Level,pattern, and risk assessment of the selected soil trace metals in the calcareous-cultivated Vertisols

Dynamics and distribution pattern of trace metals in agricultural lands are an increasing concern due to potential risks to the environment and human health. To ascertain more knowledge of this aspect, the fractions of total and available Fe, Mn, Zn, Cu, and Cd belonging to Vertisols under intensive cultivation and adjoining uncultivated soils were investigated. The order of abundance of metals in both cultivated and uncultivated soils was Fe?>?Mn?>?Cu?>?Zn?>?Cd and Fe?>?Mn?>?Zn?>?Cu?>?Cd for both available and total fraction, respectively. A relative enrichment was observed in the value of diethylene-triamine pentaacetic acid-extractable Fe (1.2–201%), Mn (2–31%), Cu (1–40%), and Cd (21–45%) as well as total fraction of Zn (3–17%), Cu (12–32%), and Cd (42–108%) after intensive cropping, which can be contributed to repeated application of agrochemical inputs and manure over long time. The values of RI (potential ecological risk) showed that cultivation caused a low potential ecological risk (33.3% of the soil samples) to moderate potential ecological risk (66.7% of the soil samples) in the study region and that cadmium made up 88%, on average, of the RI value.     

Geochemical distribution,bioavailability and potential toxicity of some trace metals in a complex micro-tidal estuary,Southwest India

The spatial and temporal variations of some trace metals in the surface sediments of Cochin Estuary were analyzed along with their geochemical associations to identify the possible sources, bioavailability and the health risks posed by them. The dominance of kaolinite and suggested that clay minerals distribution is influenced by sediment sorting. Total metal analysis revealed enrichment for Cd, Pb and Zn due to anthropogenic activities. The speciation analysis established that notwithstanding the large availability, carbonate as well as organic and sulfides bound fractions showed negligible associations with most of the metals. Hydrous Fe–Mn oxides appeared to play a major role in controlling the fate and transport of these metals in the sediments of Cochin Estuary. Lower contribution of the residual fractions for Cd (21%–26%), Pb (<60%) and Zn (24%–42%) indicated an obvious increase of other geochemical fractions. Risk assessment analysis revealed that regardless of total concentration, none of the analyzed metals were at safe levels in the estuary as appreciable percentages were found to be associated with mobile geochemical forms. The speciation study conspicuously established that the metals originating from non-geogenic sources are largely associated with the labile fractions and hence are more detrimental to the aquatic biota.     

A screening of liver,kidney, and thyroid gland morphology in organochlorine-contaminated glaucous gulls (Larus hyperboreus) from Svalbard

Concentrations of organochlorine (OC) contaminants and histomorphology of liver, kidney, and thyroid tissues were studied in nine adult and one subadult glaucous gulls (Larus hyperboreus) collected at Svalbard on 2 August 2011. Concentrations of liver polychlorinated biphenyls (PCB; range: 150–2820?ng?g^?1 ww), dichlorodiphenyltrichloroethane (DDT; range: 58–724?ng?g^?1 ww), and chlordanes (CHL; range: 11–126?ng?g^?1 ww) dominated the OC profile followed by hexachlorobenzene (HCB; range: 11–42?ng?g^?1 ww), mirex (range: 2–52?ng?g^?1 ww), and β-hexachlorocyclohexane (β-HCH; range: 1–7?ng?g^?1 ww). Histological examination of the liver showed mononuclear cell infiltrations and granulomas in 10 and 6 gulls, respectively, while intense intrahepatic lipid accumulation (steatosis) was found in two and focal necrosis in one gull. In kidney, glomerular sclerosis and adhesions was found in five and one gull, respectively. Thickening of the glomerular basement membranes and tubular necrosis was found in four and seven gulls, respectively, while mononuclear cell infiltrations were found in two individuals. In the thyroid gland, a high density of small follicles accompanied by follicular epithelial cell proliferation was observed in five glaucous gulls. Gulls with hepatic steatosis had significantly higher ΣDDT levels than the gulls without hepatic steatosis and a similar trend was found for ΣPCB. When normalizing OC concentrations for lipid content in liver, gulls with lipid granulomas had significantly lower β-HCH and significantly higher mirex levels, respectively, than gulls without lipid granulomas. Also; gulls with thickening of the glomerular basement membranes had non-significantly higher ΣPCB levels than gulls without. The histological findings were similar to those of controlled laboratory studies and OC-contaminated wildlife (e.g., polar bears; Ursus maritimus) and the data of this study therefore suggest that OC exposure may be a co-factor in the development of organ alterations in glaucous gulls. However, other environmental factors such as age, element exposure, and infectious micropathogens cannot be ruled out as co-factors, and it is uncertain if the tissue changes found exert adverse health effects on the population of Svalbard glaucous gulls.     

