Concentration Levels of Essential and Non-essential Metals in Ethiopian Khat (Catha edulis Forsk)

The levels of essential (Ca, Mg, Mn, Fe, Zn, Cr, Cu, and Co) and non-essential (Cd and Pb) metal in six different varieties of Ethiopian khat (Catha edulis Forsk, an evergreen stimulant plant) commonly consumed in the country and exported to the neighboring countries were determined by flame atomic absorption spectrometry. Known weight of oven-dried khat samples were wet-digested using 2 mL of (69–72%) HNO₃ and 2 mL of (70%) HClO₄ for 2 h and 30 min at variable temperature (120–270°C). The mineral contents in the digests were analyzed using flame atomic absorption spectrometer. The following concentrations ranges in fresh-weight basis were recorded in decreasing order: Ca (1,038–2,173 µg/g)?>?Mg (478.2–812.3 µg/g)?>?Fe (53.95–82.83 µg/g)?>?Zn (5.18–9.40 µg/g)?>?Mn (6.98–8.66 µg/g)?>?Cu (1.85–5.53 µg/g)?>?Cr (0.66–3.47 µg/g)?>?Co (0.41–0.80 µg/g). A wide variation in the mineral contents of khat from different region of Ethiopia was noticed. The toxic metals (Pb and Cd) were not detected in all the samples analyzed.     

Heavy metal accumulation in rice (Oryza sativa) near electronic waste dumps and related human health risk assessment

This research was conducted to assess heavy metal contamination in the environment and within Oryza sativa. The translocation factors (TFs) and bioaccumulation factors (BAFs) for heavy metals in O. sativa and estimated daily intake (EDI) and health risk index (HRI) were measured. The samples were analyzed for heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES). Pb and Cr concentrations in water samples within and near the electronic-waste dumping area exceeded water quality standards for surface water sources from the Pollution Control Department in the Ministry of Natural Resources and Environment of Thailand (PCD). The Pb concentration in soil samples within the area also exceeded soil quality standards for habitat and agriculture from PCD. Most of the metals were highly concentrated in roots, except for Mn which has the highest concentration in leaves. Pb concentrations in rice grains exceeded the FAO/WHO standard (0.2 mg/kg). The average TF values for heavy metals from the soil to roots, roots to stems, stems to leaves, and stems to grains were Mn > Pb > Ni > Cr, Mn > Cr > Ni > Pb, Ni > Pb > Mn > Cr, and Pb > Ni > Cr > Mn, respectively. The average BAF values in O. sativa were Mn > Ni > Pb > Cr. The EDI for Cr, Pb, Mn, and Ni via O. sativa consumption were 6.19, 6.02, 370.57, and 3.80 µg/kg/day, respectively. The HRI for Cr, Pb, Mn, and Ni via O. sativa consumption were 0.30, 1.50, 2.60, and 0.002, respectively.     

Phytoextraction of Ni,Pb and,Cd by duckweeds

Abstract

Heavy metals phytoextraction potential of swollen duckweed (Lemna gibba Linn.) and lesser duckweed (Lemna aequinoctialis Welw.) was determined under greenhouse conditions by exposing to untreated industrial/municipal effluent for a period of 21?days. The nickel (Ni), lead (Pb), and cadmium (Cd) concentrations in water samples were measured weekly and in plant biomass at the termination of experiments. Significant differences (p?<?0.05) between initial and final physicochemical parameters and in heavy metal concentrations of plant and water samples were observed. Periodically measured metal concentrations in mediums revealed that removal percentage was dependent on initial Ni (2.15?mg L^?1), Pb (1.51?mg L^?1), and Cd (0.74?mg L^?1) concentrations. The final metal removal percentages were in the sequence of Ni (97%) > Pb (94%) > Cd (90%) when treated with Lemna gibba L. as compared to control (9–12% reduction). High biomass production of Lemna gibba L. resulted in a large metal reduction in the growth medium and the total plant metal contents were in the sequence of Ni (427?µg) > Pb (293?µg) > Cd (105?µg). The lesser duckweed did not survive under experimental conditions. Based on these results, we concluded that Lemna gibba L. is a good candidate for phytoremediation of wastewater.     

