Seasonal Heterogeneity Research Articles

Spatial and Temporal Variations in Waterfowl Assemblage Structures in Mongolian Lakes and the Changes Linked to the Gradient of Lake Surface Areas

Lakes and wetlands provide top-priority hotspots that play a key role in maintaining and protecting threatened and migratory waterfowl. Identifying seasonal and spatial variations in aquatic bird communities and their responses to environmental factors is vital conservation efforts. However, there is a lack of information on waterfowl in Mongolian lakes and their associated wetlands. The purpose of this study was to investigate the spatial–seasonal changes in waterfowl assemblage structures in Mongolian lakes, as well as to determine how they respond to various environmental factors (lake surface area, elevation, and geographical distribution). Statistical analyses were performed using seasonal data (May, July, and September) for 28 waterfowl collected from 54 lakes across the country between 2016 and 2018. Seasonal heterogeneity in species richness and abundance was observed in lakes in each geographical region (Eastern, Central, and Western Mongolia). The composition of waterfowl in the lake was also relatively similar between May and September compared to July. This was due to the overlapping migration seasons in spring and autumn. Regionally, the number of waterfowl was much higher in the Eastern Mongolian lakes, followed by Central Mongolian lakes and then Western Mongolian lakes. This is likely due to differences in habitat availability and water levels between the regions. Eastern Mongolian lakes tend to have more wetlands and shallow water habitats, while Central and Western Mongolian lakes tend to have deeper open-water habitats. These differences in habitat types could contribute to the observed differences in waterfowl abundance among the regions. Additionally, some small lakes and the group of small lakes supported a greater abundance and diversity of waterfowl compared to some medium-sized and large lakes, suggesting that they are important for conservation. Indices of diversity (H’) and species dominance (D’) showed positive and negative correlations with lake surface area, respectively. Perhaps the increased surface area of the lake decreases the habitat overlap for designated waterfowl due to habitat heterogeneity. Accordingly, the indices (H’ and EH) increased as the waterfowl species composition became relatively equivalent in large lakes. Overall, spatial variations among the lakes were primarily attributable to the individual features of the lakes (shallowness, small lake groupings, and surface area), and seasonal variation in the lakes depended majorly on the compositional changes of the waterfowl due to migration.

Seasonal succession of microbial community co-occurrence patterns and community assembly mechanism in coal mining subsidence lakes.

Coal mining subsidence lakes are classic hydrologic characteristics created by underground coal mining and represent severe anthropogenic disturbances and environmental challenges. However, the assembly mechanisms and diversity of microbial communities shaped by such environments are poorly understood yet. In this study, we explored aquatic bacterial community diversity and ecological assembly processes in subsidence lakes during winter and summer using 16S rRNA gene sequencing. We observed that clear bacterial community structure was driven by seasonality more than by habitat, and the α-diversity and functional diversity of the bacterial community in summer were significantly higher than in winter (p < 0.001). Canonical correspondence analysis indicated that temperature and chlorophyll-a were the most crucial contributing factors influencing the community season variations in subsidence lakes. Specifically, temperature and chlorophyll-a explained 18.26 and 14.69% of the community season variation, respectively. The bacterial community variation was driven by deterministic processes in winter but dominated by stochastic processes in summer. Compared to winter, the network of bacterial communities in summer exhibited a higher average degree, modularity, and keystone taxa (hubs and connectors in a network), thereby forming a highly complex and stable community structure. These results illustrate the clear season heterogeneity of bacterial communities in subsidence lakes and provide new insights into revealing the effects of seasonal succession on microbial assembly processes in coal mining subsidence lake ecosystems.

Dissolved organic matter from surface and pore waters of a discontinuous permafrost watershed in central Alaska reveals both compositional and seasonal heterogeneity

Dissolved organic matter from surface and pore waters of a discontinuous permafrost watershed in central Alaska reveals both compositional and seasonal heterogeneity

Adaptation of construction and demolition waste management towards climate change

According to the results of observations of Federal agency Roshydromet, the specific signs of recent decades are climate changes caused by global warming. Their features are an increase in the average annual temperature, frequency and intensity of dangerous hydrometeorological phenomena, an increase in the amount of precipitation, spatial and seasonal heterogeneity. The territories of Russia are in the area of observed and predicted climate changes, and their consequences have an increasing impact on the socio-economic development of the country, the living conditions and health of people, as well as on the state of economic sectors and objects of economic activity. The article examines measures to adapt the sphere of management of construction and demolition waste (CDW) to the negative consequences of climate change.

