Search

Cadmium (Cd) is a widespread environmental toxic contaminant, which causes serious health-related problems. In this study, human intestinal cell line (Caco-2 cells) and normal human liver cell line (HL-7702 cells) were used to investigate the toxicity and bioavailability of Cd to both cell lines and to validate these cell lines as in vitro models for studying Cd accumulation and toxicity in human intestine and liver. Results showed that Cd uptake by both cell lines increased in a dose-dependent manner and its uptake by Caco-2 cells (720.15 μgmg-1 cell protein) was significantly higher than HL-7702 cells (229.01 μgmg-1 cell protein) at 10mg L-1. A time- and dose-dependent effect of Cd on cytotoxicity assays (LDH release, MTT assay) was observed in both Cd-treated cell lines. The activities of antioxidant enzymes and differentiation markers (SOD, GPX, and AKP) of the HL-7702 cells were higher than those of Caco-2 cells, although both of them decreased significantly with raising Cd levels. The results from the present study indicate that Cd above a certain level inhibits cellular antioxidant activities and HL-7702 cells are more sensitive to Cd exposure than Caco-2 cells. However, Cd concentrations <0.5mg L-1 pose no toxic effects on both cell lines. [ABSTRACT FROM AUTHOR]

Anthropogenic chromium (Cr) pollution in soils poses a great threat to human health through the food chain. It is imperative to understand Cr accumulation properties in common vegetables because the proportion of vegetables consumed has increased with the improvement of living standards. Th is study investigated Cr accumulation in pak choi (Brassica chinensis L.) grown on six representative agricultural soils in China. Chromium concentration in the edible parts of pak choi generally increased with soil Cr concentrations following the order: Ustic Cambosols > Periudic Argosols > Mollisols > Calcaric Regosols > Stagnic Anthrosols > Udic Ferrisols. Simple correlation analysis indicated that Cr concentration in pak choi was signifi cantly correlated with the total Cr, Mehlich-3--extractable Cr, and Cr(VI). Stepwise multiple regression analysis also demonstrated that the phytoavailability of Cr was strongly correlated with the extractable fraction by Mehlich-3, total Cr concentration, soil organic matter, and Fe(II). Critical Cr concentrations in these six soils were evaluated for pak choi based on the maximum safe level for daily intake of Cr. Total soil Cr can be used as Cr thresholds for potential dietary toxicity in pak choi. Mehlich-3--extractable Cr is most suitable to be used as Cr thresholds for Periudic Argosols, Udic Ferrisols, Mollisols, and Ustic Cambosols, with values of 20.7, 15.8, 21.2, and 20.4 mg kg-1, respectively, whereas Cr(VI) is most suitable for Calcaric Regosols and Stagnic Anthrosols, with values of 26.5 and 28.0 mg kg-1, respectively. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the ionic speciation (ISP) of reclaimed wastewater (RWW) and potential effects of 11-year of irrigation with RWW on the quality of soil equated with well-water (WW) irrigation. Most of nutrients in RWW are readily available for plant uptake and are free ionic species, while more than around 80% of aluminum (Al), lead (Pb), chromium (Cr) and copper (Cu) are complexed with organic matter. The study shows that the RWW irrigation increased the total concentrations and availability of nonessential elements and nutrients, sodicity and soil salinity by two to three times equated with WW-irrigated soils.

