Crop demand of manganese

The objectives of this study were to evaluate some of the popular rotation crops grown in Hungary for tolerance to low external Mn(2+) levels and to determine the critical tissue concentration of Mn(2+) deficiency during early stages of growth. The minimum Mn(2+) concentration required in soil nutrient contents was 42.5 mg kg(-1) for sunflower, 24.3 mg kg(-1) for tobacco and 10.2 mg kg(-1) for triticale. Sunflower, tobacco and triticale achieved optimum growth at 48.0-65.0 mg Mn(2+) kg(-1), 24.9-32.1 mg Mn( n+) kg(-1) and 28.7 to 29.6 mg Mn(2+) kg(-1), respectively. Critical shoot Mn(2+) concentration at early stages of growth was 53.6 mg kg(-1) in sunflower, 458.0 mg kg(-1) in tobacco and 193.8 mg kg(-1) in triticale. Our results demonstrate that the tolerance to low external Mn(2+) (triticale: <30.2 mg kg(-1); sunflower: <56.2 mg kg(-1); tobacco: <69.3 mg kg(-1)) and the critical tissue Mn(2+) levels for deficiency varied significantly between crop species tested.     

Dynamic changes in radial oxygen loss and iron plaque formation and their effects on Cd and As accumulation in rice (Oryza sativa L.)

Temporal variations and correlations between radial oxygen loss (ROL), iron (Fe) plaque formation, cadmium (Cd) and arsenic (As) accumulation were investigated in two rice cultivars at four different growth stages based upon soil pot and deoxygenated solution experiments. The results showed that there were significant differences in ROL (1.1–16 μmol O₂ plant^?1 h^?1), Fe plaque formation (4,097–36,056 mg kg^?1), Cd and As in root tissues (Cd 77–162 mg kg^?1; As 49–199 mg kg^?1) and Fe plaque (Cd 0.4–24 mg kg^?1; As 185–1,396 mg kg^?1) between these growth stages. ROL and Fe plaque increased dramatically from tillering to ear emergence stages and then were much reduced at the grain-filling stage. Furthermore, significantly positive correlations were detected between ROL and concentrations of Fe, Cd and As in Fe plaque. Our study indicates that increased Fe plaque forms on rice roots at the ear emergence stage due to the increased ROL. This stage could therefore be an important period to limit the transfer and distribution of Cd and As in rice plants when growing in soils contaminated with these toxic elements.     

Assessment of heavy metals in a soil contaminated by oil spill: a case study in Nigeria

Surface and subsurface soil samples contaminated with crude oils were collected from an impacted site at Bodo City in the Niger Delta, Nigeria, after a field reconnaissance survey. An uncontaminated soil sample collected 100 m from the impacted site, but within the same geographical area, was used as a control. Trace elements such as, As, Cu, Cr, Cd, Fe, Pb, Ba, Ni, V, Hg and cation-exchange capacity constituents of the contaminated and uncontaminated soils were determined by atomic absorption spectroscopy. Trace element concentrations were: Cu, 0.5–13.4 mg kg^{? 1}; Cr, 0.2–0.8 mg kg^{? 1}; Fe, 6.2–8.7 mg kg^{? 1}; Ba 80.0–108.0 mg kg^{? 1}; Ni, 0.6–4.8 mg kg^{? 1}; and V, 4.0–9.4 mg kg^{? 1}; cation-exchange capacity ranged from 43.6 to 57.2 mg kg^{? 1} in surface and subsurface soils. Results showed that eigenvalues for the two first principal components represent up to 49% of the total variance. A positive correlation of the first principal component with Cu, Cr and cation-exchange capacity shows pollution from oil spillage, while a positive correlation of the second principal component with Cr, Fe, V, and dissolved oxygen (DO) shows both oil pollution and allochthonous inputs.     

