Greenhouse evaluation of EDTA effectiveness at enhancing Cd,Cr, and Ni uptake in <Emphasis Type="Italic">Helianthus annuus</Emphasis> and <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis>

Background, Aims and Scope  Phytoremediation is a promising means for the treatment of heavy metal contamination. Although several species have been identified as hyperaccumulators, most studies have been conducted with only one metal. Experiments were conducted to investigate the ability of Helianthus annuus and Thlaspi caerulescens to simultaneously uptake Cd, Cr and Ni. Materials and Methods  The efficiency of plants grown in a sandy-loam soil was investigated. The ability of two EDTA concentrations (0.1 and 0.3 g kg⁻¹) for enhancing the phytoremediation of Cd, Cr and Ni at two different metal concentrations (24.75 mg kg⁻¹ and 90 mg kg⁻¹) was studied. Results   Thlaspi hyperaccumulated Ni with 0.1 g kg⁻¹ EDTA. When the EDTA dosage was increased to 0.3 g kg⁻¹, Thlaspi was able to hyperaccumulate both Ni and Cr. Since Thlaspi is a low-biomass plant, it was considered insufficient for full-scale applications. Helianthus annuus hyperacummulated Cr (with 0.1 g kg⁻¹ EDTA) and Cd (0.3 g kg⁻¹ EDTA). Discussion  When the contamination was 8.25 mg kg⁻¹ per metal, the total metal uptake was 10–25% (1.35 to 2.12 mg) higher and had the same uptake selectivity (Cr>>Cd>Ni) for both EDTA levels. It was hypothesized that complexation with EDTA interfered with Ni translocation. For these experiments, the optimal results were obtained with the H. annuus-0.1 g kg⁻¹ EDTA combination. Conclusions  Although the use of EDTA did increase the amount of metal that could be extracted, care should be taken during in-situ field applications. Chelators can also increase the amount of metals that are leached past the root zone. Metal leaching and subsequent migration could lead to ground water contamination as well as lead to new soil contamination. Recommendations and Perspectives  Additional research to identify the optimal EDTA dosage for field applications is warranted. This is necessary to ensure that the metals do not leach past the root zone. Identification of a plant that can hyperaccumulate multiple metals is critical for phytoremediation to be a viable remediation alternative. In addition to being able to hyperaccumulate multiple metals, the optimal plant must be fast growing with sufficient biomass to sequester the heavy metals.     

Polycyclic Aromatic Hydrocarbons, Polychlorinated Biphenyls and Trace Metals in Sediments from a Coastal Lagoon (Northern Adriatic, Italy)

Surface sediments (0–5 cm) were analysed to provide information on levels, spatial trends and sources of the 16 USEPA polycyclic aromatic hydrocarbons (PAH), 15 polychlorinated biphenyls (PCBs) and trace metals (copper, chromium, mercury, nickel and zinc) in channel and wetland habitats of Pialassa Baiona lagoon (Italy). The highest levels of PAHs, PCBs and Hg (3,032–87,150, n.d.–3,908 and 1.3–191 mg kg⁻¹) were mainly found at channel habitats close to industrial sources. Pyrogenic PAH inputs were significant, with a predominance of four-ring PAHs and combustion-related PAHs in both channel and wetland habitats. Among PCB congeners, chlorination class profiles show that penta- and hexachlorinated PCBs are the most prevalent homologues accounting for approximately 33% and 47% of the total PCB concentrations in channel sediments. Total toxicity equivalent factors (TEQs) of potentially carcinogenic PAHs varied from 348 to 7,879 μg kg⁻¹ and from 4.3 to 235 μg kg⁻¹ in channel and wetland sediments; calculated TEQs for dioxin-like PCB congeners at channel habitats ranged from n.d. to 86.7 μg kg⁻¹. Comparison of PAHs, PCBs and metal levels with Sediment Quality Guidelines suggests that more concern should be given to the southern area of the lagoon for potential risks of carcinogenic PAHs, dioxin-like PCBs and mercury.     

