Our previous study showed that the tea extract, epigallocatechin-3-gallate (EGCG), protects against microcystin-LR (MC-LR) -mediated apoptosis of human umbilical vein endothelial cells (HUVECs); however, the mechanism underlying MC-LR-induced HUVEC apoptosis remains incompletely understood. In this study, we investigated whether the nuclear factor erythroid-like 2 (NRF2)/heme oxygenase-1 (HO-1) pathway, which regulates antioxidant transcriptional regulation of oxidative stress and apoptosis, is involved in this process. Mitochondrial membrane potential (MMP) and caspase-3/-9 activities were evaluated in HUVECs by JC-1 staining and colorimetric activity assay, and a DCFH-DA fluorescent probe assay was used to quantitate reactive oxygen species (ROS) generation. The effects of MC-LR, EGCG, NF2, and HO-1 on HUVEC apoptosis were explored by western blotting and small interfering RNA (siRNA) analyses. MC-LR treatment downregulated HUVEC mitochondrial membrane potential, and decreased levels of cytochrome c release and activated caspase-3/-9, ROS generation, consequently inducing HUVEC apoptosis. EGCG treatment attenuated MC-LR-mediated HUVEC oxidative stress and mitochondria-related apoptosis. EGCG induced NRF2/HO-1 expression and activation in MC-LR treated HUVECs, while downregulation of NRF2/HO-1 by specific siRNAs revealed that NRF2/HO-1 signaling was involved in EGCG attenuation of MC-LR-induced HUVEC apoptosis. Our findings indicate that EGCG treatment protects against MC-LR-mediated HUVEC apoptosis via activation of NRF2/HO-1 signaling.

Locations of city features, e.g., city centers, roads, railways, and rivers, may impact urban carbon sinks. Therefore, the effects of city features on spatial variations of urban carbon sinks were investigated using geographic proximity data. The main results were as follows. (1) Carbon sink function varied in a complex manner with distance from the city center and with city size. The carbon sink per unit area increased with distance from the prefecture-level city center (0–30 km), with the dominant influence occurring within a 9 km radius. The lowest carbon sink per unit area was observed at a distance of 12 km from the city center of the provincial capital city (Guangzhou) and special economic zone (Shenzhen), which may be suburban industrial zones. (2) Carbon sinks decreased with increases in road grades as a result of the different functions and traffic flow, and carbon sinks were lowest near city express ways. For highways, carbon sinks were lower near highway entrances and exits. Carbon sinks around ordinary railways were higher than those around subways and light rail, but carbon sink characteristics grew more complex with increasing distances from subways and light rail. (3) Rivers were closely related to the urban layout. Grade I (i.e., larger) rivers were associated with lower carbon sinks, and carbon sink characteristics became increasingly complex around larger rivers. Within a 0–1000 m distance of all rivers, the carbon sink per unit area increased rapidly, but carbon sink characteristics differed slightly for grade I rivers. This study implies that it is important to take urbanization spatial position effects into account while assessing regional carbon sinks during urbanization and development.

The hydrological and pollution processes are an important science problem for aquatic ecosystem. In this study, the samples of river water, reservoir water, shallow groundwater, deep groundwater, and precipitation in mining area are collected and analyzed. δD and δ¹⁸O are used to identify hydrological process. δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ are used to identify the sources and pollution process of NO₃⁻. The results show that the various water bodies in Fenhe River Basin are slightly alkaline water. The ions in the water mainly come from rock weathering. The concentration of SO₄²⁻ is high due to the impact of coal mining activity. Deep groundwater is significantly less affected by evaporation and human activity, which is recharged by archaic groundwater. There are recharge and discharge between reservoir water, river water, soil water, and shallow groundwater. NO₃⁻ is the main N species in the study area, and forty-six percent of NO₃⁻-N concentrations exceed the drinking water standard of China (NO₃⁻-N ≤ 10 mg/L content). Nitrification is the main forming process of NO₃⁻. Denitrification is also found in river water of some river branches. The sources of NO₃⁻ are mainly controlled by land use type along the riverbank. NO₃⁻ of river water in the upper reaches are come from nitrogen in precipitation and soil organic N. River water in the lower reaches is polluted by a mixture of soil organic N and fertilizers.

