Anthropogenic Heavy Metal Pollution in the Surficial Sediments of the Keratsini Harbor, Saronikos Gulf, Greece

The contents of ten elements [Cd, Pb, W, Zn, Mn, As, Se, Cr, Cu, and organic carbon (C_org)] have been determined in the surficial sediments of Keratsini harbor, Saronikos Gulf, Greece. The contamination of the sediments was assessed on the basis of geoaccumulation index and to corresponding sediment quality guidelines (SQGs) effects range low/effects range median. The results revealed highly elevated Cd, Pb, W, Zn, As, Se, Cr, Cu, and C_org values (Cd, 190–1,763 mg kg^?1; Pb, 521–1,263 mg kg^?1; W, 38–100 mg kg^?1; Zn, 409–6,725 mg kg^?1; Mn, 95–1,101 mg kg^?1; As, not detectable–1,813 mg kg^?1; Se, not detectable–58 mg kg^?1; Cr, 264–860 mg kg^?1; Cu, 195–518 mg kg^?1; and C_org, 0.69–4.41%). The enrichment of metals in the sediments results from the contribution of the central Athens sewage outfall through which the waste of the Attica basin ends up in Keratsini harbor as well as from industrial and ship contaminants.     

EDTA Leaching of Cu Contaminated Soils Using Ozone/UV for Treatment and Reuse of Washing Solution in a Closed Loop

Ozone and UV irradiation were used for oxidative decomposition of EDTA-Cu complexes in washing solution obtained during multi-step leaching of Cu (344,1?±?36.5 mg kg^?1) contaminated vineyard soil with EDTA as a chelant. The released Cu was absorbed from the washing solution on a commercial mixture of metal absorbing minerals, and the treated washing solution then reused for removal of soil residual Cu-EDTA complexes in a closed-loop process. Six consecutive leaching steps (6?×?2.5 mmol kg^?1 of EDTA) removed 38.8 % of Cu from soils, and reduced Cu soil mobility, determined using the toxicity characteristic leaching test (TCLP), by 28.5%. The final washing solution obtained after soil remediation was colourless, with a pH close to neutral (7.5?±?0.2) and with low concentrations of Cu and EDTA (0.51?±?0.22 mg L^?1 and 0.083 mM, respectively). The proposed remediation method has therefore potential not just to recycle and save process water, but also not to produce toxic wastewaters. Soil treatment did not substantially alter the soil properties determined by pedological analysis, and had relatively little impact on soil hydraulic conductivity and soil water sorption capacity.     

Effects of organic material amendment and water content on NO, N2O, and N2 emissions in a nitrate-rich vegetable soil

Amending vegetable soils with organic materials is increasingly recommended as an agroecosystems management option to improve soil quality. However, the amounts of NO, N₂O, and N₂ emissions from vegetable soils treated with organic materials and frequent irrigation are not known. In laboratory-based experiments, soil from a NO ₃ ^? -rich (340 mg N?kg^?1) vegetable field was incubated at 30°C for 30 days, with and without 10 % C₂H₂, at 50, 70, or 90 % water-holding capacity (WHC) and was amended at 1.19 g?C kg^?1 (equivalent to 2.5 t?C ha^?1) as Chinese milk vetch (CMV), ryegrass (RG), or wheat straw (WS); a soil not amended with organic material was used as a control (CK). At 50 % WHC, cumulative N₂ production (398–524 μg N?kg^?1) was significantly higher than N₂O (84.6–190 μg N?kg^?1) and NO (196–224 μg N?kg^?1) production, suggesting the occurrence of denitrification under unsaturated conditions. Organic materials and soil water content significantly influenced NO emissions, but the effect was relatively weak since the cumulative NO production ranged from 124 to 261 μg N?kg^?1. At 50–90 % WHC, the added organic materials did not affect the accumulated NO ₃ ^? in vegetable soil but enhanced N₂O emissions, and the effect was greater by increasing soil water content. At 90 % WHC, N₂O production reached 13,645–45,224 μg N?kg^?1 from soil and could be ranked as RG?>?CMV?>?WS?>?CK. These results suggest the importance of preventing excess water in soil while simultaneously taking into account the quality of organic materials applied to vegetable soils.     

