[Ecologically suitable areas for growing Scutellaria baicalensis worldwide: an analysis based on GMPGIS].

This paper explored the ecologically suitable areas for growing Scutellaria baicalensis using Geographic Information System for Global Medicinal Plants(GMPGIS), to figure out the resource distribution of S. baicalensis worldwide and provide a scientific basis for its scientific introduction. A total of 349 S. baicalensis sampling sites were selected all over the world for GMPGIS-based analy-sis of the ecologically suitable areas with six ecological factors including annual average temperature, average temperature during the coldest season, average temperature during the warmest season, average annual precipitation, average annual relative humidity, and annual average illumination and soil type as the ecological indexes. The results demonstrated that the ecologically suitable areas for growing S. baicalensis were mostly located in the Northern hemisphere, and the suitable areas in the United States, China, and Russia accounted for 19.25%, 18.66%, and 13.15% of the total area worldwide, respectively. In China, the Inner Mongolia, Heilongjiang province, and Yunnan province occupied the largest proportions of the total area, namely 14.28%, 8.72%, and 6.18%, respectively. As revealed by ecological factors of each sampling site, S. baicalensis was resistant to low temperature but not to high temperature. The adaptive range of average annual precipitation is narrower than that of average annual air humidity. The suitable soils were mainly inceptisol, alfisol, and fluvisol. High temperature and rainy climate or excessively high soil bulk density was not conducive to the growth of S. baicalensis. The adoption of GMPGIS enabled to obtain areas with the greatest ecological similarity for S. baicalensis, which were reliable data supporting the exploration of resource distribution and reasonable introduction of S. baicalensis.

[Study of extracting natural resources of Chinese medicinal materials planted area in Luoning of Henan province based on UAV of low altitude remote sensing technology and remote sensing image of satellite].

The study is aimed to effectively obtain the planting area of traditional Chinese medicine resources. The herbs used as the material for traditional Chinese medicine are mostly planted in natural environment suitable mountainous areas. The UAV low altitude remote sensing data were used as the samples and the GF-2 remote sensing images were applied for the data source to extract the planting area of Salvia miltiorrhiza and Artemisia argyi in Luoning county combined with field investigation. Remote sensing satellite data of standard processing obtain specific remote sensing data coverage. The UAV data were pre-processed to visually interpret the species and distribution of traditional Chinese medicine resources in the sample quadrat. Support vector machine( SVM) was used to classify and estimate the area of traditional Chinese medicine resources in Luoning county,confusion matrix was used to determine the accuracy of spatial distribution of traditional Chinese medicine resources. The result showed that the application of UAV of low altitude remote sensing technology and remote sensing image of satellite in the extraction of S. miltiorrhiza and other varieties planting area was feasible,it also provides a scientific reference for poverty alleviation policies of the traditional Chinese medicine Industry in local areas.Meanwhile,research on remote sensing classification of Chinese medicinal materials based on multi-source and multi-phase high-resolution remote sensing images is actively carried out to explore more effective methods for information extraction of Chinese medicinal materials.

Ethanol extract of Rehmannia glutinosa exerts antidepressant-like effects on a rat chronic unpredictable mild stress model by involving monoamines and BDNF.

The dried roots of Rehmannia glutinosa Libosch. (Scrophulariaceae) are of both medicinal and nutritional importance. Our previous study has found that the 80% ethanol extract of R. glutinosa (RGEE) produced antidepressant-like activities in mouse behavioral despair depression models. However, its mechanisms are still unclear. The present study aimed to observe the antidepressant-like mechanisms of RGEE on a rat chronic unpredictable mild stress (CUMS) model by involving monoaminergic neurotransmitters and brain-derived neurotrophic factor (BDNF). CUMS-stressed rats were orally given RGEE daily (150, 300, and 600 mg/kg) or fluoxetine hydrochloride (FH) for 3 weeks after starting the CUMS procedure. Sucrose preference test was carried out to observe depression-like behavior, and serum and brain tissues were used for neurochemical and fluorescent quantitative reverse transcription PCR analysis. Results demonstrated that CUMS induced depression-like behavior, whereas RGEE and FH administration inhibited this symptom. Furthermore, CUMS caused excessively elevated levels of serum corticosterone (CORT), an index of hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, in a manner attenuated by RGEE and FH administration. RGEE administration also further elevated monoamine neurotransmitters and BDNF levels, up-regulated the mRNA expression of BDNF and tropomyosin-related kinase B (TrkB) in hippocampus of rats suffering CUMS. Together, our findings suggest that RGEE can improve CUMS-evoked depression-like behavior, and indicate its mechanisms may partially be associated with restoring HPA axis dysfunctions, enhancing monoamineergic nervous systems, and up-regulating BDNF and TrkB expression.

