Spatial Distribution Of pH Research Articles

Просторово-часова нерівномірність забезпечення ґрунтів рухомими мікроелементами

Goal. To determine the spatial and temporal variation of the content of mobile trace elements in the arable layer of zonal soils of the Left Bank Forest Steppe of Ukraine. Methods. Field, soil monitoring, laboratory-analytical — for determination of mobile forms of trace elements in the soil by the method of atomic absorption spectrometry with extraction with ammonium acetate buffer solution with pH 4.8, and statistical. The research was conducted during 2018–2020 at 2 soil-agrochemical land ranges. The soil cover of one of them consisted of chornozems and dark gray podzolized soils, and of the other, typical chornozems and their varieties. Each of the ranges was divided into 24 plots, where twice a year (April–May, and September–October) pH of saline, organic carbon, moisture, and mobile Zn, Cu, and Mn in the arable soil layer were determined. Results. During the research period, the average saline pH parameters at the first land range varied from 4.4 to 5.0, and at the second land range from 5.8 to 6.1. At the first land range, the average content of Zn increased from spring to autumn from 0.63 to 0.81 mg/kg, Cu — from 0.25 to 0.38, and Mn — from 20.0 to 27.5 mg/kg. Conversely, on chornozems of typical content, Zn decreased from spring to autumn from 0.79 to 0.52 mg/kg, Cu from 0.35 to 0.16 mg/kg, and Mn did not change significantly. A very high level of variation was observed within each range, especially for Zn and Cu. However, centers of concentration or impoverishment of the soil on mobile trace elements mostly did not have a stable location. The spatial distribution of pH had a significant negative correlation with Mn, and in certain periods of observation, also with Zn. Conclusions. Mobile Zn, Cu, and Mn had significant temporal dynamics in the arable layer of the zonal soils of the Left Bank Forest Steppe, which was manifested in an increase in their content from spring to autumn under an acidic reaction of the environment and a decrease in Zn and Cu under close to neutral pH values. The variability of trace elements within each range was high, with coefficients of variation of 25–71% for Zn, 28–76 for Cu, and 9–52% for Mn. The closest negative relationship between Mn content and soil pH (correlation coefficients – 0.4––0.85) was noted in the samples of the experimental land range «Novyi Korotych» during the research periods.

Spatial Distribution, Source Apportionment, and Ecological Risk Assessment of Soil Heavy Metals in Jianghugongmi Producing Area, Shandong Province

Taking the Jianghugongmi producing area as the research object, As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the soil of the study area were sampled and determined. The correlation of heavy metals was discussed using the multivariate statistical method, the spatial distribution interpolation analysis of heavy metals was carried out using ArcGIS 10.2, the quantitative source analysis of heavy metal pollution was carried out using the enrichment factor (EF) and PMF methods, and the potential ecological risk was evaluated. The results showed that the contents of the soil heavy metals As, Cd, Cu, Hg, Pb, and Zn were lower than the screening values specified in the standard for soil pollution risk control of agricultural land (GB 15618-2018), and the soil ecological environment risk was low; the maximum values of Cr and Ni exceeded the risk screening values, but the risk was low. The main distribution range of pH in the study area was 6.05-6.69, which was suitable for rice growth. The Mohe River indicated the spatial distribution of pH and heavy metals, which was closely related to the supergene geochemical characteristics of the elements. However, Hg and Cd showed different spatial distribution characteristics under human influence. Hg was distributed in the middle and high value distribution area along the west side of the river, and the spatial distribution of Cd was significantly different from north to south. The quantitative source analysis results based on the EF method and PMF showed that the main sources of heavy metals in the study area were agricultural sources, mixed sources, coal sources, and natural sources. The contribution rates of various sources accounted for 24.2%, 35.4%, 9.5%, and 30.9%, respectively. The medium strong ecological risk points of Hg in the study area were distributed along the west side of the Mohe River, whereas the moderate potential ecological risk points of Cd were concentrated in the cultivated land on both sides of the Mohe River, and the potential ecological risk index (Er) of the other elements was<40. Cd and Hg were the main potential ecological risk elements in the study area, whereas Cd was still the main potential pollution element in the cultivated land soil in the study area.

