Perchlorate Uptake Research Articles

Perchlorate uptake by poly-(diallydimethylammonium chloride) functionalized montmorillonites

Montmorillonite (Mt) is proposed as a promising adsorbent for removing contaminants from water, yet it is unclear whether and how the layer charge density (LCD) of Mt. affects its hydration properties, especially for the capturing performance of anions by polyelectrolyte modified Mt. Here, the feasibility and performance of perchlorate uptake by poly-(diallydimethylammonium chloride) (PDDA) functionalized Mt. (PDDA-Mtx) with different LCD were investigated. PDDA species were loaded via partial intercalation or adsorption on the surface/end sites of Mt. The CEC of Ca-Mtx increased with increasing LCD, while on the contrary for colloidal valence. The perchlorate uptake by Ca-Mtx can be significantly improved by introducing PDDA species. As expected, the PDDA-Mt0.3 showed superior perchlorate capture of up to 0.80 mmol/g due to the relatively high positive zeta potential and loading of un-ionized PDDA. The perchlorate uptake by PDDA-Mtx still maintained largely despite a slight decrease in the presence of co-competing anions NO-3, SO2–4 and PO3–4. The capture behaviors were well characterized by the pseudo-second-order and Langmuir isotherm models, and the natures of spontaneous and endothermic were demonstrated by thermodynamic analysis. Anion exchange and electrostatic were the dominant ways in which perchlorate was captured onto PDDA-Mtx.

Perchlorate detection via an invertebrate biosensor.

Improvised explosive devices (IEDs) are constructed from easily obtainable ingredients that are often unregulated and difficult to trace. Salts of the oxyhalide perchlorate are frequently used as oxidisers in IEDs and in commercially available munitions, thus a reliable detection is needed to aid forensic investigations and the tracing of environmental ground or surface water contamination. We introduce the nematode Caenorhabditis elegans as a biosensor for the presence of perchlorate, a promising alternative to the costly, technically challenging and time-consuming current perchlorate detection methods. Perchlorate uptake dynamics in C. elegans were first validated using ion exchange chromatography followed by assessing the effects of perchlorate on key life-point indices to verify the suitability of the nematodes as a forensic biosensor. Whole genome microarrays and qPCR analyses established that a set of immune and stress response genes were enriched during perchlorate exposure. A nematode strain (agIs219) containing an integrated copy of the significantly overexpressed t24b8.5 gene promoter followed by a GFP reporter gene was shown to fluoresce in a perchlorate dose dependent manner with a limit of detection (LOD) of 0.5 mg mL-1. Whilst chemicals commonly used in the construction of IEDs did not induce fluorescence, exposure to other oxyhalides did, highlighting the presence of possible shared stress response pathways. Burnt wire sparklers containing potassium perchlorate elicited fluorescence while other non-perchlorate containing post-blast explosion matrices did not. This demonstrates how C. elegans can be used to screen for perchlorate at environmental hotspots, an optimization, possibly with other target transgenes, is required to enable the detection of perchlorate at concentrations below 0.5 mg mL-1.

Design, synthesis, and biological evaluation of novel tetrahydroprotoberberine derivatives (THPBs) as proprotein convertase subtilisin/kexin type 9 (PCSK9) modulators for the treatment of hyperlipidemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) modulators may attenuate PCSK9-induced low-density lipoprotein receptor (LDLR) degradation in lysosome and promote the clearance of circulating low-density lipoprotein cholesterol (LDL-C). A novel series of tetrahydroprotoberberine derivatives (THPBs) were designed, synthesized, and evaluated as PCSK9 modulators for the treatment of hyperlipidemia. Among them, eight compounds exhibited excellent activities in downregulating hepatic PCSK9 expression better than berberine in HepG2 cells. In addition, five compounds 15, 18, 22, (R)-22, and (S)-22 showed better performance in the low-density lipoprotein, labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine perchlorate (DiI-LDL) uptake assay, compared with berberine at the same concentration. Compound 22, selected for in vivo evaluation, demonstrated significant reductions of total cholesterol (TC) and LDL-C in hyperlipidemic hamsters with a good pharmacokinetic profile. Further exploring of the lipid-lowering mechanism showed that compound 22 promoted hepatic LDLR expression in a dose-dependent manner in HepG2 cells. Additional results of human ether-à-go-go related gene (hERG) inhibition assay indicated the potential druggability for compound 22, which is a promising lead compound for the development of PCSK9 modulator for the treatment of hyperlipidemia.