Preparative Isolation of Two Prenylated Biflavonoids from the Roots and Rhizomes of Sinopodophyllum emodi by Sephadex LH-20 Column and High-Speed Counter-Current Chromatography.

Two prenylated biflavonoids, podoverines B-C, were isolated from the dried roots and rhizomes of Sinopodophyllum emodi using a Sephadex LH-20 column (SLHC) and high-speed counter-current chromatography (HSCCC). The 95% ethanol extract was partitioned with ethyl acetate in water. Target compounds from the ethyl acetate fraction were further enriched and purified by the combined application of SLHC and HSCCC. n-Hexane-ethyl acetate-methanol-water (3.5:5:3.5:5, v/v) was chosen as the two phase solvent system. The flow rate of mobile phase was optimized at 2.0 mL·min(-1). Finally, under optimized conditions, 13.8 mg of podoverine B and 16.2 mg of podoverine C were obtained from 200 mg of the enriched sample. The purities of podoverines B and C were 98.62% and 99.05%, respectively, as determined by HPLC. For the first time, podoverins B and C were found in the genus Sinopodophyllum. Their structures were determined by spectroscopic methods (HR-ESI-MS, ¹H-NMR, (13)C-NMR, HSQC, HMBC). Their absolute configurations were elucidated by comparison of their experimental and calculated ECD spectra. The cytotoxic activities were evaluated against MCF-7 and HepG2 cell lines. The separation procedures proved to be practical and economical, especially for trace prenylated biflavonoids from traditional Chinese medicine.

[Microbial diversity of salt lakes in Badain Jaran desert].

OBJECTIVE: We characterized procaryotic biodiversity, community structure and the relationship between the community structure and environmental factors of salt lakes in Badain Jaran desert, Inner Mongolia, China. METHODS: We constructed 16S rRNA gene clone libraries by molecular biology techniques to analyze the procaryotic phylogenetic relationships, and used R language to compare the community structure of haloalkalophiles in the salt lakes. RESULTS: Water in this region has a high salinity ranging from 165 to 397 g/L. The water is strongly alkaline with pH value above 10. The microbial diversity and community structure of the salt lakes are obviously different. The diversity of bacteria is more abundant than that of archaea. The main categories of bacteria in the samples are Gammaproteobacteria, Bacteroidetes, Alphaproteobacteria, Firmicute and Verrucomicrobia, whereas all archaea only belong to Halobacteriaceae of Euryarchaeota. CONCLUSION: Salinity is the most important environmental factor influencing the bacterial community structure, whereas the archaea community structure was influenced comprehensively by multiple environmental factors.

[Research on Breeding of Dioscorea opposita cv. Tiegun].

OBJECTIVE: To breeding the new varieties Dioscorea opposita cv. Tiegun with the best comprehensive properties. METHODS: Seven new Dioscorea opposita. cv. Tiegun cultivars were screened by space mutation breeding of Dioscorea opposita cv. Tiegun bulbils. Yield,allantoin content,water soluble extractive and the resistance of these seven cultivars were compared with the main cultivar Dioscorea opposita cv. Tiegun( CK). Meanwhile, the nutrition quality of new cultivars No. 6 and No. 10 were compared with the main cultivar. RESULTS: (1) The fresh weight per plant ranked in the order as follows: No. 6 > No. 10 > No. 4 > No. 9 > No. 1 > CK > No. 2 > No. 8. The drying rate ranked in the order as follows: No. 2 > No. 10 > No. 9 > No. 6 > No. 8 > CK > No. 1 > No. 4. Dry weight per plant ranked in the order as follows: No. 10 > No. 9 > No. 6 > No. 2 > No. 1 > CK > No. 4 > No. 8. The fresh weight per plant, drying rate and dry weight per plant of No. 6 and No. 10 were higher than the main cultivar. (2) The allantoin content ranked in the order as follows: No. 6 > No. 4 > No. 10 > CK > No. 9 > No. 8 > No. 2 > No. 1. (3) The water soluble extractive contents ranked in the order as follows: No. 6 > No. 2 > No. 4 > No. 10 > No. 1 > CK > No. 9 > No. 8. The water soluble extractive content of No. 6 was higher than No. 10 and the main cultivar. (4) No. 10 had the best taste of dry, soft, sweet and fragrant, No. 6 had the taste of dry, floury and hard, and No. 9 had the taste of dry and crisp. (5) No. 6 had the strongest resistance to Gloeosporium pestis and Cykindrosporium dioscoreae; No. 10 had a middle resistance to Gloeosporium pestis and a strong resistance to Cykindrosporium dioscoreae; and the main cultivar had a middle degree of being prone to Gloeosporium pestis and a middle resistance to Cykindrosporium dioscoreae. (6) The content of starch, reducing sugar, protein and ash in No. 6 and No. 10 were higher than that of the main cultivar,while the content of water in No. 6 and No. 10 were lower,which indicated that the nutrition quality of No. 6 and No. 10 is better than the main cultivar. CONCLUSION: The new cultivar No. 10 is suitable for popularizing as a new variety of edible Dioscorea opposita cv. Tiegun. The new cultivar No. 6 is suitable for popularizing as a new variety of medicinal Dioscorea opposita cv. Tiegun.

