Bulk pH Research Articles

Changes in the Physical, Chemical, and Bacterial Community Characteristics of Soil in Response to Short-Term Combined Organic–Inorganic Fertilizers in a Dry Direct-Seeded Paddy Field

Dry direct-seeded rice cultivation is a simple and labor-saving planting method wherein the combined application of organic and inorganic fertilizers can improve yield. However, the effects of combined fertilizers on soil properties and bacteria in dry direct-seeded rice paddy soil are unclear. Here, four treatments, conventional fertilization (NPK), seaweed bio-organic fertilizer + NPK, Jishiwang bio-organic fertilizer + NPK, and attapulgite organic fertilizer + NPK applied for three consecutive years were tested to explore their effects on soil physical, chemical, and bacterial community characteristics in a dry direct-seeded rice paddy field. The combined fertilizers increased alkaline hydrolysis-nitrogen and available potassium while decreasing the bulk density and pH; in addition, a marked increase in the relative abundance of soil macroaggregates (>5 mm) and clay particles and a decrease in that of sand was observed. Urease and neutral phosphatase activities were the highest with the Jishiwang organic fertilizer + NPK, whereas invertase and catalase activities were the highest with attapulgite organic fertilizer + NPK. All combined fertilizers considerably increased the bacterial richness index (ACE) and Chao index; Jishiwang bio-organic fertilizer + NPK also increased the Simpson index, whereas the seaweed bio-organic fertilizer + NPK reduced it. Proteobacteria and Acidobacteria accounted for 54.25–70.49% of the total bacterial relative abundance. The relative abundance of Verrucomicrobia, Chloroflexi, Firmicutes, and Nitrospirae increased with the combined fertilizers. The correlation network analysis showed predominant antagonistic relationships. A redundancy analysis demonstrated that total nitrogen, soil organic matter, urease, and invertase were the main environmental factors affecting bacterial composition. Combined fertilizers may improve soil physical and chemical properties, fertility, and bacterial richness.

Quality Ealuation of National Cereals Research Institute Brown Sugar

A brown sugar process technology [BST] was developed using a simple batch system and a local clarifier at the National Cereals Research Institute [NCRI], Badeggi. The quality characteristics of the brown sugar produced from the technology were studied. Where necessary and feasible the brown sugar quality was compared to industrial brown sugars. The bulk density, solubility, particle size, brix percentage, pH, Pol%, soluble and insoluble fractions, water sorption properties, proximate composition, microbial load and organoleptic properties of the sugar were evaluated. The results showed that the brown sugar had 82.87% solubility as compared to 85.80 and 72.73% of industrial samples. The bulk density was 0.88g/cm3 as compared to 0.82 and 0.95g/cm3. The particle size ranged from 600µm-10mm with 53% passing through 600µm-1.18mm. The moisture sorption studies showed that the brown sugar exhibited a sigmoid shaped structure with monolayer moisture content of 0.63gH20 while the surface area was 0.0036x10M2 /g solid. There was no apparent presence of fibre but ash content was high [10.00%] while protein as expected was very low [0.26%]. The microbial load was low 20x103 cfu/g while feacal pollution was not observed. The NCRI brown sugar was preferred to the industrial samples and had an acceptability score of 4 in a 5-point-hedonic scale.

Do the Soil's Physiochemical Properties Fluctuate with Season and Soil Depth in the Ecological Critical Areas (ECA) of Sundarbans, Bangladesh?

