Influence Water Quality Research Articles

Impacts of soil use and management on water quality in agricultural watersheds in Southern Brazil

AbstractWorldwide, agriculture is considered one of the main activities that influence water quality. The objective of this work was to evaluate the influence of soil use and management on water quality at the small watershed scale, in Southern Brazil. One watershed is characterized by production of annual crop seeds under no‐tillage (zero tillage), with crop rotation and with terraces (Sarandi watershed—SW), while the other is characterized by production of grains in the summer and pasture with grazing in the winter, under no‐tillage, without crop rotation and without terraces (Coxilha watershed—CW). Flow and climatic data were measured during 2 years. Water samples were manually taken at precipitation events and base flow over 1 year for laboratory analysis. During events of high volume, most of the rainfall was converted to base flow in SW, while in CW, most of the rainfall was transformed into overland flow. Overall, higher concentrations and losses of sediments and nutrients occurred in the CW, mainly during precipitation events in the winter crops season. Of the total nitrogen concentration in water, approximately 3% was ammonium‐N and 58% was nitrate‐N, on average, in both watersheds. For total phosphorus concentration in water, more than 75% was particulate in both watersheds, however, the bioavailable phosphorus accounted for 70% of the total phosphorus in the SW and for 35% in the CW. The higher concentration of bioavailable phosphorus in the SW indicates a short‐term pollution potential, but in both watersheds, the water quality was impaired by the high concentrations of total phosphorus. In general, even with no‐tillage, the results highlight the importance of best management practices as terracing, riparian vegetation, crop rotation, better crop systems and fertilizer management to avoid degradation of water resources.

Utilizing the TTOP model to understand spatial permafrost temperature variability in a High Arctic landscape, Cape Bounty, Nunavut, Canada

AbstractGround surface and permafrost temperatures in the High Arctic are often considered homogeneous especially when viewed at the scale of climate and environmental models. However, this is generally incorrect due to highly variable, topographically redistributed snow cover, which generates a substantial degree of ground thermal heterogeneity. The objective of this study is to describe and spatially model the variability in the ground thermal regime within the Cape Bounty Arctic Watershed Observatory (CBAWO), Nunavut, Canada, using the TTOP model, for current conditions in addition to a series of future climate change scenarios. While observed air temperature was mostly uniform, annual mean ground surface and permafrost temperatures across the paired watersheds were estimated to range between −3.8 to −13.8°C and −3.9 to −14°C, respectively, similar to the −5 to −15°C magnitude and range identified from boreholes across the High Arctic. The spatial models showed higher ground surface temperatures in topographic hollows (slope bases and stream channels), and lower temperatures in areas of topographic prominence (hilltops and plateaus) following the spatial pattern of snow accumulation and redistribution. Under projected climate change, the models predicted areas with the coldest permafrost to have the largest magnitude of warming (about 9°C), while areas of warm permafrost became closer to 0°C (warming 4–7°C). This thermal heterogeneity may have implications for ground instability such as permafrost‐related mass movements, hydrological connectivity, biogeochemical cycling, and microbial activity, which influence water quality and contaminant mobility.

Assessment of Industrial Influent and Effluent Water Quality at a Bottling Company in Aba, Abia State, Nigeria

his study assessed water sources (treated water, pond water and harvested rain water) and effluents discharge from a bottling company, Aba, Abia State. A single factor experiment in randomized complete block designs with three replications was used to assess the physicochemical properties of water at various sources. The result shows that pond water and rain water gave significantly the highest and least N and P contents respectively (N: 33.60-5.60 mg/L; P: 12.40-10.30 mg/L). The K contents of the various water point sources were significantly higher as follows: Pond water > Effluent water > Rain water > Treated water (6.50 > 0.30 > 0.20 > 0.20). Pond water was statistically highest in Mg contents when compared to other sources. The Fe contents were significantly higher as follows: Effluent water > Rain water > Treated water > Pond water, while Fe content in pond water wasn’t significantly higher when compared to its content in Rain water. Pond water and treated water were significantly the highest and least (P<0.05) in organic matter (OM) and Organic Carbon (OC) contents respectively. No significant differences existed between color intensity and turbidity values of the various water point sources. Effluent water from the industry and pond water were significantly the least in DO values respectively. Rain water and pond water were significantly the least in BOD concentrations. Effluent water was significantly the highest in TSS values, while the least TSS values were significantly recorded for Treated water and Rain water.

