Survey of human virus occurrence in wastewater-recharged groundwater on Long Island.

Treated wastewater effluents and groundwater observation wells from three sewage recharge installations located on Long Island were assayed on a monthly basis for indigenous human enteroviruses and coliform bacteria for a period of 1 year. Viruses were detected in groundwater at sites where recharge basins were located less than 35 feet (ca. 10.6 m) above the aquifer. Results from one of the sites indicated the horizontal transfer of viable viruses through the groundwater aquifer.     

Vertical change in dissolved organic carbon and oxygen at the water table region of an aquifer recharged with stormwater: biological uptake or mixing?

Decreases in dissolved organic carbon (DOC) and dissolved oxygen (DO) with increasing depth below the groundwater table are often considered as evidence for aerobic respiration; however, they may reflect mixing of infiltrating water and groundwater. We found that groundwater DOC concentration was on average 0.3 mg C l^?1 higher and DO concentration 1.5 mg O₂ l^?1 lower at recharge sites replenished with stormwater than at reference sites fed by direct infiltration of rain water from the land surface. Groundwater DOC increased and DO decreased with increasing vadose zone thickness (VZT) at both recharge and reference sites. There was no significant interaction between the effects of stormwater infiltration and VZT. Vertical changes in DOC and DO below the groundwater table at recharge sites could account for by simple mixing of infiltrating stormwater and groundwater. Moreover, aquifer sediment respiration (SR) was not significantly higher at recharge sites than at reference sites. However, slow filtration column experiments showed that SR increased significantly with an increasing supply of easily biodegradable DOC. We conclude that the observed reduction in DOC below the groundwater table at recharge sites was essentially due to water mixing rather than biological uptake because of the low biodegradability of the DOC and the short transit time of stormwater in the upper layers of groundwater. Our results highlight the need to distinguish between the effect of hydrological and biological processes on DOC and DO patterns below the groundwater before conclusions are made on the efficiency of groundwater in degrading surface-derived DOC.     

Ecological assessment of groundwater trophic status by using artificial substrates to monitor biofilm growth and activity

The European water legislation highlights the necessity of developing ecological criteria for assessing the quality of aquatic ecosystem. While a multitude of ecological indicators has been proposed and validated for streams, rivers and lakes, these indicators are not available for groundwater ecosystems. In the present study, we developed a method based on the measurements of the growth and activity of microorganisms developed on artificial substrates (glass beads) incubated in wells to characterize the trophic status of groundwater. Incubation sites were selected in an urban aquifer where previous works showed contrasting trophic conditions in groundwater due to artificial groundwater recharge practices. Total proteins, total carbohydrates, dehydrogenase and hydrolytic activities were measured on glass beads incubated in wells for two periods of 2 months (October–December 2010 and April–June 2011). Biofilm measured on glass beads was significantly more developed and active in wells where groundwater was enriched with dissolved organic matter due to artificial groundwater recharge. Indeed, most microbial variables (total proteins and dehydrogenase activities for the two incubation periods and hydrolytic activities for the second incubation period) were significantly and positively correlated with the concentrations of dissolved organic carbon (DOC) in groundwater. The availability of phosphorus also tended to influence biofilm growth (assessed by total carbohydrates) when PO₄³⁻ concentrations were lower than 50 μg/l. Overall, our study clearly demonstrated that artificial substrates acting as colonisable area for microorganisms could be used to efficiently monitor nutrient enrichment in aquifers.     

Patterns in groundwater nitrogen concentration in the floodplain of a subtropical stream (Wollombi Brook,New South Wales)

The sources of groundwater and the patterns in groundwater dissolved N and DOC concentration in the floodplain of a subtropical stream (Wollombi Brook, New South Wales) were studied over a 2-year period using three piezometer transects. While the stream was generally a discharge area for regional groundwater, this source represented only a small contribution to either the water or N budget of the alluvial aquifer. Groundwater–surface water interactions appeared mostly driven by cycles of bank recharge and discharge between the stream and the alluvial aquifer. DON and NH₄⁺ were the principal forms of dissolved N in groundwater, consistent with the primarily suboxic to anoxic conditions in the alluvial aquifer. A plume of groundwater NO₃⁻ was found at one transect where oxic conditions persisted within the riparian zone. The origin of the NO₃⁻ plume was hypothesized to be soil NO₃⁻ from the riparian zone flushed to the water table during recharge events. When present, NO₃⁻ did not reach surface water because conditions in the alluvial aquifer in the vicinity of the stream were always reduced. The concentration of groundwater DOC was variable across the floodplain and may be related to the extent of the vegetation cover. Overall, transformation and recycling of N during lateral exchange processes, as opposed to discharge of new N inputs from regional groundwater, appears to primarily control N cycling during groundwater–surface water interactions in this subtropical floodplain.     

