Cation Exchange Capacity Research Articles

Fluvial avulsions influence soil fertility in the Pantanal wetlands (Brazil)

River avulsions drive important changes in the Pantanal wetlands, owing to their role in the hydro-sedimentology of the region. Although relevant to numerous ecosystem services, few studies have analyzed the influence of river avulsions on soil fertility in the Pantanal. Here, we use the largest ongoing avulsion in the Taquari River (Caronal region) to evaluate the effects on soil fertility, considering two factors: avulsion stage (1) and aquatic-terrestrial succession (2). Since both factors are influenced by macrophyte abundance, an incident map was created through tasseled cap indices from Sentinel 2 images to guide sampling efforts in flooded soils. The mapped area was split into two zones of alluvial processes, the first from the apex of the Caronal lobe corresponding to the Taquari River megafan (TRM), and the second as the distal Paraguay River floodplain (PRF). Soil macro- and micronutrient levels were evaluated from 42 surface samples (0–0.2 m) distributed across the two alluvial process zones. The macrophyte map's overall accuracy (OA) was analyzed by a confusion matrix using the Sentinel 2 imagery. Finally, we used Random Forest regressions to determine the influence of response variables on soil attributes, including tassel indices, distance from the Caronal crevasse, macrophyte density, and an existing soil fertility map. The macrophyte map obtained an OA of 93 %. Some parameters such as pH (r = −0.62; R2 = 0.57), effective cation exchange capacity (r = −0.49; R2 = 0.79), Mn (r = −0.71; R2 = 0.6), Zn (r = −0.69; R2 = 0.54), and base saturation (r = −0.7; R2 = 0.93) were influenced by the distance or level of maturation of the avulsion stage in the TRM. Our scattering of soil collections was insufficient to test the terrestrialization hypothesis (2). The study results show that river channel avulsions influence the accumulation of mineral and organic nutrients in tropical floodplain soils, which has implications for fertility and biodiversity.

Differential responses of photosynthesis, yield and soil properties 4 years after a single application of zeolites and biochar in a rainfed olive orchard

AbstractOlive orchards represent a key agricultural system in the Mediterranean Basin. Soil degradation processes associated with unsustainable agronomic practices and climate change could severely impact the sustainability of Mediterranean rainfed olive orchards. In this context, soil amendments are important tools that can be used to enhance soil fertility for sustained environmental quality and plant performance. In this study, a field trial was conducted for 4 years in olive tree (Olea europaea L.) to assess the effects of a mineral fertilizer compound and the combination with a single application of zeolites or biochar on the physiological and biochemical performance, tree nutritional status, crop yield and soil chemical and biological properties to gain knowledge towards more sustainable management. Our results showed that the addition of zeolites and biochar to mineral fertilizer ameliorated the physiological and biochemical performance, as evidenced by consistent increments of relative water content, stomatal conductance and net photosynthesis and by lower signs of oxidative stress during the periods of greater climate adversity. However, crop yield was not significantly different among soil treatments. On the other hand, soil chemical and biological traits at the surface layer (0–10 cm) have shown different and relevant responses after 4 years of soil amendment application. In fact, zeolite supply stood out as increased pH, extractable K, cation exchange capacity, microbial biomass carbon and microbial biomass quotient and reduced extractable Cu. Furthermore, zeolites induced positive changes in soil enzymatic activity, leading to increases in 10 enzymes involved in C, N and P cycles. In contrast, the effects of biochar on soil properties were much more reduced, given that it decreased the microbial biomass nitrogen and enhanced the activities of three P‐cycle enzymes. In summary, our data demonstrated that both soil amendments can be an interesting complement to mineral fertilization, in order to increase trees' resilience under rainfed conditions and to promote soil health, although the use of zeolites appears to be a more promising strategy because of the induction of higher soil sustainability.