Arsenic speciation in polychaetes (Annelida) and sediments from the intertidal mudflat of Sundarban mangrove wetland, India

This paper documents the concentration of total arsenic and individual arsenic species in four soft-bottom benthic polychaetes (Perenereis cultifera, Ganganereis sootai, Lumbrinereis notocirrata and Dendronereis arborifera) along with host sediments from Sundarban mangrove wetland, India. An additional six sites were considered exclusively for surface sediments for this purpose. Polychaetes were collected along with the host sediments and measured for their total arsenic content using inductively coupled plasma mass spectrometry. Arsenic concentrations in polychaete body tissues varied greatly, suggesting species-specific characteristics and inherent peculiarities in arsenic metabolism. Arsenic was generally present in polychaetes as arsenate (As^V ranges from 0.16 to 0.50 mg kg^?1) or arsenite (As^III ranges from 0.10 to 0.41 mg kg^?1) (30–53 % as inorganic As) and dimethylarsinic acid (DMA^V <1–25 %). Arsenobetaine (AB < 16 %), and PO₄-arsenoriboside (8–48 %) were also detected as minor constituents, whilst monomethylarsonic acid (MA^V) was not detected in any of the polychaetes. The highest total As (14.7 mg kg^?1 dry wt) was observed in the polychaete D. arborifera collected from the vicinity of a sewage outfall in which the majority of As was present as an uncharacterised compound (10.3 mg kg^?1 dry wt) eluted prior to AB. Host sediments ranged from 2.5 to 10.4 mg kg^?1 of total As. This work supports the importance of speciation analysis of As, because of the ubiquitous occurrence of this metalloid in the environment, and its variable toxicity depending on chemical form. It is also the first work to report the composition of As species in polychaetes from the Indian Sundarban wetlands.     

Selenium speciation in wheat grain varies in the presence of nitrogen and sulphur fertilisers

This study investigated whether selenium species in wheat grains could be altered by exposure to different combinations of nitrogen (N) and sulphur (S) fertilisers in an agronomic biofortification experiment. Four Australian wheat cultivars (Mace, Janz, Emu Rock and Magenta) were grown in a glasshouse experiment and exposed to 3 mg Se kg^?1 soil as selenate (Se^VI). Plants were also exposed to 60 mg N kg^?1 soil as urea and 20 mg S kg^?1 soil as gypsum in a factorial design (N + S + Se; N + Se; S + Se; Se only). Plants were grown to maturity with grain analysed for total Se concentrations via ICP-MS and Se species determined via HPLC-ICP-MS. Grain Se concentrations ranged from 22 to 70 µg Se g^?1 grain (dry mass). Selenomethionine (SeMet), Se-methylselenocystine (MeSeCys), selenohomolanthionine (SeHLan), plus a large concentration of uncharacterised Se species were found in the extracts from grains. SeMet was the major Se species identified accounting for between 9 and 24 µg Se g^?1 grain. Exposure to different N and S fertiliser combinations altered the SeMet content of Mace, Janz and Emu Rock grain, but not that of Magenta. MeSeCys and SeHLan were found in far lower concentrations (<4 µg Se g^?1 grain). A large component of the total grain Se was uncharacterisable (>30 % of total grain Se) in all samples. When N fertiliser was applied (with or without S), the proportion of uncharacterisable Se increased between 60 and 70 % of the total grain Se. The data presented here indicate that it is possible to alter the content of individual Se species in wheat grains via biofortification combined with manipulation of N and S fertiliser regimes. This has potential significance in alleviating or combating both Se deficiency and Se toxicity effects in humans.     

Assessment of heavy metals contamination in soils surrounding a gold mine: comparison of two digestion methods

This study investigated two digestion methods (USEPA 3051: microwave, HNO₃ or Hossner: hot plate, HF–H₂SO₄–HClO₄) for heavy metals analysis in contaminated soil surrounding Mahad AD'Dahab mine, Saudi Arabia. Moreover, contamination metal levels were estimated. The Hossner and USEPA 3051 methods showed, respectively, average total contents of 17.2 and 18.1 mg kg^?1 for Cd, 11.6 and 10.6 mg kg^?1 for Co, 45.7 and 34.7 mg kg^?1 for Cr, 1030 and 1100 mg kg^?1 for Cu, 33,300 and 27,400 mg kg^?1 for Fe, 963 and 872 mg kg^?1 for Mn, 33.2 and 22.8 mg kg^?1 for Ni, 791 and 782 mg kg^?1for Pb, and 6320 and 2870 mg kg^?1 for Zn. A lack of significant differences and a high correlation coefficient (>90%) for Cd, Pb and Cu between the two digestion methods suggest that the total-recoverable method (USEPA 3051) may be equivalent to the total-total digestion method (Hossner) for determining these metals in the studied soil. However, significantly higher concentrations of Cr, Fe, Ni and Zn were found by the Hossner method comapred with the USEPA 3051 method. The soil samples have very or extremely high levels of Zn, Cu, Cd and Pb contamination, indicating very high potential ecological risk.     

