Lixi Zeng

Global distribution of perfluorochemicals (PFCs) in potential human exposure source–A review

Human exposure to perfluorochemicals (PFCs) has attracted mounting attention due to their potential harmful effects. Breathing, dietary intake, and drinking are believed to be the main routes for PFC entering into human body. Thus, we profiled PFC compositions and concentrations in indoor air and dust, food, and drinking water with detailed analysis of literature data published after 2010. Concentrations of PFCs in air and dust samples collected from home, office, and vehicle were outlined. The results showed that neutral PFCs (e.g., fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamide ethanols (FOSEs)) should be given attention in addition to PFOS and PFOA. We summarized PFC concentrations in various food items, including vegetables, dairy products, beverages, eggs, meat products, fish, and shellfish. We showed that humans are subject to the dietary PFC exposure mostly through fish and shellfish consumption. Concentrations of PFCs in different drinking water samples collected from various countries were analyzed. Well water and tap water contained relatively higher PFC concentrations than other types of drinking water. Furthermore, PFC contamination in drinking water was influenced by the techniques for drinking water treatment and bottle-originating pollution.

Tracking Dietary Sources of Short- and Medium-Chain Chlorinated Paraffins in Marine Mammals through a Subtropical Marine Food Web

Our previous study revealed an elevated accumulation of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in marine mammals from Hong Kong waters in the South China Sea. To examine the bioaccumulation potential and biomagnification in these apex predators, we sampled the dietary items of marine mammals and tracked the sources of SCCPs and MCCPs through a marine food web in this region. Sixteen fish species, seven crustacean species, and four mollusk species were collected, and the main prey species were identified for two species of marine mammals. Concentrations of ∑SCCPs and ∑MCCPs in these collected species suggested a moderate pollution level in Hong Kong waters compared to the global range. Lipid content was found to mediate congener-specific bioaccumulation in these marine species. Significantly positive correlations were observed between trophic levels and concentrations of ∑SCCPs or ∑MCCPs (p < 0.05). Trophic magnification factors for ∑SCCPs and ∑MCCPs were 4.29 and 4.79, indicating that both of them have trophic magnification potentials. Elevated biomagnification of SCCPs and MCCPs from prey species to marine mammals was observed. This is the first report of dietary source tracking of SCCPs and MCCPs in marine mammals. The elevated biomagnification between prey and marine mammals raises environmental concerns about these contaminants.

Spatial and temporal trends of short- and medium-chain chlorinated paraffins in sediments off the urbanized coastal zones in China and Japan: A comparison study

To examine the impacts of urbanization and industrialization on the coastal environment, and assess the effectiveness of control measures on the contamination by chlorinated paraffins (CPs) in East Asia, surface and core sediments were sampled from the urbanized coastal zones in China and Japan (i.e., Pearl River Delta (PRD), Hong Kong waters and Tokyo Bay) and analyzed for short-chain (SCCPs) and medium-chain CPs (MCCPs). Much higher concentrations of CPs were found in the industrialized PRD than in adjacent Hong Kong waters. Significant correlation between CP concentration and population density in the coastal district of Hong Kong was observed (r2xa0=xa00.72 for SCCPs and 0.55 for MCCPs, pxa0<xa00.05), highlighting the effect of urbanization. By contrast, a relatively lower pollution level of CPs was detected in Tokyo Bay. More long-chain groups within SCCPs in the PRD than in Hong Kong waters and Tokyo Bay implied the effect of industrialization. Comparison of temporal trends between Hong Kong outer harbor with Tokyo Bay shows the striking difference in historical deposition of CPs under different regulatory situations in China and Japan. For the first time, the declining CP concentrations in Tokyo Bay, Japan, attest to the effectiveness of emissions controls.

Visible light-enhanced electrocatalytic alcohol oxidation based on two dimensional Pt-BiOBr nanocomposite

Photoelectrocatalytic oxidation based on noble/semiconductor has been a renewed interest in the past decades. The lack of high-performance semiconductor support remains a challenge for the harvesting and conversion of solar energy. Here, we report the syntheses of two dimensional (2D) BiOBr nanosheets with the superiorities of suitable band gaps, nontoxic, corrosion resistant and so on. These features enable them unprecedented performance for acting as the visible-light-driven support towards alcohol oxidation. Firstly, the pure BiOBr nanosheet has negligible activity towards alcohol oxidation. After the deposition of Pt nanoparticles (NPs), the as-prepared Pt-BiOBr composites show superior electrocatalytic activities towards ethanol and methanol oxidation reaction under visible light irradiation, with the mass activities of 929.8u202fmAu202fmg-1Pt and 751.7u202fmAu202fmg-1Pt, 6.0 and 28.4-fold enhancements than those under dark condition, respectively. The great enhancement in the photoelectrocatalytic performances can be attributed to the unique 2D nanostructure, synergistic and photocatalytic effects. This work may pave up a new route for designing the desirable semiconductor supports for the decoration of the noble metal catalysts, showing significant promise for the application of fuel cells.