Chemical speciation and health risks of airborne heavy metals around an industrial community in Nigeria

Abstract

Quantification of PM_2.5 (particulate matter <2.5?µm) bound heavy metals and their potential health risks were carried out around a cement manufacturing company in Ewekoro, Nigeria. The PM_2.5 samples were collected using Environtech gravimetric sampler. A four-staged sequential extraction procedure was used to fractionate PM_2.5 bound chromium (Cr), lead (Pb), aluminum (Al), copper (Cu), and silver (Ag), and further analyzed using inductively coupled plasma mass spectrometry. Chemical speciation results reveal bioavailable levels of Pb (4.05?µg/m³), Cr (10.75?µg/m³), Al (16.47?µg/m³), Cu (4.38E-01?µg/m³), and Ag (1.22E-02?µg/m³) in the airborne particulates. Pb and Cr levels exceeded the World Health Organization allowable limit of 0.5 and 2.5E-05?µg/m³, respectively. The labile phases showed strong indication of the presence of Cr and Cu metal. Excess cancer risks exposure for adults, outdoor workers and children were higher than the acceptable risk target level of 1E-06. Non-carcinogenic health risk estimated using hazard quotients (HQs) and hazard indices (HIs) showed ingestion route within the safe level of HI <1 implying no adverse effect while inhalation route exceeded the safe level for all receptors. Enforcement of pollution control by authorized agencies, and screening of greenbelts as sinks for air pollutants is strongly recommended.     

Using tree leaves and barks collected from contaminated and uncontaminated areas as indicators of air metallic pollution

Abstract

The aim of this study was to show the usefulness of woody species in assessing air pollution by cadmium, copper, lead, and zinc. For this, washed leaves, unwashed leaves, and barks of a coniferous species (Cupressus sempervirens var. fastigiata) and a broadleaved one (Eucalyptus cladocalyx F. Muell) were analyzed for cadmium, copper, lead and zinc contents. A transect sampling approach was carried out during spring 2016. Fifty stations were selected along an intensive traffic road, and three in a control area. The results showed that the highest concentrations were recorded in barks for copper (21.86?µg/g, 23.33?µg/g) and lead (14.53?µg/g, 63.33?µg/g), and in unwashed leaves for cadmium (0.57?µg/g, 1.19?µg/g) and zinc (48.94?µg/g, 47.6?µg/g) for E. cladocalyx F. Muell, and C. sempervirens var. fastigiata, respectively. Lead and zinc are the most accumulated metals compared to cadmium and copper in all samples. The studied metal contents in urban area were significantly higher than that of the control one. This represents that traffic road has influenced the metals contamination of the surrounding area. Results of the bioconcentration factor (BCF) for both species indicate that the studied species could be used as biomonitors to identify ecological problems and to predict effect on wildlife habitats. The highest values of metal accumulation index (MAI) indicate the effectiveness of these trees for controlling the air metals in the polluted areas. Result shows too that the studied species could be used for phytoextraction of heavy metals from the polluted soils and/or air.     

Induction of non-protein thiols and phytochelatins by cadmium in Eichhornia crassipes

