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1.
Due to the sea level rise and the excessive exploitation of freshwater, seawater intrusion is becoming a critical issue. To clarify the degree of seawater intrusion in Donghai Island and the microbial community structure and functional response to seawater intrusion, groundwater samples and sediment samples were collected at profiles A, B; the profiles were along the direction of groundwater flow, perpendicular to the coastline, a hydrogeochemical survey and soil microbial community analysis were also performed. The hydrogeochemistry analysis showed that the chemical type of groundwater was Na–Cl, brackish water was dominant in the area, and coastal groundwater was strongly affected by seawater intrusion. The effect of seawater intrusion on structural and functional diversity of soil microbes was analyzed from soil samples of the study area, by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). The results of DGGE patterns and phylogenetic tree show that the extent of seawater intrusion has directly influenced soil microbial community structure. The changes of microbial community structure might be related to the major elements’ concentrations in groundwater. Phylogenetic affiliation indicated that γ-proteobacteria were dominated in the profile A, while β-proteobacteria were mainly appeared in the profile B. The Flavobacteriaceae was only appeared at the shrimp ponds nearby.  相似文献   

2.
The Batinah coastal plain in northern Oman has experienced a severe deterioration of groundwater quality due to seawater intrusion as a result of excessive groundwater abstraction for agricultural irrigation. Upgrading all farms to fully automated irrigation technology based on soil moisture sensors may significantly reduce the water demand and lead to recovering groundwater levels. This study compares the effects of smart irrigation technology, recharge dams, and a combination of both on seawater intrusion in the coastal aquifer of the Batinah. A groundwater flow and transport model is used to simulate the effect of reduced pumping rates on seawater intrusion for various intervention scenarios over a simulation period of 30 years, and an economic analysis based on cost-benefit analysis is conducted to estimate the potential benefits. Results indicate that a combination of smart irrigation and recharge dams may prevent further deterioration of groundwater quality over the next 30 years. In conjunction with increased efficiency, this combination also generates the highest gross profit. This outcome shows that the problem of seawater intrusion needs to be tackled by a comprehensive, integrated intervention strategy.  相似文献   

3.
Irrigation by treated wastewater (TWW) can pollute the soil by different organic and inorganic compounds. The pollution level can depend on the irrigation period, soil nature, and wastewater characteristics. Since 1989, the Zaouit Sousse area (central Tunisian) has been irrigated by treated wastewater. The irrigation period and the mineralogy of soil composition change from one locality to another in Zaouit Sousse area. In this work, we are interested in organic compounds, polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs) evolution. One control soil (S1) and four irrigated areas soil (S2, S3, S4, and S5) were chosen. The soil samples differ by the irrigation period and soil characteristics. Total PAHs content in control soil was 66.2 ng?g?1 and in irrigated areas were between 46.23 and 129.51 ng?g?1. The PAHs content in irrigated soil, except S5 which has been irrigated with wastewater for 20 years and contains the highest clay fraction percent, decreased with the irrigation period (from 0 to 20 years). The microbial degradation may decrease the PAHs concentrations in the soil thanks to bacterium brought by TWW and the important soil permeability. Concentration of heavy metals ranged from 24 to 1,320 μg?L?1. The HMs (Cu, Cr, Zn, Fe, Ni, Pb, and Cd) contents decreased with the irrigation period (from 10 to 20 years). So, following the PAHs aerobic bio-degradation, this organic compound discharges their absorbed heavy metals which leached to deeper levels. The Cr, Cu, Al, Zn, and Cd mobility depend on the clay yield too. However, the PAHs and Pb mobility are also related to humic substance quantities. Cr and Cu have affinities both to clay and humic substance quantities.  相似文献   

