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Amorphous mineral-associated organic carbon (AMAOC) and organo-Al/Fe complexes (C p) play crucial roles in soil carbon (C) sequestration in volcanic soils. This study investigated the effects of land use management and liming on the C sequestration capacity of a young allophanic Andisol and old halloysitic-kaolinitic volcanic Ultisol sampled at 0–10 and 10–20 cm depth. This study was designed to test two hypotheses: (1) management and liming affect the C sequestration capacity of Andisol by reducing C p and increasing AMAOC to offset C p losses, and (2) they do not significantly affect the carbon sequestration capacity of Ultisol because of its more crystalline mineral forms and reduced amount of C p. This study was conducted using a selective dissolution technique and density fractionation with agricultural soils and forests as control soils. After 43 years of intensive management and liming, the soil organic carbon (SOC) content decreased by 32% in the topsoil compared to the original native forest soil (178 ± 2 g kg−1 soil), mainly in the particulate organic matter (POM) fraction, which decreased by 74% compared to the native forest soil (61 ± 9 g kg−1 soil). However, C p decreased only by 40% compared to the forest soil (62 ± 1 g kg−1 soil) from pH KCl 4.8–5.0, and AMAOC increased in 17% in the topsoil and 64% in the subsoil, supporting the first hypothesis of this study. In the cultivated Ultisol, SOC decreased by 35% due to the POM fraction, and mineral-associated organic C (MAOC) decreased by 37% compared to the forest soil (38 ± 7 g kg−1 soil). These results partially support the second hypothesis because the crystalline clay minerals from which MAOC originated remained unchanged and were strongly correlated with SOC. The mass balance of both soils indicated that the stable C losses from native forest soils were < 14%. These results highlight the importance of different C sequestration mechanisms to compensate for SOC losses in the young allophanic Andisol and old volcanic Ultisol. Our findings imply that both mechanisms can be used to estimate the C sequestration capcity in similar soil types. [Display omitted] • As pH increases, amorphous clay C (AMAOC) offsets the loss of organic-Al/Fe (C p). • 43 years of Andisol management and liming decreased C p and increased AMAOC. • POM experienced the highest losses due to deforestation among all C pools. • The C persistence and distribution of AMAOC and C p depends on soil pH Andisol. [ABSTRACT FROM AUTHOR]

Given that the lithology of the soil parent material determines the background metal concentrations in the soil (Novoselov et al., [7]), background concentrations established in one area are not applicable in areas that differ lithologically. Keywords: Soil contamination; Metals; Heavy metals EN Soil contamination Metals Heavy metals 555 557 3 02/28/23 20230301 NES 230301 Background concentrations of trace elements in soil, that is, the natural abundances of metals and metalloids in soil, have been the subject of much scientific discussion. [Extracted from the article]

Several studies have reported the presence of smithsonite (ZnCO3) in soils polluted by zinc mining. The present study aimed to determine upper critical threshold values of Zn phytotoxicity in a substrate spiked with ZnCO3 and to compare them with those obtained in field‐collected soils. We studied Zn toxicity to perennial ryegrass (Lolium perenne L.) grown in pots with unpolluted peat treated with increasing concentrations of ZnCO3 that produced nominal total Zn concentrations of 0, 0.7, 1.3, 2.0, 2.6, and 3.3%. To keep constant near‐neutral pH value in all the treatments, we used decreasing concentrations of dolomitic lime. In the treatment with total soil Zn of 3.3% (pH 6.8), the foliar Zn concentration of L. perenne was 1914 ± 211 mg kg–1, falling into the range of 2400 ± 300 mg kg–1 reported for Lolium species grown under similar laboratory conditions in a polluted soil (total soil Zn 5.4%, pH 7.3) collected near a Zn smelter. The value of 92 ± 98 mg kg–1 was obtained for the median effective concentration (EC50) values of 0.01 M KNO3‐extractable Zn using the responses of shoot dry biomass, shoot length, and total pigments. This value falls within the range of 95 ± 46 mg kg–1 reported in other studies for the EC50 values of salt‐extractable Zn using field‐collected soils. The application of ZnCO3 for spiking was able to mimic foliar Zn concentrations of Lolium species observed in field‐collected soils. The effective concentrations of soil Zn obtained in the present study are comparable to those obtained in field‐collected soils. Future research should determine effective concentrations of metals using soils spiked with metal‐containing compounds that mimic a real source of contamination. Environ Toxicol Chem 2020;39:1790–1796. © 2020 SETAC [ABSTRACT FROM AUTHOR]

The goal of phytoextraction is to remove contaminants - for example, metal(loid)s - from polluted soils through root uptake and accumulation in the harvested plant parts. Meanwhile, chelate-enhanced phytoextraction, where chelating agents such as ethylenediaminetetraacetic acid are added to the soil to increase plant-metal uptake, can reduce cleanup time in some cases. Metal phytotoxicity and uptake might depend on both bioavailable and total soil metal pools that are capable of supplying metal to the soil solution at the same time as plant roots take up ions (e.g., Lillo et al. 2020). [Extracted from the article]

The effects of income on environmentally significant behavior (i.e., behavior that does have an effect on the environment, such as traveling and waste disposal) have been strong but equivocal. The relation between knowledge and environmentally significant behavior has attracted even greater interest, but relations have been weak and explanations diverse. These findings have been based on samples in industrialized countries with relatively narrow income distributions, and this may have attenuated a clear understanding of the relations between income, environmental knowledge, and environmentally significant behavior. Using a Chilean sample (N = 1785) with a relatively wide income distribution, we found a parsimonious explanation for the ambiguous results of previous studies. Income had a much stronger and differential effect on environmentally significant behaviors, suggesting that when income affects the situation that influences behavior, it trumps knowledge or attitudes. [ABSTRACT FROM PUBLISHER]

We studied the fate of Cu in contaminated semiarid soils from two areas with different mining activities in central Chile. Several regression models were evaluated to use soil physicochemical characteristics to predict solubility, partitioning, and activity of Cu. Furthermore, we hypothesize that the type of Cu mining compound (smelter dust versus tailing sand) can be another important variable determining the bioavailability of Cu. In the studied neutral to alkaline soils, soil organic matter (SOM) enhanced Cu solubility most probably through the formation of organic complexes with dissolved organic C (DOC). As a consequence, Cu solubility and partitioning were better explained by DOC concentration than by SOM content. On the other hand, Cu activity was mainly related to soil pH and was not affected by DOC. Although we found differences between the two study areas, Cu solubility and partitioning might not be as dependent upon the origin of the Cu mining compound as upon other physiochemical characteristics that influence the concentration and characteristics of DOC. Total Cu, pH, and DOC would be the most important variables to consider on Cu solubility, however, data about the nature of SOM may certainly improve the prediction models. Thus, multiple binding site models between Cu and DOC should be studied to improve predictions of Cu solubility. [ABSTRACT FROM AUTHOR]

Highlights: [•] Shoot biomass of Oenothera picensis positively correlated to soil organic matter. [•] Shoot Cu in O. picensis positively correlated to soil exchangeable Cu. [•] Cu phytoextraction positively correlated to both exchangeable Cu and organic matter. [ABSTRACT FROM AUTHOR]

Abstract: The revegetation of soils affected by the historic pollution of an industrial complex in central Chile was studied. Spontaneous and assisted revegetation and changes in the physicochemical properties of the soils were evaluated in field plots that were amended with lime or lime+compost. Lime had no effect on plant productivity in comparison with the control, whereas the incorporation of lime+compost into the soil increased the plant cover and aboveground biomass. The application of lime+compost increased the plant productivity of Chrysanthemum coronarium (a species sensitive to the atmospheric emissions from the industrial complex), thus showing effective in situ stabilization of soil contaminants. Regression analyses suggested that the plant response was due to the increase in the soil organic matter content rather than to the increase in the soil pH. The aboveground biomass and plant cover did not differ under the spontaneous and assisted revegetation regimes. The native soil seed bank was sufficient for attainment of the proper plant cover and biomass production after the application of the soil amendments. Although the pCu2+ in the amended soils was 4 orders of magnitude higher than in the unamended control, the shoot Cu concentration was similar among most of the combinations of plant species and amendments. [Copyright &y& Elsevier]

