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Abstract: This study was conducted under greenhouse conditions to evaluate the potential use of SPS as a fertilizer, amendment and/or liming agent for wheat (Triticum aestivum L.). Two representative Mediterranean agricultural soils, a Cambic Arenosol (cmAR) and a Cromic Cambisol (crCM) were used. Treatments included four sludge rates ranging from 0 to 40gkg−1 (equivalent of 0, 38, 88 and 120Mgha−1). A significant increment in soil pH, organic carbon, N total, available P and exchangeable K were observed in both soils. Sludge application significantly increased N and decreased Zn, Mn and Cu concentrations in wheat. Wheat grain yields were reduced by 33% and 37% when 120MgSPSha−1 was applied to cmAR and crCM soils, respectively, due apparently to unavailability of Mg. However, straw yields, with much lower Mg requirements, increased significantly with SPS rates. Secondary pulp mill sludge seems to be a potential source of organic matter, N, P, K and a potential soil amendment liming agent for acid soils, when appropriate supplemental fertilizer was provided. For grain crops grown in these soils, addition of Mg is required for proper nutrient balance. [Copyright &y& Elsevier]

Abstract: In the last few years solidification/stabilisation of acidic soils polluted by heavy metals with low-cost sorbents has been investigated. Paper mill sludges are produced in large amounts and their disposal is a serious environmental problem. The possibility was therefore studied of using paper mill sludge as a stabilizer to reduce the bioavailable metal forms in polluted soils and thus the transferability of metals to plants (barley). We first investigated the sorbing properties of paper mill sludge for Zn(II) and Pb(II) and then their fractionation both in a polluted soil and in the same soil amended with paper mill sludge in order to check the decrease in mobile forms. Finally in both soils we tested the uptake of two metals by common barley in order to assess the performance of soil remediation from an ecological point of view. The addition of paper mill sludge to a soil contaminated by lead and zinc induces a decrease in the mobile forms of both metals, probably due to the presence in sludge of organic matter and kaolinite, which are able to bind the metals very strongly. The decrease in the mobile forms, which are the most readily available for uptake by plants, corresponds to a decrease in plant uptake. [Copyright &y& Elsevier]

Soil microbial communities, which play a key role in the provision of essential ecosystem services, are significantly influenced by several physical and chemical soil properties that may change with land management. This study explores the effect of different land cover types (coniferous tree stands, broad-leaved stands, shrublands, pastures/grasslands and croplands) on physical, chemical and microbial properties (all contributing to soil health) in southern European areas under moderate-high desertification risk selected in Italy, Spain and Portugal. In sites that differ in land cover, we determined microbial biomass (C mic), activity and indices of microbial metabolism including C mic /C org ratio, metabolic quotient (qCO 2) and quotient of mineralization (qM). Soil physical and chemical properties were also measured, comprising bulk density (BD), water content (WC), pH, cation exchange capacity (CEC), total organic C (C org) and some of its labile fractions, extractable C (C ext) and mineralizable C (C min), total N content and C/N. Results showed that land cover type played a strong role in determining magnitude of microbial variables with biomass and activity being higher under coniferous tree cover than in other land covers, according to trends in WC, CEC, C org , C ext , C min , N, C/N. Compared to land cover, aridity index had lower effect on investigated variables. In comparison to sites with higher C org content, sites with lower C org content (most croplands) tended to lose C more rapidly, as suggested by high qM values, except for Spanish acidic soils. Therefore, urgent actions must be taken to counteract the tendency of C-poorer soils to lose C, promoting land cover types that facilitate soil recovery by ensuring denser and more continuous soil cover over time. We also identified a minimum set of soil variables that provide information on soil health changes in both short term (microbial variables) and longer term (physical and chemical variables) in areas under desertification risk. [Display omitted] • Land cover is a key factor affecting soil health in areas at desertification risk. • Coniferous cover had the best effect on soil microbial, physical and chemical variables. • Croplands, grasslands, shrublands and broad-leaved soils differed at a lesser extent. • Soils poorer in organic C tended to lose C more rapidly than richer soils. • A minimum data set of soil health indicators was proposed. [ABSTRACT FROM AUTHOR]

Soil acidification is a natural phenomenon that human activity can accelerate or manage. Acid soils limit plant growth by reducing nutrient availability and causing aluminum toxicity, significantly reducing crop production. Liming has proven efficient for increasing crop yield on acidic soils. Knowledge is required on the effect of liming on the soil pH dynamics to find the suitable material, application rate, timing, and method. The objective of this study was to develop a prediction model of soil pH temporal variations after lime application using data from the literature. A database was built from research results extracted from 16 scientific papers that provided data on soil acidity changes over time under different liming treatments. Machine learning (ML) was used to predict soil pH dynamics from eight predictive parameters: rate of application, time since application, neutralizing value (CCE), grind fineness (D50), pH measurement depth, soil acidity (pH prior to liming), the type of solution used for pH measurement (water or CaCl 2) and the soil:solution ratio used to measure pH. Since soil pH fluctuates with seasons, all pH values were expressed as difference between the actual pH value and that of an unlimed control (ΔpH). The Random Forest (RF) algorithm was tested to predict ΔpH over time. On testing, we obtained an R2 between measured and predicted ΔpH values of 0.881 and an RMSE of 0.230. These results are excellent, considering the heterogeneity in soils, liming materials, and pedoclimatic conditions found in the 16 papers. The primary factors influencing ΔpH, ranked by their impact are application rate, time elapsed post-application, and lime characteristics including its grind fineness and neutralizing value. • Random Forest robustly predicts soil pH change over time following lime application. • The predictors are: rate, neutralizing value, particle size, depth, and initial pH. • The model predicts that, on average, lime increases soil pH for 82 weeks. • Machine learning models are promising tools in managing liming practices. [ABSTRACT FROM AUTHOR]

Biochar is produced from organic materials by pyrolysis specifically for soil improvement. Interactions with beneficial outcomes between biochar and soil can arise within a short time but it is uncertain whether the effects are similar in all soil types and at different time-scale. The objective of this study was to evaluate the short-term and mid-term effects of biochars from different feedstocks (grain husks and paper fibre sludge, post-treated grain husks and paper fibre sludge, woodscreenings) on the soil physico-chemical, biological and ecotoxicological properties. As part of a complete scale-up technology, aiming improvement of an acidic sandy soil, a 12-month microcosm experiment was conducted with combined application of biochars, compost and fertilizer. The applied multiparameter approach made possible the selection of the most optimal treatment. All the three biochars had favourable influence on the soil, but the effects were different in terms of extent and time. Although the biochar from woodscreenings had not the most promising short-term effects, but combined with fertilizer at 0.5 w/w% biochar rate it was the most favourable treatment after 12 months. The grain husk and the paper fibre sludge biochar at 1 w/w% rate could also efficiently improve soil parameters and functions. [ABSTRACT FROM AUTHOR]

The use of peracetic acid (PAA) in advanced oxidation processes has gained significant attention recently, but the knowledge of activating PAA to degrade polycyclic aromatic hydrocarbons (PAHs) is limited due to the variety and selectivity of reactive substances in PAA oxidation system. This paper presented the first systemically study on the degradation of PAHs by PAA activation in soil. It was found that heat-activated peracetic acid (heat/PAA) was capable of degrading phenanthrene (PHE) efficiently with degradation efficiency > 90 % within 30 min. Experimental results demonstrated that a series of reactive oxygen species (ROS) including organic radicals (RO•), hydroxyl radicals (HO•) and singlet oxygen (1O 2) were generated, while acetylperoxyl (CH 3 C(O)OO•) and acetyloxyl (CH 3 C(O)O•) radicals were primarily responsible for PHE degradation in soil. Further analysis shows that polymerization products such as diphenic acid, 2′-formyl-2-biphenylcarboxylic acid and other macromolecules were dominant products of PHE degradation, suggesting polymerization driving PHE degradation instead of the conventional mineralization process. Toxicity analysis shows that most of the polymerization products had less toxicity than that of PHE. These results indicate that PAA activation was a highly effective remediation method for PAHs contaminated soil, which also provided a novel mechanism for pollutant degradation with the PAA activation process for environmental remediation. [Display omitted] • The degradation of PAHs in soil by heat-activated peracetic acid was systematically studied. • Heat-activated peracetic acid was capable of degrading phenanthrene efficiently within 30 min. • CH 3 C(O)OO• and CH 3 C(O)O• were primarily responsible for phenanthrene degradation in soil. • Polymerization products and other macromolecules were dominant products of phenanthrene degradation. [ABSTRACT FROM AUTHOR]

