Hydrochemistry dynamics in a glacierized headwater catchment of Lhasa River, Tibetan Plateau

Mountain glaciers are essential for supplying water resources that sustain downstream communities and livelihoods, yet the hydrogeochemical dynamics at glacier terminals and the impact of glacier retreat on downstream water chemistry are not fully understood. This study addresses this by conducting comprehensive observations and analysis of water chemistry at refined spatial and temporal resolutions in the Lhasa River Valley Glacier No. 1 (LRVG-1) catchment, a vital source of drinking and irrigation water for the local population on the Tibetan Plateau. Our findings reveal a weakly alkaline water environment within this glacierized basin, with HCO3- and Ca2+ as the dominant anions and cations, respectively, resulting in a hydrochemical pattern classified as HCO3--Ca2+ type. Solute concentrations increase along the glacier meltwater pathway, influenced by water-rock interaction, dilution, and diverse sources. The cations are predominantly from carbonate weathering, constituting 72.86 % of the total cations, followed by sulfide oxidation (11.08 %), glacier meltwater inputs (8.13 %), and silicate weathering (7.93 %). The contribution of cations from glacier meltwater diminishes as they travel along the glacier meltwater flow pathway. Our study indicates the localized yet significant impact of glacier meltwater on hydrochemistry, particularly in the vicinity of the glacier terminus. We recommend considering glacial meltwater and the entire glacier watershed as a continuum, essential for understanding the cumulative effects of glacier melt and human activities on water quality. This perspective is crucial for predicting future river chemistry trajectories in high-mountain basins and informing policy-making for water quality conservation across the Tibetan Plateau.

Occurrence of pentachlorophenol in surface water from the upper to lower reaches of the Yangtze River and treated water in Wuhan, China

Pentachlorophenol (PCP), a persistent organic pollutant, has been banned in many countries, but it is still used in China as a wood preservative, molluscicide, or reagent for fish-pond cleaning, which may pose risks to the ecosystem and humans. However, data on the occurrence of PCP in the environment are scarce in the recent decade. The Yangtze River was regarded as a priority area of PCP pollution according to previous documents. This study aimed to examine the spatial distribution of PCP in the Yangtze River water, the differences in dry and wet seasons, the ecological risk for aquatic organisms, and its removal efficiency in tap water treatment plants. The river water samples (n = 144) were collected from the upper, middle, and lower reaches across ten provinces (or municipalities) in December 2020 and June 2021, respectively. PCP was detected in 88.9% of all the samples, ranging from  Collapse

Key Words

• Pentachlorophenol
• Removal
• Seasonal difference
• Spatial variations
• Surface water
• Yangtze River

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MESH Headings

• Humans
• Animals
• Pentachlorophenol/analysis
• Ecosystem
• Water Pollutants, Chemical/analysis
• Environmental Monitoring
• Rivers
• Cities
• China
• Risk Assessment
• Aquatic Organisms

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Grants

• WJ2019H307 Health Commission of Hubei Province
• WJ2019H303 Health Commission of Hubei Province
• 42277428 National Natural Science Foundation of China
• 21407117 National Natural Science Foundation of China

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Affiliation(s)

Fengting Yang Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, Hubei, China
Yanjian Wan Center for Public Health Laboratory Service, Institute of Environmental Health, Wuhan Centers for Disease Prevention & Control, Wuhan, Hubei, 430024, People's Republic of China
Yan Wang Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, Hubei, China
Shulan Li Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, Hubei, China
Shunqing Xu Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, Hubei, China
Wei Xia Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, 13 Hangkong Road, Wuhan, 430030, Hubei, China.

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Spatial variations in the associations of surface water quality with roads and traffic across an urbanization gradient in northern Georgia, USA

Roads and traffic are important elements of urbanization, but their spatial associations with surface water quality in watersheds have been seldom studied. In this study, the spatially varying associations of three urbanization indicators, including road density, traffic density, and percentages of urban land, with twenty water quality indicators, including dissolved oxygen (DO), specific conductance (SC), dissolved solids (DS), suspended solids (SS), biochemical oxygen demand (BOD), dissolved nutrients, dissolved ions, heavy metals, and coliform bacteria, across the watersheds in the northern part of the state of Georgia, USA, have been examined by a conventional statistical method, ordinary least squares regression (OLS), and a spatial statistical method, geographically weighted regression (GWR). The results from OLS show that the urbanization indicators all have significant positive associations with the majority of the studied water pollutants, indicating that water pollution is significantly contributed by human activities related to urbanization in northern Georgia. In contrast, GWR results show that the associations vary across the watersheds affected by their urbanization levels. Significant positive associations are found between each urbanization indicator and each of the studied water pollutants, but not in all watersheds. The associations of suspended solids, nitrogen nutrients, and coliform bacteria with all three urbanization indicators are more significant in less-urbanized watersheds, while the associations of dissolved ions, BOD, and orthophosphate (PO4) with road density and traffic density are more significant than those with urban land in more-urbanized watersheds, indicating that those water pollutants are more contributed by human activities associated with roads and traffic than other activities in more-urbanized areas. As a pilot study to explore how and why the associations of surface water quality with roads and traffic change across watersheds with different urbanization levels, its findings suggest that the policies of watershed management, land-use planning, and transportation planning should be tailored in local areas based on the locally important water pollutants and their associated urbanization indicators.

Animal production predominantly contributes to antibiotic profiles in the Yangtze River

Human-induced antibiotic pollution in the world's large rivers poses significant risk to riverine ecosystems, water quality, and human health. This study identified geophysical and socioeconomic factors driving antibiotic pollution in the Yangtze River by quantifying 83 target antibiotics in water and sediment samples collected in its 6300-km-long reach, followed by source apportionment and statistical modeling. Total antibiotic concentrations ranged between 2.05-111 ng/L in water samples and 0.57-57.9 ng/g in sediment samples, contributed predominantly by veterinary antibiotics, sulfonamides and tetracyclines, respectively. Antibiotic compositions were clustered according to three landform regions (plateau, mountain-basin-foothill, and plains), resulting from varying animal production practices (cattle, sheep, pig, poultry, and aquaculture) in the sub-basins. Population density, animal production, total nitrogen concentration, and river water temperature are directly associated with antibiotic concentrations in the water samples. This study revealed that the species and production of food animals are key determinants of the geographic distribution pattern of antibiotics in the Yangtze River. Therefore, effective strategies to mitigate antibiotic pollution in the Yangtze River should include proper management of antibiotic use and waste treatment in animal production.