A short review on human exposure to and tissue distribution of per- and polyfluoroalkyl substances (PFASs)

PFASs are widely distributed in natural and living environment and can enter human bodies via different routes. Many studies have reported that PFASs may be associated with human diseases, such as urine acid and thyroid diseases. In this study, we reviewed PFAS levels in human bodies reported in past seven years, including blood, urine, milk, and tissues (hair and nails). Most studies focused on human blood. Blood type, spatiality, human age, and gender were found to have a strong relationship with PFAS levels in blood samples. The PFAS distribution in urine samples was reported to be associated with the chain length of PFASs and human gender. Urinary excretion was found to be an important pathway of PFAS elimination. PFAS levels in human milk might be affected by various factors, such as mothers age, dietary habit, parity of mothers and the interval of interpregnancy. Data in hair and nails remain very limited, but these matrices offer a non-invasive approach to evaluate human exposure to PFASs.

One-pot fabrication of Nitrogen-doped graphene supported binary palladium-sliver nanocapsules enable efficient ethylene glycol electrocatalysis

Fuel cells hold great potential of replacing traditional fossil fuel to alleviate the energy crisis and increasing environmental concerns. Although great progresses have been achieved over decades, the sluggish reaction kinetics and poor durability of electrocatalysts in fuel cells have been the decisive bottleneck that limited their practical applications. Herein, we focus on the design and development of cost-efficient anode electrocatalysts for fuel cells and report the successful creation of an advanced class of N-doped graphene (NG) supported binary PdAg nanocapsules (PdAg NCPs). The well-defined nanocatalysts with highly open structure exhibit greatly improved electrocatalytic performances for ethylene glycol oxidation reaction (EGOR). In particular, the optimized PdAg NCPs/NG show the mass and specific activities of 6118.3u202fmAu202fmg-1 and 13.8u202fmAu202fcm-2, which are 5.8 and 6.9 times larger than those of the commercial Pd/C catalysts, respectively. More importantly, such PdAg NCPs/NG can also maintain at least 500 potential cycles with limited catalytic activity attenuation, showing an advanced class of electrocatalysts for fuel cells.

Combined Effects of Dust and Dietary Exposure of Occupational Workers and Local Residents to Short- and Medium-Chain Chlorinated Paraffins in a Mega E-waste Recycling Industrial Park in South China

Four types of dust samples and nine categories of locally produced staple foods were collected from a mega e-waste recycling industrial park and its surrounding regions, and simultaneously analyzed for short-chain and medium-chain chlorinated paraffins (CPs) to estimate dust and dietary exposure and their combined effects on occupational workers and local residents. All samples related to e-waste activities contained considerably high concentrations of CPs. The highest dust concentration was found in e-waste workshops. CPs were highly accumulated in local plant and animal origin foods, most markedly in fish, vegetables, and rice. The main contribution to CP intake under a median exposure scenario was from the diet, and vegetables, fish, and rice were the three largest dietary intake sources. Only the combined dust and food exposure from the present study has approached or even exceeded the highest tolerable daily intake (TDI) set up by the International Program on Chemical Safety (IPCS). However, due to lack of official threshold values for CP exposure on adverse human health, there are limitations on accurate risk assessment. Considering the presence of other exposure pathways, CPs endocrine disrupter properties, as well as the multicomponent chemical cocktails effects, potential high risks from CP exposure may be posed to e-waste workers and local residents.

Enhanced electrocatalytic ethanol oxidation reaction in alkaline media over Pt on a 2D BiVO4-modified electrode under visible light irradiation

Bismuth vanadate (BiVO4), as a typical visible-light-activated semiconductor, has attracted much attention in water oxidation. In this paper, we extend it to be a visible-light responsive support for the application of electrocatalytic ethanol oxidation reaction (EOR). Firstly, two dimensional (2D) BiVO4 nanosheets were synthesized, and then worked as the support for the decoration of Pt nanoparticles. Pt nanoparticles of ultra-small size with an average diameter of 3.5 nm were well dispersed on the surface of as-synthesized 2D BiVO4 nanosheets. By using the as-prepared Pt–BiVO4 as a working electrode, 2.7 folds enhanced catalytic activity for the EOR were achieved under visible light irradiation compared to that under dark conditions. The synergistic effect of photocatalysis and electrocatalysis together with the 2D structure of BiVO4 result in the improvement of the catalytic performance.