Nitrification and acidification from urea application in red soil (Ferralic Cambisol) after different long-term fertilization treatments

Purpose

Long-term manure applications can prevent or reverse soil acidification by chemical nitrogen (N) fertilizer. However, the resistance to re-acidification from further chemical fertilization is unknown. The aim of this study was to examine the effect of urea application on nitrification and acidification processes in an acid red soil (Ferralic Cambisol) after long-term different field fertilization treatments.

Materials and methods

Soils were collected from six treatments of a 19-year field trial: (1) non-fertilization control, (2) chemical phosphorus and potassium (PK), (3) chemical N only (N), (4) chemical N, P, and K (NPK), (5) pig manure only (M), and (6) NPK plus M (NPKM; 70 % N from M). In a 35-day laboratory incubation experiment, the soils were incubated and examined for changes in pH, NH₄ ⁺, and NO₃ ^?, and their correlations from urea application at 80 mg N kg^?1(?80) compared to 0 rate (?0).

Results and discussion

From urea addition, manure-treated soils exhibited the highest acidification and nitrification rates due to high soil pH (5.75–6.38) and the lowest in the chemical N treated soils due to low soil pH (3.83–3.90) with no N-treated soils (pH 4.98–5.12) fell between. By day 35, soil pH decreased to 5.21 and 5.81 (0.54 and 0.57 unit decrease) in the NPKM-80 and M-80 treatments, respectively, and to 4.69 and 4.53 (0.43 and 0.45 unit decrease) in the control-80 and PK-80 treatments, respectively, with no changes in the N-80 and NPK-80 treatments. The soil pH decrease was highly correlated with nitrification potential, and the estimated net proton released. The maximum nitrification rates (K _max) of NPKM and M soils (14.7 and 21.6 mg N kg^?1 day^?1, respectively) were significantly higher than other treatments (2.86–3.48 mg N kg^?1 day^?1). The priming effect on mineralization of organic N was high in manure treated soils.

Conclusions

Field data have shown clearly that manure amendment can prevent or reverse the acidification of the red soil. When a chemical fertilizer such as urea is applied to the soil again, however, soil acidification will occur at possibly high rates. Thus, the strategy in soil N management is continuous incorporation of manure to prevent acidification to maintain soil productivity. Further studies under field conditions are needed to provide more accurate assessments on acidification rate from chemical N fertilizer applications.     

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.     

Effects of Single,Binary and Quinary Mixtures of Phenanthrene and Its N-PAHs on <Emphasis Type="Italic">Eisenia fetida</Emphasis> in Soil

It is now acknowledged that aromatic hydrocarbons present in contaminated soils occur in mixtures. The effect of single, binary and quinary mixtures of phenanthrene and selected nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) were investigated on the survival, growth and behavioural index of earthworms (Eisenia fetida) over a 21-day incubation in soil. The results showed that the LC₅₀ values ranged from (not detected) ND–329.3 mg kg^?1 (single mixture), ND–219.8 mg kg^?1 (binary mixtures) to 148.4 mg kg^?1 (quinary mixture), while the EC₅₀ values (based on weight loss) ranged from 13.3–148.4 mg kg^?1 (single mixture), 63.8–148.4 mg kg^?1 (binary mixture) to 24.2 mg kg^?1 (quinary mixture). Greater impacts were recorded where N-PAHs are present with phenanthrene. Further, behavioural index of E. fetida was affected after 24-h exposure to N-PAH-amended soils. Among the N-PAHs however, benzo[h]quinoline recorded the greatest impact on the survival, growth and behavioural index of E. fetida in soil. Findings from this study showed that three ring-N-PAHs are more toxic than phenanthrene as expected from their physico-chemical properties. The binary and quinary mixtures of phenanthrene and N-PAHs in soil intensified toxicity, suggesting that PAHs-N-PAHs mixtures represent greater risk to soil biota.     