4.
Reclamation of saline soil plays an important role in supporting high population growth in China. To evaluate the effects of reclamation and sustainability of salt-affected land production, soil chemical properties, enzyme activities, microbial community structure and function in sites reclaimed in 1976, 1984 and 1996 were characterized. The 2009 site was left to succession fallow and chosen as a control site. Results showed that electrical conductivity (EC) and pH decreased rapidly after the soil forming process started. An accumulation of soil organic C as a result of farming was observed. In all sites, inorganic N and available P were increased within 33 years after reclamation and commencement of agriculture. As a result of reclamation, soil enzyme activity (β-glucosidase, phosphatase, urease and arylsulfatase) was increased. There were no significant differences in soil enzyme activity between the sites reclaimed in 1976 and 1984, with the exception of phosphatase. Carbon source utilization patterns were less diverse in control soil than in treatment sites. The activities of reclamation resulted in synthesis of new phospholipid fatty acids (14:0, 17:1 c9, 16:0 2OH, 17:0 10Me, i17:0, 20:4 ω6c). Principal component analyses showed that the sites reclaimed in 1976 and 1984 clustered together and were distinct from 1996. Taken together, reclamation showed significantly increased soil quality and microbial activity. EC was the main limiting soil quality characteristic, which showed a comparative steady state after a reclamation time of 33 years. Differences in soil enzyme activity and microbial community function after long-term reclamation have potential to be reflected in soil functional integrity and ecosystem service.  相似文献   

5.
Sang  Shilei  Dai  Heng  Hu  Bill X.  Huang  Zhenyu  Liu  Yujiao  Xu  Lijia 《Hydrogeology Journal》2022,30(6):1833-1845

Microbes live throughout the soil profile. Microbial communities in subsurface horizons are impacted by a saltwater–freshwater transition zone formed by seawater intrusion (SWI) in coastal regions. The main purpose of this study is to explore the changes in microbial communities within the soil profile because of SWI. The study characterizes the depth-dependent distributions of bacterial and archaeal communities through high-throughput sequencing of 16S rRNA gene amplicons by collecting surface soil and deep core samples at nine soil depths in Longkou City, China. The results showed that although microbial communities were considerably impacted by SWI in both horizontal and vertical domains, the extent of these effects was variable. The soil depth strongly influenced the microbial communities, and the microbial diversity and community structure were significantly different (p < 0.05) at various depths. Compared with SWI, soil depth was a greater influencing factor for microbial diversity and community structure. Furthermore, soil microbial community structure was closely related to the environmental conditions, among which the most significant environmental factors were soil depth, pH, organic carbon, and total nitrogen.

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6.
森林生态系统的土壤微生物群落组成和活性,是影响生物地球化学循环、有机质代谢和土壤质量的关键因素.磷脂脂肪酸(PLFA)是一类可有效表征活体微生物群落结构的生物标志物,而其单体稳定碳同位素(δ13C)水平对土壤微生物植物碳代谢具有独特的指示作用.本次研究以土壤PLFA为对象,分析了我国位处纬度梯度带上(24°N～47°N...  相似文献   

7.
大兴安岭多年冻土区不同林型土壤微生物群落特征   总被引：1，自引：1，他引：0  
高纬度多年冻土区是全球变化的敏感区域,揭示不同林型土壤微生物群落的演变规律,对于理解气候变化对寒区生态系统的影响机制具有重要意义。以大兴安岭多年冻土区3种典型林型（落叶松林、樟子松林和白桦林）为研究对象,运用磷脂脂肪酸法（PLFA）系统研究土壤微生物群落结构间差异及与土壤因子的关系。结果表明：不同林型土壤中共检测到38种PLFA生物标记,含量较高的PLFA为16∶0、18∶0、19∶0和18∶2ω6c;各类群微生物中,细菌PLFA含量最高,占总磷脂脂肪酸的83.78%~90.55%,其次为真菌,放线菌最低;白桦林土壤总磷脂脂肪酸、革兰氏阴性菌、革兰氏阳性菌、真菌和放线菌的含量最高分别为22.03、5.13、4.90、1.88和0.77 nmol·g-1,而樟子松林最低分别为14.25、2.75、2.75、1.34和0.51 nmol·g-1。Shannon-Wiener多样性指数主要表现为白桦林 > 落叶松林 > 樟子松林。冗余分析结果为：土壤含水量、全氮、总有机碳与总磷脂脂肪酸、细菌、革兰氏阳性菌和革兰氏阴性菌呈显著正相关（P<0.05）;铵态氮、硝态氮、全磷与真菌和放线菌呈显著正相关（P<0.05）。大兴安岭多年冻土区不同林型间土壤微生物群落特征存在显著差异,土壤含水量、全氮和总有机碳是影响多年冻土微生物群落结构的主要因素。  相似文献   