Effects of organic amendments, biofertilisers and biodynamic preparations on soil properties and leaf nutrient concentrations in grapevine

ABSTRACT Excessive and unbalanced use of chemical fertilisers can lead to depletion of physical and chemical properties of the soil and have negative impacts on the environment. This investigation was conducted at Mizoram University, Aizawl, Mizoram, India and aimed to evaluate effects of organic amendments, biofertilisers and biodynamic preparations on soil properties and leaf nutrient status of grapevine. The experiment was laid out in randomised block design with 14 treatments consisting of different combinations of organic amendments, biofertilisers and biodynamic preparations viz. farmyard manure (FYM), vermicompost (VC), pig manure (PIM), neem cake (NC), Azospirillum, phosphate solubilising bacteria (PSB), potash solubilising bacteria (KSB), Trichoderma harzianum, cow pat pit (CPP) and biodynamic preparations BD500 and BD501. The results demonstrated that the use of organic amendments in combination with biofertilisers and biodynamic preparations enhanced leaf nutrient status as well soil properties in the vineyard. Among all the tested combinations, the highest concentrations of Mn, Zn, chlorophyll a, b and total chlorophyll in the leaves and concentrations of soil organic carbon, inorganic carbon, total carbon, total N, available N, P, K, Mn and Zn, cation exchange capacity (CEC) and abundance of bacteria and Actinomycetes in the soil were recorded with application of PIM + Azospirillum + PSB + KSB + T. harzianum + CPP + BD 500 + BD 501. This treatment was therefore recommended as a suitable option to meet the demand for long-term maintenance of soil fertility as well agroecosystem conservation and sustainability.

Land use and topographic controls on soil chemical properties in some selected sites of the North West Region of Cameroon

ABSTRACT Land use change affects soil forming processes and modifies site conditioning factors. This paper evaluates land use and topographic controls on soil chemical properties in selected sites of the North West Region of Cameroon. Three topographic zones comprising; low altitude (<1200m), mid-altitude (1200-1500m), and high altitude (˃1500m), under four land use types were studied. 60 soil samples were collected on plots of 30m2, at 0-20cm depth and subjected to chemical analyses. Significant relationships between variables were established via ANOVA and Pearson’s correlation tests. The results revealed significant correlation between soil properties at (P<0.05) and (P<0.01) confident intervals between soil properties with land use and elevation classes. A significant decline (P< 0.01) was observed in the concentrations of pH, Base Saturation (BS), Cation Exchange Capacity (CEC), Total Nitrogen (TN), Soil Organic Carbon (SOC), Soil Organic Matter (SOM), Phosphorus (P) and exchangeable bases in farmlands. Soil chemical properties showed variations across land uses and elevation classes. Soil pH, BS, CEC, SOC, SOM, P, and Ca2+ were statistically significant with topographic variations, while BS, CEC, TN, and Mg2+ varied significantly with land use. Exchangeable potassium (K+) and exchangeable sodium (Na+) showed no significant variations with land use and topographic position.

A Comparative Study of Soil Fertility in Organic, Semi-Organic, and Conventional Rice Field Farming Systems (Case Study: Nguntoronadi District, Wonogiri, Indonesia)

The soil fertility of rice fields is closely related to rice crop production. The research aims to identify soil fertility under different rice field farming systems, find the key factor of soil fertility, and recommend strategies to improve soil fertility based on the key factor. The research was conducted in Nguntoronadi District, Indonesia, on conventional, semi-organic, and organic rice fields. The research was an exploratory descriptive survey through a field survey approach and soil chemistry and physics analysis. Soil sampling was conducted in 12 Land Map Units (LMUs) with three replicates using purposive sampling methods. Observation indicators include soil pH, organic C, total N, C/N ratio, available P, available K, exchangeable Ca, exchangeable Mg, Cation Exchangeable Capacity (CEC), Base Saturation (BS), Aluminum saturation, soil texture, and worm population density representing soil chemical, physical, and biological properties. Soil fertility is determined using Principal Component Analysis (PCA) and scoring based on the category. The research results show that the level of soil fertility under various rice field farming systems was included in the moderate with ranges of 0.53-0.70, and organic farming has the highest soil fertility. The key factors of soil fertility include pH, organic C, available P, available K, Ca-dd, CEC, and Aluminum saturation. The appropriate management direction is the addition of organic fertilizer in the planting period.

