Subsurface Water Samples Research Articles

Groundwater quality assessment for drinking and irrigation purposes and its human health risks in the Sevathur mine region, south India

In this research, 35 samples of groundwater were collected and subjected to analysis with the aim of assessing its appropriateness for both drinking and irrigation purposes in Sevathur mine region, south India. Spatial depiction illustrates the widespread dispersal of primary positively charged ions and negatively charged ions formulated through the Inverse Distance Weighting (IDW) technique within a Geographic Information System (GIS). The Piper and Gibbs plots reveal a variety of water compositions in the surveyed region, encompassing combinations of mixed Ca-Mg-Cl, Ca-Mg-Cl-SO4, Na-K-Cl-SO4, and a few instances falling within the category of Ca-Mg-HCO3. The current features of hydrogeochemical facies result from the interplay between geological formations and water, alongside the occurrence of ion exchange, dissolution and weathering of calcium carbonate, calc-silicate minerals, and halite within subterranean aquifers. The water quality index unveiled that 23 % of the samples fall into the poor category, while a substantial 11 % are categorized as very poor. Additionally, 3 % are undesirable, 17 % are unfit for drinking, 23 % exhibit a good, and 23 % are distinguished by excellent categories. SAR values of subsurface water samples belong to the excellent class. Additionally, the RSC value indicates that 94 % of the samples are categorized as suitable class, while 6 % are classified as marginal for irrigation purposes. Individuals are advised to avoid drinking groundwater with fluoride levels above the WHO limit (>1.5 mg/l), as 26 % of samples exceeded this threshold. The region's groundwater chemistry is influenced by natural geological processes, such as mineral dissolution, and ion exchange, as well as human activities, including agricultural practices. Advanced water treatment techniques are being considered to improve water quality and ensure safer drinking water for the community.

Palatability Assessment of Subsurface Water in South India: An Experimental and Numerical Study

Monitoring the quality of groundwater is crucial and important for the environment, the human health and agriculture practices. This study focused on evaluating the physical and chemical characteristics of subsurface water of different selected places in Coimbatore. This study was also aimed for identifying the influence of sampling location to its characteristics. Twenty-five subsurface water samples were taken from distinct places and sources. The tests were conducted as per Indian standards. The findings indicate that temperature, available and residual chlorine, and pH are nearly identical for all groundwater samples; turbidity, electrical conductivity, total dissolved solids, sulphates and iron change significantly depending on where the source was located. To determine the appropriateness of ground water samples for drinking purposes, findings were compared with Indian (IS 10500:2012) and WHO (2006) standards. It was determined that results for all parameters are within the acceptable limit. The statistical analysis was conducted using SPSS software to know the significance of the predicted results and it has been found that the results were statistically significant.

Evaluation of Groundwater Chemistry and Multivariate Statistical Studies in Parts of Tirupur District, India

Groundwater quality at any location depends on the mutual possessions of several progressions beside the subsurface flow path. The natural history and degree of infectivity in a particular region can be ascertained by hydro-chemical statistics. In order to assess the groundwater chemistry and its appropriateness for consumption purposes, sixty-three subsurface water samples were analyzed. Based on the perceptive of the hydro-geological and groundwater environment, the chemical characteristics of the groundwater were evaluated. The favored parameters for the quality assessment were major anions and cations along with pH, turbidity, total dissolved solids, total hardness, fluoride and iron as trace metals. Total dissolved solids distribution, hydro-chemical facies, Piper diagram, factor analysis, correlation studies and cluster analysis were done to monitor the study zone. The total dissolved solids (TDS) were clustered independently. It was concluded from the assessment that the groundwater of the Tirupur region was critically deteriorated by different anthropogenic activities.

Seasonal and spatial variability of CO2 emissions in a large tropical mangrove‐dominated delta