Potential of multiparametric characterization of foodstuffs by nuclear magnetic resonance to better predict microbial behavior.

Numerous predictive microbiology models have been proposed to describe bacterial population behaviors in foodstuffs. These models depict the growth kinetics of particular bacterial strains based on key physico-chemical parameters of food matrices and their storage temperature. In this context, there is a prominent issue to accurately characterize these parameters, notably pH, water activity (aw ), and NaCl and organic acid concentrations. Usually, all these product features are determined using one destructive analysis per parameter at macroscale (>5g). Such approach prevents an overall view of these characteristics on a single sample. Besides, it does not take into account the intra-product microlocal variability of these parameters within foods. Nuclear magnetic resonance (NMR) is a versatile non-invasive spectroscopic technique. Experiments can be recorded successively on a same collected sample without damaging it. In this work, we designed a dedicated NMR approach to characterize the microenvironment of foods using 10-mg samples. The multiparametric mesoscopic-scale approach was validated on four food matrices: a smear soft cheese, cooked peeled shrimps, cold-smoked salmon, and smoked ham. Its implementation in situ on salmon fillets enabled to observe the intra-product heterogeneity and to highlight the impact of process on the spatial distribution of pH, NaCl, and organic acids. This analytical development and its successful application can help address the shortcomings of monoparametric methods traditionally used for predictive microbiology purposes.

Effect of Savanna windrow wood burning on the spatial variability of soil properties

ABSTRACT Tropical Savannas cover an area of approximately 1.9 billion hectares around the word and are subject to regular fires every 1 to 4 years. This study aimed to evaluate the influence of burning windrow wood from Cerrado (Brazilian Savanna) deforestation on the spatial variability of soil chemical properties, in the field. The data were analysed by using geostatistical methods. The semivariograms for pH(H2O), pH(CaCl2), Ca, Mg and K were calculated according to spherical models, whereas the phosphorus showed a nugget effect. The cross semi-variograms showed correlations between pH(H2O) and pH(CaCl2) with other variables with spatial dependence (exchangeable Ca and Mg and available K). The spatial variability maps for the pH(H2O), pH(CaCl2), Ca, Mg and K concentrations also showed similar patterns of spatial variability, indicating that burning the vegetation after deforestation caused a well-defined spatial arrangement. Even after 20 years of use with agriculture, the spatial distribution of pH(H2O), pH(CaCl2), Ca, Mg and available K was affected by the wood windrow burning that took place during the initial deforestation.

Controlling factors of riverine CO2 partial pressure and CO2 outgassing in a large karst river under base flow condition

Riverine CO2 outgassing constitutes the important vertical conduit in global carbon cycle and affects climate change. In order to investigate the factors that control riverine pCO2 and CO2 diffusion rate (FCO2), river water samples were collected in the mainstream and 42 tributaries of Xijiang River, a karst river during the dry season in 2015. The pCO2 varied from 260 to 6354μatm with a mean value of 1765μatm, indicating most of the samples were oversaturated with respect to CO2 compared to atmosphere. The pH, pCO2, and HCO3− exhibited clearly spatial distribution pattern that pH and HCO3− decreased along the flow direction while the pCO2 increased along the flow direction. Theoretical calculation indicated that the water temperature fluctuation, bio-degradation/respiration, photosynthetic activities and anthropogenic acidic inputs were not the reasonable explanations. The lithologic differences essentially predominated the riverine pH, pCO2, and HCO3−, the upper reaches of Xijiang River flow through karst carbonate terrain and thus exhibited high pH, HCO3− concentrations meanwhile low pCO2, the spatial distribution of pH, pCO2, and HCO3− became visible as the continuous addition of silicate weathering products with low pH and dissolved inorganic carbon (DIC) concentrations. The mixing calculation indicated the DIC concentrations of silicate weathering should lower than 0.5 mmol/L. The calculated FCO2 of Xijiang River ranged between −38.6 and 1579.8 mmol/m2/D, with a mean value of 574.8 mmol/m2/D and median value of 410.9 mmol/m2/D. FCO2 exhibited obviously lower values in karst terrain compared that in silicate terrains, because carbonate weathering results in high pH of karst rivers, which caused the low relative proportion of pCO2 in DIC. More estimations of CO2 outgassing rate from the karst rivers are required due to the unique characteristics and geochemical process in karst landform.