Study of the antimony species distribution in industrially contaminated soils

Purpose

The purpose of the present study was to investigate the distribution of antimony (Sb) and its species in soil fractions in order to understand better the real risk associated with Sb in the environment.

Materials and methods

Nine surface soil samples contaminated from lead/zinc and iron smelting operations and coal fired power plants were examined using: (1) four-step sequential extraction procedure (BCR); (2) two-step sequential extraction including ethylenediaminetetraacetic acid (EDTA), sodium hydroxide (NaOH) and NH₄F; and (3) single extraction with EDTA and NaOH. Liquid phase extraction was used for redox speciation of Sb. The distribution of Sb between soil fulvic and humic acids was determined after their chemical separation. The concentrations of Sb were measured by electrothermal atomic absorption spectrometry.

Results and discussion

The main part of total Sb (2.5–105 mg?kg^?1) was associated with the residual fraction in all soils. The exchangeable/carbonate-bound concentrations were 0.83–4.7 % of total Sb. Up to 6.8 % was in the reducible and up to 1.4 % was in the oxidizable fraction. EDTA removed 7.2–11.4 % of total content. Sb(V) was the predominant form in acetic acid and EDTA extracts. Single extraction with 0.1 mol?l^?1 NaOH released up to 13.7 % of soil antimony. The main part of Sb was complexed to the higher molecular weight fraction of soil-derived humic substances.

Conclusions

For highly contaminated soils, 4 % solubility in acetic acid could represent risk of contamination of ground water under specific conditions. Also, the relatively high phytoavailable Sb (7–11 %) can represent a significant proportion in highly polluted soils. Pentavalent antimony was the main antimony species extracted from soils. The main part of the organically antimony was found to be present as complexes with higher molecular weight humic acids fraction.     

Optimization of arsenic and pentachlorophenol removal from soil using an experimental design methodology

Purpose

In this study, a soil-washing process was investigated for arsenic (As) and pentachlorophenol (PCP) removal from polluted soils. This research first evaluates the use of chemical reagents (HCl, HNO₃, H₂SO₄, lactic acid, NaOH, KOH, Ca(OH)₂, and ethanol) for the leaching of As and PCP from polluted soils.

Materials and methods

A Box–Behnken experimental design was used to optimize the main operating parameters for soil washing. A laboratory-scale leaching process was applied to treat four soils polluted with both organic ([PCP] _i ?=?2.5–30 mg kg^?1) and inorganic ([As] _i ?=?50–250 mg kg^?1, [Cr] _i ?=?35–220 mg kg^?1, and [Cu] _i ?=?80–350 mg kg^?1) compounds.

Results and discussion

Removals of 72–89, 43–62, 52–68, and 64–98 % were obtained for As, Cr, Cu, and PCP, respectively, using the optimized operating conditions ([NaOH]?=?1 N, [cocamidopropylbetaine] _i ?=?2 % w w^?1, t?=?2 h, T?=?80 °C, and PD?=?10 %).

Conclusions

The use of NaOH, in combination with the surfactant, is efficient in reducing both organic and inorganic pollutants from soils with different levels of contamination.     

Evaluation of Pb Phytoremediation Potential in Buddleja asiatica and B. paniculata

The phytoremediation potential for Pb of Buddleja asiatica (a wild species) and a closely related cultivated species, B. paniculata, was investigated by means of field survey, hydroponic and pot experiments, and field trial experiments. Field surveys showed that B. asiatica had an extraordinary accumulation capacity and tolerance for Pb. Plants grown in soil with 2,369.8–206,152 mg kg^?1 total Pb accumulated 1,835.5–4,335.8 mg kg^?1 Pb in their shoots. Under hydroponic conditions (10, 20 mg l^?1 Pb), both B. asiatica and B. paniculata showed unusually high concentrations of Pb in their roots (12,133–21,667 mg kg^?1) and increased biomass production. A pot experiment in a greenhouse without any soil amendments was conducted on three different soils with various Pb contents (10,652, 31,304, 89,083 mg kg^?1) for 3 months. The results showed that both species of Buddleja had an increase in the biomass similar to the control plants. There was a slight decrease in survival rates of plants grown in soil with 89,083 mg kg^?1 Pb content. A field trial experiment was conducted for 6 months at three sites around the Pb mine area in which plants were provided with Osmocote fertilizer. Both Buddleja species showed 100% survival, increased biomass production and phytoextraction capacity (TF 1.1–2.3) when grown in soil with Pb content of 94,584–101,405 mg kg^?1. Plants accumulated 2,273–3,675 mg kg^?1 Pb in their shoots. The results suggest these Buddleja plants are suitable for use in the phytoremediation of Pb-contaminated soil.     