Étude de l'adsorption des ions de Nickel sur des argiles naturelles locales dans les effluents hydrométallurgiques

This research focuses on the treatment of hydrometallurgical effluents, specifically studying the adsorption of metallic ions such as Nickel, Copper, Cobalt, Mercury, and lead on natural clays from the Democratic Republic of Congo (DRC). Twelve clay samples, six activated with a strong acid and six non-activated, were characterized using various techniques including X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, X-Ray Fluorescence, Transmission Electron Microscopy, and chemical dosage. The characterization revealed that the clays are mixed with several clayey minerals, enriched in aluminum silicate; contain absorption and water retention sites, and exhibit heterogeneities at the interfaces between grains and exchangeable ions. Activating the clays increased their cation exchange capacities, removed impurities, and increased pore size and specific area. Two aqueous solutions were used in the experiments: a laboratory-prepared nickel sulfate solution and a hydrometallurgical aqueous solution from a factory, both initially containing 15 mgL-1 of Ni2+ ions. Results showed that the adsorption of Ni2+ ions increased with the quantity of clay in the solution. The activated clays adsorbed more ions than non-activated clays at the same Ni2+ ion concentration. Additionally, adsorption was weaker in the hydrometallurgical solution compared to the nickel sulfate solution, suggesting competition from other metallic ions. The optimal adsorption occurred with chemically activated clays containing high Na+, Fe2+, and Al3+ ion content and low K+ ion content. The Hill-Langmuir model was used to describe the adsorption results, revealing that minimal quantities of activated clay were needed to adsorb a large quantity of Ni2+ ions in the solution, whereas large quantities of non-activated clays were insufficient. In conclusion, the research demonstrates the potential of natural clays from the DRC to adsorb metallic ions from hydrometallurgical effluents, providing insights for effective treatment methods in the future. The model revealed that the clay samples A2a clay, A6a and A3na have the very elevated reactional sites concentrations.

Assessing the Impact of Gully Erosion on Soil Fertility in Ankpa Local Government Area of Kogi State

This study explores the impact of gully erosion on soil fertility in Ankpa Local Government Area, Kogi State, Nigeria. A systematic sampling procedure was employed, involving composite soil samples collected at varying depths (0 – 15 cm, 15 – 30 cm, and 30 – 45 cm). Physical and chemical analyses were conducted on these samples, and statistical analysis, utilizing the coefficient of variation (CV), was applied to the data. Results revealed that sand fractions dominated the surface horizons in all pedons studied, ranging from 74.10% to 80.60%. Silt content showed irregular accumulation down the profile depth, ranging from 5.00% to 6.00%. Clay content, ranging from 14.40% to 20.40%, decreased down the profile depth, indicating potential illuviation and pedoturbation processes. Bulk density values within the rooting zone were optimal for plant production. Particle size distribution suggested that the studied soils fell within the sandy loam textural class, except for one profile identified as sandy clay loam. Soil pH (H2O) and pH (KCl) indicated highly acidic conditions. Organic carbon content was critically low, and total nitrogen levels were also critically low according to fertility ratings. Available phosphorus ranged from low to moderate levels, while calcium dominated the exchange complexes. Magnesium levels were high, potentially contributing to unstable soil structural arrangements. Potassium content was categorized as moderate, while sodium content was rated moderate with implications for soil fertility. Cation Exchange Capacity (CEC) was moderate, reflecting the general low organic matter content in the soil series. Base saturation indicated high values, suggesting minimal leaching of plant nutrients. In conclusion, the study identifies the complex interplay of soil properties affected by gully erosion, emphasizing the need for targeted interventions to improve soil fertility.