Temporal and spatial relationships of CrAssphage and enteric viral and bacterial pathogens in wastewater in North Carolina

Enteric disease remains one of the most common concerns for public health, particularly when it results from human exposure to surface and recreational waters contaminated with wastewater. Characterizing the temporal and spatial variation of enteric pathogens prevalent in wastewater is critical to develop approaches to mitigate their distribution in the environment. In this study, we aim to characterize pathogen variability and test the applicability of the human-associated wastewater indicator crAssphage as an indicator of enteric viral and bacterial pathogens. We conducted weekly samplings for 14 months from four wastewater treatment plants in North Carolina, USA. Untreated wastewater samples were processed using hollow fiber ultrafiltration, followed by secondary concentration methods. Adenovirus, norovirus, enterovirus, Salmonella, Shiga toxin 2 (stx2), Campylobacter, and crAssphage were measured by quantitative polymerase chain reaction (qPCR) and reverse transcriptase (rt)-qPCR. Our results revealed significant correlations between crAssphage and human adenovirus, enterovirus, norovirus, Salmonella, and Campylobacter (p<0.01). Pathogens and crAssphage concentrations in untreated wastewater showed distinct seasonal patterns, with peak concentrations of crAssphage and viral pathogens in fall and winter, while bacterial pathogens showed peaked concentrations in either winter (Campylobacter), fall (Salmonella), or summer (stx2). This study enhances the understanding of crAssphage as an alternative molecular indicator for both bacterial and viral pathogens. The findings of this study can also inform microbial modeling efforts for the prediction of the impact of wastewater pathogens on surface waters due to increased flooding events and wastewater overflows associated with climate change.

How does anthropogenic activity influence the spatial distribution of dissolved organic matter in rivers of a typical basin located in the Loess Plateau, China

River ecosystems interact strongly with adjacent terrestrial environments and receive dissolved organic matter (DOM) from a variety of sources, all of which are vulnerable to human activities and natural processes. However, it is unclear how and to what extent human and natural factors drive DOM quantity and quality changes in river ecosystems. Here, three fluorescence components were identified via optical techniques, including two humic-like substances and one protein-like component. The protein-like DOM was mainly accumulated in anthropogenically impacted regions, while humic-like components exhibit the opposite trend. Furthermore, the driving mechanisms of both natural and anthropogenic factors on the variations in DOM composition were investigated using partial least squares structural equation modelling (PLS-SEM). Human activities, especially agriculture, positively influence the protein-like DOM directly by enhancing anthropogenic discharge with protein signals and also indirectly by affecting water quality. Water quality directly influences the DOM composition by stimulating in-situ production through a high nutrient load from anthropogenic discharge and inhibiting the microbial humification processes of DOM due to higher salinity levels. The microbial humification processes can also be restricted directly by a shorter water residence time during the DOM transport processes. Furthermore, protein-like DOM was more sensitive to direct anthropogenic discharge than indirect in-situ production (0.34 vs. 0.25), especially from non-point source input (39.1%), implying that agricultural industry optimization may be an efficient way to improve water quality and reduce protein-like DOM accumulation.

Identifying and characterizing frequency and maximum durations of surface urban heat and cool island across global cities

Surface urban heat island (SUHI) has been widely reported from a local to global scale. However, variations and controls of temporal indicators for SUHI and SUCI (surface urban cool island) remain unclear. This paper firstly reconstructed the seamless daily LST (land surface temperature) based on ATC-SKT (annual temperature cycle-skin temperature) and comprehensively validated for SUHI applications across 1112 global cities. Based on the seamless daily LST, this paper further characterized the spatiotemporal variations of the frequency (SUHIF and SUCIF) and maximum duration (SUHID and SUCID) and investigated the impacts from related factors, inconsideration of the different characteristics of SUHI and SUCI. There are five major findings. (1) The seamless daily LST reconstructed based on ATC-SKT is validated through pixel-based temperature and city-based SUHII accuracy assessments. (2) The selection of the frequency threshold is based on robustness for LST accuracy, approximation to SUHII global average, and mitigation of frequency saturation. (3) The average daytime SUHIF is 214 days/year, with 44 % of cities exhibiting SUHI occurrences for almost every day in summer. The nighttime SUHIF is 175 days/year, with increasing latitudinal variations from equatorial to polar regions. The daytime SUCIF is 41 days/year, with the greatest average frequency of 172 days/year exhibited in arid regions. (4) The average SUHID is 147 days at daytime and 58 days at nighttime, with relatively opposite geographical distributions between day and night. (5) Greater vegetation difference at daytime and greater albedo difference at nighttime result in more occurrences and longer consecutive durations of SUHI, with opposite effects on the temporal indicators of SUCI. Furthermore, the improvements in daily SUHII and impacts from the maximum duration were discussed. This paper aims to identify and highlight the period with significant SUHI and SUCI effects across global cities for further mitigation.

Spatial distribution and determinants of newbornsnot receiving postnatal check-up withintwodays after birth in Ethiopia: a spatial and multilevel analysis of EDHS 2016

Background

Accessibility and utilization of postnatal newborn check-ups within 2 days after delivery are critical for a child’s survival, growth, and development. However, the service delivery is not yet improved and fluctuates across the geographical locations in Ethiopia. Therefore, this study aimed to assess the spatial distribution and determinants of newborns not received postnatal check-ups within 2 days after birth in Ethiopia.

Methods

A secondary data analysis of the Ethiopia Demographic and Health Survey (EDHS) 2016 was done among live births within 2 years preceding the survey. A multilevel binary logistic regression model was fitted to identify the factors associated with the outcome variable. Adjusted Odds Ratio with 95% (Confidence Interval) was calculated and used as a measure of associations and variables with a p-value < 0.05, were declared as statistically significant.

Results

A total of 4036 live newborns in Ethiopia were included in the analysis, of whom half (51.21%) were females. The mean age of the mothers was 33+ SD 1.3, and more than 60 % (61.56%) of the mothers were not educated. The national prevalence of newborns not receiving postnatal check-ups within 2 days after birth was 84.29 (95% CI: 83.10–85.41) with significant spatial variations across the study area. Mothers who had no ANC visits were 58% higher than (AOR = 0.42(0.27–0.66) mothers who had > 4 ANC visits. Mothers who gave birth at home and others were 80% (AOR = 0.02(0.01–0.29) and 25% (AOR = 0.76(0.59–0.99), higher than mothers delivered at hospital. Rural mothers were 1.90 times higher (AOR = 1.90(1.29–2.81) than urban mothers, and mothers live in administrative regions of Afar 66% (AOR = 0.34(0.16–0.69), Oromia 47% (AOR = 0.53(0.30–0.91), Somali 60% (AOR = 0.40 (0.22–0.74),Benishangul 50% (AOR = 0.50 (0.27–0.92), SNNPR 67% (AOR = 0.33(0.19–0.57), Gambela 70% (AOR = 0.30 (0.16–0.56), Harari 56% (AOR = 0.44 (0.25–0.78), and Dire Dawa70% (AOR = 0.30 (0.17–0.54) were higher than Addis Abeba for not receiving postnatal checkup of new born within the first 2 days, respectively.