Heavy‐Metal Inhibition of Nitrification in Selected Iowa Soils Treated with Stay‐N 2000

Abstract

Heavy‐metal inhibition of nitrification in soils treated with reformulated nitrapyrin was investigated. Clarion and Okoboji soils were treated with ammonium sulfate [(NH₄)₂SO₄] and a nitrification inhibitor. Copper(II) (Cu), Zinc(II) (Zn), Cadmium(II) (Cd), or Lead(II) (Pb) were added to each soil. A first‐order equation was used to calculate the maximum nitrification rate (K _max), duration of lag period (t′), period of maximum nitrification (Δt), and the termination period of nitrification (t _s). In the Clarion soil, the K _max decreased from 12 mg kg^?1 d^?1 without the nitrification inhibitor to 4, 0.25, 0.86, and 0.27 mg kg^?1 d^?1, respectively, when the inhibitor and Cu, Zn, Pb, or Cd were applied. In the Okoboji soil, K _max decreased from 22 mg kg^?1 d^?1 with no inhibitor to 6, 3, 4, and 2 mg kg^?1 d^?1, respectively, when an inhibitor and Cu, Zn, Pb, or Cd were added. The t′ varied from 8 to 25 d in the Clarion soil and from 5 to 25 d in the Okoboji soil, due to addition of Cu, Zn, Pb, or Cd and the inhibitor.     

Nitrification,acidification, and nitrogen leaching from subtropical cropland soils as affected by rice straw-based biochar: laboratory incubation and column leaching studies

Purpose

Few studies have examined the effects of biochar on nitrification of ammonium-based fertilizer in acidic arable soils, which contributes to NO₃ ^? leaching and soil acidification.

Materials and methods

We conducted a 42-day aerobic incubation and a 119-day weekly leaching experiment to investigate nitrification, N leaching, and soil acidification in two subtropical soils to which 300 mg N kg^?1 ammonium sulfate or urea and 1 or 5 wt% rice straw biochar were applied.

Results and discussion

During aerobic incubation, NO₃ ^? accumulation was enhanced by applying biochar in increasing amounts from 1 to 5 wt%. As a result, pH decreased in the two soils from the original levels. Under leaching conditions, biochar did not increase NO₃ ^?, but 5 wt% biochar addition did reduce N leaching compared to that in soils treated with only N. Consistently, lower amounts of added N were recovered from the incubation (KCl-extractable N) and leaching (leaching plus KCl-extractable N) experiments following 5 wt% biochar application compared to soils treated with only N.

Conclusions

Incorporating biochar into acidic arable soils accelerates nitrification and thus weakens the liming effects of biochar. The enhanced nitrification does not necessarily increase NO₃ ^? leaching. Rather, biochar reduces overall N leaching due to both improved N adsorption and increased unaccounted-for N (immobilization and possible gaseous losses). Further studies are necessary to assess the effects of biochar (when used as an addition to soil) on N.     

Toxic Metal Removal from Polluted Soil by Acid Extraction

Sulfuric acid leaching is a promising technique to extract toxic metals from polluted soils. The objective of this study was to define the optimum sulfuric acid leaching conditions for decontamination of the fine particle fraction (<125???m) of an industrial soil polluted by Cd (16.8?mg?kg^?1), Cu (3,350?mg?kg^?1), Pb (631?mg?kg^?1) and Zn (3,010?mg?kg^?1). Batch leaching tests in Erlenmeyer shake flasks showed that a soil pulp pH between 1.5 and 2.0 using a solid concentration (SC) ranging from 5 to 20?% is adequate to efficiently solubilize toxic metals. Leaching tests performed at different temperatures (20, 40, 60 and 80?°C) also revealed that it is not beneficial to heat the soil suspension during the leaching treatment. The application in a 1-L stirred tank reactor of five consecutive 1-h leaching steps at 10?% SC and ambient temperature, followed by three water washings steps resulted in the following metal extraction yields: 30?% As, 90?% Cd, 43?% Co, 7?% Cr, 88?% Cu, 75?% Mn, 26?% Ni, 18?% Pb and 86?% Zn. The decontaminated soil conformed to Quebec norms for commercial and industrial use of soil.     