Biochar produced from a wide range of organic materials by pyrolysis has been reported as a means to improve soil physical properties, fertility and crop productivity. However, there is a lack of studies on the complex effects of biochar both on the degraded sandy soil physico-chemical properties and the soil biota as well as on toxicity, particularly in combined application with fertilizer and compost. A 7-week microcosm experiment was conducted to improve the quality of an acidic sandy soil combining variations in biochar types and amounts, compost and fertilizer application rates. The applied biochars were produced from different feedstocks such as grain husks, paper fibre sludge and wood screenings. The main purpose of the microcosm experiment was to assess the efficiency and applicability of different biochars as soil amendment prior to field trials and to choose the most efficient biochar to improve the fertility, biological activity and physical properties of acidic sandy soils. We complemented the methodology with ecotoxicity assessment to evaluate the possible risks to the soil as habitat for microbes, plants and animals. There was clear evidence of biochar-soil interactions positively affecting both the physico-chemical properties of the tested acidic sandy soil and the soil biota. Our results suggest that the grain husk and the paper fibre sludge biochars applied to the tested soil at 1% and 0.5 w / w % rate mixed with compost, respectively can supply a more liveable habitat for plants and soil living animals than the acidic sandy soil without treatment. [ABSTRACT FROM AUTHOR]

Public concerns over environmental protection have increased after Fukushima accident. The soil-plant transfer factor (Fv) is a critical parameter for environmental risk assessment. 137Cs Fv values determined in acid Brazilian soils could be two orders of magnitude higher than Fv values measured in soils affected by the Chernobyl accident. This paper studied the behaviour of 90Sr in Brazilian soils where very few 90Sr Fv data is available. All classes of studied soils (Ferralsol, Acrisol and Nitisol) showed that more than 80% of total 90Sr in soils remains potentially mobile, mainly at the bioavailable phase, more than 2 years after soil contamination in an experiment conducted in lysimeters. Higher 90Sr Fv for maize and cabbage was observed in the acid soils with low content of exchangeable Ca, lower Fv values occurred at Nitisol, the subtropical soil type. It seems that the behaviour of 90Sr in these soils are mainly controlled by ionic competition mechanisms occurring for root uptake and sorption sites, with stable Sr and major nutrients (Ca, Mg and K). The mineralogy also seems to play a relevant role, since goethite rich clay soil presented 90Sr Fv values higher one or two orders of magnitude than 90Sr Fv values observed at clayed soil goethite rich with trace of vermiculite, for all studied crops. The high rate of 90Sr migration down the soil profiles observed for the studied soils during the 2 first years after contamination suggests a high rate of transfer to groundwater, even transfer to leafy crop group can be also a relevant pathway. In the present study, maize, among other plant species, presented the lowest Fv values, even when compared with maize cultivated in temperate soil. Our results suggest that stable Sr may not be a very good analogue of 90Sr for determining plant Fv values: geometric mean of stable Sr Fv for maize was Fv maize = 6.3E-1 ± 2.1E0 (n = 8) and for 90Sr was Fv maize = 1.8E-2 ± 2.5E0 (n = 16), geometric mean of stable Sr Fv for cabbage was Fv cabbage = 1.4E0 ± 3.9E0 (n = 17) and for 90Sr was Fv cabbage = 7.9E-1 ± 4.4E0 (n = 18). [Display omitted] • Transfer of 90Sr and stable-Sr was studied in Brazilian soils. • 90Sr in Brazilian soils (Ferralsol, Nitisol, Acrisol) had a high potential mobility. • Mineralogy plays a key role in determining 90Sr availability for plant uptake. • Stable-Sr is not a good analogue for 90Sr plant uptake. • A high rate of 90Sr migration down the soil profile was observed. [ABSTRACT FROM AUTHOR]

Sustained high yields of tea rely on the supply of nitrogen (N) from soil reserves, typically maintained by N fertilisation from inorganic or organic sources. This paper describes how soil N levels, including the effects of soil organic content and pH, were developed and incorporated into a crop yield simulation model called CUPPA-Tea. The nitrogen dynamics are presented in terms of i) the initial nitrogen stocks, ii) the addition of nitrogen to the system, iii) the uptake, use and loss of nitrogen by tea plants, and iv) nitrogen flows within the soil. CUPPA-Tea was then calibrated and validated using measured tea yields from Tanzania and Kenya. After integrating a wide range of nitrogen algorithms, the model explained 79% of the variation in annual yields within a nitrogen and irrigation experiment in Tanzania and a fertilizer experiment in Kenya. The slope of the relationship was 0.84 and 0.73 respectively, the root mean square error was 660 kg ha−1 and 507 kg ha−1, and the modelling efficiency was 0.77 and 0.75 respectively. The model predicted that in the absence of N application, tea yields would be higher from a site with a high rather than a low soil organic content. By contrast, at high levels of mineral N application, the yield response in the model was not sensitive to the soil organic content. Hence within the model, a site in Tanzania with a low soil organic content of 1.6% showed a greater yield response to applied mineral N than a site in Kenya where the soil organic carbon was 4.0%. The model also predicted small losses of N from the cropping system through denitrification and leaching due to the acidic soil conditions (pH < 4.5) and an assumed tea rooting depth between 300 and 500 cm. In Tanzania, irrigation was predicted to result in around 10% higher nitrogen uptake than under unirrigated conditions. The use of the CUPPA-Tea model can be useful in supporting decision making and improving the accuracy of tea yield estimates, as well as predictions of N fate within the soil-plant-atmosphere continuum. [Display omitted] • N dynamics, including the effects of soil organic content and pH, were developed and incorporated into the CUPPA-Tea model. • The resulting model explained 79% of the variation in tea yields from experiments in Tanzania and Kenya. • Under no N fertilizer, the model predicted greater yields in a site with a high rather than a low soil organic content. • Minimal N losses due to volatilisation, denitrification, and leaching were predicted (at pH 4.0–4.5 and rooting depths 3–5 m) • CUPPA-Tea was also used to identify the financially optimum N fertilizer application rate in pruned and unpruned tea. [ABSTRACT FROM AUTHOR]

Classification of fields into management zones based on variability of soil fertility parameters is under use in precision agriculture. The study was conducted in west Wollega zone of Ethiopia covering nearly 40 km2 of agricultural land, with the aim to explain variability of soils in the field, classify soils into mapping units and produce a map of these soils at a scale of 1:10000 using geostatistics. In this paper, soil mapping units (SMUs) were interchangeably used with management zones. Ten SMUs were identified in the study site. The SMU mean pH value varied between 5.3 in the SMU6 and 6.4 in the SMU7. Variation in soil texture, pH, exchangeable acidity, exchangeable potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), cation exchange capacity (CEC), organic carbon (OC), total nitrogen (TN), and plant available phosphorus (AvP), were observed within and among SMUs. Variability of soil parameters ranged from 1.06% (Na) in the SMU5 to 172.94% (AvP) in the SMU8. The OC and AvP content of all SMUs were found in the very low and low critical ranges. Intensive grid sampling had helped to produce digital soil maps and exposed soil heterogeneity across the landscape. We suggest that classification of fields into management zones was a remedy to low crop production occurred from uniform applications of nutrients and chemical amendments to significantly varying soils. • Digital soil maps aid variable rate technology and site-specific management soils. • Geostastical models are used to show soil-environment interactions. • Acid soils have a wide range of nutrient deficiencies and imbalances. [ABSTRACT FROM AUTHOR]

