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Item Comparison of Cd(II) adsorption properties onto cellulose, hemicellulose and lignin extracted from rice bran(Elsevier Ltd, 2021-06) Wu C; Ren M; Zhang X; Li C; Li T; Yang Z; Chen Z; Wang LRice bran, an underutilized by-product obtained from outer rice layers, has received wide interest due to its abundance, eco-friendliness, and low cost. In this research, cellulose, hemicellulose and lignin as the main components of rice bran were fractionated, and their Cd(II) adsorption capacity, behavior and mechanism were further studied. The adsorption capacity of cellulose for Cd(II) was 5.79 mg/g within the equilibrium time of 10 min, which was 1.8 and 3.6 times those of hemicellulose and lignin, respectively. The Cd(II) adsorption onto cellulose exhibited monolayer surface behavior, whilst the heterogeneous adsorption behavior was observed for hemicellulose and lignin. These differences were related to the discrepancy of morphology and chemical composition in three polymers. The multi-hole sticks morphology of cellulose and porous blocky structure of hemicellulose were observed, while lignin showed compact and agglomerated blocky structure. Cellulose had numerous available adsorption sites including the oxygen-containing functional groups, which bonded with Cd(II) driven by chemical interaction. In conclusion, it highlights that cellulose from rice bran has the great potential of being applied as adsorbent for the Cd(II) removal.Item Plant associated soil mechanisms of cadmium uptake and translocation in chicory and plantain : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Environmental Science at Massey University, Palmerston North, New Zealand(Massey University, 2021) Ubeynarayana, NilushaCadmium (Cd) is a non-essential trace element that is extensively distributed in the environment. Cadmium is effectively absorbed by plant roots and transported to its aerial parts and plants growing in soils with high Cd concentration can accumulate Cd in their roots and shoots to levels which can threaten human and animal health. Elevated Cd concentrations in New Zealand agricultural soils are a function of the country’s long-term history of using Cd-contaminated phosphate fertiliser. Recent studies have identified that two forage species chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.), which are increasingly used in New Zealand agriculture, accumulate a significantly higher shoot Cd concentration than traditional pasture species. The variation in Cd accumulation between forage species suggests that different plants have different abilities to absorb Cd in roots and translocate this trace element from roots to shoots. Thus, Cd uptake and the potential translocation of Cd to aerial tissues deserves more research, particularly for forage species of economic importance to countries such as New Zealand, where agriculture is dependent on pastoral grazing systems. Information from such studies will be useful in mitigating the continuing risk of Cd transfer into the food chain. The overall aim of this thesis is to better understand Cd uptake and translocation mechanisms in chicory and plantain. Cadmium uptake by plant roots is a function of rhizosphere soil chemistry and the interaction between plant roots and soil solution. Plants exude Low Molecular Weight Organic Acids (LMWOA) into soil solution and these play a key role in regulating Cd bioavailability. A pot trial was conducted to evaluate the influence of increasing soil Cd concentration on the secretion of LMWOAs by chicory and plantain roots and to analyse their impact on plant Cd uptake. Chicory and plantain were grown under increasing Cd levels and showed variable secretion of oxalic, fumaric, malic and acetic acids as a function of Cd treatment. Results revealed that the primary cause for the significant increase of shoot and root Cd concentration in both chicory and plantain, as a function of treatment level, is the significantly greater bioavailable Cd concentration in soil solution with increasing Cd treatment level. The significantly higher shoot Cd accumulation in chicory (18.63 mg Cd/kg DW) than plantain (4.22 mg Cd/kg DW) at the highest tested soil Cd concentration (1.6 mg Cd/kg) can be explained by increased acetic acid and reduced fumaric acid excretion from chicory relative to plantain. Increased understanding of Cd translocation mechanisms in plants requires knowledge of the free Cd2+ ion concentration in xylem saps. However, the determination of low concentrations of free Cd2+ ions in a low volume of xylem sap poses an analytical challenge. To overcome this limitation, a thiosalicylic-acid-modified carbon-paste electrode was developed as an alternative and reliable measurement tool for the detection of free Cd2+ ions in environmental samples, including xylem saps. Compared to other Cd2+ ion ligands used to develop Cd2+-ion-specific electrodes in literature, thiosalicylic acid is a readily available solid, which is stable to air, making it a conveniently handled ligand. The developed electrode showed a lower detection limit of 11 μg Cd/L (0.1 10-6 mol Cd/L) with a linear range from 20 to 100 μg Cd/L (0.18 10-6 to 0.88 10-6 mol Cd/L). To the best of my knowledge, this is the first time a Cd2+ ion-specific electrode was developed to determine free Cd2+ ion concentration in plant xylem sap. The modified electrode has the ability to distinguish between total Cd and free Cd2+ in solution and measure only the free Cd2+ ions in environmental samples, including