Conclusions

Low postnatal check-up utilization remains a big challenge in Ethiopia, with significant spatial variations across regional and local levels. Spatial clustering of not receiving postanal check-ups within 2 days was observed in Afar, Oromia, Gambela, Benishangul, SNNPR, Harari, and Dire Dawa regions. Residence, ANC visits, place of delivery, and administrative regions were significantly associated with not receiving postnatal check-ups. Geographically targeted interventions to improve ANC follow-up and institutional delivery should be strengthened.

Spatial variations on the hydrochemistry, controls, and solute sources of surface water in the Weihe River Basin, China

The Weihe River Basin (WRB), the largest tributary of the Yellow River Basin (YRB), is located in the northwest of China. As the "mother river" of the Guanzhong Plain, it plays an important role in the development of Guanzhong City Group. Based on pH, electric conductivity (EC), total dissolved solids (TDS), and major ionic concentrations of 227 samples collected from the main stream (MS), northern tributaries (NT), and southern tributaries (ST) of the WRB, we explored spatial differential characteristics of hydrochemistry and their controlling factors, solute sources, and water quality of surface water. The results revealed mildly alkaline pH and much higher TDS values than the global average with mean values of 7.9 and 1037.7 mg L^-1, respectively. Except NO₃^-, the concentrations of major ions in the MS and NT were higher than those of the ST, with similar spatial distribution patterns of Ca²⁺, Na⁺, Mg²⁺, SO₄^2-, and Cl^-. Na⁺ and SO₄^2- were the most dominant cation and anion in the MS and NT controlled by both rock weathering and evaporation-crystallization processes. Ca²⁺ and HCO₃^- were the most dominant cation and anion in the ST mainly controlled by rock weathering process. Evaporite dissolution contributed the most to dissolved solutes in the MS and NT, while carbonate weathering dominated dissolved solutes in the ST. These findings were confirmed by the results of correlation matrix, principal component analysis (PCA), stoichiometric plots, and different water types identified as Na-SO₄·Cl in the MS and NT, and Ca-HCO₃ in the ST. Atmospheric and anthropogenic inputs had a minor effect on the surface water chemistry. However, human activities could not be ignored in the ST accounting for 10.9% of the total dissolved solutes, mainly because of the fertilizer application. And the surface water of the ST was more suitable for irrigation and drinking purposes than that of the MS and NT. Knowledge of our findings could contribute new insights to the solute geochemistry and sustainable management of water resources in the lithologically distinct segments of the WRB and other similar areas.

Spatial variations and social determinants of life expectancy in China, 2005-2020: A population-based spatial panel modelling study

BACKGROUND

Social determinants of health (SDOH) produce a broad range of life expectancy (LE) disparities. In China, limited literatures were found to report association between SDOH and LE at ecological level during a consecutive period of time from the spatial perspectives. This study aimed to determine the existence, quantify the magnitude, and interpret the association between SDOH and LE in China.

METHODS

Provincial-level LE were estimated from mortality records during 2005-2020 from National Mortality Surveillance System in China. A spatial panel Durbin model was used to investigate LE associated SDOH proxies. Spatial spillover effects were introduced to interpret direct and indirect effects caused by SDOH during long-term and short-term period on LE disparities.

FINDINGS

Nationwide, LE increased from 73.1 (95% confidence interval (CI): 71.3, 74.4) years to 77.7 (95%CI: 76.5, 78.7) years from 2005 to 2020. Unequally spatial distribution of LE with High-High clustering in coastal areas and Low-Low clustering in western regions were observed. Locally, it was estimated that SDOH proxies statistically significant related to an increase of LE, including GDP (coefficient: 0.02, 95%CI: 0.00, 0.03), Gini index (coefficient: 2.35, 95%CI: 1.82, 2.88), number of beds in health care institutions (coefficient: 0.02, 95%CI: 0.00, 0.05) and natural growth rate of resident population (coefficient: 0.02, 95%CI: 0.01, 0.02). Direct and indirect effects decomposition during long-term and short-term of LE associated SDOH proxies demonstrated that GDP, urbanization rate, unemployment rate, education attainment, Gini index, number of beds in health care institutions, sex ratio, gross dependence ratio and natural growth rate of resident population not only affected local LE, but also exerted spatial spillover effects towards geographical neighbors.

INTERPRETATION

Spatial variations of LE existed at provincial-level in China. SDOH regarding socioeconomic development and equity, healthcare resources, as well as population characteristics not only affected LE disparities at local scale but also among nearby provinces. Externalities of policy of those SDOH proxies should be took into consideration to promote health equity nationally. Comprehensive approaches on the basis of population strategy should be consolidated to optimize supportive socioeconomic environment and narrow the regional gap to reduce health disparities and increase LE.

FUNDING

National Key Research & Development Program of China (Grant No.2018YFC1315301); Ministry of Education of China Humanities and Social Science General Program (Grant No.18YJC790138).

Drinking water elements constituent profiles and health risk assessment in Wuxi, China

Water elements pollution has attracted public attention globally. Wuxi is located in East China, and its water source, Taihu Lake, has been severely polluted since 2007. Studies of elemental pollution profiles have yet to be conducted in this area. In this study, 56 water samples were collected in 2018, and 33 elements were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results showed that the levels of 33 elements ranged from 1.35 × 10^-3 μg/L(Tl) to 101 mg/L(Ca), with Sr, Al, Fe, B, Ti, Ba, and Zn levels being relatively higher. A comprehensive literature review showed spatial distribution of conspicuous elements in drinking water worldwide. Meanwhile, Monte Carlo simulations were applied to evaluate exposure health risks. The total hazard index(HI) for 14 non-carcinogens and the average incremental lifetime cancer risk (ILCR) of As and Pb exposure through drinking water were found acceptable. Sensitivity analyses suggested that Sb and As in the drinking water represent an increasing risk to human health. The results of this study provide key data on local metal pollution characteristics, help identify potential risk factors, and contribute to the development of effective environmental management policies for Taihu Lake.