AbstractThis study quantified the seasonal and spatial variability of partial pressure of CO2 (pCO2) and water‐atmosphere CO2 fluxes in the Parnaíba River Delta, the largest delta in the Americas. It is a pristine equatorial, mangrove‐dominated environment located in a transitional between humid and semi‐arid climates, with marked seasonality in rainfall and river discharge. Major channels and bays were sampled during dry and wet seasons, with continuous measurements of pCO2, temperature, salinity, and wind velocity. Subsurface water samples were collected in discrete stations for pH, total alkalinity (TA), dissolved inorganic carbon (DIC), dissolved oxygen and chlorophyll a quantification. A significant positive correlation between carbonate system parameters with salinity was found in both periods, with salinity significantly higher in the dry season. Strong deviations of pCO2, TA, and DIC from two endmembers conservative mixing were found, particularly in mangrove‐dominated waters, due to organic matter degradation. The Delta showed high spatial variability of pCO2, with the highest values in mangrove‐dominated waters, moderate in the river‐dominated regions, and lowest in the high salinity areas, suggesting that pCO2 variability is likely controlled by a combination of river‐ocean mixing and biological processes (respiration and photosynthesis). The Delta outgasses about 20 times less CO2 in the dry season (9.06 ± 11.09 mmol m−2.d−1) than in the rainy season (209.68 ± 250.87 mmol m−2 d−1). Our results indicate this large mangrove‐dominated tropical delta is an important source of CO2 to the atmosphere, but a sharp decrease was observed during dry periods.

Hydrogeochemical Characteristics of Geothermal Water in Ancient Deeply Buried Hills in the Northern Jizhong Depression, Bohai Bay Basin, China

The Jizhong Depression boasts rich geothermal resources with a lengthy history of geothermal exploitation. Buried hill geothermal reservoirs, which serve as primary thermal sources for hydrothermal resource exploitation, are prevalent in this region and have advantages such as extensive development potential, significant geothermal reservoir capacity, superior water quality, and straightforward recharge. This study investigates the formation and evolution of deep geothermal water in the Jizhong Depression by analyzing the hydrochemical and isotopic data of geothermal water samples collected from buried hill geothermal reservoirs in the northern part of the depression. The findings reveal that the subsurface hot water samples from the carbonate geothermal reservoirs in this region were predominantly weakly alkaline water with a pH ranging between 6.61 and 8.87. The hot water samples collected at the wellhead exhibited temperatures varying from 33.9 °C to 123.4 °C and total dissolved solids (TDS) lying between 473.9 mg/L and 3452 mg/L. Based on the δ2H-δ18O stable isotope analysis, the geothermal fluids in the Jizhong Depression are predominantly sourced from atmospheric precipitation and exist in a somewhat isolated hydrogeological environment, exhibiting pronounced water–rock interactions and deep water circulation (with depths ranging from 1324 m to 3455 m). Through a comparison of various methods, it is deduced that the most appropriate geothermometer for deep karst geothermal reservoirs in the Jizhong Depression is a chalcedony geothermometer, and when using it, the deep reservoir temperature was estimated at 63–137.6 °C. The precipitation in the adjacent mountainous areas enables the groundwater to infiltrate and descend deep into the earth along piedmont faults. Subsequently, lateral runoff over extended periods replenishes the groundwater into the depression. This process allows for the groundwater to fully absorb heat from deep heat sources, resulting in the formation of the deep geothermal reservoirs in the northern Jizhong Depression. The insights obtained from this study offer a theoretical and scientific foundation for the exploitation and utilization of regional geothermal resources and the transformation of the energy structure in China.

A Pioneering Assessment on the Physico-chemical and Health Status of a Small Sub-tropical Reservoir in North-Eastern, India

Background: The water resources of Northeast (NE) Indian reservoirs have been largely overlooked, despite their immense potential in various aspects. A comprehensive analysis of water quality parameters was conducted to assess the physio-chemical changes and health status of Maphou or Mapithel reservoir, Manipur, NE, India. Methods: Sub-surface water samples were collected from June 2021 to May 2022 to assess the spatio-temporal changes. Trophic State Index (TSI), Morpho Edaphic Index (MEI), Maximum Sustainable Yield (MSY) and fish yield potential were calculated. The average water spread area was calculated through Normalised Difference Water Index (NDWI) method. Result: A total of eighteen (18) water quality parameters were examined following Standard Methods. ANOVA analysis indicated that all water quality parameters, except total alkalinity, exhibited significant seasonal variations (p less than 0.05). Spatially, most of the water quality was found to be insignificant, except for Chl-a and depth (p less than 0.05). All the water quality parameters were within acceptable ranges for the growth and survival of aquatic biotic resources. No signs of pollution were observed. The trophic status of the reservoir was found in an oligotrophic state. The MEI was estimated as 8.55 and the average fish yield for the reservoir was 14.98 kg ha-1, which is below the national average yield of small reservoir (49.9 kg ha-1). The MSY was estimated to be 21.46 kg ha-1. Heatmap cluster analysis revealed three distinct clusters of months. The actual average water spread area was determined to be 852.62 ha, hence the reservoir can be categorised as small reservoir.

