Heavy Metals in the Blue Crab (<Emphasis Type="Italic">Callinectes sapidus</Emphasis>) in Mersin Bay,Turkey

The concentrations of four metals (copper, cadmium, zinc and lead) were quantified in blue crabs (Callinectes sapidus) tissues collected in January, April, June and September at two stations in Mersin Bay, northeastern Mediterranean Sea, using ICP-MS. The metal concentrations in crabs from the two stations differed significantly. The hepatopancreas was the major organ accumulating metals, followed by gill and muscle tissues. Except for lead, the highest concentrations of metals were measured in the hepatopancreas. The hepatopancreas had higher concentrations of all heavy metals (Cu 321.1?±?4.30; Zn 182.2?±?3.40; Cd 48.2?±?2.00) compared to gill (Cu 90.2?±?1.35; Zn 104.3?±?2.30; Cd 22.3?±?3.40) and muscle (Cu 19.1?±?1.10; Zn 55.1?±?3.25; Cd 2.5?±?0.20). Among the metals analyzed, Cu, Zn and Pb were the most abundant in the different tissues while Cd was the least abundant in C. sapidus. Seasonality in the levels of the four metals was determined.The highest concentrations of all metals were observed in the June (Zn 55.1?±?3.25; Cu 19.1?±?1.10; Cd 2.5?±?0.20; Pb 5.1?±?0.18) compared to all other months (Zn 34.1?±?3.23; Cu 11.1?±?1.15; Cd 0.9?±?0.20; Pb 3.1?±?0.21).     

Composition of heavy metals in indoor dust and their possible exposure: a case study of preschool children in Malaysia

The aim of this study is to determine the levels of selected heavy metals (Pb, Zn, Cd, Fe and Cr) at ten preschools in Selangor, Malaysia. Dust samples from the interior of classrooms and surface soils were collected using soft paint brushes while Kimwipes were used to collect samples of dust from interior walls and children’s palms. Heavy metals in the dust samples were determined using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of the selected heavy metals in the indoor dust were dominated by Fe with a concentration of 4,801?±?1,873 μgg^?1 followed by Pb?>?Zn?>?Cr and Cd with concentration of 253.5?±?83.2, 144.9?±?73.4, 11.9?±?6.8 and 0.23?±?0.10 μgg^?1, respectively. Fe also had the highest concentration of all the heavy metals investigated in the samples taken of soil dust (8,225?±?6,800 μgg^?1), the interior walls (1,865?±?756 μgm^?2) and children’s palms (3,882?±?3,401 μgm^?2). Using enrichment factor (EF) analyses, Pb, Zn and Cd in the indoor dust were found contributed by anthropogenic factors while the same was true for Zn, Cd and Cr in the indoor wall and children’s palm samples.     

Ecotoxicological Test Assay Using OECD TG 212 in Marine Java Medaka (<Emphasis Type="Italic">Oryzias javanicus</Emphasis>) and Freshwater Japanese Medaka (<Emphasis Type="Italic">Oryzias latipes</Emphasis>)

The study explored (I) the concentration of heavy metals in water samples (II) their bioaccumulation in common carp Cyprinus carpio (III) and the subsequent genotoxicity in the selected organs of carp; from river Kabul, Khyber Pakhtunkhwa Pakistan. Except for Mercury (Hg) the water samples had all the heavy metals within permissible limits of recommended dietary allowance (RDA). Nonetheless a number of heavy metals (Zn, Ni, Cr, Cd, Pb and Hg) showed bioaccumulation at levels higher than permissible. Zinc (Zn) was the most while Cadmium (Cd) was the least accumulated metal in all tissue samples analyzed. The metal burden in different organs of C. carpio was in sequence of intestine?>?skin?>?liver?>?gills?>?muscle. The Comet assay established DNA damage in selected organs to be in accordance with metal burden; the most to least damage being in sequence of blood?>?intestine?>?skin?>?liver?>?gills?>?muscle. In conclusion assessment of DNA damage in the organs of C. carpio appears to be a useful bio-marker to evaluate genotoxic effects of heavy metal pollution.     