Aluminum (Al) is the most prevalent element in the earth crust and is toxic to plants in acidic soils. However, plants can address Al toxicity through external exclusion (which prevents Al from entering roots) and internal detoxification (which counterbalances the toxic-Al absorbed by roots). Nowadays, certain categories of exogenously added regulatory factors (EARF), such as nutritional elements, organic acids, amino acids, phytohormones, or biochar, etc. play a critical role in reducing the bioavailability/toxicity of Al in plants. Numerous studies suggest that regulating factors against Al toxicity mediate the expression of Al-responsive genes and transcription factors, thereby regulating the secretion of organic acids, alkalizing rhizosphere pH, modulating cell wall (CW) modifications, improving antioxidant defense systems, and promoting the compartmentalization of non-toxic Al within intracellular. This review primarily discusses recent and older published papers to demonstrate the basic concepts of Al phytotoxicity. Furthermore, we provide a comprehensive explanation of the crucial roles of EARF-induced responses against Al toxicity in plants. This information may serve as a foundation for improving plant resistance to Al and enhancing the growth of susceptible species in acidic soils. And this review holds significant theoretical significance for EARF to improve the quality of acidic soils cultivated land, increase crop yield and quality, and ensure food security. [Display omitted] • EARF influences rhizosphere pH and Al availability, reduces its absorption by root. • EARF regulates organic acids secretions in the tolerance to Al toxicity. • EARF modulates Al toxicity by reducing Al deposition in cell wall. • EARF protects Al-induced inhibition by regulating antioxidant defense system. • EARF chelates and separates Al to vacuoles to reduce its toxicity. [ABSTRACT FROM AUTHOR]

Acid mine drainage and acid sulfate soils are common consequences of disturbing earth materials containing pyrite and other sulfide-bearing minerals. In order to predict the acid-producing potential of geologic layers in eastern US coal mining regions, Acid-Base Accounting (ABA) was developed by researchers at West Virginia University. The objective of this paper is to demonstrate the use of this method and its interpretation as a prediction tool, and to evaluate its accuracy from literature sources. ABA is an analytical procedure that provides an assessment of the acid-producing and acid-neutralizing potential of soils, sediments and rocks prior to coal mining, highway construction, and other large-scale earth-moving excavations. ABA includes techniques that measure the reactive sulfur content (which is converted to the acid-producing potential, Maximum Potential Acidity or MPA) and the reactive carbonate content (which is converted to acid-neutralizing potential, Neutralization Potential or NP). These two quantifiable properties in ABA are primarily used to predict the quality of drainage and soil quality by subtracting MPA from NP, resulting in a net NP value (either positive or negative). If the MPA value is higher for the sample (negative net NP), the rock sample is predicted to produce acidic drainage upon weathering and leaching. If the number for NP is higher (positive net NP), the rock is predicted to produce alkaline drainage. Other parameters such as rock type, color and paste pH help to refine the interpretation and prediction of net NP. After passage of laws requiring an assessment of surface mining on water quality, ABA became the preferred method to predict post-mining water quality, and permit decisions for surface mines are largely based on the net NP values of ABA. With this information, mining plans are developed which may include mixing overburden materials during mining and reclamation or removing acid-producing materials from the site, selective handling of these materials and placing in specific areas within the backfill, and amending these acid materials with alkaline material. ABA has proven to be a good tool to predict overburden quality that allows the application of prevention procedures to alleviate post-mining water and soil quality problems. Studies comparing the post-mining water quality with predictions made by ABA have confirmed the utility of ABA for permit decisions, pre-mine planning and reclamation practices. [ABSTRACT FROM AUTHOR]

Soil physiochemical properties play a vital role in bioaccessibility-based health risk assessment as it can determine the bioaccessibility and the true risk of potentially toxic elements in soil. However, the effects of soil properties on bioaccessibility still remains unclear. In this paper, 17 of the 1454 literatures with 474 samples were identified, screened and reviewed for exploring the correlation between soil physicochemical properties and lead bioaccessibility (BAc Pb) through a meta-analysis approach. Five soil physicochemical parameters including pH, SOM, Clay, CEC and T-Pb were systematically analyzed using Principal component analysis, Pearson correlation analysis and survival analysis. The results showed that pH of simulated gastric juice is a major source of heterogeneity of the correlation between soil pH and BAc Pb. In the gastric phase, the effect of alkaline soil on high BAc Pb (BAc >50%) is more sensitive, and the effect of acidic soil on low BAc Pb (BAc <50%) is more sensitive. However, in the small intestinal phase, soil pH displays little impacts on BAc Pb in acidic, alkaline and neutral soils. Although three principal components explained 66.2% and 64.9% of the total variance of the urban, agricultural, and mining soils in gastric and small intestinal phases, respectively, there was no strong evidence that soil type can influence the BAc Pb. The results of present study provide insights into the correlation between soil properties and BAc Pb , and prediction of the bioaccessibility and bioavailability of Pb in different types of soil. [Display omitted] • A meta-analysis of correlation between soil properties and BAc Pb was performed. • Five soil parameters pH, SOM, Clay, CEC and T-Pb were systematically analyzed. • BAc Pb can be greatly influenced by soil pH in gastric and small intestinal phases. • pH of gastric juice is a major source of heterogeneity for soil pH and BAc Pb. [ABSTRACT FROM AUTHOR]

• Previous studies showed that the vulnerability of mycorrhiza to negative impacts of reactive nitrogen differs in different forests. • In this paper, we introduce a model that explains such differences as resulting from the optimization of belowground tree C investment in forests with inorganic or organic N economy. • The analysis of this model showed that C investment in mycorrhiza did not depend on increasing input of available forms of N into the ecosystem in the case of inorganic N economy (e.g. forests with prevalence of maple on naturally fertile soils). • In contrast, in the case of organic N economy, the model showed decreasing C investment in mycorrhiza with increasing available forms of N (e.g. spruce or pine forests on naturally acid poor soils). • As mycorrhizae are essential for nutrients and water acquisition in trees, we suggest our approach could contribute to predicting the responses of forests to global environmental changes. Elevated reactive nitrogen deposition can result in declines in belowground C allocation to mycorrhiza, potentially threatening the sustainability of forest ecosystems, especially with regard to ongoing global environmental changes. Previous studies showed that the vulnerability of mycorrhiza differs in different forests. In this paper, we introduce a model that explains such differences as resulting from the optimization of belowground tree C investment in forests with inorganic or organic N economy. According to the model, the optimization of belowground tree C investment in forests with organic N economy is governed by indirect competition between trees for available forms of N. We predict decreasing C investment in mycorrhiza with N deposition in systems dominated by an organic N economy. In contrast, in forests with inorganic N economy the optimization of belowground tree C investment is governed by direct competition between trees for available forms of N. We show that C investment in mycorrhiza does not depend on N deposition in the case of inorganic N economy. Parameterizing the model with data from spruce and beech temperate forests, we show that spruce forests are more sensitive to N deposition with a decrease of tree investment in mycorrhiza, which seems to be consistent with empirical findings. As mycorrhizae are essential for nutrients and water acquisition in trees, we suggest our approach could contribute to predicting the responses of forests to global environmental changes. [ABSTRACT FROM AUTHOR]