Several methods for determination of extractable iron (Fe; or so-called “active Fe”) have been proposed. In this study, three methods of Fe extraction were tested: 1.5% phenanthroline (pH 3) and 1 M hydrochloric acid (HCl) from fresh leaves, and 1 M HCl from oven-dry leaves. A six-year-old avocado orchard (cultivar 'Hass'), grown on a calcareous soil in the proximity of Cabildo (Valparaiso region, Chile), was selected for the study. Samples of mature (5-7 moths-old) leaves of different degree of chlorosis were collected. Total Fe concentrations in chlorotic leaves were similar or even greater than in green leaves. Regressions between the extractable Fe concentrations and the leaf SPAD-color were statistically significant for phenanthroline method, while non-significant for HCl methods. Thus, phenanthroline method was superior over others for diagnosis of Fe deficiency in avocado. Phenanthroline-extractable Fe concentration of 6 mg kg-1 was considered as a critical value for mature avocado leaves. [ABSTRACT FROM AUTHOR]

Abstract: We studied soils exposed to emissions from the Ventanas copper smelter in central Chile. Values of pH, free Cu2+ activity, and total dissolved copper were determined in the saturated paste extracts and the soil solutions collected by means of perforated plastic bottles installed in situ. Soil solutions were collected based on the periodicity of the rain. The topsoils (up to 30 cm) exhibited pH values in the saturated paste extracts of 4.6–5.5 and total soil copper concentrations of 310–640 mg/kg. In contrast, subsoils exhibited pH values in the saturated paste extracts of 6.4–7.2 and total soil copper concentrations of 30–60 mg/kg. These data suggest that the anthropogenic inputs of the Ventanas smelter, with respect to increase in Cu concentrations and acidification, are restricted to the topsoil while the subsoil remains unaffected. The above observations are probably due to sandy loam texture of the topsoils that allowed rapid water infiltration that did not allow the equilibrium between the rain water and the soil constituents to be reached. Consistent with this argument, soil solutions were not as acid as saturated paste extracts. Likewise, free Cu2+ activities and total dissolved copper concentrations in the soil solutions were lower in the saturated paste extracts. Thus, saturated paste extracts were not a good proxy of soil solutions for short-duration and intense rain events. In situ soil solution sampling by simple and low-cost devices, such as perforated plastic bottles used in this study, is a better mean for assessment of metal mobility in contaminated soils than saturated paste extracts. In solutions percolating through the soil during rain events, dissolved organic carbon was the major factor controlling total dissolved copper concentrations while soil pH was the major factor controlling the free Cu2+ activity. [Copyright &y& Elsevier]

Smelting of copper (Cu) results in the atmospheric deposition of Cu onto surrounding soils. Excess concentrations of Cu in soils can be absorbed by soil biota to toxic levels or leached into the groundwater, threatening the entire ecosystem. A means to restrict Cu mobility and uptake by plants is to remove it from the aqueous phase by applying an adsorptive material. A synthetic clay (highly charged swelling mica) was tested for its ability to decrease the levels of free and 0.1 M KNO3-extractable Cu in 15 surface soils from three different Cu mining areas in central Chile. The soils contained excessive total Cu levels (112-2790 mg Cu (kg soil)-1), while extractable Cu ranged from 0.3 to 22.9 mg Cu L-1. The mica was applied to each soil at rates of 0.1%, 1%, and 2% (w/w). A 2% sodium-montmorillonite treatment and the nonamended soil served as controls. The order of treatment efficacy in reducing extractable Cu and free Cu2+ for low pH soils ( 1% mica > 2% montmorillonite > 0.1% mica. At 120 days, the 2% mica treatment maintained reductions of up to 93% in the free Cu2+ activity and up to 75% in the extractable Cu concentration upon acidification to the original soil pH value. In addition, Cu retention in mica-treated soils was more resistant to acidification than in lime-treated soils. This mica has promise for the remediation of acidic soils with metal contamination at the surface. [ABSTRACT FROM AUTHOR]

Abstract: Selective dissolution methods have been largely used to get insight on trace element association with solid phases. Modern instrumental techniques offer many tools to test the validity of selective dissolution methods and should be systematically used to this end. The association of trace elements with Fe- and Mn-oxides in soil nodules has been studied here by electron probe microanalysis. The results were compared with findings from an earlier study on selective dissolution of the same nodules by hydroxylamine hydrochloride, acidified hydrogen peroxide, and Na-citrate-bicarbonate-dithionite. Electron probe microanalysis results were consistent with previous findings using selective dissolution and showed that P, As and Cr were mainly present in Fe-oxides, while Co was mainly associated with Mn-oxide phases. These results support the applicability of the studied selective dissolution methods for fractionation of trace elements in soils and sediments containing appreciable amounts of Fe and Mn-oxide phases. [Copyright &y& Elsevier]

Iron chlorosis is a very common disorder of crops grown in calcareous soils. It is well known that the total iron concentration in leaves is not a valid index for iron nutritional status of crops and that the total iron concentration in chlorotic leaves are often similar or even greater than in the green leaves. In this study, we compare three extraction methods for iron deficiency diagnosis in young (two month old) avocado leaves: 1.5% phenanthroline (pH 3) extraction from fresh leaves, 1 N hydrochloric acid (HCl) extraction from fresh leaves, and 1N HCl extraction from oven-dry leaves. Relationships between the total and extractable iron concentrations in the leaves with the leaf color were examined by linear regression analysis. These regressions were statistically significant for the total iron and in the case of all three methods tested. However, the correlation coefficients suggest that phenanthroline extraction from fresh leaves was superior over other methods for diagnosis of iron deficiency in avocado. [ABSTRACT FROM AUTHOR]

Analyzing Soil Metal Toxicity: Spiked or Field-Contaminated Soils? Most ecotoxicological studies on soil metal toxicity are performed using spiked soils (i.e., uncontaminated or artificial soils to which increasing amounts of metals in the form of soluble salts are added in a laboratory setting). For instance, total soil metal concentrations yielding 10% inhibition in freshly spiked soils were up to 100-fold smaller (median 3.4-fold) than those in corresponding aged soils or field-contaminated soils (Smolders et al. [8]). [Extracted from the article]

Yosemite granite from the Tuolumne River series was dissolved under oxic and anoxic conditions in the presence (0.001 or 0.01 M) and absence of organic ligands in batch experiments at pH 6. Release of all elements was enhanced consider- ably in the presence of organic ligands. Citrate (tridentate) and gallate (tetradentate) increased element release to the greatest extent among the aliphatic and aromatic ligands, respectively. The extent of element mobilization observed for the aliphatic ligands decreased in the order citrate > oxalate ≈ malonate and for the aromatic ligands gallate > salicylate ≈ phthalate. The effects of the ligands generally followed trends in cation-ligand stability constants, but aromatic ligands were less effective in element mobilization than aliphatic ligands. This was attributed to protonation of the functional groups of aromatic ligands at pH 6. Rock dissolution was non-stoichiometric regardless of the presence or absence of organic ligands. Release of P and Cu (% of total element content in the unweathered rock) in the presence of organic ligands was considerably greater than that of other elements. Findings of the present study were compared to the findings of our previous study on dissolution of basalt. Differences in the mobility patterns of Y, Fe, Cu, Ti, and Zr during dissolution of granite and basalt were observed. In basalt, release of Y was enhanced considerably in the presence of citrate. In contrast, in the present study, release of Y from granite with and without citrate was at the detection limit. This difference was attributed to the difference in Y-hosting parent minerals: apatite (basalt) and sphene (granite). With and without organic ligands, no significant differences were observed in the extent of Fe released from granite under oxic versus anoxic conditions, while the extent of Fe release from basalt was considerably greater under anoxic versus oxic conditions with and without organic ligands. These differences can be attributed to the difference in major Fe-hosting phases in the rocks: biotite (granite) versus glass and augite (basalt). In the granite, concentrations of Cu released increased considerably in the presence of organic ligands under both oxic and anoxic conditions. In contrast, concentrations of Cu released from basalt were increased considerably only under oxic conditions, especially in the presence of organic ligands. This difference was attributed to the different extent of Fe release from basalt and granite that affected dissolution of Cu/Fe-sulfides. Although both Ti and Zr can be mobilized in the presence of organic ligands, in the rock where zircons hosted Zr (granite), this element was the most immobile, while in the rock where Fe/Ti oxides hosted Zr (basalt), Ti was the most immobile. [ABSTRACT FROM AUTHOR]