Climatology and landscape determinants of AOD, SO2 and NO2 over Indo-Gangetic Plain

Indo-Gangetic Plains (IGP) experiences high loading of particulate and gaseous pollutants all year around and is considered to be the most polluted regions of India. Understanding the effect of landscape determinants on air pollution in IGP regions is crucial to make its environment sustainable. We examined satellite retrievals of OMI NO2 and SO2, and MODIS AOD to analyse the long-term trend, spatio-seasonal pattern and dynamics of aerosols, NO2 and SO2 over three IGP regions, namely Upper Indo-Gangetic plain (UIGP), Middle Indo-Gangetic plain (MIGP) and Lower Indo-Gangetic plain (LIGP) over the period 2005–2019. IGP experienced an overall increment in AOD (R2 = 0.63) and SO2 (R2 = 0.67) values, with LIGP (AOD, R2 = 0.8 & SO2, R2 = 0.8) experiencing the largest rate of enhancement. The levels of NO2 (R2 = 0.2) experienced a decrement after 2012 (owing to implementation of vehicle emission policy) except in MIGP, with UIGP (R2 = 0.23) exhibiting the largest rate of decrement. Seasonal heterogeneity in the nature of sources was observed over IGP regions. AOD (0.61 ± 0.1) and NO2 value (3.82 ± 0.98 × 1015 molecules/cm2) were found highest during post-monsoon in UIGP owing to crop residue burning activity. The value of NO2 (3.8 ± 1.4 × 1015 molecules/cm2) in MIGP was found highest during pre-monsoon due to high consumption of coal in power plants for summer cooling demand. The highest SO2 level (0.09 ± 0.06 DU) was observed during post-monsoon in UIGP, as a large number of brick kilns are fired during this period. Correlations among landscape determinants and pollutants revealed that topography is the dominant variable that affect the spatial pattern of AOD compared to vegetation and land use. Lower elevation tends to have high AOD values compared to higher elevation. Vegetation-AOD relationship showed an inverse association in IGP regions and is influenced by factors such as seasonal meteorology and size of the airborne particles. Vegetation possesses positive relationship with SO2 and NO2, implying no pollution abatement effect on SO2 and NO2 pollutants. Built-up change has deteriorating effect as well as quenching effect on pollutants. Increase in built terrain have deteriorated the air quality in UIGP whereas it favored in suppressing the aerosol level in LIGP.

Spatial and temporal change determined co-occurrence networks stability and community assembly processes of epipelagic seawater microbial community in the Nordic Sea

The Nordic Sea has a vital impact on the global climate change, occupies a significant status in the physical oceanography research, on account of its intersection of complex ocean currents. To explore the influence of seasonal and spatial heterogeneity in its epipelagic seawater on the microbial community structure, a total of 54 seawater samples from 18 stations and 3 water layers (0 m, 50 m, 100 m) were collected in the summer of 2017 and the autumn of 2018 from the Norwegian Sea, the Greenland Sea and the vicinity of Jan Mayen Island in the Nordic Sea. Alpha- and Beta- diversity analysis showed that significant differences were found between characteristic bacterial groups in detached or mixed currents of corresponding seasons, as endemic OTUs with seasonal and ocean current characteristics which revealed the existence of spatiotemporal patterns of microbial communities in the Nordic Sea. Moreover, co-occurrence networks were conducted to show different degree of complexity and stability of microbial community response to spatiotemporal dynamic changes. Furthermore, the flow and collision between ocean currents do have an impact on the community assembly processes by affecting the migration and dispersal of microbial communities. This study reflects the response of microbial communities to the spatiotemporal dynamics and reveals the microbial community assembly mechanisms under complex hydrological condition represented in the Nordic Sea.