Abstract

Impact of root Cd concentration on production of cysteine, non-protein thiols (NP-SH), glutathione (GSH), reduced glutathione (GSSG), and phytochelatins (PCs) in Eichhornia crassipes exposed to different dilutions of brass and electroplating industry effluent (25%, 50%, and 75%), and synthetic metal solutions of Cd alone (1, 2.5, and 3.5?ppm) and with Cr (1?ppm Cd + 1?ppm Cr, 2.5?ppm Cd + 3?ppm Cr, and 3.5?ppm Cd + 4?ppm Cr) was assessed in a 45?days study. Different treatments were used to understand and compare differential antioxidant defense response of plant under practical drainage (effluent) and experimental synthetic solutions. The production of NP-SH and cysteine was maximum under 2.5?ppm Cd + 3?ppm Cr treatments i.e., 1.78?µmol/g fw and 288?nmol/g fw, respectively. The content of GSH declined whereas that of GSSG increased progressively with exposure duration in all treatments. HPLC chromatograms revealed that the concentrations of PC2, PC3, and PC4 (248, 250, and 288?nmol-SH equiv.g^?1 fw, respectively) were maximum under 1?ppm Cd, 1?ppm Cd + 1?ppm Cr, and 2.5?ppm Cd + 3?ppm Cr treatments, respectively. PC2, PC3, and PC4 concentrations increased with Cd accumulation in the range 812–1354?µg/g dry wt, 1354–2032?µg/g dry wt and 2032–3200?µg/g dry wt, respectively. Thus, the study establishes a direct proportionality relationship between concentration/length of phytochelatins and root Cd concentrations, upto threshold limits, in E. crassipes.     

Heavy metal accumulation in frogs surrounding an e-waste dump site and human health risk assessment

Abstract

This study was performed heavy metals (As, Cd, Cr, and Pb) in water, soil and frogs around an electronic-waste dump site. The bioaccumulation factors (BAFs) of heavy metals in three frog species and potential human health risks were assessed. Heavy metals were analyzed using inductively coupled plasma-optical emission spectrometry. The Cd and Pb concentrations in water samples and As and Pb concentrations in soil samples from within the e-waste dump site exceeded the standards. The heavy metal concentrations in the muscles of three frog species were as follows: Cr?>?Pb?>?As?>?Cd, and there were no significant differences among frog species except in the case of Pb (p?<?0.05). Only the Cr concentrations exceeded the food quality standards. The relative order of the BAFs for heavy metals in frogs as a result of uptake from the water and soil was Cr?>?As?>?Pb?>?Cd and Cr?>?As?>?Cd?>?Pb, respectively, which indicated that the uptake from water was greater than that from the soil. The assessment of the health risk index and carcinogenic risk (CR) indicated potential human health effects from As, Cr, and Pb via the consumption of frogs.     

Inhibition and eradication of Salmonella Typhimurium biofilm using P22 bacteriophage,EDTA and nisin

Abstract

P22 phage >10⁵ PFU ml^?1 could be used to inhibit Salmonella Typhimurium biofilm formation by 55–80%. Concentrations of EDTA >1.25?mM and concentrations of nisin >1,200?µg ml^?1 were also highly effective in reducing S. Typhimurium biofilm formation (≥96% and ≥95% reductions were observed, respectively). A synergistic effect was observed when EDTA and nisin were combined whereas P22 phage in combination with nisin had no synergistic impact on biofilm formation. Triple combination of P22 phage, EDTA and nisin could be also used to inhibit biofilm formation (≥93.2%) at a low phage titer (10² PFU ml^?1), and low EDTA (1.25?mM) and nisin (9.375?µg ml^?1) concentrations. A reduction of 70% in the mature biofilm was possible when 10⁷ PFU ml^?1 of P22 phage, 20?mM of EDTA and 150?μg ml^?1 of nisin were used in combination. This study revealed that it could be possible to reduce biofilm formation by S. Typhimurium by the use of P22 phage, EDTA and nisin, either alone or in combination. Although, removal of the mature biofilm was more difficult, the triple combination could be successfully used for mature biofilm of S. Typhimurium.     

Design,synthesis, antimicrobial evaluation and molecular docking studies of some new 2,3-dihydrothiazoles and 4-thiazolidinones containing sulfisoxazole

Microbial resistance to the available drugs poses a serious threat in modern medicine. We report the design, synthesis and in vitro antimicrobial evaluation of new functionalized 2,3-dihydrothiazoles and 4-thiazolidinones tagged with sulfisoxazole moiety. Compound 8d was most active against Bacillis subtilis (MIC, 0.007?µg/mL). Moreover, compounds 7c–d and 8c displayed significant activities against B. subtilis and Streptococcus pneumoniae (MIC, 0.03–0.06?µg/mL and 0.06–0.12?µg/mL versus ampicillin 0.24?µg/mL and 0.12?µg/mL; respectively). Compounds 7a and 7c–d were highly potent against Escherichia coli (MIC, 0.49–0.98?µg/mL versus gentamycin 1.95?µg/mL). On the other hand, compounds 7e and 9c were fourfolds more active than amphotericin B against Syncephalastrum racemosum. Molecular docking studies showed that the synthesized compounds could act as inhibitors for the dihydropteroate synthase enzyme (DHPS). This study is a platform for the future design of more potent antimicrobial agents.     