The Ecological Critical Areas (ECA) of Sundarbans is located outside of Sundarbans Reserved Forest at 10 km extended landward, which is threatened to reach a critical state due to human activities. Aquaculture is the dominant land use in the ECA and the tree coverage is going to deplete at an alarming rate due to the deterioration of site conditions, which significantly influence the productivity of aquaculture and the establishment of the plantations on the dikes of the fishpond. The present study aimed to assess some static and dynamic soil physiochemical properties of the fishpond dikes located in the ECA of Sundarbans. Soil samples were collected from the western part (Satkhira district) of ECA of Sundarbans during the pre-monsoon and post-monsoon seasons. The bulk density, pH, and electrical conductivity of the studied areas varied from 1.05-1.18 g/cm3, 7.30-8.54, and 1.05-2.13 ms/cm respectively. However, the concentration of available form of Nitrogen, Phosphorus, Potassium and Sodium were 0.5-0.72 mg/g, 0.03-0.06 mg/g, 10.5-12.88 mg/g and 16.89-20.53 mg/g respectively. Some of these parameters showed significant variation among the zones, seasons, and soil layers. However, the stock of available nitrogen, phosphorus, potassium, sodium and organic carbon varied from 52.5- 84.96 kg/ha, 3.15-7.08 kg/ha, 1.10-1.52 t/ha, 1.77-2.42 t/ha and 173.47-199.43 t/ha respectively. As pond soil provides all the important nutrients with water, the findings of this study will help to take proper management interventions for the dike greening initiatives and productivity of fishponds in the ECA of Sundarbans.

Unravelling Mass Transport Effects in Electrochemical Nitrate Reduction on Titanium

Nitrate is a prevalent waterborne pollutant that threatens the health of humans and aquatic systems. By selectively producing ammonia, electrochemical nitrate reduction reaction (NO3RR) can directly transform nitrate pollutants into widely used commodity chemicals and fertilizers, thus balancing the nitrogen cycle while reducing energy consumption from the traditional Haber-Bosch process.Although research efforts to date have primarily focused on the development of efficient nitrate reduction catalysts, the electrolyte environment has been found to substantially influence NO3RR activity and selectivity. Specifically, the composition of the first ten nanometers of electrolyte away from the electrode surface dictates the immediate environment within which reactions take place. As has been demonstrated in the electrochemical CO2 reduction reaction, this interfacial reaction microenvironment comprised of near-surface electrolyte and electrocatalyst influences reaction activity and selectivity. In electrochemical NO3RR, where an anionic species reacts at a negatively charged electrode, the reaction rate can often be limited by the mass transport of the reactant nitrate. Additionally, mass transport phenomena define the electrolyte side of the reaction microenvironment by influencing other interfacial properties (i.e., electric potential, pH and ion concentrations). Therefore, we investigated the influence of mass transport phenomena on NO3RR activity and selectivity.In this study, we used a membrane-separated flow cell as a representative and translatable reactor and titanium foil as a common ammonia-selective NO3RR electrode. By varying the electrolyte flow rate, we controlled the mass transport phenomena in the flow cell and empirically determined the diffusion layer thickness. We found that NO3RR activity generally increased with increasing electrolyte flow rate, as predicted from the decreasing diffusion layer thickness, whereas NH3 selectivity slightly decreased, showing an activity-selectivity trade-off.To unravel the origins of the experimentally observed mass transport effects, simulations using the 1D generalized modified Poisson-Nernst-Planck (GMPNP) model were conducted to spatially resolve interfacial properties. Interfacial cation concentration and pH were the two properties that changed most significantly with electrolyte flow rate. Informed by simulation results, we controlled the bulk electrolyte composition to modify the interfacial cation concentration and pH and examine their impacts on NO3RR activity and selectivity. Nitrate removal rate decreased by half when the bulk cation concentration was lowered to 1/100 of the original bulk concentration but the product distribution was similar. Meanwhile, in phosphate buffered electrolytes with different bulk pH values, NH3 selectivity decreased as bulk pH increased, with NO3RR activity remaining largely unchanged. Therefore, we attributed the influence of mass transport on NO3RR selectivity to changes in the interfacial pH during reaction, likely as the result of the varying NO3RR activity under different flow rates. By comparing the nitrogen species product distribution in different electrolytes, we inferred that the interfacial pH increased rapidly to basic in non-buffered systems regardless of their bulk pH.In summary, we systematically investigated the underexplored effects of mass transport on NO3RR and found that it influenced the reaction activity and selectivity by influencing interfacial properties. This study underscores the importance of scrutinizing the interfacial electrolyte environment in electrocatalyst development and provides insight to optimize NH3 production by engineering the bulk electrolyte.