Determination of the levels of selected metals in seeds,flowers and fruits of medicinal plants used for tapeworm treatment in Ethiopia

The level of accumulation of selected essential and non-essential metals, namely; Ca, Cu, Fe, Zn, Mn, Cd, Pb, and Cr have been investigated in the seeds, fruits, and flowers of some medicinal plants utilized for tapeworm treatment in Ethiopia and their respective soil samples. These include seed of Cucurbita maxima (Duba), fruit of Embelia abyssinica (Ankoko), flowers of Hagenia abyssinica (Kosso), and fruits of Rosa abyssinica (Kega) and their respective soil samples. A wet digestion procedure with a mixture of conc. HNO₃ and HClO₄ for the plant samples and a mixture of conc. HNO₃, HCl, and H₂O₂ for soil samples were used to solubilize the metals. Ca (1280–12,670?mg?kg^?1) was the predominant metal followed by Fe (104–420?mg?kg^?1), and Zn (18–185?mg?kg^?1) in all the plant materials except for Hagenia abyssinica flower from Hirna in which Mn (16–42?mg?kg^?1) followed by Fe. Among the non-essential toxic metals, Pb was not detected in Cucurbita maxima of Boji, Gedo and Hirna origins and in Rosa abyssinica of Hirna site. Similarly, Cr was not detected in Rosa abyssinica fruits of Boji and Gedo sites. The sampled soils were found to be between strongly acidic to weakly basic (pH: 4.7–7.1). In the soil samples, Ca (8528–18,900?mg?kg^?1) was the most abundant metal followed by Fe (417–912?mg?kg^?1), Zn (155–588?mg?kg^?1), Mn (54–220?mg?kg^?1), Cr (21–105. mg?kg^?1), Cu (11–58?mg?kg^?1), Pb (13–32?mg?kg^?1) and Cd (2.8–4.8?mg?kg^?1). The levels of most of the metals determined in the medicinal plants and the respective soil samples are in good agreement with those reported in the literature and the standards set for the soil by various legislative authorities.     

Persistent organochlorine pesticides,polychlorinated biphenyls,polybrominated diphenyl ethers in fish from coastal waters off Savannah,GA, USA

Contamination profiles of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined in six fish species from three selected regions along coastal waters off Savannah, GA, USA. Concentrations of PCBs were predominant (12–493 ng g^?1 lw) followed by PBDEs (10–337 ng g^?1 lw), OCPs such as DDTs (2.7–153 ng g^?1 lw), chlordanes (3.8–34 ng g^?1 lw), cyclodienes (<0.1–35 ng g^?1 lw), mirex (<0.1–8.6 ng g^?1 lw), γ-hexachlorocyclohexane (<0.1–1.4 ng g^?1 lw), and hexachlorobenzene (<0.1–0.68 ng g^?1 lw). The results indicated no region-specific difference in the contaminants however inter-species as well as intra-species differences were evident. Comparison of DDTs, PCBs, and PBDEs profiles in fish with those from other countries revealed that fish from coastal waters off Savannah contained relatively less concentrations of PCBs and chlorinated pesticides, while PBDE concentrations were comparable or even higher than fish samples from other regions. Polychlorinated biphenyl congeners and chlorinated pesticide tempoal trend data exhibited no increase of contamination levels. The levels of PCBs and chlorinated pesticides in fish from Savannah coastal waters were below the Food and Drug Administrations (FDA) established limits for human consumption.     

