Determination of nitrite with a nano-gold modified glassy carbon electrode by cyclic voltammetry

Abstract

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of rare earth elements (REEs) in plants and soils. Sample preparation and analytical conditions were investigated to set up a simple routine procedure for measuring rare earth elements. For prompt sample decomposition, a microwave digestion technique was successfully used with an acid mixture of HCl+HNO₃+HF. Detection limits, reproducibility, accuracy and possible interference were also studied. ICP-MS provided extremely low detection limits for REEs (0.6–6ng/l). Precision was typically better than 6% RSD (relative standard deviation) for soil and 10% for plant. The potential of the method was evaluated by analysis of standard reference materials of soils and plants. A good agreement between the experimental results and certified values was observed. The spectroscopic interference of Ba with Eu and light REEs(LREEs, La-Eu) with heavy REEs(HREEs, Gd-Lu) were eliminated by the algebra correction.

The results suggested that REEs in soil samples existed mainly as light REEs, and the same concentration distribution patterns of Oddo-Hakins law were observed, showing negative gradient from La to Lu concentrations. The REE contents in plants were very low, less than 20μg/g and varied with plant species. Apart from rape leaf(Brassica juncea), the REE distribution patterns in other plant leaves were consistent with soils, indicating that these plants generally absorbed REEs from soil without selectivity. Rape leaf showed selective absorption for LREEs, especially for La. The REE concentration distribution in parts of hot pepper(Capsicum annuum) was characteriaed by root>leaf>stem>fruit. The REEs absorbed by hot pepper concentrated mainly in roots and leaves, very little migrated into fruit. Transfer factors(TFs) of REEs in plants were very low. Although the contents of LREEs were relatively more than those of HREEs, no distinct difference of TFs between LREEs and HREEs was observed, meaning that LREEs and HREEs have the same abilities of transportation. However, for rape leaf, the TFs of LREEs were one or two orders of magnitude higher than those of HREEs.     

Multielement analysis by sequential instrumental and radiochemical neutron activation

We measured 37 elements in six USGS geological camples and one NBS biological orchard leaf (OL) sample, using sequential INAA and radiochemical group separation coupled with high resolution, high efficiency Ge(Li), and a Ge(Li) with anticoincidence shields. The elemental concentrations in these samples vary over three orders of magnitude. Our results agree very well with the reported values. The rare earth values in PCC-1 are 2–4 times lower than the reported values. Precise REE patterns are defined in USGS samples, which are characteristic of the total rock types. The REE pattern in OL is identical to the mineral apatite. In addition to the possibility that OL may be contaminated by local soil, it is also possible that the uptake of REE trace elements by plants from soil is perhaps dominated by accessory mineral such as apatite, or plants take up the REE from bulk soil in a preferential manner as a smooth function of the REE ionic radii.     

Study on the contents of trace rare earth elements and their distribution in wheat and rice samples by RNAA

The concentrations of 8 REE (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in wheat and rice samples have been determined by RNAA. The contents and distributions of REE in each part of the plants (i.e. root, leaf, stem, husk and seed) and their host soils were studied, which included samples applied with rare earch elements in farming and control samples. The effects of applying rare earths on the uptake of REE by the plants and the REE accumulation in the grains on human health were also discussed in this paper.     

Precise trace rare earth analysis by radiochemical neutron activation

A rare earth group separation scheme followed by normal Ge(Li), low energy photon detector (LEPD), and Ge(Li)−NaI(Tl) coincidence-noncoincidence spectrometry significantly enhances the detection sensitivity of individual rare earth elements (REE) at or below the ppb level. Based on the selected γ-ray energies, normal Ge(Li) counting is favored for¹⁴⁰La,¹⁷⁰Tb and¹⁶⁹Yb; LEPD is favored for low γ-ray energies of¹⁴⁷Nd,¹⁵³Sm,¹⁶⁶Ho and¹⁶⁹Yb; and noncoincidence counting is favored for¹⁴¹Ce,¹⁴³Ce,¹⁴²Pr,¹⁵³Sm,¹⁷¹Er and¹⁷⁵Yb. The detection of radionuclides^152mEu,¹⁵⁹Gd and¹⁷⁷Lu is equally sensitive by normal Ge(Li) and noncoincidence counting;¹⁵²Eu is equally sensitive by LEPD and normal Ge(Li); and¹⁵³Gd and¹⁷⁰Tm is equally favored by all the counting modes. Overall, noncoincidence counting is favored for most of the REE. Precise measurements of the REE were made in geological and biological standards. Prepared for the U.S. Department of Energy under Contract DE-AC06-76RLO 1830.     