NPAHs and OPAHs in the atmosphere of two central European cities: Seasonality, urban-to-background gradients, cancer risks and gas-to-particle partitioning

Derivatives of polycyclic aromatic hydrocarbons (PAHs) such as nitrated- and oxygenated-PAHs (NPAHs and OPAHs) could be even more toxic and harmful for the environment and humans than PAHs. We assessed the spatial and seasonal variations of NPAHs and OPAHs atmospheric levels, their cancer risks and their gas-to-particle partitioning. To this end, about 250 samples of fine particulate matter (PM2.5) and 50 gaseous samples were collected in 2017 in central Europe in the cities of Brno and Ljubljana (two traffic and two urban background sites) as well as one rural site. The average particulate concentrations were ranging from below limit of quantification to 593 pg m-3 for Σ9NPAHs and from 1.64 to 4330 pg m-3 for Σ11OPAHs, with significantly higher concentrations in winter compared to summer. In winter, the particulate levels of NPAHs and OPAHs were higher at the traffic site compared to the urban background site in Brno while the opposite was found in Ljubljana. NPAHs and OPAHs particulate levels were influenced by the meteorological parameters and co-varied with several air pollutants. The significance of secondary formation on the occurrence of some NPAHs and OPAHs is indicated. In winter, 27-47% of samples collected at all sites were above the acceptable lifetime carcinogenic risk. The gas-particle partitioning of NPAHs and OPAHs was influenced by their physico-chemical properties, the season and the site-specific aerosol composition. Three NPAHs and five OPAHs had higher particulate mass fractions at the traffic site, suggesting they could be primarily emitted as particles from vehicle traffic and subsequently partitioning to the gas phase along air transport. This study underlines the importance of inclusion of the gas phase in addition to the particulate phase when assessing the atmospheric fate of polycyclic aromatic compounds and also when assessing the related health risk.

Machine learning algorithms for predicting undernutrition among under-five children in Ethiopia

OBJECTIVE

Child undernutrition is a global public health problem with serious implications. In this study, we estimate predictive algorithms for the determinants of childhood stunting by using various machine learning (ML) algorithms.

DESIGN

This study draws on data from the Ethiopian Demographic and Health Survey of 2016. Five ML algorithms including eXtreme gradient boosting, k-nearest neighbours (k-NN), random forest, neural network and the generalised linear models were considered to predict the socio-demographic risk factors for undernutrition in Ethiopia.

SETTING

Households in Ethiopia.

PARTICIPANTS

A total of 9471 children below 5 years of age participated in this study.

RESULTS

The descriptive results show substantial regional variations in child stunting, wasting and underweight in Ethiopia. Also, among the five ML algorithms, xgbTree algorithm shows a better prediction ability than the generalised linear mixed algorithm. The best predicting algorithm (xgbTree) shows diverse important predictors of undernutrition across the three outcomes which include time to water source, anaemia history, child age greater than 30 months, small birth size and maternal underweight, among others.

CONCLUSIONS

The xgbTree algorithm was a reasonably superior ML algorithm for predicting childhood undernutrition in Ethiopia compared to other ML algorithms considered in this study. The findings support improvement in access to water supply, food security and fertility regulation, among others, in the quest to considerably improve childhood nutrition in Ethiopia.

Occurrence of areca alkaloids in wastewater of major Chinese cities

Areca nut is a widely used psychoactive product that can cause multiple health problems, such as oral and pharyngeal cancers. Therefore, it is important to estimate areca nut use and the exposure levels of areca alkaloids that are responsible for its health effects. China is a major producer of areca nut and has a large number of areca nut chewers. In this study, occurrence of areca alkaloids and metabolites in wastewater of major cities across China was examined via wastewater-based epidemiology (WBE). Arecoline, arecaidine, and their metabolite, N-methylnipecotic acid (NMNA) were detected in the overwhelming majority of wastewater samples, with concentrations up to several μg/L. In contrast, guvacoline was only occasionally detected and guvacine was below detection limit in all samples, possibly due to their low contents in areca nut products, low excretion rates, and/or low stability in sewer systems. Strong positive correlations existed between arecoline, arecaidine, and NMNA concentrations. In addition, their loads were much higher in Central and Southern China. This geographic pattern is consistent with previous survey results on prevalence of areca nut chewing. These results indicate that WBE is a potentially useful method to monitor areca nut consumption and to estimate the exposure levels of areca alkaloids.

Occurrence and abundance of poly- and perfluoroalkyl substances (PFASs) on microplastics (MPs) in Pearl River Estuary (PRE) region: Spatial and temporal variations

Although the occurrence and distribution of various chemicals on microplastics (MPs) has been widely studied, little was known about the concentrations of poly- and perfluoroalkyl substances (PFASs) on MPs. In this study, MPs from eight rivers draining into Pearl River Estuary (PRE) region were collected and analyzed. Higher concentrations of PFASs on MPs (105-9.07 × 10³ ng g^-1) were found in the drain outlets receiving wastewater from most urbanized cities with large population densities. On the other hand, lower concentrations of PFASs on MPs (10.3-227.8 ng g^-1) were found in the drain outlets receiving wastewater mostly from agricultural and forested areas. Specially, 8:2 disubstituted polyfluoroalkyl phosphates (8:2 diPAP) was detected with the highest frequency, in 92.5% of the samples. Furthermore, a positive Spearman correlation was found between 6:2 disubstituted polyfluoroalkyl phosphates (6:2 diPAP) and perfluorotetradecanoic acid (PFTeDA) (r_s = 0.621, p = 0.012), indicating they might share similar sources. PFASs on MPs were found to vary significantly with different seasons. Higher concentrations of PFASs on MPs were found in dry seasons, while lower concentrations were observed in wet seasons. The results of this study should be important for the understanding of PFAS occurrence and distribution on MPs and the partitioning mechanism of PFASs on MPs in estuary systems.

Competing PM2.5 and NO2 holiday effects in the Beijing area vary locally due to differences in residential coal burning and traffic patterns

The holiday effect is a useful tool to estimate the impact on air pollution due to changes in human activities. In this study, we assessed the variations in concentrations of fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) during the holidays in the heating season from 2014 to 2018 based on daily surface air quality monitoring measurements in Beijing. A Generalized Additive Model (GAM) is used to analyze pollutant concentrations for 34 sites by comprehensively accounting for annual, monthly, and weekly cycles as well as the nonlinear impacts of meteorological factors. A Saturday effect was found in the downtown area, with about 4% decrease in PM_2.5 and 3% decrease in NO₂ relative to weekdays. On Sundays, the PM_2.5 concentrations increased by about 5% whereas there were no clear changes for NO₂. In contrast to the small effect of the weekend, there was a strong holiday effect throughout the region with average increases of about 22% in PM_2.5 and average reductions of about 11% in NO₂ concentrations. There was a clear geographical pattern in the strength of the holiday effect. In rural areas the increase in PM_2.5 is related to the proportion of coal and biomass consumption for household heating. In the suburban areas between the Fifth Ring Road and Sixth Ring Road there were larger reductions in NO₂ than downtown which might be due to decreased traffic as many people return to their hometown for the holidays. This study provides insights into the pattern of changes in air pollution due to human activities. By quantifying the changes, it also provides insights for improvements in air quality due to control policies implemented in Beijing during the heating season.

