The levels of Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn, Zn, Al and Fe were evaluated in indoor dusts from electronic workshops, cybercafés and offices in southern Nigeria. The study was aimed at providing ...information on the distribution patterns, and the associated risks that may arise from exposure of humans to these metals in indoor dusts from the three work environments. The dust samples were digested with aqua-regia and analyzed for the metal concentrations by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The metal concentrations (mg kg−1) in the indoor dusts from these work environments ranged from 0.2 to 20.5 Cd, 0.6–4810 Pb, 8.65–2210 Cr, 1.85–209 Ni, 6.75–2820 Cu, 0.25–19.6 Co, 22.7–597 Mn, 6.65–140 Ba, 43.3–7310 Zn, 1040–16,800 Al and 969–78,300 Fe. The metal distribution patterns in these dust samples followed the order: electronic workshops > cybercafés > offices. The concentrations of Cd, Pb and Cu in significant proportions of the dust samples from the electronic workshops and cybercafés surpassed their respective permissible limits in soils. The health risk assessment suggests considerable non-cancer risks arising from childhood contact with Pb in dust from the electronic workshops while no considerable non-cancer risk is associated with the adult and child exposure to dust from the cybercafés and offices. The results indicated that Cr and Pb are the main elements responsible for the non-carcinogenic risk arising from childhood exposure to electronic workshop dusts. The carcinogenic risk due to exposure of humans to metals in these dust samples were within the range regarded as safe by the USEPA.
•Considerable non-cancer risks for childhood contact with Pb in electronic workshop dusts.•Cr and Pb are the main elements responsible for the non-carcinogenic risk.•No considerable cancer risk from exposure of humans to dust-borne metals.
This study provides data on the characteristic levels, spatial patterns, sources, and risk of
n-
alkanes (AHs) octane,
n-
C
8
, to tetracontane,
n-
C
40
and polycyclic aromatic hydrocarbons (PAHs) ...in surficial sediments from the Escravos River Basin (ERB), Nigeria. The
n-
alkane and PAH concentrations in sediments were quantified by chromatographic methods. The concentrations of AHs and PAHs in the ERB sediments varied from 95 to 3430 µg g
−1
and from 0.75 to 213 µg g
−1
, respectively. Both the concentrations of AHs and PAHs in ERB sediments exceeded their respective guideline values. The carbon preference index and other AH markers provide evidence that the AHs in the ERB sediments originated from petroleum sources. Ecological risk assessment indicated that the ecological risk relating to an organism’s contact with PAHs in the ERB sediments was high. The possible carcinogenic risk arising from human exposure with PAHs in surface sediments through accidental oral ingestion and skin contact exceeded the safe level of 10
–6
, indicating a considerable probable cancer risk for fishermen and other inhabitants of the ERB. PAH isomer ratios and multivariate statistics suggested that the PAHs in sediments from the ERB originated from gas flaring inputs, discharges from oil drilling platforms, diesel engines, ships, and speed boats, and combustion of wood and other biomass.
Among other factors, the electrochemical capacitor (EC) properties of graphene oxide (GO) are limited by conductivity issues emanating from high oxygen concentrations. Hence, innovative GO ...modifications, such as derivatisation and synthesising composites with conducting polymers, are required to boost the EC properties. This allows the exploitation of the low material cost associated with carbonaceous materials. Herein, the effect of temperature (70, 130 and 190 °C) on the hydrothermal treatment of a GO/urea mixture (to form nitrogen-doped reduced GO samples U70, U130 and U190 (N-RGO), respectively) was investigated in order to study the resulting physicochemical and EC properties of N-RGO in a K
2
SO
4
electrolyte. Subsequently, the EC properties of the N-RGO obtained from the optimum temperature were investigated in composites with polyaniline (PANI). The functionality of the composites in the electrolytes, namely, K
2
SO
4
(SO
4
2−
radius: 258 pm)
versus
KOH (OH
−
radius: 133 pm), was compared. The nitrogen at% in GO and N-RGO (U190) was 0.39 and 6.74%, respectively, with corresponding conductivities of 4.61 × 10
−7
and 4.17 × 10
−1
S cm
−1
. Compared with GO, U130 achieved the highest increase in specific capacitance (
C
s
) of 200 times at 10 mV s
−1
. The 5 wt% PANI composite displayed the highest enhancement of
C
s
of 14 032% at 50 mV s
−1
and 4749% at 5 mV s
−1
relative to N-RGO and PANI in K
2
SO
4
, respectively. The highest
C
s
values for NRGO-PANI composites in KOH were more than double those of K
2
SO
4
. This work demonstrates that the hydrothermal treatment temperature tailors the physicochemical properties of the doped GO and, together with the anion size of the electrolyte and PANI wt%, synergistically tunes the EC properties of the ultimate PANI-N-RGO composite.