Differential effects of warming on the complexity and stability of the microbial network in Phragmites australis and Spartina alterniflora wetlands in Yancheng, Jiangsu Province, China.

The impact of climate warming on soil microbial communities can significantly influence the global carbon cycle. Coastal wetlands, in particular, are susceptible to changes in soil microbial community structure due to climate warming and the presence of invasive plant species. However, there is limited knowledge about how native and invasive plant wetland soil microbes differ in their response to warming. In this study, we investigated the temporal dynamics of soil microbes (prokaryotes and fungi) under experimental warming in two coastal wetlands dominated by native Phragmites australis (P. australis) and invasive Spartina alterniflora (S. alterniflora). Our research indicated that short-term warming had minimal effects on microbial abundance, diversity, and composition. However, it did accelerate the succession of soil microbial communities, with potentially greater impacts on fungi than prokaryotes. Furthermore, in the S. alterniflora wetland, experimental warming notably increased the complexity and connectivity of the microbial networks. While in the P. australis wetland, it decreased these factors. Analysis of robustness showed that experimental warming stabilized the co-occurrence network of the microbial community in the P. australis wetland, but destabilized it in the S. alterniflora wetland. Additionally, the functional prediction analysis using the Faprotax and FunGuild databases revealed that the S. alterniflora wetland had a higher proportion of saprotrophic fungi and prokaryotic OTUs involved in carbon degradation (p < 0.05). With warming treatments, there was an increasing trend in the proportion of prokaryotic OTUs involved in carbon degradation, particularly in the S. alterniflora wetland. Therefore, it is crucial to protect native P. australis wetlands from S. alterniflora invasion to mitigate carbon emissions and preserve the health of coastal wetland ecosystems under future climate warming in China.

Biological characteristics of flowers and examination of pollen viability at different developmental stages of Epimedium sagittatum (Sieb. et Zucc.) Maxim.

To gain a deeper understanding of the flowering pattern and reproductive characteristics of Epimedium sagittatum, to enrich the research on the flower development of E. sagittatum and its reproductive regulation, and to screen the methods suitable for the rapid detection of pollen viability of E. sagittatum and to promote its cross-breeding. The characteristics of its flower parts were observed, recorded and measured, and the pollen viability of E. sagittatumwas determined by five methods, including TTC staining, I2-KI staining, red ink staining, peroxidase method and in vitro germination method. The flowering process of E. sagittatum can be divided into five stages: calyx dehiscence, bract spathe, petal outgrowth, pollen dispersal, and pollination and withering. The results of I2-KI staining and peroxidase method were significantly higher than those of other methods; the in vitro germination method was intuitive and accurate, but the operation was complicated and time-consuming; the red ink staining method was easy to operate and had obvious staining effect, and the results were the closest to those of the in vitro germination method; and it was found that the pollen of E. sagittatum was not as effective as the in vitro germination method at the bud stamen stage, the flower stigma and the flower bud. It was also found that the pollen viability and germination rate of E. sagittatum pollen were higher in the three periods of bud spitting, petal adductor and pollen dispersal. Comparing the five methods, the red ink staining method was found to be a better method for the rapid detection of pollen viability; the best pollination periods of E. sagittatum were the bud stamen stage, petal adductor stage, and pollen dispersal stage of flowers at the peak of bloom. This study on the flowering and fruiting pattern of E. sagittatum, and the related mechanism of sexual reproduction, can be used as a reference for the next step of research on the breeding of E. sagittatum.