Suitability for developing riverside groundwater sources along Songhua River,Northeast China

Riverbank filtration is a natural water treatment technology that consists of extracting water from rivers by pumping wells located in the adjacent alluvial aquifer. It is vital to choose the most appropriate from multiple potential candidate sites, which is a complex procedure and seldom paid attention to. In this study, a method system including multicriteria evaluation indexes was developed with which the suitability of bank filtration along the Songhua River of China for developing riverside groundwater sources was assessed. The system was comprised of main suitability indexes for water quantity, water quality, interaction intensity between surface water and groundwater, and the exploitation condition of aquifer condition, weights of which were determined by specialist marking methods. Based on this assessment system, the suitability of the study area was divided into five grades. Results show that riversides along Lalin River, Hulan River, and the middle part of Songhua River are suitable for developing riverside groundwater sources.     

Spatio-temporal patterns of microbial communities in a hydrologically dynamic pristine aquifer

Seasonal patterns of groundwater and sediment microbial communities were explored in a hydrologically dynamic alpine oligotrophic porous aquifer, characterized by pronounced groundwater table fluctuations. Rising of the groundwater level in consequence of snow melting water recharge was accompanied by a dramatic drop of bacterial Shannon diversity in groundwater from H' = 3.22 ± 0.28 in autumn and winter to H' = 1.31 ± 0.35 in spring and summer, evaluated based on T-RFLP community fingerprinting. Elevated numbers of bacteria in groundwater in autumn followed nutrient inputs via recharge from summer rains and correlated well with highest concentrations of assimilable organic carbon. Sterile sediments incubated to groundwater in monitoring wells were readily colonized reaching maximum cell densities within 2 months, followed by a consecutive but delayed increase and leveling-off of bacterial diversity. After 1 year of incubation, the initially sterile sediments exhibited a similar number of bacteria and Shannon diversity when compared to vital sediment from a nearby river incubated in parallel. The river bed sediment microbial communities hardly changed in composition, diversity, and cell numbers during 1 year of exposure to groundwater. Summing up, the seasonal hydrological dynamics were found to induce considerable dynamics of microbial communities suspended in groundwater, while sediment communities seem unaffected and stable in terms of biomass and diversity.     

Surface Water Linkages Regulate Trophic Interactions in a Groundwater Food Web

Groundwaters are increasingly viewed as resource-limited ecosystems in which fluxes of dissolved organic carbon (DOC) from surface water are efficiently mineralized by a consortium of microorganisms which are grazed by invertebrates. We tested for the effect of groundwater recharge on resource supply and trophic interactions by measuring physico-chemistry, microbial activity and biomass, structure of bacterial communities and invertebrate density at three sites intensively recharged with surface water. Comparison of measurements made in recharge and control well clusters at each site showed that groundwater recharge significantly increased fluxes of DOC and phosphate, elevated groundwater temperature, and diminished dissolved oxygen (DO). Microbial biomass and activity were significantly higher in recharge well clusters but stimulation of autochthonous microorganisms was not associated with a major shift in bacterial community structure. Invertebrate assemblages were not significantly more abundant in recharge well clusters and did not show any relationship with microbial biomass and activity. Microbial communities were bottom-up regulated by DOC and nutrient fluxes but trophic interactions between microorganisms and invertebrates were apparently limited by environmental stresses, particularly DO depletion and groundwater warming. Hydrological connectivity is a key factor regulating the function of DOC-based groundwater food webs as it influences both resource availability for microorganisms and environmental stresses which affect energy transfer to invertebrates and top-down control on microorganisms.     