Considerable mobilization of Fe without mobilization of Al in Precambrian paleosols has been documented and attributed to either anoxic- or ligand-promoted dissolution. To elucidate these mechanisms, basalt was dissolved under oxic and anoxic conditions with and without citrate, and the mobility of several elements was analyzed. The extent of release of Fe and P was minor (in citratefree conditions) or considerable (with citrate) regardless of oxygen pressure. Release of Al was minor in all cases, whereas release of Cu was minor (in anoxic conditions) or considerable (in oxic conditions). Release of Cu was enhanced by citrate. In comparison, in the weathered surface of two of the oldest-known basalt-derived paleosols—the Mount Roe (2.76 Ga) and the Hekpoort (2.25 Ga)— Fe and P were considerably depleted and Al retained, consistent with the presence of organic ligands. Cu, retained in the Mount Roe paleosol but considerably mobilized in the Hekpoort paleosol, documents formation under an anoxic atmosphere and an oxic atmosphere, respectively, as inferred by others on the basis of Fe mobility. The immobility of Al in both paleosols is consistent with formation under conditions in which the annual volume of rainwater was lower than the topsoil pore volume. Mobilization of P in such paleosols developed under low-rainfall conditions provides a new proxy for identification of ligands secreted by terrestrial organisms on early Earth. [ABSTRACT FROM AUTHOR]

Very little was known about how palygorskite affects soil properties when it constitutes a significant component of the soil clay fraction. This constituted a serious impediment for the proper management of palygorskite-containing soils under irrigated agriculture. The present review is intended to summarize studies on the effects of palygorskite on chemical and physico-chemical properties of soils carried out in recent years, and to discuss future research required in this area. When palygorskite-containing soils are involved in irrigation practices, release of Mg from palygorskite into the soil solution will occur. Magnesium as an exchangeable cation, in turn, is known to decrease aggregate stability and to enhance the dispersivity of the soil clay fractions. On the other hand, magnesium as a dissolved cation is known to improve phosphorus availability in arid soils. Knowledge of factors affecting rheological properties of soil clay suspensions is essential for understanding of mechanisms of water and solid particle transfer through the soil profile. The rheological behavior of soil clay suspensions is, however, complex and cannot be predicted from that of suspensions of standard clays. Although the flocculation value of palygorskite at near neutral pH is significantly lower than that of smectite, the presence of palygorskite in the soil clay fraction will not affect the flocculation value of the soil clay since smectite, which is always present in the clay fraction of palygorskite-containing soils, has a dispersive effect on palygorskite. Palygorskite has the strongest disaggregation potential and the highest ability to migrate in the soil among common phyllosilicates such as smectite and kaolinite. Palygorskite particles are thus likely to move preferentially over smectite and kaolinite downward in the soil profile, and eventually to clog soil pores. Disaggregation and migration of palygorskite from the surface-soil during rainfall and/or irrigation may have an effect on the degree of erosion as well. Palycretes (duripans in which the cementing material is dominantly composed of palygorskite) can be formed in some landscapes. Where palycretes occur close to the surface, plant growth is severely impeded. Palycretes also reduce water permeability of the soils, creating water-logged conditions that necessitate drainage installation.Although some progress has been made recently in understanding the effects of palygorskite on chemical and physico-chemical properties of soils, much research remains to be done. Performing some additional studies on disaggregation potential and migration ability of palygorskite under conditions close to those in the field is strongly desirable. Scanning electron microscopy observations on possible changes in aggregation of palygorskite in soils following intensive irrigation might be useful. Studies of the rheological behavior of soil clays with different mineralogical composition, and palygorskite-containing soil clays in particular, are strongly encouraged. There is a need as well to study interactions of various contaminants (both organic and inorganic) with palygorskite-containing soil clays. [Copyright &y& Elsevier]

The association of rare earth and other trace elements with Fe and Mn oxides was studied in Fe-Mn-nodules from a lateritic soil from Serra do Navio (Northern Brazil). Two improved methods of selective dissolution by hydroxylamine hydrochloride and acidified hydrogen peroxide along with a classical Na–citrate–bicarbonate–dithionite method were used. The two former reagents were used to dissolve Mn oxides without significant dissolution of Fe oxides, and the latter reagent was used to dissolve both Mn and Fe oxides. Soil nodules and matrix were separated by hand. Inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry after fusion with lithium metaborate, and X-ray diffraction were used to determine the elemental and mineralogical composition of the nodules and soil matrix. The latter was composed of kaolinite, gibbsite, goethite, hematite, and quartz. In the nodules, lithiophorite LiAl2(MnIV2MnIII)O6(OH)6 was detected in addition to the above-mentioned minerals. The presence of hollandite (BaMn8O16) and/or coronadite (PbMn8O16) in the nodules is also possible. In comparison to the matrix, the nodules were enriched in Mn, Fe, K, and P, and relatively poor in Si, Al, and Ti. The nodules were also enriched in all trace elements determined. Phosphorus, As and Cr were associated mainly with Fe oxides; Cu, Ni, and V were associated with both Fe and Mn oxides; and Ba, Co, and Pb were associated mainly with Mn oxides. Distribution of rare earth elements indicated a strong positive Ce-anomaly in the nodules, compared to the absence of any anomaly in the matrix. Some of Ce was associated with Mn oxides. The improved methods achieved almost complete release of Mn from the sample without decreasing the selectivity of dissolution, i.e., without dissolving significant amounts of Fe oxides and other minerals, and provided reliable information on associations of trace elements with Mn oxides. These methods are thus proposed to be included in sequential extraction schemes for fractionation of trace elements in soils and sediments. [Copyright &y& Elsevier]

Palygorskite from the ancient mine of Sacalum, Yucatan, Mexico was mineralogically characterized and its applicability as drilling muds was evaluated. The clay consists of palygorskite with minor illite and iron oxides. The rheological properties of the clay suspensions are suitable for preparing drilling muds. [Copyright &y& Elsevier]

Dry and in situ (fluid-cell) Atomic Force Microscopy (AFM) and Low-Pressure Gas Adsorption experiments were used to investigate the surfaces of pure Na-smectite panicles. These two techniques permit the identification of different surfaces of the platelets (lateral, basal, and interlayer surfaces) and to quantify their surface area. Calculation of the surface area was done for AFM, by measuring directly the dimensions of the clay particles on AFM images, and for gas adsorption experiments, by applying the Derivative Isotherm Summation (DIS) procedure designed by Villiéras et al. (Villiéras et al. 1992, 1997a, 1997b). In the present study, we find a discrepancy between measurements of the basal and interlayer surface area. This difference is due to the stacking of platelets in dry conditions compared to their dispersion in aqueous suspension. A particle is estimated to be formed of nearly 20 stacked layers in the dehydrated state used in the gas adsorption experiment, whereas it is estimated to be composed of only 1 or 2 layers in aqueous suspension, on the basis of AFM measurements. However, the two techniques give similar results for the lateral surface area of the platelets (i.e., about 8 m²/g) and the perimeter to area ratio value of the particles because the stacking of platelets does not alter these values. This correlation confirms the effectiveness of the interpretation of the gas adsorption experiments lowest pressure domains as the adsorption on lateral surfaces. The lateral surface area has important implications in the calculation of specific sorption site density on clay material. The relevance of the lateral surface area value (8 m²/g) was tested subsequently with sorption data found in the literature. Based on those results, we show that one essential parameter for the calculation of particle edge-site density is the mean perimeter to area ratio value. This parameter can be obtained by microscopic techniques but the... [ABSTRACT FROM AUTHOR]

Textural properties of homoionic Na- and Ca-bentonite (MX-80 from Wyoming) were studied by nitrogen adsorption. Bulk samples, which contained 20% of nonclay minerals and purified samples, were taken for the study. Powder samples and compressed pellets, which were prepared by applying a uniaxial stress of 57 MPa, were examined. Presence of nonclay minerals in the bulk samples affects significantly textural properties of the system. In particular, nonclay minerals prevented full compression of the bulk samples. In comparison to Na-saturated purified samples, higher values of surface area and total pore volume were detected in Ca-saturated samples. In addition, amount of the trapped pores was considerably higher in Ca-saturated samples than that in Na-saturated ones. In Ca-saturated samples, values of micropore surface area and micropore volume were very low, or even equal to zero. In Na-saturated samples, on the other hand, considerable percentage of surface area was associated with micropores. Surface area and pore volume of the sample decreased following heating at 200 °C during 24 h, with no difference to the exchanged cation. Following compression, surface areas of Na-saturated samples decreased and those of Ca-saturated samples increased. With no differences to the exchanged cation, considerable reduction in pore volumes was observed for the purified samples following compression. In the case of the compressed nonheated samples, hydration at relative humidity of 100% during 2 days resulted in significant increase of total and micropore surface areas. The increase in surface area was contributed mainly by micropores, i.e., open surface areas of the samples increased only slightly. Behavior of heated Na-saturated sample was similar to that of nonheated one. Hydration capacity of Ca-saturated sample, however, diminished considerably after heating. [Copyright &y& Elsevier]

Investigates the rheology of aqueous suspensions of six palygorskites with different particle morphologies as a function of clay concentration, adsorbed ion, pH and electrolyte concentration using a rotary viscometer. Effects of fiber morphology; Effect of clay concentration.

