results showed that mean concentrations were highest for methoxychlor (8.817 ± 0.020?µg l^?1) in water, sediments (92.893 ± 3.039 µg kg^?1), and weeds (39.641 ± 3.045?µg kg^?1), the weeds also tended to accumulate aldrin (15.519 ± 3.756?µg kg^?1). The results show that the pesticides are still in use and are detected in the catchment. Stringent management and public awareness measures are required to enforce the ban on the organochlorine pesticides in order to safeguard the environment and ecosystems of Lake Victoria.     

Biodiversity and extracellular enzymatic activity of heterotrophic bacterial communities in Bardawil Lagoon,Egypt

The biodiversity of heterotrophic viable bacteria (209 isolates) in the hypersaline Bardawil Lagoon, Egypt, was studied. Composition and extracellular activities of viable culturable heterotrophic bacteria (VCHB) in the water and in non-colonised and seagrass-colonised sediments of Bardawil Lagoon were determined bimonthly during 1997 and 1998. The average ± SD total Kjeldhal nitrogen was 1.69 ± 0.44 mg l^?1 in water, 335.95 ± 19.22 mg kg^?1 in colonised sediments, and 215.5 ± 16.0 mg kg^?1 in non-colonised sediments. Exoenzymatic bacterial activity (glycosidase) presented a seasonal trend with average values of 1.02 ±0.16 μM cm^?3 min^?1 in colonised sediment samples and was 0.36 ± 0.27 μM cm^?3 min^?1 in non-colonised sediments. Mean of VCHB was 4 017 ± 565 cfu g^?1 and 1 195 ± 242 cfu g^?1 for colonised and non-colonised sediments, respectively. Bacterial isolates from Bardawil Lagoon water and sediments yielded a wide diversity of VCHB: a total of 209 different species, belonging to 13 genera from the water and 12 genera from the sediments.     

Speciation of trace metals in chromated-copper-arsenate contaminated sediment of Ogba River

Abstract

The impact of storm water run-off from a location of intensive application of CCA in wood treatment on the quality of sediment of the receiving water body was examined. Sediment samples were collected along Ogba River. Physico-chemical characteristics as well as total levels of As, Cr and Cu in sediment samples were determined. Physico-chemical analysis of composite sediment samples upstream and downstream showed pH of sediments to be neutral (6.95 upstream and 6.90 downstream). The sand content for downstream sediment was 90.52 and 87.52% for upstream sediment sample. Total levels of 3.3–14.9 mg kg^?1 As, 3.1–116.6 mg kg^?1 Cr, and 13.7–16.4mg kg^?1 Cu were obtained for downstream sediment samples and 2.2–2.3mg kg^?1 As, 8.1–13.1 mg kg^?1 Cr, and 6.0–7.4mg kg^?1 Cu were obtained for upstream samples. Sequential extraction procedure involving six steps was used to evaluate the partitioning of As, Cr and Cu in the sediments. The results showed that the bioavailable fraction of sediment 20 m downstream was 10%, 100% and 20% of the total levels of As, Cr and Cu respectively in the sediment.     

Effects of complexing agents on the distribution of Hg(II) species provided by food to starfish Leptasterias polaris

Abstract

Mature starfish Leptasterias polaris were exposed to labelled mercury (II) species via food contaminated at a level of 5.0 μg g^?1. The distribution of inorganic Hg and methylmercury (MeHg) in starfish organs and tissues and the effect of a series of complexing agents on mercury translocation between organs and tissues were examined over a 24-h period. The distribution of mercury species in coelomic fluid components, ammonia excretion rate and mercury excretion were also measured. The highest concentrations were observed in the stomach (the source organ) and in pyloric caecum (up to 0.32 μg g^?1 wet weight for inorganic Hg and 0.22 μg g^?1 for MeHg). Concentrations of MeHg in gonads ranged from ≤ 0.01 to 0.08 μg g^?1 whereas concentrations of inorganic Hg never exceeded 0.06 μg g^?1. In all studied cases, mercury concentration was very low the coelomic fluid (≤ 0.01 μg g^?1). The short-term distribution of Hg species via contaminated food in starfish L. polaris seems to be controlled by the haemal system, a primitive circulatory system responsible for the transport of soluble nutrients from the digestive track towards organs and tissues, but a possible role of the coelomic fluid can not be excluded. Very low Hg contents were observed in gonads and in the coelomic fluid which fills the general cavity. Except for mercaptoethanol (merOH) and dimercaptosuccinic acid (DMSA), the addition of complexing agents to the food had little effect on the distribution of Hg species. MerOH appeared as an efficient carrier for methylmercury transport through the digestive system. DMSA enhanced the translocation of inorganic mercury from stomach and pyloric caecum toward external tissues and markedly increased its excretion.     