Polychlorinated-dibenzo-p-dioxins, -dibenzofurans and -dioxin-like polychlorinated biphenyls in aquatic organisms from lake Kasumigaura,Japan

Polychlorinated-dibenzo-p-dioxins (PCDDs), -dibenzofurans (PCDFs) and -dioxin-like polychlorinated biphenyls (DLPCBs) were determined in aquatic wildlife of Kasumigaura Lake (KUL), Japan from 1978 to 2001. Two plankton species elucidated several fold greater concentrations (2400–7800) than small tiger fish (310–6500), shrimp (160–1100), and three large fish namely, black bass (120–240), carp (94–120) and mullet (54) on pg/g fat. PCDD homologues were predominant accumulants with >68–<95% contribution and remaining was shared by PCDFs. Accumulation, non-ortho DLPCBs in plankton (3500–9200), shrimp (1600–8600) and small fish (2000–8800) and large fish (1300–3900) on ng/g fat basis were several orders magnitude greater than PCDD/DFs. The mono-ortho DLPCBs in large fish species were 23?000–83?000?ng/g fat and which it is accounted 94.3–95.9% the total dioxin-like PCBs accumulation. Temporal trends of PCDDs, PCDFs, non-ortho PCBs and TEQ in shrimp and small tiger fish were varied. The mullet had minimum toxic equivalency “TEQ” (14?pg?TEQ/g) followed by plankton Neomysis intermedia (25?pg?TEQ/g), small tiger fish (mean: 33, ranges 14–66?pg?TEQ/g), plankton Cyclopus vicinus (34?pg?TEQ/g), carp (mean: 35, ranges 32–38?pg?TEQ/g), shrimp (mean: 38, ranges 11–68?pg?TEQ/g) and black bass (mean: 59, ranges 38–79?pg?TEQ/g) on fat basis. In all the samples, PCDD was predominant TEQ contributor followed by PCDFs and DLPCBs. The contribution of mono-ortho DLPCBs to the total TEQ was 0.52–0.92 in large fish.     

Seasonal variation assessment of impact of industrial effluents on physicochemical parameters of surface water of River Challawa,Kano, Nigeria

The physicochemical characteristics of the River Challawa in the Kumbotso Local Government Area of Kano State were studied across four seasons (warm and dry, cold and dry, hot and dry, and warm and wet seasons) between October 2006 and August 2008. Physicochemical parameters like pH, electrical conductivity (EC), total dissolved solids (TDSs), total suspended solids (TSS), alkalinity, turbidity, hardness, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), ammonia, chloride, nitrate, sulfate, and phosphate were analyzed and compared with standard permissible limits. The mean range of parameters determined across the seasons revealed: 8.36–8.59 for pH; 209.57–335.27 µS cm^?1 for EC; 134.05–208.5 mg L^?1 for TDS; 182.4–273.45 mg L^?1 for TSS; 125.3–276.07 mg L^?1 for hardness; 16.11–40 mg L^?1 of CaCO₃ for alkalinity; 2.76–3.78 mg L^?1 for DO; 1.9–43.33 mg L^?1 for BOD; 231.67–310.06 mg L^?1 for COD; 221.67–441.67 mg L^?1 for turbidity; 17.98–35.89 mg L^?1 for chloride; 5.12–8.89 mg L^?1 for nitrate; 37–558.83 mg L^?1 for sulfate; and 0.47–0.81 mg L^?1 for phosphate. Data showed that all parameters determined were significantly different among the various sampled sites across seasons. With the exception of COD, EC, and phosphate, all other parameters determined were within the WHO and USPH standard limits.     

Levels and distribution of trace metals in surface sediments from Kongsfjorden, Svalbard, Norwegian Arctic

Trace metal contents (Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn) have been measured in 27 surface sediment samples collected from Kongsfjorden, Svalbard, Norwegian Arctic. The analyses yielded concentration values (in mg kg^?1) of 0.13–0.63 for Cd, 11.89–21.90 for Co, 48.65–81.84 for Cr, 21.26–36.60 for Cu, 299.59–683.48 for Mn, 22.43–35.39 for Ni, 10.68–36.59 for Pb, 50.28–199.07 for Zn and 8.09–65.34 for Hg (in ng g^?1), respectively. Relative cumulative frequency method has been used to define the baseline values of these metals, which (in mg kg^?1) were 0.14 for Cd, 13.56 for Co, 57.86 for Cr, 25.14 for Cu, 364.08 for Mn, 26.22 for Ni, 17.46 for Pb, 70.49 for Zn and 9.76 for Hg (in ng g^?1), respectively. The enrichment factor analysis indicated that Hg showed some extent of anthropogenic pollution, while Pb, Zn and Cd showed limited anthropogenic contamination in the study areas.     