8.
Bioremediation strategies continue to be developed to mitigate the environmental impact of petroleum hydrocarbon contamination. This study investigated the ability of soil microbiota, adapted by prior exposure, to biodegrade petroleum. Soils from Barrow Is. (W. Australia), a class A nature reserve and home to Australia’s largest onshore oil field, were exposed to Barrow production oil (50 ml/kg soil) and incubated (25 °C) for successive phases of 61 and 100 days. Controls in which oil was not added at Phase I or II were concurrently studied and all treatments were amended with the same levels of additional nutrient and water to promote microbial activity. Prior exposure resulted in accelerated biodegradation of most, but not all, hydrocarbon constituents in the production oil. Molecular biodegradation parameters measured using gas chromatography–mass spectrometry (GC–MS) showed that several aromatic constituents were degraded more slowly with increased oil history. The unique structural response of the soil microbial community was reflected by the response of different phospholipid fatty acid (PLFA) sub-classes (e.g. branched saturated fatty acids of odd or even carbon number) measured using a ratio termed Barrow PLFA ratio (B-PLFAr). The corresponding values of a previously proposed hydrocarbon degrading alteration index showed a negative correlation with hydrocarbon exposure, highlighting the site specificity of PLFA-based ratios and microbial community dynamics. B-PLFAr values increased with each Phase I and II addition of production oil. The different hydrocarbon biodegradation rates and responses of PLFA subclasses to the Barrow production oil probably relate to the relative bioavailability of production oil hydrocarbons. These different effects suggest preferred structural and functional microbial responses to anticipated contaminants may potentially be engineered by controlled pre-exposure to the same or closely related substrates. The bioremediation of soils freshly contaminated with petroleum could benefit from the addition of exhaustively bioremediated soils rich in biota primed for the impacting hydrocarbons.  相似文献   

9.
磷脂脂肪酸(phospholipid fatty acid,PLFAs)是活体微生物细胞膜的重要组成部分,微生物通过改变细胞膜中PLFA组成,快速响应环境变化.目前,表土PLFAs研究主要集中于季节和植被群落变化对微生物群落结构影响,对于不同生境下表土PLFAs揭示的微生物群落结构的差异性尚不明确.基于此,对神农架大九湖7种不同生境表土进行PLFAs研究.结果表明,表土样品PLFAs集中分布于C14到C19;除湿生泥炭沼泽和湿生半退化沼泽生境外,其他生境以n16:0为主峰.不同生境的PLFAs含量差异较大,沼泽生境TPLFAs含量是草甸及阔叶林生境下的3~8倍.PLFAs组成还揭示出生境间主要受到pH和含水率的影响,微生物群落结构存在差异.不同生境下表层土壤PLFAs揭示的微生物丰度和群落结构具有一定的相似性及差异性.运用PLFAs对微生物量及微生物群落结构的划分将有助于更好的了解区域生态系统中微生物群落结构的变化,为研究微生物参与碳循环及古生态研究奠定基础.   相似文献   

10.
The main objective of this study was to identify the main sources and processes that control SO4 2? groundwater concentrations in the Jinghuiqu irrigation district of China using isotope analysis. Lysimeter irrigation experiments and numerical modeling were used to assess the impact of long-term irrigation practices on sulfate transport, when different sources of irrigation water were used. SO4 2? concentrations in the groundwater of the entire irrigation area increased significantly from the years 1990 (a mean value was 4.8 mmol L?1) to 2009 (a mean value was 9.84 mmol L?1). The δ34S-SO4 2? values (ranging from +5.27 to +10.69 ‰) indicated that sulfates in groundwater were initially predominantly derived from dissolution of minerals. However, no soluble sulfate minerals (gypsum and/or mirabilite) were detected after 1990. To better understand this seeming anomaly, water content and SO4 2? data were collected before and after the field irrigation experiment and analyzed using the HYDRUS-1D and HP1 software packages. The experimental data were also used to assess sulfate leaching when different sources of irrigation water were used under current irrigation practices. The dissolved sulfate concentrations in the soil profile increased significantly when groundwater was used for infiltration compared to the use of surface water. Irrigation water sources had a great impact on the increase of sulfate concentrations in the shallow groundwater, especially when groundwater with elevated concentrations was used for irrigation.  相似文献   