Chile as a major international Cu producer faces serious soil contamination issues in mining areas. Currently Chile does not have any specific law governing the maximum permissible concentrations of metals in soils to protect ecosystems and human health. Chile heavily relies on the use of environmental laws of 14 foreign countries; the choice of the country depends on the similarity of its environmental conditions with those in Chile. In this study, we used an online database to compare the similarity of Chilean rocks to those in foreign countries. Likewise, we performed soil sampling and determined the background concentrations of Cu, As, Pb, and Zn in soils of the Aconcagua basin, the largest river basin in the Valparaiso Region of central Chile. The results showed that geochemical patterns in Chile have the greatest resemblance to New Zealand, Mexico, and Italy. The background Cu concentration in the Aconcagua basin (134 mg kg−1) exceeded the legislated limits of New Zealand (100 mg kg−1) and Italy (120 mg kg−1), whereas the background Zn concentration (200 mg kg−1) exceeded the legislated limit of Italy (150 mg kg−1). Due to the elevated natural abundance of Cu and Zn in Chile, international laws should not be applied in Chile for the assessment of soil contamination. In addition, we assessed ecological risk using the results of our previous studies obtained by analyzing native field-contaminated soils of the Valparaiso region. In the Aconcagua basin, Cu posed high risk for plants in 11% of the samples, whereas As posed high risk for earthworms in 48% of the samples. We suggest that future studies are required to search for other organisms that can serve as biomarkers of metal toxicity because our previous studies were limited to plants and earthworms. Importantly, As posed high risk to human health in 25% of the samples in our study. There is a need for future studies to demonstrate empirically an association between soil As and children's blood As in order to establish the national threshold values of soil As to protect human health. We conclude that there is an urgent need in Chile to advance from the current approach of adapting foreign laws to developing Chilean sovereign environmental legislation. • Geochemically, Chile resembles New Zealand, Mexico, and Italy. • International laws are not suitable in Chile for soil contamination assessment. • Cu and Zn are naturally abundant in the soils of Chile. • Cu and As pose high ecological risk in 11% and 48% of the studied soil samples. • As poses high human health risk in 25% of the studied soil samples. [ABSTRACT FROM AUTHOR]

The present study investigates the functionalecological status of typical light clay soils in vineyards in the southern region of Crimea, using both traditional (including fallow soils) and organic land-use systems. This analysis was carried out by examining agrochemical indicators, microbial respiratory activity, microbial biomass, and the ecological status of the microbial community. In organic vineyard soils, the mean substrate-induced respiration, microbial biomass carbon and the ratio of microbial biomass to organic carbon were found to be 2.8, 4.0, and 4.1 times higher, respectively, compared to conventional farm soils. On the contrary, the microbial metabolic coefficient was 1.4 times lower, signifying more favorable conditions for the functioning of the soil microbiota. The increased mobile sulfur content in organic vineyard soils (18.3 mg kg−1 vs. 8.0 mg kg−1 in traditional farms) and inadequate mobile phosphorus supply in some farms present potential risks. The suboptimal functional state of the microbiome in fallow soils previously under traditional plant protection necessitates comprehensive ecotoxicological analyses before development. Assessing the soil functional ecological status through an ecophysiological evaluation of the microbiome is vital for understanding ampelocenosis soils and making informed decisions on vineyard management practices. [ABSTRACT FROM AUTHOR]

Concentrations of organic acids in prebiotic soils were presumably low, given limitations in abiotic synthesis and the limited lifetimes of organic molecules before the ultraviolet shield developed on early Earth. Prokaryotes, the first land-colonizing organisms, commonly secrete aliphatic carboxylic acids, and, less extensively, secrete aromatic compounds as siderophores and antibiotics. In contrast, secretion of aromatic acids is considerable for fungi, lichens, and vascular plants. Aromatic acids are also produced by degradation of high-molecular-weight compounds from lignin and tannin, both abundant in vascular plants. The proportion of aromatic carboxylic acids in soil solutions therefore probably increased with the evolution of higher order organisms. As biomass of organisms increased over geological time, concentrations of organic acids in soil solutions and, in turn, the extent of ligand-promoted dissolution of minerals probably increased. To elucidate the contribution of ligands during weathering on early Earth, Columbia River basalt was dissolved under oxic and anoxic conditions in the presence (0.00 1 or 0.01 M) and absence of several organic ligands in batch experiments at pH 6. Release of all elements including Si was enhanced considerably in the presence of organic ligands. Citrate (tridentate) and gallate (tetradentate) increased element release to the greatest extent among the aliphatic and aromatic ligands, respectively. The extent of element mobilization observed for the aliphatic ligands decreased in the order: citrate > oxalate &ap; malonate, and for the aromatic ligands: gallate > salicylate pathalate. The effects of the ligands generally followed trends in cation-ligand stability constants, but aromatic ligands were less effective in element mobilization than aliphatic ligands. One exception was gallate, an aromatic ligand, which significantly enhanced Cu release. Ligand-promoted mobilization of Cu may therefore have increased over geological time with the increase in the proportion of aromatic ligands. In the presence of organic ligands, Fe was mobilized from basalt considerably more than Al even under oxic conditions. Complexation of Fe with organic ligands may have mobilized Fe in Precambrian paleosols where little Al mobility is observed. Extent of P and Y release was minor in ligand-free experiments and considerable with ligands regardless of PO2. Release of Cu was considerable under oxic conditions, especially with ligands, and minor under anoxic conditions. Mobility patterns of P and Y could thus possibly serve as “organomarkers” (indicative of prevalence of organic ligands in soil solutions) and mobility patterns of Cu could possibly serve as “oxymarkers” (indicative of the presence of molecular oxygen), respectively, in ancient soils. [ABSTRACT FROM AUTHOR]

Ecotoxicological studies on soil metal toxicity often rely on artificially contaminated soils. A major difficulty in using soils contaminated by anthropogenic activities (e.g., mining and agriculture) is the presence of multiple metals, which can make it impossible to distinguish the toxic effects of a particular metal. Therefore, sites with monometallic pollution have great potential for ecotoxicological research. One such site is an agricultural field in Kargaly, Orenburg region, Russia, where copper mining and smelting activities were carried out during the 18th–20th centuries. Samples of Mollisols (chernozems) were collected in the studied field. At several sampling points there were copper ore rocks on the surface, containing malachite (CuCO3 · Cu(OH)2). The soil samples had a high copper content, up to approximately 10 g kg−1, compared with 75 mg kg−1 in the background soil. Importantly, the content of other elements in all soil samples was similar to that in the background soil, highlighting the uniqueness of the monometallic contamination in the study area. Despite the extremely high total copper content, exchangeable copper was relatively low, with a maximum of approximately 0.5 mg kg−1. We performed a short‐term (21‐day) ecotoxicity assessment using perennial ryegrass as an indicator of copper toxicity. Contrary to expectations, plant growth was not affected by the high copper content in the studied soils. The low copper phytotoxicity may be explained by the low solubility of malachite. However, future long‐term experiments may be warranted to determine copper toxicity thresholds for plants under field conditions. The site discovered in the present study could potentially acquire the same significance as the Danish Hygum site for the study of monometallic soil contamination. Environ Toxicol Chem 2023;42:707–713. © 2023 SETAC [ABSTRACT FROM AUTHOR]