Qualitative assessment of 27 current-use pesticides in air at 20 sampling sites across Africa

Increasing use of current-use pesticides (CUPs) in Africa raises environmental and public health concerns. But there is a large uncertainty about their occurrence and the composition of pesticide mixtures on this continent. This paper investigates the presence of 27 CUPs in air across 20 sampling sites in Africa. 166 passive air samples, consisting of polyurethane foam (PUF), were collected in 12 African countries between 2010 and 2018. Samples were extracted with methanol and analyzed via high-performance liquid chromatography coupled with tandem mass spectrometry. The detection frequencies of CUPs per site were compared to land use patterns and sampling years, while their similarities were assessed using hierarchical cluster analysis. Overall, 24 CUPs were detected at least once. In 93% of all samples, at least one CUP was detected, while 78% of the samples had mixtures of two or more CUPs (median 3, interquartile range 5). Atrazine and chlorpyrifos were detected in 19 out of 20 sampling sites. Carbaryl, metazachlor, simazine, tebuconazole and terbuthylazine had the highest detection frequencies at sampling sites dominated by croplands. Across all the sampling years, 16 CUPs were present. Seven CUPs were newly detected from 2016 onwards (azinfos-methyl, dimetachlor, chlorsulfuron, chlortoluron, isoproturon, prochloraz and pyrazon), while metamitron was only present before 2012. Sites within a radius of about 200 km showed similarities in detected CUP mixtures across all samples. Our results show the presence of CUP mixtures across multiple agricultural and urban locations in Africa which requires further investigation of related environmental and human health risks.

Evaluation of Salix alba, Juglans regia and Populus nigra as biomonitors of PTEs in the riparian soils of the Sava River

A large number of human activities result in the release of potentially toxic elements (PTEs) into the environment, which could lead to the degradation of riparian areas. This study aimed to evaluate the potential of Salix alba, Juglans regia and Populus nigra for the biomonitoring of PTEs in the riparian soils of the Sava River. Levels of seven PTEs (As, Cd, Cr, Cu, Ni, Pb and Zn) were measured in the soils, roots and leaves of plants at selected sampling sites and evaluated according to bioaccumulation and translocation factors. The obtained results showed that in riparian soils, As, Cr, Cu, Ni and Zn were at levels considered to be critical for plants. The levels of As, Cd, Cr, Ni and Zn measured in roots of Salix alba and As, Cr, Ni and Zn in its leaves were toxic for plant tissue. Toxic levels of Cr were also measured in the roots of Juglans regia and As in its leaves, as well as As and Cr in the roots of Populus nigra, and Zn in its leaves. Bioconcentration and translocation factors showed that S. alba and P. nigra have potential for the phytoextraction of Zn and Cd, while J. regia has potential for the phytoextraction of As. In terms of phytostabilization potential, S. alba proved to be good for the phytostabilization of Cd and Cu, and J. regia for the phytostabilization of Cr, As, Ni and Pb, while P. nigra showed potential for the phytostabilization of Cr, Ni, Pb and Cu.

Antenatal care use in Ethiopia: a spatial and multilevel analysis

BACKGROUND

Accessibility and utilization of antenatal care (ANC) service varies depending on different geographical locations, sociodemographic characteristics, political and other factors. A geographically linked data analysis using population and health facility data is valuable to map ANC use, and identify inequalities in service access and provision. Thus, this study aimed to assess the spatial patterns of ANC use, and to identify associated factors among pregnant women in Ethiopia.

METHOD

A secondary data analysis of the 2016 Ethiopia Demographic and Health Survey linked with the 2014 Ethiopian Service Provision Assessment was conducted. A multilevel analysis was carried out using the SAS GLIMMIX procedure. Furthermore, hot spot analysis and spatial regressions were carried out to identify the hot spot areas of and factors associated with the spatial variations in ANC use using ArcGIS and R softwares.

RESULTS

A one-unit increase in the mean score of ANC service availability in a typical region was associated with a five-fold increase in the odds of having more ANC visits. Moreover, every one-kilometre increase in distance to the nearest ANC facility in a typical region was negatively associated with having at least four ANC visits. Twenty-five percent of the variability in having at least four ANC visits was accounted for by region of living. The spatial analysis found that the Southern Nations, Nationalities and Peoples region had high clusters of at least four ANC visits. Furthermore, the coefficients of having the first ANC visit during the first trimester were estimated to have spatial variations in the use of at least four ANC visits.

CONCLUSION

There were significant variations in the use of ANC services across the different regions of Ethiopia. Region of living and distance were key drivers of ANC use underscoring the need for increased ANC availability, particularly in the cold spot regions.

Optical and molecular signatures of dissolved organic matter in Xiangxi Bay and mainstream of Three Gorges Reservoir, China: Spatial variations and environmental implications

With the on-going boom in the construction of dam reservoirs all over the world, the sources and composition of dissolved organic matter (DOM) in fluvial networks are expected to be altered. Considering the importance of DOM as a key biogeochemical component in inland waters, this might bring important ecological and environmental influences. However, limited information is available on the molecular composition of DOM in dam reservoirs. In this study, the spatial characteristics of DOM composition were investigated in Xiangxi tributary and mainstream of the Three Gorges Reservoir (TGR), the largest freshwater reservoir in the world. The concentration alteration of conservative cations revealed the water intrusion from mainstream into Xiangxi tributary, which mainly controlled the hydrological gradient. One tyrosine-like (C4), one tryptophan-like (C2), and two humic-like (C1 and C3) fluorescent components were identified in fluorescent DOM (FDOM) by parallel factor analysis (PAFACAC), potentially indicating algal, anthropogenic, and terrestrial inputs, respectively. Decreasing trends of C1, C3 and C4 components and an increasing trend of C2 component were observed from Xiangxi tributary to mainstream, indicating higher terrestrial and algal inputs but lower anthropogenic inputs in Xiangxi tributary compared to mainstream. The Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) characterization further revealed substantial heterogeneity of DOM at the molecular level. Interestingly, S-containing compounds related to synthetic surfactants were consistently detected, and their relative abundances showed an increasing trend from Xiangxi tributary to mainstream, in agreement with the distribution of the anthropogenic derived C2 component. Meanwhile, numerous lignin-like S-containing compounds were identified, likely the result of the incorporation of sulfide ions to lignin-like CHO compounds. This study represents the first molecular level characterization of DOM in the TGR system, which should aid the design and implementation of more detailed future studies.