EFFECTS OF TEA (CAMELLIA SINENSIS) CULTIVATION ON SOIL QUALITY IN THE LAM DONG, VIETNAM

The objectives of the study were to assess soil quality and its relationship to the sustainability of tea cultivation in the Lam Dong, Vietnam. Overall soil quality declined with increasing age of the tea plantations as evidenced by decreases in soil OC, total N, K and S, available P and K, mean weight diameter of aggregates. As well, total P, bulk density and mechanical resistance increased with increasing cultivation intensity. Because these soil properties were sensitive to cultivation effects, they were considered to be good indicators of soil quality. Soil properties that were less sensitive to change, and limited as soil quality indicators included texture, clay mineralogy and sesquioxides, and effective cation exchange capacity. Soil quality changes were greatest during the first 10 years of cultivation and were generally greatest in the surface 0- to 40-cm of soil. Soil and crop management factors were considered to be the most important factors affecting soil quality. Decreases in long-term crop yields were found to correspond with decreases in soil quality. In terms of crop productivity, the most important soil quality indicators (based on a multiple regression analysis) were OC, available P, total K and PAWC. Economic analysis of the yield and production cost data indicated that, under current conditions, tea cultivation in the Lam Dong province is sustainable for periods of about 20 years. Thus, measured values of soil quality indicators in the 20-yr tea soils were considered to represent the "critical levels" for economic sustainability of tea cultivation.

Biostimulation potentials of spent milled maize and cowblood on a crude oil polluted soil

This study was carried out to investigate the biostimulation effect of the application of spent milled maize and cow blood to crude oil polluted soil. The treatment groups were; Control (0 L crude oil (CO) + 0 kg spent milled maize (SMM)), group 1 (1 L CO + 1 kg SMM + 1 L cow blood), group 2 (2 L CO + 2 kg SMM) and group 3 (5 L CO + 5 kg SMM). The experiment was laid out in a completely randomized design A total of four treatment combinations were applied and replicated 3 times giving a total of 48 plots.The physicochemical properties and bacterial load of the soil were determined before pollution, two weeks after pollution, four weeks and eight weeks after remediation. The results for physicochemical properties of soil indicates a decrease in total organic carbon and nitrogen while there was an increase in the levels of cation exchange capacity, phosphorus and electrical conductivity after crude oil pollution. The mean levels of total petroleum hydrocarbon and polycyclic aromatic hydrocarbon reduced after the pollution. The application of the spent milled maize and cow bloodwere observed to improve the physicochemical properties of soil. There was also an increased bacterial count for the treated groups compared to the control; the values ranged from 1.3 x 103cfu/g to 1.24 x 108cfu/g. The identified bacteria were Flavobacterium, Pseudomonas, Bacillus, Micrococcus, Proteus, Clostridium and Nocardia species.Generally, this study has revealed that spent milled maize and cow blood are effective in the restoration of crude oil polluted soil.

Research on the Transformation Mechanism of Soil Cadmium Fractions under the Conditions of Freeze-thaw and Crude Oil Contamination in Wetlands in the Songnen Plain, China

Environmental changes can significantly affect heavy metals behave in soil. Currently, we know little about the impact of crude oil contamination on heavy metal fractions in soil, with few studies available on heavy metal fraction transformation under the composite action of freeze-thaw and crude oil contamination. In this study, soil samples were collected from the Momoge Wetland in the Songnen Plain. Properties including pH, cation exchange capacity, calcium carbonate, free iron oxide, dissolved organic carbon, microbial biomass carbon, and cadmium (Cd) fractions under freeze-thaw, crude oil contamination, and the two combined (composite action) were analysed. The results show that under freeze-thaw, crude oil contamination, and composite action, soil properties changed significantly; soil water-soluble Cd content significantly increased by 54.17%, 62.50%, and 33.33% from control levels, respectively; soil ion-exchangeable Cd content decreased significantly by 10.90%, 23.73%, and 18.64% from control levels, respectively; soil residual Cd content significantly increased by 80.36%, 94.64%, and 132.14% from control levels, respectively; carbonate-bound, humic acid-bound, Fe-Mn oxide-bound, and strongly organic-bound Cd did not change significantly. Soil dissolved organic carbon, pH, CaCO3, and free iron oxide were significantly correlated with water-soluble, ion-exchangeable, carbonate-bound, and Fe-Mn oxide-bound Cd, respectively. This study provides a theoretical basis for evaluating soil Cd behaves in crude oil contaminated wetlands in cold regions.