Comparison of single and sequential extraction procedures for the study of rare earth elements remobilisation in different types of soils

With the continual increase in the utilisation of rare earth elements (REE) for industrial and agricultural purposes, research into the environmental and biogeochemical behaviour of REE had attracted much interest in recent times. This study principally describes the distribution of REE in four different types of soils like lateritic soil (S-1), in situ natural soil (S-2), soil contaminated by mining activity (S-3) and accidentally polluted soil (S-4) utilizing the optimised BCR sequential extraction procedure and partial extractions with various types of single extractants such as unbuffered salt solutions 0.1 M NaNO₃, 0.01 M CaCl₂, 1 M NH₄NO₃; complexing agents 0.005 M DTPA and 0.05 M EDTA; acid solutions 0.43 M CH₃COOH and 1 M HCl. Comparison of the sum of the four BCR fractions, which included an aqua regia attack on the residue, with the pseudo-total aqua regia digest values to assess the accuracy of the BCR partioning approach has been undertaken. Partial extraction results with several single extractants have also been reported for all the REE elements including yttrium which have been analysed by the optimised BCR procedure. Results obtained after 24 h extraction with each of the single extractant have also been discussed. The extraction with 1 M HCl during 24 h yielded similar quantities of REE as those released under the combined steps of 1, 2 and 3 of the BCR sequential extraction for all the four different type of soil samples indicating that this reagent can be used successfully to estimate the total extractable contents of REE in various types of soil samples.     

Biogeochemistry of trace and major elements in a surface environment (volcanic rock,soil, mosses,lichens) in the S. Miguel Island,Azores, Portugal

The distribution of the chemical element during weathering of trachyandesite in S. Miguel Island (Azores, Portugal), and in mosses and lichens growing on these rocks, was studied using instrumental neutron activation analysis. A general enrichment of rare earth elements (REEs), a Ce positive anomaly (partial oxidation after primary apatite dissolution) and a Eu negative anomaly (Eu²⁺ in plagioclases/clay minerals) are observed with increasing weathering. Mosses and lichens are Ce and Eu depleted, indicating that the main REE uptake is done via absorption from REE³⁺ secondary phosphates, probably together with P (essential nutrient). Zn, Br and Sb show higher enrichment factors in lichens and mosses.     

乌江流域沉积岩风化过程中稀土元素的富集与释放

以乌江流域石灰岩、白云质灰岩、白云岩、硅质岩、页岩和砂岩等沉积岩的13条风化剖面为对象，运用R型分层聚类分析和质量平衡计算方法，研究了这些岩石风化过程中稀土元素（REE）的富集与释放及其对植物生长和河水REE分布的影响，目的是为河水物质来源研究和为农业生产提供依据。结果表明：（1）乌江流域石灰土中REE的富集程度显著高于各自母岩、黄壤、上陆壳（UCC）、中国土壤（CS）和世界土壤（WS）；（2）沉积岩风化过程中REE的富集特征和机制可能与母岩中REE分布特征以及风化剖面中有机质、铁（氢）氧化物和粘土矿物的吸附有关；（3）沉积岩风化过程中释放的REE可为植物吸收利用；（4）石灰岩等沉积岩风化过程中REE和F。等元素的释放对河水溶解态REE的分布有重要影响。     

Determination of the contents and distribution characteristics of REE in natural plants by NAA

The concentration of 8 REEs (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in 17 species of plants and their host soil, which were collected from a rare earth ore area located in the south of China, have been determined by INAA. The chondritic normalized REE patterns for different parts of plants (e.g., leaf stem and root) and their host soils were studied. The results showed that the concentration levels of REE for most plants in the sampling area were elevated. Particularly, the leaves of the fern (Dicranopteris dichotoma) contain extremely high concentration of the total REE (675–3358 g/g) Generally, these REE distribution patterns in every part of plants were very similar and reflected the characteristics of their host soils. However, the chondritic normalized REE patterns in some plants relative to the host soil revealed obvious fractionation, such as the depletion of the heavy REE (for fernCitrus reticulata andBrassia campestris), the heavy REE enrichment (forCamellia sinensis, Camellia oleifera andZiziphus) and the Ce positive anomaly (forGardenia jasminoides).     

