Science of the Total Environment最新文献

Earthen sites in China are widely exposed to freeze-thaw environments. There is a lack of knowledge about the spatial distribution patterns of freeze-thaw deterioration and environments, as well as preventive conservation strategies and subsequent refined research on the freeze-thaw deterioration of earthen sites. In this study, the freeze-thaw deterioration process of earthen sites was divided into two periods. Thirteen relevant factors were selected, and using the GIS-FAHP method, a susceptibility map for freeze-thaw deterioration of earthen sites in China was created. The Jenks Natural Breaks method was then employed to categorize the areas into five susceptibility levels: very low (24.6 %), low (18.2 %), moderate (24.2 %), high (18.2 %) and very high (14.8 %). Based on the susceptibility map, the three-level regionalization scheme for freeze-thaw environments of earthen sites in China was systematically developed, taking into account the differences in freeze-thaw deterioration susceptibility and natural landscape within the geomorphological units, and the environmental codes were assigned to third level small-regions. The freeze-thaw environments of earthen sites in China were finally divided into 5 major-regions, 20 sub-regions and 42 small-regions. The results showed that in the area east of the Heihe-Tengchong line, the susceptibility to freeze-thaw deterioration showed latitudinal correlation, and the susceptibility gradually increased from south to north; in the area west of the Heihe-Tengchong line, the susceptibility to freeze-thaw deterioration exhibited strong zonal characteristics. Among the provincial administrative units, Gansu Province and Xinjiang Uighur Autonomous Region have the most complex freeze-thaw environments, while Qinghai, Tibet, Sichuan and Heilongjiang Provinces have the harshest freeze-thaw environments. This study can support regional management and prevention of freeze-thaw deterioration and deterioration studies of earthen sites in China.

The analysis of terrestrial ecosystem carbon dynamics, based on scarce carbon flux observations or carbon flux products simulated by reanalysis meteorological data, has great uncertainties. A more accurate understanding of carbon dynamics in Eurasia was achieved by using a carbon flux dataset (CFD) from meteorological stations with quasi-observational characteristics. The growth of net carbon uptake of ecosystems over Eurasia has been decreasing since the early 2000s. The net ecosystem productivity (NEP) increased significantly with the growth rate of 8.7 × 10^-3 g C m^-2d^-1 yr^-1 in spring, summer, and autumn (SSA) during 2003-2011 (p < 0.05), which was correlated with the enhanced vegetation index (EVI) and land surface water index (LSWI). This growth was mostly in dry subhumid and humid regions. However, the change in Eurasian NEP was not significant after 2011. Additionally, about 79 % of the stations in Eurasia were in net carbon uptake in SSA, and net carbon emission stations were mainly located in southwestern Eurasia. The intensity of net carbon uptake was highest in the forest, with a mean carbon uptake of 1.73 ± 0.76 g C m^-2d^-1 in SSA during 2003-2018, and almost all stations demonstrated carbon uptake. During 2011-2018, the number of stations experiencing reduced NEP exceeded those with increased NEP, and this ratio was higher compared to 2003-2011, mainly due to the decrease in EVI and LSWI. The rate of NEP decline at stations with reduced NEP was 5.2 × 10^-3 g C m^-2d^-1 yr^-1 faster during 2011-2018 than in the previous period (p < 0.01). Most of the decreases in NEP during 2011-2018 occurred in cropland, grassland and urban land. The spatio-temporal dynamic analysis of Eurasian NEP could provide references for effective carbon management.