Land use change from paddy rice to sugarcane under long-term no-till conditions: increase P balance, soil organic matter and sugarcane productivity

ABSTRACT Expanding sugarcane (SC) cultivation at the expense of paddy rice (PRC) areas led to soil nutrient cycling changes. The study hypothesized that SC straw return and fertilizer application after land use change (LUC) from PRC to SC cropping would increase the soil-crop systems nutrient balance, ultimately enhancing growth, yield, and nutrient use efficiency of SC. In a field study involving a 17-year chronosequence of sugarcane 6 (SC6), 13 (SC13), and 17 (SC17) years after LUC, the nutrient balance dynamics of SC were monitored in comparison with those of PRC. A phosphorus (P) balance increase of 62–102% after LUC increased soil available P (Pav) from 5.2 to 13.6–16.0 mg kg−1. A potassium (K) balance decrease of 47–55% after LUC led to a decrease in soil exchangeable K (Kex) from 102.5 to 96.2–56.8 mg kg−1. Moreover, LUC increased the % sand, soil organic matter (SOM), total mineral nitrogen (N), and total N. In contrast, the % clay, bulk density, cation exchange capacity (CECpH7), and exchangeable calcium (Caex) decreased after LUC. An increase in soil nutrients increased cane yield and nutrient use efficiency with time after LUC. However, further research in different locations and management practices is required for the LUC investigation.

Partial Substitution of Chemical N with Solid Cow Manure Improved Soil Ecological Indicators and Crop Yield in a Wheat–Rice Rotation System

Alternative fertilizers are essential to minimizing the deteriorating effects of chemical fertilizers on soil and water quality/health. Accordingly, the present work investigated the effects of combined organic–inorganic fertilization (COIF) on wheat and rice yields, soil nutrients, and soil Cd accumulation. Hence, seven different treatments were set up: control (CK); conventional fertilization (CF); adequate fertilization (OF); organic fertilizer replacing 25% (T1) and 50% (T2) of OF; and organic nitrogen (N) replacing 25% (M1) and 50% (M2) of OF-N. Overall, significant increases occurred in the yields of COIF crops. Compared with the CF, the highest wheat and rice yields happened in the M1 treatment (with a difference of approximately 18.5%) (p &lt; 0.05). COIF slightly alleviated soil acidification, and improved the cation exchange capacity (CEC) of the study soils. Furthermore, COIF treatments significantly increased the contents of total phosphorus, total potassium, available phosphorus, and available potassium by 6.35 to 16.9%, 3.17 to 10.9%, 5.53 to 28.7%, and 2.6 to 12%, respectively (p &lt; 0.05). Nevertheless, negligible increases took place in the Cd content of COIF soils compared with that of the CK. Altogether, our results concluded that 25% replacement of OF-N by organic N (M1) effectively improved the fertility/ecological sustainability of the study soils.

Assessment of the Quality of Agricultural Soils in Manica Province (Mozambique)

Agriculture is the main economic activity of Mozambique and there is a lack of information about the quality of agricultural soils. In this paper, five soils from the Manica and Sussundenga districts (Manica province) sampled in the years 2021/2022 and 2022/2023 (before and after the rainy seasons) were subjected to an agronomical and environmental chemical analysis to assess their quality, from the fertility and environmental contamination points of view. Standard analytical methodologies from external certified laboratories and local X-ray fluorescence measurements were used. All the studied soils were acidic (pH ranging from 4.5 to 5.4), had no salinity problems (conductivity ranging from 4.2 to 11.8 mS/m), and had a low amount of soil organic matter (0.90% to 1.81%). Soils from the Sussundenga district had a very low cation exchange capacity (CEC) (average of 3.33 cmolc/kg), while that of those from the Manica district ranged from very low to average CEC (3.59 to 13.11 cmolc/kg). Sussundenga soils also had a phosphorous deficiency (values ranging from &lt;20 to 38.5 mg/kg) and there were deficiencies and/or excesses of some macro and micronutrients in all soil samples. Manica soils were contaminated, apparently from geogenic origin, with Cr (280 to 1400 mg/kg), Co (80 mg/kg), Ni (78 to 680 mg/kg) and V (86 mg/kg). Agricultural soil monitoring must be fostered in Mozambique in order to improve food quality and quantity to ensure economic and environmental sustainability.