Potential health risk of heavy metals via consumption of rice and vegetables grown in the industrial areas of Bangladesh

Abstract

Heavy metals are toxic in nature, and their contamination in foodstuff is a matter of concern for human health. The present study was conducted to assess the concentrations of chromium, nickel, copper, arsenic, cadmium, and lead in rice and vegetables and their possible human health risks in Tangail district, Bangladesh. Metals were measured by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion system. The average values of Cr, Ni, Cu, As, Cd, and Pb in rice and vegetables were 16.26, 16.11, 13.99, 2.28, 1.86, and 7.93?mg/kg, respectively. The average metal concentration in rice and vegetable species was in the decreasing order of okra?>?chili?>?bitter gourd?>?papaya?>?brinjal?>?bean?>?bottle gourd?>?rice?>?cucumber?>?sponge gourd?>?Indian spinach. The estimated daily intake (EDI) values of all the metals except Cu were higher than the maximum tolerable daily intake (MTDI). The target hazard quotients (THQs) values of Ni, Cu, As, Cd, and Pb exceeded the threshold value of 1 through consumption of rice and vegetables, indicating significant health risks to both adult and children. The target carcinogenic risk (TR) of As and Pb through consumption of rice and vegetables was higher than the USEPA threshold level (10^?4). From the health point of view, this study clearly revealed that consumption of these contaminated rice and vegetables definitely poses carcinogenic and non-carcinogenic risks.     

Bioaccumulation of heavy metals in local edible plants near a municipal landfill and the related human health risk assessment

ABSTRACT

The increase in municipal solid waste generation, along with high concentrations of heavy metals in environments near municipal landfill, has led to human health hazards. This study investigated heavy metal contamination in water, sediment, and edible plants near a municipal landfill, including the bioaccumulation factor (BAF) and potential health risks. The heavy metal concentrations in the samples were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The concentrations of arsenic (As), lead (Pb), cadmium (Cd), and chromium (Cr) in water samples were not detected (ND), ND, 0.006 ± 0.01 mg/L, and ND, respectively, and in sediment samples, the concentrations were 1.19 ± 0.44, 3.20 ± 0.62, 0.46 ± 0.21, and 6.97 ± 0.34 mg/kg, respectively. The highest concentrations of As (5.03 ± 0.38), Pb (1.81 ± 0.37), and Cd (1.93 ± 0.13) were found in Marsilea crenata, whereas that of Cr (5.68 ± 0.79) was detected in Ipomoea aquatica. The Cr concentration in all plant species exceeded the standard for vegetables. The BAF values followed the heavy metal concentrations. All plant species have a low potential for accumulating Pb and Cr. The edible plants in this study area might cause health hazards to consumers from As, Pb, and Cd contamination.     

Design,synthesis and biological evaluation of 4-benzoyl-1-dichlorobenzoylthiosemicarbazides as potent Gram-positive antibacterial agents

Twelve 4-benzoyl-1-dichlorobenzoylthiosemicarbazides have been tested as potential antibacterials. All the compounds had MICs between 0.49 and 15.63?µg/ml toward Micrococcus luteus, Bacillus cereus, Bacillus subtilis and Staphylococcus epidermidis indicating, in most cases, equipotent or even more effective action than cefuroxime. In order to clarify if the observed antibacterial effects are universal, further research were undertaken to test inhibitory potency of two most potent compounds 3 and 11 on clinical isolates of Staphylococcus aureus. Compound 11 inhibited the growth of methicillin-sensitive S. aureus (MSSA) at MICs of 1.95–7.81?µg/ml, methicillin-resistant S. aureus (MRSA) at MICs of 0.49–1.95?µg/ml and MDR–MRSA at MIC of 0.98 and 3.90?µg/ml, respectively. Finally, inhibitory efficacy of 3 and 11 on planktonic cells and biofilms formation in clinical isolates of S. aureus and Haemophilus parainfluenzae was tested. The majority of cells in biofilm populations of MSSA and MRSA were eradicated at low level of 3, with MBICs in the range of 7.82–15.63?µg/ml.     