Lactating and nonlactating rats differ to renal toxicity induced by mercuric chloride: the preventive effect of zinc chloride

This study evaluated the effects of HgCl₂ on renal parameters in nonlactating and lactating rats and their pups, as well as the preventive role of ZnCl₂. Rats received 27 mg kg^?1 ZnCl₂ for five consecutive days and 5 mg kg^?1 HgCl₂ for five subsequent days (s.c.). A decrease in δ‐aminolevulinic acid dehydratase (δ‐ALA‐D) activity in the blood and an increase in urine protein content in renal weight as well as in blood and urine Hg levels were observed in lactating and nonlactating rats from Sal―Hg and Zn―Hg groups. ZnCl₂ prevented partially the δ‐ALA‐D inhibition and the proteinuria in nonlactating rats. Renal Hg levels were increased in all HgCl₂ groups, and the ZnCl₂ exposure potentiated this effect in lactating rats. Nonlactating rats exposed to HgCl₂ exhibited an increase in plasma urea and creatinine levels, δ‐ALA‐D activity inhibition and histopathological alterations (necrosis, atrophic tubules and collagen deposition) in the kidneys. ZnCl₂ exposure prevented the biochemical alterations. Hg‐exposed pups showed lower body and renal weight and an increase in the renal Hg levels. In conclusion, mercury‐induced nephrotoxicity differs considerably between lactating and nonlactating rats. Moreover, prior exposure with ZnCl₂ may provide protection to individuals who get exposed to mercury occupationally or accidentally. Copyright © 2014 John Wiley & Sons, Ltd.     

Cd AND Zn TOLERANCE AND ACCUMULATION BY SEDUM JINIANUM IN EAST CHINA

Field survey, hydroponic culture, and pot experiments were carried out to examine and characterize cadmium (Cd) and zinc (Zn) uptake and accumulation by Sedum jinianum, a plant species native to China. Shoot Cd and Zn concentrations in S. jinianum growing on a lead/Zn mine area reached 103–478 and 4165–8349 mg kg^?1 (DM), respectively. The shoot Cd concentration increased with the increasing Cd supply, peaking at 5083 mg kg^?1 (DM) when grown in nutrient at a concentration of 100 μmol L^?1 for 32 d, and decreased as the solution concentration increased from 200 to 400 μmol L^?1. The shoot-to-root ratio of plant Cd concentrations was > 1 when grown in solution Cd concentrations ≤ 200 μmol L^?1. Foliar, stem, and root Zn concentrations increased linearly with the increasing Zn level from 1 to 9600 μmol L^?1. The Zn concentrations in various plant parts decreased in the order roots > stem > leaves, with maximum concentrations of 19.3, 33.8, and 46.1 g kg^?1 (DM), respectively, when plants were grown at 9600 μmol Zn L^?1 for 32 d. Shoot Cd concentrations reached 16.4 and 79.8 mg kg^?1 (DM) when plants were grown in the pots of soil with Cd levels of 2.4 mg kg^?1 and 9.2 mg kg^?1, respectively. At soil Zn levels of 619 and 4082 mg kg^?1, shoot Zn concentrations reached 1560 and 15,558 mg kg^?1 (DM), respectively. The results indicate that S. jinianum is a Cd hyperaccumulator with a high capacity to accumulate Zn in the shoots.     

Spatial distributions and dose assessment of natural radionuclides in rocks and soils of some selected sites in southwestern Nigeria

The activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in rock and soil samples collected from Ondo and Ekiti States in southwestern Nigeria were measured by using gamma-ray spectrometer with a high-purity germanium (HPGe) detector. The mean activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K in the rock were 25.53, 61.12, and 554.20 Bq kg^?1 respectively, while that of the soil were 8.27, 17.37, and 151.72 Bq kg^?1 respectively. Results showed that the activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K were higher in the rocks than the soils of the areas studied. To assess the radiological impact of some radionuclides on the population in the region, the annual effective dose equivalent (AEDE), annual gonadal equivalent dose (AGED), and excess lifetime cancer risk (ELCR) were calculated. The mean values of the indoor and outdoor AEDE, and AGED were 88.08 µSv y^?1, 352.34 µSv y^?1, and 508.40 mSv y^?1, respectively for the rock samples, and 25.31 µSv y^?1, 101.25 µSv y^?1, and 145.80 mSv y^?1 respectively for the soil samples. The mean values obtained for AEDE and AGED for the soil were below ICRP recommended limits of 1 and 300 mSv y^?1, respectively. AGED for the rocks was higher than the maximum permissible limit.