Responses of photosynthetic characteristics of Phragmites australis to simulated warming in salt marshes of the Yellow Sea and Bohai Sea, China.

Coastal wetlands are highly efficient in blue carbon sequestration. The impacts of climate warming on photosynthetic rates and light response characteristics of wetland plants would change the magnitude of carbon sequestration in coastal wetlands. We constructed warming observation stations in Phragmites australis (Phragmites) wetlands located in the Yellow River Delta in Dongying with dry climate, and in Yancheng by the Yellow Sea with wet climate. By using a Li-6800 photosynthesis system, we investigated the responses of simulated warming on photosynthetic characteristics of Phragmites in both wetlands, and compared the difference between months (June and August) in Dongying wetland. The results showed the photosynthetic rates of Phragmites were higher in June than in August. Warming increased net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (gs) and intercellular carbon dioxide concentration (Ci) in the two months, but the variability of Pn to warming was lower in August. The Pn and water use efficiency (WUE) of Phragmites in the Yancheng wetland were higher than Dongying wetland, and the maximum net photosynthetic rate (Pn max), light saturation point (LSP), apparent quantum efficiency (AQY), and dark respiration rate (Rd) of the former responded more positively to warming. The values of AQY, LSP and Pn max of Phragmites in the Yancheng wetlands were increased by 16.7%, 53.6% and 30.3%, respectively, in the warming plots. Our results suggested that warming could improve the utilization efficiency of weak light, the adaptability to strong light and photosynthetic potential of Phragmites under rainy and humid conditions. This study is of importance for accurately quantifying carbon sequestration of coastal wetlands at the regional and seasonal scales in the context of climate warming.

Ecological risk assessment of heavy metals in the sediments and their impacts on bacterial community structure: A case study of Bamen Bay in China.

Heavy metal pollution associated with human activity is of big concern in tropical bays. Microorganisms may be highly sensitive to heavy metals. Nonetheless, little is known about effects of heavy metals on microbial structure in tropical bay sediments. In this study, 16S rRNA gene sequencing and potential ecological risk index analysis were used to analyze the relationships between nine metals (arsenic, lead, cadmium, cobalt, chromium, copper, zinc, manganese, and nickel) and bacterial communities in the sediments of Bamen Bay, China. Our results showed that Bamen Bay was under a considerable ecological risk and cadmium had the highest monomial potential ecological risk. In addition, individual metal contamination correlated with bacterial community composition but not with bacterial α-diversity. Arsenic was the metal influencing bacterial community structure the most. Our findings provide a novel insight into the monitoring and remediation of heavy metal pollution in tropical bays.

Synergistic/antagonistic effects of nitrate/ammonium enrichment on fatty acid biosynthesis and translocation in coral under heat stress.

Superimposed on ocean warming, nitrogen enrichment caused by human activity puts corals under even greater pressure. Biosynthesis of fatty acids (FA) is crucial for coral holobiont survival. However, the responses of FA biosynthesis pathways to nitrogen enrichment under heat stress in coral hosts and Symbiodiniaceae remain unknown, as do FA translocation mechanisms in corals. Herein, we used the thermosensitive coral species Acropora hyacinthus to investigate changes in FA biosynthesis pathways and polyunsaturated FA translocation of coral hosts and Symbiodiniaceae with respect to nitrate and ammonium enrichment under heat stress. Heat stress promoted pro-inflammatory FA biosynthesis in coral hosts and inhibited FA biosynthesis in Symbiodiniaceae. Nitrate enrichment inhibited anti-inflammatory FA biosynthesis in Symbiodiniaceae, and promoted pro-inflammatory FA biosynthesis in coral hosts and translocation to Symbiodiniaceae, leading to bleaching after 14 days of culture. Intriguingly, ammonium enrichment promoted anti-inflammatory FA biosynthesis in Symbiodiniaceae and translocation to hosts, allowing corals to better endure heat stress. We constructed schematic diagrams of the shift in FA biosynthesis and translocation in and between A. hyacinthus and its Symbiodiniaceae under heat stress, heat and nitrate co-stress, and heat and ammonium co-stress. The findings provide insight into the mechanisms of coral bleaching under environmental stress from a fatty acid perspective.