Effects of land cover, topography, and soil on stream water quality at multiple spatial and seasonal scales in a German lowland catchment

The influence of catchment characteristics on water quality varies with space and time. Understanding the key factors influencing water quality is needed for effective land use and riparian management to protect river health. To this end, we quantified effects on stream water quality in summer and winter between 1992 and 2019 at multiple spatial scales in the upper Stör catchment, Germany. We applied multivariate statistical analyses on three scales: the catchment, riparian, and reach scale. Our results indicated that poorer water quality mostly occurred in winter and in steeper arable and pasture areas and in wetlands. Water quality was strongly affected by soil properties, land use composition (the areal shares of arable or pasture land respectively with slopes >2%, forest, and urban) and configuration. The spatial variation of the overall water quality was better explained at the larger scales (riparian and catchment) and in summer (73–78%). The most important variables differed among scales and for the different water quality variables. Forest and complex landscape patterns showed more negative correlations with degraded water quality at the reach scale when compared to larger scales. At larger scales, besides permeable and organic soils, steeper arable lands were most significant for nitrate-nitrogen (NO3-N) and steeper pasture areas for phosphate-phosphorus (PO4-P) pollution. The results of this study provide valuable insights for guiding sustainable and spatially specific land-water management of river catchments at different scales to improve stream water quality.

Assessment of the quality of quaternary groundwater under the influence of anthropogenic activities in the low-income neighbourhoods of the Treichville municipality (Abidjan, Côte d’Ivoire)

This study aims to assess the groundwater quality and the origin of water mineralization in an environment with high anthropogenic pressure in the municipality of Treichville. Twenty-one water samples were analysed to determine the quality. Kruskal–Wallis nonparametric test, Mann–Whitney test, Kohonen algorithm, and water table building were used to determine the factors influencing the mineralization. The results showed that the well’s water contains chemical and bacteriological elements whose concentrations are higher than the standards authorized by the World Health Organization (WHO). Thus, high levels of nitrate (peak = 173.1 mg L−1), phosphate (peak = 1.03 mg L−1), lead (peak = 2.987 mg L−1), and Escherichia coli (peak = 2.31 × 105 UFC 100 mL−1) were obtained in these waters. So, the groundwater is not suitable for human consumption. The most mineralized waters are found in the areas near the Ebrie Lagoon and extend in the direction including the low-income neighbourhoods of Biafra, Nanan Yamousso and Appolo. Pollutant transfer is continuous in the study area and comes from surface sewage, latrines, sewage disposal systems, well water collection materials, and the Ebrie Lagoon. Indeed, the pollutants leave Biafra neighbourhoods where water is heavily polluted and the pollution is amplified by the presence of septic tanks and latrines located on the line of groundwater flow. The main factors influencing water quality are the lagoon water intrusion, the advection mechanism linked to the infiltration of surface water and the lateral migration of pollutants from septic tanks and latrines, and mechanism of dissolution of the clay component of the clayey–sandy layers.

Submarine groundwater discharge drives coastal water quality and nutrient budgets at small and large scales

Submarine groundwater discharge (SGD) can be a significant source of chemical pollutants from land to ocean. Here, we first estimated SGD using radium isotopes and related nutrient fluxes at the local scale in Jiaozhou Bay (JZB), a typical Chinese system that is experiencing rapid urban and industrial development. We then summarized SGD studies off China to assess the large-scale implications of SGD to nutrient budgets. In JZB, the location of contaminated nearshore waters revealed by an integrative water quality index (WQI) coincided with the SGD hotspots. The total (fresh and saline) SGD flux in JZB was estimated to be (0.64–1.67) × 107 m3/d or (2.12–5.59) cm/d based on 224Ra and 228Ra mass balance models. This was approximately 8 times the discharge rate of local rivers. By combining these JZB results with the literature data, we provide the first estimate of SGD and associated nutrient fluxes off China. The magnitude of SGD at the China-scale was (5.40–10.2) × 1012 m3/yr, accounting for 5–9% of the global SGD flux. SGD-derived nutrient fluxes summarized from ∼40 previous studies were one order of magnitude higher than riverine inputs. These nutrients fluxes from SGD contributed >50% of the total dissolved inorganic nitrogen (DIN), phosphorous (DIP) and silicate (DSi) inputs into Chinese coastal waters, which can explain about 60% of the phosphorus required by primary production. The mean DIN/DIP ratio (121) in SGD was significantly higher than the Redfield ratio, with important implications for phytoplankton growth and structure. SGD can influence water quality, dominate nutrient budgets, and drive primary production not only at the local scale, but also at the regional and global scales.