Effect of Flooding on Contamination of Agricultural Soils with Metals and PAHs: The Middle Vistula Gap Case Study

During the intensive flood in May–June 2010, the floodplains in Little Poland Vistula Gap, used mostly for agriculture, were waterlogged for a period of over 1 month. The aim of the study was to assess the effect of the flood on the level of contamination of the soils in this region. The analysis included basic physicochemical soil properties, contents of ten metals, and concentrations of 16 polycyclic aromatic hydrocarbons (PAHs). The studies cover two territories on opposite sites of the river Vistula (Wilkow and Janowiec) differing in their areas (70 and 4.6 km²) and time of water logging (30 and 10 days). Forty soil samples were collected from both areas immediately after the flood event from the upper (0–30 cm) soil layer together with four samples from the 30–60-cm depth layer. This was supplemented by eight samples from the flood-deposited sediment layer (thickness, 2 cm). The concentrations of identified metals (As, Ba, Cr, Sn, Zn, Cd, Co, Cu, Ni, Pb) at all the sampling points were below the Polish legal limits for the upper layer of soils for agriculture use. The same regarded the median contents of nine PAHs compounds specified in the Polish regulations. In both areas, the median contents of Σ16 PAHs (0.21–0.35 mg kg⁻¹), Zn (10.3–10.6 mg kg⁻¹), Pb (9.2–10.7 mg kg⁻¹), and Cd (0.03 mg kg⁻¹) were much below the mean concentrations of those contaminants in arable soils on the national and European levels. The results show that this severe flooding episode in “clean” agricultural area had no immediate negative impact on the soils as regards the basic physicochemical properties (organic matter content, acidity, nitrogen content) and did not result in excessive soil contamination.     

Plant Availability and Uptake of Lead, Zinc, and Cadmium in Soils Contaminated with Anti-corrosion Paint from Pylons in Comparison to Heavy Metal Contaminated Urban Soils

Red lead (Pb₃O₄) has been used extensively in the past as an anti-corrosion paint for the protection of steel constructions. Prominent examples being some of the 200,000 high-voltage pylons in Germany which have been treated with red lead anti-corrosion paints until about 1970. Through weathering and maintenance work, paint compounds and particles are deposited on the soils beneath these constructions. In the present study, six such “pylon soils” were investigated in order to characterize the plant availability and plant uptake of Pb, Cd, and Zn. For comparison, three urban soils with similar levels of heavy metal contamination were included. One phase extractions with 1 M NH₄NO₃, sequential extractions (seven steps), and extractions at different soil pH were used to evaluate the heavy metal binding forms in the soil and availability to plants. Greenhouse experiments were conducted to determine heavy metal uptake by Lolium multiflorum and Lactuca sativa var. crispa in untreated and limed red lead paint contaminated soils. Concentrations of Pb and Zn in the pylon soils were elevated with maximum values of 783 mg Pb kg⁻¹ and 635 Zn mg kg⁻¹ while the soil Cd content was similar to nearby reference soils. The pylon soils were characterized by exceptionally high proportions of NH₄NO₃-extractable Pb reaching up to 17% of total Pb. Even if the relatively low pH of the soils is considered (pH 4.3–4.9), this appears to be a specific feature of the red lead contamination since similarly contaminated urban soils have to be acidified to pH 2.5 to achieve a similarly high Pb extractability. The Pb content in L. multiflorum shoots reached maximum values of 73 mg kg⁻¹ after a cultivation time of 4 weeks in pylon soil. Lime amendment reduced the plant uptake of Pb and Zn significantly by up to 91%. But L. sativa var. crispa cultivated on soils limed to neutral pH still contained critical Pb concentrations (up to 0.6 mg kg⁻¹ fresh weight). Possible mechanisms for the exceptionally high plant availability of soil Pb derived from red lead paint are discussed.     

Nitrogen mineralization and CO2 and N2O emissions in a sandy soil amended with original or acidified pig slurries or with the relative fractions

The following six pig slurries obtained after acidification and/or solid/liquid separation were used in the research: original (S) and acidified (AS) pig slurry, nonacidified (LF) and acidified (ALF) pig slurry liquid fraction, and nonacidified (SF) and acidified (ASF) pig slurry solid fraction. Laboratory incubations were performed to assess the effect of the application of these slurries on N mineralization and CO₂ and N₂O emissions from a sandy soil. Acidification maintained higher NH₄ ⁺-N contents in soil particularly in the ALF-treated soil where NH₄ ⁺-N contents were two times higher than in LF-treated soil during the 55–171-day interval. At the end of the incubation (171 days), 32.9 and 24.2 mg N kg⁻¹ dry soil were mineralized in the ASF- and SF-treated soils, respectively, but no mineralization occurred in LF- and S-treated soils, although acidification decreased N immobilization in ALF- (−25.3 mg N kg⁻¹ soil) and AS- (−12.7 mg N kg⁻¹ soil) compared to LF- (−34.4 mg N kg⁻¹ soil) and S-treated (−18.6 mg N kg⁻¹ soil) soils, respectively. Most of the dissolved CO₂ was lost during the acidification process. More than 90% of the applied C in the LF-treated soil was lost during the incubation, indicating a high availability of the added organic compounds. Nitrous oxide emissions occurred only after day 12 and at a lower rate in soils treated with acidified than nonacidified slurries. However, during the first 61 days of incubation, 1,157 μg N kg⁻¹ soil was lost as N₂O in the AS-treated soil and only 937 in the S-treated soil.     

Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol

Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching, denitrification, and nitrous oxide (N₂O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content 55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral N addition, on N mineralization–immobilization and N₂O emission. Residues were added at the rate of 3 t C ha⁻¹ to soil with, and without, 150 kg urea N ha⁻¹. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of soil N. Amended soil had significantly (P < 0.05) lower NO₃⁻–N, which reached minimum values of 2.8 mg N kg⁻¹ for sugarcane (at day 28), 10.3 mg N kg⁻¹ for maize (day 7), and 5.9 mg N kg⁻¹ for sorghum (day 7), compared to 22.7 mg N kg⁻¹ for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased by 45 mg N kg⁻¹ in sugarcane, 34 mg kg⁻¹ in maize, 29 mg kg⁻¹ in sorghum, and 16 mg kg⁻¹ in cotton amended soil compared to soil + N fertilizer, although soil NO₃⁻–N increased by 7 mg kg⁻¹ in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum emissions of N₂O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the cumulative N₂O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N₂O emission was significantly and positively correlated with NO₃⁻–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO₂ in the first 3 and 5 days of incubation (r = 0.59, P < 0.05).     

A critical assessment of soil amendments (slaked lime/acidic fertilizer) for the phytomanagement of moderately contaminated shooting range soils

Purpose  

The effects of the addition of an acidic fertilizer solution and/or slaked lime (5.5 g Ca(OH)₂ kg⁻¹) on a slightly acidic shooting range soil (pH 6.1, % organic carbon 5.4) with moderate metal (e.g., 620 mg kg⁻¹ Pb) and metalloid (17 mg kg⁻¹ Sb) concentrations on metal and Sb solubility and plant accumulation were investigated.     

Responses of microbial community in rhizosphere soils when ryegrass was subjected to stress from PCBs

Purpose  

The purpose of the present study was to investigate the composition and structure of microbial communities in rhizosphere soils in response to the presence of Aroclor 1242 with low (8 mg kg⁻¹ soil) and high (16 mg kg⁻¹ soil) concentrations in the hope to provide more information on potential dissipation of polychlorinated biphenyls (PCBs) at contaminated sites.     

The impact of storm water runoff on a small urban stream

Background, aim, and scope  In urban areas, storm water runoff often transports various pollutants, some of which settle and form sediments. In order to have the comprehensive view of the ecological state of storm water runoff recipients, both water and sediments of the stream must be assessed. In the Baltic Sea Area, the Water Framework Directive & HELCOM Recommendations aim to prevent or minimise pollution caused by harmful substances arising from storm water runoff, in order to promote the ecological restoration of the Baltic Sea—one of the most vulnerable seas. The aim of the study was to investigate the toxicity of bottom sediments of a small storm water runoff recipient focusing on the potential impact of successive discharges of urban storm water. Some storm water runoff quality parameters and the toxicity of bottom sediments of recipients was studied in this research. Materials and methods  During 9 years, at four discharge points, minimum four grab samples per year at each discharge point were taken for chemical characterisation. General parameters (pH, SS, BOD₇, COD_Cr and TPH) in liquid phase samples were analysed according to standard methods. Annual limit values were taken from the Lithuanian EPA requirements for the management of storm water runoff with a focus on prevention and control of contamination. Eleven composite samples of stream bottom sediments, each consisting of ten sub-samples, were collected in 2006. Toxicity screening from sediments was performed using the plant Lepidium sativum according to modified I. Magone’s methodology (Magone I, Bioindication of phytotoxicity of transport emission. In: Kachalova O-L, Zinatne (eds) Bioindication of toxicity of transport emissions in the impact of highway emissions on natural environment. Riga, pp 108–116, 1989). The level of toxic impact of Lepidium sativum (compared to control) was assessed according to the modified method of Wang (Rev Environ Contam Toxicol 126:88–127, 1992). Results  The mean pH of urban storm water runoff does not vary much from neutral, but range values are quite different, from 4.0 up to 8.7. The highest concentration of SS reached 800 mg L⁻¹, TPH—2.4 mg L⁻¹, BOD₇—300 mg O₂ L⁻¹ and COD_Cr—1,400 mg L⁻¹. The SS was above the limit in 64% of total amount of grab samples, TPH—37%, BOD₇—41% and COD_Cr—55%. The toxicity analysis of the bottom sediments showed varying toxicity of bottom sediments along the stream. From nine analysed samples of bottom sediments, 30% had weak toxicity, 30% medium and 30% strong toxicity on the test organism plant L. sativum. There was one single sample with no toxic effects, so that the results showed that urban storm water has an unacceptable environmental impact on recipients. It was also indicated that storm water runoff discharge alone is not the potential source of toxicity of bottom sediments. The litter demonstrated a weak toxicity of bottom sediments as well. Discussion  Most local authorities do not consider storm water runoff discharges to be a matter of great concern because they believe that surface runoff arising from rainfall is still relatively clean. The study showed that the current method of monitoring storm water runoff quality by chemical analyses is not the best tool for environmental impact assessment and must be combined with toxicity tests of bottom sediments of recipients. Recommendations and perspectives  To avoid the environmental impact of storm water runoff more attention should be paid to the development and implementation of storm water runoff pollution prevention measures. The study implies that future research concerning the relationships between storm water runoff deposit characteristics and biological activities must be developed to evaluate the contamination potential of stream sediment deposits for local aquatic ecosystems. Further studies should be developed to characterise the activities of the microbial community of storm water runoff sediments, and to monitor bioremediation in situ.     