Spatial imaging of cadmium (Cd) in the hyperaccumulator Sedum alfredii was investigated in vivo by laser ablation inductively coupled plasma mass spectrometry and x-ray microfluorescence imaging. Preferential Cd accumulation in the pith and cortex was observed in stems of the Cd hyperaccumulating ecotype (HE), whereas Cd was restricted to the vascular bundles in its contrasting nonhyperaccumulating ecotype. Cd concentrations of up to 15,000/&MICRO;g g-1 were measured in the pith cells, which was many fold higher than the concentrations in the stem epidermis and vascular bundles in the HE plants. In the leaves of the HE, Cd was mainly localized to the mesophyll and vascular cells rather than the epidermis. The distribution pattern of Cd in both stems and leaves of the HE was very similar to calcium but not zinc, irrespective of Cd exposure levels. Extended x-ray absorption fine structure spectroscopy analysis showed that Cd in the stems and leaves of the HE was mainly associated with oxygen ligands, and a larger proportion (about 70% in leaves and 47% in stems) of Cd was bound with malic acid, which was the major organic acid in the shoots of the plants. These results indicate that a majority of Cd in HE accumulates in the parenchyma cells, especially in stems, and is likely associated with calcium pathways and bound with organic acid (malate), which is indicative of a critical role of vacuolar sequestration of Cd in the HE S. alfredii. [ABSTRACT FROM AUTHOR]

Background, aim and scope: Water quality impairment by heavy metal contamination is on the rise worldwide. Phytoremediation technology has been increasingly applied to remediate wastewater and stormwater polluted by heavy metals. Materials and methods: Laboratory analysis and field trials were conducted to evaluate the uptake of metals (Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn) by an aquatic plant, water lettuce ( Pistia stratiotes L.), and metal distribution in the plant. Results: The growth of water lettuce reduced Al, Fe, and Mn concentrations in water by >20%, K and Cu by >10%, and Ca, Mg, Zn, and Na to a lesser extent. A larger proportion of Ca, Cd, Co, Fe, Mg, Mn, and Zn was adsorbed or deposited on the external root surfaces while more Al, Cr, Cu, Ni, and Pb were absorbed and accumulated within the roots. Discussion: Water lettuce has a great ability in concentrating metals from its surrounding water with a concentration factor (CF) ≥10. The bio-concentration factor (BCF), which excludes the part on the root surfaces, is a more appropriate index than the CF for the differentiation of hyperaccumulation, accumulation, or non-accumulation plants for metals. Conclusions: Water lettuce is a hyperaccumulator for Cr, Cu, Fe, Mn, Ni, Pb, and Zn and can be applied for the remediation of surface waters. Recommendations and perspectives: Further study on the bioavailability of metals in the water lettuce is needed for the beneficial use of metal-enriched plant biomass. [ABSTRACT FROM AUTHOR]

Purpose: Copper is a trace element of environmental concern. Repeated applications of Cu-containing fungicides have resulted in a large scale of Cu contamination in agricultural soils. However, limited information is available regarding Cu accumulation and availability in soils under citrus production in the Indian River Area, South Florida, which has received increasing amounts of Cu fungicides to control canker and other diseases. The purpose of this study was to investigate Cu transformation, availability, and mobility in soils as affected by external Cu loading and soil properties. Materials and methods: Soil samples ( n = 18) were collected from representative commercial citrus groves in the Indian River area. These samples were characterized to understand the accumulation, availability to plant, and leaching loss, as influenced by soil properties, agricultural practices, and Cu fungicide inputs. Results and discussion: Significant accumulation and increased availability and mobility of Cu occurred in the soils with increasing citrus production period. Soil acidification enhanced Cu leaching in soil profiles. Available Cu estimated by Mehlich-3 or NHOAc extraction was highly correlated with total recoverable Cu, whereas the relationship between CaCl-extractable Cu and total recoverable Cu was affected by soil pH, with a greater slope of the relationship curve at soil pH < 6.5. Vertical movement of Cu in a soil profile was more pronounced at pH < 6.5. A large portion of soil Cu was present as organically bound, ranging from 43% to 62%, which was significantly correlated with both recoverable Cu and Mehlich-3-extractable Cu ( P < 0.001). Conclusions: Significant accumulation of Cu occurred in citrus grove soils due to anthropogenic inputs, and the availability and mobility of Cu in the soils were related to Cu accumulation and soil pH. Copper migration from Cu-contaminated soils to the environment was reduced when soil pH was 6.5 or higher. [ABSTRACT FROM AUTHOR]