Quantitative PCR Monitoring of Antibiotic Resistance Genes and Bacterial Pathogens in Three European Artificial Groundwater Recharge Systems

Aquifer recharge presents advantages for integrated water management in the anthropic cycle, namely, advanced treatment of reclaimed water and additional dilution of pollutants due to mixing with natural groundwater. Nevertheless, this practice represents a health and environmental hazard because of the presence of pathogenic microorganisms and chemical contaminants. To assess the quality of water extracted from recharged aquifers, the groundwater recharge systems in Torreele, Belgium, Sabadell, Spain, and Nardò, Italy, were investigated for fecal-contamination indicators, bacterial pathogens, and antibiotic resistance genes over the period of 1 year. Real-time quantitative PCR assays for Helicobacter pylori, Yersinia enterocolitica, and Mycobacterium avium subsp. paratuberculosis, human pathogens with long-time survival capacity in water, and for the resistance genes ermB, mecA, blaSHV-5, ampC, tetO, and vanA were adapted or developed for water samples differing in pollutant content. The resistance genes and pathogen concentrations were determined at five or six sampling points for each recharge system. In drinking and irrigation water, none of the pathogens were detected. tetO and ermB were found frequently in reclaimed water from Sabadell and Nardò. mecA was detected only once in reclaimed water from Sabadell. The three aquifer recharge systems demonstrated different capacities for removal of fecal contaminators and antibiotic resistance genes. Ultrafiltration and reverse osmosis in the Torreele plant proved to be very efficient barriers for the elimination of both contaminant types, whereas aquifer passage followed by UV treatment and chlorination at Sabadell and the fractured and permeable aquifer at Nardò posed only partial barriers for bacterial contaminants.     

Anaerobic Biodegradation and Hydrogeochemical Controls on Natural Attenuation of Trichloroethene in an Inland Forested Wetland

A field and laboratory investigation of natural attenuation, focusing on anaerobic biodegradation, was conducted in a forested wetland where a plume of trichloroethene discharges from a sand aquifer through organic-rich wetland and stream-bottom sediments. The rapid response of the wetland hydrology to precipitation events altered groundwater flow and geochemistry during wet conditions in the spring compared to the drier conditions in the summer and fall. During dry conditions, partial reductive dechlorination of trichloroethene to cis-1,2-dichloroethene occurred in methanogenic wetland porewater. Influx of oxygenated recharge during wet conditions resulted in a change from methanogenic to iron-reducing conditions and a lack of 1,2-dichloroethene production in the wet spring conditions. During these wet conditions, dilution was the primary attenuation mechanism evident for trichloroethene in the wetland porewater. Trichloroethene degradation was insignificant in anaerobic microcosms constructed with the shallow wetland sediment, and microbiological analyses showed a low microbial biomass and absence of known dehalorespiring microorganisms. Despite the typically organic-rich characteristic of wetland sediments, natural attenuation by anaerobic degradation may not be an effective groundwater remediation for chlorinated solvents at all sites.     

Phosphorus Limitation in Boreal Forests: Effects of Aluminum and Iron Accumulation in the Humus Layer

Plant growth in boreal forests is generally considered to be predominantly nitrogen (N) limited, but forested groundwater discharge areas may be exceptions. In this study, we conducted tests to determine whether highly productive forested groundwater discharge areas generally differ from adjacent groundwater recharge areas in terms of humus chemistry and the availability of phosphorus (P) and N to plants. We investigated six forested sites, divided into groundwater discharge and adjacent groundwater recharge areas, in northern Sweden. The humus layers of the forested groundwater discharge areas were clearly distinguished from the adjacent groundwater recharge areas by having higher acid-digestible calcium (Ca) and/or aluminium (Al) and iron (Fe) content and higher organic P and N content. Soil solution inorganic N (NH₄ ⁺ and NO₃ ⁻) and pH were higher in the groundwater discharge areas than in the groundwater recharge areas. The organic P content showed a positive linear relationship to the Al and Fe content in the humus layer, indicating that organic P is associated with Al and Fe compounds in the humus. A plant bioassay using humus substrate from one groundwater discharge area and the adjacent groundwater recharge area found that plants grown in groundwater discharge area humus (with a high P-fixation capacity) increased their biomass upon P fertilization, whereas no growth response was found for N additions. By contrast, plants grown in humus from the groundwater recharge area did not respond to added P unless N was added too. This study suggests that groundwater discharge can affect the nutrient availability of N and P both directly, via increased P fixation due to the redistribution of Al and Fe, and indirectly, via the inflow of groundwater high in Ca and alkalinity, maintaining a high pH in the humus layer that favors in situ N turnover processes. Received 2 March 2001; Accepted 9 November 2001.     