Anthropogenic environmental impact in the Mediterranean coastal area of Koper/Capodistria,Slovenia

Purpose

Heavy metal content in soils could be a consequence of geogenic and different anthropogenic sources. In ancient times, soils in the Mediterranean region were affected by agriculture and viticulture, whereas more recently, industry and traffic might contribute more to their pollution. The aim of the study is to determine the extent of multisource heavy metal pollution in soils within the Koper area.

Materials and methods

Along the northern Adriatic Sea coast, around the port city of Koper/Capodistria, 24 topsoil samples were collected; sets of six samples representing four possible pollution sources: intensive agriculture, viticulture, port activities and industry. The parent material of the soil is mainly derived from the Eocene flysch weathered marls and calcarenites and the soil types are eutric. The chemical composition of the samples was determined by ICP-ES for oxides and several minor elements and by ICP-MS for heavy metals. The mineral composition of the selected samples was checked using X-ray powder diffraction. Different statistical analyses were performed on the normally distributed data.

Results and discussion

The mean concentrations of all samples are: Cr 215 mg kg^?1, Ni 81 mg kg^?1, Zn 67 mg kg^?1, Cu 44 mg kg^?1 and Pb and Co 18 mg kg^?1. The ANOVA showed significant differences only in CaO, C/TOT, P₂O₅, Co and Pb between those locations within reach of the different contamination sources. The observed average values of heavy metals are well below Slovenia’s Directive limit for Cu, Pb and Zn, close to but not above it for Co and above the action value for Cr and Ni. According to Igeo, soils from all the sampling locations are uncontaminated with Co, Ni and Pb, and uncontaminated to moderately contaminated with Cu and Zn at one port location, and with Cr at all locations.

Conclusions

The very high Cr and Ni levels could still be geogenic because soils developed on Eocene flysch rocks are enriched in both metals. Cr and Ni are not correlated because of their different levels of sorption and retention in carbonate soils. Cr was retained and concentrated in the sand fraction but Ni has been mobilised in solution. The only serious threat to the environment seems to be an illegal waste dumping area near the port.     

Trace metals in the soils of Water Conservation Area of Florida Everglades: Considerations for ecosystem restoration

Purpose

Inorganic contaminants present a major challenge for the restoration of aquatic ecosystems. The objectives of this study were to determine the extent of trace metal contamination and investigate the influence of different plant communities on trace metal accumulation in the soils of the Florida Everglades.

Materials and methods

Soil samples (n?=?117) were collected from 0 to 10-cm depth using a stainless steel coring device from sites with three dominant plant communities—cattail, sawgrass, and slough—of Water Conservation Area-2A (43,281 ha) of Florida Everglades.

Results and discussion

The mean pH in soils collected from three plant communities was 6.75–6.82, whereas electrical conductivity was slightly greater in the sawgrass (0.69 dS m^?1) than cattail (0.58 dS m^?1) and slough (0.40 dS m^?1). Mean reduction–oxidation potential was greatest in cattail (?113 mV) than sawgrass (?85.3 mV) and slough (?48.3 mV) soils. Among 11 trace metals (As, B, Co, Cr, Cu, Mn, Mo, Na, Ni, Pb, Zn) found in soil samples, Na had the greatest contents and was greater in cattail (2070 mg kg^?1) and sawgrass (1735 mg kg^?1) than slough (1297 mg kg^?1). Four trace metals (B, Cu, Mo, Ni) were significantly greater in cattail than sawgrass and slough. Whereas, Mn was significantly lower in cattail (31 mg kg^?1) than both sawgrass (84 mg kg^?1) and slough (51 mg kg^?1). Cattail also had significantly lower Cr (1.97 mg kg^?1) and Pb (10 mg kg^?1) than sawgrass (Cr 2.5 mg kg^?1; Pb 20.8 mg kg^?1). As (<6.9 mg kg^?1), Co (<1.3 mg kg^?1), and Zn (<17.2 mg kg^?1) were not significantly different among soils collected from three plant community-dominant sites. Contents of Cd and Se were below the method detection limits (Cd 0.01 mg L^?1; Se 0.2 mg L^?1) and are not reported.