Heavy Metal Contamination in Fish (<Emphasis Type="Italic">Callinectis amnicola</Emphasis>) From an Estuarine Creek in the Niger Delta,Nigeria and Health Risk Evaluation

Heavy metal bioconcentration in crabs from an estuarine creek in the Niger Delta was examined using atomic absorption spectrophotometry. Health risk via human exposure to metal toxicity was evaluated. Mean metal levels (µg/g) were Cr 2.32?±?0.71, Ni 2.76?±?0.48, Cu 12.94?±?3.53, Pb 5.67?±?1.03, Ag 1.83?±?0.71 and Cd 0.73?±?0.14 with significant difference (p?<?0.001) between periods. Ni, Pb and Cd had values above FAO/WHO recommended limits. Estimated daily intake values were below the reference oral doses and the target hazard quotient was <1 for each metal examined while hazard index for all metals was also <1. The target carcinogenic risk value for Ni was 3.4?×?10^?3. Based on the evaluations, the study concluded that consumers of crabs from the study area had minimal/moderate metal toxicity exposures of no significant health concern but recommended continuous monitoring to detect anomalies.     

Determination and health risk assessment of heavy metals in imported rice bran oil in Iran

In this current study, the contents of heavy metals including Pb, As, Cr, Cd, Zn, Cu, and Mn in imported rice bran oil in Iran were investigated with microwave digestion method based on an inductively coupled plasma optical emission spectrometry system (ICP-OES). The concentrations range of Pb, Cr, Cd, As, Zn, and Cu in rice bran oil samples were measured as 0.066–0.30, 0.008–0.014, 0.005–0.01, 0.047–0.01, 0.025–0.74 and 0.01–0.096 μg/g, respectively. A significant difference (p-value < 0.05) in the mean concentration of Pb in imported rice bran oils samples was observed. The sum of incremental lifetime cancer risk (ILCR) for heavy metals for children and adults were 2.6 × 10⁻⁴ and 2.4 × 10⁻⁵, respectively, which an acceptable level proposed values (10⁻⁴–10⁻⁶) by U.S. EPA. Moreover, the target hazard quotients (THQs) of As, Pb, Cr, Cd, Cu, and Zn for children were limited to between 1.17 × 10^-5 and 9.49 × 10⁻⁹, and in adults were limited to 2.33 × 10⁻⁷and 6.82 × 10^-7, which were lower than the acceptable limit (THQ < 1). There have been concerns regarding heavy metals since past up to now in all foodstuffs. We demonstrated in this study that there are traceable concentrations of heavy metals in six brand of rice bran oils.     

Heavy Metal Concentration in Largehead Hairtail (<Emphasis Type="Italic">Trichiurus lepturus</Emphasis> Linneaus, 1758) and Savalai Hairtail (<Emphasis Type="Italic">Lepturacanthus savala</Emphasis> (Cuvier, 1829)) Obtained from Karachi Fish Harbour,Pakistan

In this study, muscle samples gathered from Largehead hairtail (Trichiurus lepturus Linneaus, 1758) and Savali hairtail [Lepturacanthus savala (Cuvier, 1829)] from the Karachi Fish Harbour, Pakistan were analyzed to determine heavy metal concentrations (iron [Fe], zinc [Zn], copper [Cu], manganese [Mn], lead [Pb] and cadmium [Cd]) between January and December 2016. All samples were analyzed using the AAnalyst 700 Flame Atomic Absorption Spectrophotometer. It was observed that the average measured level of Fe, Zn, Cu, Mn, Pb and Cd in muscle were 77.72?±?47.84 µg/g, 20.34?±?8.49 µg/g, 2.23?±?1.16 µg/g, 0.57?±?0.36 µg/g, 0.20?±?0.16 µg/g and 0.42?±?0.19 µg/g for T. lepturus, respectively. Besides, the average level of the same metal concentrations in muscle for L. savala were 85.11?±?57.64 µg/g, 16.63?±?9.25 µg/g, 2.53?±?1.90 µg/g, 0.47?±?0.27 µg/g, 0.23?±?0.18 µg/g and 0.47?±?0.20 µg/g, respectively. The correlation between size groups and metal accumulation in muscle tissues were investigated for both fish. In terms of public risk assessment, the provisional tolerable weekly intake’s of various heavy metals were compared with the consumption of both fish. As a result of the analysis, Fe, Zn, Cu, Mn, Pb and Cd accumulations in muscle tissues of T. lepturus and L. savala collected from Karachi Fish Harbour Pakistan did not exceed limit values.     