Determination and spatial distribution of <Superscript>137</Superscript>Cs in soils,mosses and lichens near Kavanayen,Venezuela

The activity of ¹³⁷Cs was determined in soils, mosses, lichens and other vegetation along the Caruay River and near the town of Kavanayen. The range of values for the soils was from <1.2 Bq·kg⁻¹ of ¹³⁷Cs (our detection limit) to 14.1 Bq·kg⁻¹. The range of ¹³⁷Cs activities in the mosses ranged from 9.9 to 17.9 Bq·kg⁻¹ with a mean value of 13.4±4 Bq·kg⁻¹; all the moss samples were found along the river. While the ¹³⁷Cs activities in the lichens ranged from 9.1 to 29.8 Bq·kg⁻¹; the two values along the river were about three factors higher than the one near Kavanayen. It was concluded that the ¹³⁷Cs activities in the soils, mosses and lichens are much higher along the river in respect to the nearby town of Kavanayen.     

Assessing the Capability of Chemical Ameliorants to Reduce the Bioavailability of Heavy Metals in Bulk Fly Ash Contaminated Soil

In-situ rehabilitation of fly ash at dumping sites has rarely been addressed for crop production due to growth-related constraints, largely of heavy metal (HM) contamination in soils and crops. Current communication deals with a novel approach to identify a suitable management option for rejuvenating the contaminated soils. In this background, a 60-days incubation experiment was conducted with different fly ash-soil mixtures (50 + 50%, A1; 75 + 25%, A2; 100 + 0%, A3) along with four ameliorants, namely, lime (T1), sodium sulphide (T2), di-ammonium phosphate (T3), and humic acid (T4) at 30 ± 2 °C to assess the ability of different fly ash-soil-ameliorant mixtures in reducing bio-availability of HMs. Diethylenetriaminepentaacetic acid (DTPA)-extractable bio-available HM contents for lead (Pb), cadmium (Cd), nickel (Ni), and chromium (Cr) and their respective ratios to total HM contents under the influence of different treatments were estimated at 0, 15, 30, 45, and 60 days of incubation. Further, the eco-toxicological impact of different treatments on soil microbial properties was studied after 60 days of experimentation. A1T1 significantly recorded the lowest bio-availability of HMs (~49–233% lower) followed by A2T1 (~35–133%) among the treatments. The principal component analysis also confirmed the superiority of A1T1 and A2T1 in this regard. Further, A1T1 achieved low contamination factor and ecological risk with substantial microbial biomass carbon load and dehydrogenase activity. Thus, liming to fly ash-soil mixture at 50:50 may be considered as the best management option for ameliorating metal toxicity. This technology may guide thermal power plants to provide the necessary package of practices for the stakeholders to revive their contaminated lands for better environmental sustainability.     

Rare earth element patterns in lake sediments as studied by neutron activation analysis

Using instrumental neutron activation analysis, the vertical distribution of La, Ce, Nd, Sm, Eu, Tb, Yb and Lu was determined in 3 well dated sedimentary cores collected from Laguna Mar Chiquita, Argentina. Validation of the methodology was done using the Soil 7 (IAEA) reference material. The REE contents vary according to core location and lithological units, depending on the proportion of fluvial terrigenous components in the lake sediments. Lithologies with higher proportion of terrigenous components show higher REE concentrations, suggesting that the dominant REE carrier phase might be a detrital mineral. There is a consistent value of about 1.2 for (La/Yb)_N and (LREE/HREE)_N ratios for all sediments at the three sites, indicating a slight LREE enrichment in relation to the average shale NASC. Ce/Ce* values are close to 1.0, meaning that Ce behaves similarly to other light REE's.     

Distribution characteristics of rare earth elements in plants from a rare earth ore area

The contents of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in various plant species taken from a rare earth ore area were determined by instrumental neutron activation analysis. For a given plant, the REE patterns in root, leaf and host soil are different from each other. The REE distribution characteristics in roots of various species are very similar and resemble those in the surface water. The results of this study suggest that there is no significant fractionation between the REEs during their uptake by the plant roots from soil solution. However, the variation of the relative abundance of individual REE occurs in the process of transportation and deposition of REEs in plants.     

Identifying chemical sources of airborne contamination in lichen biomonitors through instrumental neutron activation analysis

Chemical elements were determined in epiphytic lichens from Terceira and Santa Maria islands (Azores, Portugal), by k ₀-standardized, instrumental neutron activation analysis. Abundance ranges were generally below those in mainland Portugal, except for Br (Terceira), Cl (Santa Maria), Na (Santa Maria), and Se (both islands). Elemental (averaged) contents of As, Br, Cl, Co, Cr, Mg, Na, Se, Hg and Zn were significantly different between the islands. Anthropogenic influence was discernible in Terceira if not in Santa Maria, where only crustal and marine sources are apparent.     