Distributions of total metals in the surface sediments of the Bandirma and Erdek Gulfs,Marmara Sea,Turkey

The aim of this study is to determine the contents of aluminum, iron, manganese, nickel, copper, zinc, chromium, cadmium, lead, and mercury in sediments at 1–30?m depths of the Band?rma and Erdek Gulfs in the Southern Inner Shelf of the Marmara Sea. Sediment samples were collected from different depths (1?m, 5?m, 10?m, 20?m, 30?m) at each region in February 2008. Primary hydrographic conditions, such as temperature (6.6–14.5°C), salinity (22.6–26.875 psu), percentage of dissolved oxygen saturation (35–83 %), and pH (8.0–8.4) were recorded for each sampling point. Moreover the total organic carbon (0.5–2.9%) and the total calcium carbonate contents (0.8–60%) of sediment samples were determined. In surface sediments of both gulfs, Pb (21–62?mg?kg^?1) and Cd (0.52–0.86?mg?kg^?1) contents were determined to be higher than the shale average (Pb 20?mg?kg^?1, Cd 0.2?mg?kg^?1) while the other metal contents were measured to be lower in general. On the other hand, generally Hg (0.06–1.1?mg?kg^?1) contents were higher than the shale average (0.3?mg?kg^?1)at all of the examined stations in the Band?rma Gulf and lower than the shale average in the Erdek Gulf.     

Effect of ultra-sonication and its use with sodium hypochlorite as antifouling method against <Emphasis Type="Italic">Mytilus edulis</Emphasis> larvae and mussel

Biofouling is a stubborn problem in cooling systems where using raw water from lakes, rivers, and sea. The effect of ultrasound and its sequential application with sodium hypochlorite (chlorination) upon marine bivalve Mytilus edulis (blue mussel), a massive fouling organism, has been studied and discussed here. The results obtained from the work carried out have shown that 42 kHz ultrasound is better than 28 kHz in accordance with veliger larvae mortality. The 42 kHz ultrasound has enhanced the mortality rate of veliger larvae than only free-residual chlorination up to 99%. On the other side, the 14-mm size mussel was less resistance than 25-mm size mussel to 42 kHz ultrasonication, among the studied two sizes (14 and 25 mm) of the blue mussel. Lethal time (100%) have decreased by 1–12% used for the sequential action of 42 kHz ultrasonic followed by free-residual chlorination compare with only free-residual chlorination treatment. The obtained results are put forward that the application of ultra-sonication before chlorination can reduce the mussel extinct time up to 12%. Obviously, this result will provide a possible use of ultra-sonication with famous chlorination antifouling treatment and eventually can decrease the chlorine exposure time and dose. It could discharge low chlorine by-products that may provide an environment friendly way.     

Phosphorus fractionation in surface water and sediments of industrially polluted freshwater reservoir,India

Industrial pollutions are responsible for alterations in biogeochemical cycling of phosphorus (P) in freshwater systems. The objectives of the present study were to quantify the major P forms and assess the relationship between P fractions in water and surface sediments of Govind Ballabh Pant Sagar (GBPS) reservoir, India. Surface water samples (n?=?48) and surface sediment samples (n?=?48) were collected from six regions of GBPS reservoir in December 2014. The results showed that total particulate phosphorus (TPP) and total dissolved phosphorus (TDP) account for 45%–58% and 42%–55% of total phosphorus (TP) in the surface water. The authigenic-P was found to be more than 84% of the total P in surface sediments. The TPP showed a positive statistical relationship with sedimentary P fractions (authigenic-P, exch-P, and organic-P) indicated the impact of industrial pollution load on inorganic and organic P fractions in water and sediments of GBPS reservoir. The discriminant fraction analysis (DFA) revealed that the exch-P, Fe(III)-bound-P, detrital-P, organic-P, and TPP were sensitive indicators of P dynamics in the industrially polluted GBPS reservoir.     

