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Lead Induced Organic Acid Exudation and Citrate Enhanced Pb Uptake in Hydroponic System
Kim, Kwon-Rae,Owens, Gary,Naidu, Ravi,Kwon, Soon-Ik,Kim, Kye-Hoon The Korean Society of Environmental Agriculture 2009 한국환경농학회지 Vol.28 No.2
The influence of Pb-citrate complex formation on Pb uptake and the effect of Pb on organic acid exudation were investigated using four plant species, viz., sunflower (Helianthus annuus L), Indian mustard (Brassica juncea), canola (Brassica napus) and vetiver grass (Vetiveria zizanioides) under hydroponic conditions. Seedlings were exposed to different levels of Pb and Pb-citrate for 24 hrs and subsequently Pb distributions in plant shoot, root and hydroponic solution were measured. The dissolved organic carbon (DOC) concentration generally decreased as the concentration of Pb in the hydroponic solution increased. In contrast to DOC, the total organic acid concentrations exuded from Indian mustard roots significantly increased (424 to 6656 mg $kg^{-1}$) with increased Pb treatment, implying that exuding organic acids were involved in Pb accumulation in Indian mustard. The complexation of Pb with citrate enhanced Pb accumulation in the above ground portions. Lead concentration in Indian mustard increased from 2.05 mg $kg^{-1}$ to 6.42 mg $kg^{-1}$ when the concentration of citrate in solution increased from 0 to 50 mg $L^{-1}$. This result showed enhanced translocation of Pb from root to shoot with observation of transfer coefficient ($K_t$) increase from 2.03E-3 to 5.72E-3.
Kwon-Rae Kim,Gary Owens,Ravi Naidu,Kye-Hoon Kim 한국토양비료학회 2008 한국토양비료학회지 Vol.41 No.1
A detailed understanding and appreciation of the important mechanisms operating at the soil:root interface, commonly identified as the rhizosphere, is critical for evaluating the potential for particular plant species to be successfully used as part of a phytoremediation technique. For specific plants, mechanisms may exist to overcome the inherit limitation of the phytoremediation technique when poorly mobile soil metals are of interest. In the present study, the influence of root exudates on the rhizosphere chemistry of soil and consequential metal uptake were investigated following culture of vetiver grass (Vetiveria zizanioides), recognized as a promising plant for land stabilization, in three different long-term contaminated soils and one non-contaminated control soil. The soil solution pH increased (0.3-1.1 units) following vetiver grass culture and dissolved organic carbon (DOC) also significantly increased in all soils with the highest increase in PP02 (23 to 173 mg L-1). Chemical changes are contributed to root exudation by vetiver grass when exposed to high concentration of heavy metals. Chemical changes, consequently, influenced metal (Cd, Cu, Pb, and Zn) solubility and speciation in the rhizosphere. The highest solubility was observed for soil Ko01 (eg. 2091 and 318 μg L-1 for Cd and Pb, respectively). Initial heavy metal solubility in soils varied with soil and either increased or decreased following vetiver grass culture depending on the soil type. An increase in pH following plant culture generally resulted in a decrease in metal solubility, while elevated DOC due to root exudation resulted in an increase in metal solubility via the formation of metal-DOC complexes. Donnan speciation demonstrated a significant decrease in free Cd and Zn in the rhizosphere and the concentration of Cd, Pb, and Zn in vetiver grass shoot was highly correlated with soluble concentration rather than total soil metal concentration.
Lead Induced Organic Acid Exudation and Citrate Enhanced Pb Uptake in Hydroponic System
Kwon Rae Kim,Gary Owens,Ravi Naidu,Soon Ik Kwon,Kye Hoon Kim 한국환경농학회 2009 한국환경농학회지 Vol.28 No.2
The influence of Pb-citrate complex formation on Pb uptake and the effect of Pb on organic acid exudation were investigated using four plant species, viz., sunflower (Helianthus annuus L), Indian mustard (Brassica juncea), canola (Brassica napus) and vetiver grass (Vetiveria zizanioides) under hydroponic conditions. Seedlings were exposed to different levels of Pb and Pb-citrate for 24 hrs and subsequently Pb distributions in plant shoot, root and hydroponic solution were measured. The dissolved organic carbon (DOC) concentration generally decreased as the concentration of Pb in the hydroponic solution increased. In contrast to DOC, the total organic acid concentrations exuded from Indian mustard roots significantly increased (424 to 6656 mg kg-1) with increased Pb treatment, implying that exuding organic acids were involved in Pb accumulation in Indian mustard. The complexation of Pb with citrate enhanced Pb accumulation in the above ground portions. Lead concentration in Indian mustard increased from 2.05 mg kg-1 to 6.42 mg kg-1 when the concentration of citrate in solution increased from 0 to 50 mg L-1. This result showed enhanced translocation of Pb from root to shoot with observation of transfer coefficient (Kt) increase from 2.03E-3 to 5.72E-3.