Gasoline vehicles are a major source of anthropogenic secondary organic aerosols (SOAs). However, current models based on known precursors fail to explain the substantial SOAs from vehicle emissions due to the inadequate understanding of the formation mechanism. To provide more information on this issue, the formation of SOAs from ozonolysis of four light-duty gasoline vehicle exhaust systems was investigated with a vacuum ultraviolet photoionization mass spectrometer (VUV-PIMS). Remarkable SOAs formation was observed and the SOAs were primarily aliphatic alkenes. PI mass spectra of the SOAs from all vehicles exhibited similar spectral patterns (a regular mass group with m/z at 98, 112, 126 …). Interestingly, most carbonyl products of aliphatic alkenes observed as major gaseous products have specific molecular weights, and the main formation pathway of SOAs can be explained well using aldol condensation reactions of these carbonyls. This is a direct observation of the aldol condensation as a dominated pathway for SOAs formation, and the first report on the composition and formation mechanism of the SOAs from the ozonolysis of gasoline vehicle exhaust is given. The study reveals that low molecular weight alkenes may play a more significant role in vehicle-induced SOAs formation than previously believed. More importantly, the PI mass spectra of SOAs from vehicles show similarities to the field aerosol sample mass spectra, suggesting the possible significance of the aldol condensation reactions in ambient aerosol formation. Since carbonyls are a major degradation product of biogenic and anthropogenic VOCs through atmospheric oxidation processes, the mechanism proposed in this study can be applied more generally to explain aerosol formation from the oxidation of atmospheric hydrocarbons.

Salinity effects on the bioaccumulation and biokinetic processes of eight trace elements (Cu, Cr, Pb, Ni, Zn, Cd, Se, and As) in the black mussel Septifer virgatus were explored in the present study. A 6-week laboratory waterborne exposure first showed that salinity (15, 20, 25, and 30) had relatively weak or even no significant influence on trace element accumulation in the black mussels. Biokinetics including uptake and efflux was then quantified in the mussels at different salinities. Uptake rates of Ni and Zn were negatively correlated with the salinity, while the uptake of Cd was not significantly influenced by salinity. The efflux rates of Ni and Zn also exhibited an inverse relationship with salinity, whereas the case of Cd was on the contrary. Biokinetic modeling showed that the salinity effects on uptake and elimination of Ni and Zn counteracted with each other, thus weakening the combined effects on accumulation. Overall, the response of uptake to salinity could weakened, removed, or even overturned by elimination, depending on the relative magnitude of the change of the two processes. The combined effects of uptake and elimination further led to negative, no, or positive relationship between trace element accumulation and salinity.

Natural gas extraction (NGE) has expanded rapidly in the United States in recent years. Despite concerns, there is little information about the effects of NGE on air quality or personal exposures of people living or working nearby. Recent research suggests NGE emits polycyclic aromatic hydrocarbons (PAHs) into air. This study used low-density polyethylene passive samplers to measure concentrations of PAHs in air near active (n = 3) and proposed (n = 2) NGE sites. At each site, two concentric rings of air samplers were placed around the active or proposed well pad location. Silicone wristbands were used to assess personal PAH exposures of participants (n = 19) living or working near the sampling sites. All samples were analyzed for 62 PAHs using GC-MS/MS, and point sources were estimated using the fluoranthene/pyrene isomer ratio. ∑PAH was significantly higher in air at active NGE sites (Wilcoxon rank sum test, p < 0.01). PAHs in air were also more petrogenic (petroleum-derived) at active NGE sites. This suggests that PAH mixtures at active NGE sites may have been affected by direct emissions from petroleum sources at these sites. ∑PAH was also significantly higher in wristbands from participants who had active NGE wells on their properties than from participants who did not (Wilcoxon rank sum test, p < 0.005). There was a significant positive correlation between ∑PAH in participants' wristbands and ∑PAH in air measured closest to participants’ homes or workplaces (simple linear regression, p < 0.0001). These findings suggest that living or working near an active NGE well may increase personal PAH exposure. This work also supports the utility of the silicone wristband to assess personal PAH exposure.

This research aimed to evaluate the ecological risk of xenobiotics associated with agricultural activities by determining metal contents and biomarker responses using tucunaré (Cichla sp.) as a bioindicator. The work was conducted in the southwest region of the state of Tocantins, in the cities of Lagoa da Confusão and Pium. Water samples and specimens of Cichla sp. were collected in the Javaés and Formoso Rivers at three collection points (A, B and C). The concentrations of Cd, Pb, Cu, Cr, Mn, Ni and Zn in water and fish were analyzed. In fish, genotoxic, biochemical (glucose serum levels, AST (aspartate aminotransferase) and ALT (alanine aminotransferase) and histological (gills and liver) biomarkers were assessed. In the water, the Cr and Mn concentrations at the three collection points exceeded the values for Class 1 rivers. In the muscle, Cr was above the maximum limit allowed for human consumption at the three collection points, although the values at Points B and C were not significantly different from that at Point A (p > 0.05). At the three collection points, the micronucleus test revealed a low frequency of micronuclei. Significant hyperglycemia and a decrease in the AST activity of the fish collected at Point C was observed. In the gills, the most frequent alterations were at Stages I and II, which indicated mild to moderate damage, and epithelial detachment was the most frequent variation. In the liver tissue, the most frequently observed histological changes were at Stages I and II and included cytoplasmic vacuolization, nuclear hypertrophy, dilated sinusoids and bile stagnation. The integrated evaluation of these biomarkers indicated that fish collected from areas with intense agricultural activities presented adaptive responses that were likely caused by the availability and bioaccumulation of certain xenobiotics in the environment.