Effect difference of climate change and urbanization on extreme precipitation over the Guangdong-Hong Kong-Macao Greater Bay Area

Increasing extreme precipitation caused by climate change and human activities may have severe consequences on people's lives and property. In this study, the effect difference of urbanization, climate change and their compound effect on the annual and seasonal extreme precipitation under various Shared Socioeconomic Pathways are investigated using a convection-permitting (4 km) Weather Research and Forecasting model in the mega urban agglomeration. The enhancement effects of urbanization and climate change on extreme precipitation are also compared in the near future (2021–2050) and far future (2071–2100) periods of various Shared Socioeconomic Pathways-Representative Concentration Pathways (SSP-RCP) emission scenarios. The Guangdong-Hong Kong-Macao Greater Bay Area (GBA), a subtropical coastal world-class urban agglomeration in China, is taken as a representative in this study. The results indicate that, annual extreme and total precipitation will be more intensive and more frequent at regional scale along with rising long-lived greenhouse gas (LLGHG) concentration, while future urbanization exacerbates precipitation at local scale. Urban-induced total precipitation increases in the downwind areas and some urban areas of urban agglomeration, but still slightly decreases (all below 1.5%) over the entire study area. And more robust and stronger urban-induced signal in extreme precipitation characteristic is found in and around the urban areas where the total precipitation increases, as seen with an increase of >20% in amount and day number. In the compound scenarios, the interaction between urban and LLGHGs on precipitation was nonlinear and can be better explored by using convective permitting simulations. While urbanization can amplify or dampen local to regional precipitation, increased concentration of LLGHGs still make regional precipitation shift toward a general enhancement. Urbanization still has an impact on spatial distribution of precipitation despite a warming background climate. Additionally, seasonal heterogeneity of precipitation will be enhanced in all the future scenarios, especially in the future urbanization scenarios. The enhancement of urbanization (increase by about 42.1%, 38.0%, 14.0% in the precipitation amount, days and intensity respectively) on summer extreme precipitation change is greater than that of low-level LLGHG concentration (same as above, but increase by about 38.7%, 35.4%, 13.4%), despite their different mechanisms in altering extreme precipitation. The dominant factor of extreme precipitation varies with urbanization level and the LLGHG concentration. More attention should be paid to urban-induced precipitation changes under sustainable development scenarios with low-level LLGHG concentration.

Early warning of red tides using bacterial and eukaryotic communities in nearshore waters

Anthropogenic discharge activities have increased nutrient pollution in coastal areas, leading to algal blooms and microbial community changes. Particularly, microbial communities could easily be affected with variation in nutrient pollution, and thus offered a promising strategy to predict early red tides warning via microbial community-levels variation and their keystone taxa hysteretic responses to nutrient pollution. Herein high-throughput sequencing technology from 52 samples were used to explore the variation of microbial communities and find the significant tipping points with aggravating nutrient conditions in Xiaoping Island coastal area. Results indicated that bacterial and microeukaryote communities were generally spatial and seasonal heterogeneity and were influenced by the different nutrient conditions. Procrustes test results showed that the comprehensive index of organics polluting (OPI), total nitrogen (TN), inorganic nitrogen (DIN), and total phosphorus (TP) were significantly correlated with the composition of bacteria and microeukaryotes. A SEGMENTED analysis revealed that the threshold of TN, DIN, and NH4–N for bacterial community were 0.23 ± 0.091 mg/L, 0.21 ± 0.084 mg/L, 0.09 ± 0.057 mg/L, respectively. Tipping points for TN, DIN, and NH4–N agreed with the concentration during Ceratium tripos and Skeletonema costatum blooms. Co-occurrence network results found that Planktomarina, Acinetobacter, and Verrucomicrobiaceae were keystone and OPI-discriminatory taxa. The abundant changes of Planktomarina at station A1 were significantly correlated with the development of C. tripos blooms (r = 0.55, p < 0.05), and also significantly correlated with TN, DIN, and NO3–N (r≥|0.55|, p < 0.05). The abundant changes of Acinetobacter and Verrucomicrobiaceae at station C1 were significantly correlated with the development of C. tripos blooms (r ≥ 0.77, p < 0.05), and also significantly correlated with PO4–P (r ≥ 0.64, p < 0.05). The dynamic abundance of keystone taxa showed that the trend of rapid changes could be monitored 1.5 months before the occurrence of red tide. Therefore, this study provides an assessment method for early warning of red tide occurrence and factors that trigger red tide.