• A unique dataset combining soil properties and stand productivity was compiled. • Common soil chemical properties were poor predictors of stand productivity. • Forest soils with low nutrient stocks sometimes exhibit high stand productivity. • Nutrient fluxes and cycling could better explain stand productivity. Forest soil fertility can be defined as a combination of physical, chemical and biological factors characterising the biomass production capacity of the soil. However, numerous ecological variables affect tree growth and the aim of the present study was to investigate the specific influence of soil chemical properties on tree productivity at 49 acidic forest sites. A standardized tree productivity index based on tree height expressed as dominant height of the studied stand divided by maximum tree height observed at the same age for the same species in the same climatic region was firstly computed at each site. This index is assumed to limit the influence of species, ages and climate. A soil database was also compiled with data on soil properties from 47 temperate (France) and two tropical (Congo, Brazil) sites. Data included seven tree species, varying in age from 1 to 175 years. Commonly used indicators such as C:N ratio, soil pH, as well as available and total pools of soil nutrients were compared to the standardized tree productivity index, to find the most reliable indicator(s). Nutrient pools at fixed mineral soil depths (down to 100 cm) were used, as well as (for 11 stands) the depth comprising 95% of fine roots. Our results show that none of the common soil chemical parameters tested in this paper could individually explain stand productivity. Combinations of different parameters were also tested using PCA and they could better explain the variability of the data set but without being able to separate the sites according to their standardized tree productivity index. Moreover, random Forests performed on our dataset were unable to properly predict the standardized tree productivity index. Our results reinforce the idea that the influence of the soil chemical fertility on stand productivity is complex and the soil chemical parameters alone (individually or combined) are poor predictors of tree productivity as assessed by the H 0 :H max index. In this paper we focused on static soil chemical indicator and more dynamic indictors, such as nutrient fluxes involved in the biogeochemical cycles, could better explain stand productivity. A companion paper (Legout et al., 2020) focuses on the connection between productivity and different components of the biogeochemical cycle, using data from 11 of the stands presented in this paper. [ABSTRACT FROM AUTHOR]

• The Pre-Eifelian paleosol on rhyolite demonstrates surprisingly deep development. • Rhyolite contains allochthonous substituted by pyrite inclusions of nematophyte. • Pyrite oxidation drives the acid sulfate paleosol development. • Gypseous acid sulfate paleosol was developed under warm humid climate. During Late Devonian Voronezh Land was one of the main volcanic centers of Central Devonian Field. Earlier eruptions on the given territory have not been documented. This paper presents the detailed multidisciplinary study of the Pre-Eifelian paleosol developed from rhyolite lava deposited on the contact with the Proterozoic basement in Shkurlat granite quarry (Voronezh region, Russia). Discovered paleosol includes abundant coalified and partly substituted by pyrite allochthonous remnants of Nematasketum and Prototaxites. Main part of them had an outstanding preservation of tissues. Along with typical for rhyolite a quartz dominance, paleosol contains in situ developed kaolinite, gypsum, goethite, jarosite. Abundant Fe-nodules concentrated in the second half part of the shallow (∼50 cm) paleosol profile are composed of gypsum, goethite and metastable Fe-sulfates - jarosite and voltaite. Based on a complex of analytical characteristics, the discovered paleosol was attributed to acidic sulfate soil. The development of paleosol was initiated by pyrite oxidation which played the role of trigger. Being gypseous, paleosol bears the characteristics which are typical for paleosol of humid type. Based on geochemical data (CIA, CIA-K, PWI indexes) the obtained climatic parameters correspond to a subtropical climate with MAP 1200–1300 mm and MAT ∼ 17 °C. [ABSTRACT FROM AUTHOR]

In the subsurface environment, highly toxic hexavalent chromium (Cr(VI)) control and remediation are essential to avoid further ecological impacts and reduce environmental risks. This paper investigated the enhanced Cr(VI) electrokinetic removal in the soil through the approaching cathode method. Besides, a novel four-step sequential fractionation method was used to reflect the strength of Cr(VI) binding to the soil. The approaching cathode enhanced the electrokinetic delivery of surface-bound Cr(VI) by advancing the alkaline front for Cr(VI) desorption and improving the electric potential flattening of the soil layers. Desorption of Cr(VI) by the alkaline front involved converting the inner-sphere complexes form of Cr(VI) to a weakly adsorbed form susceptible to ionic strength. In addition, the acidic front provided a favorable environment for the photochemical reduction of Cr(VI) by soil species or the added citrate as the electron donors. Improving the potential distribution could regulate the energy consumption of individual soil layers and efficiently operate the electrokinetic transfer of pollutants. The work results have significant scientific and practical significance for applying the in-situ electrokinetic technique in subsurface pollution control. [Display omitted] • Cr(VI) forms bound to the soil were classified into four categories. • The approaching cathode improved potential flattening and Cr(VI) desorption. • Advancing the alkaline front could modulate system energy consumption distribution. • The acidic front supports photochemical reducing Cr(VI) within the anolyte and soil. [ABSTRACT FROM AUTHOR]

Aggregate-associated soil organic carbon (SOC) controls organic carbon stabilization. The research question of this paper was: what were the effects of conversion of forest land uses to agriculture at Ranchi, India on SOC pools, soil aggregation and aggregate-associated C? The samples were taken from six different land uses viz. native forest (NF), agri-horticulture (AH), native grass land (NG), rice-wheat (RW), rice- vegetable (RV) and maize-wheat (MW) from three soil depths (0–15, 15–30 and 30–45 cm). Soil aggregation, SOC pools and aggregate-associated C were determined. Results revealed that SOC concentration in NF was 36%, 67% and 127% higher than RW, RV and MW land uses, respectively, at 0–15 cm depth. The microbial biomass carbon (MBC) was higher in NF land uses than rice-based systems in the soil surface (0–15 cm) due to less disturbance. In surface soils (0–15 cm depth) under NF, the large macroaggregates had 21% and 40% higher SOC concentration than RW and RV, respectively. Similarly, NF soil had larger small macroaggregate-associated C than RW, RV and MW systems in the 0–15 and 15–30 cm layers. This result supports that tillage and regular crop removal under arable (MW, RW and RV) systems adversely affect loss of SOC contents in the surface layers and C storage inside aggregates, both in the 0–15 and 15–30 cm soil layers at Ranchi, India. • Conversion of native forest (NF) to rice-wheat (RW) system reduced total C by 36%. • Large macroaggregates of NF had ~21% and 40% higher total C than RW system. • RW system had higher C than rice-maize (RM) in the surface (0–15 cm) soils. • NF and grassed soils had higher soil aggregation and macroaggregates than RW. [ABSTRACT FROM AUTHOR]

• The combined effects of calcium carbonate and NPKS fertilizer addition on growth of Populus spp. were assessed based on the results from a field and a pot experiment. • The fertilization effect on poplar growth was strong only if soil conditions in terms of pH and exchangeable Ca were at a sufficiently high level. • Available nutrient concentrations in the soil and foliar nutrient concentrations in the plant suggested co-limitation of poplar growth by N and Ca. • The results of this study emphasize the importance of adapting the level of CaCO 3 to the given soil conditions. The cultivation of Populus spp. on acid soils is difficult mainly due to low nutrient availability, limiting the distribution and use of this marketable tree species. In this paper we report the results of two experiments, in which a granulated highly reactive micronized calcium carbonate (CaCO 3) was tested at increasing levels to improve the effect of NPKS fertilization on poplar growth. Twin field and pot experiments were carried out in 2017 using two different poplar clones, both of which are often used in Italy. In addition to analysing the data from the two experiments separately, common patterns were evaluated using a mixed-effect model with CaCO 3 level and fertilization as fixed effects, and the experiment type as random effect. Growth was assessed in terms of total height, diameter and biomass. Taken together, the results from the two experiments showed that fertilization led to enhanced growth of poplar, but this effect was stronger when soil conditions in terms of pH and exchangeable Ca were at a sufficiently high level. Available nutrient concentrations in the soil and foliar nutrient concentrations in the plant suggested co-limitation of poplar growth by N and Ca. In conclusion, the results of this study on one hand emphasize the importance of adapting the level of CaCO 3 to the given soil conditions, and on the other hand ask for further studies addressing the relative importance of elevated pH and improved Ca nutrition. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we provide support for the hypothesis that trees and fungi modify their physical environment in acidic forest soils by actively translocating metal cations from the mineral to the organic horizon. We suggest that pH buffering and soil organic matter (SOM) turnover in organic horizons are regulated by Ca and Mg cycling via the tree canopy and litter fall and by fungal translocation of Al from mineral soil. Fungi in addition translocate Fe from mineral to organic horizons to enhance the degradation of aromatic structures in SOM. Together these processes are in control of N bioavailability, including new inputs via N fixation. Cycling of Ca and Mg via tree canopy typically increase the base saturation and pH towards the surface of organic forest soil horizons. This process is most clearly depicted at sites with laterally moving groundwater. An up-transport of Al from mineral to the organic horizon is most important as a pH buffering process in less productive, acid soils having a pH below approximately 4.5. At this pH, the non-acidic properties of organically complexed Al keep pH at a level sufficiently high for maintained microbial activity. Furthermore, the formation of bridging bonds between major organic functional groups (carboxyls and phenols) and di- and trivalent metal cations of Ca, Al and Fe possesses a strong influence on the tertiary structure of SOM and its persistence to degradation and delivery of N. [Copyright &y& Elsevier]