Modeling nutrient flows from land to rivers and seas - A review and synthesis.

Water quality modeling facilitates management of nutrient flows from land to rivers and seas, in addition to environmental pollution management in watersheds. In the present paper, we review advances made in the development of seven water quality models and highlight their respective strengths and weaknesses. Afterward, we propose their future development directions, with distinct characteristics for different scenarios. We also discuss the practical problems that such models address in the same region, China, and summarize their different characteristics based on their performance. We focus on the temporal and geographical scales of the models, sources of pollution considered, and the main problems that can be addressed. Summary of such characteristics could facilitate the selection of appropriate models for resolving practical challenges on nutrient pollution in the corresponding scenarios globally by stakeholders. We also make recommendations for model enhancement to expand their capabilities.

Complete sequence of Cynanchum rostellatum (Apocynaceae: Asclepiadoideae) chloroplast genome and its phylogenetic analysis.

Cynanchum rostellatum (Turcz.) Liede and Khanum 2016 is a perennial herbaceous twining vine that is widely distributed in Japan, South Korea, the United States of America, and China. In this study, the complete chloroplast (cp) genome of C. rostellatum was sequenced using the Illumina platform and assembled for the first time. This plastome has a circular structure with a length of 160,641 bp. The GC content of the plastome was 37.82%. The cp genome contained 113 unique genes, including 79 protein-coding, 30 transfer RNA, and four ribosomal RNA genes. Phylogenetic analysis based on the complete cp genome sequences of the Asclepiadoideae subfamily showed that C. rostellatum was closely related to C. bungei in the genus Cynanchum. These results provide useful information for both phylogenetic research and the utilization of C. rostellatum.

The complete chloroplast genome and phylogenetic analysis of Smilax moranensis (Liliales: Smilacaceae).

Smilax moranensis M.Martens & Galeotti 1842 is an important medicinal plant widely distributed in warm and temperate climates. In this paper, the complete chloroplast (cp) genome of S. moranensis was sequenced using the Illumina platform and assembled for the first time. This plastome is a circular structure of 157,907 bp in length. The GC content of the plastome was 37.16%. A total of 112 unique genes in this genome have been annotated, including 78 protein-coding genes, 30 transfer RNA genes, and four ribosomal RNA genes. Phylogenetic analysis based on complete cp genome sequences of Smilacaceae family showed that Smilax is monophyletic. The position of S. moranensis was positioned as the sister to the other seven Smilax species. These results provide an important basis for future species identification and taxonomic determinations, as well as the phylogenetic reconstruction of the family Smilacaceae.

Natural background levels in groundwater in the Pearl River Delta after the rapid expansion of urbanization: A new pre-selection method.

Establishment of natural background levels (NBL) of groundwater in urbanized areas such as the Pearl River Delta (PRD) is challenging. Pre-selection methods are the most common approaches for NBL assessment, but it will overestimate (or underestimate) contaminated groundwater in urbanized areas by using present pre-selection methods with empirical definite values because of complicated human activities. Unlike present pre-selection methods, this study aims to establish a new pre-selection method with the indicative of Cl/Br ratios to identify contaminated groundwaters with convincing evidences. Specifically, this new method consists of indicatives of the oxidation capacity and the Cl/Br ratio combining with contaminated-markers. In addition, factors controlling NBL of Cl and NO3 in groundwater in various hydrogeological units in the PRD were also discussed. Main procedures of this new method: contaminated-markers in various hydrogeological units are extracted by a hierarchical cluster analysis, thereby determining threshold values of Cl/Br ratios and Cl concentration in various hydrogeological units for identifying contaminated groundwater; After that, groundwater chemical datasets was selected by the oxidation capacity, and then tested by Grubbs' test until normal distributions. Groundwater Cl and NO3 concentrations in datasets before and after this new method are dependent and independent of urbanization levels, respectively, indicating that the new method is useful for groundwater NBL assessment in urbanized areas such as the PRD. Both the seawater intrusion and the diffusion of Cl from marine deposits are likely to be responsible for the much higher NBL-Cl in coastal-alluvial and marine aquifers than in other hydrogeological units. Groundwater Cl enrichment resulted from groundwater recharge and evaporation is mainly responsible for the higher NBL-Cl in alluvial-proluvial aquifers than in lacustrine aquifers, fissured aquifers, as well as karst aquifers. More than double times NBL-NO3 in alluvial-proluvial and fissured aquifers than in other hydrogeological units is probably attributed to more oxidizing conditions of their vadose zones and groundwaters.

