More than two billion people worldwide have suffered thyroid disorders from either iodine deficiency or excess. By creating the national map of groundwater iodine throughout China, we reveal the spatial responses of diverse health risks to iodine in continental groundwater. Greater non-carcinogenic risks relevant to lower iodine more likely occur in the areas of higher altitude, while those associated with high groundwater iodine are concentrated in the areas suffered from transgressions enhanced by land over-use and intensive anthropogenic overexploitation. The potential roles of groundwater iodine species are also explored: iodide might be associated with subclinical hypothyroidism particularly in higher iodine regions, whereas iodate impacts on thyroid risks in presence of universal salt iodization exhibit high uncertainties in lower iodine regions. This implies that accurate iodine supply depending on spatial heterogeneity and dietary iodine structure optimization are highly needed to mitigate thyroid risks in iodine-deficient and -excess areas globally.
Abstract The overall performance of the simulated seasonal precipitation response to local terrestrial forcings, namely vegetation abundance and soil moisture, in the Sahel among the Coupled Model Intercomparison Project Phase Five (CMIP5) Earth System Models (ESMs) is systematically investigated and compared with its observational counterpart using a multivariate statistical method. The observed seasonal precipitation response is evaluated against a large ensemble of observational, reanalysis, and satellite data sets to provide quantification of uncertainties. The behaviour of models with and without a Dynamic Global Vegetation Model (DGVM) component is also explored, along with the mechanisms responsible for terrestrial feedback on rainfall. In general, the CMIP5 models can reasonably capture the seasonal evolution of Sahel precipitation and soil moisture, albeit with wet biases during the pre-monsoon period and dry biases during the peak monsoon period. The non-DGVM ESMs simulate comparable leaf area indices (LAIs) with observations, while DGVM-enabled ESMs simulate too much year-round LAI. The variance of precipitation that is attributed to oceanic forcings in CMIP5 is comparable with observations; however, the variance of precipitation that is attributed to terrestrial forcings is smaller in CMIP5 models than observed, especially for non-DGVM ESMs. CMIP5 models, especially those without DGVMs, undervalue precipitation's observed response strength to soil moisture anomalies. In both observations and CMIP5 models, none of the atmospheric variables show significant responses to direct vegetation forcing, except for the response in transpiration. Although vegetation has minimal direct effect on the atmospheric state, it can affect the atmosphere by modifying soil moisture and transpiration rate indirectly, which helps explain the more realistic simulation of rainfall in DGVM-enabled ESMs than non-DGVM ESMs. Coupling of an ESM to a DGVM is critical in generating reasonable land–atmosphere feedback and examining future ecological and climatic changes over the Sahel.
The widely spilled diclofenac (DCF) in water has attracted broad attention because of its potential environmental risk. In this work, palladium quantum dots (PQDs) deposited g-C3N4 photocatalysts (PCNs) were fabricated through a two-step process, i.e., initial thermal polymerization followed by an in-situ reduction for PQDs deposition. In addition, the synthesized g-C3N4 (43.09 m2/g) composing of ultrathin sheets had 4 times larger specific surface area than bulk g-C3N4 (8.73 m2/g), thus offered abundant sites for reaction. The optimized material (PCN2) with 1 wt% PQDs loading content achieved the highest cost-efficiency for DCF degradation, and exhibited a kinetic rate constant (k1) of 0.072 min−1, which was 8 times higher than bulk g-C3N4. The mechanisms on enhanced photocatalytic activity of PCN are interpreted as: (1) decoration of PQDs can alter the optical band structure of g-C3N4, leading to a narrowed bandgap; (2) PQDs can act as electron transfer mediator to retard the recombination of photogenerated charge carriers; and (3) a photosensitization-like electron transfer pathway occurs from highest occupied molecular orbital (HOMO) of DCF to conduction band (CB) of g-C3N4 by means of PQDs. Radical quenching experiments and electron spin resonance (ESR) analysis indicated •O2- was the primary radical for DCF degradation. Density functional theory (DFT) calculation combined intermediates identification further revealed that the Cl11 and N12 atoms with high Fukui index (f 0) were more venerable to attack. PCN2 also remained good stability after five continuous cycles for DCF degradation, showing the great potential for practical application in water treatment area.