Nitrogen deposition and climate change have been identified as major threats to the biodiversity of semi-natural grasslands. Their relative contribution to recent biodiversity loss is however not fully understood, and may depend on local site conditions such as soil type, which hampers efforts to prevent further decline. We used data from >900 permanent plots in semi-natural grasslands in Dutch roadsides to investigate whether trends in plant diversity and community composition (2004-2020) could be explained by: (1) nitrogen deposition (NH_x and NO_y) and climate change (winter degree days and summer drought), (2) the interactive effect of nitrogen deposition and climate change, and (3) the interactive effect of nitrogen deposition and climate change with soil type. Overall we observed a decline in plant diversity and an increased dominance of tall species and grasses. These changes were linked to winter warming, but not to changes in summer drought and nitrogen deposition. The effect of winter warming was more pronounced in areas with higher NO_y deposition, but was consistent across different soil types. Our results suggest that winter warming will become an important driver of plant diversity loss by altering competitive interactions, which could have major repercussions for other trophic levels and ecosystem services. Future conservation and restoration of grassland biodiversity therefore requires management regimes that are adapted to winter warming.

Zero-valent iron biochar composites (ZVI/BC) are considered as effective amendments for arsenic (As)-contaminated soils. However, the mechanisms of transformation of various soil As species during ZVI/BC amendments remain unclear. This study investigated As transformation in four soils (namely, GX, ZJ, HB, and HN) treated with ZVI/BC for 65 days under two soil moisture conditions, unsaturated and oversaturated. Results showed that the 65-day treatment was divided into two stages based on the variation of labile As content. Within 2 days (stage 1), ZVI/BC addition quickly reduced labile As content by 5.91-90.3 % in soils under unsaturated conditions. During days 2-65 (stage 2), labile As ultimately decreased by 0.06-0.31 mg/kg in GX, ZJ, and HB while increasing by 22.1 mg/kg in HN soil, due to its lower pH value and Fe content. The variations of labile As were attributed to changes in multiple Fe minerals and associated As species. In stage 1, the corrosion of ZVI/BC generated amorphous Fe oxides to immobilize labile As, resulting in the accumulation of meta-stable As. In stage 2, amorphous Fe oxides were transformed into crystalline Fe oxides, resulting in the release and re-precipitation of As along with transformation, thus redistributing immobilized As into labile and stable As, which was evidenced by multiple methods, including chemical extraction, XRD, and TEM-EDX. The elevated soil moisture condition would enhance the corrosion of ZVI/BC in stage 1, further forming a reductive environment to facilitate the transformation of Fe minerals in stage 2. Besides, As bioaccessibility in soils was reduced by 10.8-38.7 % after ZVI/BC treatment in in-vitro gastrointestinal simulations. Overall, our study revealed the time-dependent transformation mechanism of soil As species and associated Fe minerals under different soil moisture with ZVI/BC treatments, and highlighted the effectiveness of ZVI/BC as a long-term amendment for As-contaminated soils.

Biochar addition is effective in reducing soil greenhouse gas (GHG) emissions, but it's essential to evaluate whether aged biochar retains this capability as its properties change over time. However, research comparing the effects of fresh and aged biochar on soil GHG emissions is limited. Moreover, exploring the priming effect of biochar on native soil organic carbon (SOC) mineralization is crucial for revealing the effect mechanism on soil CO₂ emission. However, research investigating the priming effects of aged biochar is limited. In this study, the effects of aged biochar addition on soil physicochemical properties, GHG emissions, and global warming potential (GWP) were examined through an incubation experiment with three treatments: (1) soil only (CK), (2) 1 % aged maize straw biochar addition (HBC1) and (3) 4 % aged maize straw biochar addition (HBC4), and then their effects were compared with those of fresh biochar from our previous research. ¹³C tracer technology was used to assess the priming effect of aged biochar on native SOC mineralization. Results showed that aged biochar improved soil physicochemical properties. Compared to CK, HBC1 and HBC4 reduced CO₂ emissions by 28.02 % and 20.15 %, respectively, and reduced N₂O emissions by 61.54 % and 66.39 %. HBC4 significantly increased CH₄ emission, whereas HBC1 reduced it. HBC1 and HBC4 reduced GWP by 29.01 % and 21.41 %, respectively. Overall, aged biochar demonstrated a greater reduction effect compared to fresh biochar at the 1 % addition ratio. The CO₂ reduction is attributed to the negative priming effect of aged biochar on native SOC mineralization. The reduction in N₂O emissions is attributed to aged biochar promoting microbial nitrogen fixation and reducing the ratio of denitrification to nitrification. The variation in CH₄ emissions reflects differing dominant factors influencing CH₄ emission across varying addition ratios. In conclusion, 1 % aged biochar addition demonstrates a more favorable long-term effect on mitigating GHG emissions.