A distinct clade of Bifidobacterium longum in the gut of Bangladeshi children thrives during weaning

The gut microbiome has an important role in infant health and development. We characterized the fecal microbiome and metabolome of 222 young children in Dhaka, Bangladesh during the first two years of life. A distinct Bifidobacterium longum clade expanded with introduction of solid foods and harbored enzymes for utilizing both breast milk and solid food substrates. The clade was highly prevalent in Bangladesh, present globally (at lower prevalence), and correlated with many other gut taxa and metabolites, indicating an important role in gut ecology. We also found that the B.longum clades and associated metabolites were implicated in childhood diarrhea and early growth, including positive associations between growth measures and B.longum subsp. infantis, indolelactate and N-acetylglutamate. Our data demonstrate geographic, cultural, seasonal, and ecological heterogeneity that should be accounted for when identifying microbiome factors implicated in and potentially benefiting infant development.

Seasonal variability of water residence time in the Subei Coastal Water, Yellow Sea: The joint role of tide and wind

Assessing the coastal water export rate is important for better solving the coastal environmental problems and developing environmental management strategies. To investigate the water export rate and its spatiotemporal variation in the Subei coastal water (SCW), a subregion of the Yellow Sea, this study applied water residence time (RT) as an indicator and studied the roles of tides, wind, and river discharge on the water export rate using numerical modeling and the RT adjoint method. RT had an annual and spatial mean of ∼80 days but presented highly spatial and seasonal heterogeneity. Spatially, high RT (∼100–300 days) occurred in the nearshore region, and its location varied in seasons. Temporally, RT was the shortest in the spring (∼55 days), longest in the summer (∼91 days), and median (∼81 days) in autumn and winter. Furthermore, the seasonal RT mismatched the strength of residual transport velocity (RTV) at the current season but instead relied on the combined effects of RTVs in the current and next seasons. Additional sensitivity experiments revealed that tides greatly increased the RT, the Changjiang River runoff slightly decreased the RT, while monsoon wind dominated the RT seasonal variation. As highlighted by an idealized analytical framework, increasing the magnitude ratio of the wind- and tidal-induced RTVs could amplify the RT seasonal variability. Ecologically, the shortest RT in spring might promote the rapid expansion of macroalgal blooms originating from the SCW into offshore waters, thereby contributing to green tide occurrence in the Yellow Sea. Therefore, the seasonality of RT should be considered in coastal management and scientific planning.

Chlorophyll maxima layer in a large subtropical reservoir (Xinanjiang Reservoir): Spatial development process and limitation by CO2 and phosphorus

In marine investigations, the maximum chlorophyll-a (Chla) concentration is often reported to occur at a specific depth below the ocean surface, a phenomenon known as subsurface Chla maxima (SCM). However, SCM has long been overlooked in artificial reservoirs, which may lead to a serious underestimation of the primary productivity level and trophic status of reservoirs. To better understand the temporal and spatial variability of SCM and the mechanisms leading to SCM development, this study conducted a detailed survey in a large subtropical reservoir (Xinanjiang Reservoir, XAJR) from September 2020 to August 2021. The seasonal thermal stratification, in situ variables (WT, pH, DO and Chla), nutrient concentrations (DSi, NO3−, DIP and DCO2), Chla maxima depth and magnitude of the riverine region (S1), transition region (S2) and the central part of the XAJR (S3 and S4) were all thoroughly investigated. Thermal stratification and SCM in XAJR exhibited significant seasonal and spatial heterogeneity. Phytoplankton biomass in the epilimnion was limited by dissolved CO2 from June to October in the warm seasons, while it was primarily limited by phosphorus in the other seasons, according to the nutrient limitation analysis. Along the water column, dissolved CO2 limitation occurred mainly above the SCM layer, and the water column below the SCM layer gradually transitioned from dissolved CO2 limitation to phosphorus limitation. Furthermore, as the thermal stratification developed, the upstream water mass moves along the middle of the water column as density flow toward the reservoir, providing nutrients for the development of the SCM. This research contributes to a better understanding of the temporal and spatial variation of SCM and nutrient supply in deep and large stratified reservoirs.

Seasonality drives the survival landscape of a recovering forest carnivore in a changing world.

Ecological heterogeneity promotes species persistence and diversity. Environmental change has, however, eroded patterns of heterogeneity globally, stifling species recovery. To test the effects of seasonal heterogeneity on a reintroduced carnivore, American martens (Martes americana), we compared metrics of local and season-specific heterogeneity to traditional forest metrics on the survival of 242 individuals across 8 years and predicted a survival landscape for 13 reintroduction sites. We found that heterogeneity-created by forest structure in the growing season and snow in the winter-improved survival and outperformed traditional forest metrics. Spatial variation in heterogeneity created a distinct survival landscape, but seasonal change in heterogeneity generated temporal discordance. All translocation sites possessed high forest heterogeneity but there were greater differences in winter heterogeneity; recovery sites with the poorest snow conditions had the lowest viability. Our work links heterogeneity across seasons to fitness and suggests that management strategies that increase seasonal aspects of heterogeneity may help to recover other sensitive species to continuing environmental change.