Long-term use of Cu-containing fungicides in citrus groves has resulted in Cu buildup in the soil, but the effects of Cu contamination on microbial properties of citrus grove soils remain poorly understood. The objective of this study was to investigate the influence of long-term application of Cu-containing fungicides on microbial biomass, and bacterial community structure and diversity in five representative commercial citrus groves (5, 21, 27, 36, and 43 yr of planting history, respectively) soils, with one adjacent pasture soil as a reference. With increasing planting time of citrus, Cu concentrations in the soils increased, while microbiological properties including microbial biomass carbon (Cmic), microbial quotient (MQ), and the diversity of operational taxonomic units based on denaturing gradient gel electrophoresis (DGGE) community fingerprinting decreased. Stepwise multiple regression analysis showed that Cmic, microbial quotient, and bacterial community diversity were affected by Cu concentration and other soil properties such as total N and available P, but the effect of Cu was dominant. These results indicate that long-term application of Cu-containing fungicides has adverse effects on microbial biomass and bacterial community diversity in citrus grove soils. Sequencing of partial 16S rRNA gene fragments revealed that a shift of total bacterial community composition occurred as a result of Cu contamination, and the soils of more severely Cu-polluted citrus groves were dominated by bacteria g-Proteobacterium, Acidobacteria, Firmicutes, and b-Proteobacterium, whereas certain strains of s-Proteobacterium, g-Proteobacterium, Firmicutes, and Cyanobacteria were the dominant bacteria in the young citrus grove soils. [ABSTRACT FROM AUTHOR]

Lead (Pb), zinc (Zn), copper (Cu), and cadmium (Cd) often seriously deteriorate water quality. Spatial and temporal fluctuations of the metal concentrations in the Ten Mile Creek (Florida) (TMC) were monitored on a weekly basis at 7 sampling sites, from June 2005 to September 2007. River sediment samples were also collected from these sites in April, June, and October 2006 and January 2007, and analyzed for water, Mehlich 1 (M1), and Mehlich 3 (M3)-extractable metals (Mehlich, 1953, 1984), to examine the role of sediments as sources or sinks of the metals. The concentrations of lead, zinc, copper, and cadmium in the water samples were

Use of biosolids in agriculture to improve crop production and soil quality have created concerns due to content of heavy metals that may affect surface or ground water quality. A column leaching study was conducted to evaluate the leaching potential of copper (Cu), lead (Pb), zinc (Zn), cdmium (Cd), cobalt (Co), chromium (Cr), and nickel (Ni) from two typical agricultural sandy soils in South Florida (Spodosol and Alfisol) with increasing application of pelletized biosolids (called PB) at the rates of 0, 1.25, 5.0, 10.0 g kg-1, respectively together with chemical fertilizer (CF). Elevated PB rate resulted in reduced leaching loss of Cu, Pb, Zn, Cd, Co, Ni from Spodosol, but resulted in increased loss of Pb, Zn, Cd, and Co from Alfisol. Significant reduction in Cu loss occurred in both soils, which can be attributed to the strong binding of Cu with organic matter from the applied PB. Percentage of Cd loss as of total Cd was 13% - 41%, the highest in all the heavy metals, whereas loss of Pb as of total Pb was less than 6.6%, though the concentrations of Pb, Cd, Co, and Ni in leachate were mostly above the limits of U.S. EPA drinking water standards or the national secondary drinking water standards. These results indicate that soil properties, PB application rates, and chemical behavior of elements jointly influence the leachate total loads of heavy metals in sandy soils applied with biosolids. Application of CF together with BP at a rate higher than 10.0 g kg-1 for sandy soils may pose potential threats to water quality due to enhanced leachate loads of Cr and Ni in Spodosol and Pb, Zn, Cd, Co and Ni in Alfisol. [ABSTRACT FROM AUTHOR]