Microplastics in the Arctic: a transect through the Barents Sea

Globally, the abundance of microplastics in our oceans is increasing, including within the remote locations of the polar regions. The Barents Sea, which adjoins the Arctic Ocean, is an area of high primary productivity that, owing to the convergence of regional currents, has been mooted as a potential sixth ocean gyre that may coalesce high concentrations of plastic debris. This study aimed to explore data collected from large volume samples of sub-surface water collected from transects through the Barents Sea to quantify and characterise microplastics in this region, with a focus on potential impacts to zooplankton. Overall, the mean microplastic abundance in the Barents Sea was 0.011 microplastics m-3 (range: 0.007 – 0.015 m-3). Microplastics were found in higher abundances nearer land mass at the southern end of the transect and northwards towards the ice edge, recording 0.015 microplastics m-3 during both transect legs. Microplastics were predominantly fibrous (92.1%) and typically blue (79%) or red (17%) in colour. A range of polymers were identified including polyester (3.8%), copolymer blends (2.7%), elastomers (7.1%) and acrylics (10.6%), however semi-synthetic polymers dominated, comprising 74.4% of particles found. Higher microplastic concentrations in the northernmost transect may stem from melting sea-ice, while the higher concentrations in the southernmost transect likely derive from the long-range transport of microplastics via currents from Europe.

Seasonal Fluctuation of Nutrients and Primary Productivity of the Coastal Waters of Culaman, Malita, Davao Occidental

The study was conducted to determine the nutrient and chlorophyll-a concentration of coastal water at Barangay Culaman, Malita, Davao Occidental between two seasons. One shot sampling was done during the rainy season on November 19, 2017, and November 26, 2017. It was also done during summer season on March 6, 2018, and March 11, 2018. Water samples were collected in the surface (5-10 cm depth) and subsurface (below 1m depth). Nutrients were analyzed in terms of their concentration expressed in mg/L, including ammonia, nitrate, nitrite, and phosphate. Chlorophyll-a was included being the most reliable index of primary productivity in seawater. Nitrate, nitrite, phosphate, and chlorophyll-a showed high concentration during rainy season while ammonia exhibited a high concentration during summer season. Further, nutrients were found in high concentrations from surface water compared to those from subsurface water. There were no significant differences in nutrient and chlorophyll-a concentrations between stations except for nitrate. In terms of its concentration between rainy and summer season, and between surface and subsurface waters, there were no significant differences in ammonia, nitrate, and phosphate. However, significant differences in the concentrations of nitrite and chlorophyll-a between rainy and summer season and between surface and subsurface water samples were observed. The prevailing levels of temperature, salinity, dissolved oxygen, and turbidity observed during sampling were found to be normal.

Analysis of Groundwater Quality In Areas Surrounding Mining Sites In Kolaka Regency

This rearch was conducted around mining sites is Pomalaa district, Kolaka. Nickel mining activities have an impact on water pollution which can reduce water quality in both rivers and groundwater. The decrease in water quality around the mining area can be caused by the flow of runoff from rainwater which carries soil particles to water bodies which makes the water cloudy and may contain heavy metals. This study aims to determine the quality of the soil around the mining area of ​​Pomalaa District. Sampling of surface water and subsurface water was carried out using the purposive sampling method. The Pollution Index method is used to analyze the level of water pollution. The results of the analysis show that mining activities in the study area do not have a significant impact on decreasing air quality even though some hazardous metal elements are found such as Arsenic (Ar), Khomium VI (Cr+6), Iron , Cadmium, Copper (Cu) and Lead (Pb). The dominant influence is the high content of BOD and DO in the waters which makes several locations of minor occurrences according to the calculation of indexing calculations. Geological factors that play a role in decreasing air quality are morphological, lithological and structura

Anthropogenic impact and antibiotic resistance among the indicator and pathogenic bacteria from several industrial and sewage discharge points along the coast from Pydibhimavaram to Tuni, East Coast of India