Pesticide fate at watershed scale: A new framework integrating multimedia behavior with hydrological processes

Pesticide pollution has been one serious ecological and environmental issue due to its wide application, high toxicity, and complex environmental behavior. The fugacity model has been widely used to quantify biogeochemical cycles of pesticides due to its clear compartments, simple structure, and easy-accessible data. However, the lack of detailed hydrological processes limits its application for large and heterogeneous watershed. In present study, a new framework was proposed through integration of hydrological processes of SWAT and pesticide fate of fugacity model, and was applied into a typical watershed in the Three Gorges Reservoir Area, China. The results showed that surface runoff, soil erosion, and percolation varied spatiotemporally, which highlighted the importance of considering regional and seasonal heterogeneity of pesticide transport variables in the fugacity model. The amount of dichlorvos (DDV) and chlorpyrifos (CHP) in air, water, soil, and sediment phase were estimated as 0.26 kg, 19.77 kg, 1.06 × 104 kg, and 0.55 kg, respectively. Spatiotemporally, pesticide concentrations in water phase peaked in summer, while the middle and southwest regions of the watershed were identified as the hotspots for pesticide pollution. Compared with the classical model, the new framework provided technical support for the pesticide assessment at watershed scale with heterogeneous hydrological conditions, which can be easily extended to other watersheds, and integrated with other models for comprehensive agricultural management.

Seasonal heterogeneity and a link to precipitation in the release of microplastic during COVID-19 outbreak from the Greater Jakarta area to Jakarta Bay, Indonesia

To reduce microplastic contamination in the environment, we need to better understand its sources and transit, especially from land to sea. This study examines microplastic contamination in Jakarta's nine river outlets. Microplastics were found in all sampling intervals and areas, ranging from 4.29 to 23.49 particles m−3. The trend of microplastic contamination tends to increase as the anthropogenic activity towards Jakarta Bay from the eastern side of the bay. Our study found a link between rainfall and the abundance of microplastic particles in all river outlets studied. This investigation found polyethylene, polystyrene, and polypropylene in large proportion due to their widespread use in normal daily life and industrial applications. Our research observed an increase in microplastic fibers made of polypropylene over time. We suspect a relationship between COVID-19 PPE waste and microplastic shift in our study area. More research is needed to establish how and where microplastics enter rivers.

Separating climate change and vegetation dynamics contributions to soil drying over drylands of China: A case study in the West Liao River Basin

AbstractSignificant soil drying has been reported in the semi‐arid Three‐North Region of China since the 1980s, yet its dominant drivers and the potential effects on dryland ecosystems are still poorly documented. In this work, the improved Vegetation Interface Processes (VIP) model was employed to characterize the spatio‐temporal pattern of the root‐zone soil moisture (RZSM) from 1982 to 2015 over the West Liao River Basin (WLRB). Results showed that RZSM decreased in most parts of the WLRB along with precipitation decline and vegetation greening. Sensitivities of RZSM to climate and vegetation dynamics exhibited obvious spatial and seasonal heterogeneity. Averaged over the whole basin, sensitivity of RZSM to precipitation (SP) is the highest. Significant seasonal differences were found in the sensitivity of RZSM to leaf area index (LAI) (SLAI). SLAI values in spring and autumn were generally negative throughout the WLRB, but prominent positive SLAI values were observed in the north‐west forest in summer, owing to the increased drier‐and‐browner associations in summer induced by the earlier spring greenness. Attribution analysis showed that relative contributions of precipitation, air temperature and LAI changes to the growing‐season RZSM (RZSMGS) drying trend were 69.0%, 17.5% and 13.5 %, respectively. It can be inferred that precipitation decrease dominated the soil drying over the WLRB, while air warming and vegetation greening accelerated this drying. In a future warming scenario without substantial increase in water use efficiency (WUE), dryland ecosystems might suffer more severe biomass losses caused by complex soil–vegetation–atmosphere interactions. This study can improve our understanding of the terrestrial–atmospheric feedbacks and their possible effects on dryland ecosystems.