An arsenic-contaminated field trial to assess the uptake and translocation of arsenic by genotypes of rice

Compared to other cereals, rice has particular strong As accumulation. Therefore, it is very important to understand As uptake and translocation among different genotypes. A field study in Chenzhou city, Hunan province of China, was employed to evaluate the effect of arsenic-contaminated soil on uptake and distribution in 34 genotypes of rice (including unpolished rice, husk, shoot, and root). The soil As concentrations ranged from 52.49 to 83.86 mg kg^?1, with mean As concentration 64.44 mg kg^?1. The mean As concentrations in rice plant tissues were different among the 34 rice genotypes. The highest As concentrations were accumulated in rice root (196.27–385.98 mg kg^?1 dry weight), while the lowest was in unpolished rice (0.31–0.52 mg kg^?1 dry weight). The distribution of As in rice tissue and paddy soil are as follows root ? soil > shoot > husk > unpolished rice. The ranges of concentrations of inorganic As in all of unpolished rice were from 0.26 to 0.52 mg kg^?1 dry weight. In particular, the percentage of inorganic As in the total As was more than 67 %, indicating that the inorganic As was the predominant species in unpolished rice. The daily dietary intakes of inorganic As in unpolished rice ranged from 0.10 to 0.21 mg for an adult, and from 0.075 to 0.15 mg for a child. Comparison with tolerable daily intakes established by FAO/WHO, inorganic As in most of unpolished rice samples exceeded the recommended intake values. The 34 genotypes of rice were classified into four clusters using a criteria value of rescaled distance between 5 and 10. Among the 34 genotypes, the genotypes II you 416 (II416) with the lowest enrichment of As and the lowest daily dietary intakes of inorganic As could be selected as the main cultivar in As-contaminated field.     

砷胁迫对不同烟草品种光合色素和叶绿素荧光特性的影响

为了研究不同浓度砷(As)对烟草光合色素和叶绿素荧光特性的影响,首先将3个烟草品种翠碧1号、K326和云烟-87幼苗种植在从0到100 mg·kg-1亚砷酸钠(Na As O2)的6个浓度组中进行盆栽试验,并定期进行烟草受害症状的观测,测定叶片的光合色素含量、叶绿素荧光参数。结果表明:烟草在As胁迫下的反应因As胁迫浓度、胁迫时间和烟草品种而异。烟草光合色素含量、叶绿素荧光参数均表现为低浓度下有促进效应和高浓度下有抑制效应,同时3种烟草在40 mg·kg-1As浓度处理下出现生长受阻,且浓度越高胁迫症状越明显。K326和云烟-87表观症状较明显,对As毒害的敏感性高于翠碧1号。随着As胁迫时间的延长,烟草的耐性增强,对As胁迫的敏感性减弱。     

Growth and Cd accumulation of two halophytes and a non-halophyte grown in a non-saline and a saline soil with different Cd levels

Two halophytes, Salicornia europaea and Atriplex verucifera, and the non-halophyte Chenopodium album were grown in pots on sodic and non-sodic Iranian soils spiked with up to 100 mg Cd kg^?1. The halophytes grew best on the sodic soil in the absence of Cd spiking, while C. album performed better on non-sodic soil. Cadmium spiking reduced the growth of all plants, with Cd tolerance decreasing in the order S. europaea>A. verucifera>C. album. The observed order of Cd tolerance corresponds to the abilities of the plants to tolerate sodic soil properties. The variation of Cd concentration in shoots in response to sodicity was related to different mechanism, including dilution (C. album) Cd solubilisation by Ca²⁺ (S. europea) and Ca²⁺ competition for uptake and translocation of Cd (A. verucifera). Improved understanding of these complex interactions will help to design phytoextraction technology for Cd-polluted soils in arid regions.     