11.
During the past 50 years, the amount of agricultural fertilizer used in Northern China increased from about 7.5 kg ha?1 in the 1950s to approximately 348 kg ha?1 in the 1990s. Given that little is known about the effects of nitrogen fertilization on soil labile carbon fraction in Northern China, this paper evaluated such effects in terms of microbial biomass and dissolved organic carbon in the Sanjiang Plain located in Northeast China. Soils with different cultivation time and undisturbed marsh with Deyeuxia angustifolia were selected to study the effects of nitrogen fertilization on the soil labile organic fractions microbial C (biomass C, microbial quotient, and basal respiration) and to estimate the contributions of nitrogen input on the dynamics of soil labile carbon. Continuous nitrogen application decreased total organic and dissolved organic carbon concentrations significantly, leading to the lack of carbon source for microbes. Therefore, continuous nitrogen fertilizer application induced negative effects on measured soil microbiological properties. However, a moderate nitrogen application rate (60 kg N ha?1) stimulated soil microbial activity in the short term (about 2 months), whereas a high nitrogen application rate (150 kg N ha?1) inhibited measured soil microbiological properties in the same period.  相似文献   

12.
农业作为通辽科尔沁地区的传统产业,是当地重要经济产业之一.了解土壤微生物群落结构和功能及其影响因素对农作物种植、污染土地修复等具有重要意义.采用Illumina Miseq高通量测序技术、FAPROTAX.1.1功能预测平台等方法,在该区采集71个土壤样品,分析其地球化学特征和微生物群落特征并对微生物群落进行功能预测,同时探讨不同环境因子和空间因子对微生物群落的影响.结果显示:微生物群落由变形菌门（Proteobacteria）（19.77%）、奇古菌门（Thaumarchaeota）（17.85%）、酸杆菌门（Acidobacteria）（17.14%）和放线菌门（Actinobacteria）（15.58%）等构成;功能预测表明该区存在大量活跃的参与氮循环过程的微生物功能群,其中有氧氨氧化功能群为该区的优势微生物功能群.方差分解分析显示,在对微生物群落结构差异的可解释范围内环境因子比空间因子的解释量更大.Mantel检验结果显示,整体微生物群落与土壤pH、EC、TN、C/N及Mg、Na、Sr元素含量显著相关（p < 0.05）.综合分析表明,pH、EC和Sr元素含量是影响通辽科尔沁地区土壤微生物群落结构和功能及多样性的主要环境因素.   相似文献   

13.
Microbial mat communities host complex biogeochemical processes and play a role in the formation of most carbonate rocks by influencing both carbonate precipitation and dissolution. In this study, the biogeochemistry of microbial mats from the hypersaline Salt Pond, San Salvador, Bahamas are described using scanning electron microscopy, X-ray diffraction, microelectrode profiling, fatty acid methyl esters, and carbon and nitrogen analyses. These microbial mats are distinctly layered both chemically and with regard to composition of microbial community, where significant (?? < 0.05) differences are noted between layers and cores. Furthermore, an oxic upper zone and an H2S-rich lower zone dominate the Salt Pond microbial mats, where H2S concentrations were measured approaching 8 mM. The high H2S concentrations along with the lacking evidence of mineral precipitation in SEM images point to the prevalence of carbonate dissolution. Moreover, the high concentrations of organics (3?C9%) reveal that the mats are self-sourcing and can provide ample fuel to sustain the highly active heterotrophic (both aerobic and anaerobic) metabolism. Seasonal differences in sulfide and oxygen concentrations in Salt Pond mats indicate that the carbonate dissolution and precipitation reactions are dynamic in this hypersaline lake.  相似文献   