Selected physical parameters of spruce chips vs. alkali consumptions in the impregnation step of kraft pulping

The uniformity of pulp and the amount of rejects are influenced by many factors, but impregnation can be the most important. The opportunities for improving impregnation of kraft white liquor start in description of the parameters affecting the process. The first parameter is the chip itself (its basic density, moisture, and pH) and the second is the process parameters set by the technological possibilities of the digester. During outside storage, the chips deteriorate via the fungal stains, brittleness, and high acidity. The moisture content also decreases. Understanding the relationships of chip parameters in the impregnation step and amount of rejects requires the assignment of effective alkali consumption. This study shows the effects of selected physical parameters, such as bulk density, moisture, and pH, of spruce chips on alkali consumption during impregnation step of a Super Batch process.

The Recent Advances in Bulk and Microfluidic-Based pH Sensing and Its Applications

The determination of pH is of paramount importance in environmental, pharmaceutical, and medicinal sciences, etc., for accurate controlling, monitoring, and adjusting whole processes on microscale and macroscale. Therefore, the pH measurements have drawn continuous efforts from a great deal of research. The bulk pH determination can tackle part of the demands from laboratories and industrial applications. However, more and more studies have started to pay more attention to microfluidic-based pH sensing by integrating with metal oxides and solid-state-based pH sensing applications. This review paper focuses on the recent development of pH sensing, the mechanisms of pH sensing, a few common pH sensors, and microfluidic-based pH determinations from the aspects of fabrication techniques to the various applications in biology, environmental study, and food safety. The future trends of pH sensing, as well as microfluidic-based pH sensing, were discussed as well at the end of this review.

Soil clay is a key factor affecting soil phosphorus availability in the distribution area of Masson pine plantations across subtropical China

Evaluating the environmental effects on soil phosphorus (P) availability is the key to understanding P cycling and regulating forest productivity. However, what and how environmental factors affect soil P availability in regional plantation ecosystems remains unclear. The study evaluated the effects of climatic factors, nitrogen deposition rate, stand attributes, litter characteristics, and soil-associated properties on soil P availability in Masson pine plantations across subtropical China using stepwise regression and structural equation modelling (SEM) analyses. At the 0–20 cm and 20–40 cm soil depths, soil total P ranged from 0.24 to 0.43 g kg−1 and from 0.24 to 0.48 g kg−1, respectively. Similarly, soil available P varied from 0.35 to 7.55 mg kg−1 and from 0.14 to 4.34 mg kg−1, respectively. Soil total and available P had high values in the eastern and northern distribution areas of subtropical China. Soil total P linearly decreased with an increase in bulk density, clay and pH but linearly increased with an increase in DBH. These four factors had a similar contribution (15.5–35.1 %) to soil total P. Soil available P linearly decreased with an increase in bulk density and clay. The relative contribution of clay (48.1–75.7 %) to soil available P was higher than that of bulk density (16.2–33.5 %). Soil total P decreased during the initial 30 years of plantations and then increased. But other variables (e.g., climate, nitrogen deposition, and litter) had no significant impacts on soil P. Overall, the SEM explained 35.4 % and 28.1 % of soil available P variations at the 0–20 cm and 20–40 cm soil depths, respectively, and revealed that clay had strong total effects (β = -0.526 and −0.396) on the soil available P. These results reveal the dominant roles of soil texture (especially clay) in affecting soil P availability in Masson pine plantations and suggest that extending the rotation period benefits soil P recovery in pine plantation ecosystems of subtropical China.

Water Orientation at the Anatase TiO2 Nanoparticle Interface: A Probe of Surface pKa Values.