Kim Hyunuk,Lee Mina,Lee Jae-Hwang,Kim Kye-Hoon,Owens Gary,Kim Kwon-Rae 한국응용생명화학회 2020 Applied Biological Chemistry (Appl Biol Chem) Vol.63 No.3
In Korea, rapid industrialization has often caused severe soil and water pollution near industrial complexes. Particularly, heavy metal(loid) contamination of agricultural lands could induce serious long-term problems for crop safety and productivity, requiring continual safety assessment. This study investigated heavy metal(loid) contamination of agricultural lands near fifteen industrial complexes. At each of industrial sites in Gyeongsangbuk-do, topsoils and subsoils were collected at two different distances from each site (0–500 m and 500–1000 m). For comparison, at each site, non-polluted soils were also collected more than 1000 m away from each industrial complex. With the exception of one sample, heavy metal(loid) concentration of all soils were lower than the Korean guidelines for soil contamination. However, the difference between the heavy metal(loid) concentrations of Cu, Pb and Zn in topsoil and subsoil increased the closer the samples were the industrial complexes, which implied that these elements were being generated by industrial activities and were freshly loaded on to near surface soils. While the heavy metal(loid) concentration in the studied sites did not exceed the Korean guideline, the geoaccumulation index of each soil indicated that the degree of Cd, Cu, and Pb contamination was heavily or extremely serious in more than twenty of the examined soils. The elevation of specific metals associated with industrial activity in soils in close proximity to industrial sites is of some concern and should be taken into consideration for the future management of agricultural soils around such complexes as well as the industrial complex operation itself.
Galactic Archeology with the AEGIS Survey: The Evolution of Carbon and Iron in the Galactic Halo
Yoon, Jinmi,Beers, Timothy C.,Dietz, Sarah,Lee, Young Sun,Placco, Vinicius M.,Costa, Gary Da,Keller, Stefan,Owen, Christopher I.,Sharma, Mahavir American Astronomical Society 2018 The Astrophysical journal Vol.861 No.2
<P>Understanding the evolution of carbon and iron in the Milky Way's halo is of importance because these two elements play crucial roles in constraining star formation, Galactic assembly, and chemical evolution in the early universe. Here we explore the spatial distributions of the carbonicity, [C/Fe], and metallicity, [Fe/H], of the halo system based on medium-resolution (R similar to 1300)spectroscopy of similar to 58,000 stars in the southern hemisphere from the AAOmega Evolution of Galactic Structure (AEGIS) survey. The AEGIS carbonicity map exhibits a positive gradient with distance, as similarly found for the Sloan Digital Sky Survey carbonicity map of Lee et al. The metallicity map confirms that [Fe/H] decreases with distance from the inner halo to the outer halo. We also explore the formation and chemical evolution history of the halo by considering the populations of carbon-enhanced metalpoor (CEMP) stars present in the AEGIS sample. The cumulative and differential frequency of CEMP-no stars (as classified by their characteristically lower levels of absolute carbon abundance, A(C) <= 7.1, for subgiants and giants) increases with decreasing metallicity and is substantially higher than previous determinations for CEMP stars as a whole. In contrast, that of CEMP-s stars (with higher A(C)) remains almost flat, at a value of similar to 10% in the range -4.0 less than or similar to [Fe/H] less than or similar to -2.0. The distinctly different behaviors of the CEMP-no and CEMP-s stars relieve the tension with population synthesis models assuming a binary mass-transfer origin, which previously struggled to account for the higher reported frequencies of CEMP stars, taken as a whole, at low metallicity.</P>
Kim, Hyuck Soo,Seo, Byoung-Hwan,Kuppusamy, Saranya,Lee, Yong Bok,Lee, Jae-Hwang,Yang, Jae-E.,Owens, Gary,Kim, Kwon-Rae Elsevier 2018 Ecotoxicology and environmental safety Vol.148 No.-
<P>The efficiency of gypsum, as a dissolved organic carbon (DOC) coagulator, for the simultaneous immobilization of two heavy metals (Cd and Pb) and one metalloid (As) in agricultural soils near an abandoned mining site was examined. The agricultural soil was defined as long-term contaminated as As (1540 mg kg(-1)), Cd (55 mg kg(-1)) and Pb (1283 mg kg(-1)) concentrations exceeded the Korean guideline values for As (25 mg kg(-1)), Cd (4 mg kg(-1)), and Pb (200 mg kg(-1)). Gypsum was incorporated into the contaminated soil at 3% (w/w). In comparison two commonly using immobilizing agents (lime and compost), together with a mixture (lime + gypsum) were also included in the pot trial for the cultivation of two medical plants (A. gigas and A. macrocephala) and to evaluate the effectiveness of gypsum on As, Cd and Pb immobilization. The results showed that even though pH change-induced immobilizing agents such as lime were more effective than gypsum at immobilizing Cd and Pb, addition of gypsum also effectively reduced heavy metal phytoavailability as indicated by decreases in the concentration of Cd and Pb in medicinal plants. Furthermore, gypsum and gypsum + lime were also most effective in reducing As concentrations in both plants studied. This was mainly attributed to significant decreases in soil DOC (48-64%) when gypsum and gypsum + lime were applied to the soil. Consequently, it was concluded that enhanced DOC coagulation with gypsum, could be considered as a promising technique for the immobilization of both metals (Cd and Pb) and metalloids (As) in agricultural soils.</P>