Adsorption performance of packed bed column for the removal of perchlorate using modified activated carbon

Abstract The adsorption performance of packed bed column using coconut shell based activated carbon for the removal of perchlorate from water was investigated. The influence of parameters like inlet ion concentration, flow rate and bed height on the breakthrough curves and adsorption performance were studied. The results indicated that the adsorption efficiency increased with increase in the initial concentration and the bed height, decreased with increase in the flow rate which in turn resulted in a shorter saturation time. It also revealed that the throughput volume of the aqueous solution increased with increase in bed height owing to the availability of more adsorption sites. The adsorption kinetics was analysed using three kinetic models viz. Adam- Bohart, Thomas and Yoon-Nelson models. The maximum adsorption capacity increased with increase in flow rate and initial ion concentration but decreased with increase in bed height. The perchlorate uptake data was also analyzed for first and second order kinetics. The regeneration of spent activated carbon was systematically investigated by thermal and chemical regeneration methods under different operating conditions.

Extremely Rapid Uptake of Perchlorate with Release of an Environmentally Benign Anion: Silver Bipyridine Acetate

We report the selective removal of perchlorate from water by a cationic coordination polymer in the highest observed capacity and rate to date. Silver bipyridine acetate [Ag(4,4′-bipy)+][CH3CO2–]·6H2O (bipy = bipyridine) is easily synthesized in water under ambient conditions (60 min with 99.1% yield). The material releases its environmentally benign acetate anions upon perchlorate uptake to 99.9% mol/mol completion in Millipore water. Actual contaminated industrial water from an underground plume (53 ppm initial perchlorate concentration) was treated to 96% mol/mol in 60 min. The uptake capacity is near-record high at 310 mg/g and is 94% complete within 30 min. Perchlorate exchange was also conducted at 1–30 ppm perchlorate typical of underground contaminated source sites, with up to 99.7% mol/mol completion.

Risk assessment of dietary exposure to perchlorate for the Austrian population

ABSTRACTPerchlorate is frequently found as contaminant in a variety of food. Based on analytical data of perchlorate occurrence in food products from the Austrian market, this study calculated dietary perchlorate exposure of the Austrian population for the three age classes of adults, children and infants. Furthermore, a detailed risk assessment was conducted based on the tolerable daily intake (TDI) of 0.3 µg/kg body weight/day, established by the European Food Safety Authority in 2014. Calculations of a scenario of average food consumption did not indicate elevated health risks by dietary perchlorate uptake. Exposure estimates reached only 12%, 26% and 24% of the TDI for adults, children and infants, respectively. However, in a scenario of high consumption, the TDI was exceeded by all age classes with 132%, 161% and 156%. The major cause for this exceedance is the comparatively high perchlorate contamination of spinach, but also other leaf vegetables, legumes and pineapples, leading to elevated exposure of high consumers. Our calculations reveal that the current provisional intra-Union trade reference level for perchlorate in spinach of 0.2 mg/kg, advocated by the European Commission, is not sufficient to protect high consumers against possible health risks. In order to reduce health risks to a tolerable level for all consumers, lowering of the regulatory maximum perchlorate concentrations is indicated. Moreover, a generally diversified diet can also counteract excessive exposure to perchlorate as well as to other harmful food contaminants.

Capture of perchlorate by a surface-modified bio-sorbent and its bio-regeneration properties: Adsorption, computations and biofouling

A magnetic amine-crosslinked reed (MACR) was synthesized by an insitu precipitation method and used for perchlorate uptake. The morphological properties of clean MACR, perchlorate-saturated MACR and bio-regenerated MACR samples were determined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. The adsorption capacities of perchlorate by clean and bio-regenerated MACRs were determined. The density functional theory (DFT) method was employed to evaluate the binding free energies between various anions and ammonium/hydroxy groups. The maximum adsorption (Qmax) of perchlorate by MACR was calculated to be 195.5–232.8 mg/g at 30–50 °C. The theoretical computation of adsorption-free energies indicated that ammonium groups were dominant in the process of perchlorate adsorption; other anions, such as [H2PO4]-, [NO3]- and [SO4]2-, showed relatively higher binding free energies than [ClO4]-, which corresponded to the results of competitive adsorption. The spent MACR was then bio-regenerated in a sealed 250-ml conical flask with perchlorate-reducing bacteria (30 °C, 160 rpm) and reached 81.4% of recovery within 3 days. Some hydrophobic macromolecules of extracellular polymeric substances (EPS) might have attached to the surface of MACR, which was validated by the zeta potential, SEM and excitation emission matrix (EEM) fluorescence spectroscopy results.