Groundwater quality assessment of Allahabad smart city using GIS and water quality index

Groundwater quality plays a very important role in groundwater protection as well as demarcation of the groundwater depleted area which may be attempted for its improvement and conservation. An effort has been made to comprehend the water quality of Allahabad city with the help of groundwater sampling, their chemical analysis, and synthesis of results in GIS framework. The assessment of physiochemical parameters of groundwater samples for drinking purpose has been made using Water Quality Index and Geographic Information System. Spatial distribution of pH, electrical conductivity, total dissolved solids, fluoride, iron, total alkalinity, total hardness, chloride, sulphate, sodium, potassium, calcium, magnesium, bicarbonate, and nitrate content of groundwater samples collected from 12 locations and studied for pre-monsoon (May 2016) and post monsoon (Nov 2017) periods has been assessed using Arc-GIS. Water quality maps of pre-monsoon period reveal that 4.23% area is falling under good, 74.82% under moderate, and 12.12% under poor and 0.66% under very poor category while water quality maps for post monsoon period reveal that the 40.33% of area falls under good, 58.89% area under moderate and 0.77% under poor water quality. The observed values of various physiochemical parameters of water samples were also compared with standard values recommended by IS 10,500:2012. It is observed that depth to water has positive correlation with TDS, electrical conductivity, and hardness. The extent of pollution occurred in the city is due to over exploitation of groundwater, urbanization, and anthropogenic activities.

Monitoring of pre- and post-monsoon groundwater quality of north-eastern Haryana region using GIS

ABSTRACT The present paper is the result of an investigation carried out to analyse the quality of sub-surface water in the districts of Yamunanagar and Ambala of the province of Haryana in India. The investigation was necessitated as the area combines the presence of industrial, commercial and residential units close to each other. A total of 30 groundwater samples were taken each during the months of April and September of 2017 and were appraised for analytical parameters, hydro-geochemical constituents and metal ions. Eight locations were observed to have an abnormal presence of only one element and were, therefore, classified to be falling in the ‘Grey-Zone’. Matedi Bus Stand (Sample number – 23) was found to be adversely influenced by the presence of the most of chemical elements and thus was categorized as the ‘Red Zone’. For the combined data of post-monsoon and pre-monsoon periods of 2017, the spatial distribution of pH, TDS, TA and TH showed that 100%, 90%, 91.67% and 93.33% of samples, respectively, fall under allowable limits of groundwater quality. Spatial distribution of hydro-chemical elements and metal ions showed that 96.11% of samples for cations, 98.33% for anions and 93.33% for Fe are in the ‘allowable’ category of groundwater. A comparison of laboratory results with the GIS maps prepared during the study has been found to be in good agreement. The classification of samples pursuance to their hydro-chemical facies indicated that most of the samples fall in Ca2+–Mg2+– –Cl− and Na+––Cl− type.

Spatial variability of soil pH sampled by two methodologies used in precision agriculture in farms under crop rotation

This study aimed to characterize the spatial variability of pH in soils of two farms in the state of Paraná, Brazil, based on two different sampling methods used in precision agriculture, by means of geostatistical analyzes. The first method of sampling the pH grid consisted in the collection of soil samples by the traditional method (1 point / ha). The second method of pH determination was by on-the-go soil sensor (200 points / ha). The spherical model was better suited to most semivariograms, regardless of the sampling method. After adjusting the semivariograms for soil pH determination methods, thematic maps were made using normal kriging. The best spatial distribution of pH was obtained where the attribute was sampled by the on-the-go sensor. The number of pH samples collected and the sampling method influenced the visual representation of pH variability.