Trace element content in soil after a sediment-laden flood in northern Chile

Purpose

Arid and hyper-arid zones worldwide are reservoirs of chemical compounds, among them are various trace elements. With climate change, abnormal precipitation is occurring in arid and hyper-arid mountainous zones, which in turn is increasing the displacement of trace elements from mountainous to populated areas. The objective of this study was to evaluate trace element displacement of a sediment-laden flood in the Copiapó River Basin on March 24–25, 2015.

Materials and methods

Sixty topsoil samples were taken from 20 agricultural fields. Soil organic matter content, pH, electrical conductivity, and particle size were determined according to accepted procedures in Chile. Samples were acid-digested to determine total Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, and Zn content by flame atomic absorption spectroscopy. Hydride generation AAS was used for As and Se determination, and Hg was quantified by cold vapor AAS. Detection limits were 0.2, 0.05, 0.1, and 5.0 mg kg^?1 for Cd, Hg, Se, and Mo, respectively. Correlation and principal component analyses were made, and theoretical distribution functions were fitted to each element.

Results and discussion

Metal concentration showed a strong correlation between SOM and particle size, explaining the first component from the principal component analysis. All trace elements correlated well between each other except for Mo and Se. Mo values were consistently below detection levels (<5.0 mg kg^?1). Expected values for the elements were (95% of probability): 13–37 g Al kg^?1, 10–50 mg As kg^?1, <0.2–0.6 mg Cd kg^?1, 13–25 mg Cr kg^?1, 27–281 mg Cu kg^?1, 27–40 g Fe kg^?1, <0.05–6.5 mg Hg kg^?1, 516–1.080 mg Mn kg^?1, 7–24 mg Ni kg^?1, 13–50 mg Pb kg^?1, 0.2–0.6 mg Se kg^?1, and 61–172 mg Zn kg^?1. Concentrations of As, Cu, and Hg were consistently above national standards.

Conclusions

The authors conclude that the trace element contents in sediments deposited by the event are within expected values based on soil data in Chile.

     

Bulk density and content,density and stock of carbon,nitrogen and heavy metals in vegetable patches and lawns of allotments gardens in the northwestern Ruhr area,Germany

Purpose

In view that soils are bodies and that processes such as storage and release of water, carbon, nutrients and pollutants, and aeration and rooting happen in these bodies, it is of interest to know the density of elements and compounds in soils. On the basis of soil bulk and element density of organic carbon (OC), N, and heavy metals in soils and of horizon thickness, stocks of these elements for garden soils were calculated.

Materials and methods

Fourteen gardens in four allotments of the northwestern part of the Ruhr area, Germany were investigated. The research included 14 vegetable patches, 13 lawns, 2 compost heaps, and 1 meadow. Volume samples were taken. The soil analysis included pH, soil bulk density, and OC, N, Pb, Cd, Zn, Cu, and Ni contents.