Black carbon aerosols at an urban site in North Africa (Kenitra, Morocco)

Although black carbon is one of the most important atmospheric particulate components driving climate change and air quality, there is a lack of comprehensive air quality data from North African urban areas. Seven-wavelength aethalometer-collected data were used to provide first insights into the levels and patterns of equivalent black carbon (eBC) mass concentrations, particularly into the seasonal and diurnal cycles, that exist over an urban area in the North of Africa, Kenitra city, Morocco. The average BC mass concentration was observed as 0.90 ± 0.80 μg/m3. This BC value is overall largely lower than reported African and European urban location levels, although the role of COVID-19 restrictions could have influenced this result. The diurnal pattern revealed two BC peaks corresponding to morning and evening traffic rush hours. This variation is found to be seasonally dependent, with the maximum daily amplitude occurring in winter. The BC bimodal behaviour is observed in all the seasons but with varying degrees of the magnitude of the peaks (winter > autumn > summer). This observed seasonal heterogeneity was explained by varying meteorological conditions (wind speed, wind direction, relative humidity, air pressure, air temperature, rainfall, and boundary layer height), and air mass trajectory height and pathways. It was pointed out that the daily and seasonal variations are significantly influenced by local traffic sources, wind speed, and boundary layer dynamics. Hysplit backward trajectories revealed that the long-range aerosols transport through both south-western (Atlantic region), and western (over populated areas) regions can as well contribute to BC concentrations, although to a different extent. Finally, a common thread that runs through seasonal, and diurnal variations were that typical low hourly BC concentrations (distinguished in the afternoon) do not exceed the value of 0.5 μg/m3 representing a kind of urban background level.

Investigating Dissolved Organic Matter Dynamics in the Downstream Reaches of the Ganges and Brahmaputra Rivers Using Fluorescence Spectroscopy

The Ganges and the Brahmaputra, two major rivers in Bangladesh, contribute major loads of dissolved organic matter (DOM) into the Bay of Bengal. The composition, sources, availability, and seasonal heterogeneity of DOM in these two rivers are thus very important to know about the biogeochemical cycles, fate, and ecological and environmental aspects before discharge into the Bay of Bengal. In this study, DOM was characterized in the downstream reaches of the Ganges and Brahmaputra rivers before their confluence with each other. The concentration of dissolved oxygen decreased in the pre-monsoon and monsoon in both rivers due to the increased decomposition and oxidation of rainfall-washed substances and thus made the water unsuitable for drinking. The amount of total coliform also made the water of both rivers unsuitable for drinking, recreational, and irrigation purposes. In total, four DOM components (one humic, one detergent-, and two protein-like) in the Ganges River and five DOM components (three humic- and two protein-like) in the Brahmaputra River were identified at their downstream reaches using fluorescence spectroscopy, three-dimensional excitation emission matrix (EEM) measurement, and parallel factor analysis (PARAFAC). The abundances of DOM components were higher in the pre-monsoon and monsoon seasons than in the post-monsoon season. Protein-like components contributed the most in two rivers. DOM was obtained mostly from terrestrial sources and was matured and less aromatic. This study also identifies that sewage water is the largest contributor to DOM in surface water, next to natural sources, and indicates the excessive anthropogenic activities in the river basins of Bangladesh.

Non-optimum temperature increases risk and burden of acute myocardial infarction onset: A nationwide case-crossover study at hourly level in 324 Chinese cities.