Metal Accumulation Strategies of Emergent Plants in Natural Wetland Ecosystems Contaminated with Coke-Oven Effluent

The release of industrial effluents into natural wetlands is a ubiquitous problem worldwide, and phytoremediation could be a viable option for treatment. The present study assessed metal accumulation strategies of three dominant emergent plants [Colocasia esculenta (L.) Schott, Scirpus grossus (L.) f., and Typha latifolia L.] growing in a wetland contaminated with coke-oven effluent. Metals concentration (mg kg^?1) in wetland sediment followed the order Mn (408)?>?Cu (97)?>?Co (14.2)?>?Cr (14)?>?Cd (2.7). Plant tissues (root and shoot) showed metal-specific accumulation at different extents due to plant response against metal utility or toxicity. Bioconcentration factor (BCF) and translocation factor (TF) of metals in plants revealed Cd and Mn pollution could be remediated through phytoextraction (BCF?>?1 and TF?>?1); however, Co, Cu, and Cr pollution could be remediated through phytostabilization (BCF?>?1 and TF?<?1).     

Appraisal of Heavy Metals in Groundwater in Chennai City Using a HPI Model

Heavy metal contamination in Chennai city was evaluated using a heavy metal pollution index (HPI) model in conjunction with the spatial distribution maps. Metals such as Cd, Cr, Cu, Pb and Zn in the groundwater were determined using standard methods and the resultant data was utilized in the development of a HPI model. The metal concentrations showed a dominance in the order of Zn > Cu > Cr > Pb > Cd respectively. About 14.3 % of the samples (n = 2), exhibited high HPI (>38) and the highest value, HPI = 97.55, has been recorded from Thiruvanmiyur area. Statistical analysis revealed a positive correlation between metals such as Cd and Cr (r = 0.606), Cd and Cu (r = 0.601), Cr and Cu (r = 0.464) and Pb and Zn (r = 0.416), suggested their common origin. The spatial distribution maps of heavy metals and the HPI suggested that the SW region, especially Adyar and Thiruvanmiyur regions are highly contaminated with the metals. Industrialisation and improper waste dumping were identified as the major cause for the accumulation of metals in the groundwater of Chennai city.     

Concentrations of Cadmium,Copper, and Zinc in <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> (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.     

Arbuscular Mycorrhizal Fungi Favor the Initial Growth of <Emphasis Type="Italic">Acacia mangium,Sorghum bicolor</Emphasis>, and <Emphasis Type="Italic">Urochloa brizantha</Emphasis> in Soil Contaminated with Zn,Cu, Pb,and Cd

This study evaluated the effect of inoculation with a mixture of spores of arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, Paraglomus occultum, and Glomus sp.) on the initial establishment of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in soil contaminated with heavy metals. The experiment was conducted in a greenhouse, in plastic pots containing 1.8 kg of soil, which presented 7200, 1140, 480, and 72 mg of Zn, Cu, Pb, and Cd, respectively. The chlorophyll content (SPAD index) of inoculated plants of A. mangium and U. brizantha was higher than those of non-inoculated plants (p?<?0.05). No differences were detected for the concentration of heavy metals in plant shoots, whether the plant was inoculated or not. However, inoculated plants had greater root length (S. bicolor and U. brizantha) (p?<?0.05) and greater plant height (A. mangium) (p?<?0.05). The present results demonstrate that the beneficial effects of AMF on plant growth and the alleviation of contaminants are imperative factors for the rehabilitation of soils contaminated with heavy metals.     

Heavy Metal Contamination and Ecological Risk Assessment of Swine Manure Irrigated Vegetable Soils in Jiangxi Province,China

Heavy metal are often added to animal fodder and accumulate in the soils with swine manure. In this study, heavy metal (Cu, Pb, Cd, Zn, As and Cr) concentrations were determined in agricultural soils irrigated with swine manure in Jiangxi Province, China. Results showed that the average concentrations of Cu, Zn, As and Cr (32.8, 93.7, 21.3 and 75.8 mg/kg, respectively) were higher than the background values, while Pb and Cd (15.2 and 0.090 mg/kg, respectively) were lower than the background values. Contamination factors \(\left( {C_{f}^{i}} \right)\) indicated that they were generally moderate for Cu, Zn, As and Cr and generally low for Pb and Cd. The contamination degree (C _d ) was calculated to be 7.5–10.0 indicating a moderate degree of contamination. The geoaccumulation index (I_geo) indicated that the soils were unpolluted with Zn, Cd and Pb, while unpolluted to moderately pollute with Cr, Cu and As. The single ecological risk factor \(\left( {E_{r}^{i}} \right)\) revealed that the six heavy metals all belonged to low ecological risk. The ecological risk indices suggested that all the sampling sites were at low risk level.     