Plastic pollution is widely recognized as one of the major threats to marine ecosystems. However, our knowledge on the ecological interactions between plastic and marine fauna is still limited. Here, we analyzed the substrate preferences for oviposition in the small-spotted catshark (Scyliorhinus canicula) and explored the influence of pollution, environmental conditions, and fishing pressure as potential drivers. For the first time, we report this catshark species using marine debris for oviposition, unraveling a behavioral shift in the oviposition substrate preferences towards plastics, particularly ghost fishing gear, when biological substrates are unavailable. Our results indicate that this behavioral change may be driven by the combined effects of plastic pollution and habitat degradation. Preferences also change with depth, with a larger preference for the hydrozoan Lytocarpia myriophyllum on the continental shelf, followed by sponges, as in this region mesophotic and deep benthic communities are still more abundant although impacted by human pressures. In contrast, on the continental slope, the preference shifts to tube-dwelling polychaetes and plastics, primarily ghost fishing gear, due to the limited availability of biological substrates in this region. We highlight that plastic-fish interactions may become increasingly recurrent as plastic substrates increase and habitat forming invertebrates decline due to trawl fishing and other anthropogenic activities, especially in the Mediterranean Sea. The implications of this behavior for catshark fitness are still largely unknown, which prompts further research concerning the potential impact on its survival and/or dispersal in the plastic age and highlights the urgency of preserving biogenic habitats.

Various sources associated with mining activities adversely affect water quality in aquatic ecosystems. This study aimed to estimate the sources of dissolved trace elements (DTEs: Al, As, B, Ba, Cd, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Sb, U, and Zn) affecting water chemistry in the upper Nakdong River (UNR) catchment and determine the hydrological processes associated with the inflow from anthropogenic sources. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were employed to estimate main sources affecting water chemistry and its spatiotemporal variability in the four tributaries and main channel of the UNR. Water samples were classified into four groups based on their chemistry. The spatiotemporal variations of DTEs were driven by the presence of anthropogenic sources (including smelters, AMD, mining-related sources), while running toward downstream. The correlations among PCA (and HCA), Zn as smelter impact, and deuterium excess (d-excess = δ²H - 8 × δ¹⁸O) indicated that smelters had a strong influence on water chemistry in the main channel after passing through the smelter. In the dry season, d-excess < ~12 ‰ was observed with increasing Zn levels and factor score for PC2, especially samples influenced by DTEs from smelter, indicating that groundwater affected by the smelters recharged mainly by summer rainwater impacted the spatiotemporal variability of DTEs. This multivariate study suggests that the spatiotemporal variation in DTEs is associated with the complex contributions of natural and anthropogenic sources to water chemistry, which are strongly influenced by hydrological processes and seasonality.

Flow regulation and the spread of invasive species are significant threats to freshwater biodiversity, including native fish communities in rivers across the globe. The bleak (Alburnus alburnus), an invasive fish currently widespread throughout the main rivers of the Iberian Peninsula, threatens native fish biodiversity, mostly via trophic competition and hybridisation. In this study, we assessed the impacts of bleak presence and rapid flow fluctuations (both main and interactive effects) on the use of artificial habitats (a flow refuge) and the stress physiology of barbels. We examined how bleak's presence influenced the selection of flow refuges by the native Iberian barbel (Luciobarbus bocagei) under base (continuous 7 L s^-1 flow stimulus) and pulsed (7 L s^-1 to a 60 L s^-1 pulse) flows in an indoor flume. We quantified habitat use within three specific regions of two installed flow refuges and two physiological responses (glucose and lactate) associated with the stress axis. The results indicated that the presence of bleak significantly reduced flow refuge use by barbels and this effect was more prominent during pulsed flows. Additionally, barbels exhibited higher levels of glucose and lactate in the presence of bleaks. These results show that bleaks compete with barbels for habitat under fluctuating flows and induce physiological adjustments that may reduce the ability of barbels to find low-velocity areas to shelter. Overall, the bleaks had a competitive advantage under high flow variability. This underscores the need for further studies and effective management strategies to protect native freshwater fish communities in the context of biological invasions and anthropogenic flow variability.

