Thirty years(1984–2014) of groundwater science teaching and research in China: A dissertation-based bibliometric survey

In order to track the footprint of groundwater science teaching and research in China during the past years, a bibliometric analysis was conducted based on the database of China National Knowledge Infrastructure(CNKI), which covered the time span from 1984 to present and included more than 2.6 million master and doctoral dissertations from hundreds of institutions of China's Mainland. The bibliometric analysis summarized output, geographical, and institutional patterns, as well as research directions and hotspots in groundwater studies in China in the period of 1984-2014. A total of 1 396 groundwater-related dissertations including 1 161 master dissertations and 235 doctoral dissertations, contributed by 128 institutions distributed in 53 cities nationwide, were searched out in the database. It can be seen obviously that, the groundwater science teaching and research in China has experienced a notable growth in the past three decades especially during 2000-2014. Groundwater modeling, resource, and exploitation were the top three major subject categories; China University of Geosciences(Beijing), Jilin University and Chang’an University were the top three productive institutions together accounting for more than one third of the total dissertations and 50% of the doctoral dissertations, which further prompted the cities(Beijing, Changchun, and Xi’an) to become the top three productive cities. The dissertations generally covered all the international research topics, which indicated that hydrogeologists in China have tracked the international frontier closely during the past decades. The keywords analysis revealed that,(1) numerical modeling was still the hottest topic and PHREEQC, MODFLOW, GMS, and FEFLOW were the four most used softwares;(2) the topics related with groundwater pollution and quality developed steadily and rapidly;(3) environmental isotopes and GIS were frequently used tools for hydrogeological condition analysis, and spatial data processing respectively; and(4) the unsaturated zone as an integral part of aquifers attracted more and more attentions from hydrogeologists focus on saturated zone.

Seasonal variations in sulfur isotopic composition of dissolved SO_4^(2-) in the Aha Lake, Guiyang and their implications

The Aha Lake is a seasonal anoxic water system in the southwest of Guiyang City, Guizhou Province, China. Seasonal variations in SO42- concentrations and their isotopic compositions in lake water as well as in the tributaries were investigated in this study. The results showed that sulfate concentrations in river water range from 0.94 to 6.52 mmol/L and their δ34S values range from -14.9‰ and 0.9‰, while lake water has sulfate concentrations ranging from 1.91 to 2.79 mmol/L, and δ34S values from -9.8‰ to -5.9‰. It is suggested that coal mining drainage is the major source of SO42- in the Aha Lake. Rainfall, sewage discharge, sulfide oxidation and gypsum dissolution have made only limited contributions. Different depth-dependent distributions of dissolved SO42- and δ34S were de-veloped for both DB and LJK in summer and winter. Due to water overturn, δ34S values display homogenous vertical distributions in winter and spring. While in summer and autumn, significant positive shifts of δ34S were clearly ob-served in epilimnion and bottom strata as a result of water stratification. High δ34S values in epilimnion may result from the retention of rainwater during water stratification. Dissimilatory sulfate reduction by bacteria was thought to be responsible for the increase of δ34S value in hypolimnion.

Iron Isotope Compositions of Natural River and Lake Samples in the Karst Area,Guizhou Province,Southwest China