Results and discussion

The soils were from sandy loam to loamy sand. The pH was slightly acid and C/N ratio about 20. Soil bulk density was between 0.8 and 1.4 g cm^?3 and mean bulk density was 1.1 g cm^?3. Mean OC content was for compost 7.4 %, vegetable patches 5.2 % (0–30 cm depth), and lawns and meadow 5.8 and 5.2 % (0–5 cm depth). OC density for compost was 76 mg cm^?3, vegetable patches 56 mg cm^?3, and lawns 67 mg cm^?3 (0–5 cm). Mean OC stock in 0–30 cm soil depth in vegetable patches was 16.4 kg m^?2, lawns 15.5 kg m^?2, and meadow 11.1 kg m^?2. N contents were between 0.06 and 0.46 %. For compost, the mean was 0.39 %, vegetable patches 0.27 % (0–30 cm), lawn 0.28 %, and meadow 0.26 % (0–5 cm). Mean stock of N in 0–30 cm depth for vegetable patches was 0.84 kg m^?2, lawn 0.76 kg m^?2, and meadow 0.55 kg m^?2. For heavy metals in compost, vegetable patches, lawn and meadow, Cd contents were in the range of 1.7 to 3.0 mg kg^?1, Pb 49 to 152 mg kg^?1, and Zn 52 to 1830 mg kg^?1. The amounts stored per square meters in 30 cm depth were for Cd 0.6–1.1 g, Pb 15–52 g, Zn 41–440 g, Cu 4–39 g, and Ni 1–8 g.

Conclusions

Allotment gardens have a high capacity to store CO₂ as OC. Roughly, there will be 7–8 million tons of OC stored in the 1.3 million allotment gardens of Germany. The high amount of 8000 kg N ha^?1 could damage the groundwater when released by wrong soil management. Cd, Zn, Pb, Cu, and Ni amounts of 7.8, 1000, 300, 135, and 30 kg ha^?1, respectively, are a lasting burden.

     

Geochemistry of Manganese in Neutral to Alkaline Soils of Punjab,Northwest India and Its Availability to Wheat and Rice Plants

Manganese (Mn) release in 18 soil–water suspensions after their equilibration for 24 and 240 h periods at 25°C was studied in a laboratory experiment. Total dissolved Mn released into the soil solution was observed to increase from a range of 0.03–0.41 mg L^?1 (mean = 0.13 mg L^?1) to a range of 0.45–44.44 mg L^?1 (mean = 22.40 mg L^?1) with the increase in incubation periods from 24 to 240 h, respectively. The increase in Mn released was observed to be related with the redox potential (pe) induced by incubation conditions. After 24 h of equilibration period, pe of soil–water suspension ranged from ?1.75 to 0.77 (mean = ?0.24). Increasing the incubation period to 240 h, pe of soil–water suspensions declined in the range of ?4.49 to ?2.74 (mean = ?3.29). Laboratory results of redox pe and corresponding dissolved manganese concentrations of some soil–water equilibrated systems were compared with the leaf Mn content in wheat and rice plants grown in the fields, from where soil samples were collected for laboratory experiment. These results demonstrated that decline in pe due to longer equilibration period (240 h) of soil–water systems in the laboratory experiment or keeping standing water for a couple of weeks in the fields for cultivation of rice crop results in higher release of Mn and eventually its higher uptake in rice than in wheat plants. Leaf manganese content in rice ranged from 94 to 185 mg kg^?1, which was markedly higher than its range from 25 to 62 mg kg^?1 found in the wheat grown at 10 different sites. Pourbaix diagrams were drawn for different soil–water systems containing carbonate, phosphate, or sulfate along with manganese. The presence of carbonate and phosphate anions along with manganese oxides minerals in the soil–water systems of all soils results in its precipitation as MnCO₃ and MnHPO₄, respectively, in both oxidized and reduced soil field environment. In Punjab, wheat and rice crops are generally cultivated on soils heavily fertilized with P fertilizers. The presence of phosphate anion with manganese oxides minerals in the soil–water systems of all soils results in the precipitation MnHPO₄ in both oxidized and reduced soil field environment. Thus, in P-fertilized soil, MnHPO₄ compound is even more predominant than aqueous Mn²⁺ and its solubility actually controlled the availability of Mn²⁺ to plants.     

Impact of Tropical Ecosystem on the Migrational Behavior of K-40, Cs-137, Th-232 U-238 in Perennial Plants