Perchlorate Uptake and its Effect on Physiological, Biochemical and Growth Parameters of Eucalyptusplant under Ammonium Perchlorate Stress

Perchlorate is a significant environmental pollutant affecting public health. When entered in ecosystem it is highly toxic. Present investigation focused on the influence of perchlorate on physiological and biochemical parameters of Eucalyptus citriodora and also its accumulation in plant tissue and depletion from soil. Eucalyptus plants were treated with varying concentration of ammonium perchlorate from 1000ppm, 2000ppm, 5000ppm and 10000 ppm. Perchlorate inside the plant tissue and in soil was quantified at regular intervals. Amount of perchlorate inside plant tissue observed to increase with number of days after treatment and is proportional to concentration of perchlorate in soil. Morphological characters like shoot length, root length, number of leaf were observed to decrease with increasing concentration of perchlorate. The present study revealed decrease in chlorophyll and reducing sugar content in leaf tissue under varying concentration of perchlorate and is indirectly proportional to amount of perchlorate. While total protein, proline, and phenol content showed a gradual increase with increase in concentration of perchlorate and in different experimental set up, suggesting increase in non-enzymatic stress parameters with increased level of toxicity. An increased activity of peroxidase enzyme was observed with increased dose of ammonium perchlorate. It can be concluded that perchlorate related influence on plant are both qualitative and quantitative and depends upon its concentration and duration of exposure.

Perchlorate Uptake from Aqueous Solutions by Calcined Mg-Al Layered Double Hydroxides

The calcined layered double hydroxides (CLDHs) with 3:1 Mg/Al molar ratio were observed to acquire a high removal efficiency of perchlorate. And they were applied into perchlorate adsorption process with the initial 100 mg/L perchlorate solution in order to analyze removal efficiencies of perchlorate on various influential factors. The results represented that 1.5 g/L CLDHs could achieve ideal adsorption efficiencies of perchlorate at the pH range of 7–9 and at the temperature of 25°C. The removal efficiencies of perchlorate increased up to a maximum efficiency with the increasing dose of CLDHs. Acidic or highly alkaline environment adversely affected perchlorate adsorption. The adsorption process was found to be endothermic due to the higher adsorption capacity in CLDHs with the increasing temperature. The removal of perchlorate was best represented by the pseudo second-order kinetics model and Langmuir isotherm model. Co-existing anions tests showed that the anions of higher valence had a more significant effect than the monovalent anions during the adsorption process. Finally, the adsorption process was further validated by the X-ray patterns and Fourier-transform Infrared spectra of CLDHs. Results demonstrated potential utility of CLDHs that could be developed into a viable technology for perchlorate removal from water.

Highly selective removal of nitrate and perchlorate by organoclay

An organoclay was prepared using montmorillonite and hexadecylpyridinium chloride (HDPyCl) and tested for the removal of nitrate and perchlorate anions from aqueous solutions. The cationic surfactant modified organoclay was prepared at room temperature using HDPyCl corresponding to 4 times the cation exchange capacity (CEC) of Na-montmorillonite. Powder X-ray diffraction (XRD) analysis of the above organoclay showed a large basal spacing of 40.27Å with the intercalation of HDPy cations in the interlayers probably as a result of a paraffin-type bilayer arrangement. The adsorption data of nitrate and perchlorate were fitted to the Langmuir and Freundlich adsorption isotherms and pseudo-first order and pseudo-second order kinetic models to better understand their adsorption mechanisms. The nitrate and perchlorate uptakes by this organoclay could be described well using the Langmuir isotherm while their uptake kinetics fitted well to the pseudo-second order model. The maximum adsorption capacities of nitrate and perchlorate by the organoclay, HDPy-montmorillonite were calculated at 0.67 and 1.11mmolg−1, respectively. Nitrate and perchlorate uptake kinetics were found to be fast as equilibrium was reached within 4h. Furthermore, the uptakes of nitrate and perchlorate by HDPy-montmorillonite were found to be highly selective in the presence of Cl−, SO42− and CO32−, the most abundant naturally occurring anions. Therefore, the HDPy-montmorillonite could be used as a highly efficient adsorbent for the separation of nitrate and perchlorate from drinking or waste water and ground water.