Restoring tropical coastal wetland water quality: ecosystem service provisioning by a native freshwater bivalve

Freshwater bivalves can influence water quality by reducing phytoplankton levels through filter-feeding and altering nutrient levels through excretion and biodeposition. In northeast Australia, native freshwater bivalves (Corbicula australis) may help restore the water quality of coastal wetlands that receive high nutrient loads in runoff from nearby agricultural activity. We investigated the biofiltration and biodeposition capacity of C. australis and discuss their potential to provide an ecosystem service benefit of improved water quality to the Great Barrier Reef (GBR). The filtration and biodeposition rates of C. australis were measured in natural and artificial wetlands across: (1) the population’s size range; and (2) the temperature range of the wetlands they inhabit. High frequency water temperature loggers were deployed in wetlands throughout the year to determine water column temperature seasonality, population densities were measured to scale from individuals to ecosystem service provisioning potential. Bivalve filtration and biodeposition were quantified by measuring the rates of chlorophyll a removal and nutrient biodeposition, respectively. Biofiltration rates did not increase with size or differ between natural and artificial wetlands. In contrast, size was positively related to phosphorus (P) and nitrogen (N) biodepsoition rates, and N biodeposition rates differed between natural and artificial wetlands. Our results also suggest that biofiltration and biodeposition capacity of C. australis may be limited in high water temperatures only experienced in summer months. Overall, we demonstrate the importance of size, population density, and environmental context (i.e. wetland type and season) for the filtering capacity and biodeposition rate of C. australis. Larger individuals and denser populations mean that filtration and biodeposition rates are likely to be higher in artificial wetlands and may lead to greater processing of nutrient rich water.

Climate Change-Induced Changes in the Chemistry of a High-Altitude Mountain Lake in the Central Alps

Mountains are among the most sensitive ecosystems to climate change, and one of the most evident signs of climate-related effect is the continuous net loss of ice from the cryosphere. Several studies showed that meltwater from glaciated and perennially frozen areas can profoundly affect alpine aquatic ecosystems. Here, we present the impressive temporal increase in solutes in Lake Leit, a mountain lake in the Central Alps that is impacted by an active rock glacier. During the last 30 years, concentrations of sulfate and base cations increased by factors of 4 and 3, respectively. Atmospheric deposition, the only catchment external source, could be excluded as possible cause. The inlets have sulfate and base cations concentrations that were up to double the concentrations of the lake outlet confirming the presence of catchment internal sources. The highest concentrations were measured in the springs at the bottom of the rock glacier. Ground surface temperatures of the rock glacier indicated a high probability of permafrost occurrence, while the annual mean air temperature after the mid-1980s showed continuously positive deviations from the long-term average values (period 1961–1990) with increasing values after 2010. δ34S of sulfate in the inlets and the outflow indicated that sulfate in Lake Leit mainly derived from dissolution of gypsum/anhydrite even if its presence is not confirmed by the Geologic Atlas of Switzerland. Because of these results, we postulate the presence of subsurface traces of sulfate-bearing evaporites, probably associated with Triassic metasediments. These deposits are very common in the closer surroundings. We further hypothesize that the thawing of permafrost affects the flow path of water enabling its contact with fresh highly weatherable minerals increasing the overall weathering rate and shifting the relative ionic composition in the discharge toward the ions that originate from the most soluble minerals. This study shows that increased permafrost thawing in the future can influence water quality in high-alpine settings.