To better understand the Fe isotope characteristics of natural samples in the Karst area,the Fe isotope compositions of riverine suspended particulates,lake suspended particulates,lake sediments,porewaters,phytoplanktons,and aerosols in the watersheds of Lake Aha（a mineralized water system）and Lake Hongfeng（a mesotrophic water system）,which are located in the Karst area, southwest China,were investigated.The studied samples displayed a variable range betweenδ^（56）Fe=-2.03‰and 0.36‰.Aerosols and phytoplanktons have similar or slightly heavier Fe isotope compositions relative to the average of igneous rocks.Fe isotope compositions of riverine Suspended Particulate Matter（SPM）were mainly affected by the types of tributaries.Suspended particulates collected from tributaries seriously contaminated with coal mine drainages displayed negativeδ^（56）Fe values（-0.89‰to-0.31‰）during summer,and there were significant increases ofδ^（56）Fe values in winter,except AR2,which was polluted with both coal mine drainage and sewage effluent. Characteristics of lakes have important influences on Fe isotope compositions of suspended particulates,lake sediments,and porewaters.The epilimnetic particulate Fe of Lake Hongfeng hadδ^（56）Fe=-0.04‰to 0.13‰,while lighter Fe isotope compositions were measured for particulate Fe from Lake Aha,ranging from-0.42‰to-0.09‰.Sediments collected from Hou Wu（HW）station of Lake Hongfeng have an averageδ^（56）Fe value of 0.09‰and their corresponding porewaters have lighter Fe isotope compositions,ranging from-0.57‰to-0.31‰;no significant variations have been observed. For the Liang Jiang Kou（LJK）station of Lake Aha,the content of reactive Fe and the concentration of sulfate were all high.Due to the reactive Fe recycling,including dissimilatory Fe reduction,adsorption, and Fe-sulfide formation,porewaters sampled near the sediment surface have been found to have aδ^（56）Fe value as low as-2.03‰and an increase up to 0.12‰,with a burial depth of 10 cm.In contrast,an opposite variation trend was found for LJK sediments.Sediments sampled at 1-cm depth had a value ofδ^（56）Fe=-0.59‰and decrease as low as-1.75‰with burial depth.This investigation demonstrated that significant Fe isotope fractionations occur in surface environments.Fe isotope compositions of particulate Fe were seriously affected by Fe sources,and Fe biogeochemical recycling has an important influence on Fe isotope fractionations in lake sediments,especially when there are significant amounts of reactive Fe and sulfate.

Anaerobic benzene biodegradation by a pure bacterial culture of Bacillus cereus under nitrate reducing conditions

A pure culture using benzene as sole carbon and energy sources was isolated by screening procedure from gasoline contaminated soil.The analysis of the 16S rDNA gene sequence,morphological and physiological characteristics showed that the isolated strain was a member of genus Bacillus cereus.The biodegradation performance of benzene by B.cereus was evaluated,and the results showed that benzene could be efficiently biodegraded when the initial benzene concentration was below 150 mg/L.The metabolites of anaerobic nitrate-dependent benzene oxidation by strain B.cereus were identified as phenol and benzoate.The results of substrate interaction between binary combinations for benzene,phenol and benzoate showed that the simultaneous presence of benzene stimulated the degradation of benzoate,whereas the addition of benzene inhibited the degradation of phenol.Benzene degradation by B.cereus was enhanced by the addition of phenol and benzoate,the enhanced effects were more pronounced at higher concentration.To our knowledge,this is the first report that the isolated bacterial culture of B.cereus can efficiently degraded benzene under nitrate reducing conditions.

Analysis of Environmental Endocrine Disrupting Activities in Wastewater Treatment Plant Effluents Using Recombinant Yeast Assays Incorporated with Exogenous Metabolic Activation System

Objective To measure the endocrine disrupting chemicals （EDCs） in wastewater and evaluate the EDCs removal efficiencies in the municipal wastewater treatment plants （WWTP）. Methods A battery of in vitro recombinant yeast bioassays incorporated with exogenous metabolic activation system （rat liver preparation, S9 mix） was conducted to assess the estrogen receptor （ER）, androgen receptor （AR）, progesterone receptor （PR）, and thyroid receptor （TR） ant/agonistic activities of effluents collected from Datansha WWTP. Results The indirect estrogenic, anti‐androgenic, anti‐progesteronic, and anti‐thyroidic activities were observed in the influent. The removal efficiencies of EDCs were above 74%, suggesting that the present wastewater treatment processes were good enough to remove most of these indirect endocrine disrupting chemicals. Conclusion The incorporation of exogenous metabolic capacity into the test system was valid for the study of indirect effects on ER, AR, PR, and TR.

Biogeography and diversity patterns of antibiotic resistome in the sediments of global lakes