A comprehensive study was conducted to determine the soil to plant transfer factor (TF_S–P) of K-40, Cs-137, Th-232 and U-238 in perennial plants from accessible areas of Mumbai, using high-resolution γ spectrometry. A total of 50 soil and 150 plants samples were collected from all over the Mumbai region where lithology is dominated by basaltic rocks. The mean concentration values for K-40, Cs-137, Th-232 and U-238 in soil was 170.06?±?65.36, 5.19?±?1.20, 25.72?±?6.262 and 10.21?±?2.82 Bq kg^?1 respectively, whereas in case of plants the mean concentration values were determined to be 181.82?±?18.50, 0.44?±?0.14, 0.84?±?0.19 and 0.79?±?0.22 Bq kg^?1 respectively. The mean activity ratio of Th-232/U-238 in plants is 1.06 while in soil the ratio is 2.5. The soil to plant transfer factor (TF_S–P) calculated for K-40, Cs-137, U-238 and Th-232 are 1.05, 0.076, 0.071 and 0.031 respectively. Higher value of TF_S–P for K-40, which is an integral part of stable potassium clearly indicates the physiological need of stable potassium, for maintaining the different biological mechanisms of perennial plants under tropical conditions.     

The effect of concentrations and properties of phenanthrene, pyrene, and benzo(a)pyrene on desorption in contaminated soil aged for 1 year

Purpose

The choice and timing of microorganisms added to soils for bioremediation is affected by the dominant bioavailable contaminants in the soil. However, changes to the concentration of bioavailable PAHs in soil are not clear, especially when several PAHs coexist. This study investigated the effects of PAH concentration and chemical properties on desorption in meadow brown soil after a 1-year aging period, which could reflect changes of PAH bioavailability during bioremediation.

Materials and methods

Based on the percentage of different molecular weights in a field investigation, high-level contaminated soil (HCS) and low-level contaminated soil (LCS) were prepared by adding phenanthrene (PHE), pyrene (PYR) and benzo(a)pyrene (BaP) to uncontaminated meadow brown soil. The concentrations of HCS and LCS were 250 mg?kg^?1 (PHE, PYR, and BaP: 100, 100, and 50 mg?kg^?1) and 50 mg?kg^?1 (PHE, PYR, and BaP: 20, 20, and 10 mg?kg^?1) respectively. The soils were aged for 1 year, after which desorption was induced by means of a XAD-2 adsorption technique over a 96-h period.

Results and discussion

The range of the rapidly desorbing fraction (F _rap) for PHE, PYR, and BaP in HCS and LCS was from 1.9 to 27.8 %. In HCS, desorption of PYR was most difficult, and the rate constant of very slow desorption (K _vs) of PYR was 8 orders of magnitude lower than that of BaP, which had similar very slow desorbing fractions (49.8 and 50.5 %, respectively). However, in LCS, desorption of PYR was the easiest; the K_vs of PYR was 8–10 orders of magnitude higher than those of PHE and BaP. In HCS, the time scale for release of 50 % of the PAHs was ranked as BaP?>?PYR?>?PHE, while in LCS this was BaP?>?PHE?>?PYR.

Conclusions

The combined effect of PAH concentrations and properties should be taken into account during desorption. The desorption of PAH did not always decrease with increasing molecular weight, and the desorption of four-ring PAHs might be special. These results are useful for screening biodegrading microbes and determining when they should be added to soils based on the dominant contaminants present during different periods, thus improving the efficiency of soil bioremediation.     

Transfer of 137Cs and 40K from Agricultural Soils to Food Products in Terrestrial Environment of Tarapur, India

The ¹³⁷Cs and ⁴⁰K activities and transfer factors from soil to vegetables, grass, and milk from villages located around Tarapur Atomic Power Station (TAPS) were determined using high-resolution gamma spectrometry. A total of 32 soil, 21 vegetable, 23 dry paddy grass, and 23 milk samples were collected from 23 different agricultural farms from various villages around TAPS to determine transfer factors for natural environment. The mean concentration values for ¹³⁷Cs and ⁴⁰K in soil, grass, and milk were 2.39?±?0.86 Bq kg^?1, 0.31?±?0.23 Bq kg^?1, and 12.4?±?5.7 mBq L^?1 and 179?±?31 Bq kg^?1, 412?±?138 Bq kg^?1, and 37.6?±?9.3 Bq L^?1, respectively, for soil?Cgrass?Cmilk pathway. In the soil?Cvegetation pathway, the mean concentrations values for ¹³⁷Cs and ⁴⁰K were 2.15?±?1.04 Bq kg^?1, 16.5?±?7.5 mBq kg^?1, and 185?±?24, 89?±?50 Bq kg^?1, respectively. The evaluated mean transfer factors from soil?Cgrass, grass?Cmilk, and soil?Cvegetation for ¹³⁷Cs were 0.14, 0.0044, and 0.0073 and that of ⁴⁰K were 2.42, 0.0053, and 0.49, respectively. Only 15 out of total 44 milk and vegetable samples were detected positive for ¹³⁷Cs, indicating a very low level of bioavailability.     