The Roles of Diethylenetriamine Pentaacetate (DTPA) and Ethylenediamine Disuccinate (EDDS) in Remediation of Selenium from Contaminated Soil by Brussels Sprouts (Brassica oleracea var. gemmifera)

The objective of this study was to investigate the effects of adding different rates of diethylenetriamine pentaacetate (DTPA) at different concentrations (0, 0.5, 1, and 5 mmol kg⁻¹) and ethylenediamine disuccinate (EDDS) at 0, 5, 7.5, and 10 mmol kg⁻¹ on the capacity of Brussels sprouts plants to take up Se from soils contaminated with 0, 5, 10, and 15 mg kg⁻¹ NaSeO₄, under a greenhouse conditions. Results indicated that the application of DTPA and EDDS to Se-contaminated soils significantly affect plant Se concentration, Se uptake, and dry matter yield of plants. Se concentration in the plant leaves, stems, and roots increased with increase in DTPA and EDDS application doses, but total Se uptake increased from 0 to 1.0 and 7.5 mmol kg⁻¹ DTPA and EDDS application doses, respectively, and decreased after those levels due to toxic Se concentration for plant. Most plant available fractions and the carbonate, metal oxide, and organic matter-bound fractions increased linearly with Se application. At all DTPA and EDDS application rates, the Se concentrations in the leaves were about two to three times higher than those in the roots and about three to four times higher than those in the stems. This study suggests that the above-ground organs like leaf and shoots of Brussels sprouts can effectively be used in the removal of Se from soils contaminated with Se. Under the conditions in this experiment, Brussels sprouts were capable of removing 0.9–1.8 mg Se pot⁻¹ when harvested at maturity without any chelating agent take into consideration one growing season per year. Based on the data of present experiment, it would be necessary to approximately 57–67 growing seasons without EDDS and EDTA to remove all total Se from polluted soil. Selenium removal can be further increased 12- to 20-fold with 7.5 mmol kg⁻¹ EDDS and 1.0 mmol kg⁻¹ DTPA application, respectively.     

河北板蓝根产地土壤-植物中镉铅汞砷含量特征及其污染评价

采用野外调查和室内分析相结合的方法,研究了河北省安国市和蔚县板蓝根产地土壤-植物中Cd、Pb、Hg、As含量特征及其在菘蓝中的累积特性,并对板蓝根产地土壤和草药中Cd、Pb、Hg、As污染状况进行了评价,为该地区安全、合理地发展中草药生产提供数据支撑和科学依据。结果表明,安国市和蔚县板蓝根产地土壤中重金属Cd、Pb、Hg、As含量差异不大,土壤重金属含量的变异系数在11.70%~97.65%。以《土壤环境质量标准》(GB 15618—1995)一级标准值进行评价,综合污染指数评价结果显示45%板蓝根种植区土壤Cd、Pb、Hg、As污染等级为警戒限,其他处于清洁水平;而以《土壤环境质量标准》二级标准值进行评价,种植区单项污染指数及综合污染指数结果均0.7,土壤环境清洁。此外,菘蓝地上部(大青叶)Cd、Pb、Hg、As平均含量分别为0.22 mg·kg~(-1)、0.89 mg·kg~(-1)、0.04 mg·kg~(-1)、0.25 mg·kg~(-1),对重金属的富集能力表现为CdHgPbAs;菘蓝地下部(板蓝根)Cd、Pb、Hg、As含量均值分别为0.14 mg·kg~(-1)、0.57 mg·kg~(-1)、0.04 mg·kg~(-1)、0.26 mg·kg~(-1),对重金属的富集能力表现为CdHgAsPb。所有菘蓝样品中Pb、Hg、As含量均未超出《药用植物及制剂进口绿色行业标准》(WM2—2001),大青叶9.09%样品中Cd超标,且Cd平均污染指数0.7,属警戒限污染等级。因此,在中药材GAP(良好的农业规范)产地环境质量评价时,除板蓝根产地土壤完全符合土壤环境质量二级标准外,也不应忽视板蓝根和大青叶吸收和累积重金属的自身特性。     