Increasing urbanisation and industrialisation of the Visakhapatnam region have brought domestic sewage and industrial wastewater discharge into the coastal ocean. This study examines the indicator and pathogenic bacteria's quantitative abundance and antibiotic susceptibility. This study collected surface and subsurface water samples from ten different regions (147 stations; 294 samples), including 12 industrial discharge points, surrounding stations and two harbours from the coast of Pydibheemavaram to Tuni. Physicochemical parameters like salinity, temperature, fluorescence, pH, total suspended matter, nutrients, chlorophyll-a and dissolved oxygen showed a difference between regions. We noticed the presence of indicator (Escherichia coli and Enterococcus faecalis) and pathogenic (Aeromonas hydrophila, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella and Shigella, Vibrio cholera and Vibrio parahaemolyticus) bacteria among the samples. Waters from the near harbour and Visakhapatnam steel plant showed lower bacterial load with no direct input from industries to the coastal water. Samples collected during the industrial discharge period had a higher bacterial load, including E. coli. Enteric bacteria were found in higher numbers at most stations. Some isolates were resistant to multiple antibiotics with higher antibiotic resistance and multiple antibiotic resistance indexes compared with the other coastal water habitats in the Bay of Bengal. The occurrence of these bacteria above the standard limits and with multiple antibiotic resistance in the study region may pose a potential threat to the local inhabitants. It can create an alarming situation in the coastal waters in the study region.

Contributions from the main river of the largest open sea delta in the Americas to the CO2 fluxes

In this study, we sampled for the first time the main channel of the Parnaíba Delta, the largest open sea delta in the Americas, and two of its secondary channels, during the rainy season. Continuous measurements of pCO 2, temperature, salinity, and wind velocity were taken, while subsurface water samples were collected to analyze for dissolved oxygen, pH, total alkalinity, dissolved organic carbon, and its isotopic, chlorophyll-a, and nutrients. The spatial variability of pCO 2 along the different channels showed the existence of distinct drivers of CO2 dynamics in the area. The correlation of pCO 2 in freshwater samples with dissolved oxygen and chlorophyll-a indicated the incidence of organic matter decomposition and primary production in the main channel and mangroves, while the highest salinity samples evidenced the control of carbonate equilibrium in the river mouth. Our data also indicated an important influence of the river discharge on the carbon dynamics of the estuary, with around 73% of the CO2 emissions in the estuary estimated to be from riverine CO2. The strong river effect in the estuary was also supported by the low salinities (0.04–26.37), pH (7.09 ± 0.36), and total alkalinity (328 ± 530.46 μmol kg −1), typical from fluvial waters. The estuary was supersaturated in CO2 and behaved as a strong source, with an average flux of 194.1 ± 135.1 mmol m−2 d−1.

In situ digital holographic microscopy for rapid detection and monitoring of the harmful dinoflagellate, Karenia brevis

Karenia brevis blooms, also known as red tide, are a recurring problem in the coastal Gulf of Mexico. These blooms have the capacity to inflict substantial damage to human and animal health as well as local economies. Thus, monitoring and detection of K. brevis blooms at all life stages and cell concentrations is essential for ensuring public safety. Current K. brevis monitoring methods have several limitations, including size resolution limits and concentration ranges, limited capacity for spatial and temporal profiling, and/or small sample volume processing. Here, a novel monitoring method wherein an autonomous digital holographic imaging microscope (AUTOHOLO), that overcomes these limitations and can characterize K. brevis concentrations in situ, is presented. Using the AUTOHOLO, in situ field measurements were conducted in the coastal Gulf of Mexico during an active K. brevis bloom over the 2020–21 winter season. Surface and sub-surface water samples collected during these field studies were also analyzed in the lab using benchtop holographic imaging and flow cytometry for validation. A convolutional neural network was trained for automated classification of K. brevis at all concentration ranges. The network was validated with manual counts and flow cytometry, yielding a 90% accuracy across diverse datasets with varying K. brevis concentrations. The usefulness of pairing the AUTOHOLO with a towing system was also demonstrated for characterizing particle abundance over large spatial distances, which could potentially facilitate characterization of spatial distributions of K. brevis during bloom events. Future applications of the AUTOHOLO can include integration into existing HAB monitoring networks to enhance detection capabilities for K. brevis in aquatic environments around the world.