Long-term trends and spatial patterns of PM2.5-induced premature mortality in South and Southeast Asia from 1999 to 2014

Fine particulate matter (PM_2.5) poses a potential threat to human health, including premature mortality under long-term exposure. Based on a long-term series of high-resolution (0.01°×0.01°) satellite-retrieved PM_2.5 concentrations, this study estimated the premature mortality attributable to PM_2.5 in South and Southeast Asia (SSEA) from 1999 to 2014. Then, the long-term trends and spatial characteristics of PM_2.5-induced premature deaths (1999-2014) were analyzed using trend analyses and standard deviation ellipses. Results showed the estimated number of PM_2.5-induced average annual premature deaths in SSEA was 1,447,000. The numbers increased from 1,179,400 in 1999 to 1,724,900 in 2014, with a growth rate of 38% and net increase of 545,500. Stroke and ischemic heart disease were the two principal contributors, accounting for 39% and 35% of the total, respectively. High values were concentrated in North India, Bangladesh, East Pakistan, and some metropolitan areas of Southeast Asia. An estimated 991,600 deaths in India was quantified (i.e., ~69% of the total premature deaths in SSEA). The long-term trends (1999-2014) of PM_2.5-related premature mortality exhibited consistent incremental tendencies in all countries except Sri Lanka. The findings of this study suggest that strict controls of PM_2.5 concentrations in SSEA are urgently required.

Assessment of water quality monitoring for the optimal sensor placement in lake Yahuarcocha using pattern recognition techniques and geographical information systems

Pollution and the eutrophication process are increasing in lake Yahuarcocha and constant water quality monitoring is essential for a better understanding of the patterns occurring in this ecosystem. In this study, key sensor locations were determined using spatial and temporal analyses combined with geographical information systems (GIS) to assess the influence of weather features, anthropogenic activities, and other non-point pollution sources. A water quality monitoring network was established to obtain data on 14 physicochemical and microbiological parameters at each of seven sample sites over a period of 13 months. A spatial and temporal statistical approach using pattern recognition techniques, such as cluster analysis (CA) and discriminant analysis (DA), was employed to classify and identify the most important water quality parameters in the lake. The original monitoring network was reduced to four optimal sensor locations based on a fuzzy overlay of the interpolations of concentration variations of the most important parameters.

Strong among population variation in frugivory strength by functional diverse frugivores: a 'reciprocal translocation' experiment

Fruit-frugivore interactions are critical for the dynamics and evolution of many plant communities. The strength of the interactions between a given plant species and different frugivore guilds (e.g., seed dispersers, seed predators) often vary in space due to changes in plant extrinsic factors (e.g., frugivore abundances) and plant traits (e.g., fruit size and reward). By reciprocally translocating Pyrus bourgaeana ripe fruits representative of five Mediterranean localities during 2 consecutive years, we experimentally quantified guild-specific variations among populations in frugivory strength, while accounted for plant-intrinsic and- extrinsic factors. Though overall fruit removal did not differ among localities, there were strong guild-specific differences in fruit removal strength. Fruit removal by pulp feeders, seed dispersers, and fruit predators varied among populations up to 8.5-, 5.6-, and 4.0-folds, respectively. These strong variations seemed mediated by changes in frugivore relative abundances rather than on availability of alternative fruits. As expected, all fruit traits considered (e.g., fruit size, pulp amount) markedly varied among tree populations. However, no frugivore guild showed preference for fruits from any locality, suggesting that fruit traits did not contribute much to differences in frugivory strength among populations. Since the functional diverse frugivore guilds played contrasting roles in P. bourgaeana dynamics (e.g., seed dispersal vs. seed predation), our study highlights the importance of accounting for functional diversity in frugivore guilds when estimating spatial variations in the strenght of seed dispersal. This investigation also illustrates a neglected but widely applicable experimental approach to identify the relative importance of extrinsic factors and fruit traits in mediating fruit-frugivore interactions.

Spatial variations in the occurrence of potentially genotoxic disinfection by-products in drinking water distribution systems in China

We investigated the occurrence of disinfection by-products (DBPs) with genotoxic potential in plant effluent and distribution water samples from four drinking water treatment plants in two Chinese cities using comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry. We tested the samples for 37 DBPs with genotoxic potential, which we had previously identified and prioritized in water under controlled laboratory conditions. Thirty of these DBPs were found in the water samples at detection frequencies of between 10% and 100%, and at concentrations between 3.90 and 1.77 × 10³ ng/L. Of the DBPs detected, the concentrations of 1,1,1-trichloropropan-2-one were highest, and ranged from 299 to 1.77 × 10³ ng/L with an average of 796 ng/L. The concentrations of 6-chloro-2-N-propan-2-yl-1,3,5-triazine-2,4-diamine and 2,6-ditert-butylcyclohexa-2,5-diene-1,4-dione were also much higher, and ranged from 107 to 721 ng/L, and from 152 to 504 ng/L, respectively. Concentrations of 1,1,1-trichloropropan-2-one, 2-chloro-1-phenylethanone, 2,2-dichloro-1-phenylethanone and 6-chloro-2-N-propan-2-yl-1,3,5-triazine-2,4-diamine were highest at or near the treatment plants and decreased with increasing distance from the plants. Patterns in the concentrations of benzaldehyde, 2-phenylpropan-2-ol, and 1-methylnaphthalene differed between plants. The levels of DBPs such as 4-ethylbenzaldehyde, (E)-non-2-enal, and 1-phenylethanone were relatively constant within the distribution systems, even at the furthest sampling points (20 km < d < 30 km). A risk assessment showed that there was no risk to human health. It is, however, important to note that, because of limited availability of toxicity data, only five DBPs were evaluated in this study. The risks to health associated with exposure to the target potentially genotoxic DBPs should not be ignored because of their prolonged existence in drinking water.

[A spatially explicit analysis of traffic accidents involving pedestrians and cyclists in Berlin]

BACKGROUND

In many German cities and counties, sustainable mobility concepts that strengthen pedestrian and cyclist traffic are promoted. From the perspectives of urban development, traffic planning and public healthcare, a spatially differentiated analysis of traffic accident data is decisive.

OBJECTIVES

1) The identification of spatial and temporal patterns of the distribution of accidents involving cyclists and pedestrians, 2) the identification of hotspots and exploration of possible underlying causes and 3) the critical discussion of benefits and challenges of the results and the derivation of conclusions.

MATERIAL AND METHODS

Spatio-temporal distributions of data from accident statistics in Berlin involving pedestrians and cyclists from 2011 to 2015 were analysed with geographic information systems (GIS).

RESULTS

While the total number of accidents remains relatively stable for pedestrian and cyclist accidents, the spatial distribution analysis shows, however, that there are significant spatial clusters (hotspots) of traffic accidents with a strong concentration in the inner city area.

CONCLUSIONS

In a critical discussion, the benefits of geographic concepts are identified, such as spatially explicit health data (in this case traffic accident data), the importance of the integration of other data sources for the evaluation of the health impact of areas (traffic accident statistics of the police), and the possibilities and limitations of spatial-temporal data analysis (spatial point-density analyses) for the derivation of decision-supported recommendations and for the evaluation of policy measures of health prevention and of health-relevant urban development.