Phytoextraction has been proposed in many papers as a low‐cost method for remediating contaminated soil. However, if national regulation is based on total metal(loid) concentrations in soil, phytoextraction is generally infeasible because of the long time required for remediation. Assessing phytoextraction requires determination of the dynamic rate of metal removal from soil. Phytoextraction may be feasible if the main goal is to reduce the soluble fraction of the metal(loid) with the goal of reducing bioavailability. However, it has been reported that there is a large mass balance mismatch between the reduction of the soluble metal fraction in contaminated soil and metal uptake by plants. Several studies report that the decrease of soluble fraction of metals in soil is higher than can be accounted for by plant uptake. In other words, studies generally overestimate the feasibility of bioavailable contaminant stripping. Therefore, a more rigorous approach is advisable to ensure that papers on bioavailable contaminant stripping include relevant information on mass balances. Furthermore, to implement the concept of bioavailable contaminant stripping, regulations must distinguish between the bioavailable fraction and the total metal concentration in soil. Environ Toxicol Chem 2023;42:558–565. © 2022 SETAC [ABSTRACT FROM AUTHOR]

Abstract: Oenothera picensis plants (Fragrant Evening Primrose) grow in the acid soils contaminated by copper smelting in the coastal region of central Chile. We evaluated the effects of the biodegradable chelate MGDA (methylglycinediacetic acid) on copper extraction by O. picensis and on leaching of copper through the soil profile, using an ex situ experiment with soil columns of varying heights. MGDA was applied in four rates: 0 (control), 2, 6 and 10mmol plant−1. MGDA application significantly increased biomass production and foliar concentration, permitting an effective increase in copper extraction, from 0.09mg plant−1 in the control, to 1.3mg plant−1 in the 6 and 10mmol plant−1 treatments. With 10mmol plant−1 rate of MGDA, the copper concentration in the leachate from the 30cm columns was 20 times higher than in the control. For the 60cm columns, copper concentration was 2 times higher than the control. It can be concluded that at increased soil depths, copper leaching would be minimal and that MGDA applications at the studied rates would not pose a high risk for leaching into groundwater. It can thus be stated that applications of MGDA are an effective and environmentally safe way to improve copper extraction by O. picensis in these soils. [Copyright &y& Elsevier]

While plant toxicity reduction remains the primary metric for judging the success of metal immobilization in soil, the suitability of microorganisms as universal indicators of its effectiveness in various contaminated soils remains a point of contention. This study assessed the sensitivity of microbial bioindicators in monitoring metal immobilization success in smelter-impacted soils. It compared plants and microorganisms as indicators of the efficiency of natural Fe–Mn nodules from the Gulf of Finland in immobilizing metals in soils contaminated by a Ni/Cu smelter, on the Kola Peninsula, Murmansk region, Russia. Perennial ryegrass (Lolium perenne) was grown on nodule-amended and control soils. Plant responses in the smelter-impacted soils proved to be sensitive and robust indicators of successful metal immobilization. However, microbial responses exhibited a more complex story. Despite the observed reductions in soluble metal concentrations, shoot metal contents in ryegrass, and significant improvements in plant growth, certain microbial bioindicators were unresponsive to metal immobilization success brought about by the addition of Fe–Mn nodules. Among microbial bioindicators studied, community-level physiological profiling, microbial biomass carbon, and basal respiration were sensitive indicators of metal immobilization success, whereas the number of saprotrophic, oligotrophic, and Fe-oxidizing bacteria and fungi, the biomass of bacteria and fungi, and enzymatic activity were less robust indicators. Interestingly, the correlations between different microbial responses measured were weak or even negative. Some microbial responses also exhibited negative correlations with plant biomass. These findings underscore the need for further research on comparative evaluations of plants and microorganisms as reliable indicators of metal immobilization efficacy in polluted environments. [Display omitted] • Plant biomass was a sensitive and robust indicator of metal immobilization success. • Among 15 microbial indicators, 7 were sensitive to metal immobilization. • In 85% of cases, microbial response correlations were not statistically significant. [ABSTRACT FROM AUTHOR]

The use of zero-valent iron nanoparticles in the remediation of metal-contaminated soils has received considerable attention. Upon introduction into the soil, zero-valent iron particles corrode into iron oxides, known for their high adsorption capacity for potentially toxic metals. While limited research has directly compared zero-valent iron micro- and nanoparticles, it is important to investigate whether particle size contributes to effective soil remediation. This study focuses on elucidating the comparative kinetics of iron corrosion using iron powder and a nano-iron-biochar composite. In a model experiment, these materials were exposed to a cellulose/biochar mixture and peat for five months. Mössbauer spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy with electron diffraction were used to analyze the corrosion products. The results show a slow corrosion rate in the nano-iron-biochar composite in cellulose due to the protective effect of biochar on the embedded iron nanoparticles. In addition, iron corrosion in peat was inhibited, likely due to the presence of humic substances. Transmission electron microscopy after five months of corrosion revealed round metal particles encased in a graphite capsule with visible channels. Large dissolved organic matter molecules in the peat likely block these channels, inhibiting metallic iron corrosion. Consequently, the nano-iron-biochar composite emerges as a slow-reacting option for immobilizing soil metals in peat. This study highlights the need for further research involving long-term field experiments. • Nanoparticles embedded in biochar have slow reactivity. • Biochar protects iron nanoparticles from corrosion. • Iron corrosion was inhibited in peat. • Humic substances might play a role in iron corrosion inhibition. • Long-term field studies would be essential. [ABSTRACT FROM AUTHOR]

While zinc protects plants from copper in hydroponics, its behavior in soil remains unclear. We investigated the potential of zinc sulfate to protect ryegrass from copper toxicity in contaminated soil. Twelve soil treatments combined varying levels of copper oxide (CuO) and zinc sulfate (ZnSO 4). Increasing CuO significantly stunted ryegrass, but adding ZnSO 4 mitigated the effects at each CuO level. ZnSO 4 had no effect in unpolluted conditions. These results, supported by the Terrestrial Biotic Ligand Model, indicate that zinc competes with copper for binding sites, reducing copper uptake by ryegrass and mitigating its toxicity. Application of zinc sulfate to copper-contaminated soils appears promising for ryegrass growth, although field studies are critical to confirm real-world efficacy. • Ryegrass shoot length increased in CuO-treated soils following ZnSO4 addition. • Under unpolluted conditions, ZnSO 4 addition had no statistically significant effect. • The Terrestrial Biotic Ligand Model provides a theoretical framework. • Zn2+ likely competed with Cu2+ for binding sites in ryegrass. • Future field studies will be essential to assess real-world effectiveness. [ABSTRACT FROM AUTHOR]

Carnivores play an important role in ecosystem functioning as apex predators. However, most carnivore species are threatened or have been extirpated in human-dominated landscapes. The Mediterranean region of central Chile is a biodiversity hotspot, but expansion of agricultural areas such as vineyards is degrading wildlife habitat. We estimated the species richness and composition of carnivore communities in remnant fragments of sclerophyllous forest-shrubland in the vineyard landscapes of central Chile to evaluate the effects of human disturbance at different spatial scales. We tested two hypotheses: (1) vineyard landscapes with higher levels of human disturbance support a lower diversity of native carnivores in fragments of remnant native vegetation compared to landscapes with larger areas of natural habitat, and (2) habitat specialists and generalists respond differentially to human influence at the habitat vs landscape spatial scale. We used camera traps at 12 sites across the study area and evaluated the impact of human disturbance indicators on the richness and detection frequency of carnivore species. We found that human population density negatively affected carnivore richness and was associated with a lower detection frequency of the Vulnerable guiña Leopardus guigna. The presence of domestic dogs also had a negative effect on the detection frequency of the guiña and the two native species of foxes, the culpeo Lycalopex culpaeus and South American grey fox Lycalopex griseus. We conclude that protecting remnants of native forest in vineyard landscapes is crucial for carnivore conservation in central Chile. [ABSTRACT FROM AUTHOR]