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Temporal and spatial distribution of pH in flow-mode capacitive deionization and membrane capacitive deionization

Capacitive deionization (CDI) is a desalination technique that removes salt from saline water by applying a potential difference between two porous activated carbon electrodes. Although undesirable Faradaic reactions causing a deterioration in the desalination performance in long-term operation have been reported with pH fluctuations and hydrogen peroxide generation, the effect of the temporal and spatial pH distribution and quantitative analysis of charge consumption have rarely been reported or interpreted, especially in membrane capacitive deionization (MCDI). In this study, more detailed and precise investigations were quantitatively conducted to determine the charge consumption for ion adsorption, Faradaic reaction, the co-ion repulsion by analyzing the pH distribution on the electrode surface, the H2O2 and salt concentration, and the current profiles for short-term and long-term operations of CDI and MCDI. As major results, active Faradaic reactions caused a decrease in the deionization performance in the short-term operation, whereas in the long-term operation of CDI the sustained oxidation of carbon electrode caused its performance to decrease even further. On the other hand, regardless of a short or long term operation, less Faradaic reactions and less oxidation of the carbon electrode were observed with a superior deionization performance in MCDI.

PHYSICAL-CHEMICAL QUALITY OF A LATOSSOL UNDER DIRECT SEEDING AND SOYBEAN-CORN SUCCESSION IN THE CERRADO-AMAZONIAN ECOTONE

ABSTRACT The soybean-corn succession in no-tillage system (DSS) is the most common cultivation practice in the state of Mato Grosso. Soils submitted to this type of system are prone to the formation of fertility gradients and surface compaction, restricting crop productivity. The objective of this work was to evaluate the physical-chemical attributes of an Oxisol after 11 years of continuous succession of soybean and corn in direct seeding, using geostatistical analysis techniques and main components. The experiment was conducted at the Chão Nativo farm located in the municipality of Sinop, Mato Grosso, Cerrado-Amazonian ecotone. For this, a rectangular mesh was installed with 103 sampling points distributed in an area of 7.02 ha, in which the grain yield of the soybean was determined as well as the physical and chemical attributes of the soil in the layers 0-10 and 0.10 - 0.20 m. Soybean showed a grain yield between 2.83 and 3.70 Mg ha-1, which was positively correlated with the spatial distribution of pH, phosphorus and potassium. The soil presented low physical quality due to high soil resistance to penetration and macroporosity less than 10%; however, no spatial correlation of physical attributes with soybean yield was observed.

Assessment of the spatial variability of soil chemical properties along a transect using multifractal analysis

The spatial variability of soil properties can be assessed through concepts of scale invariance, fractals and multifractals. The aim of this study was to characterize the scaling patterns and structural heterogeneity properties of general soil chemical properties along a short (i.e. 52 m large) transect. Field measurements were carried out at the experimental farm of CIAM located in Mabegondo, A Coruña, Spain. The studied transect was marked following land slope, and 66 soil samples were collected at the 0-20 cm depth every 0.8 m. The soil properties analyzed were: pH (H2O ), organic carbon content, exchangeable Ca, Mg and K, exchangeable acidity (H + Al), exchangeable bases (SB), cation exchange capacity (CEC), percent base saturation (V) and extractable P. The soil properties studied showed various degrees of multifractality. The spatial distribution of pH was characterized by quasi-monofractal behaviour; CEC, (H+Al) and OM, presented a relatively low degree of multifractality, and the other soil properties studied showed stronger degrees of multifractality, being the highest one for Olsen extractable P. In general, the scaling features of the properties studied implied a multifractal nature, where the low and high density regions scaled differently.