Impact of organic manure on the phytoremediation potential of Vetiveria zizanioides in chromium-contaminated soil

Chromium is a pollutant present in electroplating waste water and its removal is necessary for the protection of the environment. Vetiveria zizanioides (VZ) was grown in chromium effluent concentrations of 50, 100 and 200 mg kg ^?1 soil amended with organic manure and the potential for phytoremediation was determined. The amounts of Cr in plant tissues (root and shoot), soil and percentage electrolyte leakage of VZ roots were analysed. From the results, VZ amended with organic manure showed the greatest potential for Cr removal because of its faster growth and larger biomass achieved over the whole length of the experiment. In this study, 92.25% Cr removal efficiency was obtained with a Cr concentration of 50 mg kg ^?1 soil and removal efficiencies of 90.5% and 85% were obtained with 100 and 200 mg kg^?1, respectively after a period of two months of VZ growth.     

Mine tailings composition in a historic site: implications for ecological restoration

Ecological restoration, using tolerant plant species and nutrient additions, is a low-cost option to decrease environmental risks associated with mine tailings. An attempt was previously made to establish such a vegetation cover on an abandoned tailings facility in Southern Ireland. Historically, the tailings site has been prone to dusting and is a potential source of contamination to the surrounding environment. The site was examined to determine the success of the previous restoration plan used to revegetate the site and to determine its suitability for further restoration. Three distinct floristic areas were identified (grassland, poor grassland and bare area) based on herbage compositions and elemental analysis. Surface and subsurface samples were taken to characterise tailings from within these areas of the tailings site. The pH of bare surface tailings (pH, 2.7) was significantly more acidic (p < 0.5) than in other areas. Additionally, negligible net neutralising potential resulted in the tailings being hostile to plant growth. Total metal concentrations in tailings were high (c. 10,000 mg kg^?1 for Pb and up to 20,000 mg kg^?1 for Zn). DTPA-extractable Zn and Pb were 16 and 11 % of the total amount, respectively. Metal content in grasses growing on some areas of the tailings were elevated and demonstrated the inability of the tailings to support sustainable plant growth. Due to the inherently hostile characteristics of these areas, future restoration work will employ capping with a barrier layer.     

Attenuation of metal species in acidic solutions using bentonite clay: implications for acid mine drainage remediation

A laboratory batch experimental study has been carried out to evaluate the adsorption capacity of selected metal species in acid mine drainage (AMD) by bentonite clay. Bentonite clay was mixed with simulated AMD at specific solid–liquid (S/L) ratios and agitated in a reciprocating shaker and adsorption of selected toxic metals assessed over time. Cation exchange capacity varied from 1140 to 1290 meq kg^?1. Contact of AMD with bentonite leads to increase in pH and a possible reduction in electrical conductivity and total dissolved solids. At constant agitation time of 60 min, the pH increased with dosage of bentonite. Removal of Mn²⁺, Al ³⁺, and Fe³⁺ was observed to be greatest at 60 min of agitation. Bentonite clay exhibits high adsorption for Al³⁺ and Fe³⁺ at concentration less than 300 mg L^?1, while the capacity for Mn²⁺ was observed to be lower. Adsorption capacity for SO₄^2? was low with a great percentage of the SO₄^2? remaining in solution. Adsorption capacity of bentonite with more complex formulated AMD and gold tailing leachates was low for Fe³⁺, Al³⁺, and Mn²⁺. This indicates that optimum adsorption of bentonite clay is dependent on the chemistry of the AMD and its application might be site specific.     

