Mercury and Methylmercury in Freshwater Fish and Sediments in South Korea Using Newly Adopted Purge and Trap GC-MS Detection Method

The use of purge and trap gas chromatography–mass spectrometry (GC-MS) technique for the determination of methylmercury in biological and sediment samples was described. The GC-MS detection system was combined with the dithizone extraction method for biological samples and the distillation method for sediment samples to alleviate matrix interference problems. The method was validated by analysis of CRMs such as SRM 966 (human blood), BCR 463 (tuna fish), IAEA 407 (fish), ERM CC580 (estuarine sediment), and IAEA 405 (sediment). The performance of the purge and trap GC-MS method was also tested on field samples of freshwater fish and sediment. The results were compared with those of the GC-ECD and the GC-CVAFS, which were used widely for methylmercury analysis. Additionally, total mercury and methylmercury levels in freshwater fish and sediments from various reservoirs and streams in Korea were measured to understand mercury contamination status in Korean peninsula. Methylmercury concentrations in freshwater fish were found to correlate with body weight, diet habit, and food availability. In sediment, total mercury concentrations correlated with methylmercury concentrations and organic matter such as %C and %S. However, no significant relationships between methylmercury and sediment organic matter have been found.     

An appraisal of microwave-assisted Tessier and BCR sequential extraction methods for the analysis of metals in sediments and soils

Purpose  

The purpose of this research was to assess the precision and accuracy of a BCR and Tessier microwave-assisted sequential extraction procedure, in comparison to the conventional versions for a range of metals using a soil, lake and estuarine certified reference material (CRM).     

SPME-GC-pyrolysis-AFS determination of methylmercury in marine fish products by alkaline sample preparation and aqueous phase phenylation derivatization

Characterization of a cost-efficient analytical method based on alkaline sample digestion with KOH and NaOH, followed by aqueous phase phenylation derivatization with NaBPh4 and solid phase microextraction (SPME) for the determination of methylmercury in typical fish-containing food samples commercially available in Hungary, is reported. The sample preparation procedure along with the applied SPME-GC-pyrolysis-AFS system was validated by measuring certified reference materials (CRM) BCR-464, TORT-2, and a candidate CRM BCR 710. To carry out an estimation of average Hungarian methylmercury exposures via marine fish and/or fish-containing food consumption, 16 commercially available products and 3 pooled representative seafood samples of-according to a previous European survey--the three most consumed fish species in Hungary, herring, sardines, and hake, were analyzed. Methylmercury concentrations of the analyzed samples were in the range 0.016-0.137 microg of MeHg g(-1) dry weight as Hg.     

Immobilization of Mercury Species under the Influence of Typical Organic Compounds in Waste Gases by the Circulating Fluidized Bed

Hearth furnace coke (HOK), a special type of lignite (brown-coal)coke produced in a manufacturing process called `hearth furnace process', and portlandite (Ca(OH)₂) particles were placed ina circulating fluidized bed reactor. Defined model waste gases containing HCl/SO₂/Hg⁰/Hg²⁺ and organic compounds were injected into the reactor to investigate the adsorption of different mercury species. Elemental mercuryreacted immediately with HCl to form HgCl₂, but for Hg²⁺ further investigations had to be made, because todaygas cleaning plants still have problems in observing national limits for the mercury output. The temperature, the mercury content of the gas, and its content of acid compounds as majorinfluences in cleaning exhaust gases were varied without relevantpositive effects on the adsorption rate which decreased from nearly 100% in the first five minutes to unsatisfactory20% some minutes later. The mercury load on the HOK particles onlyshowed a value of 60 μg Hg g^-1 HOK. Then organic compounds (guide pollutants such as 1-chlorobutane, monochlorobenzene, toluene, and naphthalene, which are alwayspresent in incineration plant exhaust gases) were added to thegas stream and the results improved significantly. The mercuryload on the HOK particles varied depending on the chemical nature of the organic compound and amounted to 300 μg Hg g^-1 HOK maximum. The measured values of mercury in the clean gas stream fell below 10 μg m^-3. The characterization of the dynamic behavior of mercury in hot, acid waste gases and the analytical identification of mercurysticking to HOK under the influence of organic compounds leadto new methods for improving the effectiveness and performanceof gas cleaning plants.     