Abstract: Application of lime and fertilizers might impact soil properties by affecting their physico-chemical parameters. The focus of the Versailles 42-plots experiment that was started in 1929 has always been to determine in fallow conditions the impact of mineral fertilization over time on the physico-chemical properties of a loamy soil. This paper''s aim is to assess the impact of long-term mineral fertilization on mechanical strength and soil stability. Soil samples of similar texture and bulk density were taken from the 42-plots site, with pH ranging from 3.5 to 8.2. Aggregate stability followed the procedure of Le Bissonnais (1996). Compression tests were performed in drained conditions and short loading time (300s). Remolded and saturated soil samples were used to focus on the impact of chemical changes due to repeated fertilization. The pre-compression stress values Pc were derived from compression curves using various model fits according the shape of curve. Chemical discrepancies among soils provided from pH, organic matter and diversity of treatments. The decrease of pH reduced the cationic exchange capacity (CEC) value due to the protonation of variable charges and retention of positively charged hydroxyl-Al polymers. Exchangeable aluminum represented up to 90% of the CEC in acid soils as calcium ions represented from 80 to 98% of CEC with increasing pH of neutral and alkaline soils. Compression curves showed different global shapes according pH values and the contrasted behavior of acid soils when compared to other ones. The Pc values of highly acid soils were much greater than other treatments (greater than 150kPa compared with 30kPa). Nevertheless their Pc values decreased down to 40kPa, when soils were air-dried before compression. Meanwhile the deformation rate decreased when the pH dropped. This lower deformation cannot be explained by kinetic aspects and was not sensitive to drying. So the hypothesis of a set of yield stress avoiding drainage of the water phase and limiting soil compression was proposed. Aggregate stability tests revealed the unstable nature of all plots especially with the highly acid soils. The size distributions of fragment were very similar for all three tests with a narrow distribution in elementary particle class suggesting the predominance of dispersion in fragmentation process. But we found opposite results for this soil by comparing mechanical strength and water stability of aggregates. This contrast raised the question of the crucial role of the air-drying step on aggregate stability measurements. A small increase of aggregate stability was observed in neutral and alkaline soils due to calcium bridges when compared to reference plot. Such effect was not observed in compression behavior of remolded soils. Future studies will require the use of structured soil samples; in particular for neutral and alkaline soils to gather evidence of the effects of calcium bridges on soil stability and mechanical strength. Our results showed the need to consider interfacial processes in the soil stability and compression behavior and the great interest of the 42-plots experiments at INRA Versailles to relate chemical and physical soil properties. [Copyright &y& Elsevier]

Abstract: A modified flue gas desulphurization residue (MFGDR) was prepared and its effects on sorghum growth and acidic soil amelioration were evaluated in this paper. The MFGDR was prepared by calcining a mixture of dry/semi-dry flue gas desulphurization (FGD) residue from a coal-fired power plant, sorted potash feldspar and/or limestone powder. The available nutrients from the MFGDR were determined with 4.91wt% K+, 1.15wt% Mg2+, 22.4wt% Ca2+, 7.01wt% Si4+ and 2.07wt% SO4 2−–S in 0.1molL−1 citric acid solution. Its pH value was held at 9.60 displaying slightly alkaline. The results of sorghum pot growth in both red and crimson acidic soil for 30 days indicated that adding the MFGDR at a dosage of 2gkg−1 in total soil weight would increase the growth rate of biomass by 24.3–149% (wet weight basis) and 47.3–157% (dry weight), the stem length and thickness increase by 5.75–22.1% and 4.76–30.9% in contrast with CK treatment for two test cuttings, respectively. The effect on sorghum growth was attributed to the increase of available nutrients, the enhancement of soil pH value and the reduction of aluminum toxicity in acidic soil due to the addition of the MFGDR. The experimental results also suggested that the MFGDR could be effectively used to ameliorate the acidic soil which is widely distributed throughout the southern China. [Copyright &y& Elsevier]

Abstract: In a greenhouse study we investigated the potential of wood ash amended composts to ameliorate acid tropical soils. Three composts (produced with 0%, 8% and 16% wood ash admixture, respectively), and two acid tropical soils, an Oxisol and an Ultisol from Cameroon were used for that purpose. In this paper we report the effects on the soil microbiota at the end of the cropping cycle (100 days soybean plus 100 days fallow). Principal coordinate analysis of denaturing gradient gel electrophoresis patterns of ammonium oxidizing bacteria (AOB) indicated that they were stimulated by addition of compost. AOB communities of the compost treated soils differed from the control ones, and no significant differences among the different composts were found in both soils. Soil type clearly influenced the AOB community. Ester-linked phospholipid fatty acids increased in compost treated soils, up to an ash amendment of 8%. The ratio of cyclopropyl-to-monoenoic precursor (cy19:0 to 18:1ω7), which has been proposed as an indicator of stress conditions, decreased upon compost addition and did not differ among the treated soils. Community level physiological profiling indicated an increase in activities after addition of compost, the effect was most distinct for the compost with 16% ash. Based on these results, compost with moderate dose of wood ash is considered beneficial to the soil microbiota and could thus be used for ameliorating tropical acid soils. [Copyright &y& Elsevier]

Abstract: In this paper we evaluated the effects of various amendments, notably zeolite, red mud (a by-product of aluminium manufacturing) and lime on decreasing the bioavailability and phytotoxicity of Pb, Cd and Zn present in a contaminated acidic soil (pH=4.2). Pisum sativum and Triticum vulgare were grown in a glasshouse experiment on untreated-polluted (control) and amended soils and their yield and metal uptake determined. The influence of plants on the total concentration and mobility of Pb, Cd, and Zn, and on several soil microbiological and biochemical parameters was also evaluated and compared to unplanted (control and amended) soils on which we have previously reported. All the amendments enhanced plant yields significantly. Red mud and lime decreased Zn, Pb and Cd availability to plants, whilst zeolite was efficient only at blocking Pb. Red mud in particular decreased heavy metal uptake of pea and wheat by 60–34% (Pb), 79–80% (Cd), and 93–64% (Zn) respectively when compared to the control plants. After plant growth, Cd and Zn solubility in the amended soils was significantly higher than in respective unplanted soils. Likewise, the number of fast-growing heterotrophic bacteria and fungi was higher after pea and wheat compared to bare soil, and this was irrespective of the treatment applied. These data together with Biolog-derived parameters (AWCD and richness) and enzyme activities (dehydrogenase, urease and β-glucosidase) also suggested that pea rhizodeposits, in the different soils, were either more abundant or more readily-available to soil bacterial communities compared to wheat rhizodeposits. [Copyright &y& Elsevier]