Purification of contaminated paddy fields by clean water irrigation over two decades

Paddy fields near a mining site in north part of Guangdong Province, PR China, were severely contaminated by heavy metals as a result of wastewater irrigation from the tailing pond. The following clean water irrigation for 2 decades produced marked rinsing effect, especially on Pb and Zn. Paddy fields continuously irrigated with wastewater ever since mining started (50 years) had 1,050.0 mg kg^?1 of Pb and 810.3 mg kg^?1 of Zn for upper 20 cm soil, in comparison with 215.9 mg kg^?1 of Pb and 525.4 mg kg^?1 of Zn, respectively, with clean water irrigation for 20 years. Rinsing effect mainly occurred to a depth of upper 40 cm, of which the soil contained highest metals. Copper and Cd in the farmlands were also reduced due to clean water irrigation. Higher availability of Pb might partly account for more Pb transferred from the tailing pond to the farmland and also more Pb removal from the farmland as a result of clean water irrigation. Neither rice in the paddy field nor dense weeds in the uncultivated field largely took up the metals. However, they might contribute to activate metals differently, leading to a different purification extent. Rotation of rice and weed reduced metal retention in the farmland soil, in comparison with sole rice growth. Harvesting of rice grain (and partially rice stalk) only contributed small fraction of total amount of removed metal. In summary, heavy metal in paddy field resulted from irrigation of mining wastewater could be largely removed by clean water irrigation for sufficient time.     

Hypoxia-driven selective degradation of cellular proteins in jumbo squids during diel migration to the oxygen minimum zones

The jumbo squid, Dosidicus gigas, is an oceanic top predator in the eastern tropical Pacific that undergoes diel vertical migrations into mesopelagic oxygen minimum zones (OMZs). Besides glycogen breakdown, the pathways of the squid’s metabolic (suppression) strategy are poorly understood. Here, juvenile D. gigas were exposed to oxygen levels found in the OMZ off Gulf of California (1 % O₂, 1 kPa at 10 °C) with the aim to identify, via proteomic tools, eventual anaerobic protein degradation as potential energy source at such depths. Under hypoxia, total protein concentration decreased nonsignificantly from 79.2 ± 12.4 mg g^?1 wet mass to 74.7 ± 11.7 mg g^?1 wet mass (p > 0.05). Yet, there was a significant decrease in heat-shock protein (Hsp) 90 and α-actinin contents (p < 0.05). The lower α-actinin concentration at late hypoxia was probably related to decreased protection of the Hsp90 chaperon machinery resulting in increased ubiquitination (p < 0.05) and subsequent degradation. Thus, the present findings indicate that D. gigas might degrade, at least under progressing hypoxia, specific mantle proteins anaerobically to increase/maintain anaerobic ATP production and extend hypoxia exposure time. Moreover, the ubiquitin–proteasome system seems to play an important role in hypoxia tolerance, but further investigations are necessary to discover its full potential and pathways.     

Assessment of elemental distribution and heavy metals contamination in phosphate deposits: potential health risk assessment of finer-grained size fraction

The concentrations and chemical distributions of heavy metals (Cd, Cr, Ni, Zn, U, and V) in the Al-Jiza phosphate ores were investigated. Typically, the mean concentration values of Cd, Cr, Ni, U, and Zn are 15 ± 8, 109 ± 21, 34 ± 6, 211 ± 55, 142 ± 55, and 161 ± 57 mg kg^?1, respectively. On the other hand, the encountered average concentration values of Cd, Cr, Ni, Zn, U, and V in the phosphate dust particles (<0.053) were found to be 22 ± 5, 179 ± 5, 67 ± 11, 441 ± 14, 225 ± 58, and 311 ± 9 mg kg^?1, respectively. The contamination factors of U and Cr are greater than 1, indicating that these heavy metals could be potentially hazardous, if released to the environment. Multivariate statistical analysis allowed the identification of three main factors controlling the distribution of these heavy metals and the other chemical constituents. The extracted factors are as follows: francolite mineral factor, clay minerals factor, and diagenesis factor. Health risk assessments of non-cancerous effects in finer-grained size fraction that might be caused by contamination with the heavy elements have been calculated for both children and adults. The risk assessments in case of children for non-cancerous effects showed that U has values greater than the safe level of hazard index (HI = 1). In case of adults, the value of risk for U is also higher as compared to those of Cd, Ni, Cr, and Zn where it lies within the safe range of hazard index (HI < 1). Child health risk assessment indicates that children are more vulnerable to contaminants from phosphate mining than adults.     