Physiological Responses of Transgenic merA-TOBACCO (Nicotiana tabacum) to Foliar and Root Mercury Exposure

Plants expressing a modified bacterial mercury reductase, merA, are highly resistant to Hg(II) toxicity as a result of the enzymatically catalyzed electrochemical reduction of Hg(II) to the much less toxic and volatile Hg(0). merA expression may allow plants to manifest a suite of responses to mercury exposure, making them more capable than wild-type plants of interacting with and removing mercury from contaminated soil or water. We have engineered merA-expressing Nicotiana tabacum (tobacco) as a model plant for examining these responses. Mercury resistance was demonstrated by germinating and growing merA tobacco seeds on semi-solid medium spiked with a HgCl₂ concentration acutely toxic to wild-type plants. On similar growth medium, merA plant roots penetrated a highly concentrated, localized Hg(II) zone of HgS (cinnibar) more readily than wild-type roots. In hydroponic medium spiked with HgCl₂, merA plants maintained higher evapotranspiration activity than wild-type plants. The ability of merA Hg(II)-reductive activity to counter typical plant-catalyzed Hg(0) oxidation to Hg(II) was demonstrated by a lower net foliar absorption of atmospheric Hg(0) than wild-type plants. Mercury translocation through merA plants was examined through reciprocally grafted merA and wild-type tobacco grown on HgCl₂-spiked hydroponic medium. Elevated mercury concentrations in wild-type shoots grafted to merA roots suggest the vertical movement of mercury within merA tissues or plants may be facilitated by dynamic balance between native Hg(0) oxidation and MerA-catalyzed Hg(II) reduction. These experiments demonstrate that merA-engineered tobacco plants display an array of tissue-level and whole-plant attributes which should allow for more efficient mercury extraction and processing compared to the wild-type.     

Determination of Total Mercury in Fish Tissues using Combustion Atomic Absorption Spectrometry with Gold Amalgamation

A simple and rapid procedure for measuring total mercury in fishtissues is evaluated and compared with conventional techniques.Using an automated instrument incorporating combustion, preconcentration by amalgamation with gold, and atomic absorptionspectrometry (AAS), milligram quantities of wet fish tissue wereanalyzed directly for mercury (i.e., without acid digestion). Seven tissue types (skeletal muscle, liver, blood, gonad, brain, gill, and heart) from five species (340 fish) were analyzed. Because of the small quantities of tissue needed for analysis, wedocument the homogeneity of mercury within the tissues and determine a preferred sampling technique and location for skeletal muscle. The precision was found to be generally > 10% (rsd), and the accuracy was determined by using certified reference materials (dogfish muscle, dogfish liver, and oystertissue). Comparisons to conventional cold-vapor AAS (CV-AAS) andisotope dilution inductively coupled plasma mass spectrometry found that the methods give statistically equivalent (p > 0.05) results. Because the combustion-AAS method is faster than conventional CV-AAS and produces no waste reagents, it should be particularly useful for laboratories that analyze large numbers of fish for mercury. The method detection limit for fish-muscle homogenate was estimated at 0.9 ng g^-1.     

Rapid Determination of Mercury in Plant and Soil Samples Using Inductively Coupled Plasma Atomic Emission Spectroscopy, a Comparative Study

The objectives of this study were to simplify sample preparation and validate mercury detection in soil and plant samples using inductively coupled plasma atomic emission spectroscopy (ICP-AES). A set of mercury contaminated and mercury free soil and plant samples were digested and analyzed by ICP-AES, inductively coupled plasma mass spectrometry (ICP-MS), and cold vapor atomic absorption spectroscopy (CVAAS). Results show that mercury measurements in soil and plant samples using ICP-AES were in agreement with those analyzed using ICP-MS and CVAAS. The concentrations of mercury in soils and plant tissues determined by ICP-AES were 92.2% and 90.5% of those determined by CVAAS and ICP-MS, respectively. Digestion of soil samples with 4 M HNO₃ and direct measurement by ICP-AES without reduction of Hg²⁺ to Hg⁰ gave a reasonable and acceptable recovery (92%) for determining Hg in soils. We conclude that ICP-AES with optimized conditions (addition of gold chloride, extension of washing time, linear working range, and selection of wavelength – 194 nm) resulted in reliable detection of mercury in environmental samples.     

Trace metals in sediments and aquatic plants from the Xiangjiang River, China

Purpose

The metal concentrations and Pb isotopic composition in sediments and plants from the Xiangjiang River, China, were investigated to understand the contamination and potential toxicity of metals in sediments; to determine the accumulation and distribution of metals in plant tissues; and to trace the possible pollution source of Pb in sediments and plants.