The acid-base properties of surfaces significantly influence catalytic and (photo)electrochemical processes. Estimation of acid dissociation constants (pKa values) for colloids is commonly performed through electroanalytical techniques or spectroscopic methods employing label molecules. Here, we show that polarimetric angle-resolved second harmonic scattering (AR-SHS) can be used as an all-optical, label-free probe of colloid surface pKa values. We apply AR-SHS to dispersions of 100 nm anatase TiO2 particles to extract surface potential and surface susceptibility, a measure of interfacial water orientation, as a function of pH. The surface potential follows changes in surface charge density, while the interfacial water orientation inverts at pH ∼4.8, ∼6, and ∼7.6. As the variation in bulk pH modifies the populations of Ti-OH2+, Ti-OH, and Ti-O- interfacial groups, a change in water orientation reports on the ratio of protonated/deprotonated species. Such observation allows for pKa evaluation from plots of surface susceptibility versus pH. A Nerstian trend in the surface potential is additionally demonstrated.

Distribution of SOCD along different offshore distances in China's fresh-water lake-Chaohu under different habitats

Carbon storage in wetland ecosystems is an important part of the carbon cycle of terrestrial ecosystems and provides important ecosystem services. Chaohu Wetland is a typical freshwater lake wetland in China. In this study, soil and plant samples were collected every 500 m through three sample lines of different vegetation habitats (estuarine banks, woodlands and shrub beaches) and different offshore distances, revealing the spatial distribution characteristics of soil organic carbon density (SOCD) in Chaohu wetland. The overall SOCD of Chaohu wetland was low, with different habitats ranking as Woodland > Estuary and riverside > Shrub and beach. SOCD of different offshore distances had no obvious law, and the SOCD decreased significantly with soil depth. The plant biomass was significantly higher at the woodland habitat than at other habitats. Most of soil nutrient indicators were the highest at the woodland habitat, while the estuary-riverside habitat had the highest N and P contents. Soil and plant nutrients at different offshore distances had no obvious change patterns. The contents of soil K, Ca, Mg, and N were significantly positively correlated with SOCD, but soil bulk density and pH were significantly negatively correlated with SOCD, and vegetation P content was significantly negatively correlated with SOCD. The spatial pattern of SOCD changes in this lake coastal wetland was determined by the combined effects of plant nutrients, biomass, and soil physical and chemical properties. Our results indicate Chaohu wetlands may have been experiencing serious degradation. The SOCD of Chaohu wetland is lower than that of other wetlands in China, which is mainly affected by human activities. Different offshore distances and habitat heterogeneity are the main factors affecting the soil carbon cycle of the wetland.

Crop intensification effects on soil quality and organic carbon stocks: a case study of Haramosh Valley in Central Karakorum, Pakistan

ABSTRACT Agricultural operations such as excessive tillage and intense cropping deplete soil organic carbon (SOC), making sustainable agriculture management critical for reducing greenhouse gas (GHG) emissions. This study evaluates the impact of crop intensification on soil quality and soil organic carbon stocks (SOCS) under double cropping (DC) and single cropping pattern (SC) in upper Haramosh of Gilgit, Pakistan. Soil samples were taken from cropping zones (DC and SC) under three depths (0–20, 20–40, and 40–60 cm). Standard methods were used to analyze selected soil quality parameters and SOC. Statistical analysis using ANOVA showed that soil temperature, moisture, pH, SOC, and SOCS highly significantly differed (p < 0.001) for different cropping patterns (DC and SC), whereas bulk density (BD), electrical conductivity (EC), and clay were not significantly different. The SC retained 4.4% more moisture and had lower BD than the DC, while BD increased with increasing depth. The texture of the soil was sandy loam at both cropping zones. The mean SOC and SOCS of SC were greater (by 12%) than in the DC zone. Pearson correlation showed a significant and positive correlation of SOC stock with SOC, moisture (p < 0.01), and EC (p < 0.05), but had a negative correlation with bulk density, pH (p < 0.01), and sand (p < 0.05). DC apparently degraded soil quality and organic carbon reserves, thus reducing the soil health in mountain agriculture.