Fractionation of chromium in tannery sludge-amended soil and its availability to fenugreek plants

Purpose

Fenugreek (Trigonella foenum-graecum L.) is a medicinal plant with antidiabetic effects. Chromium has been related to better glucose tolerance in humans. The objective of this study was to determine whether tannery sludge could be used for Cr biofortification of fenugreek.

Materials and methods

Soil was mixed with tannery sludge containing 6.03 g Cr kg^?1. All Cr was in the form of Cr(III). Three treatments were disposed: control without sludge, and two treatments with 10 and 20 g sludge kg^?1, respectively. Control and the 10 g sludge kg^?1 treatments received NPK fertilizer to adjust the concentrations of major mineral nutrients to similar levels in all treatments. Soils were potted and planted with fenugreek. Plants harvested at the initial flowering stage were analysed for total Cr, Fe, Zn and Pb. Sequential soil extraction was applied to obtain operationally defined soil Cr fractions.

Results and discussion

Total Cr in all treatments was below or within the allowable range for agricultural soils (100–150 mg kg^?1). In control soils, most Cr was in the residual fraction (HF/HClO₄ digest). Tannery sludge-amended soils incorporated most Cr into the moderately reducible fraction (oxalic acid/ammonium oxalate extract). In fenugreek shoots, Cr concentrations reached 3.2 mg Cr kg^?1, a higher concentration than that reported for other leafy vegetables. Lead concentrations in plant shoots from this treatment were enhanced but hardly exceeded 1 mg Pb kg^?1.

Conclusions

Tannery sludge-amended soils containing Cr within the range of permissible concentrations can increase shoot Cr in fenugreek. Only sludge with low Pb concentrations should be used for Cr biofortification of fenugreek.     

Potential of Borago officinalis, Sinapis alba L. and Phacelia boratus for Phytoextraction of Cd and Pb from Soil

Heavy metal phytoextraction is a soil remediation technique, which makes use of plants in removing contamination from soil. The plants must thus be tolerant to heavy metals, adaptable to soil and climate characteristics, and able to take up large amounts of heavy metals. Most of the high biomass productive plants such as, maize, oat and sunflower are plants, which do not grow in cold climates or need intensive care. In this study three “weed” plants, Borago officinalis; Sinapis alba L. and Phacelia boratus were investigated for their ability to tolerate and accumulate high amounts of Cd and Pb. Pot experiments were performed with soil containing Cd and Pb at concentrations of up to 180 mg kg^?1 and 2,400 mg kg^?1 respectively. All three plants showed high levels of tolerance. Borago officinalis; and Sinapis alba L. accumulated 109 mg kg^?1 and 123 mg kg^?1 Cd, respectively at the highest Cd spiked soil concentration. Phacelia boratus reached a Cd concentration of 42 mg kg^?1 at a Cd soil concentration of 100 mg kg^?1. In the case of Pb, B. officinalis and S. alba L. displayed Pb concentrations of 25 mg kg^?1 and 29 mg kg^?1, respectively at the highest Pb spiked soil concentration. Although the Pb uptake in P. boratus reached up to 57 mg kg^?1 at a Pb spiked soil concentration of 1,200 mg kg^?1, it is not suitable for phytoextraction because of its too low biomass.     

Sorption isotherms and kinetics of Sb(V) on several Chinese soils with different physicochemical properties

Purpose

Sorption of antimony on soils is the primary factor that influences its immobilization and migration in the environment. In the present study, the sorption of Sb(V) onto seven Chinese soils with different physicochemical properties was investigated for exploring the relationship between the sorption capacity of Sb(V) and the physicochemical properties of the soils.