A sharp contrasting occurrence of iron-rich groundwater in the Pearl River Delta during the past dozen years (2006-2018): The genesis and mitigation effect.

Fe-rich (>0.3 mg/L) groundwater is generally present in areas where organic matter-rich fluvial, lacustrine, or marine sedimentary environments occur. The Pearl River Delta (PRD) that marine sediments is common, where a large scale of Fe-rich groundwater was distributed but disappearing in recent decade. This study aims to investigate the change of Fe-rich groundwater in the PRD, and to discuss the genesis controlling Fe-rich groundwater in the PRD during the past dozen years. A total of 399 and 155 groundwater samples were collected and analyzed at 2006 and 2018, respectively. Results showed that Fe-rich groundwater of the PRD was from 19.3% at 2006 dropped to 1.3% at 2018. Fe-rich groundwater in coastal-alluvial aquifers was more than 2 times that in other aquifers at 2006. Both of anthropogenic and geogenic sources were contributed to the widely distribution of Fe-rich groundwater in the PRD at 2006. The infiltration of industrial wastewater and the irrigation of Fe-rich surface water were the major anthropogenic driving forces for the occurrence of Fe-rich groundwater in the PRD at 2006. The reductive dissolution of Fe minerals in aquifer sediments, associated with the degradation of organic matter in marine sediments and the sewage infiltration, was the main driving force for the enrichment of groundwater Fe in coastal-alluvial aquifers at 2006. The intrusion of sewage triggering the reductive dissolution of Fe minerals in terrestrial sediments and the reductive dissolution of Fe minerals in carbon-rich rocks induced by sewage leakages were the major driving forces for the occurrence of Fe-rich groundwater in alluvial-proluvial and fissured aquifers at 2006. All these driving forces were weaker or even not work at 2018 because of the large decrease of untreated wastewater discharge in the PRD during 2006-2018. Therefore, limiting untreated wastewater discharge is the first choice to improve the groundwater quality in urbanized areas.

The Aging Process of Cadmium in Paddy Soils under Intermittent Irrigation with Acid Water: A Short-Term Simulation Experiment.

Cadmium (Cd)-contaminated paddy soils are a big concern. However, the effect of irrigation with acid water on the migration and transformation of Cd and the effect of alternating redox conditions caused by intermittent irrigation on Cd aging processes in different depths of paddy soils are unclear. This study revealed Cd fractionation and aging in a Cd-contaminated paddy soil under four irrigation periods with acid water and four drainage periods, by applying a soil columns experiment and a sequential extraction procedure. The results showed that the dynamic changes of soil pH, oxidation reduction potential (ORP), iron (Fe) oxides and dissolved organic carbon (DOC) throughout the intermittent irrigation affected the transformation of Cd fractions. After 32 days, the proportion of exchangeable Cd (F1) to the total Cd decreased with a reduction of 24.4% and 20.1% at the topsoil and the subsoil, respectively. The labile fractions of Cd decreased, and the more immobilizable fractions of Cd increased in the different depths of soils due to the aging process. Additionally, the redistribution of the Fe and Mn oxide-bound Cd (F3) and organic matter and secondary-sulfide-bound Cd (F4) occurred at different depths of soils during the incubation time. Overall, the bioaccessibility of Cd in the subsoil was higher than that in the topsoil, which was likely due to the leaching and accumulation of soluble Cd in the deep soil. In addition, the aging processes in different depths of soils were divided into three stages, which can be mainly described as the transformation of F1 into F3 and F4.

Distributions, origins, and health-risk assessment of nitrate in groundwater in typical alluvial-pluvial fans, North China Plain.