Study on primary physicochemical characteristics and nutrient adsorption of four plant cultivation substrates

The primary physicochemical characteristics and the nutrient adsorption of different substrates were carried out, to select suitable cultivation substrates for plant cultivation in space. Four types of plant cultivation substrates (Profile substrate (P), black ceramsite (B), white ceramsite (W), and vermiculite (V)) were used to test and compare the primary physicochemical characteristics, such as micropore, bulk density, total porosity, specific surface area and available nutrient content, as well as the nutrients adsorption for NH4+, NO3–, PO43– and K+ with seven concentration gradients respectively. Substrate P contained more micropores, with higher parameter values of total porosity, cation exchange capacity, electrical conductivity, and specific surface area, moderate bulk density and pH, and more mineral nutrients such as potassium, magnesium, and sulfur; substrate B was porous, with smaller parameter values of total porosity, cation exchange capacity and specific surface area, minimum electrical conductivity, moderate bulk density, alkaline and smaller content of mineral elements (excepting for calcium); substrate W had smaller micropore size, the highest value of bulk density and contents of NO3– and PO43–. Other physicochemical parameters were equivalent to those of substrate B; substrate V was flaky, with the smallest values of bulk density, and the highest values of total porosity and cation exchange capacity. The values of electrical conductivity and specific surface area were smaller than those of substrate P. It contained more mineral nutrients of calcium and sulfur. Substrate V had the highest adsorption capacity for NH4+, NO3–, PO43– and K+, followed by substrate P, while substrate B and substrate W had relatively weak adsorption capacity. The adsorption capacity of four substrates for cations (NH4+ and K+) was significantly higher than that for anions (NO3– and PO43–). The orders of average adsorption amount for NH4+, NO3–, PO43– and K+ by four substrates were respectively: V > P > B > W, P > V > W > B, V > P > B > W and V > P > W > B. In comparison, substrate P and substrate V had better physicochemical characteristics, and stronger adsorption capacity for NH4+, NO3–, PO43–, and K+.

Probing the relationship between bulk and local environments to understand impacts on electrocatalytic oxygen reduction reaction

Local catalyst environments fluctuate during electrochemical reactions which significantly influences reaction efficiency and selectivity. However, elucidating fundamental relationships between local environment and electrocatalytic performance is challenging due to the difficulty in probing this local region. Here, we study the impact of electrolyte composition on the kinetics and mechanism of the oxygen reduction reaction (ORR) for a carbon catalyst. Using a rotating ring-disk electrode equipped with an iridium oxide pH probe, we monitor changes in local pH during ORR. We confirm that local pH changes significantly for near-neutral bulk pH and find that different cations provide variable pH-buffering, thereby modulating overall magnitude and onset of local pH changes. Overall, local pH more strongly dictates changes in mechanisms and performance, while the cation identity modulates local pH to influence these trends. This work highlights the importance relating local pH to electrocatalytic performance to further improve understanding of complex electrochemical processes.

Effects of rape/common vetch intercropping on biomass, soil characteristics, and microbial community diversity