Nitrogen enrichment does not adversely affect exchangeable bases in rainfed urban arable soils of Kumasi, a tropical West African city

Urbanisation induces nitrogen (N) enrichment in tropical soils. This enhances soil acidification, leading in turn to a decrease in effective cation exchange capacity (CECe) and base saturation (BSe). Here, we investigated if and how these effects of urbanisation-induced N inputs affect the soils of tropical urban agroecosystems. Our aim was to quantify the impact of urbanisation intensity (UI) on total N (TN) contents and stocks, and to detect possible adverse N effects on soil pH, CECe, and exchangeable bases in rainfed urban arable soils of Kumasi, a tropical city in Ghana, West Africa. We analysed 618 topsoil samples (0–10 cm) from arable fields within the urban perimeter, categorised into four classes forming a gradient from low to high UI. For baseline comparison, 9 samples each from both rural arable fields and an urban forest were included. Urban arable soils generally had higher TN levels than their rural counterparts. Among the urban arable soils however, TN levels decreased with increasing UI, possibly as crop production and related N export through harvest intensified. Conversely, increasing UI correlated with increased levels of exchangeable Ca2+, K+, and Na+. No adverse N effect on soil pH, CECe, and BSe was detected. This could be explained with the strong TN-SOC relationship (R2 ≥ 0.9), and an increasingly strong relationship between exchangeable bases and TN and SOC (R2 = 0.5–0.8) with increasing UI. These relationships suggested a major common source of TN, SOC, and exchangeable bases. As the soils are neither chemically fertilised nor limed, these findings supported earlier studies that this source is provided by dumped biodegradable household waste, charred matter, ash, and construction materials. We concluded that soil N enrichment through these materials in Kumasi is accompanied by abundant bases in the same materials, which overcompensate any theoretic acidification. Our findings imply that not only can the fertility of tropical urban arable soils in cities like Kumasi be maintained, but also that the crops and ground water may not be at risk from the mobilisation of trace elements and heavy metals due to the hindered soil acidification.

Comparative analysis and prediction of cation exchange capacity via summation: influence of biochar type and nutrient ratios

IntroductionEnhancing soil cation exchange capacity (CEC) is of paramount importance for sustainable agriculture and ecosystem health. This study investigated the pivotal role of biochar in altering soil CEC and challenges conventional assumptions about universal effects of biochar application.MethodsContrasting biochar types, one with a low ash content of 4.4% (switchgrass-derived biochar, SGB) and the other with a high ash content of 45.9% (poultry litter-derived biochar, PLB) were used. Two experiments treated with increasing biochar application rates were conducted: one without plants and the other grown with ryegrass. Effective CEC (summation method) was determined by two extraction methods: Mehlich-3 (M3) and ammonium acetate (AA).Results and discussionThe SGB decreased CEC by 27% on average (from both experiments) from the lowest to the highest rate of biochar application, while the PLB significantly increased CEC by 91%. This highlights the critical role of biochar properties in influencing CEC dynamics. In the second experiment, ryegrass cultivation revealed the greater importance of the calcium and magnesium/potassium ratio ([Ca+Mg]/K) in the soil CEC than CEC only for plant growth in biochar-amended soils. The ratios for optimum ryegrass production ranged from 82‒86 (M3) and 69‒74 (AA), which was translated to 88:11:1 Ca:Mg:K percent base saturation ratios. Moreover, predictive models for estimation of soil CEC after biochar application were successfully developed based on initial soil and biochar CEC. However, M3 was more reliable than AA for such predictions mainly because it was more successful in predicting nutrient availability from biochar. These models offer a promising tool for informed soil management decisions.ConclusionThis research emphasizes the importance of biochar feedstock, elucidates nutrient ratio effects on plant growth, and provides a practical means to anticipate soil CEC changes post-biochar application.