Materials and methods

Sediments and plants were collected from 43 sampling sites in the study region. After sediments were air-dried and passed through a 63-??m sieve, they were acid-digested and DTPA-extracted for determination of total and bioavailable metals. The plants were separated into roots, leaves, and stems; dried; cut into pieces; and digested with HNO₃?CH₂O₂. Metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and Pb isotopic composition were analyzed by inductively coupled plasma-mass spectrometry.

Results and discussion

Maximum As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in sediments were 47.18, 55.81, 129.5, 161.6, 160.4, 430.7, and 1,098.8?mg?kg^?1, respectively. The bioavailable fractions of As, Cd, Cu, Pb, and Zn had significant linear relationship with their corresponding total contents in sediments while no significant relationship was observed between bioavailable and total contents of Cr and Ni. In general, plant tissues showed higher As, Cd, Cu, Pb, and Zn concentrations and lower Cr and Ni concentrations compared with sediments. The ²⁰⁶Pb/²⁰⁷Pb ratios decreased in the order of total > bioavailable > stems ?? leaves > roots. A strong linear correlation was observed between the ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁷Pb ratios of the plant tissues, sediments, and the possible pollution sources of Pb in the Xiangjiang River.

Conclusions

As, Cd, Cu, Pb, and Zn demonstrated higher contamination levels in sediments and plants compared with Cr and Ni. Cd had highest potential ecological risk. The Pb from anthropogenic sources with low ²⁰⁶Pb/²⁰⁷Pb ratios was preferentially associated with the bioavailable fractions in sediments and accumulated in roots. The Pb in plant tissues is mainly derived from the Pb in sediment and is taken up through the sediment-to-root pathway.     

Mercury Partitioning in Surface Sediments of the Upper St. Lawrence River (Canada): Evidence of the Importance of the Sulphur Chemistry

An intensive survey of mercury speciation was performed at a site on the Upper St. Lawrence River near Cornwall, Ontario, Canada with a history mercury contamination in sediments. Surface sediments were collected every 1.50 h. Total mercury (Hg_total), methylmercury (MeHg), organic carbon, inorganic and organic sulphur were determined in the solid fraction. Dissolved Hg_total, MeHg and dissolved organic carbon (DOC) were measured in pore waters. Concentrations of Hg_total in the upper layers (first 5 cm) were high, ranging from 1.42 to 25.8 nmol g^?1 in solids and from 125 to 449 pM in pore waters. MeHg levels were also high, ranging from 4.34 to 34.1 pmol g^?1 in solids and from 40 to 96 pM in pore waters. This amounts to up to 1.4% of Hg_total present as MeHg in solids and 64% in pore waters. A daily pattern for Hg_total was observed in the solid fraction. The MeHg distribution in solids and pore waters was not correlated with Hg_total or DOC_, suggesting that the concentrations of MeHg are probably more influenced by the relative rates of methylation/demethylation reactions in the sediment–water interface. Acid volatile sulphide levels and DOC were inversely correlated with organic sulphur (S_org) levels suggesting that both parameters are involved in the rapid production of S_org. A positive correlation was also observed between Hg_total and S_org in solids (R?=?0.87, p?<?0.01) illustrating the importance of organic sulphur in the retention and distribution of Hg in the solid fraction of the sediments. The results suggest that variations of Hg_total concentrations in Upper St. Lawrence River surface sediments were strongly influenced by the formation/deposition/retention of organic sulphur compounds in the sediment–water interface.     

Heavy metals in recent sediments and bottom-fish under the influence of tanneries in South Brazil

Selected metals were evaluated in surface sediments from Cadeia and Feitoria Rivers (Brazil), potentially affected by tanneries. Statistical factor analysis of sediment data allowed the identification of critical} metals and priority areas for biological monitoring, i.e., chromium and mercury at the lower course of Feitoria River. Non-piscivorous bottom-fish from the species Rineloricaria cadeae (violinha) were collected at reference and contaminated sites. Chromium was undetected} in fish tissues, and mercury accumulated in individuals living in contact with contaminated deposits. Mercury contents in fish were below World Health Organization quality standard for human consumption (0.5 μg/g). The ratio of total mercury content in fish (wet weight) to sediment (dry weight, <63 μm) was 0.5 and 0.7 at reference and contaminated sites, respectively. A risk assessment based on hazard index showed that maximum consumption of fish from contaminated site by human population should be 32 g/day, while at reference site the allowable amount could reach 140 g/day.     