Naproxen Adsorption-Desorption in a Sandy Aquifer Matrix: Characterisation of Hysteretic Behavior at Two Different Temperature Values

Adsorption/desorption processes (sorption isotherms) of Naproxen in a sandy aquifer matrix sediment were investigated using batch tests to compare Naproxen sorption behavior at 15°C and 25°C. Both temperatures are representative of the aquifer media and environmental conditions. Adsorption was well described by linear isotherms with low sorption affinity to aquifer material (K_d of 0.4 μg kg^?1) at both temperatures (15°C and 25°C). Desorption isotherm coefficients at 15°C and 25°C were 5.0 and 4.9, respectively. Naproxen hysteresis indices were between 9.98 and 10.8, indicating that a Naproxen fraction may be irreversibly fixed in the aquifer media, being higher at 25°C (10.88) compared to 15°C, showing a decreasing trend with increasing compound concentration at 15°C. The low sorption of Naproxen leads to potential leaching to groundwater if present in irrigation water, and its prevalence in an aquifer media when directly injected in wells for groundwater recharge.     

Spatial and temporal changes in microbial community structure associated with recharge-influenced chemical gradients in a contaminated aquifer

In a contaminated water-table aquifer, we related microbial community structure on aquifer sediments to gradients in 24 geochemical and contaminant variables at five depths, under three recharge conditions. Community amplified ribsosomal DNA restriction analysis (ARDRA) using universal 16S rDNA primers and denaturing gradient gel electrophoresis (DGGE) using bacterial 16S rDNA primers indicated: (i). communities in the anoxic, contaminated central zone were similar regardless of recharge; (ii). after recharge, communities at greatest depth were similar to those in uncontaminated zones; and (iii). after extended lack of recharge, communities at upper and lower aquifer margins differed from communities at the same depths on other dates. General aquifer geochemistry was as important as contaminant or terminal electron accepting process (TEAP) chemistry in discriminant analysis of community groups. The Shannon index of diversity (H) and the evenness index (E), based on DGGE operational taxonomic units (OTUs), were statistically different across community groups and aquifer depths. Archaea or sulphate-reducing bacteria 16S rRNA abundance was not clearly correlated with TEAP chemistry indicative of methanogenesis or sulphate reduction. Eukarya rRNA abundance varied by depth and date from 0 to 13% of the microbial community. This contaminated aquifer is a dynamic ecosystem, with complex interactions between physical, chemical and biotic components, which should be considered in the interpretation of aquifer geochemistry and in the development of conceptual or predictive models for natural attenuation or remediation.     

Metagenomic comparison of microbial communities inhabiting confined and unconfined aquifer ecosystems

A metagenomic analysis of two aquifer systems located under a dairy farming region was performed to examine to what extent the composition and function of microbial communities varies between confined and surface-influenced unconfined groundwater ecosystems. A fundamental shift in taxa was seen with an overrepresentation of Rhodospirillales, Rhodocyclales, Chlorobia and Circovirus in the unconfined aquifer, while Deltaproteobacteria and Clostridiales were overrepresented in the confined aquifer. A relative overrepresentation of metabolic processes including antibiotic resistance (β-lactamase genes), lactose and glucose utilization and DNA replication were observed in the unconfined aquifer, while flagella production, phosphate metabolism and starch uptake pathways were all overrepresented in the confined aquifer. These differences were likely driven by differences in the nutrient status and extent of exposure to contaminants of the two groundwater systems. However, when compared with freshwater, ocean, sediment and animal gut metagenomes, the unconfined and confined aquifers were taxonomically and metabolically more similar to each other than to any other environment. This suggests that intrinsic features of groundwater ecosystems, including low oxygen levels and a lack of sunlight, have provided specific niches for evolution to create unique microbial communities. Obtaining a broader understanding of the structure and function of microbial communities inhabiting different groundwater systems is particularly important given the increased need for managing groundwater reserves of potable water.     