xylem sap, with high precision (RSD<5%). Subsequent analysis using the thiosalicylic acid modified electrode showed that Cd is mainly in a complex form in chicory and plantain xylem sap. Therefore, a glasshouse experiment was set up with six increasing Cd concentrations in hydroponic solution to assess the impact of LMWOA on xylem sap Cd translocation and shoot accumulation in chicory and plantain. Results revealed that both chicory and plantain showed variable production of oxalic, fumaric, citric, malic and acetic acids with increasing Cd concentration in the hydroponic media. The higher shoot Cd accumulation (by 28-208%) in chicory compared to plantain can be explained in terms of variations in LMWOA production between chicory and plantain. Functional relationship analysis showed that the primary cause for higher shoot Cd concentration in chicory relative to plantain is fumaric acid production in chicory xylem sap which may bind with Cd in chicory and translocate the metal towards shoots. To explore the specific role of fumaric and acetic acids on Cd uptake and translocation in chicory, a glasshouse experiment was conducted with the external addition of fumaric and acetic acid into the hydroponic solution. Increasing fumaric acid concentration in the hydroponic solution showed the ability to reduce Cd uptake and translocation in chicory with a maximum reduction achieved at 10 mg/L and 50 mg/L fumaric acid treatment for root and shoot Cd accumulation, (respectively) for a solution concentration of 1 mg/L Cd. The shoot Cd concentration significantly increased at lower acetic acid treatment levels (1 mg/L) and reduced with increasing acetic acid concentrations from 10 mg/L to 50 mg/L in the presence of 1 mg Cd/L solution concentration. However, the root Cd accumulation increased as a function of acetic acid concentration in the hydroponic solution up to 50 mg/L acetic acid treatment. The root: shoot Cd concentration ratio showed a significant positive correlation (R=0.729 P<0.05) with acetic acid treatments (up to 50 mg/L treatment). Chicory biomass significantly reduced at all LMWOA treatments compared to the control treatment in the presence of 1 mg Cd/L Cd level, showing that there was a limited potential ameliorative effect of LMWOA on Cd toxicity at any concentration for the experimental conditions used in this study. This study highlights that variations in plant root LMWOA secretion and xylem sap LMWOA production between chicory and plantain can explain the different shoot Cd accumulation characteristics of these two forage species. This work shows that fumaric acid plays a fundamental role in both Cd uptake and translocation in chicory, while such a role is not clear for plantain. Low secretion of fumaric acid by roots and production of fumaric acid in chicory xylem sap aid to increase shoot Cd accumulation in chicory compared to plantain while low acetic acid secretion by chicory roots supports the high shoot Cd accumulation in chicory compared to plantain. Future work is recommended to develop a new cultivar of chicory which express traits of variations in fumaric acid production and acetic acid production. Such work may yield new cultivars of chicory which restrict the translocation of Cd from roots to shoots in this important forage species. The future application of this work is to help develop strategies which could assist in mitigating high Cd accumulation in offal to maintain the standards of New Zealand’s food production.Item Investigations into the uptake and effects of long-term cadmium and arsenic exposure on the earthworm Eisenia fetida : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Wellington, New Zealand(Massey University, 2020) Dharmadasa, LokugamaCadmium (Cd) and arsenic (As) are trace elements that differ in their chemistries but are both highly toxic, and common soil contaminants in agricultural land and contaminated sites. Their potential impacts range from adverse effects on soil-dwelling organisms to uptake into food and leading to human exposures. This study examines the uptake and effects of Cd and As individually and in mixtures primarily on the earthworm Eisenia fetida on up to three consecutive generations, and the potential for recovery when exposure ceases. Exposure ranges were selected to minimise mortality and permit reproduction. Key variables examined were contaminant concentrations and associated trace elements in worm tissue, growth, reproduction, and levels of gene expression. In worms exposed to Cd-spiked soils, Cd accumulation was rapid. Three key factors determining [Cd] in worm tissue were exposure level, time, and the bioconcentration factor (BCF), which increased with decreasing soil [Cd]. Results indicate that for all exposure conditions, and given enough time, Cd accumulation will continue until a lethal tissue level is reached. This point may be either before or after reproduction has occurred (depending on circumstances), but indicates a need to re-examine standardised approaches to toxicity testing for cumulative and biologically persistent contaminants such as Cd. The biological half-life for Cd loss was 6.5 months. This implies that worms that have been exposed to elevated Cd for more than a few weeks would unable to eliminate much of the accumulated burden over their normal lifetimes. Worms exposed to Cd took longer to reach sexual maturation, and at higher exposures, cocoon production progressively decreased from generation to generation. However, there were differences depending on the exposure level. At