Zn and Pb release of sphalerite (ZnS)-bearing mine waste tailings

Background, aim, and scope  Contaminated mine drainage water has become a major hydrogeological and geochemical problem. Release of soluble metal contaminants and acidity from mining sites can pose serious chemical risks to surface and groundwater in the surrounding environment, and it is an important socio-economic factor addressed by working groups like SUITMA Morel and Heinrich (J Soils Sediments 8:206–207, 2008). The release of Zn and Pb from sulfide-bearing flotation residues of a small scale mine in Western Germany is investigated with focus on metal transfer to soil solution. Total contents of the soil material as well as soil water sampled with suction cups were analyzed. The influence of pH on leaching behavior was investigated with pH_stat tests. Isotopic analyses helped assessing seepage water velocity. The aim of this study was the assessment of the environmental behavior of zinc and lead caused by the weathering of sulfide-bearing mine tailings. Especially, we address in this paper the dissolution of sphalerite (ZnS) in contrast to the well-known dissolution processes of pyrite (FeS₂). Materials and methods  Total metal contents of the soil samples were analyzed by energy-dispersive X-ray fluorescence spectroscopy, total C concentration was measured using a CHNS elemental analyzer. X-ray diffraction (XRD) spectra were recorded from powdered soil samples. Soil water was sampled in nylon suction cups. Electrical conductivity (EC), pH, and temperature of the soil water samples were measured in the field immediately after sampling. Major anions (F, Cl, NO₂, NO₃, SO₄) were analyzed by ion chromatography, major cations (Ca, Na, K, Li) were analyzed by flame photometry, heavy metals (Zn, Pb, Fe, Mn, and Mg) by flame atomic absorption spectrometry. Tritium was analyzed by liquid scintillation counting (LSC), ¹⁸O and ²H were analyzed by isotope ratio mass spectrometry (IRMS). pH_stat tests were performed at four different pH values between 2 and 5. Results  Total Zn contents of the soil samples averaged 10 g kg⁻¹, Pb contents averaged 2.5 g kg⁻¹, Fe 22 g kg⁻¹, S 8.0 g kg⁻¹, and total carbon 4.0 g kg⁻¹. Below 2-m depth, soil samples had neutral pH values. Toward the surface, pH decreased down to pH 5.4 in P1 and P3, and to pH 5.9 in core P2, respectively. Dissolved contents of major ions (Mg, Ca, K, SO₄, and HCO₃) in the soil solution increased with depth. Metal concentrations (Fe, Mn, Zn) decreased with depth. The solution pH was neutral to slightly alkaline in samples below 2 m and slightly acidic (pH 6) at 1 m depth. Tritium values are around 7 TU and correspond to modern rain, i.e., after 1975. Stable isotope values plot on the global meteoric water line. The pH_stat tests provide two kinds of information, the acid neutralization capacity after 24 h (ANC24) and the release of metals depending on pH. The ANC24 increases linearly with decreasing pH from about 60 mmol(eq) kg⁻¹ at pH 5 to about 460 mmol(eq) kg⁻¹ at pH 2. Zn and Fe release show a strong increase with decreasing pH to 126 and 142 mmol(eq) kg⁻¹, respectively. Pb release increases at pH <4 and Mn release at pH <5, both to about 10 mmol(eq) kg⁻¹. Discussion  With an average of 10 g kg⁻¹, this field site is highly enriched in Zn. In the oxidized topsoil, Zn concentrations are significantly lower than in the anoxic subsoil. The distribution pattern of total Zn contents and soil pH values indicate that the topsoil, which is prone to oxidation and acidification, is already depleted in Zn. Only in soil core P2, Zn (and Fe) contents in the topsoil were higher than in the subsoil. Oxidation of the sulfidic material leads to redistribution into mobilizable species. High soil water concentrations (10 to 15 mg L⁻¹) can be found at acidic pH. The dominant Zn species in the soil solution is Zn²⁺. At neutral pH, Zn concentrations are below 0.001 mg L⁻¹. During the soil passage, the contaminated seepage water enters the anoxic subsoil with pH buffering carbonates. Results indicate that Zn is immobilized there. However, when the acid neutralization capacity is exhausted, a breakthrough of dissolved Zn to the groundwater has to be expected. Lead averages 2.5 g kg⁻¹ inside the flotation dump. In contrast to Zn, the first centimeters of the oxidized topsoil with high TOC contents show higher Pb contents than the anoxic subsoil. About 80% of the cation exchange capacity in the topsoil is occupied by Pb. In contrast to Zn, Pb is not abundant as aqueous species at slightly acidic pH. Values lower than pH 4 are necessary to mobilize Pb in higher amounts, as pH_stat experiments confirm. Hence, Pb is not expected to be leached out until the buffer capacity of the soil is exhausted. Conclusions  The environmental fate and behavior of Zn and Pb in the flotation dump is strongly depending on pH and redox conditions. Oxidation of sphalerite leads to a transfer of Zn from immobile to easily mobilizable species. Sulfide oxidation leads to an acidification of the topsoil where the buffer capacity is already exhausted due to the leaching of carbonates. At acidic pH, Zn is transferred to the aqueous phase and leached to the subsoil where soil pH is neutral. Electron supply and the buffer capacity of the material are found to be the main factors controlling the mobility of Zn. In contrast, the transfer of comparable amounts of Pb to the aqueous phase requires pH values <4. Since Pb is enriched in the topsoil, not leaching to the groundwater, but direct uptake (e.g., children, animals) and uptake by plants is the highest environmental risk. If the acidification of the soil proceeds with the same rate as in the last 40 years, it will reach the bottom of the tailing in about 200 years and a breakthrough of metals to the groundwater has to be expected. Recommendations and perspectives  The behavior of the different metals and their environmental impact depends on the different metal properties as well as on external conditions, e.g. pH, redox conditions, buffer capacity, and groundwater recharge. To assess the future release of metals from a flotation dump it is crucial to determine the main processes leading to acidification, the buffer capacity, and heavy metal binding forms. The release of heavy metals to the groundwater could be prevented by liming or other buffering techniques de Andrade et al. (J Soils Sediments 8:123–129, 2008). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Phytoremediation of Mixed Soil Contaminants