Bioreduction of hexavalent chromium by Exiguobacterium indicum strain MW1 isolated from marine water of Paradip Port,Odisha, India

Hexavalent chromium-tolerant (1500?mg/L) bacterium MW1 was isolated from harbour water of Paradip Port and evaluated for Cr(VI) reduction potential. The isolate was identified as Exiguobacterium indicum by biochemical and 16S rRNA gene sequence methods. Salt tolerance of the bacterium was evaluated in a wide range of NaCl concentrations (0.5–13%, w/v). The Cr(VI) reduction of the strain was evaluated and optimised with varied Cr(VI) concentrations (100–1000?mg/L), pH (5.0–9.0), temperature (30–40°C) and shaking velocity (100–150?rpm) in two different minimal media (M9 and Acetate). Under optimised conditions, after 192?h of incubation nearly 92%, 50% and 46% reduction in the M9 minimal medium and 91%, 47% and 40% reduction in the acetate minimal medium were observed for 100, 500 and 1000?mg/L of Cr(VI), respectively. The exponential rate equation for Cr(VI) reduction yielded higher rate constant value, that is, 1.27?×?10^?2?h^?1 (M9) and 1.17?×?10^?2?h^?1 (Acetate) in case of 100?mg/L and became lower for 500 and 1000?mg/L Cr(VI) concentrations. Further, the association of bacterial cells with reduced product was ascertained by Fourier transform infrared spectrometer, UV–Vis–DRS and field-emission scanning electron microscope–energy-dispersive X-ray analyses. The above study suggests that the higher reducing ability of the marine bacterium E. indicum MW1 will be suitable for Cr(VI) reduction from saline effluents.     

Seasonal variation of heavy metals in sediment of Lake Ulansuhai,China

Sediment samples were collected from 10 sites in Lake Ulansuhai during summer and winter 2009 to reveal seasonal variations in sediment heavy metal levels. The geoaccumulation index (GI) was calculated to assess the severity of metal pollution. The GI values suggest that, in winter, the lake sediments were polluted slightly with Cu (GI=0.66–1.34), Zn (GI=0.59–1.35), Cr (GI=0.49–0.82) and Pb (GI=0.60–0.96), and moderately with Cd (GI=1.03–4.23). The degree of pollution was higher in winter than in summer. By contrast, the degree of pollution was higher in summer than in winter for Hg and As. Correlation analysis can be used to identify factors influencing seasonal variations in heavy metals. The concetrations of Cu, Zn, Pb, Cr and Cd were negatively correlated with water temperature and hydrodynamic conditions, but positively correlated with organic matter concentration in the sediments and with a sediment particle size of<63 μm (p<0.01). Meanwhile, Hg and As concentrations were affected by redox state and salinity. Among the metals tested, Hg and Cd posed a more serious pollution risk.     

Identification of urinary metabolites in rats administered the fluorine-containing pyrethroids metofluthrin,profluthrin, and transfluthrin

The major metabolites in urine of rats administered the fluorine-containing pyrethroids transfluthrin, profluthrin, and metofluthrin, which are used widely recently as mosquito repellents or mothproof repellents, were identified to establish biological indexes for evaluating the absorption amounts of these pyrethroids in the general population. A single dose of 300?mg?kg^?1 body weight of each pyrethroid was separately administered intraperitoneally to male Sprague-Dawley rats and urine samples were collected until 24 hours after the administration. The metabolites identified by gas chromatography-mass spectrometry were as follows: 2,3,5,6-tetrafluorobenzyl alcohol, 2,3,5,6-tetrafluorobenzoic acid, and 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (DCCA) for transfluthrin; 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol, 4-methyl-2,3,5,6-tetrafluorobenzoic acid, 4-hydroxymethyl-2,3,5,6-tetrafluorobenzyl alcohol (HOCH₂–FB–Al), and 2,2-dimethyl-3-(1-propenyl)-cyclopropanecarboxylic acid (MCA) for profluthrin; 4-methoxymethyl-2,3,5,6-tetrafluorobenzyl alcohol, HOCH₂–FB–Al and MCA for metofluthrin. In addition, several compounds estimated to be metabolites were detected as follows: hydroxylated DCCA and its lactone for transfluthrin; 4-hydroxymethyl-2,3,5,6-tetrafluorobenzoic acid (HOCH₂–FB–Ac), hydroxylated MCA and its lactone for profluthrin; 4-methoxymethyl-2,3,5,6-tetrafluorobenzoic acid, HOCH₂–FB–Ac, hydroxylated MCA, and its lactone for metofluthrin. The pyrethroids administered underwent metabolic reactions such as ester hydrolysis and oxidation, and most of the metabolites were excreted as their conjugates into urine. These findings should be useful as basic data for evaluating the health effects of exposure to pyrethroids for the general population.     