Variability of chlorophyll-a concentration in the Gulf of Guinea and its relation to physical oceanographic variables

The Gulf of Guinea represents a wide tract of the African coast with complex and rich coastal ecosystems undergoing various pressures. The seasonal variations of chlorophyll-a concentration (Chla) along the Gulf of Guinea (GoG) and their relations with physical oceanographic variables were analyzed using satellite observations covering the period 2002-2012. The effects of sea surface temperature (SST), sea level anomalies (SLA), winds, geostrophic currents, eddy kinetic energy (EKE), mesoscale eddies and fronts were considered on a monthly time scale. The analysis for each unit area was carried out on a chlorophyll index (IChla) computed as the product of the mean distance from the coast to the eutrophic threshold (1 mg m^-3 isoline) and the average Chla in the eutrophic area. The study, based on satellite-derived Chla, was allowed by the unprecedented coverage given by the products distributed by the ESA Ocean Colour Climate Change Initiative (OC_CCI) resulting from the merging of data from several satellite missions. The physical variables served as potential predictors in a statistical Boosted Regression Tree (BRT) model. To account for the heterogeneous nature of the GoG, the analysis was conducted on eight systems that made up a partition of the whole region defined on the basis of the BRT model results and climatological properties. The western-most domain, from Guinea-Bissau to Sierra Leone, was associated with upwelling properties in boreal winter and appeared to share some characteristics with the overall Northwest African upwelling system. The region of Ivory Coast and Ghana also had upwelling properties but the main upwelling season was in boreal summer. In general upwelling conditions with cold SST, negative SLA, fairly strong frontal activity, and moderate winds, appeared as the environmental window most favorable to high IChla values. For these systems, the BRT model fitted the IChla data well with a percentage of explained total deviance [Formula: see text] between 70% and 91% when using only physical oceanographic variables. Finally, the systems associated with the coasts of Nigeria to Gabon showed some mixed properties, with [Formula: see text] values of 54-60%. Among these systems, a common feature seemed to be the importance of river discharge to explain IChla variations. Where possible (for the Niger River in the Nigeria system), the addition of river data as predictor in the BRT model resulted in a significant increase of [Formula: see text] to 75%. Further progress is needed to understand the observed relationships and to predict how they can evolve in the face of climate change.

Ecosystem services of human-dominated watersheds and land use influences: a case study from the Dianchi Lake watershed in China

Watersheds provide multiple ecosystem services. Ecosystem service assessment is a promising approach to investigate human-environment interaction at the watershed scale. The spatial characteristics of ecosystem services are closely related to land use statuses in human-dominated watersheds. This study aims to investigate the effects of land use on the spatial variations of ecosystem services at the Dianchi Lake watershed in Southwest China. We investigated the spatial variations of six ecosystem services-food supply, net primary productivity (NPP), habitat quality, evapotranspiration, water yield, and nitrogen retention. These services were selected based on their significance at the Dianchi Lake watershed and the availability of their data. The quantification of these services was based on modeling, value transference, and spatial analysis in combination with biophysical and socioeconomic data. Furthermore, we calculated the values of ecosystem services provided by different land use types and quantified the correlations between ecosystem service values and land use area proportions. The results show considerable spatial variations in the six ecosystem services associated with land use influences in the Dianchi Lake watershed. The cropland and forest land use types had predominantly positive influences on food productivity and NPP, respectively. The rural residential area and forest land use types reduced and enhanced habitat quality, respectively; these influences were identical to those of evapotranspiration. Urban area and rural residential area exerted significantly positive influences on water yield. In contrast, water yield was negatively correlated with forest area proportion. Finally, cropland and forest had significantly positive and negative influences, respectively, on nitrogen retention. Our study emphasizes the importance of consideration of the influences from land use composition and distribution on ecosystem services for managing the ecosystems of human-dominated watersheds.

Spatial variations in the associations of term birth weight with ambient air pollution in Georgia, USA

Birth weight is an important indicator of overall infant health and a strong predictor of infant morbidity and mortality, and low birth weight (LBW) is a leading cause of infant mortality in the United States. Numerous studies have examined the associations of birth weight with ambient air pollution, but the results were inconsistent. In this study, a spatial statistical technique, geographically weighted regression (GWR) is applied to explore the spatial variations in the associations of birth weight with concentrations of ozone (O3) and fine particulate matter (PM2.5) in the State of Georgia, USA adjusted for gestational age, parity, and six other socioeconomic, behavioral, and land use factors. The results show considerable spatial variations in the associations of birth weight with both pollutants. Significant positive, non-significant, and significant negative relationships between birth weight and concentrations of each air pollutant are all found in different parts of the study area, and the different types of the relationships are affected by the socioeconomic and urban characteristics of the communities where the births are located. The significant negative relationships between birth weight and O3 indicate that O3 is a significant risk factor of LBW and these associations are primarily located in less-urbanized communities. On the other hand, PM2.5 is a significant risk factor of LBW in the more-urbanized communities with higher family income and education attainment. These findings suggest that environmental and health policies should be adjusted to address the different effects of air pollutants on birth outcomes across different types of communities to more effectively and efficiently improve birth outcomes.

Spatial Variations of Soil Microbial Activities in Saline Groundwater-Irrigated Soil Ecosystem

Spatial variations of soil microbial activities and its relationship with environmental factors are very important for estimating regional soil ecosystem function. Based on field samplings in a typical saline groundwater-irrigated region, spatial variations of soil microbial metabolic activities were investigated. Combined with groundwater quality analysis, the relationship between microbial activities and water salinity was also studied. The results demonstrated that moderate spatial heterogeneity of soil microbial activities presented under the total dissolved solids (TDS) of groundwater ranging from 0.23 to 12.24 g L(-1). Groundwater salinity and microbial activities had almost opposite distribution characteristics: slight saline water was mainly distributed in west Baqu and south Quanshan, while severe saline and briny water were dominant in east Baqu and west Huqu; however, total AWCD was higher in the east-center and southwest of Baqu and east Huqu, while it was lower in east Baqu and northwest Huqu. The results of correlation analyses demonstrated that high-salinity groundwater irrigation had significantly adverse effects on soil microbial activities. Major ions Ca(2+), Mg(2+), Cl(-), and SO4(2-) in groundwater decisively influenced the results. Three carbon sources, carbohydrates, amines, and phenols, which had minor utilization rates in all irrigation districts, were extremely significantly affected by high-salinity groundwater irrigation. The results presented here offer an approach for diagnosing regional soil ecosystem function changes under saline water irrigation.