Anaerobic sediment potential acidification and metal release risk assessment by chemical characterization and batch resuspension experiments

Background, Aim and Scope  Sediments act as a sink for toxic substances (heavy metals, organic pollutants) and, consequently, dredged materials often contain pollutants which are above safe limits. In polluted anaerobic sediments, the presence of sulphides and redox potential changes creates a favorable condition for sulphide oxidation to sulphate, resulting in potential toxic metal release. The oxidation reaction is catalyzed by several microorganisms. Some clean up measures, such as dredging, can initiate the process. The aim of the present work is to assess the acidification and metal release risk in the event of sediment dredging and also to compare two different acid base account techniques with the resuspension results. The oxidation mechanism by means of inoculation with an Acidithiobacillus ferrooxidans strain was also evaluated. Methodology  The sediments were chemically characterized (pH; organic oxidizable carbon; acid volatile sulphides; total sulphur; moisture; Cr, Cu and Zn aqua regia contents). A metal sequential extraction procedure (Community Bureau of Reference, BCR technique) was applied to calculate the Acid Producing Potential (APP) and Acid Consuming Capacity (ACC) of the sediment samples through Fe, Ca²⁺ and SO₄ ²⁻ measurements. The acid base account was also performed by the Sobek methodology (Acid producing potential — AP — calculated with total sulphur and neutralization potential — NP — by titration of the remaining acid after a reaction period with the sample). Fresh sediments were placed in agitated shake flasks and samples were taken at different times to evaluate pH, SO₄ ²⁻ and Cr, Cu, Zn and Fe²⁺ concentration. Some of the systems were inoculated with an Acidithiobacillus ferrooxidans strain to assess the biological catalysis on sulphide oxidation. Results  Sediment chemical characterization showed high organic matter content (5.4–10.6%), total sulphur (0.36–0.86%) and equivalent CaCO₃ percentages (4.5–8%). pH was neutral-alkaline for all of the samples. AVS content was high except for sample 5. The acid base account obtained with the two methods gave different results for the acid generating risk of the samples. A decrease of 0.4 to 3.1 pH units was measured in the agitated shake flasks. In all of the systems, sulphate concentration increased (2,100–2,200 mg L⁻¹ to 2,500–3,000 mg L⁻¹), and positively correlated with the initial total sulphur content of the samples in the inoculated flasks. Cu and Cr in solution were not detected in most of the sampling occasions (<0.5 mg Cu L⁻¹ and <0.5 mg Cr L⁻¹). Zn reached high concentrations (up to 11.8 mg L⁻¹). For every system — except sediment 1 — the lowest pH registered was similar in comparison to inoculated and control systems. The inoculation effect was mostly evidenced in the systems by a higher sulphate release rate compared to the control systems. Discussion  The BCR method categorized all of the samples as potentially acid generating material. The Sobek method using NPR (NP/AP) criteria classified sample 3 as a possible acid generator and samples 1, 2 and 5 with a low acid generation potential. Despite this, all the samples acidified the media in the kinetic tests in at least one of the conditions employed in this work. It would seem that NPR and NNP (NP-AP) risk classification criteria should not be directly used with anaerobic sediments. Appropriate classification levels for sediments should be developed considering the different sulphide reactivity between rock and sediments. Sediment oxidation can cause acidification, which is partially explained by sulphide oxidation. In the samples studied, we found a positive correlation between sulphate increase in solution after oxidation and total sulphur content in the inoculated systems. Significant amounts of Zn could be released to solution while Cr and Cu remained insoluble despite the pH decrease observed. The low Cu and Cr mobility could be explained by the very low solubility of their hydroxides and high affinity for organic matter and iron oxides/hydroxides that might form during sediment oxidation. Dredged sediment management and disposal should be carefully planned. Conclusions  All of the sediment samples lowered the pH media in the laboratory batch resuspension experiments. However, both risk classification criteria (NNP, NPR) from Sobek acid base account were not able to predict the samples’ behavior as accurately as the BCR derived base account. The inoculation effect was mostly associated with a higher sulphate release and not to a lower pH due to acid base equilibrium. Recommendations and Perspectives  Appropriate risk classification levels for sediments should be developed considering the different sulphide reactivity between rock and sediments. ESS-Submission Editor: Dr. Sabine Ulrike Gerbersdorf (sug@st-andrews.ac.uk)     

A simplified method for the gas-liquid chromatographic determination of methyl mercury in fish and shellfish.