Fractionation,Source Identification and Risk Assessments for Heavy Metals in Soils near a Small-Scale Industrial Area (Çanakkale-Turkey)

Contamination of soils by heavy metals due to urbanization increases various environmental concerns. The objective of this research was to determine the potential sources of heavy metals in agricultural soils in the vicinity of a small-scale industrial area and to assess their environmental impacts. Soil samples were obtained from 15 different locations near a small industrial area in the Çanakkale province of Turkey. Heavy metal (Cd, Co, Cu, Ni, Pb, Zn) contents of soil samples were determined with four different geochemical fractions via a sequential extraction procedure. The results revealed that pseudo-total heavy metal concentrations were ordered in decreasing order as Zn > Pb > Cu > Ni > Co > Cd. Considering the results, Cd (1.95 ± 0.12 µg/g), Pb (39.21 ± 2.14 µg/g) and Zn (64.99 ± 8.16 µg/g) values were above the normal values specified for agricultural lands. The findings obtained from sequential extraction procedure showed that Cd (78%) and Pb (65%) existed mostly in mobile phases. Such mobile phases originated mostly from anthropogenic sources. These findings were also supported by chemometric analyses. Risk assessments pointed out that while Pb and Zn have moderate risks on the environment, Cd creates high risks.     

Interaction of Heavy Metals in Multimetal Biosorption by Galerina vittiformis from Soil

ABSTRACT Soil heavy metal contamination, a major threat due to industrialization, can be tackled by an efficient and economical process called bioremediation. Mushrooms are employed to accumulate heavy metals from soil due to their high metal accumulation potential and better adaptability. The bioaccumulation potential of Galerina vittiformis was already reported for individual metals. At natural conditions, since soil consists of more than one polluting metal, more focus has to be given to multimetal systems. In this study, multimetal accumulation potential was analyzed using central composite design, and the responses obtained were analyzed using response surface methodology. Heavy metals such as Cu(II), Cd(II), Cr(VI), Pb(II), and Zn(II) were subjected to biosorption at 10–250 mg/kg concentrations along with pH 5–8. The results showed that the preference of the organism for the five metals under study was in the order Pb(II) > Zn(II) > Cd(II) > Cu(II) > Cr(VI) at pH 6.5 under multimetal condition. The study also indicates that the metal interaction pattern in multimetal interaction is a property of their ionic radii. The response surface methodology clearly explains the effect of interaction of heavy metals on the accumulation potential of the organism using three-dimensional response plots. The present work suggests that the fungus Galerina vittiformis could be employed as a low-cost metal removal agent from heavy metal–polluted soil.     

Selenium in drinking water and cereal grains,and biomarkers of Se status in urine and fingernails of the Main Ethiopian Rift Valley population