Tests were conducted to study the influence of non-ionic surfactants Triton X-100 and Tween 80 on the removal of mixed contaminants from a sandy soil using phytoremediation. Cd(II) and Pb(II) were used to form the inorganic contaminant, while used engine oil was selected to form the organic contaminant. The Indian mustard (Brassica juncea) plant was the plant chosen for phytoremediation of the sandy soil that contained the mixed contaminant. Thirty days after the plants were grown in the greenhouse, surfactants were applied to test pots in which the soil had been spiked with 50 mg kg⁻¹ of CdCl₂, 500 mg kg⁻¹ of PbCl₂ and 500 mg kg⁻¹ of used engine oil. Two control tests were conducted in this study. Planted and unplanted control tests were conducted using soil without surfactants. Following these tests, the tests were completed using the plants and surfactants at different concentrations. Test results showed that Triton X-100 and Tween 80 at concentrations higher than their critical micellar concentration enhanced Cd(II) and Pb(II) accumulation in the plant roots. Further, test data showed that translocation of contaminants to plant shoots occurred for Cd(II) but not for Pb(II). At the same concentrations, Tween 80 was more effective than Triton X-100 in facilitating rhizodegradation of used engine oil. This study demonstrates that simultaneous phytoremediation of Pb(II), Cd(II) and oil can be enhanced by using non-ionic surfactant Tween 80. Leaching test results indicated that the enhanced phytoremediation could remove the mixed contaminants safely from the point of view of limiting groundwater contamination.     

Cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis> Crantz) genetic resources: a case of high iron and zinc

Cassava hybrids from interspecific crosses with Manihot caerulescens Pohl, M. pseudoglaziovii Pax and Hoffmann and M. dichotoma Ule showed a very high iron and zinc content in both roots and leaves, e.g. 98.15 mg kg⁻¹ in roots of the interspecific hybrid cassava-M. caerulescens versus 12.17 mg kg⁻¹ in a cassava cultivar. This promising results show the potential of wild Manihot species for micronutrient enhancement of cassava.     