A simple acetone wash of the fish sample which removes lipids and other organic materials replaces the cystein cleanup specified in other methods. Methyl mercury is freed by hydrochloric acid, extracted into benzene, and determined with a gas-liquid chromatograph equipped with an electron capture detector. The method is quantitative for methyl mercury levels as low as 0.10 ppm in fish and shellfish. Ethyl mercury chloride may be used as an internal standard to detect unsuspected error or instrumental parameter variation.     

Elemental analysis of solid samples by low temperature plasma ashing and microwave acid digestion

Sixteen elements (Mn, Zn, Cu, Fe, B, Sr, Ba, Cr, Pb, As, Cd, Ni, Co, Se, Sb, Hg) were determined in oils, sediments, plants and marine organisms by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or by Graphite Furnace Atomic Absorption Spectroscopy (GF-AAS) after plasma ashing followed by microwave acid digestion with HNO₃/HCl/H₂O₂. Soil and sediment samples were treated directly in the microwave oven without ashing, but the complete procedure must be applied in case of high organic content. The method was tested on a variety of standard reference materials. Good recoveries were obtained for most of the considered trace elements with less time and reagents consumption than conventional open vessels acid digestion procedures. Hg was determined with good recovery in soil samples by the same method and in organic materials by a modified procedure involving digestion of fresh material with nitric acid in a reflux quartz system.     

Determination of refractory organic matter in marine sediments by chemical oxidation, analytical pyrolysis and solid-state 13C nuclear magnetic resonance spectroscopy

Seeking to quantify the amount of refractory organic matter (ROM), which includes black carbon‐like material (BC), in marine sediments, we have applied a two‐step procedure that consists of a chemical oxidation with sodium chlorite of the demineralized sediments followed by integration of the aromatic C region in the remaining residues by solid‐state ¹³C nuclear magnetic resonance (NMR) spectroscopy. The efficacy for lignin removal was tested by analytical pyrolysis in the presence of tetramethyl ammonium hydroxide (TMAH). Riverine, estuarine and offshore marine sediment samples were collected from the southwest Atlantic coast of Spain, a site of geological and environmental interest. Measured contents of BC‐like material ranged between 3.0 and 45.7% of the total organic carbon. Greater relative BC contents were found in riverine sediments close to urban areas, which show an elevated input of anthropogenic organic material. The contents of BC‐like material in offshore marine sediments (5.5–6.1%) were similar to those previously reported for these kinds of samples. However, NMR and pyrolysis‐GC/MS of the isolated ROM reveals that abundant refractory aliphatic organic material remains in most of the marine samples after chlorite oxidation. We suggest that this pool of aliphatic carbon may play an important role as a stable carbon pool within the global C cycle.     

Method development and sample processing of water,soil, and tissue for the analysis of total and organic mercury by cold vapor atomic fluorescence spectrometry

Atomic Fluorescence-based methods have been developed for measuring ultratrace levels of mercury (Hg) in environmental (water, soil) and biological (fish tissue) samples. In addition, methods for preparation of water, soil, and tissue samples have been developed. For the analysis of total Hg in soil, sediment and fish the samples are digested with concentrated nitric acid in sealed glass ampules, and subsequently autoclaved. Water samples are digested using standard brominating procedures. A Merlin Plus, PS Analytical atomic fluorescence spectrometer (AFS) system equipped with an autosampler, vapor generator, fluorescence detector and a PC based integrator package is used in the determination of total Hg. The determination of Hg mercury species in water, without pre-derivatization, involves adsorbent pre-concentration of the organomercurials onto sulfydryl-cotton fibers. The organic Hg compounds are eluted with a small volume of acidic KBr and CuSO₄ and extracted into dichloromethane. Sediment, soil and tissue samples are homogenized and the organomercurials first released from the sample by the combined action of acidic KBr and CuSO₄ and extracted into dichloromethane. The initial extracts are subjected to thiosulfate clean-up and the organomercury species are isolated as their chloride derivatives by cupric chloride addition and subsequent extraction into a small volume of dichloromethane. Analysis of organic Hg compounds is accomplished by capillary column chromatography coupled with atomic fluorescence detection.     