Most biodiversity studies endeavour to put forward strategies for its short-term enhancement, seeking to understand the spatial scale. However, biodiversity preservation strategies should also take into account temporal scales, in order to fulfil the main biodiversity preservation objectives. Biodiversity variability also depends on the structural heterogeneity of the land on which this strategy is developed. Agroforestry systems have a tree component that makes this heterogeneity more important than in exclusively agronomic systems. This paper aims to evaluate the effect of different soil fertility management (application of lime and fertiliser in both organic and inorganic nitrogen forms) on tree and pasture growth, as well as on the pasture richness in a silvopastoral systems developed on a 5-year-old Pinus radiata D. Don plantation over 6 years. Temporal scale, as well as spatial biodiversity scale, should be taking into account in biodiversity studies in forests. Tree development as well as fertility soil modifications modified species richness, the relative dominance between species and the type of species. The lack of management caused an undesirable development of shrubs, main resource of forest fires development in the region. Lower tree densities than those currently used combined with authocthonous breed grazing, to reduce shrub biomass is the best option to sustain biodiversity and productivity from the area. [Copyright &y& Elsevier]

• Soil pH decreased by 0.23 unit after forestation over the globe. • Climate was the most important predictor of soil pH change after forestation. • Forestation significantly decreased soil pH in humid areas but not in arid areas. Forestation is a key strategy to mitigate climate change caused by anthropogenic carbon dioxide emissions. However, the impacts of forestation on soil pH remain unclear, despite critical roles of soil pH in regulating key soil biogeochemical processes. Here, we collected a global dataset of soil pH change after forestation, which included 1082 observations from 171 published papers. Results showed that soil pH declined significantly by 0.23 after forestation over the globe. Soil pH consistently declined after forestation, no matter the forest was established naturally or by planting, on croplands or grasslands. The decline of pH after forestation was generally larger in neutral soils (pH 6–7) than in acidic soils (pH < 6) and alkaline soils (pH > 7), and larger in boreal and temperate forests than in tropical forests. Soil pH decreased significantly in humid areas but not in arid regions. Random forest analysis showed that climate was the most important regulatory factor to influence soil pH change after forestation. Mean annual temperature and precipitation probably affected soil pH both directly and indirectly via altering soil physiochemical properties. Given vital roles of soil pH in regulating carbon and nutrient dynamics, our findings have important implications for the long-term impacts of forestation on carbon and nutrient dynamics. [ABSTRACT FROM AUTHOR]

Abstract: Elevated aluminum (Al) availability limits plant growth on acidic soils. Although this element is found naturally in soils, acidic conditions create an environment where Al solubility increases and toxic forms of Al impact plant function. Plant resistance to Al is often attributed to organic acid exudation from plant roots and the chelation of cationic Al in the rhizosphere. The association of arbuscular mycorrhizal (AM) fungi with the roots of plants may alleviate Al toxicity by altering soil Al availability or plant exposure through the binding of Al to fungal structures or through the influence of fungi on exudation from roots. Diverse communities of AM fungi are found in soil ecosystems and research suggests that AM fungi exhibit functional diversity that may influence plant performance under varying edaphic environments. In the present study, we evaluated acidic isolates of six AM species in their responses to Al. Andropogon virginicus (broomsedge), a warm-season grass that commonly grows in a range of stressful environments including acidic soils, was used as a plant host for Acaulospora morrowiae, Glomus claroideum, Glomus clarum, Glomus etunicatum, Paraglomus brasilianum, and Scutellospora heterogama. Fungal spores were germinated and exposed to 0 or 100 μM Al on filter paper in sand culture or were grown and exposed to Al in sand culture in association with A. virginicus. Short- and long-term responses to Al were evaluated using direct measurements of fungal spore germination, hyphal elongation, and measurements of A. virginicus colonization and plant growth as a phytometer of AM function in symbio. Spore germination and hyphal elongation varied among AM species in response to Al, but patterns were not consistent with the influences of these AM species on A. virginicus under Al exposure. Exposure to Al did not influence colonization of roots, although large differences existed in colonization among fungal species. Plants colonized by G. clarum and S. heterogama exhibited the least reduction in growth when exposed to Al, produced the highest concentrations of Al-chelating organic acids, and had the lowest concentrations of free Al in their root zones. This pattern provides evidence that variation among AM fungi in Al resistance conferred to their plant hosts is associated with the exudation of Al-binding organic acids from roots and highlights the role that AM fungal diversity may play in plant performance in acidic soil environments. [Copyright &y& Elsevier]

Biochar was prepared from rice straw and modified with 15% H 2 O 2 and 1:1 HNO 3 /H 2 SO 4 , respectively. The unmodified biochars and HCl treated biochars for carbonate removal were used as control. The biochars were added to the acid paddy soil collected from Langxi, Anhui Province, China at the rate of 30 g/kg. The paddy soil was flooded and then air-dried, and soil pH and Eh were measured in situ with pH electrode and platinum electrode during wet-dry alternation. Soil pH buffering capacity (pHBC) was determined by acid-base titration after the wet-dry treatment. Then, the simulated acidification experiments were carried out to study the changing trends of soil pH, base cations and exchangeable acidity. The results showed that soil pHBC was effectively increased and the resistance of the paddy soil to acidification was apparently enhanced with the incorporation of H 2 O 2 - and HNO 3 /H 2 SO 4 -modified biochars. Surface functional groups on biochars were mainly responsible for enhanced soil resistance to acidification. During soil acidification, the protonation of organic anions generated by dissociation of these functional groups effectively retarded the decline of soil pH. The modification of HNO 3 /H 2 SO 4 led to greater increase in carboxyl functional groups on the biochars than H 2 O 2 modification and thus HNO 3 /H 2 SO 4 -modified biochars showed more enhancement in soil resistance to acidification than H 2 O 2 -modified biochars. After a wet-dry cycle, the pH of the paddy soil incorporated with HNO 3 /H 2 SO 4 -modified biochar increased apparently. Consequently, the addition of HNO 3 /H 2 SO 4 -modified biochar can be regarded as a new method to alleviate soil acidification. In short, the meaning of this paper is to provide a new method for the amelioration of acid paddy soils. Increase the soil pHBC, slow down the decline of soil pH, and improve the resistance to acidification. [Display omitted] • The addition of modified biochars obviously increased pHBC of an acid paddy soil. • HNO 3 /H 2 SO 4 -modified biochar increased soil resistance to acidification more evident. • Modified biochars increased the pH of the paddy soil after a wet-dry cycle. • Protonation of organic anions on biochars was main mechanism for soil pHBC increase. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with utilization of biomass of Jatropha hulls for production of bioactive compost. In the process of Jatropha oil extraction, a large amount of hull waste is generated. It has been found that the direct incorporation of hull into soil is considerably inefficient in providing value addition to soil due to its unfavorable physicochemical characteristics (high pH, EC and phenolic content). An alternative to this problem is the bioconversion of Jatropha hulls using effective lignocellulolytic fungal consortium, which can reduce the phytotoxicity of the degraded material. Inoculation with the fungal consortium resulted in better compost of jatropha hulls within 1 month, but it takes nearly 4 months for complete compost maturation as evident from the results of phytotoxicity test. Such compost can be applied to the acidic soil as a remedial organic manure to help maintaining sustainability of the agro-ecosystem. Likewise, high levels of cellulolytic enzymes observed during bioconversion indicate possible use of fungi for ethanol production from fermentation of hulls. [Copyright &y& Elsevier]

• An operational method to map soil carbon content (SOC) is applied in Tuscany. • It is based on the combination of ground, ancillary and remote sensing datasets. • The method is tested versus all measurements and through a leave-one-out approach. • The final map reproduces the SOC observations and follows main ecosystem features. The organic carbon stored in the topsoil is an essential component of the global carbon cycle which should be quantified for a variety of purposes. The current paper proposes a new approach to map the amount of organic carbon stored in the 0.3 m topsoil (SOC), based on the statistical combination of a large number of ground observations with ancillary and remote sensing data. This approach is applied and tested in Tuscany, a region of Central Italy that is characterised by extremely diversified and heterogeneous environmental features. More than 3500 soil samples were collected and made available for the purpose, together with a soil map, meteorological data, a land use map and MODIS Normalised Difference Vegetation Index (NDVI) imagery. This information was processed by advanced statistical methods to yield a final map which describes the SOC spatial distribution in the region with a spatial resolution of 250 m. The map well reproduces the SOC variability in the region, showing higher SOC values for forests with respect to grasslands and croplands and SOC peaks related to peats and acidic soils. The accuracy assessment, carried out both versus all ground observations and by a leave-one-out cross validation strategy, testifies to the high quality of the SOC map, which has a global RMSE comprised between 17.5 and 32.3 t ha−1. The map is also accompanied by per-pixel estimates of error variance which are informative on the uncertainty of SOC prediction. [ABSTRACT FROM AUTHOR]