Dynamics, distribution, and transformations of mercury species from pyrenean high-altitude lakes

While mercury (Hg) is a major concern in all aquatic environments because of its methylation and biomagnification pathways, very few studies consider Hg cycling in remote alpine lakes which are sensitive ecosystems. Nineteen high-altitude pristine lakes from Western/Central Pyrenees were investigated on both northern (France) and southern (Spain) slopes (1620–2600 m asl.). Subsurface water samples were collected in June 2017/2018/2019 and October 2017/2018 for Hg speciation analysis of inorganic mercury (iHg(II)), monomethylmercury (MMHg), and dissolved gaseous mercury (DGM) to investigate spatial and seasonal variations. In June 2018/2019 and October 2018, more comprehensive studies were performed in four lakes by taking water column depth profiles. Besides, in-situ incubation experiments using isotopically enriched Hg species (199iHg(II), 201MMHg) were conducted to investigate Hg transformation mechanisms in the water column. While iHg(II) (0.08–1.10 ng L−1 in filtered samples; 0.11–1.19 ng L−1 in unfiltered samples) did not show significant seasonal variations in the subsurface water samples, MMHg (<0.03–0.035 ng L−1 in filtered samples; <0.03–0.062 ng L−1 in unfiltered samples) was significantly higher in October 2018, mainly because of in-situ methylation. DGM (0.02–0.68 ng L−1) varies strongly and can exhibit higher levels in comparison with other pristine areas. Depth profiles and incubation experiments highlighted the importance of in-situ biotic methylation triggered by anoxic conditions in bottom waters. In-situ incubations confirm that significant methylation, demethylation and photoreduction extents are taking place in the water columns. Overall, drastic environmental changes occurring daily and seasonally in alpine lakes are providing conditions that can both promote Hg methylation (stratified anoxic waters) and MMHg photodemethylation (intense UV light). In addition, light induced photoreduction is a major pathway controlling significant gaseous Hg evasion. Global warming and potential eutrophication may thus have direct implications on Hg turnover and MMHg burden in those remote ecosystems.

A Multivariable Empirical Algorithm for Estimating Particulate Organic Carbon Concentration in Marine Environments From Optical Backscattering and Chlorophyll-a Measurements

Accurate estimates of the oceanic particulate organic carbon concentration (POC) from optical measurements have remained challenging because interactions between light and natural assemblages of marine particles are complex, depending on particle concentration, composition, and size distribution. In particular, the applicability of a single relationship between POC and the spectral particulate backscattering coefficient bbp(λ) across diverse oceanic environments is subject to high uncertainties because of the variable nature of particulate assemblages. These relationships have nevertheless been widely used to estimate oceanic POC using, for example, in situ measurements of bbp from Biogeochemical (BGC)-Argo floats. Despite these challenges, such an in situbased approach to estimate POC remains scientifically attractive in view of the expanding global-scale observations with the BGC-Argo array of profiling floats equipped with optical sensors. In the current study, we describe an improved empirical approach to estimate POC which takes advantage of simultaneous measurements of bbp and chlorophyll-a fluorescence to better account for the effects of variable particle composition on the relationship between POC and bbp. We formulated multivariable regression models using a dataset of field measurements of POC, bbp, and chlorophyll-a concentration (Chla), including surface and subsurface water samples from the Atlantic, Pacific, Arctic, and Southern Oceans. The analysis of this dataset of diverse seawater samples demonstrates that the use of bbp and an additional independent variable related to particle composition involving both bbp and Chla leads to notable improvements in POC estimations compared with a typical univariate regression model based on bbp alone. These multivariable algorithms are expected to be particularly useful for estimating POC with measurements from autonomous BGC-Argo floats operating in diverse oceanic environments. We demonstrate example results from the multivariable algorithm applied to depth-resolved vertical measurements from BGC-Argo floats surveying the Labrador Sea.

Spatio-temporal variability of eDNA signal and its implication for fish monitoring in lakes.