High concentration of nitrate (NO3-) in groundwater is a major concern because of its complex origin and harmful effects on human health. This study aims to investigate the distributions of nitrate in various aquifers and in areas with different land use types in alluvial-pluvial fans in North China Plain, to identify dominant sources and factors using hydrochemical data and principal component analysis, and to conduct health-risk assessment of groundwater nitrate using the models recommended by USEPA. Results show that approximately 76.1% groundwater in fissured aquifers showed high-NO3- (> 50 mg/L), and was 2.7 times of that in granular aquifers. In fissured aquifers, the proportion of high-NO3- groundwater (PHNG-WHO) in peri-urban areas was more than 1.3 times of those in other areas. Similarly, in shallow granular aquifers, the PHNG-WHO in peri-urban areas was also higher than that in other areas. By contrast, in deep granular aquifers, the PHNG-WHO in urbanized areas was 2.8 and 5.2 times of that in peri-urban areas and farmland, respectively. High NO3- levels in both granular and fissured aquifers originated mainly from domestic sewage and animal waste, and fertilizers are also important sources of NO3- in fissured aquifers. Intensive groundwater exploitation aggravated nitrate contamination because more thickness of vadose zones resulting from over-exploitation is in favor of nitrification. Risk assessment of groundwater nitrate indicated about 43.3%, 45.6%, and 54.2% of the groundwater samples showed unacceptable non-carcinogenic risk to adult males, adult females, and children, respectively. The proportion of samples with health risks had a significant positive correlation with the urbanization level. Our study indicates that several effective measures for pollution prevention, such as strengthening sewage treatment and prohibiting groundwater over-exploitation, must be adopted so as to ensure the sustainable management of groundwater and the safety of drinking water.

Identification of Groundwater Contamination in a Rapidly Urbanized Area on a Regional Scale: A New Approach of Multi-Hydrochemical Evidences.

Efficient identification of groundwater contamination is a major issue in the context of groundwater use and protection. This study used a new approach of multi-hydrochemical indicators, including the Cl-Br mass ratio, the hydrochemical facies, and the concentrations of nitrate, phosphate, organic contaminants, and Pb in groundwater to identify groundwater contamination in the Pearl River Delta (PRD) where there is large scale urbanization. In addition, the main factors resulting in groundwater contamination in the PRD were also discussed by using socioeconomic data and principal component analysis. Approximately 60% of groundwater sites in the PRD were identified to be contaminated according to the above six indicators. Contaminated groundwaters commonly occur in porous and fissured aquifers but rarely in karst aquifers. Groundwater contamination in porous aquifers is positively correlated with the urbanization level. Similarly, in fissured aquifers, the proportions of contaminated groundwater in urbanized and peri-urban areas were approximately two times that in non-urbanized areas. Groundwater contamination in the PRD was mainly attributed to the infiltration of wastewater from township-village enterprises on a regional scale. In addition, livestock waste was also an important source of groundwater contamination in the PRD. Therefore, in the future, the supervision of the wastewater discharge of township-village enterprises and the waste discharge of livestock should be strengthened to protect against groundwater contamination in the PRD.

Both pH and salinity shape the microbial communities of the lakes in Badain Jaran Desert, NW China.

Badain Jaran Desert (BJD), characterized by extremely arid climate and tallest sand dunes in the world, is the second largest desert in China. Surprisingly, there are a large number of permanent lakes in this desert. At present, little is known about the composition and distribution of microbial communities in these desert lakes, which are an important bioresource and play a fundamental role in the elemental cycles of the lakes. In this study, the physicochemical characteristics and microbial communities of water samples from 15 lakes in BJD were comparatively investigated. The results showed that the lakes were rich in Na+, Cl-, CO32- and HCO3- while Ca2+ and Mg2+ were scarce, with pH 8.52-10.27 and salinity 1.05-478.70 g/L. Bacteria dominated exclusively in low saline lakes (salinity < 50 g/L) while archaea were predominant in hypersaline lakes (salinity > 250 g/L), which abundance increased along salinity gradient linearly. Genera Flavobacterium, Synechocystis and Roseobacter from phyla Bacteroidetes, Cyanobacteria, Alphaproteobacteria were the major members in low saline lakes whereas Halomonas, Aliidiomarina and Halopelagius from Gammaproteobacteria and Euryarchaeota were abundant in moderately saline lakes (salinity 50-250 g/L). The hypersaline lakes were predominated by extreme halophiles such as Halorubrum, Halohasta and Natronomonas from Euryarchaeota. The correlation among the microbes in the lakes was mainly positive, suggesting they can survive in the harsh environments through synergistic interactions. Statistical analyses indicated that physicochemical characteristics rather than spatial factors shaped the microbial communities in the desert lakes. The pH was the most important environmental factor controlling alpha diversity, while salinity was the major driver determining microbial community structure in BJD lakes. In contrast, geographic factors had no significant impact on the microbial community compositions.