Conclusions

None of the trace metals in the soils exceeded the US Environmental Protection Agency sediment toxicity thresholds. Results from this study provided baseline concentrations of trace metals, which can be used to measure the success of restoration efforts in Florida Everglades.

     

Comparative Analysis of Azo Dye Biodegradation by Aspergillus oryzae and Phanerochaete chrysosporium

The paper reports ultraviolet matrix-assisted laser desorption/ionization mass spectroscopy (UVMALDI-MS) protocol for determination of complex heterogeneous emulsion or suspension formulations. The active agents and surfactants are morpholine fungicide fenpropimorph (1), amorolfine (2), tridemorph (mixture of 2,6-dimethyl-4-alkylmorpholins 3–6), 2,6-dimethyl-4-[2-methyl-3-(6-methyl-decahydro-naphthalen-2-yl)-propyl]-morpholine (7), dodemorph (8), main metabolite of 1 fenpropimorph acid (9), sodium dodecyl sulfate (10), and stearate (11). The full method and techniques validation as well as method performance parameters are discussed in terms of their maximal representativeness toward real environmental and foodstuff assay problems. These are additionally complicated by heterogeneous laterally, vertically, and time distribution of pesticide contaminants and their major metabolites in environmental samples. The real environmental heterogeneous distribution is elucidated, studying sterilized soil fractions with particle size 2.0 μm, clay content 11.5 %, silt 23.0 %, sand 8.1 %, and pH?∈ 6.0–8.1. A statistical sampling cluster approach is used. The method performance parameters are concentration LODs of 0.026 mg kg^?1 (res. LOQs 0.08666 mg kg^?1). Concentration linear dynamic ranges are ∈?0.025–7.3 mg kg^?1 (r ²?=?0.99822 and 0.99421) and ∈?2.3–7.4 mg kg^?1 (level of confidence of 99.33₁?%) for complex spiked heterogeneous soil samples. The data illustrates the great capability of method and its promising application for environmental contamination monitoring and controlling programs for assessment.     

The bioaccumulation of Cd in rice grains in paddy soils as affected and predicted by soil properties

Purpose

The area of cadmium (Cd)-contaminated soil in China is increasing due to the rapid development of the Chinese economy. To ensure that the rice produced in China meets current food safety and quality standards, the current soil quality standards for paddy soils urgently need to be updated.

Materials and methods

We conducted a pot experiment with 19 representative paddy soils from different parts of China to study the effects of soil properties on bioaccumulation of Cd in rice grains. The experiment included a control, a low treatment concentration (0.3 mg kg^–1 for pH?<?6.5 and 0.6 mg kg^–1 for pH?≥?6.5), and a high treatment concentration (0.6 mg kg^–1 for pH?<?6.5 and 1.2 mg kg^–1 for pH?≥?6.5) of Cd salt added to soils.

Results and discussion

The results showed that the Cd content in grains of the control and low and high Cd treatments ranged from 0.021 to 0.14, 0.07 to 0.27, and 0.12 to 0.33 mg kg^–1, respectively. Stepwise multiple regression analysis indicated that soil pH and organic carbon (OC) content could explain over 60 % of the variance in the (log-transformed) bioaccumulation coefficient (BCF) of Cd in grains across soils. Aggregated boosted trees analysis showed that soil pH and OC were the main factors controlling Cd bioavailability in paddy soils. Validation of the models against data from recent literature indicated that they were able to accurately predict the BCF in paddy soils.

Conclusions

These quantitative relationships between the BCF of Cd in grains and soil properties are helpful for developing soil-specific guidance on Cd safety threshold value for paddy soils.     

Linking Ni and Cr concentrations to soil mineralogy: does it help to assess metal contamination when the natural background is high?

Purpose

In soils from serpentinitic areas the natural background of Ni and Cr is so high that the assessment of contamination by comparing metal concentrations with some fixed thresholds may give unreliable results. We therefore sought a quantitative relation between serpentines and Ni and Cr concentrations in uncontaminated soils, evaluated if the approach may help in establishing a baseline, and discussed if additional anthropogenic inputs of Ni and Cr can be realistically individuated in these areas.