The Influence of Chemical Fertilizers on the Effectiveness of Biochar in Mitigating Cadmium Mobility in Soil

The focus of this study was to explore how various fertilizers influence the movement of cadmium in soil treated with biochar. The research utilized a strong acid sandy loam soil from Chanthaburi Province, naturally rich in organic matter with moderate cation exchange capacity and low nitrogen, potassium, phosphorus, sulfate, salinity and chloride levels. The soil was purposely contaminated with 50 mg kg-1 of cadmium and treated with biochar derived from water hyacinth through pyrolysis at 450°C for an hour. This biochar displayed moderate alkalinity, high organic matter, phosphorus, potassium, and cation exchange capacity, but low nitrogen content. Analytical techniques like Scanning Electron Microscopy and Fourier-Transform Infrared Spectroscopy were employed to study the surface characteristics of the biochar. The cadmium adding soil was blended with 10% biochar and various chemical fertilizers at a 0.04% ratio. Diethylenetriamine pentaacetate (DTPA) extraction was used to assess the bioavailability of cadmium to plants in the soil, while sequential extraction was conducted to identify the different forms of cadmium present in the soil. The study revealed distinct effects of different fertilizers on cadmium mobility. Fertilizers like 46-0-0 and 0-3-0 caused a transformation of cadmium from stable to less stable forms, increasing the bioavailability of cadmium to plants. Conversely, fertilizers such as 15-15-15, 0-0-50, 0-0-60, and 0-52-34 shifted cadmium from less stable to more stable forms, resulting in decreased cadmium extracted by DTPA. Other fertilizers showed no significant impact on cadmium mobility in the soil. A stepwise linear regression analysis highlighted that nitrogen content, potassium content, and electrical conductivity were influential factors affecting cadmium mobility.

The role of intrinsic soil properties in the compressive strength and volume change behavior of unstabilized earth mortars

Despite the growing interest in earthen construction, there is critical lack of reliable experimental data on the soil properties which mostly affect the engineering characteristics of the dried building material. Therefore, the main objective of this research was to explore the influence of some of these properties, namely clay fraction content, Specific Surface Area (SSA), Cation Exchange Capacity (CEC), chemical and mineralogical composition and various forms of iron and calcium carbonate on earth mortars. The initial trigger for this research was the extraordinary compressive strength of four earth mortars prepared with different soils. So, these four soils, along with seven others from previous research, were thoroughly examined using soil science techniques to investigate the link between soil properties and compressive strength and linear shrinkage of earth mortars. A relationship between the compressive strength to CEC ratio and dry density was found, highlighting the decisive role of clay activity as expressed by CEC, in earthen materials properties. According to linear regression and dominance analysis, the strongest correlation was exhibited by SSA followed by CEC, demonstrating that compressive strength is largely dependent on these two properties. Less strong correlation was found for clay fraction content, while poorly ordered/amorphous iron oxides were found to correlate with strength and shrinkage, but their contribution requires further research. Regarding the mineralogical properties, it was found that the mortars that achieved the highest strengths contained poorly crystalline smectite clays. Finally, even significant differences in soil chemical composition did not necessarily lead to different mortar properties.

Recent Advancements in Biochar and its Composite for the Remediation of Hazardous Pollutants

Abstract: Biochar has garnered considerable attention in recent times due to its potential uses in the environmental field. In this study, we comprehensively examine and condense information on biochar production, characteristics, and adsorption mechanisms, with a focus on its economic applications for remediating hazardous contaminants. Our assessment is based on over 200 publications from the past decade. Biochar, a carbon-rich material, can be derived from various organic waste sources, such as food waste and urban sewage sludge. Researchers are particularly interested in biochar due to its high carbon content, cation exchange capacity, substantial specific surface area, and stable structure. We investigate how the physical and chemical properties of biochar may vary based on the feedstock used, providing a comprehensive overview of biochar and its composition for pollution remediation. The review also discusses common techniques such as gasification, hydrothermal carbonization, and pyrolysis used to produce biochar. We analyze current research on the mechanisms involved in pollutant treatment using biochar and its composites while also addressing future directions in biochar research.