Assessment of heavy metal characteristics and health risks associated with PM<Subscript>2.5</Subscript> in Xi’an,the largest city in northwestern China

Fine particulate matters (PM_2.5) samples were collected in Xi’an, northwestern China, from May 2015 to April 2016. The concentrations, seasonal variations, potential sources, and health risks for personal exposure for ten metallic elements (i.e., Ba, Zn, Cu, As, Ni, Pb, Mn, Cr, Cd, and Hg) bounded to PM_2.5 were determined and assessed in this study. The results showed that the average PM_2.5 mass concentration in Xi’an was 62.1?±?35.0 μg m^?3 during the sampling period. The annual concentration of the total quantified elements was 2459.5?±?1789.8 ng m^?3, with relatively higher values in winter (3334.9?±?1690.9 ng m^?3) and spring (2809.4?±?2465.4 ng m^?3), in comparison of those in summer (1857.6?±?1162.7 ng m^?3) and autumn (1252.5?±?842.4 ng m^?3). Two elements of Ba (678.0?±?684.9 ng m^?3) and Zn (1264.8?±?725.3 ng m^?3) had greater fluctuations in concentrations and were accounted for more than 80% of the concentration of total quantified elements for each season. The concentrations of As in Xi’an exceeded the national standard in China. The enrichment factors (EFs) of most target heavy metals were high, exceeding 100 for Zn, As, Pb, Cd, and Hg, attributed to strong influences from human activities. Moreover, the largest enrichment of heavy metals in PM_2.5 occurred in Xi’an in winter. Principle component analysis (PCA) was applied for source apportionment. Coal and other fuel combustion, vehicle exhaust, and industrial activities were the three major pollution sources which contributed 43.6, 29.9, and 15.3%, respectively, of the total variance of PM_2.5. The health risk assessment showed that the non-cancer risks of As, Pb, and Cr for children were greater than 1, as well as of As for adults. The cancer risks of As and Cr were higher than 1?×?10^?6, indicating that the two elements had high potentials for both non-cancer and cancer risks. Our finding suggests that the PM_2.5 and related heavy metal pollutions in Xi’an were serious and posed high potential health risks. Effective controls and measures should be established in the studied area.     

Element differences and evaluation of the dietary intake from farmed oysters and mussels collected at different sites along the Croatian coast of the Adriatic Sea

Concentrations of the macroelements Ca, Mg, K and Na, microelements Cr, Cu, Fe, Mn and Zn and toxic metals As, Cd, Hg and Pb were determined in oysters and mussels collected at farming sites in the northern, central and south Adriatic Sea. Mean concentrations in oysters were (mg kg⁻¹): As 4.51, Ca 1551, Cd 1.44, Cu 53.6, Cr 0.23, Fe 45.9, Hg 0.047, K 2476, Mg 895, Mn 2.80, Na 7148, Pb 0.52, Zn 675. Mean values in mussels were (mg kg⁻¹): As 4.71, Ca 601, Cd 0.37, Cu 1.91, Cr 0.29, Fe 49.6, Hg 0.026, K 2246, Mg 1043, Mn 2.49, Na 7992, Pb 0.58, Zn 28.8. Significant differences in the concentrations of toxic metals and elements were found in oysters and mussels among farming sites. Obtained Cd, Hg and Pb concentration in oysters and mussels were lower than the limit levels set by the European Community. However, Cd concentration exceeded the limit level of 1 mg kg⁻¹ in oysters from all locations except Lim Bay. The estimated daily intakes (EDIs) indicate that oysters are a good source of Ca, Cu and Zn. The higher Cu and Zn concentrations than the toxicity reference values suggest a risk for consumers if larger quantities of oysters are consumed frequently.     