There is a growing need to recover degraded soils to restore their essential ecosystem services and limit damages of anthropic activities onto these systems. Safe and sustainable solutions for long-term recovery must be designed, ideally by recycling existing resources. Using ash from combustion of residual forest biomass at the pulp and paper industry is an interesting and sustainable strategy to recover mining soils. However, formulations must be found to limit the potential toxicity associated with soluble salts and chloride that ash contains. Here, we assessed the effectiveness of three field ash-based amendments for the recovery of three highly acidic soils from Portuguese abandoned mines. Three amendments were tested: an un-stabilized mixture of ash and biological sludge, granulated ash, and granulated ash mixed with composted sludge. One year after application in open field plots (in the scope of LIFE No_Waste project), soil health restoration was evaluated through (i) soil physico-chemical characterization and (ii) soil habitat functions though standardized ecotoxicological tests. This study highlights that stabilized materials provided nutrients, organic matter and alkalinity that corrected soil pH and decreased metal bioavailability, while controlling the release of soluble salts and chloride from ash. This soil improvement correlated with improved soil model organisms' reproduction and survival. For similar amendment, the native soil properties studied (as soil native electrical conductivity) affected the level of organism response. This work provides evidence that ash stabilization, formulation and supplementation with organic matter could be sustainable strategies to restore highly degraded mining soils and to recover their ecological functions. It further highlights the importance of analyzing combined effects on soil physico-chemical properties and ecological function recovery to assess restoration strategy efficiencies in complex multi-stressor environments. • Ash-based formulations improved physico-chemical conditions in highly degraded mining soils. • Invertebrate reproduction benefits from stabilized ash granules and composted sludge application. • Organic carbon addition with composted sludge promotes E. crypticus reproduction. • Ash granulation reduced EC and soluble chloride-related hazard for model invertebrates. Ash-based amendments are a promising strategy to contribute to the recovery of mining soils' capacity to support ecosystems function and to recycling nutrients in relevant waste streams. [ABSTRACT FROM AUTHOR]

In this paper, the corrosion behaviors of a welded joint of X80 pipeline steel underneath disbonded coating in an acidic soil solution were studied through electrochemical measurements, SEM/EDS and 3D ultra-depth microscopy. The results showed that the corrosion rates of the heat affecting zone (HAZ) specimens were the largest during the experiment, while the smallest corrosion rates always appeared with the base metal (BM) specimens at the same position. The corrosion rate of all the specimens at the opening were always larger than those at the bottom of the disbanded coating during the whole experiment. General corrosion dominated the surface of all specimen at different position, with much nonuniform corrosion inlaying in it. The nonuniform corrosion sensitivity of the HAZ specimens was larger than that of the BM and welded zone (WZ) specimens, whether at the opening or at the bottom. Under the disbonded coating, the nonuniform corrosion sensitivity of the specimens firstly decreased with the distance from opening and increased at the bottom. The maximum corrosion fluctuation of the HAZ specimen was available at the opening. • Corrosion of X80 steel welded joint under a crevice in acidic solution were studied. • Maximum and minimum corrosion rate existed in the HAZ and BM, respectively. • Corrosion rate at the opening was larger than that at the bottom of the crevice. • Nonuniform corrosion sensitivity of HAZ was larger than that of the BM and WZ. [ABSTRACT FROM AUTHOR]

In Part I of this paper we reported, for each of 11 acid soils, the rankings of six metals according to their sorption from solutions containing all six, and according to their retention under desorption conditions. Here, we analyse the same data from a different perspective: for each metal, we rank the soils by their capacities to sorb and retain it as reflected by soil/solution distribution coefficients K d100 measured using starting solutions containing 100mgL−1 of each metal. We also ranked the soils for overall heavy metal sorption and retention capacities using Kaplan's compound measure K dΣ, and we investigated the influence of soil characteristics on K d100 and K dΣ100 values. Overall capacity for sorption of heavy metals was positively related to HOM, kaolinite and Fe oxides contents, and negatively related to CEC and to vermiculite and haematite contents. Overall capacity for retention of heavy metals was positively related to HOM and kaolinite contents, and negatively related to CEC and vermiculite content. The good correlation between K dΣ100(sorption) and the first component extracted in a principal components analysis of K d100(sorption) values, and between K dΣ100(retention) and the first component extracted in a principal components analysis of K d100(retention) values, supports the adequacy of K dΣ as a measure of the overall capacity of a soil to sorb or retain heavy metals. [Copyright &y& Elsevier]

Phosphates are very important basic materials in agricultural and other industrial applications. Phosphorus is often present in low concentrations in wastewater, almost solely in the form of organic and inorganic phosphates (ortho-and poly-phosphates). The removal of phosphates from surface waters is generally necessary to avoid problems, such as eutrophication, particularly near urban areas. The usual methods of treatment are either biological or physicochemical by sedimentation. This paper studies the removal of phosphate species by adsorption onto calcite used as natural adsorbent. The phosphate solutions were prepared artificially by adding certain quantities of K2HPO4 in water. The effect of equilibrium pH, phosphate/mineral ratio and contact time was studied. The results showed that pH plays an important role in the removal of phosphate species from solution, with removal being more efficient in the basic pH region. The experimental results also show that adsorption is also efficient for high ratios phosphate/adsorbent. Finally, the adsorption process is time dependant. Based on the experimental results a possible mechanism of phosphate removal onto calcite surface is proposed. As a general conclusion, phosphate species seem to be efficiently removed from solutions using calcite as natural adsorbent. In addition, the adsorption product can be used as fertilizer for acid soils. [Copyright &y& Elsevier]

Abstract: In situ stabilization of toxic elements in contaminated soils by the addition of amendments is being considered as an effective technique for remediation. In this paper, we performed both kinetics and equilibrium-based sorption experiments of three toxic elements (As, Cd and Tl) in soils amended with two by-products (phosphogypsum and sugar foam, rich in gypsum and calcium carbonate, respectively) to ascertain the feasibility of their application for improving the sorption capacity of As, Cd and Tl from the soil at 25, 35 and 50°C. Kinetic studies indicated that the sorption follows a pseudo-second-order (PSO) kinetics and the sorption is a two-step diffusion process where both film and intraparticle diffusion played important roles in the sorption mechanisms of the elements. The Langmuir isotherms applied for sorption studies showed that the estimated maximum sorption capacity of the elements in control and amended soils decreased in the order of Cd>As>Tl. Using the thermodynamic equilibrium parameters obtained at different temperatures, the thermodynamic constants of sorption (ΔG, ΔH and ΔS) were also evaluated, indicating spontaneous and endothermic nature of the process, except Tl which was exothermic. An optimal scaling procedure was undertaken to determine the relationships between the kinetic and equilibrium sorption parameters. By means of statistical analysis it was seen that these inter-parametric relationships are dependent on the element nature. [Copyright &y& Elsevier]