Simultaneous Removal of Pb, Cd, and Zn from Heavily Contaminated Mine Tailing Soil Using Enhanced Electrochemical Process

Abstract This study examined the efficacy of electrokinetic remediation of chelated mine tailing soils with mixed heavy metals. Electrokinetic experiments were conducted in a nontraditional bench-reactor that contained intermediate liquid collection interfaces within treatment zones between the electrodes. Tests were conducted using 0.05 M Na2EDTA as the chelating permeant. Tap water was used in control experiments. A constant direct current voltage of 20 V (electric field≈0.625 V/cm) was applied across working electrodes for 48 h. Transient and spatial distribution of pH, conductivity, oxidation-reduction potential (Eh), and cumulative mass of the metal species in solution were measured. In all experiments, including controls, a larger portion of soluble metals were found in the anode reservoir, indicating transformation of the metals into complex species of negative charge, reverse electroosmotic advection toward anode, and/or colloidally assisted transport. Na2EDTA was expected to increase the metal ex...

Assessing groundwater quality for irrigation using indicator kriging method

One of the key parameters influencing sprinkler irrigation performance is water quality. In this study, the spatial variability of groundwater quality parameters (EC, SAR, Na+, Cl−, HCO3 − and pH) was investigated by geostatistical methods and the most suitable areas for implementation of sprinkler irrigation systems in terms of water quality are determined. The study was performed in Fasa county of Fars province using 91 water samples. Results indicated that all parameters are moderately to strongly spatially correlated over the study area. The spatial distribution of pH and HCO3 − was mapped using ordinary kriging. The probability of concentrations of EC, SAR, Na+ and Cl− exceeding a threshold limit in groundwater was obtained using indicator kriging (IK). The experimental indicator semivariograms were often fitted well by a spherical model for SAR, EC, Na+ and Cl−. For HCO3 − and pH, an exponential model was fitted to the experimental semivariograms. Probability maps showed that the risk of EC, SAR, Na+ and Cl− exceeding the given critical threshold is higher in lower half of the study area. The most proper agricultural lands for sprinkler irrigation implementation were identified by evaluating all probability maps. The suitable areas for sprinkler irrigation design were determined to be 25,240 hectares, which is about 34 percent of total agricultural lands and are located in northern and eastern parts. Overall the results of this study showed that IK is an appropriate approach for risk assessment of groundwater pollution, which is useful for a proper groundwater resources management.

Spatial distribution of pH and organic matter in urban soils and its implications on site-specific land uses in Xuzhou, China

The spatial variation of soil pH and soil organic matter (SOM) in the urban area of Xuzhou, China, was investigated in this study. Conventional statistics, geostatistics, and a geographical information system (GIS) were used to produce spatial distribution maps and to provide information about land use types. A total of 172 soil samples were collected based on grid method in the study area. Soil pH ranged from 6.47 to 8.48, with an average of 7.62. SOM content was very variable, ranging from 3.51g/kg to 17.12g/kg, with an average of 8.26g/kg. Soil pH followed a normal distribution, while SOM followed a log-normal distribution. The results of semi-variograms indicated that soil pH and SOM had strong (21%) and moderate (44%) spatial dependence, respectively. The variogram model was spherical for soil pH and exponential for SOM. The spatial distribution maps were achieved using kriging interpolation. The high pH and high SOM tended to occur in the mixed forest land cover areas such as those in the southwestern part of the urban area, while the low values were found in the eastern and the northern parts, probably due to the effect of industrial and human activities. In the central urban area, the soil pH was low, but the SOM content was high, which is mainly attributed to the disturbance of regional resident activities and urban transportation. Furthermore, anthropogenic organic particles are possible sources of organic matter after entering the soil ecosystem in urban areas. These maps provide useful information for urban planning and environmental management.