Plant resistance to metals can be achieved by two strategies, tolerance and avoidance. Although metal tolerance has been broadly studied in terrestrial plants, avoidance has been less considered as a strategy to cope with soil metal pollution. Avoidance may be an effective alternative in herbaceous plants with connected clonal growth in environments having high heterogeneity in soil micro-spatial distribution of available metals and other soil conditions (i.e. organic matter). In this study, we performed a laboratory experiment on clonal growth of Solidago chilensis when exposed to copper-spiked soils (800 mg kg−1) at different depths (0, 2, 5 and 8 cm depth), with (20%) and without addition of organic matter to mimic contrasting microhabitats found at smelter hinterlands (i.e. open bare ground and microhabitats below shrubs). Results showed that plants grown in the 2 cm-depth Cu-spiked soils were able to growth and produce ramets and rhizomes. However, increased Cu uptake of plants determined phytotoxic effects and a reduction in clonal spread in the 5 cm- and 8 cm-depth Cu-spiked soils. Addition of organic matter to the Cu-spiked soil layers allowed clonal spread. Considering that ramet and rhizome production is decreased but not inhibited when copper pollution is restricted to the uppermost soil layer (2 cm depth) and that organic matter eliminated soil copper toxicity allowing normal clonal spread, connected clonal growth may be an effective avoidance mechanism of Solidago chilensis , particularly in environments with high heterogeneity in micro-spatial distribution of metals and organic matter in the soil profile and between microhabitats. Image 1 • Clonal spread was not inhibited in soils polluted in the uppermost layer (2 cm depth). • Organic matter eliminated soil copper toxicity allowing normal clonal spread. • Connected clonal growth is an effective avoidance mechanism in copper-polluted soils. [ABSTRACT FROM AUTHOR]

The structural stability of soil is a physical characteristic that affects soil degradation processes. Calcium‐based amendments, such as calcium carbonate, calcium sulfate, and calcium oxide/hydroxide, have been shown to improve the stability of soil aggregates. This study seeks to determine which calcium‐based soil amendments, and at what concentration, are the most efficient in improving aggregate stability of sandy topsoils derived from granitic and metamorphic parent materials, and to analyze the mechanisms involved. In the pot experiment, soils amended with CaCO3, CaCl2, and CaSO4 did not present significant differences in aggregate stability compared to the control or among each other. In contrast, Ca(OH)2 soil amendment brought the greatest stability to the soil aggregates. A dose of 1% Ca(OH)2 significantly increased the stability of soil aggregates. This effect is due to the reaction of Ca(OH)2 with atmospheric CO2 which leads to the formation of CaCO3, a delayed reaction not showed by the other soil amendments tested. Likewise, the greater solubility of Ca(OH)2 compared to CaCO3 exerts a greater aggregation effect on soil. Thus, the mechanism of action of Ca(OH)2 is related to cementation, rather than flocculation. Future studies should be carried out to demonstrate the effectiveness of Ca(OH)2 under field conditions. [ABSTRACT FROM AUTHOR]

The process of passive revegetation of chemically degraded soils through assisted remediation was assessed under field conditions 6 years after amendment application. In 2009, three treatments were applied: unamended soil (untreated), soil amended with lime, and soil amended with lime + compost. For each field plot, main soil physico-chemical characteristics were determined (pH, organic matter, moisture content at field capacity and exchangeable Cu), while plant colonist development was assessed (plant cover and aboveground biomass). The same evaluation was carried out in 2015. A single application of amendments maintains a neutral pH after 6 years. Thus, neutralization of the soil acidity was stable over time. In 2009, lime + compost was the best treatment for increasing the plant cover. Although the soil organic matter content decreases in year 6, plant cover remained stable over time in this treatment. Incorporation of both organic matter and lime was pivotal at the beginning of the revegetation process, allowing the creation of a potentially self-sustaining ecosystem. No maintenance and/or additional application of amendments was required. Aboveground biomass showed differences between years, possibly explained by changes in climate conditions between 2009 and 2015, and/or changes in nutritional conditions (soil fertility) and plant competition. Plant biodiversity in year 6 was similar for all treatments. The long-term results of plant cover show lime and specially lime + compost as promising amendments to revegetate polluted soils of the Puchuncaví Valley. [ABSTRACT FROM AUTHOR]

According to the Terrestrial Biotic Ligand Model, other cations might compete with Cu +2 for biotic ligand sites and provide a protective effect. In particular, evidence suggests Zn may alleviative Cu toxicity. No study, to the best of our knowledge, has focused explicitly on the alleviating effect Zn might have on Cu toxicity to soil microorganisms in field-contaminated soils. The aim of this study was to investigate the alleviating effect Zn might have on Cu toxicity to symbiotic nitrogen fixation in agricultural soils affected by copper mining in central Chile. The bioassay estimated the symbiotic nitrogen fixation capacity of a population of rhizobia in a specified soil, using the soil as inocula for Phaseolus vulgaris L. grown in a soil-less system (pots with perlite) irrigated with a sterile nitrogen-free nutrient solution. Among all soil physicochemical characteristics, the Cu/Zn ratio best explained changes in symbiotic nitrogen fixation. The effective concentration 50% (EC 50 ) of Cu/Zn ratio for symbiotic nitrogen was equal to 1.2, with 95% confidence interval of 1.0–1.3. Symbiotic nitrogen fixation decreased with increased Cu/Zn ratio, thus suggesting that Zn alleviates Cu toxicity to nitrogen fixing microorganisms. [ABSTRACT FROM AUTHOR]

• Soil science knowledge alone is inadequate for farmers' conservation behavior. • Soil conservation behavior enactment needs a motivational component. • The adoption of ecological farming requires both knowledge and motivation. • Female farmers had higher scores of conservation behavior than males. • Studies in agriculture improve knowledge but not connection to soil. Attaining sustainable agriculture requires acknowledging the impact of human behavior. Despite the pivotal role of soils in agriculture, our understanding of the psychological drivers that motivate farmers to adopt soil conservation practices remains limited. Our objective was to explore the influence of soil science knowledge and connection to soil on farmers' soil conservation behavior. To achieve this goal, we developed scales capable of measuring farmers' soil knowledge, connection to soil, and soil conservation behavior. Our sample comprised 196 individuals from geographically and culturally distinct regions of Chile (the south, center, and north), highlighting the generalizability of our findings. Our target population consisted of farmers who were responsible for making soil management decisions on their farms. Farmers' soil conservation behavior was determined by the combination of their connection to soil (r = 0.37, p < 0.001) and their knowledge of soil science (r = 0.37, p < 0.001). The farmers who utilized ecological management practices exhibited better soil conservation behavior, a stronger connection to land, and a greater level of soil science knowledge (ANOVA, p < 0.05). Therefore, both motivational and cognitive factors are crucial in enacting effective soil conservation behavior. Furthermore, female farmers demonstrated a higher level of soil science knowledge, better soil conservation behavior, and stronger connection to soil than their male counterparts. Finally, pursuing professional studies in agriculture and formal education on soil management do not lead to the development of a stronger motivational connection to soil. This is a concerning outcome that calls for improvements in soil science education. Our study represents a significant contribution to the development of a comprehensive theory of soil conservation behavior, emphasizing the need for a holistic approach that acknowledges the multidimensional nature of farmers' motivational connection to soil and their knowledge of soil science. [ABSTRACT FROM AUTHOR]

To assess the extent of soil contamination with a potentially toxic element, it is important to determine the background concentration of that element in the soil. In this study we decided to investigate the relationship between trace element concentrations in soils and the lithology of their parent rocks. We collected 85 topsoils (0–20 cm) samples from the Petorca, La Ligua, Aconcagua, and Casablanca River basins (Valparaiso region, central Chile). For soil sampling, we chose 11 tributary watersheds free of anthropogenic influence. The areas that contributed to the formation of each alluvial soil were delineated and the parent lithologies were acquired from 1:250,000 geological maps. The results show that the total concentrations of arsenic (As), copper (Cu), lead (Pb), and zinc (Zn) in soil vary considerably among the four river basins studied. Soil concentrations of all elements under study are positively correlated with the presence of andesitic volcanic rocks. Furthermore, soils formed from marine sediments and felsic volcanic rocks had the highest concentrations of Pb and As. The carbonate-bearing marine sediments may have adsorbed As and Pb released by weathering of felsic volcanic rocks found upstream of the study area. In contrast, lithologies dominated by continental sedimentary and plutonic rocks showed negative correlations with the concentrations of As, Cu, Pb, and Zn in the soil. Thus, the differences in soil element concentrations in the watersheds under study were due to the different rock types present in the area. We argue that absolute "one-limit-fits-all" background trace element values may be inadequate to assess the extent of soil contamination. Therefore, it is important to determine background concentrations of soil elements in each river basin in the anthropogenically impacted areas. In contrast, erroneous conclusions can be drawn when background concentrations are determined in one region and then applied in another region that is lithologically different. • Rock lithology affected background element concentrations in the studied soils. • Cu and Zn concentrations correlated positively with andesitic volcanic rocks. • Carbonate-bearing oceanic sediments adsorbed Pb and As released by volcanic rocks. • It is important to establish background concentrations for each river basin. • An absolute "one-limit-fits-all" total metal concentration may be inadequate. [ABSTRACT FROM AUTHOR]