Abstract: This paper provides a quantitative comparison between electrocoagulation and chemical precipitation based on heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) removal from acidic soil leachate (ASL) at the laboratory pilot scale. Chemical precipitation was evaluated using either calcium hydroxide or sodium hydroxide, whereas electrocoagulation was evaluated via an electrolytic cell using mild steel electrodes. Chemical precipitation was as effective as electrocoagulation in removing metals from ASL having low contamination levels (30mgPbl−1 and 18mgZnl−1). For ASL enriched with different metals (each concentration of metals was initially adjusted to 100mgl−1), the residual Cr, Cu, Pb and Zn concentrations at the end of the experiments were below the acceptable level recommended for discharge in sewage urban works (more than 99.8% of metal was removed) using either electrocoagulation or chemical precipitation. Cd was more effectively removed by electrochemical treatment, whereas Ni was easily removed by chemical treatment. The cost for energy, chemicals and disposal of metallic residue of electrocoagulation process ranged from US$ 8.83 to 13.95tds−1, which was up to five times lower than that recorded using chemical precipitation. Highly effective electrocoagulation was observed as the ASL was specifically enriched with high concentration of Pb (250–2000mgPbl−1). More than 99.5% of Pb was removed regardless of the initial Pb concentration imposed in ASL and, in all cases, the residual Pb concentrations (0.0–1.44mgl−1) were below the limiting value (2.0mgl−1) for effluent discharge in sewage works. [Copyright &y& Elsevier]

Abstract: This paper reviews simplified process models for denitrification. More than fifty models were considered. The majority of these (simple) models are based on potential denitrification—either measured as a soil''s property or computed from organic C dynamics—or consider denitrification as a first-order decay process. As it is generally accepted that environmental soil conditions affect the denitrification process, reduction functions are used. Although denitrification is truly driven by the non-availability of oxygen, most authors argue that oxygen dynamics in soil is hard to simulate (or to measure). Therefore, water content is used as a complementary for oxygen diffusion. The higher the water content, the less oxygen will be present. Other factors that influence denitrification are nitrate–nitrogen content, soil temperature and soil acidity (pH). The availability of easily decomposable organic carbon determines the value of potential denitrification or the first-order decay rate constant. Although there seems to be consensus about the mathematical formulation of the simple process model, the shapes of the reduction functions differ largely between the models, especially for the water content reduction function. From a sensitivity analysis it follows that the model is most sensitive to the parameters of the water content reduction function, indicating that these parameters and the water content must be determined with great accuracy. [Copyright &y& Elsevier]

Abstract: Metal pollution in soils is a world-wide problem requiring new tools for environmental management. This study investigated the transport processes of metals (Cd, Cu and Pb) in undisturbed soil columns of an acid soil amended with phosphogypsum, sugar foam, and phosphoric rock (PG, SF and PR). Sorption mechanisms have been examined in a companion paper using sequential extraction methods. This investigation focused on how these sorption mechanisms relate to transport parameters estimated from metal breakthrough curves using temporal moment analysis. The application of the 3 soil amendments significantly reduced the total metal mass leached from all the columns. Metal travel times were also longer with the addition of the amendments, although retardation values were much lower than those reported in batch studies. Retardation (R) values for Cd, Cu and Pb averaged 1.6, 1.8 and 1.7, respectively, for all treated columns. These R values for the control columns were 1.2, 1.3 and 1.4 for Cd, Cu and Pb, respectively. Additional observations of Al, Ca and leaching from the columns revealed the existence of fast exchange and precipitation–dissolution reactions included in the transport of metals through the soil. Under the conditions of this study, it is estimated that the mass of Cd, Cu and Pb leached from the soil would be reduced by more than 60–99% with the addition of the amendments. Therefore, all 3 amendments (PG, SF, and PR) appear to have reasonable potential to be applied to reduce metal leaching in polluted agricultural soils. [Copyright &y& Elsevier]

Mechanical incorporation of surface-applied lime (CaCO3) to ameliorate subsoil acidity is often not feasible because of damage to plants and erosion hazards. This paper presents results of a field cage experiment comparing the influences of three exotic European earthworm species (Aporrectodea longa, A. caliginosa and A. trapezoides) on lime incorporation and pasture production over two seasons, on two acidic soil types under pastures on the central tablelands of New South Wales, Australia. A. trapezoides was least effective in increasing pH of soil below 2.5 cm and survived poorly compared with A. caliginosa. The latter was most effective at 2.5–10 cm whilst A. longa was more effective at 10–15 cm depth. Similar complementary increases in the level of mineralisable nitrogen (MN) by both earthworm species were also observed. There was evidence suggesting that the survival of A. longa was improved by the presence of A. caliginosa. Earthworms improved pasture growth at only one site. [Copyright &y& Elsevier]

Aluminum toxicity is a very important factor limiting crop productivity on acid soils. Early effects of aluminum toxicity comprise inhibition of cell division and effects on root elongation. The plasma membrane can be the primary target of aluminum toxicity and thus, vital staining techniques could be a powerful tool in determining effects of metal stress on the plasma membrane. In this paper, we discuss the effects of Al on growth and membrane integrity by staining root tips with a mixture of fluorescein diacetate and propidium iodide. The results show a good correlation between results from growth measurement and the vital staining. From the comparison of the luminosity patterns generated by vital staining it is easy to determine Al-resistant varieties, revealing this technique as a powerful and fast method for determining tolerance to Al in different varieties. [ABSTRACT FROM AUTHOR]

• Almuñecar cherimoya are enriched in K, P, C and N. • Cherimoya seed suffered the least changes under unfavourable climatic conditions. • Cherimoya peel, enriched in Ca and Mg, could be used as amendment in acidic soils. • Addition of pruning wastes did not significantly change the nutrient concentration. Cherimoya, a tropical fruit from South America whose commercial demand is increasing for both its exceptional flavor and high nutritional content, is expanding in cultivation to subtropical areas such as the Mediterranean coast of Andalusia (Spain). In this paper, we analyze cherimoyas (peel, pulp, and seed) grown in Almuñécar (Granada, Spain) during the years 2013, 2015, and 2016 from trees applied with different pruning wastes (avocado, cherimoya, mango, and garden). The cherimoya fruits had high contents in most of the macronutrients, especially K, Ca, and micronutrients such as Fe and Zn. The Na, P, K and Ca concentrations were related to the plant mulch that released nutrients to the soil and led to a variation in soil-nutrient bioavailability by decreasing the soil pH. The seed was the part of the cherimoya that registered the least nutritional change due to annual weather differences and the highest positive effects of mulching in terms of increased nutrient availability after mulching. [ABSTRACT FROM AUTHOR]

During the Late Glacial, hunter-gatherers began using ceramic cooking containers in three separate geographic regions of East Asia: China, Japan and in the Russian Far East. While recent research has clarified the use of early pottery in Japan, very little is known about what led to the emergence of pottery in the other two areas, including the likely environmental, economic or cultural drivers. In this paper we focus on a series of key sites along the Amur River in the Russian Far East, where early pottery has been recovered from securely-dated contexts that span ca. 16,200 to 10,200 years ago (cal BP). Interpreting how these ceramic vessels were used has been difficult because the region's acidic soils make palaeo-economic reconstructions challenging. To address this gap in knowledge we undertook lipid residue analysis of 28 pot sherds from the sites of Khummi, Gasya, and Goncharka 1 on the Lower Amur River, and the Gromatukha site on the Middle Amur. Our results indicate that pottery was employed to process aquatic oils at sites on the Lower Amur, a pattern of use that aligns closely with studies conducted in Japan, and suggests that fishing – probably of salmonids and freshwater fish – was becoming increasingly important during this period. In contrast, the results from the Middle Amur show a significant contribution of lipids from ruminant animals, indicating that these vessels were being used in different ways. Interestingly, these regional differences in pottery use also map onto contrasting manufacturing techniques, with vessels from the Middle and from the Lower Amur forming distinct pottery-making traditions. These combined insights appear to indicate a greater degree of variability in the development and use of early pottery in East Asia than has hitherto been indicated. • First organic residue analysis of the earliest pottery in the Russian Far East. • Early pottery in Osipovka culture in the Lower Amur was used for intensified processing of aquatic resources. • In contrast, results from the Middle Amur indicates the high contribution of ruminant fats. • There might be variability in the emergence of early pottery with different traditions emerging in different locations. [ABSTRACT FROM AUTHOR]