Titanium Dioxide Nanoparticle Circulation in an Aquatic Ecosystem

Nanotechnology is a dynamically developing field of scientific and industrial interest across the entire world, and the commercialization of nanoparticles (NPs) is rapidly expanding. Incorporation of nanotechnologies into a range of manufactured goods results in increasing concern regarding the subsequent release of engineered NPs into the environment. One of the biggest threats of using NPs is the transfer and magnification of these particles in the trophic chain. The aim of the studies was the evaluation of the distribution of TiO₂ NP contamination in the aquatic ecosystem under laboratory conditions. Bioaccumulation of TiO₂ NPs by plants (Elodea canadensis) and fish (Danio rerio) in the source of contamination was investigated. The studies were focused on the consequences of short-term water contamination with TiO₂ NPs and the secondary contamination of the components of the investigated model ecosystem (plants, sediments). It was found that in the fish and the plants exposed to NP contamination, the amount of Ti was higher than in the control, indicating an effective bioaccumulation of NPs or ions originating from NPs. It was clearly shown that the NPs present in the sediments are available to plants and fish. Additionally, the aquatic plants, an important trophic level in the food chain, can accumulate NPs and be a source of NPs for higher organisms. It was concluded that even an incidental contamination of water by NPs may result in long-term consequences induced by the release of NPs.     

Total mercury and methylmercury mass balance in an alkaline,hypereutrophic urban lake (Onondaga Lake,NY)

A total mercury (total Hg) and methylmercury (CH₃Hg) mass balance was developed for Onondaga Lake, NY, based on sampling of tributaries, sediments, water column, and biota in 1992. Thein situ flux of total Hg and CH₃Hg from sediments to the overlying water and the rate of net CH₃Hg production in the water column were determined experimentally. Fluxes from atmospheric deposition, groundwater, and volatilization were estimated from limited field data and the literature. Ultraclean sampling and analytical techniques developed specifically for Hg were used. Results indicate that tributaries contribute the majority of total Hg entering the lake (13.6 kg in 1992). Other sources of total Hg included groundwater flux (0.02 kg), atmospheric deposition (0.44 kg), and flux from sediments (0.056 kg). Net sedimentation (11.1 kg), outflow (2.8 kg), and volatilization (0.016 kg) were sinks for total Hg. The two major sources of CH3_Hg were tributaries (0.26 kg) and net CH₃Hg production in the water column (0.60 kg). Flux from sediments accounted for only 0.017 kg CH₃Hg. Net sedimentation (0.47 kg), outflow (0.24 kg), and net uptake, by fish (0.20 kg) were sinks for CH₃Hg. Gross sedimentation of CH₃Hg exceeded net sedimentation by 90%, suggesting that release of CH₃Hg from settling particles is a significant process.     

Mercury Levels of Soils,Sediments and Fish in French Guiana,South America

This study examines the level of mercury contamination for different components of the biosphere in French Guiana. The spatial variability of the contamination of the waters, soils and sediments in the catchment area of the Sinnamary River is studied. The contamination of the trophic chain isdiscussed by analysis of the flesh of fish for the principal species represented in nine Guianese rivers, especially species consumed by human populations. The mercury contamination of sediments and soils, is extremely heterogeneous and that of fish is generalised. For carnivorous fish, the average mercury content is 0.48 μg g^-1 (±0.28) (fresh weight) and for non-carnivorous species, 0.05 μg g^-1 (±0.07). The concentrationsmeasured are greater than the European standards forconsumption for 4.7% of the carnivorous individuals.     

An automated turbidimetric method for total sulfur in plant tissue and sulfate sulfur in soils

Abstract

An automated turbidimetric method has been developed for the rapid and accurate determination of sulfate. The method is practical and useful for accurately measuring total sulfur in plant tissues, and extractable sulfate in soils. The principle of intermittent reagent addition is used which eliminates drift and sensitivity changes caused by coating of BaSO₄ on tubing and cell walls. Also, the appropriate chemistry is used to minimize interactions of the wash with the sample at a sampling rate of 30/H. The sensitivity of the method is excellent with a working range of 0 to 15 ppm sulfur for soils. For plant digests the sample solutions are diluted to 0–35 ppm S. The precision as determined by repeated analysis of a soil sample extract was 0.58% RSD with a mean of 9.26 pg/g extractable SO⁼ ₄‐S. On another soil sample using a different extractant and extraction procedure the RSD was 0.64%, mean of 9.26 μg/g. Multiple automated sulfur analyses on a plant tissue digest resulted in an RSD of 0.41% for a sample containing 0.21% S. The automated turbidimetric method for sulfate has excellent precision and sensitivity in plant tissue and soil analyses where gravimetric BaSO₄ assays are not practical.