High-temperature treatment increased the conductivity, carrier density and mobility of N-RGO. Inclusion of PANI tailored activities from capacitive to battery-like and diffusion-controlled.
Organochlorine pesticide (OCP) and polybrominated diphenyl ether (PBDE) concentrations were measured in thirty popular brands of imported canned fish (mackerel, sardines, and tuna) in Nigeria to ...ascertain potential threats to humans arising from their consumption. The Σ20 OCP concentrations in mackerel ranged from 0.47 to 7.36 ng g−1, while those of tuna and sardines varied from 1.06 to 2.19 and 0.11 to 12.7 ng g−1, respectively. The Σ39 PBDE concentrations in mackerel varied from 0.06 to 4.21 ng g−1, while those of tuna and sardines ranged from 0.19 to 3.18 and 0.04 to 8.26 ng g−1, respectively. The estimated daily intake (EDI) of OCPs and PBDEs from ingestion of the canned fish by adults and children were in the magnitude of 0.03 to 17.6 ng kg−1 bw day−1 and 9.9 × 10−3 to 11.5 ng kg−1 bw day−1 respectively. The hazard index (HI) and total cancer risk (TCR) values for OCPs and PBDEs from ingestion of the canned fish were less than 1 and 10−6, respectively. The dietary intakes of OCPs and PBDEs from these brands of canned fish by adults and children result in no adverse non-cancer and cancer risks.
The characteristic concentrations of 28 PCB congeners, their spatial distributions, sources, and associated risks to the ecosystem were investigated in sediments of some rivers around a glass ...industry and power generating plant in the Niger Delta of Nigeria. Gas chromatography-mass spectrometry (GC-MS) was applied for the identification and quantification of PCBs in sediments from these rivers. The Ʃ28 PCB concentrations (dry weight) in sediments ranged from 1520 to 3540 ng g−1 for the Afiesere River, 976–5670 ng g−1 for the Edor River, and from 1440 to 6340 ng g−1 for the Okpare River. The homologue distribution patterns in sediments from these rivers indicated that low-chlorinated (2 Cl to 5 Cl) PCBs were more dominant than high-chlorinated (6 Cl to 10 Cl) PCBs with tri-, penta- and deca-PCBs as the top homologues. The PCB source analyses suggested that the PCB contamination of these river sediments could have originated from Aroclor mixtures, paints, pigments and other inadvertent sources. The risk assessment indicated a high risk to the ecosystem.
Display omitted
•PCBs were determined in sediments from the Afiesere, Edor and Okpare rivers.•Low-chlorinated PCBs were dominant in the sediments.•Exposure of the ecosystem to PCBs in these sediments poses a high risk.•Sources of PCBs in sediments include Aroclor mixtures, paints and pigments.
In this study, the concentrations of 28 polychlorinated biphenyl (PCB) congeners, including 12 dioxin-like PCBs and 7 indicator PCBs, were determined in sediments around oil production facilities in ...the Escravos River Basin of the Niger Delta in Nigeria. The aim was to describe the spatial patterns, sources, and ecosystem risks associated with exposure to PCBs in sediments of this river basin. Gas chromatography-mass spectrometry (GC–MS) was used to determine the concentrations of PCBs in the sediments. The Ʃ28 PCB concentrations in sediments from the Escravos River Basin ranged between 226 and 31,900 ng g−1 with a median concentration of 2300 ng g−1. The results indicated that sediments around crude oil production facilities, such as, wellheads, flow stations, and truck lines, had significantly higher levels of Ʃ28 PCBs (p < 0.05) than those collected near residential communities within the river basin. The median concentrations of PCB homologues in sediments from this river basin followed the sequence: hexaPCBs > penta-PCBs > tetra-PCBs > hepta-PCBs > tri-PCBs > di-PCBs > deca-PCBs > octa-PCBs > nona-PCBs. The risk assessment of PCBs in sediments from this river basin suggest very high potential risks for both organisms and humans.