A spatiotemporal analysis of water quality characteristics in the Klip river catchment, South Africa.

Understanding the spatial and temporal patterns of water quality is central to its management as it provides information essential to the restoration as well as protection of water resources. The main objectives of this study were (i) to analyze the spatial and temporal trends of water quality and (ii) to identify the critical sources of pollution in the Klip River catchment (KRC). Water samples were collected at 12 sampling points along the Klip River, monthly from February 2016 to January 2017 and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and spectrophotometry for heavy metals and nutrients, respectively. Multivariate statistical techniques (cluster analysis and discriminant analysis) were used to delineate homogeneous water quality zones and seasons, and principal component analysis was used to identify pollution sources. Comprehensive pollution index (CPI) was also computed to classify the overall pollution of the river. The spatial grouping yielded two homogenous water quality zones namely upstream and downstream. Temporal grouping yielded two clusters, which were attributed to the effects of the El Nino (2015/16 season) and La Nina phenomena (2016/17 season). The CPI revealed that the KRC was critically polluted in the upstream for domestic (162.16-323.28) and aquatic uses (617.70-837.09) in both the 2015/2016 and 2016/2017 seasons. It can be concluded that pollutants, which influence water quality in the KRC in one season and/or location, may not necessarily be the same in the other season or location. Therefore, there is need to develop a water quality management plan in the KRC that targets the most impaired uses, pollutants of priority, and the critically polluted areas.

Azomite Application Does Not Positively Influence Water Quality, Phytoplankton Populations, or Zooplankton Populations When Preparing Mississippi Channel Catfish Nursery Ponds for Stocking

AbstractAzomite is a hydrated sodium calcium alumina silicate that is mined from a volcanic deposit in Utah. The product contains many micronutrients that may be beneficial in preparing catfish nursery ponds for stocking. In northwest Mississippi, a 5‐week study was conducted to compare water quality, phytoplankton populations, and zooplankton populations in Channel Catfish Ictalurus punctatus nursery ponds treated with Azomite at 0, 50, or 100 kg/ha. The study was conducted in 0.04‐ha ponds during April, when fry ponds are prepared for stocking. Azomite application did not affect ammonia concentrations. Over time, nitrite concentrations increased more in control ponds compared to Azomite‐treated ponds; however, nitrite concentrations were low in all ponds. Chlorophyll‐a concentrations were also unaffected by Azomite application. The pH did significantly increase with increasing Azomite application rate. Azomite application had no effects on phytoplankton or zooplankton populations. Overall, there were no beneficial effects of adding Azomite to Channel Catfish nursery ponds in northwest Mississippi.

Water quality trends under rapid agricultural expansion and enhanced in-stream interception in a hilly watershed of Eastern China

Conflicts between agricultural intensification and the increasing demand for clean water resources are growing worldwide. This study sought to understand how the negative consequences of agricultural expansion in fragile hilly watersheds can be mitigated by ecologically based engineering practices. We analyzed long-term and seasonal water quality trends in two sub-watersheds of the Tianmu Lake watershed in Eastern China. The Zhongtian and nearby Zhucao sub-watersheds are very similar in terms of climate, topography and other features that can influence water quality. Both are experiencing rapid expansion of tea plantations, but the Zhongtian River contains an engineered system of overflow dams and cascade wetlands that is absent from the Zhucao River. The multi-year averaged reduction (2009–2018) of total nitrogen (TN) and total phosphorus (TP) from upstream to downstream reaches was 10%–15% greater in the engineered Zhongtian River compared to the non-engineered and free flowing Zhucao River, which has no interventions to reduce nutrient concentrations. Average annual reductions in TN, TP, and total suspended solids (SS) downstream of the engineered system reached 0.5%–4.0% of their multi-year averaged concentrations over this time interval. These reductions occurred despite a 2.3-fold expansion of tea plantation area in the engineered watershed, which contrasts with deteriorating water quality in the non-engineered watershed that had a 0.4-fold expansion of tea plantation area. Our results underscore the value of such engineered systems to improve water quality and help reconcile competing advantages of agricultural development and environmental protection in hilly watersheds, where there is limited in-stream processing of nutrients and the effects of human activities are substantial.