Materials and methods

We analysed the total, acid-extractable and exchangeable concentrations of Ni and the total and acid-extractable concentrations of Cr in 66 soil horizons, belonging to 19 poorly developed and uncontaminated Alpine soils. The soils had different amounts of serpentines, depending on the abundance of these minerals in the parent material. We calculated an index of abundance of serpentines in the clay fraction by XRD and related total metal contents to the mineralogical index. We then tested the regressions on potentially contaminated soils, developed on the alluvial plain of the same watershed.

Results and discussion

We found extremely high total concentrations of Ni (up to 1,887 mg kg^–1) and Cr (up to 2,218 mg kg^–1) in the uncontaminated soils, but only a small proportion was extractable. Total Ni and Cr contents were significantly related to serpentine abundance (r ²?=?0.86 and 0.74, respectively). The regressions indicated that even small amounts of serpentines induced metal contents above 200 mg kg^–1, and the 95% confidence limits were 75 and 111 mg kg^–1 of Ni and Cr, respectively. When the regressions were tested on the potentially contaminated soils, a good estimate was obtained for Cr, while the Ni concentration was overestimated, probably because of some leaching of this element.

Conclusions

The concentrations of Ni and Cr that can be expected in soils because of the presence of small amounts of serpentines are comparable to the amounts accumulated in the soil because of diffuse contamination and potentially contaminated soils had metal concentrations falling in the range expected from the presence of natural sources. Only in the case of very severe contamination events, the identification of anthropogenic sources adding to the natural background would be feasible.     

Rapid estimation of microbial biomass in acid red soils with and without substrate incorporation

Purpose

A rapid and alternative measurement of microbial biomass in acid red soils with and without substrate incorporation is proposed for soil quality evaluation.

Materials and methods

Soil microbial biomass C (SMBC) and N (SMBN) in 24 typical red soil samples developed from two parent materials (granite and arenaceous shale) were measured using fumigation-extraction followed by dry combustion method in comparison with ultraviolet (UV) spectrophotometry (increase in absorbance at 280 nm, ΔUV₂₈₀). The reliability of microbial biomass estimation by UV spectrophotometry was verified using six representative red soils amended with biochar (0, 1, 3 and 5%) and glucose (0, 100, 500 and 1000 mg kg^?1) separately.

Results and discussion

ΔUV₂₈₀ was strongly correlated with SMBC and SMBN measured by dry combustion, regardless of biochar/glucose incorporation. Validated conversion equations from unamended soil data were dependent on confounding effects of organic C and particle size and can be described as follows: SMBC?=?27.08?×?ΔUV₂₈₀ (R²?=?0.67, n?=?24) and SMBN?=?3.62?×?ΔUV₂₈₀ (R²?=?0.69, n?=?24). Regression models for rapid estimation of microbial biomass in red soils from different parent materials had to be calibrated separately in case of amendments. In most cases, SMBC (R² of 0.75–0.76 and root mean square error (RMSE) of 22.2–29.3 mg kg^?1) and SMBN (R² of 0.74–0.80 and RMSE of 2.60–14.2 mg kg^?1) can be predicted from ΔUV₂₈₀ in biochar/glucose-amended soils using these equations. The slope of the regression of SMBC against ΔUV₂₈₀ shifted in biochar-amended granite soils, mainly due to uncoordinated changes of SMBC in response to the difference in parent material-induced nutrient availability, while shifts of SMBC (or SMBN) against ΔUV₂₈₀ in glucose-amended arenaceous shale soils were attributed to particle size distribution.

Conclusions

Soil microbial biomass (SMBC and SMBN) in red soils can be rapidly predicted by fumigation-extraction with UV spectrophotometry detection and corresponding correction of calibration curves, depending on soil nutrient availability, particle size distribution and organic C levels.