Understanding the Groundwater Hydrology of a Geographically-Isolated Prairie Fen: Implications for Conservation

The sources of water and corresponding delivery mechanisms to groundwater-fed fens are not well understood due to the multi-scale geo-morphologic variability of the glacial landscape in which they occur. This lack of understanding limits the ability to effectively conserve these systems and the ecosystem services they provide, including biodiversity and water provisioning. While fens tend to occur in clusters around regional groundwater mounds, Ives Road Fen in southern Michigan is an example of a geographically-isolated fen. In this paper, we apply a multi-scale groundwater modeling approach to understand the groundwater sources for Ives Road fen. We apply Transition Probability geo-statistics on more than 3000 well logs from a state-wide water well database to characterize the complex geology using conditional simulations. We subsequently implement a 3-dimensional reverse particle tracking to delineate groundwater contribution areas to the fen. The fen receives water from multiple sources: local recharge, regional recharge from an extensive till plain, a regional groundwater mound, and a nearby pond. The regional sources deliver water through a tortuous, 3-dimensional “pipeline” consisting of a confined aquifer lying beneath an extensive clay layer. Water in this pipeline reaches the fen by upwelling through openings in the clay layer. The pipeline connects the geographically-isolated fen to the same regional mound that provides water to other fen clusters in southern Michigan. The major implication of these findings is that fen conservation efforts must be expanded from focusing on individual fens and their immediate surroundings, to studying the much larger and inter-connected hydrologic network that sustains multiple fens.     

Distribution of plasmids in groundwater bacteria

Summary Bacteria isolated from groundwater aquifer core materials of pristine aquifers at Lula and Pickett, OK, and from a site with a history of aromatic hydrocarbon contamination and natural renovation located at Conroe, TX, were screened for the presence of plasmid DNA by alkaline or enzyme lysis and agarose gel techniques. Some of the isolates were also subjected to taxonomic tests in addition to screening for resistance to antibiotics, tolerance to heavy metal salts, and bacteriocin production. There was no significant difference in the distribution of the traits usually associated with plasmid occurrence in isolates from the three sites. These traits, which occurred at low frequencies, were not restricted to plasmid-bearing strains of the communities. Plasmids were found in isolates from all three sites, but on the average there was a significantly higher percentage of isolates containing plasmids in the samples from Conroe (19.4%) than from either Lula (1.8%) or Pickett (7.7%). The sizes of the plasmids found ranged between 3.5 and 202 kilobases but, for the Conroe samples, many more isolates (67%) contained smaller plasmids (<10 kb) rather than larger ones. No plasmids were found in bacteria recovered from naturally renovated aquifer material at the Conroe site.     

Flooding forested groundwater recharge areas modifies microbial communities from top soil to groundwater table

Subsurface microorganisms are crucial for contaminant degradation and maintenance of groundwater quality. This study investigates the microbial biomass and community composition [by phospholipid fatty acids (PLFAs)], as well as physical and chemical soil characteristics at woodland flooding sites of an artificial groundwater recharge system used for drinking water production. Vertical soil profiles to c . 4 m at two watered and one nonwatered site were analyzed. The microbial biomass was equal in watered and nonwatered sites, and considerable fractions (25–42%) were located in 40–340 cm depth. The microbial community structure differed significantly between watered and nonwatered sites, predominantly below 100 cm depth. Proportions of the bacterial PLFAs 16:1ω5, 16:1ω7, cy17:0 and 18:1ω9t, and the long-chained PLFAs 22:1ω9 and 24:1ω9 were more prominent at the watered sites, whereas branched, saturated PLFAs (iso/anteiso) dominated at the nonwatered site. PLFA community indices indicated stress response ( trans / cis ratio), higher nutrient availability (unsaturation index) and changes in membrane fluidity (iso/anteiso ratio) due to flooding. In conclusion, water recharge processes led to nutrient input and altered environmental conditions, which resulted in a highly active and adapted microbial community residing in the vadose zone that effectively degraded organic compounds.     