Lakes act as one of the reservoirs and dispersal routes of antibiotic resistance genes(ARGs)and pathogenic resistant bacteria in aquatic environments.Previous studies reported the occurrence and distribution of ARGs in lakes worldwide;however,few investigated the biogeography and diversity patterns of antibiotic resistome in the environment.To fill this gap,a large-scale data set of sediment metagenomes was collected from globally distributed lakes and characterized comprehensively using metagenomic assembly-based analysis,aiming to shed light on the biogeography and diversity patterns of ARGs in lake ecosystems from a global perspective.Our analyses showed that abundant and diverse ARGs were found in the global lake sediments,including a set of emerging ARGs such as mcr-type and carbapenem-resistant Enterobacteriaceae related genes.Most of the identified ARGs were generally associated with the commonly used antibiotics,suggesting the role of increasing antibiotic consumptions on the resistome prevalence.Spatially,the composition and diversity of ARGs varied across geographical distances and exhibited a scale-dependent distancedecay relationship.Notably,the composition of ARGs was largely shaped by bacterial community structure,and their diversities were co-governed by stochastic process(∼48%)and deterministic process(∼52%).Findings provide a valuable insight to better understand ecological mechanisms of ARGs in lake ecosystems and have important implication for the prevention and control of resistome risk.

Impact of Urbanization and Industrialization upon Surface Water Quality:A Pilot Study of Panzhihua Mining Town

In order to investigate the impact of urbanization and industrialization on surface water quality, a pilot study of Panzhihua （攀枝花） mining town was carried out. The urbanization of Panzhihua region was dominated by industry development and population growth. The level of urbanization showed that it was 18.44% in 1965, and reached 45.99% in 1983. Then, it reached 53.71% in 2005, so the urbanization process was very rapid in Panzhihua region. In the process of industrialization, the level of industrialization was fluctuated at around 70% from 1965 to 2005, which was influenced by mining, extracting, and smelting production. In the processes of urbanization, population growth caused an increase in life pollution sources, and an amount of effluents bearing coliform, COD （chemical oxygen demand）, NH4^＋-N, and BOD5 （five-day biological oxygen demand） were released into Jinsha （金沙） River, which could cause decline in the surface water quality. While in the processes of industrialization （especially industrial scale expansion）, more effluent bearing heavy metals could cause degra- dation of surface water quality. Thus, the measures, such as adjusting industry structure, optimizing the cleaning technology, and controlling pollution sources, should be enhanced to alleviate the current state of water quality exacerbation.

Application of percarbonate and peroxymonocarbonate in decontamination technologies

Sodium percarbonate(SPC)and peroxymonocarbonate(PMC)have been widely used in modified Fenton reactions because of their multiple superior features,such as a wide pH range and environmental friendliness.This broad review is intended to provide the fundamental information,status and progress of SPC and PMC based decontamination technologies according to the peer-reviewed papers in the last two decades.Both SPC and PMC can directly decompose various pollutants.The degradation efficiency will be enhanced and the target contaminants will be expanded after the activation of SPC and PMC.The most commonly used catalysts for SPC activation are iron compounds while cobalt composi-tions are applied to activate PMC in homogenous and heterogeneous catalytical systems.The generation and participation of hydroxyl,superoxide and/or carbonate radicals are involved in the activated SPC and PMC system.The reductive radicals,such as carbon dioxide and hydroxyethyl radicals,can be generated when formic acid or methanol is added in the Fe(II)/SPC system,which can reduce target contaminants.SPC can also be activated by energy,tetraacetylethylenediamine,ozone and buffered alkaline to generate different reactive radicals for pollutant decomposition.The SPC and activated SPC have been assessed for application in-situ chemical oxidation and sludge dewatering treatment.The challenges and prospects of SPC and PMC based decontamination technologies are also addressed in the last section.

The elevation gradient of stable isotopes in precipitation in the eastern margin of Tibetan Plateau

Tibetan Plateau(TP)receives moistures from different directions,so variations of isotope elevation gradient on different sides may exist.In this study,we systematically monitored and modeled the elevation effect of stable isotopes in precipitation of the eastern margin of the Tibetan Plateau,where we collected 265 water samples for stable isotope(δ2H andδ^(18)O)analyses,of which 70 are eventful rainfall samples,and 195 are surface water samples,for comparison.Alpine lakes on the mountain peaks were used to reconstruct the average isotope composition of the local precipitation based on the evaporation effect.An elevation gradient of−4.2‰km^(−1)(R^(2)=0.93)was established for the eastern marginal region of TP.This elevation gradient was further confirmed by fractionation assessment using the Rayleigh fractionation model.This is the highest ever reported for the TP and it is the highest as compared to those of all the other slopes as well as that of the interior part of the TP.Precipitation isotopes in the interior of TP show a lower elevation gradient,which is likely caused by significant local moisture recycling.This paper also discusses the limitations of using river water samples to construct the elevation gradient.