     

Pilot-scale counter-current acid leaching process for Cu,Pb, Sb,and Zn from small-arms shooting range soil

Purpose

The main objective of this study was to evaluate the potential of a counter-current leaching process (CCLP) on 14 cycles with leachate treatment at the pilot scale for Pb, Cu, Sb, and Zn removal from the soil of a Canadian small-arms shooting range.

Materials and methods

The metal concentrations in the contaminated soil were 904?±?112 mg Cu kg^–1, 8,550?±?940 mg Pb kg^–1, 370?±?26 mg Sb kg^–1, and 169?±?14 mg Zn kg^–1. The CCLP includes three acid leaching steps (0.125 M H₂SO₄?+?4 M NaCl, pulp density (PD)?=?10 %, t?=?1 h, T?=?20 °C, total volume?=?20 L). The leachate treatment was performed using metal precipitation with a 5-M NaOH solution. The treated effluent was reused for the next metal leaching steps.

Results and discussion

The average metal removal yields were 80.9?±?2.3 % of Cu, 94.5?±?0.7 % of Pb, 51.1?±?4.8 % of Sb, and 43.9?±?3.9 % of Zn. Compared to a conventional leaching process, the CCLP allows a significant economy of water (24,500 L water per ton of soil), sulfuric acid (133 L H₂SO₄ t^–1), NaCl (6,310 kg NaCl t^–1), and NaOH (225 kg NaOH t^–1). This corresponds to 82 %, 65 %, 90 %, and 75 % of reduction, respectively. The Toxicity Characteristic Leaching Procedure test, which was applied on the remediated soil, demonstrated a large decrease of the lead availability (0.8 mg Pb L^–1) in comparison to the untreated soil (142 mg Pb L^–1). The estimated total cost of this soil remediation process is 267 US$ t^–1.

Conclusions

The CCLP process allows high removal yields for Pb and Cu and a significant reduction in water and chemical consumption. Further work should examine the extraction of Sb from small-arms shooting range.     

Short-term impact of a wildfire on net and gross N transformation rates

Wildfires often modify soil properties, including the N status and net N mineralization rates, but their impacts on gross N fluxes have been scarcely evaluated. We aimed to ascertain the immediate effects of a medium–high severity wildfire on soil N transformations. Net and gross N rates were analytically and numerically (FLUAZ) quantified in burned (BS) and unburned (US) topsoils from the temperate–humid region (NW Spain). Analytical and numerical solutions were significantly correlated for both gross N mineralization (m) (r ²?=?0.815; p?<?0.001) and gross nitrification (n) (r ²?=?0.950; p?<?0.001). In BS, all NH₄ ⁺-N fluxes (net m, gross m and gross NH₄ ⁺-N immobilization, ‘ia’) increased, while those of NO₃ ^?-N decreased (gross n and gross NO₃ ^?-N immobilization, ‘in’) or did not vary (net n). In US and BS, gross m (0.26–3.60 and 4.70–15.42 mg N kg^?1 day^?1, respectively) predominated over gross n (0.026–2.45 and 0.001–0.002 mg N kg^?1 day^?1, respectively), and the same was true for the net fluxes. Compared with the few available data on recently burned soils (m?=?8–55 mg N kg^?1 day^?1; n?=?0.50–1.83 mg N kg^?1 day^?1), our gross m and n rates were similar and very low, respectively; gross n showed that nitrifiers were active in US and also in BS, despite the 98 % reduction observed immediately after the fire. For gross fluxes, m increased more than ia suggesting an NH₄ ⁺-N accumulation, but there is no risk of NO₃ ^?-N leaching because n decreased more than in.     

Distinguishing between natural and anthropogenic sources for potentially toxic elements in urban soils of Talcahuano,Chile

Purpose

The objectives of this study were (1) to determine the concentrations and background concentrations of Ba, Co, Cr, Mn, and Ni in the urban soils of Talcahuano (Chile); (2) assess the level of contamination in the urban soils based on different pollution indexes; and (3) to identify natural or anthropogenic sources in order to obtain a spatial distribution of the pollutants.