Isolation and characterisation of cadmium-resistant bacteria from an industrially polluted coastal ecosystem on the southeast coast of India

A total of 35 bacterial strains were isolated from the industrially polluted Cuddalore coast, on the southeast coast of India. Of these, 17 strains were cadmium resistant and the remainder were sensitive. Six strains (C-1, C-8, C-10, C-12, C-14 and N-1) were selected based on high levels of cadmium tolerance (>150 mg L^?1) and were termed highly cadmium-resistant bacteria (HCRB). These HCRB were identified on the basis of morphological, biochemical and partial sequencing of their 16S rRNA genes. The antibiotic-susceptibility patterns and minimum inhibitory concentrations (MIC) of different metals (Cu²⁺, Pb²⁺ and Zn²⁺) against each HCRB were determined. Among the isolates, C-14 showed high degrees of metal and antibiotic resistance compared with other HCRB. Growth rates of HCRB at two different Cd²⁺ concentrations (50 and 100 mg L^?1) and under different metal conditions (Cd²⁺, Cu²⁺ and Pb²⁺) were also investigated. HCRB growth rates were lower in the metal-treated condition than in the untreated condition. Isolates C-14 and N-1 removed>80% of Cd²⁺ from cadmium-treated broth. However, isolate C-14 removed 92.3% of Cd²⁺ compared with 86.5% for isolate N-1. Bacteria showing residual growth rates under metal stress conditions might be useful in metal removal applications under growing conditions.     

The influence of solid matrices on arsenic toxicity to Corophium orientale

In marine ecosystems, benthic organisms are really important because they are the first step in the transfer of contaminants from environment to biota. To this end, this study focused on biological assays with the amphipod Corophium orientale exposed to two different molecules of arsenic: arsenate (As^V), the most abundant form in sediments, and dimethyl-arsinate (DMA), expected to be moderately toxic as an intermediate in the process of detoxification. The toxicity of arsenic compounds was measured after exposure to three different matrices: water, spiked natural sediment and inert spiked quartz sand. LC₅₀ values were calculated for each exposure, and the results confirmed the highest toxicity of As^V, in addition to underlining the importance of matrix of exposure. Water exposure was the matrix which presented the highest toxicity for inorganic arsenic (As^V LC₅₀=3.51 mg L^?1 vs DMA LC₅₀=54.65 mg L^?1), spiked natural sediment demonstrated its capability to chelate arsenate toxicity (As^V LC₅₀=34.27 mg kg^?1 vs. DMA LC₅₀=52.19 mg kg^?1) and spiked quartz sand presented intermediate values for As^V (LC₅₀=25.26 mg kg^?1), whereas for DMA a lower toxicity was registered (LC₅₀=872.35 mg kg^?1). This study can provide some useful data linked with chemical speciation of arsenic and exposure matrix, for improving the correct management of contaminated sediment.     

Spatial distribution of copper in relation to recreational boating in a California shallow-water basin

The overall effect of the number of boats on the copper (Cu) levels in the water column and sediment, along with their spatial variability within Shelter Island Yacht Basin (SIYB), San Diego Bay, California was examined. We identified a horizontal gradient of increasing dissolved Cu and Cu in sediment from outside to the head of SIYB which was coincident with the increasing number of boats. Spatial models of Cu distribution in water and sediment indicated the presence of ‘hotspots’ of Cu concentration. From outside to the head of SIYB, dissolved Cu ranged from 1.3 μ g L^?1 to 14.6 μ g L^?1 in surface water, and 2.0 μ g L^?1 to 10.2 μ g L^?1 in bottom water. Cu in sediment exceeded the Effect Range Low of 34 mg kg^?1 (i.e. where adverse effects to fauna may occur), with a peak concentration of 442 mg kg^?1 at the head of the basin. Free Cu⁺⁺ in surface water was several orders of magnitude higher than in sediment porewater. High-resolution data of Cu species together with probability maps presented in this paper will allow managers to easily visualise and localise areas of impaired quality and to prioritise which areas should be targeted to improve Cu-related conditions.