Bioecological Aspects and Heavy Metal Contamination of the Mollusk <Emphasis Type="Italic">Donax denticulatus</Emphasis> in the Colombian Caribbean Coastline

Donax denticulatus is a key mollusk for the ecology of sandy beaches, serving as a controller of organic matter, microorganisms, and as bioindicator of heavy metals pollution. The goal of this study was to characterize some ecological aspects of D. denticulatus and its relationship with the content of heavy metals in their tissue, in three beaches of the Caribbean coast of Colombia. The results showed the study populations were different in terms of morphological characteristics and density (Berrugas-Sucre?<?Cartagena-Bolívar?<?Riohacha-Guajira), but not in sexual proportion; although density was clearly related to beach occupancy by tourists. Analysis of metals revealed tissue concentrations varied depending on the location (Greater means: Hg?=?0.018?±?0.004 in Riohacha; Pb?=?0.110?±?0.060 in Berrugas and Cd?=?0.040?±?0.010 µg/g in Cartagena). No relationships were found between morphometric variables and heavy metals content. Principal components analysis highlighted Riohacha for presenting differences respecting to Bocagrande and Berrugas in terms of physicochemical water parameters such as pH, temperature, salinity, dissolved oxygen and conductivity. Results suggest tourism rather than environmental pollution could be a sensitive factor for biota survival in Caribbean beaches.     

Uptake and Distribution of Trace Elements in Dominant Mangrove Plants of the Indian Sundarban Wetland

Absorption, accumulation and translocation of 12 trace elements in nine dominant mangrove plants in the Indian Sundarban Wetland revealed both organ-specific and site-specific characteristics. An overall enrichment of elements was recorded in rhizosediment, exceeding the prescribed effects range-low (ER-L) of consensus based sediment quality guidelines (SQGs) for Cu and Pb. Avicennia officinalis, A. alba, Ceriops decandra and Excoecaria agallocha exhibited unique potential for accumulating Al, Cd, Co, Cr, Cu, Ni, Mn and Zn and could be considered efficient accumulators. Maximum element accumulation in trunk bark (As 6.16, Cr 49.9, Co 2.67, Cu 91.00 and Zn 85.5 mg kg^?1) and root/pneumatophore (Al 1000 and Fe 2430 mg kg^?1) was recorded. Maximum bioconcentration factor (6.23) in A. officinalis and translocation factor (17.5 for Mn) in C. decandra distinguished their phytoremediation capacity. These halophytes could be used for trace element phytoremediation in stressed sites of Sundarban.     

A Preliminary Investigation on Metal Bioaccumulation by <Emphasis Type="Italic">Perenniporia fraxinea</Emphasis>

The lignicolous macrofungus Perenniporia fraxinea has drawn increased attention due to its role as a pathogen of ornamentals in urban sites. The present study investigated the bioaccumulation of heavy metals by P. fraxinea. Sporophores were collected from urban and suburban areas in Pavia (Northern Italy) and analyzed for metals content (Cd, Hg, Pb, Ni, Cr, Cu, Fe, Mn, Zn) by inductively coupled plasma mass spectrometer and inductively coupled plasma optical emission spectroscopy, after microwave acidic digestion. On the basis of the obtained results the potential bioaccumulation capability of P. fraxinea was investigated. The isolates were grown in a culture medium enriched with different concentrations of Cd and Hg, chosen as probes of environmental pollution, and Cu for comparison. As P. fraxinea grows in the presence of Cd, Hg and Cu, it seems to be a potential tool in environmental monitoring.     

Horizontal and Vertical Distribution of Lead,Cadmium, and Zinc in Farmlands Around a Lead-Contaminated Goldmine in Zamfara,Northern Nigeria

This study was undertaken to evaluate the vertical and horizontal distribution of lead (Pb), cadmium (Cd), and zinc (Zn) in farmlands around a Pb-contaminated goldmine. Total concentrations of Pb and Cd recorded were at maximum values of 2,246.55 and 68.7 mg kg^?1, respectively; these are greater than the threshold values for Pb (300 mg kg^?1) and Cd (3 mg kg^?1). However, the concentration of Zn was within acceptable limits (300 mg kg^?1). Down the soil profile, concentrations of Pb, Cd, and Zn showed two peaks; these were attributed to facilitated transport and ground-water enrichment. Incubation of the soil samples with glucose indicated low microbial process(es), which could be due to the increased levels of Pb and Cd. Factor analysis showed a close association of Pb and Cd with the soil-exchange complex with a possibility of these heavy metals replacing Ca and other divalent cations in the soil-exchange site. This will, however, increase the risk of Pb and Cd leaching and uptake by plants. Although the metals were more associated with resistant soil fraction (sand), which also indicates their geogenic origin, chemical weathering under the influence of pH could release these metals into the soil-exchange site.     