Material and methods

A total of 420 samples were collected from the study area as follows: 140 topsoil samples (TS) (0–10 cm), 140 subsoil samples (SS) (10–20 cm), and 140 deep soil samples (DS) (150 cm). The soils were characterized, and the concentrations of Ba, Co, Cr, Mn, and Ni were analyzed by atomic absorption photospectrometry following aqua regia digestion. Correlations and principal component analysis combined with spatial analysis were implemented in order to distinguish the sources and their classification as geogenic or anthropogenic. Several simple and robust statistical methods were applied to datasets in order to explore their potential in the evaluation of a useful and robust background values. The degree of contamination along with the geoaccumulation index, enrichment factor, and contamination factor were also evaluated.

Results and discussion

The median concentrations obtained for various elements includes Ba 461 mg kg^?1, Co 82.7 mg kg^?1, Cr 134 mg kg^?1, Mn 311 mg kg^?1, and Ni 56.1 mg kg^?1. In general, the concentrations of Ba, Co, Cr, Mn, and Ni decrease with depth. Correlations and principal component analysis suggest that Cr, Mn, and Ni are contributed by external sources. The spatial distribution of Cr, Mn, and Ni in TS displays a spatial pattern extending along industrial environments and emission sources.

Conclusions

The estimated background values determined with the iterative 2σ-technique includes 536 mg kg^?1 for Ba, 95.9 mg kg^?1 for Co, 208 mg kg^?1 for Cr, 464 mg kg^?1 for Mn, and 90.5 mg kg^?1 for Ni. The geochemical index, enrichment factor, and the contamination factor register a moderate to considerable contamination in some soil samples.

     

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.

     

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.     

Toxicity of arsenic in relation to soil properties: implications to regulatory purposes

Purpose

The present work evaluates the influence of different soil properties and constituents on As solubility in laboratory-contaminated soils, with the aim of assessing the toxicity of this element from the use of bioassays to evaluate the soil leachate toxicity and thereby propose soil guideline values for studies of environmental risk assessment in soil contamination.

Materials and methods

Seven soils with contrasting properties were artificially contaminated in laboratory with increasing concentrations of As. Samples were incubated for 4 weeks, and afterwards, soil solution (1:1) was obtained after shaking for 24 h. The soil leachate toxicity was assessed with two commonly used bioassays (seed germination test with Lactuca sativa and Microtox ® test with Vibrio fischeri).

Results and discussion

The relationship between soluble As and soil properties indicated that iron oxides and organic matter content were the variables most closely related to the reduction of the As solubility, while pH and CaCO₃ increased As solubility in the soil solutions. Toxicity bioassays showed significant differences between soils depending on their properties, with a reduction of the toxicity in the iron-rich soil (no observed effect concentration (NOEC)?=?150 mg kg^?1) and a significant increase in the highly carbonate samples (NOEC between 15 and 25 mg kg^?1).

Conclusions

Soil guideline values for regulatory purposes usually set a single value for large areas (regions or countries) which can produce over- or underestimation of efforts in soil remediation actions. These values should consider different levels according to the main soil properties controlling arsenic mobility and the soil leachate toxicity.     

Characterization of soil physico-chemical parameters and limitations for revegetation in serpentine quarry soils (NW Spain)

Purpose

Quarrying activities in areas with serpentinized rocks may have a negative impact on plant growth. Quarry soils generally offer hostile environments for plant growth due to their low-nutrient availability, low organic matter, and high-trace metal content.

Materials and methods

In order to determine the factors that can limit plant revegetation, this study was carried out in two serpentine quarries in Galicia (NW Spain): one abandoned in 1999 and the other still active.

Results and discussion

The results show that in soils developed in the abandoned quarry, the limitations for revegetation were: moderate alkaline pH (7.87–8.05), strong Ca/Mg (<1) imbalance, low N (<0.42 mg kg^?1) and P (<2 mg kg^?1) content, and high total heavy-metal content (Co 76–147 mg kg^?1; Cr 1370–2600 mg kg^?1; and Ni 1340–2040 mg kg^?1). The limitations were much less intense in the soils developed in the substratum in the active quarry, which were incipient soils poorly developed and permanently affected by the quarrying activity.