Control of primary disinfection in a drinking water treatment plant based on a fuzzy inference system

Drinking water treatment plants (DWTPs) have to be efficiently managed to produce safe water at all times, independently from variations of influent water quality. Artificial Intelligence techniques like fuzzy inference systems (FIS) can help in consolidating process knowledge accumulated through years of experience and improve the consistency and resiliency of decision-making in these facilities. The objective of this study was to develop an advanced control system for choosing the combined dose of sodium hypochlorite and chlorine dioxide at the primary disinfection step of a full-scale DWTP. To accomplish this, two FISs consisting of a feed-forward and feed-back control elements were developed. The models were integrated in an environmental decision support system (EDSS) that evaluates the disinfection by-products (DBPs) formation risk and proposes actions which can be verified and applied by treatment managers. Implementation of the EDSS at a full-scale DWTP of Barcelona was positively validated 85.5 % of the times, maintaining acceptable DBPs concentrations at the effluent. The presented methodology can be used at similar surface water DWTPs for developing control strategies to manage DBPs formation.

Integration of Submerged Aquatic Vegetation Motion Within Hydrodynamic Models

AbstractAquatic models used for both freshwater and marine systems frequently need to account for submerged aquatic vegetation (SAV) due to its influence on flow and water quality. Despite its importance, parameterizations are generally adopted that simplify feedbacks from SAV, such as canopy properties (e.g., considering the deflected vegetation height) and the bulk friction coefficient. This study reports the development of a fine‐scale non‐hydrostatic model that demonstrates the two‐way effects of SAV motion interaction with the flow. An object‐oriented approach is applied to capture the multiphase phenomena, whereby a leaf‐scale SAV model based on a discrete element method is combined with a flow dynamics model to resolve stresses from currents and waves. The model is verified through application to a laboratory‐scale seagrass bed. A force balance analysis revealed that leaf elasticity and buoyancy are the most significant components influencing the horizontal and vertical momentum equations, respectively. The sensitivity of canopy‐scale bulk friction coefficients to water depth, current speeds, and vegetation density of seagrass was explored. Deeper water was also shown to lead to a smaller decrease in vegetation height. The model approach can contribute to improving assessment of processes influencing water quality, sediment stabilization, carbon sequestration, and SAV restoration, thereby supporting an understanding of how waterways and coasts will respond to changes brought about by development and a changing climate.

Microbial community composition across a coastal hydrological system affected by submarine groundwater discharge (SGD).

Mobile Bay, the fourth largest estuary in the USA located in the northern Gulf of Mexico, is known for extreme hypoxia in the water column during dry season caused by NH4+-rich and anoxic submarine groundwater discharge (SGD). Nutrient dynamics in the coastal ecosystem point to potentially elevated microbial activities; however, little is known about microbial community composition and their functional roles in this area. In this study, we investigated microbial community composition, distribution, and metabolic prediction along the coastal hydrological compartment of Mobile Bay using 16S rRNA gene sequencing. We collected microbial samples from surface (river and bay water) and subsurface water (groundwater and coastal pore water from two SGD sites with peat and sandy lithology, respectively). Salinity was identified as the primary factor affecting the distribution of microbial communities across surface water samples, while DON and PO43- were the major predictor of community shift within subsurface water samples. Higher microbial diversity was found in coastal pore water in comparison to surface water samples. Gammaproteobacteria, Bacteroidia, and Oxyphotobacteria dominated the bacterial community. Among the archaea, methanogens were prevalent in the peat-dominated SGD site, while the sandy SGD site was characterized by a higher proportion of ammonia-oxidizing archaea. Cyanobium PCC-6307 and unclassified Thermodesulfovibrionia were identified as dominant taxa strongly associated with trends in environmental parameters in surface and subsurface samples, respectively. Microbial communities found in the groundwater and peat layer consisted of taxa known for denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This finding suggested that microbial communities might also play a significant role in mediating nitrogen transformation in the SGD flow path and in affecting the chemical composition of SGD discharging to the water column. Given the ecological importance of microorganisms, further studies at higher taxonomic and functional resolution are needed to accurately predict chemical biotransformation processes along the coastal hydrological continuum, which influence water quality and environmental condition in Mobile Bay.