ABSTRACT: A higher denitrification rate was realized via controlling the mass ratio of pyrite and poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) under natural aerobic conditions. The results showed that the suitable mass ratio of PHBV and pyrite could be 1:2 with its removal efficiency of nitrogen and phosphorus of 99.7 and 53.4%, respectively. The PHBV/pyrite system has formed the spatial patterns of the biofilm community, such as Dechloromons attached to the pyrite surface, Rhodocyclaceae attached to the PHBV surface, and Acidovorax attached to the suppled sludge, which highlighted that the autotrophic??? heterotrophic synergy was achieved. The difference analysis among functional genes detected by high-throughput quantitative polymerase chain reaction indicated that the surface of pyrite in the pyrite/PHBV system is the hot area of methane production, the denitrifying process, and phosphorus removal. Network analysis indicated that there was a closer connection among functional genes on the pyrite surface, also supporting the speculation that pyrite was the hot area for the interaction of various genes in the pyrite/PHBV system. The key gene co-occurrence revealed that lig, nirS, and aspA are the keystone genes for cellulose degradation, denitrification, and S cycling, respectively. These results suggested that the pyrite surface was the hot area for denitrification, phosphorus removal in the blending system with pyrite and PHBV for nitrogen and phosphorus removal.
Species are changing their elevational distributions in response to climate change, leading to biodiversity loss and changes in community structure. Yet whether native and non-native species have consistent elevational shifts remains to be evaluated. Subtropical mountains are rich in biodiversity, sensitive to climate change, and are experiencing high risks of biological invasion. Hence exploring the changes in species elevational distributions induced by climate change in subtropical mountains is an urgent need. Here, we explored the impact of climate change on the elevational distribution of seed plant species in Jinfo Mountain (Mt. Jinfo), a subtropical mountain in China with rich plant diversity. Notably, we compared the elevational redistributions of native and non-native plants in response to climate change. The results showed that the elevational centroids of native plant species moved downhill, while those of non-native plants shifted upward on average. The upper limit of native plants shifted downward, while the upper limit of non-native plants shifted upward on average. The elevational shifts of non-native plants were dominated by changes in the upper range limits, while those of native plants were affected by the lower limits. These opposite elevational shifts of native vs non-native species led to the increase in the elevational range size of the non-native plants, but decrease in the elevational range size of native plants, especially in high altitudes. The differences in the directions and magnitudes of elevational shifts between the native and non-native plants are mainly due to differences in their climate adaptation. Changes in temperature and precipitation influenced the elevational range shifts of native plants but not of non-native ones. This study provides a new perspective for understanding the elevational redistribution of native and non-native plant species in subtropical mountains, and suggests that climate change has stronger influence on native than non-native species.
The presence of brackish-saline groundwater (BSG) poses great harms for human health, agricultural and in-dustrial activity. Understanding how the major environmental features in BSG determine microbiota coalescence is crucial for groundwater monitoring optimization. Based on metabarcoding analysis of 242 PCR-amplified samples, we provided the first blueprints about distinct spatiotemporal distributions, ecological drivers and assembly processes of bacterial, archaeal and fungal communities in BSG obtained from new-constructed wells at Xiong'an New Area, China. Our study demonstrated that bacterial and archaeal communities exhibited signifi-cant spatial turnovers, while fungal community displayed the most obvious seasonal variation. Environmental filtering drove bacterial compositions more than those of archaea and fungi. Total dissolved solids (TDS), one of the most critical hydrochemical factors for salinization, had a stronger effect on bacterial spatiotemporal turn -over than on those of the other two taxonomic groups, while chemical oxygen demand (CODMn) was more significantly associated with prokaryotic community variations. Bacterial and archaeal taxa dominated the metacommunity network and connected closely, and TDS was mostly related to archaeal subnetwork topological features, suggesting a significant influence of TDS on species association patterns within archaea. Specific functional guilds like bacterial nitrite oxidation, anammox, and archaeal methanogenesis were enriched in lower-TDS habitats, while higher TDS favored bacterial communities involved in dark oxidation of sulfur compounds, fumarate respiration, and cellulolysis. Finally, we confirmed that bacterial and archaeal assembly processes were governed by determinism in each season, and that of fungi was more regulated by stochasticity. Higher TDS was speculated to lead bacterial assembly more deterministic and that of fungi more random. Together, these findings provided an integrate theoretical framework about the unique responses of the three life domains to brackish-saline stress, and had important implications for microbial ecological prediction in groundwater.