The application of bacteriophage as tracers of chalk aquifer systems

Three tracer experiments were performed at two chalk groundwater sites. In the first experiment three bacteriophage were injected at three different depths within a chalk aquifer, 16.5 m from the pumping well. Two of the bacteriophage were recovered from the abstraction point giving a fastest migration rate of between 17 and 34.5 cm/h. One of the bacteriophage tracers, however, was not detected. In the second experiment, three bacteriophage were injected at different depths within a second chalk aquifer site, 1 km distance from the pumping well. A small percentage of original inoculum (0.055 and 0.002%) of two of the bacteriophage traversed the 1 km distance and was detected within 6 months, demonstrating a fastest migration rate of 30 and 29.5 cm/h. At the same site, two bacteriophage were injected into a different borehole, 50 m away from the pumping well. Neither of the two bacteriophage were recovered from the abstraction point. These bacteriophage tracer experiments expose several interesting hydrogeological features about each chalk aquifer system and re-assert bacteriophage as excellent tracers at groundwater sites.     

高寒内陆河流域植被覆盖增加对地下水补给的影响

地下水是干旱区内陆河流域的主要基础性资源,对流域生态安全、可持续发展等具有重要意义。干旱/半干旱区的地下水补给比湿润地区更易受到地表覆盖条件的影响。为揭示干旱区内陆河流域植被覆盖增加对地下水补给的影响,以巴音河中下游为例,针对土壤和水评价工具(SWAT)模型未有效考虑降水、地形等因素对植被覆盖影响的缺陷,改进SWAT模型,采用全球地表卫星叶面积指数(GLASS LAI)数据代替其LAI计算模块,再结合SWAT土地利用更新模块,准确刻画区域植被覆盖变化。将改进后的SWAT模型与模块化有限拆分地下水流耦合(MODFLOW)模型耦合,准确模拟并分析植被覆盖增加对流域地下水补给的影响。结果表明：基于植被动态变化的土壤和水评价工具与模块化有限拆分地下水流耦合模型(DVSWAT-MODFLOW)模型的月蒸散发及月地下水位模拟效果较好;巴音河中下游2019年林地及草地面积以及LAI较2001年明显增加;2019年植被覆盖情况对应的年际及月际尺度地下水补给量较2001年分别减少了6.1—26.52 mm以及0—15.03 mm;植被覆盖增加对年际尺度地下水补给量的影响强弱在一定程度上取决于年降水量,对...     

Watershed Conservation in the Long Run

We studied unanticipated long-run outcomes of conservation activities that occurred in forested watersheds on O`ahu, Hawaii, in the early twentieth century. The initial general impetus for the conservation activities was to improve irrigation surface water flow for the sugar industry. Industry concentration facilitated conservation of entire ecosystems. We investigate the benefits that accrued through dynamic linkages of the hydrological cycle and groundwater aquifer system. This provides a clear example of the need to consider integrated watershed effects, industrial structure, and linkages in determining conservation policy. We incorporated remote-sensing data, expert opinion on current watershed quality, and a spatial economic and hydrological model of O`ahu’s freshwater use with reports of conservation activities from 1910–1960 to assess these benefits. We find a 2.3% annual increase in groundwater recharge levels from these activities, with a lower bound benefit–cost ratio of 7.1–18.2. This lower-bound excludes returns from such high value, yet controversial to measure, amenities as species preservation.     

Groundwater discharge from the superficial aquifer into Cockburn Sound Western Australia: estimation by inshore water balance

Submarine groundwater discharge (SGD) into Cockburn Sound Western Australia was quantified by applying a distributed groundwater flow model to estimate the inshore aquifer water balance. Spatially averaged SGD along the coast was estimated to be 2.5–4.8?±?0.9?m³?day^?1?m^?1. The range in estimated average SGD reflected low and high estimates of average groundwater recharge, which ranged from 0.13 to 0.24?m?year^?1 (15–28% of average annual rainfall). The error ±0.9?m³?day^?1?m^?1 was calculated by assuming arbitrary ±20% errors in groundwater pumping and inflow across boundaries. SGD varied spatially along the coastal boundary due to variation in hydraulic connection between the coastal aquifers and ocean, and spatial variability in recharge, transmissivity and pumping. Under assumptions of low and high groundwater recharge, SGD along the coastline varied in the ranges 1.4–4.6?m³?day^?1?m^?1 and 2.4–7.9?m³?day^?1?m^?1, respectively.