Legume–brassica intercropping is widely used to increase productivity in modern, sustainable agricultural systems. However, few studies have assessed the linkages between soil properties and soil microorganisms. Soil microorganisms play a key role in soil nutrient turnover and plant community composition. To elucidate the responses of soil microbial community diversity and structure to intercropping, we conducted a 2-year experiment based on common vetch (CV) monoculture, rape (R) monoculture, and common vetch–rape intercropping (IRCV) with phosphorus (P) addition in alkaline soil. The microbial communities of bacteria and fungi in the rhizosphere soil were examined based on high-throughput sequencing targeting the 16S rRNA and ITS genes, respectively. In addition, we analyzed changes in soil properties and enzyme activities. Intercropping significantly increased dry matter (up to 98.86% and 81.48%, respectively dry matter is the aboveground biomass.) compared with common vetch monoculture. Intercropping decreased soil bulk density and pH and enhanced soil available phosphorus (AP) by 14.54–34.38%, 7.25–22.67%, soil organic matter (SOM) by 15.57–22.85, 6.82–15.57%, soil sucrase (Suc.) by 13.69–16.10%, 35.57–40.24% compared to monoculture common vetch and rape, respectively. However, bacterial alpha diversity was higher under rape monoculture than IRCV. In addition, the dominant soil bacterial phyla Proteobacteria (1.25–3.60%), Gemmatimonadetes (7.88–15.16%), Bacteroidetes (9.39–11.76%), and Rokubacteria (0.49–5.69%) were present at greater abundance with IRCV relative to those with CV and R, but phyla Chloroflexi was significantly decreased by 11.56–12.94% with IRCV compared with the other two treatments. The redundant analysis showed that SOM and AP were positively correlated with the dominant bacterial and fungal flora. Common vetch–rape intercropping resulted in increased biomass and altered soil microbial community composition as well as soil properties. Our results showed that intercropping systems positively improve soil microbial activity; this strategy could help in the cultivation of multiple crops and improve soil properties through sustainable production.

Effect of biofertilizers and vermicompost on physico-chemical properties of soil under wheat (Triticum aestivum) crop

A field experiment was conducted at the Instructional farm, Rajasthan College of Agriculture, Udaipur for two years (2017–18 and 2018–19) during the winter (rabi) season. The experiments were arranged in a randomized block design (RBD) manner with 3 replications. The results showed that, seed inoculation with biofertilizers (Azotobacter + Phosphorus solubilizing bacteria + Potash mobilizing bacteria + Zinc solubilizing bacteria) improved physico-chemical properties of soil except bulk density, particle density, pH, EC and showed higher availability of nutrients over control plot. Whereas in case of vermicompost (VC), physical properties such as BD, PD, porosity, WHC and chemical properties like pH, EC, CEC, OC and available nutrients were found distinctly enhanced under 50% VC at sowing + 50% VC at tillering in post-harvest soil over control. However, 50% VC at sowing + 50% VC at tillering significantly reduced bulk density, particle density, pH and EC. Furthermore, both biofertilizers and split application of vermicompost also significantly improved the productivity of wheat. It is concluded that application of biofertilizers and vermicompost could reliably be used to improve soil physico-chemical properties of wheat cultivated soils.

A theoretical understanding of ionic current through a nanochannel driven by a viscosity gradient

HypothesisDifferent thermodynamic forces owing to the gradient of temperature, electrical potential, or concentration can drive ionic current through charged membranes. It has been recently shown that a viscosity gradient can drive an electrical current through a negatively charged nanochannel (Wiener and Stein, arXiv: 1807.09106). A model description of this phenomenon, based on the Maxwell–Stefan equation will help unravel the dominating physical mechanisms in so-called visco-migration. TheoryTo understand the physical mechanisms underlying this phenomenon, we employed the Maxwell–Stefan equation to develop a 1D model and obtain a relation between the flux of solvents and the driving forces. Viscosity gradients are known to drive transport, but the development of an electrical current has not been theoretically described prior to this work. FindingsOur 1D model shows that the ionic current depends on the ideality of the solvent, though both ideal and non-ideal scenarios demonstrated good agreement with experimental data. We employed the model to understand the impact of solution bulk ionic strength and pH on the drift of ionic species with same reservoirs solution properties. Our modeling results unveiled the significant impact of bulk solution properties on the drift of ions which is in agreement with the experiments. Moreover, we have shown that the diffusion gradient along the nanochannel contributes significantly into driving ionic species if we even apply a small ionic concentration gradient to both reservoirs. Our modeling results may pave the way for finding novel applications for drift of ions in a diffusion gradient, which can be induced by connecting reservoirs of different viscosity fluids.