Removal of perchlorate from aqueous solution by cross-linked Fe(III)-chitosan complex

Cross-linked Fe(III)-chitosan composite (Fe-CB) was used as the adsorbent for removing perchlorate from the aqueous solution. The adsorption experiments were carried out by varying contact time, initial concentrations, temperatures, pH, and the presence of co-existing anions. The morphology of the adsorbent was discussed using FT-IR and SEM with X-EDS analysis. The pH ranging from 3.0–10.2 exhibited very little effect on the adsorption capability. The perchlorate uptake onto Fe-CB obeyed Langmuir isotherm model. The adsorption process was rapid and the kinetics data obeyed the pseudo second-order model well. The eluent of 2.5% (W/V) NaCl could regenerate the exhausted adsorbent efficiently. The adsorption mechanism was also discussed.

Perchlorate uptake and molecular mechanisms by magnesium/aluminum carbonate layered double hydroxides and the calcined layered double hydroxides

A series of Mg/Al carbonate layered double hydroxides (LDHs) with different Mg/Al ratios and their calcined LDHs (CLDHs) were prepared as a promising adsorbent of perchlorate anionic pollutant. The LDHs, CLDHs and reconstructed LDHs were characterized by X-ray diffraction, SEM, Raman and FTIR spectra. The adsorption of perchlorate to the parent LDHs was very weak, and the isotherms fit well to the Freundlich model. The perchlorate uptake was independent of the positive charge density of the hydroxide layers because the interlayer carbonate was not significantly replaced by perchlorate. In contrast, the CLDHs exhibited a high adsorption capacity with a nonlinear isotherm, which was mainly driven by the structural memory effect of the LDHs with perchlorate as an interlayer anion. The perchlorate uptake by the CLDHs was enhanced as the positive layer charge density decreased, which cannot be explained by anion exchange mechanism alone. According to the Cl–O and O–H stretching vibrations of the reconstructed ClO4--LDHs, we proposed that perchlorate transfer a negative charge to positively hydroxide layers via electrostatic interactions, then the oxygen atoms of perchlorate are polarized by the surrounding hydroxyls and form strong hydrogen bonds with the hydroxide layers.

Triplex Blue-shifting Hydrogen Bonds of ClO4–···H–C in the Nanointerlayer of Montmorillonite Complexed with Cetyltrimethylammonium Cation from Hydrophilic to Hydrophobic Properties

In this study, molecular interactions of perchlorate (ClO4(-)), an emerging pollutant, with cetyltrimethylammonium(CTMA(+)) complexed in the nanointerlayer of negatively charged montmorillonite were characterized using the zeta potentials, FTIR, Raman, and XRD spectroscopy and quantified using quantum mechanical calculations and sorption experiments. We found that blue-shifting hydrogen bonds assisted in the uptake of ClO4(-) from water into the nanointerlayer spacing of CTMA(+)-montmorillonite and were tunable according to CTMA(+) loading. FTIR spectra presented an obvious 47 cm(-1) blue shift in the C-H vibration coming from the N-terminal methyl group of CTMA(+) when ClO4(-) was absorbed. Quantum mechanical calculations based on density functional theory demonstrated that triplex blue-shifting hydrogen bonds of C-H···O were formed between the three terminal methyl groups of CTMA(+) and three oxygen atoms of ClO4(-). The contribution of blue-shifting hydrogen bonds to perchlorate uptake switched from a ClO4(-)/CTMA(+) ratio of 0.0453 at low CTMA(+) loadings to a ClO4(-)/CTMA(+) ratio of 0.2563 (5.6-fold) at high CTMA(+) loadings, which can be ascribed to the evolution of the nanointerlayer microenvironments from hydrophilic properties to hydrophobic properties. The blue-shifting hydrogen bond of C-H···O that is tunable with the hydrophobic nature of the organic phase should be recognized to elucidate the biochemical behavior of perchlorate in organisms.

Organoclays of high-charge synthetic clays and alumina pillared natural clays: Perchlorate uptake

Several organoclays were synthesized from different types of high charge synthetic clays using octadecyltrimethylammonium (ODTMA) chloride or polyethylenimine (PEI). Two alumina pillared clays were also prepared using two naturally occurring montmorillonites. These organic–clay and inorganic–clay nanocomposites were characterized by powder X-ray diffraction (XRD) and tested for perchlorate uptake. The results showed that the highest perchlorate uptake capacity of 0.436±0.001 was achieved with ODTMA Na-3-mica followed by 0.269±0.016meq/g with ODTMA Na-2-mica. The uptake of perchlorate by synthetic Na-n-micas is as follows: ODTMA Na-3-mica>ODTMA Na-2-mica>ODTMA Na-1-mica>ODTMA Na-4-mica. Perchlorate uptake isotherms were determined for both ODTMA Na-3-mica and ODTMA Na-2-mica as a function of perchlorate concentration but apparently equilibrium was not achieved in both cases. The uptake of perchlorate by the ODTMA Na-n-micas could be attributed to exchange with chloride ions of the neutral surfactant occluded in between cationic chains during the cation exchange process. Organoclays prepared with PEI and hydroxy Al polymer pillared clays and their calcined counterparts showed little or no uptake because excess positive charge was not created in the interlayers in these nanocomposites unlike in the organoclays with Na-n-micas.