Salt-tolerant rhizobacteria-mediated induced tolerance in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) and chemical diversity in rhizosphere enhance plant growth

Salt-tolerant isolates Bacillus pumilus, Pseudomonas mendocina, Arthrobacter sp., Halomonas sp., and Nitrinicola lacisaponensis isolated from high saline habitats exhibited plant growth-promoting traits like P solubilization and indole acetic acid (IAA), siderophore, and ammonia production. These isolates were inoculated in wheat to assess microbe-mediated responses and plant growth promotion in salt affected soil. Maximum shoot and root length (33.8 and 13.6 cm) and shoot and root biomass (2.73 and 4.48 g dry weight) was recorded in plants inoculated with B. pumilus after 30 days. Total chlorophyll content was maximum in the leaves of the plants treated with Halomonas sp. (24.22 mg g⁻¹ dry weight) followed by B. pumilus (23.41 mg g⁻¹ dry weight) as compared to control (18.21 mg g⁻¹ dry weight) after 30 days. Total protein content was maximum in Arthrobacter sp. inoculated plant leaves (3.19 mg g⁻¹ dry weight) followed by B. pumilus (2.47 mg g⁻¹ dry weight) as compared to control (2.15 mg g⁻¹ dry weight) after 30 days. Total carotenoid content was maximum in plants inoculated with Halomonas sp. (1,075.45 and 1,113.29 μg g⁻¹ dry weight) in comparison to control (837.32 and 885.85 μg g⁻¹ dry weight) after 15 and 30 days. Inoculation of bacterial isolates increased presence of individual phenolics (gallic, caffeic, syringic, vanillic, ferulic, and cinnamic acids) and flavonoid quercetin in the rhizosphere soil. The concentration of IAA in rhizosphere soil and root exudates was also higher in all treatments than in control. Accumulation of phenolics and quercetin in the plants played a cumulative synergistic role that supported enhanced plant growth promotion of wheat in the stressed soil.     

Nitrate and Phosphate Leaching under Turfgrass Fertilized with a Squid-based Organic Fertilizer

Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic burden on processors. A potential solution to this problem involves converting squid by-products into an organic fertilizer, for which there is growing demand. Because fertilizer application to lawns can increase the risk of nutrient contamination of groundwater, we quantified leaching of NO₃–N and PO₄–P from perennial ryegrass turf (Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) and synthetic (SY). Field plots were established on an Enfield silt loam, and liquid (L) and granular (G) fertilizer formulations of squid and synthetic fertilizers were applied at 0, 48, 146, and 292 kg N ha⁻¹ year⁻¹. Levels of NO₃–N and PO₄–P in soil pore water from a depth of 60 cm were determined periodically during the growing season in 2008 and 2009. Pore water NO₃–N levels were not significantly different among fertilizer type or formulation within an application rate throughout the course of the study. The concentration of NO₃–N remained below the maximum contaminant level (MCL) of 10 mg L⁻¹ until midSeptember 2009, when values above the MCL were observed for SQG at all application rates, and for SYL at the high application rate. Annual mass losses of NO₃–N were below the estimated inputs (10 kg N ha⁻¹ year⁻¹) from atmospheric deposition except for the SQG and SYL treatments applied at 292 kg N ha⁻¹ year⁻¹, which had losses of 13.2 and 14.9 kg N ha⁻¹ year⁻¹, respectively. Pore water PO₄–P levels ranged from 0 to 1.5 mg P L⁻¹ and were not significantly different among fertilizer type or formulation within an application rate. Our results indicate that N and P losses from turf amended with squid-based fertilizer do not differ from those amended with synthetic fertilizers or unfertilized turf. Although organic in nature, squid-based fertilizer does not appear to be more—or less—environmentally benign than synthetic fertilizers.     

Reduced net atmospheric CH4 consumption is a sustained response to elevated CO2 in a temperate forest

We compared, from 2004 through 2006, rates of soil–atmosphere CH₄ exchange at permanently established sampling sites in a temperate forest exposed to ambient (control plots; ∼380 μL L⁻¹) or elevated (ambient + 200 μL L⁻¹) CO₂ since August 1996. A total of 880 observations showed net atmospheric CH₄ consumption (flux from the atmosphere to the soil) from all static chambers most of the time at rates varying from 0.02 mg m⁻² day⁻¹ to 4.5 mg m⁻² day⁻¹. However, we infrequently found net CH₄ production (flux from the soil to the atmosphere) at lower rates, 0.01 mg m⁻² day⁻¹ to 0.08 mg m⁻² day⁻¹. For the entire study, the mean (±SEM) rate of net CH₄ consumption in control plots was higher than the mean for CO₂-enriched plots, 0.55 (0.03) versus 0.51 (0.03) mg m⁻² day⁻¹. Annual rates of 184, 196, and 197 mg m⁻² for net CH₄ consumption at control plots during the three calendar years of this study were 19, 10, and 8% higher than comparable values for CO₂ enriched plots. Differences between treatments were significant in 2004 and 2005 and nearly significant in 2006. Volumetric soil water content was consistently higher at CO₂-enriched sites and a mixed-effects model identified a significant soil moisture x CO₂ interaction on net atmospheric CH₄ consumption. Increased soil moisture at CO₂-enriched sites likely increases diffusional resistance of surface soils and the frequency of anaerobic microsites supporting methanogenesis, resulting in reduced rates of net atmospheric CH₄ consumption. Our study extends our observations of reduced net atmospheric CH₄ consumption at CO₂-enriched plots to nearly five continuous years, suggesting that this is likely a sustained negative feedback to increasing atmospheric CO₂ at this site.     