14.
Aquifer thermal energy storage may result in increases in the groundwater temperature up to 70 °C and more. This may lead to geochemical and microbiological alterations in the aquifer. To study the temperature effects on the indigenous microbial community composition, sediment column experiments at four different temperatures were carried out and the effluents were characterized geochemically and microbiologically. After an equilibrium phase at groundwater temperature of 10 °C for 136 days, one column was kept at 10 °C as a reference and the others were heated to 25, 40 and 70 °C. Genetic fingerprinting and quantitative PCR revealed a change in the bacterial community composition and abundance due to the temperature increase. While at 25 °C only slight changes in geochemical composition and gene copy numbers for bacteria were observed, increasing concentrations of total organic carbon in the 40 °C column were followed by a strong increase in bacterial abundance. Thermophilic bacteria became dominant at 70 °C. Temporary sulfate reduction took place at 40 and 70 °C and this correlated with an increased abundance of sulfate-reducing bacteria (SRB). Furthermore, a coexistence of SRB and sulfur-oxidizing bacteria (SOB) at all temperatures indicated an interaction of these physiological groups in the sediments. The results show that increased temperatures led to significant shifts in the microbial community composition due to the altered availability of electron donors and acceptors. The interplay of SRB and SOB in sedimentary biofilms facilitated closed sulfur cycling and diminished harmful sulfur species.  相似文献   

15.
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16.
The vegetation community succession influences soil nutrient cycling, and this process is mediated by soil microorganisms in the forest ecosystem. A degraded succession series of karst forests were chosen in which vegetation community changed from deciduous broadleaved trees (FO) toward shrubs (SH), and shrubs–grasses (SHG) in the southwest China. Soil organic carbon (SOC), total nitrogen (TN), labile organic carbon (LOC), water extractable organic matter (WEOM), microbial biomass carbon and nitrogen (MBC and MBN), bacterial and fungal diversity, as well as soil enzyme activities were tested. The results showed that SOC, LOC, MBC, MBN, and enzyme activities declined with vegetation succession, with the relatively stronger decrease of microbial biomass and functions, whereas WEOM was higher in SHG than in other systems. In addition, soil bacterial and fungal composition in FO was different from both SH and SHG. Despite positive relationship with SOC, LOC, and TN (p < 0.01), MBC, MBN appeared to be more significantly correlated to LOC than to SOC. It suggested that vegetation conversion resulted in significant changes in carbon fractions and bioavailability, furthermore, caused the change in soil microbial community and function in the forest ecosystem.  相似文献   

17.
Methanotrophic biomass and community structure were assessed for a soil column enriched with natural gas. An increase in microbial biomass, based on phospholipid ester-linked fatty acids (PLFA), was apparent for the natural gas-enriched column relative to a control column and untreated surface soil. Following GC-MS analyses of the derivatized monounsaturated fatty acids, the major component (22% of the PLFA) of the natural gas-enriched column was identified as 18·1Δ 10c. This relatively novel fatty acid has only been previously reported as a major component in methanotrophs. Its presence in the soil, together with other supportive evidence, implies that this microbial metabolic group makes a large contribution to the column flora. Other microbial groups were also recognized and differences compared between the soils analysed. A recently developed HPLC method for the separation and characterisation of archaebacterial phospholipid-derived signature di- and tetra-ether lipids was used to examine methane-producing digesters. With this technique, methanogenic biomasses of approximately 1011 bacteria per g dry weight of digestor material were determined. Differences between ratios of diether to tetraether phospholipids were apparent for the digestors analysed, though the causes are at this stage unknown. Taken together, these two methods can be used to estimate methanotrophic and methanogenic contributions in both model systems and environmental samples.  相似文献   