Environmental DNA (eDNA) metabarcoding is revolutionizing the monitoring of aquatic biodiversity. The use of eDNA has the potential to enable non-invasive, cost-effective, time-efficient and high-sensitivity monitoring of fish assemblages. Although the capacity of eDNA metabarcoding to describe fish assemblages is recognised, research efforts are still needed to better assess the spatial and temporal variability of the eDNA signal and to ultimately design an optimal sampling strategy for eDNA monitoring. In this context, we sampled three different lakes (a dam reservoir, a shallow eutrophic lake and a deep oligotrophic lake) every 6 weeks for 1 year. We performed four types of sampling for each lake (integrative sampling of sub-surface water along transects on the left shore, the right shore and above the deepest zone, and point sampling in deeper layers near the lake bottom) to explore the spatial variability of the eDNA signal at the lake scale over a period of 1 year. A metabarcoding approach was applied to analyse the 92 eDNA samples in order to obtain fish species inventories which were compared with traditional fish monitoring methods (standardized gillnet samplings). Several species known to be present in these lakes were only detected by eDNA, confirming the higher sensitivity of this technique in comparison with gillnetting. The eDNA signal varied spatially, with shoreline samples being richer in species than the other samples. Furthermore, deep-water samplings appeared to be non-relevant for regularly mixed lakes, where the eDNA signal was homogeneously distributed. These results also demonstrate a clear temporal variability of the eDNA signal that seems to be related to species phenology, with most of the species detected in spring during the spawning period on shores, but also a peak of detection in winter for salmonid and coregonid species during their reproduction period. These results contribute to our understanding of the spatio-temporal distribution of eDNA in lakes and allow us to provide methodological recommendations regarding where and when to sample eDNA for fish monitoring in lakes.

Mapping the possible origin of anomalous saline water occurrence in Agbabu, Eastern Dahomey Basin, Nigeria: insights from geophysical and hydrochemical methods

Many researchers have suspected saltwater occurrence in Agbabu in the eastern Dahomey Basin. However, there is a need to get an insight to the possible origin of saltwater in the area. The aim of this study is to determine the source of saltwater in the inland aquifers of Agbabu, southwestern Nigeria for proper management of scarcely available freshwater resource in the area. 23 vertical electrical sounding, 2D electrical resistivity tomography (ERT), aeromagnetic and hydrochemical data (11 subsurface water samples) analyses were utilized in this study. The results from the magnetic analysis revealed the inland extension of the Chain Fracture Zone (CFZ). This NE-SW trending fracture zone cuts across the entire eastern Dahomey Basin, including Agbabu and its environs. Four (4) geoelectric layers were delineated across Agbabu namely, the topsoil (4 - 2806 Ωm), clayey sand (3 - 1280 Ωm), clayey (3 - 161 Ωm) and bituminous sand (1 - 10390 Ωm) layers. Anomalously low resistivity (1 - 20 Ωm) zones suspected within the bituminous sand correspond to the saltwater intrusion zones. The bituminous sand unit harbouring freshwater exhibits characteristic resistivity values of 33 – 160 Ωm. The interface between the freshwater and saltwater intruded zones in the area was suspected at 10 m depth with resistivity values ranging between 21 Ωm and 33 Ωm. The results from the hydrochemical water analysis also confirmed the presence of saltwater intrusion in the area. The salinity extent chart which was generated from the VES results indicated the mobility of the saltwater into the groundwater system. The fracture connectivity between the complex aquifers of Agbabu and the Atlantic Ocean (CFZ), that was mapped from the aeromagnetic and electrical resistivity results, is suspected to be primarily controlling the localization of saltwater in the study area.

Bacteria Community Vertical Distribution and Its Response Characteristics to Waste Degradation Degree in a Closed Landfill

The diversity, community structure and vertical distribution characteristics of bacteria in the surface and subsurface soil and water samples of a closed landfill in Shanghai Jiading District were investigated to reveal the relationships between natural waste degradation degree and the succession of bacterial community composition. High-throughput sequencing of bacteria 16S rDNA genes was used to analyze the bacterial community structure and diversity. The results showed that the diversity of bacteria in the surface samples was higher than that in the deep samples. Proteobacteria was the dominant phylum in all the samples, and the percentage increased with depth. At the genus level, Thiobacillus, Pseudomonas, Aquabacterium, and Hydrogenophaga were the dominant genera in surface, medium, deep and ultra-deep soils, respectively. The Bray–Curtis dissimilarity of the soil bacterial communities in the same layer was small, indicating that the community composition of the samples in the same layer was similar. The RDA result showed that ammonium, nitrate, pH and C/N significantly influenced the community structure of soil bacteria. This is of great relevance to understand the effect of natural waste degradation on bacterial communities in closed landfills.