Occurrence and seasonal variability of Dense Shelf Water Cascades along Australian continental shelves

Transport of water between the coast and the deeper ocean, across the continental shelf, is an important process for the distribution of biota, nutrients, suspended and dissolved material on the shelf. Presence of denser water on the inner continental shelf results in a cross-shelf density gradient that drives a gravitational circulation with offshore transport of denser water along the sea bed that is defined as Dense Shelf Water Cascade (DSWC). Analysis of field data, collected from multiple ocean glider data missions around Australia, confirmed that under a range of wind and tidal conditions, DSWC was a regular occurrence during autumn and winter months over a coastline spanning > 10,000 km. It is shown that even in the presence of relatively high wind- and tidal-induced vertical mixing, DSWCs were present due to the strength of the cross-shelf density gradient. The occurrence of DSWC around Australia is unique with continental scale forcing through air-sea fluxes that overcome local wind and tidal forcing. It is shown that DSWC acts as a conduit to transport suspended material across the continental shelf and is a critical process that influences water quality on the inner continental shelf.

Quantity of Coliform Bacteria as Bioindicator of Water Pollution (Case Study: Several Tributaries in Purwokerto City, Banyumas Regency, Central Java)

The city of Purwokerto is crossed by several large rivers, this research examines several tributaries of a large river. Some tributaries that pass through the city of Purwokerto are the Raden River, the Caban River, the Jurig River and the Luhur River. Tributaries have the potential to influence water quality. This study aimed to analyze the quantity of coliform bacteria as an indicator of water pollution in several tributaries in Purwokerto City, Banyumas Regency. Microbiological tests were carried out by calculating the total coliform quantity and fecal coliform using the Most Probable Number (MPN) test. Total coliform and fecal coliform can be used as a reference indicator of water quality in the presence of water pollution. The laboratory test results for the quantity of coliform bacteria showed in several tributaries in Purwokerto City, Banyumas Regency, very high in total coliform or fecal coliform, exceeding the water quality standard.

What matters most? Stakeholders’ perceptions of river water quality

The need to integrate stakeholders’ views into environmental policy is increasingly gaining attention because this offers the opportunity to design sustainable and synergistic environmental strategies. Understanding and integrating the views of resource users into policy design and implementation could help address the most important challenges, gain community support, enhance project ownership, and avoid policies being rejected by local people. As a result, research in environmental management has focussed on stakeholders’ perceptions of river water quality and how to integrate such views into policy. While existing studies offer insights into the different ways in which stakeholders evaluate river water quality and potential factors influencing judgements, they appear to be limited in a number of ways. First, most of these studies focus on developed countries and may have limited contextual relevance to the developing world. Moreover, past studies focus on segments of society such as farmers and mainly on wastewater for agriculture. These shortcomings may limit our understanding of the topic and our ability to design effective policies to address water quality problems. Drawing on survey data from the Wenchi municipality in Ghana, we examine public perceptions of what constitute important measures of river water quality as well as factors influencing such judgements. Results suggest that while variables such as taste, colour, smell and litter are important, the presence of faecal matter in and/or around the river was rated the most important measure of river water quality while depth of river was the least important. Results further suggest that education, age, number of years a person had lived in a community, depth of river and the presence of aquatic vegetation influence water quality judgements. The findings of this research provide insights into what policymakers and regulators need to consider when attempting to influence behaviours in relation to water resources. We note, however, that while public perceptions of river water quality could guide water management policies, scientific measurements of water quality must not be replaced with stakeholder perceptions. This is because aspects such as ecological integrity may not be important to segments of the public but are an important aspect of water management. This is reinforced in the present study as there seems to be a lack of concern among the participants regarding river depth – an important factor for habitat provision and pollution dilution.