Unusual interrelationship between care earth element and calcium contents in fern leaves

Since the rare earth elements (REE) are most informative as isomorphic replacements of Ca²⁺ in organisms, we analyzed these elements in 142 fern leaves collected from several sampling sites in Japan by instrumental neutron activation analysis (INAA), and the correlation between the REE and Ca contents was examined. In most cases, between any particular REE and the Ca contents, the correlation in the logarithmic scattering diagram was expressed as a single line parallel to the vertical (Y) axis. However, the detailed analysis of the diagrams characterized with respect to the sampling site revealed that the 142 ferns could be separated into two or three groups on the basis of their different REE/Ca ratios. The sampling sites where the different REE/Ca ratios were observed completely agreed with those found in the preceding report, i.e., regarding the unusual correlation between Eu and the other REEs. The present work was supported in part by a Grant-in-Aid from the Ministry of Education, Science, Sports and Culture, Japan.     

Non-destructive neutron activation analysis studies on a withering disease of lowland rice occurring near an iodine plant

The withering disease of lowland rice that seems to be an injury from exess iodine was recognized in the paddy fields near an iodine isolation plant. To investigate the cause of this disease a pot experiment of lowland rice was performed and iodine contents of soils and rice plants were determined by non-destructive neutron activation analysis. The soils of the disease-produced paddy fields were remarkably polluted by iodine, its contents in roots of diseased rice plants were more than the reported limiting values for the disease.     

Measurements of nitrogen isotope composition of plants and surface soils along the altitudinal transect of the eastern slope of Mount Gongga in southwest China

The natural abundances of stable nitrogen isotopes in plants and soils have been viewed as recorders that can be used to reconstruct paleoclimate and ecological processes or to indicate the biogeochemical cycle of nitrogen in nature. This study systematically measured the nitrogen isotope composition (δ¹⁵N) in plants and surface soils along an altitudinal transect of elevation range of 1200 to 4500 m on the eastern slope of Mount Gongga in southwest China. The influences of photosynthetic pathways on plant δ¹⁵N as well as the effects of temperature and precipitation on δ¹⁵N altitudinal trends in plants and surface soils are discussed. Across this altitude transect, the δ¹⁵N values of C₃ and C₄ plants on Mount Gongga range between ?9.87‰ and 7.58‰ with a mean value of ?1.33‰, and between ?3.98‰ and 4.38‰ with a mean value of ?0.25‰, respectively. There is an evident δ¹⁵N difference between C₃ plants and C₄ plants. If, however, you only compare C₄ plants with those C₃ plants growing at the same altitudinal range, no significant difference in δ¹⁵N exists between them, suggesting that photosynthetic pathway does not have an influence on the plant δ¹⁵N values. In addition, we found that C₃, C₄ plants and surface soil (0–5 cm depth) all trend significantly towards more negative δ¹⁵N with increasing elevation. Furthermore, this study shows that the mean annual temperature and the mean annual precipitation positively and negatively correlate with δ¹⁵N in C₃ and C₄ plants, respectively. This indicates that precipitation and temperature are the main controlling factors of the δ¹⁵N variation in plants with altitude. We propose that lower δ¹⁵N values of plants and soils at higher altitude should be attributed to lower mineralization and lower net nitrification rates induced by low temperature and abundant rainfall. Copyright © 2010 John Wiley & Sons, Ltd.     

Intrinsic Acid–Base Properties of a Hexa‐2′‐deoxynucleoside Pentaphosphate,d(ApGpGpCpCpT): Neighboring Effects and Isomeric Equilibria