Perchlorate adsorption from aqueous solution on inorganic-pillared bentonites

In order to remove perchlorate (ClO4-) from water via adsorption, three modified inorganic-bentonites, such as hydroxy-aluminum pillared bentonite (Al-Bent), hydroxy-iron pillared bentonite (Fe-Bent), and mixed hydroxy-iron–aluminum pillared bentonite (Fe–Al-Bent), were synthesized and characterized. Bench-scale batch experiments were performed to study mechanisms behind the adsorption phenomenon and explore the factors affecting the perchlorate adsorption on pillared bentonites. The significant increase of interlayer spacing, BET surface area and total pore volume suggested a larger amount of active adsorption sites of the pillared bentonites surface and a wider perchlorate channel from the surface to the inner adsorption sites of bentonites, respectively. The results during adsorption process represented that the adsorption capacity of perchlorate followed the order: Fe-Bent>Fe–Al-Bent>Al-Bent. The perchlorate uptake on these three modified bentonites from 0.1mmol/L solution rapidly attained equilibrium within 100min. Pseudo-second-order kinetic model could provide satisfactory fitting of the kinetic data (R2>0.99). The Langmuir model fitted the adsorption isotherm very well (R2>0.98). The thermodynamic analysis indicated that the adsorption process was endothermic and spontaneous in nature. The pH changes appeared to have a little impact on the perchlorate adsorption performance using the Fe-Bent. While perchlorate removal by Al-Bent and Fe–Al-Bent decreased significantly with the increase of pH. Co-existing anions tests showed that the order of anion influence of the adsorption amount of ClO4- on pillared bentonite was PO43->SO42->NO3-. The present study confirmed that inorganic-pillared bentonites would be one of candidates for perchlorate adsorbent.

Predicting perchlorate uptake in greenhouse lettuce from perchlorate, nitrate, and chloride irrigation water concentrations.

Perchlorate (ClO) has been detected in edible leafy vegetables irrigated with Colorado River water. The primary concern has been the ClO concentration in lettuce ( L. var. L.). There has been a limited number of studies on ClO uptake, but the interactive effect of other anions on ClO uptake is not known in detail. We conducted a greenhouse ClO uptake experiment using two types of lettuce (iceberg and butterhead) to investigate the interaction of uptake of ClO, Cl, and NO on ClO uptake under controlled conditions. We examined three concentrations of ClO, 40, 220, and 400 nmol/L; Cl at 2.5, 13.75, and 25 mmol/L; and NO at 2, 11, and 20 mmol/L. Perchlorate was taken up the most in lettuce when ClO was the greatest and NO and Cl were lowest in concentration in the irrigation water. More ClO was detected in leafy material than in root tissue. In general, the outer leaves of iceberg and butterhead lettuce contained more ClO than did the inner leaves. The results indicate that selective ClO uptake occurs for green leaf lettuce. A predictive model was developed to describe the ClO concentration in lettuce as related to the Cl, NO, and ClO concentration in the irrigation water. Research results can be utilized to elucidate the effect of salts on the accumulation and uptake of ClO by edible leafy vegetables.

Removal of perchlorate by synthetic organosilicas and organoclay: Kinetics and isotherm studies

In this study, octadecyltrimethylammonium (ODTMA) chloride was used to prepare MCM-41 at room temperature while MCM-48 and a mesoporous layered organosilica (MCM-50) were synthesized under hydrothermal conditions using cetyltrimethylammonium (CTMA) bromide. These synthetic organosilicas in addition to a commercially available organoclay, Cloisite® 10A were characterized by powder X-ray diffraction (XRD) and tested with the occluded surfactant as adsorbents for perchlorate. Adsorption data were modeled using the Langmuir and Freundlich adsorption isotherms. Adsorption kinetics data were tested using pseudo-first-order, pseudo-second-order and intraparticle (in pores of MCM-41 and MCM-48 or interlayers in the case of layered silica and organoclay, Cloisite®) diffusion models. The results showed that the highest perchlorate uptake capacities were achieved with MCM-48 silica (0.421±0.007meq/g) followed by mesoporous layered organosilica (0.400±0.006meq/g). Cloisite® 10A and MCM-41 silica adsorbed 0.280±0.003 and 0.246±0.003meq/g of perchlorate, respectively. Kinetics studies showed that the adsorption followed pseudo-second-order kinetics model. The good fit of the experimental data and the values of correlation coefficients (R2) indicated the applicability of Langmuir model to perchlorate adsorption in the present study.