BackgroundSelenium (Se) plays an important role in human health, yet Se overexposure or deficiency can lead to deleterious health effects. This study aims to determine the concentration of Se in drinking water and staple cereal grain (maize, wheat, and teff) samples from the Main Ethiopian Rift (MER) Valley, and correspondingly, assesses Se biomarkers and their status as measured in the urine and fingernails of 230 individuals living in 25 MER communities.MethodThe concentration of Se in drinking water and cereal grain (maize, wheat, and teff) samples, and urine and fingernail samples were measured using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Demographic, anthropometric, and elemental concentrations were described by their quartiles and mean ± standard deviations. The 5th and 95th percentiles were used to describe the concentrations Se biomarkers ranges. The Se biomarker distributions in different study communities were further characterized according to Se levels found in drinking water, sex, and age using ANOVA, and multivariate regression. We conducted a correlation analysis (with Pearson correlation coefficient) and fitted a regression to evaluate the associations between these variables.ResultsThe mean concentration of Se in the drinking water samples was 0.66 (range: 0.015–2.64 µg/L; n = 25), and all samples were below the threshold value of 10 μg/L for Se in drinking water set by the World Health Organiation (WHO). In Ethiopia, most rural communities rely on locally produced cereal grains. We found mean Se concentrations (µg/kg) of 357 ± 190 (n = 14), 289 ± 123 (n = 14), and 145 ± 100 (n = 14) in wheat, teff, and maize, respectively. Furthermore, Se concentrations in drinking water showed no significant correlation with biomarker measures, indicating that the primary source of dietary Se is likely from local foods including staple grains. The mean±SD (5th–95th percentiles) of Se concentrations in fingernails and urine among study subjects were 1022 ± 320 (624–1551 µg/kg), and 38 ± 30 (1.9–100 µg/L), respectively.ConclusionA sizeable share of study participants (31%) fell below the lower limits of what is considered the currently accepted Se range of 20–90 µg/L in urine, though relatively few (only 4%) had similarly low fingernail levels. On the other hand, none of the samples reached Se toxicity levels, and the biomarker levels in this study are comparable to results from other studies that find adequate Se. Our results show that Se toxicity or deficiency is unlikely in the study population.     

Utilization of Mentha aquatica L. for removal of fecal pathogens and heavy metals from water of Bosna river,Bosnia and Herzegovina

Abstract

The aim of the present study was to investigate the potential of Mentha aquatica L. for phytoremediation of water contaminated with heavy metals and fecal pathogens from Bosna river. The water was treated with M. aquatica for 5, 10, and 15 days consecutively after which it was analyzed for the various physicochemical and microbiological parameters.

The initial concentration of cadmium (Cd) ranged from 3.644 to 6.108?µg/l, while lead (Pb) varied between 0.1 and 1.386?µg/l. After treatment, M. aquatica accumulated significant amounts of cadmium (Cd) and lead (Pb) with the highest removal rates of 96.49% for Cd and 45.72% for Pb. Values of several physicochemical parameters were decreased after 15 days treatment period.

All water samples were analyzed for enumeration of aerobic heterotrophic bacteria, total coliforms, and fecal coliforms by the membrane filtration. Removal efficiency was greater than 80% for microbiological parameters. The concentration of heavy metals was determined in different plant parts and subsequently, the translocation factor was determined. In M. aquatica plant parts, concentrations of Pb and Cd were increased after 15 days of treatment. Our results demonstrated that M. aquatica could be good candidates for the removal of fecal pathogens and heavy metals present in surface water.     

Investigation of Metal levels in Artemisia herba-alba Medicinal Plant and Soil Samples Collected from Different Areas in Jordan Country

ABSTRACT

The concentrations of selected heavy metals including cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni) and iron (Fe) in stems and leaves of Artemisia herba-alba medicinal plant and soil samples were evaluated. Results showed that there in heavy metal concentrations of washed and unwashed parts of A. herba-alba from northern site (Irbid), Middle site (Al-Mafraq), and Souhern site (Ma’an) (P < .05). Moreover, the results of this study revealed that there is a correlation between heavy metal levels in medicinal plants and their concentrations in soil. Two standard reference materials of plant (SRM 1790a; spinach, CRM 281; ryegrass) and a standard reference material of soil (GBW 07406) were examined to validate the method used. There were good agreements between the measured values of these standard reference materials and their certified values. In addition to that high recoveries for tested elements were ranged between 91.7–97.7%, 90–96.6%, and 92.2–97.7% in (CRM281, ryegrass), (SRM1570a, spinach) and (GBW 04706, soil) respectively. It is reasonable to conclude that the variation in metal concentration from site to another site as well as from element to another element may be due to the different factors such as traf?c volumes, the wind directions, the soil nature, and the element behavior.