Effects of Land Use on Stream Water Quality in the Rapidly Urbanized Areas: A Multiscale Analysis

The land use and land cover changes in rapidly urbanized regions is one of the main causes of water quality deterioration. However, due to the heterogeneity of urban land use patterns and spatial scale effects, a clear understanding of the relationships between land use and water quality remains elusive. The primary purpose of this study is to investigate the effects of land use on water quality across multi scales in a rapidly urbanized region in Hangzhou City, China. The results showed that the response characteristics of stream water quality to land use were spatial scale-dependent. The total nitrogen (TN) was more closely related with land use at the circular buffer scale, whilst stronger correlations could be found between land use and algae biomass at the riparian buffer scales. Under the circular buffer scale, the forest and urban greenspace were more influential to the TN at small buffer scales, whilst significant positive or negative correlations could be found between the TN and the areas of industrial land or the wetland and river as the buffer scales increased. The redundancy analysis (RDA) showed that more than 40% variations in water quality could be explained by the landscape metrics at all circular and riparian buffer scales, and this suggests that land use pattern was an important factor influencing water quality. The variation in water quality explained by landscape metrics increased with the increase of buffer size, and this implies that land use pattern could have a closer correlation with water quality at larger spatial scales.

Dissolved organic matter in hand-dug well water as groundwater quality indicator: assessment using laser-induced fluorescence spectroscopy and multivariate statistical techniques

In groundwater, dissolved organic matter (DOM), a complex material, is a contaminant of concern owing to its ability to influence water quality and stimulate microbial metabolism. Using a 445-nm diode laser-induced fluorescence (LIF) spectroscopy, DOM contamination levels have been investigated of well water samples fetched from ten privately owned hand-dug wells during dry and wet seasons of 2016, 2017 and 2018, in Ghana. The results showed spatio-temporal heterogeneities in the LIF spectra, and the fluorescence intensity peaks were generally higher and broader during the wet season than the dry season. In this study, DOM fluorescence spectra at an emission wavelength band of 460–650 nm showed two distinct broad peak shoulders within 480–500 nm and 550–570 nm, engulfing the water Raman peak at 527 ± 2 nm for all the water samples studied. Furthermore, principal component analysis and cluster analysis were used to differentiate the 2016 water samples based on their DOM contamination levels. In each case, three groups or clusters were identified based on their similarities and dissimilarities. The study revealed humic DOM substances as the most typical well water fluorophores. Applying the K-nearest neighbour algorithm as a classifier method for the classification of 30 water samples studied in 2016, 16.7% (5/30) were classified as very good drinking water, 46.7% (14/30) as good, 26.7% (8/30) as fairly good, and 10% (3/30) as bad drinking water samples. In general, levels of dissolved organic matter contamination increased over the study period during the rainy seasons for wells situated in close proximity to septic tanks, refuse dumps, public toilets and in wetlands. Thus, in the study the fluorescence intensity depends on the sampling site and the season, and indicates the DOM contamination level.

Red neuronal artificial para estimar un índice de calidad de agua

La red neuronal artificial (RNA) es un modelo computacional que emula el sistema neuronal biológico en el procesamiento de información; los modelos que se originan son adecuados con el propósito de describir pronósticos para tiempos prolongados, además de relaciones no lineales. Se utiliza esta herramienta con el fin de predecir parámetros físico-químicos y microbiológicos que influyen en la calidad de agua. La Fundación Nacional de Saneamiento de Estados Unidos propuso un índice de calidad de agua, conocido como NSF WQI. Este artículo describe el diseño, entrenamiento y uso del modelo de la red neuronal perceptrón de tres capas para el cálculo del NSF WQI del río Utcubamba y sus afluentes. Empleando el software Matlab y aplicando el algoritmo de entrenamiento de Levenberg-Marquardt, se encontró que la arquitectura óptima de la RNA es 6-12-1, además, el porcentaje para los conjuntos de entrenamiento, validación y prueba fue de 70 %, 10 % y 20 %, respectivamente. El rendimiento de la RNA se ha evaluado utilizando la raíz del error cuadrático medio (RMSE) y el coeficiente de correlación (R). Se mostraron correlaciones altas (mayores que 0.94) entre los valores medidos y predichos. Finalmente, la RNA propuesta ofrece una alternativa útil para el cálculo y la predicción del índice de calidad de agua en relación con el oxígeno disuelto (OD), la demanda bioquímica de oxígeno (DBO), nitratos, coliformes fecales, potencial de iones hidrógeno (pH) y la turbidez.