The potential use of zero-valent iron (ZVI) nanoparticles (i.e., <100 nm in size) for the remediation of metal-contaminated soils has sparked a flurry of research in recent years. However, even reading a large number of these papers cannot completely dispel doubts that ZVI nanoparticles are indeed superior to ZVI microparticles (e.g., iron powder or grit) in immobilizing metals and metalloids in soils. Our primary objective was to compare the adsorption properties of iron-based amendments (ZVI micro- and nanoparticles, natural iron oxides) supplied in a biochar matrix in soils contaminated by a copper-nickel (Cu/Ni) smelter on the Kola Peninsula in Russia. The following iron-containing amendments were added to the studied soil: a composite of ZVI nanoparticles and biochar (synthesized by pyrolysis of iron-impregnated biochar), a mixture of iron powder (i.e., ZVI microparticles) with biochar, and a mixture of iron oxides (from natural ferromanganese nodules) with biochar. Perennial ryegrass (Lolium perenne L.) was grown in pots on untreated and amended soils for 21 days under laboratory conditions. In our time-limited study, ZVI nanoparticles did not prove superior to ZVI microparticles or natural iron oxides at immobilizing metals in copper- and nickel-contaminated soil. In other words, ZVI particles size was irrelevant under the experimental setup of this study in its effects on exchangeable metal concentrations, foliar elemental concentrations, and plant growth. • A laboratory study on metal phytotoxicity in a Cu/Ni-contaminated soil was performed. • Zero-valent iron (ZVI) micro- and nanoparticles were compared. • ZVI nanoparticles offered a slight advantage over natural iron oxides. • ZVI nanoparticles offered no advantage over ZVI microparticles. • ZVI nanoparticles exhibited no phytotoxicity. [ABSTRACT FROM AUTHOR]

Metal contamination of soil has become a serious environmental problem worldwide. Many studies have attempted to infer metal ecotoxicity from soil microbial responses. However, much of the data from these studies tends to be inconsistent and difficult to interpret. We hypothesized that microbial response would be a useful indicator of metal toxicity in soils contaminated by copper mining in Chile. Eighty-four topsoils (0–20 cm) were collected from three areas historically contaminated by copper mining (total Cu: 46–1106 mg kg−1, soluble Cu: 0.05–2.3 mg kg−1, pCu2+: 6.3–10, pH: 5.1–7.8, organic matter: 1.1–10%, clay: 0–28%). Based on soil metal concentrations and ecotoxicity thresholds, Cu was expected to be toxic to microorganisms in the studied soils, while the effects of other metals (total Zn: 79-672, As: 1.9–60, Pb: 19-220, Cd: 0.4–5.1 mg kg−1) were expected to be minor. Soil microbial responses (microbial biomass and numbers, nitrogen mineralization and nitrification, and community-level physiological profiles) were also measured. The results showed that the different responses of soil microbes were not correlated with each other. Furthermore, the soil microbial responses were mainly influenced by the physicochemical properties of the soil, not by the metal concentrations in the soil. The effect of copper on the microbial response was either stimulating (positive) or toxic (negative). Of the soil microbial responses measured in this study, only the microbial biomass was useful for calculating dose-response curves. However, the microbial biomass response was not consistent among the different soil copper pools (total copper, soluble copper, and activity of free Cu2+ ions). It is important to emphasize that the thresholds obtained for copper toxicity cannot be adopted in a robust manner because of the different microbial responses in different sampling areas. Thus, in the copper-contaminated soils under study, microbial response was found to be an unreliable indicator of metal toxicity. [Display omitted] • The responses of different soil microorganisms did not correlate with each other. • Soil microbial responses were mainly influenced by soil physicochemical properties. • In some cases, the effect of copper on microbial responses was stimulating. • In other cases, the effect of copper on microbial responses was toxic (negative). • Soil microbial responses were not consistent among the different study areas. [ABSTRACT FROM AUTHOR]

• Comparative analysis of Ny. alba and Nu. lutea floating leaves in the same waterbodies. • Water quality does not affect photosynthetic apparatus of both Ny. alba and Nu. lutea. • Enhanced level of thylakoid photodamage and NPQ in Nu. lutea at high light. • Higher Φ PSII and well developed spongy parenchyma in Ny. alba at similar light. • Differences in photosynthetic apparatus possibly impact species redistribution. Water plants are well adapted to the aquatic environment due to the high plasticity of the photosynthetic apparatus of floating and submerged leaves. A strong decrease or complete disappearance of Nymphaea alba L. populations and their simultaneous replacement by Nuphar lutea L. Smith populations were observed for the last decades in freshwater ecosystems previously described as typical habitats of both species. However, there is no information on which environmental factors and / or interspecies differences between Nu. lutea and Ny. alba induce succession in Nymphaeaceae populations and decline of Ny. alba in natural habitats. We conducted a two-year comparative study of photosynthetic apparatus in floating leaves (chlorophyll fluorescence, leaf anatomy, and chloroplast ultrastructure) of both plant species in water bodies significantly different in the degree of anthropogenic impact and abundance of Nymphaeaceae individuals. It was shown that shifting of parameters of water chemistry induced by increasing concentrations of nitrogen and inorganic phosphorus did not affect photosynthetic processes in both species and confirmed literature data on high tolerance of rooted floating-leaved macrophytes to eutrophication. Irrespective of the water eutrophication level, a more rapid decrease of effective quantum yield (Φ PSII) of Nu. lutea floating leaves at irradiances above 500 μmol m−2 s−1 was observed. Active non-photochemical quenching (NPQ) mechanisms and local extensions of granal thylakoids indicate well-developed photoprotective features of Nu. lutea. The higher value of Φ PSII and diameter of grana in palisade parenchyma and a well-developed spongy parenchyma providing intensive gas exchange indicate better adaptation of photosynthetic apparatus of Ny. alba to high irradiance. In addition, leaf costs and leaf dynamics of Nu. lutea and Ny. alba can impact the outcome of the competition between the two species. [ABSTRACT FROM AUTHOR]

The revegetation of soils affected by historic depositions of an industrial complex in Central Chile was studied. The plant re-colonization from the existing soil seed bank and changes in the physico-chemical properties of the soil were evaluated in field plots amended with lime and/or compost. We found that the application of lime and/or compost decreased the Cu2+ ion activity in the soil solution and the exchangeable Cu in the soil, showing an effective Cu immobilization in the topsoil. Whereas lime application had no effect on plant productivity in comparison with the unamended control, the application of compost and lime+compost increased the plant cover and aboveground biomass due to the higher nutrient availability and water-holding capacity of the compost-amended soils. Although the Cu2+ activity and the exchangeable Cu were markedly lower in the amended soils than in the unamended control, the shoot Cu concentrations of Lolium spp. and Eschscholzia californica did not differ between the treatments. [ABSTRACT FROM AUTHOR]

The article describes a method for antimony speciation in vegetables such as spinach, onions and carrots using high pressure liquid chromatography (HPLC) with hydride generation-atomic fluorescence spectrometry. Extraction techniques used were mechanical agitation and ultrasound then different extraction reagents were evaluated using experimental design methodology.