Water quality throughout south Florida has been a major concern for many years. Nutrient enrichment in the Indian River Lagoon (IRL) is a major surface water issue and is suggested as a possible cause of symptoms of ecological degradation. In 2005–06, water samples were collected weekly from seven sites along Ten Mile Creek (TMC), which drains into the Indian River Lagoon, to investigate and analyze spatial and temporal fluctuations of nutrients nitrogen (N) and phosphorus (P). The objective of this study was to understand the relationships among chlorophyll a concentration, nutrient enrichment and hydrological parameters in the surface water body.High median concentrations of total P (TP, 0.272 mg L−1), PO4-P (0.122 mg L−1), and dissolved total P (DTP, 0.179 mg L−1); and total N (TN, 0.988 mg L−1), NO3−-N (0.104 mg L−1), NH4+-N (0.103 mg L−1), and total Kjeldahl N (TKN, 0.829 mg L−1), were measured in TMC. The concentrations of TP, PO4-P, DTP, TN, NO3−-N, NH4+-N, and TKN were higher in summer and fall than in winter and spring. However, chlorophyll a and pheophytin concentrations during this period in TMC varied in the range of 0.000–60.7 and 0.000–17.4 μg L−1, with their median values of 3.54 and 3.02 μg L−1, respectively. The greatest mean chlorophyll a (10.3 μg L−1) and pheophytin (5.71 μg L−1) concentrations occurred in spring, while the lowest chlorophyll a (1.49 μg L−1) and pheophytin (1.97 μg L−1) in fall. High concentrations of PO4-P (>0.16 mg L−1), DTP (>0.24 mg L−1), NO3−-N (>0.15 mg L−1), NH4+-N (>0.12 mg L−1), and TKN (>0.96 mg L−1), occurred in the upstream of TMC, while high concentrations of chlorophyll a (>6.8 μg L−l) and pheophytin (>3.9 μg L−l) were detected in the downstream of TMC. The highest chlorophyll a (11.8 μg L−l) and pheophytin (6.06 μg L−l) concentrations, however, were associated with static and open water conditions. Hydrological parameters (total dissolved solid, electrical conductivity, salinity, pH, and water temperature) were positively correlated with chlorophyll a and pheophytin concentrations (P < 0.01) and these factors overshadowed the relationships between N and P concentrations and chlorophyll a under field conditions. Principal component analysis and the ratios of DIN/DP and TN/TP in the water suggest that N is the limiting nutrient factor for phytoplankton growth in the TMC and elevated N relative to P is beneficial to the growth of phytoplankton, which is supported by laboratory culture experiments under controlled conditions. [ABSTRACT FROM AUTHOR]

The relationship of zinc (Zn) efficiency in rice to differential tolerance of photosynthetic capacity and chloroplast function to low Zn stress was studied using Zn-efficient (IR8192) and Zn-inefficient (Erjiufeng) rice genotypes ( Oryza sativa L.). Zinc deficiency caused extensive declines in leaf chlorophyll (Chl) content, ratios of chl a:b, Pn, Fv/Fm and Fv/Fo, indicating that the intrinsic quantum efficiency of the photosystem II (PSII) units was damaged. A greater decline was observed in the inefficient genotype (Erjiufeng) than the efficient genotype (IR8192). The 77 K chl fluorescence emission spectrum revealed that Zn deficiency blocked energy spillover from PSII to PSI and more excitation energy was distributed to PSII in IR8192 than Erjiufeng. The spectrum of Zn-deficient Erjiufeng was completely disordered, implying that the photosynthetic centers were seriously damaged. Electron microscopy showed that Zn deficiency caused a severe damage to the fine structure of chloroplasts, but IR8192 had a better preserved chloroplast ultrastructure as compared with Erjiufeng. These differences may result from the higher levels of the antioxidant enzyme activities and lower oxidant stress level in IR8192. These results indicate that Zn deficiency decreases leaf photosynthetic capacity primarily by reducing the number of PSII units per unit leaf area, and also reducing the photochemical capacity of the remaining PSII units. Therefore, the maintenance of more efficient photochemical capacity under low Zn stress is a key factor for the high Zn efficiency in rice, which may result from less antioxidant damage caused by low Zn to the chloroplast ultrastructure. [ABSTRACT FROM AUTHOR]

