Improving the photoelectrochemical water splitting performance of CuO photocathodes using a protective CuBi2O4 layer.

A heterojunction photocathode of CuO and CuBi2O4 grown on an FTO substrate (FTO/CuO/CuBi2O4) was synthesized using hydrothermal method followed by spin coating and annealing to overcome the bottlenecks encountered by CuO in photoelectrochemical (PEC) water splitting application. The synthesis methods, morphological, structural properties, and composition of each sample under each synthesis condition are discussed in detail. The photocathode with 15 coating layers annealed at 450 °C exhibited the best PEC performance. Moreover, its current density reached 1.23 mA/cm2 under an applied voltage of - 0.6 V versus Ag/AgCl in a neutral electrolyte. Additionally, it exhibited higher stability than the bare CuO thin film. The bonding of CuBi2O4 on CuO resulted in close contact between the two semiconductors, helping the semiconductors support each other to increase the PEC efficiency of the photocathode. CuO acted as the electron-generating layer, and the CuBi2O4 layer helped minimize photocorrosion as well as transport the carriers to the electrode/electrolyte interface to accomplish the hydrogen evolution reaction.

Perfluoroalkyl substances (PFASs) in special management sea areas of Korea: Distribution and bioconcentration in edible fish species.

Thirteen PFASs in water (n = 58), sediment (n = 58) and edible fish samples (n = 81) collected from three special management sea areas of Korea including Gwangyang bay, Masan bay and Busan harbor in July 2018 were investigated. The mean PFASs concentration in water (ng/L) were in order Masan (5.09) > Busan (2.82) > Gwangyang (1.74). PFASs levels were found as the low concentration in sediment. The greatest total PFASs concentration in each fish tissue was found as 3.04 (ng/g ww) in a Japanese amberjack fish for muscle in Busan, 66.23 (ng/mL) in Japanese amberjack fish for blood in Masan and 125.03 (ng/g ww) flathead grey mullet in Busan bay. The BCF (L/kg) of PFDoDA was found as the highest in muscle of all species with values from 30,922 (grey mullet in Gwangyang) to 69,131 (grey mullet in Busan). PFDS was the highest BCF's PFASs (110,599 L/kg) in muscle which was found in Japanese amberjack in Busan bay.

Organotins and new antifouling biocides in water and sediments from three Korean Special Management Sea Areas following ten years of tributyltin regulation: Contamination profiles and risk assessment.

A simultaneous monitoring study on organotins (butyltins and phenyltins) and most frequently used alternative antifouling biocides (Irgarol 1051, Diuron, Sea-Nine 211 and M1) in water and sediments (n=44) collected from three Special Management Sea Areas operated by Korean government. The lower concentration of butyltins (BTs) than that of new antifouling biocides (NEW) was found in water but the significant greater concentration of BTs than that of NEW was still found in sediments. The tributyltin (TBT) levels in water exceeded the chronic criterion to protect seawater aquatic life at several sites. Even ten years after the ban of the use of TBT-based antifouling paint, the concentrations of TBT, Diuron and Irgarol 1051 in sediments from shipyards exceeded global sediment quality guidelines and potentially poses adverse risks on marine organisms and extremely high concentration of TBT up to 2304ng/g was found for a sediment collected at a shipyard.

A nationwide survey of perfluorinated alkyl substances in waters, sediment and biota collected from aquatic environment in Vietnam: Distributions and bioconcentration profiles.

Water, sediment, various tissues of fish, crustacean, gastropod and bivalve were collected from major river basins in Vietnam and analyzed for the presence of perfluorinated alkyl substances (PFASs). Furthermore, the occurrence of PFASs in coastal, tap and well waters collected from eight different regions in Vietnam was investigated. PFOA and PFOS were consistently detected as the dominant PFASs in surface waters. The greatest concentrations of PFOA (53.5ngL-1) and PFOS (40.2ngL-1) were found in a surface water sample collected from a channel that receives wastewater treatment plant discharges. PFOS and PFHxS were found as the predominant PFASs in sediments. The greatest PFAS concentration in biota was 16.9ng PFUnDA g-1 wet weight found in a fish liver. Some long-chain PFCAs including PFNA, PFUnDA and PFTrDA as well as PFHxS were more abundant than short-chain PFASs in biota tissues. The measured concentrations of PFOS and PFOA in surface and tap waters were below the provisional health advisory. The rank order of mean bioconcentration factor of PFOS in biota was; crustacean (115L/kg), gastropod (1117L/kg), fish (1120L/kg) and bivalve (2110L/kg). This study provides baseline information for a better understanding of PFASs contamination in Vietnam.

Concentration and correlations of perfluoroalkyl substances in whole blood among subjects from three different geographical areas in Korea.

Toxicity and persistence of perfluorinated alkyl substances (PFASs) in human have raised considerable concern and several biomonitoring studies throughout the world reported the widespread occurrence of these compounds in human tissues. However, information regarding influence of geographic, lifestyle and demographic factor on PFAS levels in human blood tissues is limited. In this study, whole blood samples collected in 2006-2007 from 319 donors from suburban Seoul (Suwon and Yongin), Busan and Yeosu in Korea were analyzed for perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorohexane sulfonate (PFHxS) and perfluorooctane sulfonamide (PFOSA). Blood donors classified into seven age groups with ages ranging from 8 to 82 years, and different lifestyles and socio-economic status. PFOS (median=4.15 ng/mL) was found at the highest concentration with a maximum concentration of 59.1 ng/mL. The concentrations of other PFASs were in the decreasing order of; PFOA (median=1.30 ng/mL)>PFNA (median=0.85 ng/mL)>PFHxS (median=0.47 ng/mL)>PFOSA (median=0.12 ng/mL). Geographical differences in the concentrations of five target PFASs were found. Significant positive relationships between PFAS concentrations and the age of the donors were found. Gender-related differences were found in the concentrations of PFOA, PFNA, PFHxS and PFOSA. No association was found between PFAS levels and several lifestyle factors and socio-economic status which included drinking habit, furniture/carpet in an indoor environment and monthly income. Occupation was an important determinant for PFNA and PFHxS concentrations in the whole blood. Except for PFOSA, significant associations were noted between PFASs concentrations and smoking habit. The results of this study provide information for further public health monitoring and safety management for PFASs in Korea.

Perfluorinated alkyl substances in water, sediment, plankton and fish from Korean rivers and lakes: a nationwide survey.

Water, sediment, plankton, and blood and liver tissues of crucian carp (Carassius auratus) and mandarin fish (Siniperca scherzeri) were collected from six major rivers and lakes in South Korea (including Namhan River, Bukhan River, Nakdong River, Nam River, Yeongsan River and Sangsa Lake) and analyzed for perfluorinated alkyl substances (PFASs). Perfluorooctane sulfonate (PFOS) was consistently detected at the greatest concentrations in all media surveyed with the maximum concentration in water of 15 ng L(-1) and in biota of 234 ng mL(-1) (fish blood). A general ascending order of PFAS concentration of water0.80, p<0.001) were observed between PFOS concentration in blood and liver tissues of both crucian carp and mandarin fish. This result suggests that blood can be used for nonlethal monitoring of PFOS in fish. Overall, the rank order of mean bioconcentration factors (BCFs) of PFOS in biota was; phytoplankton (196 L/kg)