Perchlorate uptake by wheat straw based adsorbent from aqueous solution and its subsequent biological regeneration

A new innocuous disposal for perchlorate was presented in this study. Perchlorate was first concentrated by wheat straw based adsorbent, and then biologically reduced by mixing with heterotrophic bacteria. The physicochemical properties of modified wheat straw (MWS) were evaluated by SEM, BET specific area, TGA, 13C solid state NMR and Raman spectra. The adsorption capacity for perchlorate was determined by the kinetics and isotherm tests. The surface areas of the raw wheat straw and MWS were in range of 4.6–5.9m2g−1, which illustrated the absence of porous adsorption in potential adsorption mechanism. The uptake of perchlorate by MWS was based on ion exchange, which would benefit the biological reduction on surface of the biosorbent. The maximum adsorption capacity (Qmax) of perchlorate by MWS was about 119.0mgg−1 (20°C) and decreased as temperature grew. The mixed perchlorate-reduction bacteria could reduce about 91% of loaded perchlorate (23.94mgg−1) on MWS in the first biological-reduction cycle and 87% in second cycle, indicating an available method of innocuous disposal for concentrated perchlorate wastes.

Montmorillonite modified with hexadecylpyridinium chloride as highly efficient anion exchanger for perchlorate ion

Details of the anion-exchange properties of Na-montmorillonite modified with hexadecylpyridinium chloride (HDPyCl-montmorillonite) for perchlorate ions are reported herein. The perchlorate uptake on HDPyCl-montmorillonite from 0.01mmol/dm3 or 0.10mmol/dm3 solution rapidly attained equilibrium within 4h. The perchlorate uptake on HDPyCl-montmorillonite followed the Langmuir isotherm model with capacity of 1.02mmol/g. The perchlorate uptake of 0.70–0.80mmol/g on HDPyCl-montmorillonite persisted in a wide pH range of 4–10. High selectivity of HDPyCl-montmorillonite for perchlorate ion was reflected in the high distribution coefficient values (>104cm3/g) with selectivity sequence of HPO42−<SO42−<NO3−<ClO4− from multi-anion solution of 0.10, 1.0, or 2.0mmol/dm3. This selectivity sequence corresponded to the sequence of increasing hydration energy of anions. These data revealed that the anion uptake on HDPyCl-montmorillonite accompanied with release of chloride ion into solution through anion-exchange processes.

Perchlorate Uptake in Spinach As Related to Perchlorate, Nitrate, And Chloride Concentrations in Irrigation Water

Several studies have reported on the detection of perchlorate (ClO(4)(-)) in edible leafy vegetables irrigated with Colorado River water. However, there is no information on spinach as related to ClO(4)(-) in irrigation water nor on the effect of other anions on ClO(4)(-) uptake. A greenhouse ClO(4)(-) uptake experiment using spinach was conducted to investigate the impact of presence of chloride (Cl(-)) and nitrate (NO(3)(-)) on ClO(4)(-) uptake under controlled conditions. We examined three concentrations of ClO(4)(-), 40, 220, and 400 nmol(c)/L (nanomoles of charge per liter of solution), three concentrations of Cl(-), 2.5, 13.75, and 25 mmol(c)/L, and NO(3)(-) at 2, 11, and 20 mmol(c)/L. The results revealed that ClO(4)(-) was taken up the most when NO(3)(-) and Cl(-) were lowest in concentration in irrigation water. More ClO(4)(-) was detected in spinach leaves than that in the root tissue. Relative to lettuces, spinach accumulated more ClO(4)(-) in the plant tissue. Perchlorate was accumulated in spinach leaves more than reported for outer leaves of lettuce at 40 nmol(c)/L of ClO(4)(-) in irrigation water. The results also provided evidence that spinach selectively took up ClO(4)(-) relative to Cl(-). We developed a predictive model to describe the ClO(4)(-) concentration in spinach as related to the Cl(-), NO(3)(-), and ClO(4)(-) concentration in irrigation water.