The Puchuncaví valley, central Chile, has been exposed to aerial emissions from a copper smelter. Nowadays, soils in the surroundings are sparsely-vegetated, acidic, and metal-contaminated, and their remediation is needed to reduce environmental risks. We assessed effectiveness of lime, fly ash, compost, and iron grit as amendments to immobilize Cu in soils and promote plant growth. Amended soils were cultivated with Lolium perenne for 60 days under controlled conditions. Total dissolved Cu and Cu2+ activity in the soil solution, ryegrass biomass, and Cu accumulation in plant tissues were measured. Addition of lime and fly ash decreased Cu concentrations and Cu2+ activity in the soil solution, increased plant biomass, and reduced shoot Cu concentration below 22 mg kg−1 (the phytotoxicity threshold for the species). The most effective amendment with respect to the shoot biomass yield was a combination of lime and compost. Water content of the substrate and the K accumulation were positively correlated with the compost application rate. Compost combined with iron grit decreased dissolved Cu concentrations during the period of highest solubility, i.e. during the first 60 days after the compost application. However, iron grit incorporation into soils amended with lime and compost decreased the shoot biomass of ryegrass. [ABSTRACT FROM AUTHOR]

The Aconcagua River basin (Central Chile) is one of the most important agricultural areas in the country. However, several copper (Cu) mining operations are located in the basin. The objective of the study was to determine Cu toxicity for the earthworm Eisenia fetida (Savigny 1826) in the agricultural soils of the basin. We determined the production of cocoons and juveniles of earthworms in the studied soils. The soils differed in the concentrations of organic matter (OM, range 2-6%), pH (range 7.3-8.3), texture (from loamy sand to clay loam), and total Cu concentrations (range 230-960 mg kg-1). Concentrations of Cu and OM in the soils were the variables that determined the earthworms' biological response. In contrast, pH and texture did not affect this response. Cocoon and juvenile production decreased considerably in soils with elevated Cu concentrations (> 500 mg kg-1), regardless of OM concentrations. Cocoon production decreased in the soils with Cu concentrations below 500 mg kg-1 when OM concentrations were below 3.5%. In contrast, cocoon production did not vary when OM concentrations were above 3.5%. The same effect of OM was observed on juvenile production. In this case, the threshold for OM concentration was 2.5%. It was concluded that it is important to consider OM concentrations in order to predict the biological response of earthworms in these soils. [ABSTRACT FROM AUTHOR]

The establishment of legal limits for soil contamination with trace elements is a global issue that has not yet been resolved. However, the resolution of any global problem begins at the national level. In this vein, we present the case of Chile, the world's leading copper producer, where soil contamination by trace elements in mining areas has been severe. We evaluated the magnitude of the ecological and human health risks from exposure to arsenic (As), copper (Cu), zinc (Zn), and lead (Pb) in soils of the La Ligua and Petorca basins, two important mining areas in Chile. Contrary to what might be expected in soils affected by Cu mining activities, As was identified as the most hazardous element in the studied soils, both in terms of ecological and human health risks. On the other hand, Chile does not currently have specific legislation establishing legal limits on soil contamination with trace elements. Since Chile is geochemically similar to New Zealand, Mexico, and Italy, we used the limits of these three countries as benchmarks. We determined the background concentrations of As, Cu, Zn, and Pb in the soils of the two river basins under study and found that they tend to exceed the limits established by foreign laws. We also found that the differences in background elemental concentrations in the studied soils were primarily due to the varied lithology of soil-forming rocks. This means that absolute "one-limit-fits-all" values of element concentrations may not be adequate to regulate the level of soil contamination in areas affected by mining. As a fundamental first step, it is necessary to establish background soil concentrations of trace elements in each river basin in Chile. It is clear that Chile urgently needs to move from rubber-stamping foreign laws to the development of national legislation on soil metal contamination. [Display omitted] • Foreign laws are not adequate for assessing soil pollution in Chile. • Background trace element concentrations tend to exceed foreign limits. • Rock lithology affected background element concentrations in the studied soils. • It is necessary to develop a sovereign Chilean law on metal-contaminated soils. [ABSTRACT FROM AUTHOR]

Scientists around the world have long been searching for effective strategies to reduce the bioavailability of metals in contaminated soils. In case of metal-spiked soils, some studies have proposed gypsum as a soil amendment to alleviate metal phytotoxicity. However, for real field-collected soils, evidence on the efficacy of gypsum as a metal phytotoxicity amendment is limited. Therefore, the present study was designed to examine the effect of gypsum on plant growth in soils polluted by a copper smelter. We grew perennial ryegrass on untreated and gypsum-treated soils (at a dose of 3% by weight) under laboratory conditions. We found that gypsum had no effect on alleviating metal phytotoxicity in our soils. We also demonstrated – for the first time – that gypsum increased the concentrations of soluble metals in the soil, enhancing metal uptake by plants. The calcium ions from gypsum displace metals in the soil exchangeable complex; however, the metals do not get immobilized in soils because gypsum is a neutral salt. While our results contrast with the Terrestrial Biotic Ligand Model, that Model has never been tested on real industrially polluted soils but only on metal-spiked soils. Our main conclusion is that gypsum is ineffective in alleviating metal phytotoxicity in real industrially polluted soils and, moreover, its use is inappropriate as a soil remediation method, because it increases the environmental hazard rather than reducing it. Our study is the very first attempt to recognize that gypsum is a hazardous material when used to ameliorate soils polluted by metals. [Display omitted] • Gypsum application decreased the pH of the soil horizon O. • Gypsum application did not alleviate metal phytotoxicity in polluted Retisols. • Gypsum application increased the soluble concentrations of Cd, Mn and Pb in the soil. • Gypsum application led to elevated metal concentrations in ryegrass shoots. • Gypsum use for soil remediation can pose an added environmental hazard. [ABSTRACT FROM AUTHOR]

Agricultural use of pesticides has greatly increased worldwide over the last several decades, affecting soil microorganisms. Microbial basal respiration and substrate-induced respiration rates are commonly used to assess the detrimental effects of pesticides on soil quality. The goal of the present study was (1) to compare the impact of different pesticides on soil microbial respiration under field conditions, and (2) to characterize the recovery time of soil microbial respiration after pesticide application. The following pesticides were used in the present study: chlorpyrifos, phosalone, dimethoate (organophosphorus insecticides), λ-cyhalothrin (pyrethroid insecticide), and kresoxim-methyl (fungicide). The application of all the pesticides at commercial doses led to a decrease in soil microbial respiration. The inhibition of basal respiration and substrate-induced respiration rate decreased in the following order: chlorpyrifos > phosalone > dimethoate > λ-cyhalothrin ≈ kresoxim-methyl. Among all the pesticides assessed, chlorpyrifos showed the highest toxicity as well as the highest persistence. Several of the observed results differed greatly from previous studies; thus, local assessments are highly advisable. Given that environmental concerns can be a key decision factor for pesticide selection, assessment of different pesticides—such as undertaken in this study—could help farmers to choose the most appropriate pesticide. • Pesticides at commercial doses led to a decrease in soil microbial respiration. • Chlorpyrifos showed the highest toxicity as well as the highest persistence. • Local assessments of pesticides are highly advisable. • Pesticide assessment help farmers to choose the most appropriate pesticide. [ABSTRACT FROM AUTHOR]

Several studies have attempted to predict the so-called "phytoavailable" fraction by correlating plant responses with different soil metal pools. Most of the data derived from these studies tend to be inconsistent, making interpretations difficult. Thus, the main objective of this study was to determine which soil Cu pool (free Cu2+, salt-exchangeable Cu or total Cu) controls Cu phytotoxicity in soils near a Cu smelter in central Chile. We studied the following traits of the local plant community grown spontaneously on the study site: species richness, shoot biomass, and plant cover. The site was dominated by four early plant colonizers: Eschscholzia californica Cham., Hirschfeldia incana (L.) Lagr.-Fossat, Lolium perenne L., and Vulpia bromoides (L.) Gray. We determined exchangeable soil Cu and activity of free Cu2+ in 0.1 M KNO 3 extracts using soil/solution ratio of 1/2.5. The effect of total soil Cu on plant responses was not significant (p > 0.05). In our field-collected soil series, exchangeable Cu was a better indicator of soil phytotoxicity than either total soil Cu or free Cu2+ in the soil solution. We determined upper critical threshold values for Cu exposure using the three plant traits cited above. The mean values of EC 10 , EC 25 , and EC 50 (effective concentration at 10%, 25%, and 50%, respectively) of exchangeable soil Cu (in μg L−1) were 255, 391, and 533, respectively. The mean EC 10 , EC 25 and EC 50 values of pCu2+ were 7.5, 6.8, and 5.9, respectively. We highlight the importance of further studies on Cu phytotoxicity using actual field-contaminated soils. Image 1 • Exchangeable soil Cu was the best indicator for reduction in the evaluated traits. • Total soil Cu did not predict plant responses. • Free Cu2+ ion activity correlated rather poorly with plant responses. • Shoot biomass was a sensible morphological endpoint. [ABSTRACT FROM AUTHOR]