the lowest level (30 mg/kg), first generation worms returned to clean soil showed a large rebound effect, and by the third generation there was a recovery in cocoon production. By contrast, for higher (90 and 270 mg/kg) and longer (56 d and 84 d) exposures worms performed more poorly, suggesting that there is a tissue Cd threshold beyond which recovery becomes challenging. Evidence from gene expression results are consistent with the idea that this threshold corresponds to a point at which the Cd-sequestering protein metallothionein (MT) has reached saturation, as can also occur in human kidney tissue. Below this point, worms transferred to clean soils will recover. Above it, they will not. As (spiked as arsenate, AsO₄³⁻) also accumulated in worm tissue with exposure concentration and time, but showed some distinct differences compared to Cd. Modest As exposure extended for longer than 28 d had the unusual effect of stimulating growth and causing excessive cocoon production, an effect likely to be missed in most standardised tests. The effects are not thought to be related to parasite suppression, because they were accompanied by large-scale changes to gene expression. Despite appearing beneficial, by the second generation it was clear that effects of the As exposure were overwhelmingly negative, both in terms of extremely low survival rates and the delayed growth of surviving earthworms. Perhaps more notably, results for both the lower exposure condition (10 mg/kg soil As) and As-exposed worms returned to clean soils, suggest there are circumstances where As may promote its own uptake in a positive feedback loop. If correct such an effect may be linked to an increase in uptake of phosphate (PO₄³⁻) for cellular repair, with co-uptake of arsenate (AsO₄³⁻, which is isomorphous). A parallel mechanism is known for marine fish. Remarkably, results suggest that Cd exposure may have also caused an increase in As uptake, from soils that contained only natural [As]. Though a tentative finding, such an effect would be consistent with the idea that any contaminant that causes cellular damage in an invertebrate may trigger a need for more soil phosphate, presumably with some As co-uptake. This would also imply that many (presumed) single contaminant exposures whether in the laboratory or the field may in fact be As co-exposures. Relevant to this, the adverse impacts of As and Cd co-exposure were found to be more severe than effects of exposure to either contaminant alone; despite the fact the lower amounts of each contaminant were taken up under the co-exposure condition. This result supports an argument that soil guideline values derived from single contaminant toxicity experiments may be insufficiently protective for soil invertebrates in many real-life settings. Gene expression results were useful as an interpretive tool, with numbers and overlaps of differentially expressed genes being more useful than knowledge of the subset of named genes and their putative functions. Exposure to Cd or/and As triggered large-scale changes in gene expression, indicating ‘organism-wide’ biochemical responses and providing circumstantial evidence that supported particular interpretations, such as existence of an MT saturation-threshold, and the existence of substantive biochemical changes between lower and higher As exposures. Analysis of differentially expressed genes in common between Cd-only, As-only and co-exposure suggests existence of both similar and different impacts of toxicity under the three conditions.Item The effect of dietary cadmium on kidney function in cats : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2017) Anderson, Jeanette M JDue to the requirement for meat in feline diets, this study aimed to investigate the potential effects on kidney function in cats of cadmium accumulation in meat products due to pasture management practices. Cadmium may be a causal factor in feline Chronic Kidney Disease (CKD). Twenty-seven domestic short hair cats were randomly selected from the colony population of the Feline Nutrition Unit of Massey University and assigned to three experimental groups (n=9), which were balanced for age and sex. Each group received one of the three experimental diets designed to represent the full range of potential cadmium concentrations that cats may be exposed to on wet diets in New Zealand. Diets were fed ad libitum for a 6-month period. Kidney function was examined at baseline and after 3 and 6 months by measuring glomerular filtration rate (GFR) using iohexol clearance analysed by high performance liquid chromatography (HPLC). Blood and urine analyses were also conducted on a monthly basis. While GFR fluctuated over the study period no significant differences were found either between groups at the end, or within each group when compared at the beginning and end of the study. Although overall no evidence of CKD was observed, an unexplained trend of weight loss was observed in females receiving the two diets containing the highest cadmium levels, which may simply have reflected reduced dietary palatability. The results of the study showed no detectable effects of feeding the three diets for 6 months; however, an extended trial period may be required to fully investigate the longer term effects of cadmium levels and other dietary factors on the development of CKD. In particular, more work is needed to explore the potential for genetic and/or functional differences in mechanisms which are involved in the transport, and/or deposition of cadmium, or are protective