Lead bioaccessibility and commonly measured soil characteristics in Detroit, Michigan

Historical and contemporary use of lead (Pb) in gasoline, paints, and industry have led to its concentration in urban soils, presenting a human health risk, with disproportionate impacts on children living in urban areas. Contaminated soil is one of the major contributors to child Pb exposure. While many residents practicing urban agriculture have their soil tested to determine the amount of soil total Pb present, this measure does not provide a direct indicator of soil Pb bioaccessibility (used to predict bioavailability). Because bioavailability is ultimately necessary to determine the exposure risk, we aimed to gain a more refined understanding of Pb risk using measurements commonly performed as part of typical agricultural soil tests. Accordingly, we sampled soils from 142 residential parcels located in Detroit, MI. Soils were evaluated for: pH, organic matter content, cation exchange capacity, phosphorus, sulfur, calcium, potassium, magnesium, and sodium and total and in-vitro bioaccessible (IVBA) Pb. Detroit soil IVBA Pb ranged from 4.5% to 81%, with a mean of 39%. Total Pb, organic matter (OM) content and soil pH were found to be the most important predictors of Pb bioaccessibility. Soils typically had a relatively low OM content (mean of 5%) however, samples with higher OM content had lower IVBA (e.g., the IVBA was 15.2% smaller in soils with 7.5% OM). Soils were typically slightly basic (mean of 7.8); however, samples with pH closer to neutral had lower IVBA (e.g., the IVBA was 11.6% smaller in soils with a pH of 7.3). The proximity of soil sampling locations to former smelter locations was also found to influence Pb bioaccessibility, with samples closer to former Pb smelter sites having a somewhat higher average IVBA. Results suggest increasing soil OM content in urban soils will reduce Pb bioaccessibility. Building soil OM would therefore improve both soil fertility and decrease soil Pb bioaccessibility, imparting a predicted decrease in exposure risks.

Influence of soil nutrients on net primary productivity in post-mining forests in the Colombian Pacific

ABSTRACT Tropical forests have the highest rates of net primary productivity (NPP) in terrestrial ecosystems and, therefore, may contribute significantly to the mitigation of global climate change. Although NPP is influenced by soil fertility, and recently, in some regions, mining activity in forest ecosystems has intensified. Little is known about how soils determine the restoration of NPP in forests degraded by mining. We evaluated the influence of soil nutrients on wood NPP of post-mining forests in the biogeographic Chocó region (Colombia), with emphasis on the effects of nitrogen (N) and phosphorus (P) limitations in post-mining forests under successional stages of 12-15 or 30-35 years. For this, permanent plots were established in secondary post-mining forests in Jigualito (Colombian Pacific), the wood NPP (accumulated and current) was evaluated, and it was related to soil properties such as organic matter (OM), acidity, Al, total N, available P, magnesium (Mg), potassium (K), calcium (Ca), and texture. An accumulated wood NPP of 0.72 t ha -1 yr -1 was recorded in post-mining forests 12-15 years old. Meanwhile, in post-mining forests of 30-35 years, the accumulated wood NPP was 6.52 t ha -1 yr -1 . The current wood NPP was 4.25 t ha -1 yr -1 in post-mining forests with 30-35 years of recovery. Accumulated NPP positively correlated with soil OM, total N, Ca, Mg, and effective cation exchange capacity–ECEC in post-mining forests. In post-mining forests, a slow recovery of the wood NPP was denoted in the first years. Soil nutrients determined the wood NPP, and a multiple limitation of nutrients with the succession was observed, which corroborates the need to restore the degraded ecosystem in the region.