Fractionation of trace metals (Mn,Zn, Cu,Pb) in Red Sea sediments,Gulf of Aden,Yemen

A sequential extraction technique was applied to estimate the chemical association of Mn, Zn, Cu and Pb in five chemical phases (exchangeable, carbonate, Fe–Mn oxides, organic matter and residual) in sediments of the Gulf of Aden, Yemen. The results indicated that a higher level of Mn was associated with the residual fraction (natural sources) than the non-residual fraction (anthropogenic sources). Zn fractionations revealed that it was associated more with Fe–Mn oxides and organic fractions than exchangeable and carbonate fractions. Most of the Cu was present in the residual form (60–72%) except for in the main port area (zone III), where it was associated with the organic phase (77% of the total Cu content, the organic matter content was 5%). Similarly, most Pb was bound in the residual fraction (56–71%) except the main port area where ～ 62% of the total Pb was bound in non-residual fractions. It was also found that the Pb concentration in the exchangeable fraction was very high compared with other metals. The risk assessment code for the metals showed a low risk for Zn and Cu, but low to medium risk for Mn. Fractionation of Pb showed medium risk at most of the regions except at the eastern area, which revealed a high risk for the aquatic environment.     

Seasonal cycle of sexual reproduction of the Mediterranean soft coral Alcyonium acaule (Anthozoa, Octocorallia)

Alcyonium acaule (Cnidaria, Octocorallia) is a common, hard-bottom soft coral in the northwestern Mediterranean Sea. This study describes sexual reproduction and the gamete development cycle of this soft coral. A population at 15–18 m depth in the Marine Protected Area of the Medes Islands (42º02′55″ N, 3º13′30″ E) was sampled from July 1994–August 1995. A. acaule is gonochoristic and a surface brooder, spawning once a year in early summer. The mean diameter of ripe spermatic sacs was 400 ± 91 (SD) μm, and the mean diameter of mature oocytes was 473 ± 37 (SD) μm. There were 30 spermatic sacs polyp^?1 in males and 14 oocytes polyp^?1 in females. Different phases of gametogenesis in female and male colonies were examined separately with respect to seasonal changes in bottom temperature and solar irradiance. The data suggest that the relatively constant temperatures in January–April are probably not related to oocyte maturation, but that rising temperatures in May could affect sperm maturation. Rapidly increasing solar irradiance in March may be the trigger for vitellogenesis and oocyte maturation, although the mechanism for this in anthozoans is not understood.     

Distribution of heavy metals in soil and accumulation in plants at an agricultural area of Umudike,Nigeria

This study assessed the distribution of heavy metals in soil and their subsequent accumulation in plants at a site at Umudike, Nigeria, that had been contaminated by agrochemicals. Soil and plant samples were analysed for zinc (Zn), chromium (Cr) and cadmium (Cd). The highest concentrations of Zn (251.50 mg/kg) and Cd (61.33 mg/kg) were obtained at a soil depth of 0–10 cm. The highest concentrations of Zn (16.52 mg/kg), Cd (27.12 mg/kg) and Cr (164.07 mg/kg) were accumulated by Baphia nitida. The levels of Cd, Cr and Zn in soil were 27.97–61.33, 24.97–45.43 and 148.57–251.50 mg/kg, and their concentrations in B. nitida were 16.18–27.13, 97.99–164.07 and 0.10–16.52 mg/kg, respectively. There were significant correlations between Cd and Cr and Cd and Zn in soil, as well as between Cd and Cr in plants. The concentration of Cd in soil reflected a state of pollution relative to Dutch criteria for soil and the FAO/WHO Codex Alimentarius Commission.     