Toxic heavy metals in sediments, seawater, and molluscs in the eastern and western coastal waters of Guangdong Province, South China

Heavy metal concentrations and distribution were studied in sediments, seawater, and molluscs, and the possible heavy metal sources in the coastal waters of Guangdong Province, South China were discussed. The results showed that the concentrations of Cu, Pb, Zn, and Cr in sediments in eastern coastal waters were generally higher than those in the western coastal waters. However, concentrations of most metals in seawater and molluscs in western waters were higher than in the eastern waters, which was tightly related to the local economics and urbanization development, especially, the different industrial structure in two regions. The main heavy metal sources were attributed to the industrial and agricultural effluent, domestic sewage, and even waste gas. Furthermore, heavy metal contamination assessment indicated that high contamination levels of Cd, Zn, and Pb occurred in sediments in local areas, especially in the bays and harbors. The metal accumulation levels by molluscs ranked following the order of Cd > Cu > As > Zn > Pb > Cr, and the ecological risks introduced by heavy metals in different areas were in the order of Zhanjiang > Yangmao > Shantou > Shanhui.

Spatial and temporal distribution of aliphatic hydrocarbons and linear alkylbenzenes in the particulate phase from a subtropical estuary (Guaratuba Bay, SW Atlantic) under seasonal population fluctuation

Guaratuba Bay, a subtropical estuary located in the SW Atlantic, is under variable anthropogenic pressure throughout the year. Samples of surficial suspended particulate matter (SPM) were collected at 22 sites during three different periods to evaluate the temporal and spatial variability of aliphatic hydrocarbons (AHs) and linear alkylbenzenes (LABs). These compounds were determined by gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS). The spatial distributions of both compound classes were similar and varied among the sampling campaigns. Generally, the highest concentrations were observed during the austral summer, highlighting the importance of the increased human influence during this season. The compound distributions were also affected by the natural geochemical processes of organic matter accumulation. AHs were associated with petroleum, derived from boat and vehicle traffic, and biogenic sources, related to mangrove forests and autochthonous production. The LAB composition evidenced preferential degradation processes during the austral summer.

Spatial variations of bacterial community and its relationship with water chemistry in Sanya Bay, South China Sea as determined by DGGE fingerprinting and multivariate analysis

Bacteria play important roles in the structure and function of marine food webs by utilizing nutrients and degrading the pollutants, and their distribution are determined by surrounding water chemistry to a certain extent. It is vital to investigate the bacterial community's structure and identifying the significant factors by controlling the bacterial distribution in the paper. Flow cytometry showed that the total bacterial abundance ranged from 5.27 × 10(5) to 3.77 × 10(6) cells/mL. Molecular fingerprinting technique, denaturing gradient gel electrophoresis (DGGE) followed by DNA sequencing has been employed to investigate the bacterial community composition. The results were then interpreted through multivariate statistical analysis and tended to explain its relationship to the environmental factors. A total of 270 bands at 83 different positions were detected in DGGE profiles and 29 distinct DGGE bands were sequenced. The predominant bacteria were related to Phyla Protebacteria species (31 %, nine sequences), Cyanobacteria (37.9 %, eleven sequences) and Actinobacteria (17.2 %, five sequences). Other phylogenetic groups identified including Firmicutes (6.9 %, two sequences), Bacteroidetes (3.5 %, one sequences) and Verrucomicrobia (3.5 %, one sequences). Conical correspondence analysis was used to elucidate the relationships between the bacterial community compositions and environmental factors. The results showed that the spatial variations in the bacterial community composition was significantly related to phosphate (P = 0.002, P < 0.01), dissolved organic carbon (P = 0.004, P < 0.01), chemical oxygen demand (P = 0.010, P < 0.05) and nitrite (P = 0.016, P < 0.05). This study revealed the spatial variations of bacterial community and significant environmental factors driving the bacterial composition shift. These results may be valuable for further investigation on the functional microbial structure and expression quantitatively under the polluted environments in the world.

Spatial heterogeneity of lake eutrophication caused by physiogeographic conditions: An analysis of 143 lakes in China

In order to identify the effect of geographic characteristics on the variations of nutrient concentrations and the utilization efficiency of nutrients by phytoplankton, data from 143 lakes, from 2008 to 2010, including three very different types of topography, i.e., the first topography ladder (FTL), second topography ladder (STL), and third topography ladder (TTL), were statistically analyzed. Lakes in the FTL and STL, located at high elevation (above 1000 m) and low longitudes (lower than 105° E), were sporadically oligotrophic, whereas lakes in the TTL were almost all mesotrophic and eutrophic. The trophic level index (TLI) became higher with the rise of longitude. Two turning points (5 and 15°C) on the curve of TLI as function of the average annual temperature (AAT) corresponded with the AAT in different lake regions in the STL and TTL. Because the responses of TLI to AAT differ significantly, there were variations of nutrient and algal biomass concentrations in different lake regions in the same type of topography ladder. According to the differences in utilization efficiency of total nitrogen or total phosphorus by phytoplankton, China could be partitioned into six lake regions. Scientific nutrient criteria for each lake region shall be established considering these differences in China.

Distribution and accumulation of polybrominated diphenyl ethers (PBDEs) in Hong Kong mangrove sediments

Polybrominated diphenyl ethers (PBDEs) have been used extensively as brominated flame retardants in various polymers, and have become serious environmental contaminants, particularly in coastal sediments. Mangrove wetlands are important coastal ecosystems in tropical and subtropical regions, and mangrove sediments are often the pollutant sinks due to their close proximity with human activities. In Hong Kong, sediment samples collected from five mangrove swamps were found to be contaminated with PBDEs and the eight measured BDE congeners, including BDE-28, -47, -99, -100, -153, -154, -183 and -209 were detected in all mangrove sediments, indicating that these pollutants were widespread in Hong Kong mangrove wetlands. Among the five swamps, relatively high concentrations of PBDEs were recorded in Mai Po mangrove swamp in the northwestern Hong Kong, which is part of the RAMSAR site but is severely influenced by the pollution from the Pearl River Delta. The depth profile of PBDEs in sediment cores collected from Mai Po also showed the inputs of PBDEs in this mangrove swamp increased year by year. In all sediments, the concentrations of BDE-209 were 1-2 orders of magnitude higher than the other congeners in the same sediment. The concentrations of BDE-209 and ∑PBDEs (defined as the sum of seven targeted BDE congeners except BDE-209) ranged from 1.53 to 75.9 ng g(-1) and from 0.57 to 14.4 ng g(-1), respectively. Among the targeted BDE congeners except BDE-209, slightly different composition was recorded among samples collected from different locations, with BDE-153 and -183 being the pre-dominated congeners. In all mangrove swamps, except Tai O in the southwest of Hong Kong, ∑PBDEs concentrations showed a common trend of landward>seaward>mudflat. The concentrations of ∑PBDEs were significantly correlated with total organic matter (TOM) content in sediments but not with the sediment particle sizes in each mangrove swamp.