Materials and methods

Sorption isotherms and kinetics experiments were performed to ascertain the sorption capacity and the kinetic rate, respectively. The relationship between the sorption capacity of Sb(V) and the physicochemical properties of the soils was analyzed by multiple linear regressions.

Results and discussion

The results showed that the sorption isotherms fitted with both the Langmuir and Freundlich equations very well (R ²?=?0.936–0.997), and the sorption kinetic of Sb(V) onto the seven Chinese soils followed a pseudo-second-order reaction. The maximum sorption capacity of Sb(V) on the soils ranged from 134 to 1,333 mg?kg^?1. Nearly 94 % of the variability in maximum sorption of Sb(V) modeled by Freundlich equation could be described by Fe_DCB (dithionite–citrate–bicarbonicum extractable), and nearly 98 % of the variability could be described by Fe_DCB and Al_DCB.

Conclusions

Multiple linear regressions can be successfully applied to analyzing the relationship between sorption capacity and soil properties. Fe_DCB and Al_DCB played important roles in Sb(V) sorption onto soils. It would be useful to understand the environmental behaviors of Sb and for the implementation of risk assessment management and remediation strategies of Sb.     

Tillage system affects fertilizer-induced nitrous oxide emissions

Since the development of effective N₂O mitigation options is a key challenge for future agricultural practice, we studied the interactive effect of tillage systems on fertilizer-derived N₂O emissions and the abundance of microbial communities involved in N₂O production and reduction. Soil samples from 0–10 cm and 10–20 cm depth of reduced tillage and ploughed plots were incubated with dairy slurry (SL) and manure compost (MC) in comparison with calcium ammonium nitrate (CAN) and an unfertilized control (ZERO) for 42 days. N₂O and CO₂ fluxes, ammonium, nitrate, dissolved organic C, and functional gene abundances (16S rRNA gene, nirK, nirS, nosZ, bacterial and archaeal amoA) were regularly monitored. Averaged across all soil samples, N₂O emissions decreased in the order CAN and SL (CAN?=?748.8?±?206.3, SL?=?489.4?±?107.2 μg kg^?1) followed by MC (284.2?±?67.3 μg kg^?1) and ZERO (29.1?±?5.9 μg kg^?1). Highest cumulative N₂O emissions were found in 10–20 cm of the reduced tilled soil in CAN and SL. N₂O fluxes were assigned to ammonium as source in CAN and SL and correlated positively to bacterial amoA abundances. Additionally, nosZ abundances correlated negatively to N₂O fluxes in the organic fertilizer treatments. Soils showed a gradient in soil organic C, 16S rRNA, nirK, and nosZ with greater amounts in the 0–10 than 10–20 cm layer. Abundances of bacterial and archaeal amoA were higher in reduced tilled soil compared to ploughed soils. The study highlights that tillage system induced biophysicochemical stratification impacts net N₂O emissions within the soil profile according to N and C species added during fertilization.     

Chelate-enhanced phytoextraction and phytostabilization of lead-contaminated soils by carrot (Daucus carota)

The objective of this study was to study the influence of different ethylenediamine tetraacetate (EDTA), nitrilotriacetic acid (NTA) and oxalic acid (HOx) concentrations on tolerance and lead (Pb) accumulation capacity of carrot (Daucus carota). The results indicated that by increasing Pb, NTA and HOx concentrations in the soil, the shoot, taproot and capillary root dry matters increase effectively. In contrary, EDTA caused to reduce capillary roots biomass. EDTA was more effective than NTA and HOx in solubilizing soil Pb. The highest Pb content in shoots (342.2 ± 13.9 mg kg^?1) and taproots (301 ± 15.5 mg kg^?1) occurred in 10 mM EDTA, while it occurred for capillary roots (1620 ± 24.6 mg kg^?1) in 5 mM HOx, when the soil Pb concentration was 800 mg kg^?1. The obtained high phytoextraction and phytostabilization potentials were 1208 (±25.6) and 11.75 (±0.32) g Pb ha^?1 yr^?1 in 10 mmol EDTA kg^?1 soil and no chelate treatments, respectively. It may be concluded that chelate application increases Pb uptake by carrots. Consequently, this plant can be introduced as a hyperaccumulator to phytoextract and phytostabilize Pb from contaminated soils.