Background: Exposure to fine particulate matter (PM_2.5) has been linked to an increased risk of atherosclerosis. However, it remains unclear whether specific compounds within PM_2.5, rather than the overall mass, serve as a better indicator of adverse cardiovascular health outcomes associated with air pollution.

Methods: In this cross-sectional study, we included 3257 participants (aged 37-51 years) from the Coronary Artery Risk Development in Young Adults (CARDIA) study. Exposure to PM_2.5 and its constituent compounds, black carbon (BC), ammonium, nitrate, organic matter, sulfate, mineral dust, and sea salt were included in the analyses. Carotid intima media thickness (cIMT; the average of common, bulb, and internal carotid) was measured by carotid ultrasonography. We assessed the cross-sectional associations of one-year exposure to PM_2.5 and its compounds with mean cIMT using linear regression models adjusting for participants' demographics, individual- and neighborhood-level socioeconomic status, behavioral components, and health conditions. We also adopted Bayesian kernel machine regression (BKMR) models to investigate the association between the PM_2.5 compound mixture and cIMT as well as the contribution of each compound to the association.

Results: Greater exposure to BC was associated with higher cIMT (mm) (β =0.034, 95 % CI = 0.019-0.049, per IQR increase [0.56 μg/m³] of BC) among participants with a mean age of 45.0, consisting of 45.9 % Black and 54.1 % White males and females. The association was generally consistent across participants' demographic characteristics. In our BKMR analysis, BC exhibited a dose-response association with cIMT with a high contribution to the association of cIMT with PM_2.5 compound as a mixture (posterior inclusion probability [PIP]: 1.00).

Conclusions: Our findings suggest that certain compounds of PM_2.5, such as BC, may offer more reliable indications of the impact of air pollution on cardiovascular health.

Deep eutectic solvents (DES) are gaining interest as eco-friendly alternatives for extracting bioactive compounds, but their environmental benefits remain unclear and need further evaluation. In this work, a case study of total polyphenols (TPC) extraction from spent coffee grounds (SCG) was environmentally evaluated using life cycle assessment (LCA). First, the most convenient extraction time (1, 10, 20, or 40 min) for water and acetone 20 % from an environmental perspective was identified. Second, a comparison of different solvents-DES (choline chloride-1,6-hexanediol), water, and ethanol 20 %-under their optimal extraction yield conditions was performed using literature data. Results from the first study revealed that the environmentally optimal extraction time (10 min) was not the one leading to the highest yield. The main contributors to the impacts were the use of acetone and electricity consumption. For the second study, DES performed worse in all studied environmental impact categories compared to both ethanol 20 % and water. Ethanol 20 % was the better option compared to water due to its higher extraction yield (9.2 mg vs. 6.5 mg TPC/g SCG, respectively). The environmental impacts associated with the DES system were primarily attributed to the DES preparation step, which requires virgin raw materials (e.g., dimethyl hexanediol), and the adsorption stage involving the use of resins. A sensitivity analysis was also conducted by optimizing the DES system to the best possible described conditions (90 % reuse of DES and maximum reduction of the macroporous resin used to adsorb the TPC after extraction). Nevertheless, the DES system still performed worse than water or ethanol 20 % systems, in 11 out of 16 impact categories. The study highlights the importance to consider environmental impacts and yield when optimizing extraction processes, especially at the laboratory scale, as the insights gained are valuable for improving eco-efficiency on an industrial scale.