Field Study of the Chemical and Physical Stability of Highly Sulphide-Rich Tailings Stored Under a Shallow Water Cover

Highly sulfide-rich (approximately 83 % pyrite), potentially acid-generating mine tailings were sub-aqueously deposited in the Don Rouyn old quarry pit from 1997 to 2000. The site covers approximately 7 ha near Rouyn-Noranda, Quebec. Various in situ measurements and laboratory tests were performed during the summer and autumn of 2008, 2009, and 2010 to: characterize tailings samples; monitor water quality in the final effluent, shallow water cover, and groundwater around the pit, and; study tailings erosion and resuspension. In situ measurements included the vertical profile and spatial distribution of pH, temperature, dissolved oxygen, electric conductivity, and redox potential. Suspended tailings, wind speed, and direction were monitored. Groundwater, cover water, and final effluent water samples were chemically analyzed and suspended sediment concentrations (SSCs) was determined. Physical, mineralogical, and chemical tailings properties were also determined. Results show that the quality of the groundwater, cover, and effluent waters complied with Canadian and Quebec regulations. SSCs were also within regulation limits. No association was found between SSC and hydrodynamic conditions (wind speed, fetch, etc.). Although theoretical calculations indicated a critical wind speed of at least 10 m/s for tailings resuspension, suspended sediment was observed for wind speeds at <10 m/s.

Quantifying the Influence of Uncertainty and Variability on Groundwater Risk Assessment for Trace Elements

The application of leaching models to predict field‐scale heavy metal transport has been successful at several sites. Past studies involved site‐specific sorption experiments to quantify the leaching process and to investigate its spatial variability. Uncertainty due to lack of knowledge was frequently ignored. Here we present a leaching model that is based on an extended Freundlich equation to describe sorption. The equation is derived on a nationwide scale and is applicable to arbitrary sites in Germany. Instead of relying on site‐specific sorption experiments, it only requires information on the spatial variability of pH, organic carbon (Corg), and clay content. In addition to accounting for spatial variability, the model also considers the major sources of uncertainty influencing a leaching prediction. These sources involve uncertainty in the spatial distribution of pH, Corg, and clay content, as well as uncertainty of the extended Freundlich equation. The modeling strategy is based on a parallel soil column approach, in which a deterministic transport model is combined with a two‐dimensional Monte Carlo method. The model's ability to predict downward movement is tested on two sites in Germany—a wastewater irrigation area and an area in the vicinity of a metal smelter—where cadmium leaching has been modeled previously using extended Freundlich equations derived from local sorption data. Without any parameter fitting involved, the predicted field‐averaged cadmium profiles agree quite well with measured profiles in both cases.

Assessment on Seasonal Variation of Groundwater Quality of Phreatic Aquifers – a River Basin System

Spatial distribution of pH, electrical conductivity (EC), total dissolved solids (TDS), fluoride and total iron content of ground water samples collected from the muvattupuzha river basin, Kerala, India, has been studied for pre monsoon and post monsoon periods of year 2001. Results showed the groundwater of the basin is acidic for which the pH values ranged between 5.5 and 8.0. Average EC was found to be less than 100 microS/cm, for most of the study region. The pre monsoon minimum and maximum TDS were found as 25.6 and 227.84 mg/L respectively, where as post monsoon values ranged between 16 and 162.56 mg/L. The relatively low EC and TDS values found both during the seasons in the lateritic terrain of the river basin signifies the lower residence time of ground water with the country rock. This makes the groundwater quality of this river basin as good. Pre monsoon season samples showed high total iron content than that during the post monsoon period. During the study period values of the fluoride contents were found to be within the permissible limits.

Distribution of pH during galvanic corrosion of a Zn/steel couple

The spatial distribution of pH during galvanic corrosion of a model Zn/steel couple immersed in 0.01 M NaCl was investigated using a scanning tungsten pH electrode. The couple consisted of a steel substrate with a 3 μm-thick layer of zinc electroplated at its center. During galvanic corrosion, marked changes in pH occurred, which were confined to a thin layer of solution ca. 1.5 mm over the couple surface. As the surface was approached, the pH over the zinc layer decreased slightly from ca. 5.6 in the original bulk solution, while the pH over the steel surface distant from the zinc layer increased to ca. 11.5. The area of low pH extended not only over the zinc layer, but also over the steel surface adjacent to the zinc. Zinc corrosion products precipitated in the region of high pH. The pH distribution arising from the galvanic corrosion of the couple is discussed in terms of the potential distribution and the morphology of the precipitated zinc corrosion products.