•PCBs were measured in sediments from the Escravos River Basin.•Low chlorinated PCBs were dominant in the sediments.•Potential ecological risk exists for exposure of organisms to PCBs in sediments.•PCBs in the sediments are associated with inadvertent sources.
This study investigated the concentrations of 39 polybrominated diphenyl ether (PBDE) congeners in sediments from three rivers in the western Niger Delta of Nigeria that have been affected by ...pollution from urbanization and industrial activities. The Σ39 PBDE concentrations in sediments from these rivers ranged from 0.29 to 95.5, 5.15 to 121, and 0.73 to 66.1 ng g−1 for the Afiesere (AR), Edor (ER), and Okpare Rivers (OR), respectively. The homologue distribution patterns indicated the prominence of tetra- and penta-BDE congeners in sediments from these rivers. The ecological risk assessment results showed that the penta-BDEs were the primary source of risk to sediment-dwelling organisms in these rivers. However, the human health risk assessment indicated negligible risks for exposure of both adults and children to PBDEs in these sediments. The source apportionment suggests that the PBDE contamination in these river sediments was derived from long-distance migration, debromination of highly brominated congeners, and commercial penta-BDEs. These results reflect the use of penta-BDE formulations in this region rather than octa- and deca-BDE formulations.
•Sediments from these rivers are contaminated with PBDEs.•Industrial and urban activities are potent contributors of PBDEs to the sediment.•Tetra and penta-BDEs were the dominant species in sediments from these Rivers.•Penta-BDEs in these sediments are of potential risk to the ecosystem.•PBDE profiles in these sediments reflect the use of penta-BDE formulation.
The concentration of TBBPA in dust samples from automobiles (n = 14), computer laboratories (n = 8), homes (n = 7), and offices (n = 7), and, also, PBDE concentrations in the indoor dust of 19 ...personal and previously owned automobiles in Durban, South Africa, were determined. Gas chromatography coupled with mass spectrometry was applied for the separation, identification, and quantitation of TBBPA and PBDEs. The median concentrations of TBBPA were 1156, 269, 120, and 492 ng g⁻¹ in automobiles, computer laboratories, homes, and offices, respectively. The ∑ ₙ ₌ ₈ PBDE in 19 automobile samples ranged from 573 to 11,833 ng g⁻¹. BDE-209 accounted for approximately 42 % of ∑ ₙ ₌ ₈ PBDE in the samples. Household characteristics influenced the distribution of TBBPA in the various microenvironments. By assuming an average dust ingestion rate, and a median TBBPA concentration, the ∑DED (in ng kg⁻¹ bw day⁻¹) of TBBPA is 0.08, 0.08, and 0.60, for an adult, teenager, and toddler, respectively. These doses are similar to dust ingestion intakes reported for Asian countries where there is a high demand for TBBPA as a flame retardant. Similarly, automobiles provide ample opportunity for human exposure to PBDEs via dust ingestion, particularly for toddlers and occupationally exposed adults.
The concentrations of the sixteen United States Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) were determined in dusts from different land-use types in Benin City by means ...of gas chromatography–mass spectrometry. The results obtained were used to assess the ecological and human health risk and to determine the source apportionment. The Ʃ16 PAH concentrations in dusts from Benin City ranged from 230 to 2300 µg kg
−1
for industrial areas, 211–1330 µg kg
−1
for commercial areas, 153–1170 µg kg
−1
for residential areas, and from 216 to 1970 µg kg
−1
for school playgrounds/parks. The ecological risk assessment suggested that the levels of PAHs in dusts from these land-use types are of low-to-moderate risk to organisms. The benzo(a)pyrene carcinogenic potency BaP
TEQ
(70.5–131 µg kg
−1
) and benzo(a)pyrene mutagenic potency BaP
MEQ
(62.9–122 µg kg
−1
) concentrations were below the Canadian soil quality guideline value of 600 µg kg
−1
. The incremental lifetime carcinogenic risk (ILCR) arising from exposure of adults and children to PAHs in dusts from Benin City were in the magnitude of 10
–4
–10
–2
, which exceeded the safe target levels of 10
–6
, implying a considerable cancer risk for residents of this city. The PAH source apportionment derived from isomeric ratios and multivariate statistics indicated that burning of biomass, wood, and charcoal, and vehicular traffic were the predominant sources of PAHs in dusts from Benin City.