Respiratory deposition and health risk of inhalation of particle-bound heavy metals in the carbon black feeding area of a tire manufacturer

The health effects of metal-containing carbon black (CB) particles obtained from the CB feeding area of a tire manufacturing plant were investigated. Atmospheric samples were collected over 24 h for 20 working days in 2016 using the 12 impaction stages of micro-orifice uniform deposit impactor, and metal-containing particles were analyzed using an inductively coupled plasma optical emission spectrometer. The concentration of total particulate matter in the CB feeding area was 944.8 ± 456.4 μg/m³, and the most abundant elements in the samples include Zn (8622.0 ± 5679.0 ng/m³), Al (3113.3 ± 2017.1 ng/m³), and Fe (1519.1 ± 875.0 ng/m³). Carcinogenic metals (Cd, Co, Cr, and Ni) with the mass median diameter were incorporated in submicron particles. The mean total deposition flux in the head airway (HA) region was approximately 16–30 times higher than that in the tracheobronchial (TB) region and alveolar region (AR). The most abundant deposition flux of heavy metals in the AR and TB region was distributed in particles of less than 3.2 μm. The cancer risk presented by carcinogenic metals (Cd, Co, Cr, and Ni) in total particles to CB feeding workers ranged from 5.52 × 10^?4 to 5.65 × 10^?2, which is substantially higher than the acceptable cancer risk range 10^?6–10^?4. In particular, the cancer risk presented by these four metals in ultrafine particles (UFPs) exceeded the 10^?6 benchmark level. These results demonstrate the high health risk presented by particle-bound heavy metals to workers in a CB feeding area via inhalation exposure.     

Uptake of Urea Nitrogen by <Emphasis Type="Italic">Oocystis borgei</Emphasis> in Prawn <Emphasis Type="Italic">(Litopenaeus vannamei)</Emphasis> Aquaculture Ponds

The goal of this study was to assess the rate of urea nitrogen uptake (ρ) by Oocystis borgei and the relationship between environmental factors and ρ. Light intensity, temperature, pH, salinity, and algal concentration, were used to construct an empirical model. The results showed that light intensity, algal concentration, pH and salinity had significant effects on ρ, and the optimal combination of environmental conditions for ρ was a temperature of 25°C, pH of 7.0, light intensity of 81 µmol m^?2 s^?1, salinity of 15‰, and algal concentration of 4.5?×?10⁸ cell L^?1–5.5?×?10⁸ cell L^?1. The model equation was ρ?=?2?×?10^?5?×?(A^0.363B^0.783C^0.045D^?0.503E)?+?0.0017, with a coefficient of determination (R²) of 0.83. No significant difference in variance was observed between the model-predicted values and the measured values (F?=?0.238, p?>?0.05), which demonstrated the high fitting degree of the simulation equation. This study provided valuable insight into the reduction of urea nitrogen levels in aquaculture water by O. borgei.     

Heavy Metal Tolerance in Metal Hyperaccumulator Plant, Salvinia natans

Metal tolerance capacity of Salvinia natans, a metal hyperaccumulator, was evaluated. Plants were exposed to 10, 30 and 50 mg L^?1 of Zn, Cd, Co, Cr, Fe, Cu, Pb, and Ni. Plant biomass, photosynthetic efficiency, quantum yield, photochemical quenching, electron transport rate and elemental (%C, H and N) constitution remained unaffected in Salvinia exposed to 30 mg L^?1 of heavy metals, except for Cu and Zn exposed plants, where significant reductions were noted in some of the measured parameters. However, a significant decline was noted in most of the measured parameters in plants exposed to 50 mg L^?1 of metal concentration. Results suggest that Salvinia has fairly high levels of tolerance to all the metals tested, but the level of tolerance varied from metal to metal.