Modelo cinético hidrodinámico para el estudio de la formación de depósitos de CaCO3 en tuberías

Calcium carbonate deposition inside of pipes is a widespread problem in aqueous fluid transport systems, where calcium and carbonate ions are dissolved. The present study describes the physical and chemical phenomena of mass transport of the chemical species, from the bulk solution to the pipe walls, inside a straight circular pipe. The mass transfer coefficient is estimated using correlations for developing laminar flow. The controlling mechanism is assigned using the Damköhler number and the model simulation results are analyzed for three scenarios: when mass transfer controls the deposition, by mixed control or by the deposition kinetics. If mass transfer is the controlling mechanism, the deposit was concentrated at the pipe entrance, while with kinetic control, it forms further downstream. This study found that most important factor influencing the deposition process is the bulk and superficial pH values.

Boron removal from synthetic brines and oilfield produced waters using aluminum electrocoagulation

High boron (B) levels in oil and gas produced waters prevent its beneficial reuse as irrigation water without proper treatment. Aluminum (Al) electrocoagulation (EC) is a promising technology for B removal, but further research and development is needed to optimize EC for use in removing B from produced waters. To this end, B removal by adsorption onto insoluble aluminum hydroxide solids, generated by EC in simulated brines (up to 50,000 mg/L NaCl) and real oilfield produced waters, was studied. B removal during EC was greater than when aluminum hydroxide solids formed by EC were subsequently exposed to B containing solutions. Working parameters affecting B removal during the EC process, including current, total dissolved solid (TDS), temperature, pH, scale-forming cations and organic matter, were investigated to explore ways to achieve higher B removal. Boron removal increased with increased current loading and time, and with the concomitant increased Al solids concentration. However, too high a current loading limited B removal because of a change in the structure of the aluminum hydroxide solids. Higher TDS decreased B removal slightly, but lower TDS concentrations limited the use of higher current loadings. Temperature increased during EC treatment, particularly at higher current loadings, and this inhibited B removal due to an accelerated aggregation of amorphous Al solids into larger, denser, and presumably more crystalline particles. The best B removal occurred at pH 8, corresponding to a slightly positive zeta potential for aluminum hydroxide and a small but significant fraction of negatively charged B species. Scale-forming cations such as Ba2+ and Sr2+ had no obvious effect on the EC process. The presence of high concentrations of Mg2+ and Ca2+ resulted in low bulk pH values during the EC process and greater formation of solid products, but B removal did not decrease during a pH-controlled (pH = 8) EC process with these divalent cations present. Two produced water samples collected from oilfields in Kansas, US were treated using EC for 1 h, resulting in up to ~70 % B removal from solution with a current loading of 6.67 A/L, and up to 78 % with 13.33 A/L.

Soil quality under different agricultural land uses as evaluated by chemical, geochemical and ecological indicators in mountains with high rainfall (Darjeeling Himalayas, India)

PurposeAgricultural land use associated with intensification in plant growing affects the physicochemical parameters of soils and thus soil quality. The aim of this study was to identify the quality of soils in the Peshok catchment in the Eastern Himalayas under different types of land use (tea, horticulture, rice), under high monsoon rainfall conditions.MethodsPhysical and chemical analysis were used, e.g. bulk density, pH, TOC, major and trace element content (such as Ca, Fe, K, Mg, Mn, Na, P, Ag, As, Ba, Cd, Co, Cr, Cu, Ga, Li, Mo, Ni, Pb, Sr and Zn) based on AntonPaar Multiwave 3000 microwave system and nitrogen and sulphur content using CNS Elementar Vario MAX cube analyser. In addition, ecotoxicological analyses were performed using the Microtox test. Soil quality was assessed on the basis of chemical indicators related to the mobility of trace elements (risk assessment code, individual contamination factor and global contamination factor); geochemical indicators (geoaccumulation index, enrichment factor, contamination factor, contamination degree, modified contamination degree, pollution load index and improved Nemerow pollution index); and ecological indicators (potential ecological risk coefficient and potential ecological risk index). A statistical package of Statistica v13 was used for statistical analysis.ResultsSoils in the analysed catchment are characterised by low contents of macro- and microelements. It was shown that natural factors, such as high precipitation and steep slopes, favour strong leaching of elements from the soil, and farming systems based on natural and chemical fertilisation, terracing and irrigation are not able to balance them fully. The contents of TOC and N as well as pH were determined mainly by the land use. Results of statistical analyses and geochemical indicators revealed the predominantly natural origins of elements. The higher Ga content indicated a relationship with the local geology and the higher Cu content with the use of fertilisers. Indicators showed a low ecological risk related to the presence of trace elements, and soil ecotoxicity to A. fischeri was generally determined by the acidic pH of the tested soils. Low mobility was observed for most elements, and regardless of the land use, the residual fraction predominated.ConclusionThe study showed that use of many indicators can more fully describe soil quality in relation to land use, especially in the case of a low content of trace elements. Moreover, this approach helps to better understand the changes taking place in soil quality under different land uses in mountains with high rainfall.