Based on the results obtained, the health authorities will take in consideration these useful information and direct the residents about the risk of these pollutants.     

Assessing Toxicant Effects in a Complex Estuary: A Case Study of Effects of Silver on Reproduction in the Bivalve,Potamocorbula amurensis,in San Francisco Bay

Contaminant exposures in natural systems can be highly variable. This variability is superimposed upon cyclic variability in biological processes. Together, these factors can confound determination of contaminant effects. Long term, multidisciplined studies with high frequency sampling can be effective in overcoming such obstacles. While studying trace metal contamination in the tissues of the clam, Potamocorbula amurensis, in the northern reach of San Francisco Bay, an episode of high Ag concentrations was identified (maximum of 5.5?µg g^?1) at two mid-estuary sites. High concentrations were not seen in clams up-estuary (maximum of 1.92?µg g^?1) from these sites and were reduced down-estuary (maximum of 2.67?µg g^?1). Silver is not common naturally in the environment, so its elevated presence is usually indicative of anthropogenic influences such as municipal and industrial discharge. Monthly sampling of reproductive status of clams characterized the reproductive cycle and differences in the patterns of reproductive activity that corresponded to changes in Ag tissue concentrations. The proportion of reproductive clams was less than 60% during periods when tissue concentrations were high (generally >2?µg g^?1). When tissue concentrations of Ag decreased (≤1?µg g^?1), the proportion of reproductive clams was 80 to 100%. A comparison between the annual proportion of reproductive clams and annual Ag tissue concentrations showed a significant negative correlation. No other measured environmental variables were correlated with reproductive impairment. The weight-of-evidence approach strongly supports a cause and effect relationship between Ag contamination and reduced reproductive activity in P. amurensis.     

Synthesis and in vitro antimicrobial activity of new 4-phenyl-5-methyl-4H-1,2,4-triazole-3-thione derivatives

This study presents the synthesis, spectral analysis and antimicrobial evaluation of a new series of substituted 1,2,4-triazole (5a–i) and 1,3,4-thiadiazole derivatives (9a, c, g, h). New compounds were obtained by cyclization reaction of acyl thiosemicarbazide derivatives in the presence of alkaline and acidic media. All synthesized compounds were screened for their in vitro antimicrobial activities. Nine of the compounds had potential activity against Gram-positive bacteria (MIC?=?3.91–500 µg/mL). Some compounds showed good activity especially against: Micrococcus luteus ATCC 10240 (MIC?=?3.91?31.25 µg/mL), Bacillus subtilis ATCC 6633 (MIC?=?15.63? 62.5 µg/mL), and Staphylococcus aureus ATCC 25923 (MIC?=?15.63?125 µg/mL).     

Source identification and risk assessment of heavy metals in road dust of steel industrial city (Anshan), Liaoning,Northeast China

Abstract

The purpose of the study was to acquire the source and evaluate the risk posed by heavy metals in road dust of steel industrial city (Anshan), Liaoning, Northeast China. Potential ecological risk index (RI), pollution index (PI) and geo-accumulation index (Igeo) were applied to evaluate the heavy metal pollution level, and the carcinogenic risk (RI) and hazard index (HI) were calculated to estimate the human health risk. The geographic information system maps clearly reveal the hot spots of heavy metal spatial distribution. Principle component analysis (PCA) and cluster analysis (CA) classified heavy metals into three groups. The metal Zn and Pb originate from the traffic emission, while Cd, Cr, Fe, Mn, Ni and Sb primarily come from industrial activities. These two pathways were the major source of heavy metals pollution by positive matrix factorization (PMF). The Igeo and PI values of heavy metals were decreased in the following order: Cd?>?Sb?>?Zn?>?Fe?>?Pb?>?Cu?>?Cr?>?Sn?>?Mn?>?Ni. The RI index showed the heavy metals were moderate to very high potential ecological risk. The HI values for children and adults presented a decreasing order of Cr?>?Pb?>?Ni?>?Cu?>?Cd?>?Zn. The HI also predicted a possibility of non-carcinogenic risk for children living in urban areas in comparison with adults.