against cadmium toxicity in cats and to further define normal parameters and standard approaches in measuring GFR in cats.Item Supplying silicon alters microbial community and reduces soil cadmium bioavailability to promote health wheat growth and yield(Elsevier, 30/06/2021) Song A; Li Z; Wang E; Xu D; Wang S; Bi J; Wang H; Jeyakumar P; Li Z; Fan FSoil amendments of black bone (BB), biochar (BC), silicon fertilizer (SI), and leaf fertilizer (LF) play vital roles in decreasing cadmium (Cd) availability, thereby supporting healthy plant growth and food security in agroecosystems. However, the effect of their additions on soil microbial community and the resulting soil Cd bioavailability, plant Cd uptake and health growth are still unknown. Therefore, in this study, BB, BC, SI, and LF were selected to evaluate Cd amelioration in wheat grown in Cd-contaminated soils. The results showed that relative to the control, all amendments significantly decreased both soil Cd bioavailability and its uptake in plant tissues, promoting healthy wheat growth and yield. This induced-decrease effect in seeds was the most obvious, wherein the effect was the highest in SI (52.54%), followed by LF (43.31%), and lowest in BC (35.24%) and BB (31.98%). Moreover, the induced decrease in soil Cd bioavailability was the highest in SI (29.56%), followed by BC (28.85%), lowest in LF (17.55%), and BB (15.30%). The significant effect in SI likely resulted from a significant increase in both the soil bioavailable Si and microbial community (Acidobacteria and Thaumarchaeota), which significantly decreased soil Cd bioavailability towards plant roots. In particular, a co-occurrence network analysis indicated that soil microbes played a substantial role in rice yield under Si amendment. Therefore, supplying Si alters the soil microbial community, positively and significantly interacting with soil bioavailable Si and decreasing Cd bioavailability in soils, thereby sustaining healthy crop development and food quality.Item Influence of Soil Moisture Status on Soil Cadmium Phytoavailability and Accumulation in Plantain (Plantar lanceolata)(MDPI (Basel, Switzerland), 2018-03) Stafford A; Jeyakumar P; Hedley M; Anderson CThe effect of fluctuating soil moisture cycles on soil cadmium (Cd) phytoavailability was investigated in a pot trial with two contrasting soils (Kereone (Allophanic), total Cd 0.79 mg kg−1; and Topehaehae (Gley), total Cd 0.61 mg kg−1) that were either sown with plantain (Plantago lanceolata) or left unseeded. Varying soil moisture contents were established using contrasting irrigation regimes: “flooded” (3 days flooded and then 11 days drained); or “non-flooded” (irrigation to 70% of potted field capacity every 7 days). Overall, there was no significant difference in mean 0.05 M CaCl2 soil extractable Cd concentrations or plant tissue Cd concentrations between flooded and non-flooded irrigation. However, there was a consistent trend for an increase in soil extractable Cd concentrations following irrigation, regardless of the irrigation regime. Mean soil extractable Cd and plant tissue Cd concentrations were significantly greater (approximately 325% and 183%, respectively) for the Topehaehae soil than the Kereone soil, despite the lower soil total Cd concentration of the Topehaehae soil. These results indicate that Cd solubility is sensitive to increases in soil moisture following periods of soil drainage, but insensitive to short-term periods of soil saturation. Plant tissue Cd concentrations in Cd-sensitive forage crops such as plantain are likely to be greater following large rainfall events over summer and autumn. This has the potential to increase animal dietary Cd exposure and rate of liver/kidney Cd accumulation.Item Enhanced removal of arsenic and cadmium from contaminated soils using a soluble humic substance coupled with chemical reductant.(1/03/2023) Wei J; Tu C; Xia F; Yang L; Chen Q; Chen Y; Deng S; Yuan G; Wang H; Jeyakumar P; Bhatnagar ASoil washing is an efficient, economical, and green remediation technology for removing several heavy metal (loid)s from contaminated industrial sites. The extraction of green and efficient washing agents from low-cost feedback is crucially important. In this study, a soluble humic substance (HS) extracted from leonardite was first tested to wash soils (red soil, fluvo-aquic soil, and black soil) heavily contaminated with arsenic (As) and cadmium (Cd). A D-optimal mixture design was investigated to optimize the washing parameters. The optimum removal efficiencies of As and Cd by single HS washing were found to be 52.58%-60.20% and 58.52%-86.69%, respectively. Furthermore, a two-step sequential washing with chemical reductant NH2OH•HCl coupled with HS (NH2OH•HCl + HS) was performed to improve the removal efficiency of As and Cd. The two-step sequential washing significantly enhanced the removal of As and Cd to 75.25%-81.53% and 64.53%-97.64%, which makes the residual As and Cd in soil below the risk control standards for construction land. The two-step sequential washing also effectively controlled the mobility and bioavailability of residual As and Cd. However, the activities of soil catalase and urease significantly decreased after the NH2OH•HCl + HS washing. Follow-up measures such as soil neutralization could be applied to relieve and restore the soil enzyme activity. In general, the two-step sequential soil washing with NH2OH•HCl + HS is a fast and efficient method for simultaneously removing high content of As and Cd from contaminated soils.