Effect of Date Palm Derived Biochar on Soil’s Bulk Density, pH, and Nitrogen Content

The use of biochar as a soil amendment has been the focus of many studies. It is believed to improve soil characteristics and increase crop yields. Still, a diverse range of feedstocks needs to be researched and converted to biochar for environmental purposes.To achieve sustainable biochar, it is favorable to be derived from residues available locally, and particularly interesting are those that have been turned to biochar near the application area. This study investigates the effects of locally date palm-derived biochars produced at four different temperatures (250, 350, 450, and 550oC) for 60 minutes on soil physicochemical properties, mainly; pH, bulk density, and total nitrogen availability. The biochar application ratios were 5% and 10% by weight to each soil sample. The soil was gathered from a local farm near Al-Kargoulia, textured as clay loam, and had a total nitrogen content of 25 mg/kg. From mixing through incubation, the experiment lasted 30 days. Biochars produced at (250-350oC) have a minor impact on soil characteristics, whereas biochar produced at (450-550oC) had a higher effect on soil properties. Bulk density was decreased due to biochar’s high porosity (up to 90%), while pH increased from 7.23 to 8.5. In contrast, nitrogen was affected highly and increased to 32.33 mg/kg.

Long-term Conservation Agriculture increases sulfur pools in soils together with increased soil organic carbon compared to conventional practices

Long term depletion of sulfur (S) in soils is common in many cropping systems globally, and especially in intensive, rice-based rotations in Asia. We hypothesized that Conservation Agriculture (CA) practices (minimal soil disturbance and crop residue retention) will increase S in soils primarily through changes in soil organic carbon (SOC). A long term experiment was sampled after 24 crops of continuous practice of (A) contrasting soil disturbance (strip planting = SP and conventional tillage = CT) and (B) two levels of crop residue retention (low residue = LR and high residue = HR). Sulfur fractions and dynamics in soil at five depths (0–5, 5–15, 15–30, 30–45 and 45–60 cm) along with bulk density (BD), pH, SOC, total nitrogen (TN) and extractable nutrients were determined. Levels of total S (584 – 668 mg kg−1), organic S (50.0– 153 mg kg−1), available S (7.9 – 21.6 mg kg−1) and water soluble S (6.0 – 17.0 mg kg−1) were the highest in SP with HR (P < 0.05), while inorganic S (505 – 533 mg kg−1) and adsorbed S (2.3 – 4.4 mg kg−1) were significantly higher (P < 0.05) in HR plots irrespective of tillage systems at 0–30 cm soil depth. All the S fractions were positively and strongly correlated with SOC and except for inorganic and adsorbed S, all other S fractions were positively correlated with TN, extractable P, Zn, B and Fe. All S fractions were negatively correlated with BD. Inorganic S was the dominant S fraction but highly significant and positive correlations of available S with organic S (r = 0.92) and water–soluble S (r = 0.92) suggests these two fractions were the main sources of plant available S. This study suggests that both minimal soil disturbance and increased crop residue retention, core components of CA, increased S pools in soils primarily due to increased SOC sequestration.