The intrinsic acid‐base properties of the hexa‐2′‐deoxynucleoside pentaphosphate, d(ApGpGpCpCpT) [=(A1?G2?G3?C4?C5?T6)=(HNPP)^5?] have been determined by ¹H NMR shift experiments. The pK_a values of the individual sites of the adenosine (A), guanosine (G), cytidine (C), and thymidine (T) residues were measured in water under single‐strand conditions (i.e., 10 % D₂O, 47 °C, I=0.1 M , NaClO₄). These results quantify the release of H⁺ from the two (N7)H⁺ (G?G), the two (N3)H⁺ (C?C), and the (N1)H⁺ (A) units, as well as from the two (N1)H (G?G) and the (N3)H (T) sites. Based on measurements with 2′‐deoxynucleosides at 25 °C and 47 °C, they were transferred to pK_a values valid in water at 25 °C and I=0.1 M . Intramolecular stacks between the nucleobases A1 and G2 as well as most likely also between G2 and G3 are formed. For HNPP three pK_a clusters occur, that is those encompassing the pK_a values of 2.44, 2.97, and 3.71 of G2(N7)H⁺, G3(N7)H⁺, and A1(N1)H⁺, respectively, with overlapping buffer regions. The tautomer populations were estimated, giving for the release of a single proton from five‐fold protonated H₅(HNPP)^±, the tautomers (G2)N7, (G3)N7, and (A1)N1 with formation degrees of about 74, 22, and 4 %, respectively. Tautomer distributions reveal pathways for proton‐donating as well as for proton‐accepting reactions both being expected to be fast and to occur practically at no “cost”. The eight pK_a values for H₅(HNPP)^± are compared with data for nucleosides and nucleotides, revealing that the nucleoside residues are in part affected very differently by their neighbors. In addition, the intrinsic acidity constants for the RNA derivative r(A1?G2?G3? C4?C5?U6), where U=uridine, were calculated. Finally, the effect of metal ions on the pK_a values of nucleobase sites is briefly discussed because in this way deprotonation reactions can easily be shifted to the physiological pH range.     

Element content in a number of plant leaves and accumulation of some elements in typical plant species: A case of Okayama Prefecture

Content of 40 elements in plant leaves, soils and rocks collected from several sampling sites in Okayama Prefecture was analyzed by instrumental neutron activation analysis using the Research Reactor of Kyoto University. Of these, 16 elements were taken up, and the relationship among their amounts in plants, rocks and soils was discussed, focusing mainly on the essential elements of higher plants and related elements in the periodic table. Although most element contents in plant were different among species, the mediam values of the most non-essential elements in the leaf were lower than the contents in the soil and rock samples. However, essential elements showed significantly higher median values than those in the soil and rock samples. Most element contents in leaves showed a logarithmic normal distribution. The normal distribution was observed in most essential elements except for zinc, while non-essential elements did not show a normal distribution. The results obtained by analysis of variance, showed that the plant species studied could be divided into four major groups, namelyDicotyledoneae, Monocotyledoneae, Gymnospermae andPteridophyta. In general,Dycotyledoneae andPteridophyta had higher element contents thanMonocotyledonaeae andGymnospermae.     

Comparison and Evaluation of Extraction Media and Their Suitability in a Simple Model to Predict the Biological Relevance of Heavy Metal Concentrations in Contaminated Soils

Abstract

The concentrations of heavy metals in agricultural soils are increasing gradually from various diffuse sources. The metals can transfer from contaminated soils into the growing plants or may affect the respiration rate of soil microorganisms.

In the first part of this paper, the following simple model to predict the biorelevant metal concentration in anthropogenically or artificially contaminated soils is reported: log M_p = α + β log [M_NaNO3] log M_R = α' + β' log [M_NaNO3] log M_P = log Metal concentration in test plant (mg/kg dry weight) log M_R = log percent Redution in the respiration or enzyme activity [M_NaNO3] = Metal concentration in NaNO3-soil extract (mg/kg soil) α and β & α' + β' = Intercepts and slopes of the linear regression lines.

The model has been tested in laboratory experiments, in growth experiments either in a greenhouse or in the field. Also, an attempt is made to present a theoretical interpretation.

Critical concentrations are calculated with the help of the relationship between metal concentration in soil solution [M_NaNO3] and metal concentration in plants. The critical concentration, which is able to induce either phyto- or zootoxic concentrations in the plant parts (productive or vegetative) or reduce their growth or to reduce significantly the growth of soil microorganisms, are found to be uniform in a wide range of soils (pH 3 to 8 and CEC 10–50 millimol/100g soil), the critical concentrations of NaNO₃ in soil extracts are comparable with the values obtained with plant growth experiments in nutrient solution and also with the concentrations obtained from soil respiration experiments reported in literature.     

The concentration of rare earth elements in plants and in the adjacent soils

La, Ce, Nd, Sm, Eu, Tb, Yb and Lu were determined in needles of age class 5 from 6 individual Norway spruce trees and in their soils. Measurements were done by neutron activation analysis with a group separation of the REE. Concentrations in spruce needles are among the lowest values reported for plant leaves. Concentrations show small variations between the soils, but large variations between the trees. The mean ratio plant/soil is about 5·10^–3 forall REE except Ce. Needles have no Eu-anomaly and a strong negative Ce-anomaly with respect to the soil. In addition to the fractionation of the individual REE between trees and the soil, there is also a considerable fractionation between the trees.