Fixation and defixation of ammonium in soils: a review

Fixed NH₄⁺ (NH₄⁺ _f) and fixation and defixation of NH₄⁺ in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH₄⁺ _f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH₄⁺ _f does not necessarily reflect the fraction that is truly available to plants. The content of native NH₄⁺ _f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows that the NH₄⁺ _f-N content amounts to 10–90 mg kg⁻¹ in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg⁻¹ in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg⁻¹ in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH₄⁺ _f are mainly due to the fact that some investigators distinguished between native and recently fixed NH₄⁺ while others did not. Recently fixed NH₄⁺ is available to plants to a greater degree than the native NH₄⁺ _f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed NH₄⁺ suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH₄⁺ defixed during a growing season varied greatly within the groups of silty (20–200 kg NH₄⁺-N ha⁻¹ 30 cm⁻¹) as well as clayey (40–188 kg NH₄⁺-N ha⁻¹ 30 cm⁻¹) soils. The pool of recently fixed NH₄⁺ may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from soils.     

Fate of Macronutrients in Water Treatment of Digestate Using Vibrating Reversed Osmosis

In the transition from a fossil to a bio-based economy, it has become an important challenge to maximally recuperate and recycle valuable nutrients coming from manure and digestate processing. Membrane filtration is a suitable technology to separate valuable nutrients in easily transportable concentrates which could potentially be re-used as green fertilizers, in the meantime producing high quality water. However, traditional membrane filtration systems often suffer technical problems in waste stream treatment. The aim of this study was to evaluate the performance of vibratory shear enhanced processing (VSEP) in the removal of macronutrients (N, P, K, Na, Ca, Mg) from the liquid fraction of digestates, reducing their concentrations down to dischargeable/re-usable water. In addition, the re-use potential of VSEP-concentrates as sustainable substitutes for fossil-based mineral fertilizers was evaluated. Removal efficiencies for N and P by two VSEP filtration steps were high, though not sufficient to continuously reach the Flemish legislation criteria for discharge into surface waters (15 mg N l⁻¹ and 2 mg P l⁻¹). Additional purification can occur in a subsequent lagoon, yet further optimization of the VSEP filtration system is advised. Furthermore, concentrates produced by one membrane filtration step showed potential as N–K fertilizer with an economic value of €6.3 ± 1.1 t⁻¹ fresh weight (FW). Further research is, however, required to evaluate the impact on crop production and soil quality by application of these new potential green fertilizers.     

The Effectiveness and Feasibility of Using Ochre as a Soil Amendment to Sequester Dissolved Reactive Phosphorus in Runoff

Incidental losses of dissolved reactive phosphorus (DRP) to a surface waterbody originate from direct losses during land application of fertilizer, or where a rainfall event occurs immediately thereafter. Another source is the soil. One way of immobilising DRP in runoff before discharge to a surface waterbody, is to amend soil within the edge of field area with a high phosphorus (P) sequestration material. One such amendment is iron ochre, a by-product of acid mine drainage. Batch experiments utilising two grassland soils at two depths (topsoil and sub-soil), six ochre amendment rates (0, 0.15, 1.5, 7.5, 15 and 30 g kg⁻¹ mass per dry weight of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L⁻¹) were carried out. A proportional equation, which incorporated P sources and losses, was developed and used to form a statistical model. Back calculation identified optimal rates of ochre amendment to soil to ameliorate a specific DRP concentration in runoff. Ochre amendment of soils (with no further P inputs) was effective at decreasing DRP concentrations to acceptable levels. A rate of 30 g ochre kg⁻¹ soil was needed to decrease DRP concentrations to acceptable levels for P inputs of ≤10 mg L⁻¹, which represents the vast majority of cases in grassland runoff experiments. However, although very quick and sustained metal release above environmental limits occurred, which makes it unfeasible for use as a soil amendment to control P release to a waterbody, the methodology developed within this paper may be used to test the effectiveness and feasibility of other amendments.