18.
The effect of glucose, chicken manure, and filter mud on the ammonium and nitrate concentrations, ammonia-oxidizing bacterial community and bacterial community in latosolic red soils during the incubation of microcosms was investigated. The soil nitrate concentration was significantly lower in the glucose-treated soil than in the filter mud or chicken manure-treated soil from days 2 and 5 to 21 of incubation. The ammonia-oxidizing bacteria community composition, measured by terminal restriction fragment length polymorphism analysis, was different among the treatments 9 days after incubation, suggesting that the control soil without external fertilization had a low 283-bp (Nitrosospira) fragment relative abundance (27 %) compared with the glucose-treated (62 %), filter mud (73 %) and chicken manure (78 %) samples. Additionally, 491-bp fragments (Nitrosomonas) were detected in all the soil treatments except for the control soil, and 48-bp fragments (from different Nitrosomonas) were detected in the chicken manure-treated soil. The bacterial community structure was markedly changed in the glucose-treated soil on day 9 and in the filter mud-treated soil on day 31, indicating that the effect of filter mud on the bacterial community is delayed compared to the effect of glucose. The chicken manure-treated soil showed less change, similar to that of the control soil. Glucose fertilization greatly increased the soil bacterial abundance and functional diversity; however, the chicken manure and filter mud did not stimulate soil bacterial activity on day 9. These results indicated that nitrification may have been somewhat suppressed in the glucose-treated soils, which was possibly related to the improving ammonia-oxidizing bacterial community, bacterial community and activity via the available carbon application. The filter manure and chicken manure treatments demonstrated fewer effects. These results suggest that organic carbon quality, e.g., increasing the available carbon, regulates the nitrification process and is beneficial to reducing soil nitrogen losses.  相似文献   

19.
The extensive spread ofPhragmites australis throughout brackish marshes on the East Coast of the United States is a major factor governing management and restoration decisions because it is assumed that biogeochemical functions are altered by the invasion. Microbial activity is important in providing wetland biogeochemical functions such as carbon and nitrogen cycling, but there is little known about sediment microbial communities inPhragmites marshes. Microbial populations associated with invasivePhragmites vegetation and with native salt marsh cordgrass,Spartina alterniflora, may differ in the relative abundance of microbial taxa (community structure) and in the ability of this biota to decompose organic substrates (community biogeochemical function). This study compares sediment microbial communities associated withPhragmites andSpartina vegetation in an undisturbed brackish marsh near Tuckerton, New Jersey (MUL), and in a brackish marsh in the anthropogenically affected Hackensack meadowlands (SMC). We use phospholipid fatty acid (PLFA) analysis and enzymataic activity to profile sediment microbial communities associated with both plants in each site. Sediment analyses include bulk density, total organic matter, and root biomass. PLFA profiles indicate that the microbial communities differ between sites with the undisturbed site exhibiting greater fatty acid richness (62 PLFA recovered from MUL versus 38 from SMC). Activity of the 5 enzymes analyzed (β-glucosidase, acid phosphatase, chitobiase, and 2 oxidases) was higher in the undisturbed site. Differences between vegetation species as measured by Principal Components Analysis were significantly greater at the undisturbed MUL site than at SMC, and patterns of enzyme activity and PLFAs did not correspond to patterns of root biomass. We suggest that in natural wetland sediments, macrophyte rhizosphere effects influence the community composition of sediment microbial populations. Physical and chemical site disturbances may impose limits on these rhizosphere effects, decreasing sediment microbial diversity and potentially, microbial biogeochemical functions.  相似文献   

20.
Groundwater is of a paramount importance in arid areas, as it represents the main water resource to satisfy the different needs of the various sectors. Nevertheless, coastal aquifers are generally subjected to seawater intrusion and groundwater quality degradation. In this study, the groundwater quality of the coastal Jeffara aquifer (southeastern Tunisia) is evaluated to check its suitability for irrigation purposes. A total of 74 groundwater samples were collected and analyzed for various physical and chemical parameters, such as, electrical conductivity, pH, dissolved solids (TDS), Na, K, Ca, Mg, Cl, HCO3, and SO4. Sodium adsorption ratio, magnesium adsorption ratio, Sodium percentage, and permeability index were calculated based on the analytical results. The analytical results obtained show a strong mineralization of the water in the studied aquifer. TDS concentrations range from 3.40 to 18.84 g?L?1. Groundwater salinity was shown to be mainly controlled by sodium and chloride. The dominant hydrochemical facieses are Na–Cl–Ca–SO4, mainly as a result of mineral dissolution (halite and gypsum), infiltration of saline surface water, and seawater intrusion. Assessment of the groundwater quality of the different samples by various methods indicated that only 7% of the water, in the northwest of the study area, is considered suitable for irrigation purposes while 93% are characterized by fair to poor quality, and are therefore just suitable or unsuitable for irrigation purposes.  相似文献   

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