Endocrine-disrupting chemicals in the Pearl River Delta and coastal environment: sources,transfer, and implications

A study was conducted to investigate the occurrence and behavior of six endocrine-disrupting chemicals (EDCs) in sewage, river water, and seawater from the Pearl River Delta (PRD). The six EDCs under study were 4-nonylphenol (NP), bisphenol A (BPA), 17α-ethynylestradiol (EE2), estrone (E2), 17β-estradiol (E2), and estriol (E3). These EDCs, predominated by BPA, were found in high levels in the influents and the effluents of sewage treatment plants in the area. The relatively high concentrations (0.23–625 ng/L) of the EDCs detected in the receiving river water suggested that the untreated sewage discharge was a major contributor. The EDCs detected in eight outlets of the Pear River and the Pear River Estuary were in the ranges of 1.2–234 and 0.2–178 ng/L, respectively. The estrogen equivalents in the aquatic environments under study ranged from 0.08 to 4.5 ng/L, with E1 and EE2 being the two predominant contributors. As the fluxes of the EDCs from the PRD region to the nearby ocean are over 500 tons each year, the results of this study point to the potential that Pearl River is a significant source of the EDCs to the local environment there.     

Preparation and characterization of calcium alginate-based composite adsorbents for the removal of Cd,Hg, and Pb ions from aqueous solution

Composite adsorbent materials containing calcium alginate, clinoptilolite, and coal-derived humic acid were prepared. Humic acid (HA), clinoptilolite (CL), alginate (AL), alginate-entrapped humic acid (AL/HA), clinoptilolite (AL/CL), and humic acid/clinoptilolite (AL/HA/CL) samples were characterized. The effectiveness of the samples as adsorbents for the removal of cadmium (Cd), mercury (Hg), and lead (Pb) were studied in a series of batch-adsorption experiments. For the AL, AL/HA, AL/CL, and AL/HA/CL adsorbents, uptake versus time data were evaluated using two kinetic models, a linear and a non-linear pseudo-first-order and a pseudo-second-order model. The data for each metal ion on all adsorbents showed good correspondence with the pseudo-second-order kinetic model. The equilibrium data were fitted to Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherm models. The results show that a non-linear method seems more appropriate for obtaining isotherm parameters. The non-linear Freundlich and Langmuir models for Pb and Hg produced a best fit with high R ² value (0.99). For HA adsorbent, the equilibrium data for Cd removal better fit to the non-linear Dubinin–Radushkevich isotherm.     

Effects of three low-molecular-weight organic acids (LMWOAs) and pH on the mobilization of arsenic and heavy metals (Cu, Pb, and Zn) from mine tailings

Natural organic acids may play an important role in influencing the mobility of toxic contaminants in the environment. The mobilization of arsenic (As) and heavy metals from an oxidized Pb–Zn mine tailings sample in the presence of three low-molecular-weight organic acids, aspartic acid, cysteine, and succinic acid, was investigated at a mass ratio of 10 mg organic additive/g mine tailings in this study. The effect of pH was also evaluated. The mine tailings sample, containing elevated levels of As (2,180 mg/kg), copper (Cu, 1,100 mg/kg), lead (Pb, 12,860 mg/kg), and zinc (Zn, 5,075 mg/kg), was collected from Bathurst, New Brunswick, Canada. It was found that the organic additives inhibited As and heavy metal mobilization under acidic conditions (at pH 3 or 5), but enhanced it under neutral to alkaline conditions (at pH above 7) through forming aqueous organic complexes. At pH 11, As, Cu, Pb, and Zn were mobilized mostly by the organic additives, 45, 46, 1,660, and 128 mg/kg by aspartic acid, 31, 28, 1,040, and 112 mg/kg by succinic acid, and 53, 38, 2,020, and 150 mg/kg by cysteine, respectively, whereas those by distilled water were 6, 16, 260, and 52 mg/kg, respectively. It was also found that the mobilization of As and the heavy metals was closely correlated, and both were closely correlated to Fe mobilization. Arsenic mobilization by the three LMWOAs was found to be consistent with the order of the stability of Fe–, Cu–, Pb–, and Zn–organic ligand complexes. The organic acids might be used potentially in the natural attenuation and remediation of As and heavy metal–contaminated sites.