Air pollution contributes significantly to premature death in China. However, only a limited number of studies have identified the potential determinants of population exposure to PM2.5 from a socioeconomic perspective. This paper analyses the socioeconomic determinants of population exposure at the city level in China. We first estimated population exposure to PM2.5 by integrating high resolution spatial distribution maps of PM2.5 concentrations and population density, using data for 2013. Then, geographically weighted regression (GWR) modeling was undertaken to explore the strength and direction of relationships between the selected socioeconomic factors and population exposure. The results indicate that approximately 75% of the population of China lived in an area where PM2.5 concentrations were over 35 μg/m3 in 2013. From the GWR models, we found that the percentages for cities that showed a statistically significant relationship (p < 0.05) between population exposure and each of the six factors were: urbanization, 91.92%; industry share, 91.58%; construction level, 88.55%; urban expansion, 73.40%; income disparity, 64.98%; and private vehicles, 27.27%. The R-squared value for the six factors in the multivariable GWR model was 0.88, and all cities demonstrated a statistically significant relationship. More importantly, the association between the six factors and population exposure was found to be spatially heterogeneous at the local geographic level. Consideration of these six drivers of population exposure can help policy makers and epidemiologists to evaluate and reduce population exposure risks.

Tributyltin is a biocide used in nautical paints, aiming to reduce fouling of barnacles in ships. Despite the fact that many effects of TBT on marine species are known, studies in mammals have been limited, especially those evaluating its effect on the function of the hypothalamus-pituitary-thyroid (HPT) axis. The aim of this study was to investigate the effects of subchronic exposure to TBT on the HPT axis in female rats. Female Wistar rats received vehicle, TBT 200 ng kg−1 BW d−1 or 1000 ng kg−1 BW d−1 orally by gavage for 40 d. Hypothalamus, pituitary, thyroid, liver and blood samples were collected. TBT200 and TBT1000 thyroids showed vacuolated follicular cells, with follicular hypertrophy and hyperplasia. An increase in epithelial height and a decrease in the thyroid follicle and colloid area were observed in TBT1000 rats. Moreover, an increase in the epithelium/colloid area ratio was observed in both TBT groups. Lower TRH mRNA expression was observed in the hypothalami of TBT200 and TBT1000 rats. An increase in Dio1 mRNA levels was observed in the hypothalamus and thyroid in TBT1000 rats only. TSH serum levels were increased in TBT200 rats. In TBT1000 rats, there was a decrease in total T4 serum levels compared to control rats, whereas T3 serum levels did not show significant alterations. We conclude that TBT exposure can promote critical abnormalities in the HPT axis, including changes in TRH mRNA expression and serum TSH and T4 levels, in addition to affecting thyroid morphology. These findings demonstrate that TBT disrupts the HPT axis. Additionally, the changes found in thyroid hormones suggest that TBT may interfere with the peripheral metabolism of these hormones, an idea corroborated by the observed changes in Dio1 mRNA levels. Therefore, TBT exposition might interfere not only with the thyroid axis but also with thyroid hormone metabolism.

The Sanjiang Plain, which is located in northeastern China, given the distribution of temperate freshwater wetlands there and this region has considerable significance in ensuring food security in China. Two periods of farmland reclamation that occurred during the last 100 years led to the loss of nearly 80% of the area of the native wetlands, and the development of agriculture has also increased the potential environmental risks to the residual wetlands. To evaluate the effects of farmland reclamation on the accumulation of key elements within the residual wetland ecosystems, six wetland profiles in the Sanjiang Plain are selected in this study. Using age-depth models and the concentrations of key elements, the historical accumulation rates (ARs) of carbon (C), nutrient elements (N and P) and potentially toxic elements (Hg, As, Pb, Cu, and Zn) over the last 150 years are reconstructed. The results show that the ARs of the potentially toxic elements in two of the wetland profiles begin to increase during the first reclamation period (AD 1900–1930). The ARs of both of the key elements clearly increase in all of the wetland profiles during the second reclamation period (AD 1950–1980). After land reclamation had ceased, increases in population and the development of industry became major factors that caused the potential environmental risks to wetlands to continue to increase from AD 1980 to the present. During the last 100 years, reclamation has increased the potential environmental risks and has led to the storage of additional carbon in the residual wetlands of the Sanjiang Plain.