Conclusions

Restoration work should be geared toward establishing a stable diverse vegetation cover, including serpentinophile species, which would provide the necessary modifications to correct nutritive imbalances and improve soil quality.

     

Phosphorus release from cattle manure ash as soil amendment in laboratory-scale tests

ABSTRACT

Excessive application of animal manure to farmland leads to phosphorus (P) loss into the surrounding water. Manure is incinerated to convert it to P-rich ash as a slow-release P fertilizer. However, the potential P loss and P availability for plants from cattle manure ash (CMA) have not been fully understood. The aims of this study were to determine the P release mechanism from CMA and to propose appropriate application rates that mitigate P loss and increase available P to soil in Fukushima, where the soil is deficient in nutrients after the replacement of cesium-137-contaminated soil with sandy mountain soil. Different P fractions in CMA were sequentially extracted with H₂O, 0.5 M NaHCO₃, 0.1 M NaOH, and 1 M HCl. Phosphorus contents in different fractions of CMA were in the order of HCl–P > NaHCO₃–P > H₂O–P > NaOH–P. Water-soluble P release of CMA was also determined by kinetic experiments for 120 h. Results showed that total water-soluble P accounted for a maximum of 2.9% of total P in CMA over 120 h due to recalcitrant P compounds formed through incineration. The Fukushima sandy soil amended with CMA at three application rates, 94, 157, and 314 mg P kg^?1 (corresponding to 300, 500, 1000 kg P₂O₅ ha^?1) was incubated for 56 days. Cattle manure compost and KH₂PO₄ were applied at 157 mg P kg^?1 for comparison. Phosphorus release in water and CaCl₂ solution from ash-amended soil was significantly lower than those from compost and KH₂PO₄-amended soil at the same P application rate of 157 mg P kg^?1 (p < 0.05). Available P in ash-amended soil, determined by Fe-oxide impregnated strips, was not significantly different from those in compost-amended soil after day 7 and KH₂PO₄-amended soil on day 56 at the same P application rate. Thus, CMA reduces P losses from soil to the surrounding water while it increases P availability for plants. In comparison of different rates of CMA, P release in water or CaCl₂ was significantly greater at 314 mg P kg^?1 than at 94 or 157 mg P kg^?1, while the percentage of available P to total P was the lowest at the highest application rate (p < 0.05), suggesting that the best application rates were 94 and 157 mg P kg^?1 in this experiment.     

Root system responses of hyperaccumulator Solanum nigrum L. to Cd

Purpose

Though phytoremediation is an important technology for remedying heavy metal-contaminated soils, hyperaccumulation mechanism, especially in root, is still less known.

Materials and methods

Pot culture experiment was used to explore the tolerance mechanism of a cadmium (Cd) hyperaccumulator Solanum nigrum L. by determining the main root traits compared to the non-hyperaccumulator Solanum melongena L. (cultivar name Liaoqie 3) in the same plant family.

Results and discussion

The total root lengths, total root surface areas, and total root volumes of S. nigrum were not significantly decreased (p?<?0.05) compared to their controls when Cd spikes were lower than 20 mg kg^–1. However, the abovementioned three factors of S. melongena were significantly decreased (p?<?0.05) when 20 mg kg^–1 of Cd was spiked. By contrast, S. nigrum showed stronger tolerance to Cd. In addition, S. nigrum showed all Cd hyperaccumulator characteristics, i.e., a Cd hyperaccumulator. S. melongena was a non-Cd hyperaccumulator.

Conclusions

These results indicated that root trait can be a factor of hyperaccumulation because of strong tolerance to Cd.     