Microplastic variability in subsurface water from the Arctic to Antarctica

Comparative investigations of microplastic (MP) occurrence in the global ocean are often hampered by the application of different methods. In this study, the same sampling and analytical approach was applied during five different cruises to investigate MP covering a route from the East-Siberian Sea in the Arctic, through the Atlantic, and into the Antarctic Peninsula. A total of 121 subsurface water samples were collected using underway pump-through system on two different vessels. This approach allowed subsurface MP (100 μm–5 mm) to be evaluated in five regions of the World Ocean (Antarctic, Central Atlantic, North Atlantic, Barents Sea and Siberian Arctic) and to assess regional differences in MP characteristics. The average abundance of MP for whole studied area was 0.7 ± 0.6 items/m3 (ranging from 0 to 2.6 items/m3), with an equal average abundance for both fragments and fibers (0.34 items/m3). Although no statistical difference was found for MP abundance between the studied regions. Differences were found between the size, morphology, polymer types and weight concentrations. The Central Atlantic and Barents Sea appeared to have more MP in terms of weight concentration (7–7.5 μg/m3) than the North Atlantic and Siberian Arctic (0.6 μg/m3). A comparison of MP characteristics between the two Hemispheres appears to indicate that MP in the Northern Hemisphere mostly originate from terrestrial input, while offshore industries play an important role as a source of MP in the Southern Hemisphere. The waters of the Northern Hemisphere were found to be more polluted by fibers than those of the Southern Hemisphere. The results presented here suggest that fibers can be transported by air and water over long distances from the source, while distribution of fragments is limited mainly to the water mass where the source is located.

Do phytoplankton and epiphyton communities differ between organic and conventional rice fields?

This study aimed to determine if there are any differences in the attributes and composition of the phytoplankton and epiphyton communities between organic (OF) and conventional (CF) rice fields. We also strove to identify if there were any variations in these communities by comparing samples taken from two different periods (12 and 35 days) after the application of the herbicide clomazone and penoxsulam in CF. The farms are located in the Pampa Biome, Southern Brazil. Phytoplankton samples from the subsurface water and epiphyton samples from the rice stems were analyzed using the Utermöhl method. The CF and OF had distinct environmental conditions (pH, conductivity, and turbidity values), and the residual concentration of the herbicides decreased over time. There were no significant differences in epiphyton and phytoplankton density, or in phytoplankton richness, between the rice fields; only the epiphyton richness and taxonomic composition showed differences between the rice fields. Cyanobacteria and Chlorophyceae comprised a large proportion of the epiphytic density in CF and OF, respectively. However, Bacillariophyceae and Chlorophyceae had greater phytoplankton densities in CF and OF, respectively. The taxonomic composition of communities should be considered an effective tool to show the differences between the two cultivation systems.

Hydrogeochemical Characterization of Groundwater Quality in Parts of Amroha District, Western Uttar Pradesh, India

The present work attempts to characterize groundwater quality and ascertain its suitability for drinking and agricultural practices using different indices. A total of 122 sub-surface water samples were collected from the Amroha district of Uttar Pradesh, India, in the pre and post-monsoon season 2018 (61 samples of each season). The quality of groundwater observed from the study region has a slightly acidic to alkaline character with moderately hard type water. The order of the dominant ions is Na+ > Ca2+ > Mg+ > K+ and HCO−3 > Cl− > SO42− > NO−3 > F− in the pre-monsoon season while Na+ > Mg+ > Ca2+ > K+ and HCO−3 > SO42− > Cl− > NO−3 > F− in the post-monsoon season. A few samples show a higher concentration of Nitrate and Fluoride. The correlation coefficient shows that EC is positively correlated with TDS, Cl−, Ca2+, Mg+, and Total Hardness. The WQI studies revealed that about 52.45%, 36.07%, and 11.48% samples denoted excellent, good, and poor water quality, respectively, in the pre-monsoon season. About 52.45%, 45.9%, 1.63% of groundwater samples fell under excellent, good, and poor water quality in the post-monsoon season. The Piper diagram depicts Ca–HCO3, mixed Ca-Na-HCO3, Na–Cl, and mixed Ca-Mg-Cl facies in the water samples. Chloro-alkaline indices show negative values, which indicates that most parts of the study area exist in the discharge zone and base ion exchange processes occurred in the area. The position of the sample on the Gibbs diagram revealed that the rock-water interaction and evaporation of dissolved formation are the major governing process of water chemistry. Irrigation water quality indices revealed that the water quality for irrigation uses is mainly excellent to permissible type. The result of the Corrosivity ratio shows that about 24.5% of groundwater of the study area can be transported only through PVC pipes.