Sedum alfredii Hance can accumulate Zn in shoots over 2%. Leaf and stem Zn concentrations of the hyperaccumulating ecotype (HE) were 24- and 28-fold higher, respectively, than those of the nonhyperaccumulating ecotype (NHE), whereas 1.4-fold more Zn was accumulated in the roots of the NHE. Approximately 2.7-fold more Zn was stored in the root vacuoles of the NHE, and thus became unavailable for loading into the xylem and subsequent translocation to shoot. Long-term efflux of absorbed 65Zn indicated that 65Zn activity was 6.8-fold higher in shoots but 3.7-fold lower in roots of the HE. At lower Zn levels (10 and 100 μM), there were no significant differences in 65Zn uptake by leaf sections and intact leaf protoplasts between the two ecotypes except that 1.5-fold more 65Zn was accumulated in leaf sections of the HE than in those of the NHE after exposure to 100 μM for 48 h. At 1,000 μM Zn, however, approximately 2.1-fold more Zn was taken up by the HE leaf sections and 1.5-fold more 65Zn taken up by the HE protoplasts as compared to the NHE at exposure times >16 h and >10 min, respectively. Treatments with carbonyl cyanide m-chlorophenylhydrazone (CCCP) or ruptured protoplasts strongly inhibited 65Zn uptake into leaf protoplasts for both ecotypes. Citric acid and Val concentrations in leaves and stems significantly increased for the HE, but decreased or had minimal changes for the NHE in response to raised Zn levels. These results indicate that altered Zn transport across tonoplast in the root and stimulated Zn uptake in the leaf cells are the major mechanisms involved in the strong Zn hyperaccumulation observed in S. alfredii H. [ABSTRACT FROM AUTHOR]

Cocoa has experienced significant growth in recent years in Peru and the presence of heavy metals in the soils of these plantations is a potential problem for the export of this product. The objective of the present study was to determine the total concentrations of heavy metals (Cd, Ni, Pb, Fe, Cu, Zn, Mn) in soils with cacao crops in the main productive areas in Peru: North (Tumbes, Piura, Cajamarca and Amazonas), Center (San Martin, Huánuco and Junín) and South (Cuzco). Contents of heavy metals in soils of cocoa plantations from 10 to 15 years old were evaluated. Physical (texture) and chemical (pH, organic matter, CEC, P, K, Ca, Mg, Al, Cd, Ni, Pb, Fe, Cu, Zn, Mn) analyzes were conducted in the soils. The results show favorable growing conditions for cocoa. The values found for heavy metals were below those considered as phytotoxic. Mean values of total Fe, Zn, Mn, Ni and Pb were higher in the southern region while in the northern region the values of Cu and Cd were higher. In general, pH, % of Clay and Mg were the variables that had higher significant correlations with heavy metals. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the feasibility of using floating beds of tall fescue plants (Festuca arundinacea) inoculated with denitrifying polyphosphate accumulating microorganisms (DPAOs). In the presences of DPAOs, tall fescue showed greater removal of NH4 +-N, NO3--N, total N (TN), and orthophosphate (ortho-P) after a 20-day treatment. The average removal rates were 86.32%, 93.60%, 90.12%, 72.09%, and 84.29%, respectively, for NH4 +-N, NO3--N, TN, total P (TP), and ortho-P. Tall fescue plants grew well on the floating beds and the average growth rate was approximately 5.4 g DM m-2·d-1. Tall fescue plants, being rich in crude potein, Ca, Mg, Fe, and Mn, can meet the daily feed requirements of livestock and poultry and were found safe to be used as animal feed. [ABSTRACT FROM AUTHOR]