Effect of soil pollution with polycyclic aromatic hydrocarbons on the properties of humic acids

Purpose

Interestingly, soil is the component of the natural environment in which most hydrophobic organic pollution including polycyclic aromatic hydrocarbons (PAHs) gets accumulated. The aim of the present paper was to determine the effect of soil pollution with PAHs on the elemental composition, spectral properties, and hydrophobic and hydrophilic properties of humic acids. The research was performed on different types of soil samples that were artificially polluted with selected PAHs (anthracene, pyrene, fluorene and chrysene).

Materials and methods

The soil samples were polluted with selected PAHs in an amount corresponding to 10 mg PAHs kg^?1. The PAHs-polluted soil samples were incubated for 180 and 360 days at a temperature of 20–25 °C and fixed moisture (50 % of field water capacity). Humic acids (HAs) were extracted from the soil samples prior to the incubation (additionally, soils not polluted with PAHs) and after 180 and 360 days of incubation. For isolated HAs, the following analyses were performed: elemental composition, UV–Vis and IR spectra, susceptibility to oxidation, and hydrophilic (HIL) and hydrophobic (HOB) properties were determined using high-performance liquid chromatography.

Results and discussion

The research demonstrated that introducing anthracene, fluorene, pyrene and chrysene to soil samples resulted in a change in some of the quality parameters of humic acids. However, the intensity and the direction of those changes were determined by soil properties. The changes of the parameters, once PAHs were introduced, that did not depend on the soil properties were ΔA _665u and ΔA _465u (susceptibility to oxidation at wavelengths of 465 and 665 nm) as well as HIL/ΣHOB. The same tendency in changes in the structure of humic acids, once PAHs were introduced, was also observed based on the Fourier transform infrared spectra pattern.

Conclusions

A single pollution of soils with PAHs that leads to changes in the quality parameters of humic acids shows that, as for the soils permanently exposed to pollution with those compounds, significant changes can occur in the properties of humic acids. As a result, it can lead to a change in the functions played by humic acids in the environment.     

Fractionation of Cd and Zn in Cd-contaminated soils amended by sugarcane waste products from an ethanol production plant

Purpose

Sugarcane waste products (boiler ash, filter cake, and vinasse) from an ethanol production plant were used as soil amendments by adding 3 % (w/w) in single and/or in combination, with a research focus towards stabilization of cadmium (Cd) and zinc (Zn) in contaminated soils. The objective of this laboratory study was to evaluate the effects of adding these sugarcane waste products on bioavailability of Cd and Zn over time (aging) in Cd- and Zn-contaminated agricultural soils of Thailand.

Materials and methods

Two agricultural contaminated soils of low (<3 mg kg^?1) and high (10–15 mg kg^?1) Cd concentrations were collected from Tak Province, Northwest Thailand. Fourteen treatments were sampled at 2-week intervals for 84 days for metal bioavailability using BCR extraction procedures (proposed by The Standards, Measurements and Testing Programme of the European Union, SM&T) that determined exchangeable (BCR1), reducible (BCR2), oxidizable (BCR3), and residual (BCR4) fractions, and total concentration was determined using aqua regia digestion and microwave digestion.

Results and discussion

Cd was potentially bioavailable, predominantly in exchangeable (BCR1) and reducible (BCR2) fractions, while the higher contribution of Zn was more prevalent in refractory fractions (BCR2 and BCR4). Aging had an influence on fractionation of Cd and Zn, most notably in the first two fractions (BCR1 and BCR2) of BCR sequential extraction, which resulted in reduction of exchangeable Cd during the first few weeks of incubation (T?=?0 to 28 days). At the end of pot experiment, the exchangeable Cd fraction in the low Cd (LCdS) soil was reduced from 2.3 to 4.7 % and 9.4 to 39.9 % in low and high Cd (HCdS)-contaminated soils, respectively, as compared to nonamended soils.

Conclusions

The observed reduction in exchangeable Cd (BCR1) in the amended soils at the 3 % (w/w) application rate, the low total metal concentrations, and the significant amount of essential plant nutrients (N, P, and K) within these waste products highlight the benefits of amending metal-rich soils with them.