SummaryBackgroundThe associations of ambient temperature with acute myocardial infarction (AMI) have seldom been examined based on the time of symptom onset.MethodsWe conducted a time-stratified case-crossover study among 1,046,773 eligible AMI patients from 2,093 hospitals in 324 Chinese cities from January 1, 2015 to June 30, 2021, after excluding those transferred from other hospitals or having not reported the time of symptom onset. Hourly exposure to ambient temperature was calculated as multiple moving 24-h averages (days) before hourly onset of AMI symptoms. Conditional logistic regression and distributed lag non-linear models with a duration of 0–21 days were used to estimate the cumulative associations of non-optimum temperature with AMI onset and the corresponding disease burden nationally. Subgroup analyses by region and period were conducted. Specifically, cities with and without centralized heating system were classified into heating and non-heating regions, respectively. The whole year in heating region was divided into heating and non-heating periods based on the duration of centralized heating in each city.FindingsAlmost monotonically increasing risks were observed for both overall AMI and its two subtypes when ambient temperature declined. The effects of extremely low temperature occurred immediately on the concurrent day, and lasted up to almost 3 weeks. The excess risks of AMI onset associated with non-optimum ambient temperatures were observed during the whole year in the non-heating region and non-heating period in the heating region, but not during heating period. Specifically, odds ratios of AMI onset associated with extremely low temperature cumulated over 0–21 days were 1.24 (95% CI: 1.13–1.37), 1.46 (95% CI: 1.20–1.76), and 1.62 (95% CI: 1.46–1.81) in the heating region during non-heating period, in the non-heating region during winter and non-winter period, respectively. The heat effects on AMI onset were very modest and transient. Totally, 13.26% of AMI cases could be attributable to non-optimum temperatures nationally. The burden of AMI attributable to non-optimum temperature was much smaller in heating region than in non-heating region. Somewhat stronger effects were observed in females and patients aged older than 65.InterpretationThis nationwide study provided robust evidence that non-optimum ambient temperature may significantly trigger AMI onset, and for the first time estimated the disease burden after accounting for spatial and seasonal heterogeneity. Centralized heating might substantially mitigate AMI burden due to non-optimum temperature.FundingShanghai International Science and Technology Partnership Project, National Natural Science Foundation of China, Talent Training Program of Zhongshan Hospital, Fudan University.

Spatial distribution and source identification for heavy metals in surface sediments of East Dongting Lake, China

Dongting Lake is one of the most important inland freshwater lakes in China. To investigate the spatial distribution and seasonal variation characteristics of heavy metals (Cr, Co, Cu, Zn, Cd, and Pb) in the lake, 53 surface sediment samples were collected in the East Dongting Lake (ED Lake) in the wet and dry seasons. Results show Cr, Co, Cu, Zn, Cd, and Pb contents were 1.7 (1.9), 1.8 (2.0), 2.9 (3.0), 1.9 (1.9), 11.7 (13.1), and 2.0 (2.2)-fold of their geochemical soil background values of Hunan province (China) in the wet (dry) season. Spatial and seasonal heterogeneity could be found in the distribution of Cr, Co, Cu, Zn, and Pb in the surface sediments. The enrichment factor (EF) suggested that Cd has reached severe enrichment in the sediment. The result of the geo-accumulation index ({I}_{geo}) indicated that Cr, Co, Cu, Zn, and Pb were at levels corresponding to low contamination, and moderately to highly polluted with Cd. Multivariate statistical analysis including pearson correlation analysis and principal component analysis was used for the identification of potential sources of the heavy metals in the sediments. The results showed that Cu, Zn, and Pb from the sediments of the East Dongting Lake in the wet and dry seasons were possibly anthropogenic sources, such as emissions from mining and smelting while Al, Fe, and Cr are attributed for natural sources. Cd enrichment in the sediments is influenced by both natural factors, and human activities in local areas.

The Diel and Seasonal Heterogeneity of Carbonate Chemistry and Dissolved Oxygen in Three Types of Macroalgal Habitats

As concerns about ocean acidification continue to grow, the importance of macroalgal communities in buffering coastal seawater biogeochemistry through their metabolisms is gaining more attention. However, studies on diel and seasonal fluctuations in seawater chemistry within these communities are still rare. Here, we characterized the spatial and temporal heterogeneity in diel and seasonal dynamics of seawater carbonate chemistry and dissolved oxygen (DO) in three types of macroalgal habitats (UAM: ulvoid algal mat dominated, TAM: turf algal mat dominated, and SC: Sargassum horneri and coralline algae dominated). Our results show that diel fluctuations in carbonate parameters and DO varied significantly among habitat types and seasons due to differences in their biological metabolisms (photosynthesis and calcification) and each site’s hydrological characteristics. Specifically, carbonate parameters were most affected by biological metabolisms at the SC site, and by environmental variables at the UAM site. Also, we demonstrate that macroalgal communities reduced ocean acidification conditions when ocean temperatures supported photosynthesis and thereby the absorption of dissolved inorganic carbon. However, once temperatures exceeded the optimum ranges for macroalgae, respiration within these communities exceeded photosynthesis and increased CO2 concentrations, thereby exacerbating ocean acidification conditions. We conclude that the seawater carbonate chemistry is strongly influenced by the metabolisms of the dominant macroalgae within these different habitat types, which may, in turn, alter their buffering capacity against ocean acidification.