Heavy metal pollution in soils influences crop yield and quality, and metal accumulation in vegetables may pose a human health risk when consumed. Zinc (Zn), one of the heavy metals, is an essential ...element for plants, animals, and humans, but it is toxic at high levels. In this study, bioavailability of added Zn in a vegetable garden soil and critical Zn concentrations for phytotoxicity and potential dietary toxicity were determined for Chinese cabbage (Brassica chinensis L.), pakchoi (Brassica chinensis L.), and celery (Apiumg graveolens L.). Different Zn levels (0, 100, 200, 300, 400 mg kg(-1) soil, supplied as ZnSO4.7H2O) were added to the soil samples, based on Zn adsorption-desorption characteristics of the soil, the availability of added Zn in the soil decreased with time, with minimal change after 10-12 weeks of incubation. The results from sand and soil culture experiments showed that shoot growth was significantly inhibited at Zn concentrations above 25 mg L(-1) in nutrient solution or at DTPA-Zn above 170 mg kg(-1) in the soil. The sensitivity to Zn toxicity differed among the three vegetable crops, changing in the order: celery > Chinese cabbage > pakchoi. Zinc concentration in shoots and edible parts varied with Zn supply levels and type of the vegetables. Negative correlations were noted between Zn concentrations in shoots and dry matter yields (r = 0.90-0.98, P < 0.01), the critical Zn concentrations in plant tissues at 10% reduction of biomass yield (PT10) were 173.1, 167.5, 144.2 and 222.2 mg kg(-1) (DW) for Chinese cabbage, pakchoi, celery (stem) and celery (leaf), respectively. Zinc concentrations in the edible parts were positively correlated with available and total Zn in the soil (r = 0.91-0.99, P < 0.01). Based on the threshold of human dietary toxicity for Zn (20 mg kg(-1)), the critical concentrations of total and available Zn in the soil were 413 and 244 mg kg(-1) for Chinese cabbage, 224 and 75 mg kg(-1) for pakchoi, and 272 and 101 mg kg(-1) for celery, respectively. These results indicate that some vegetable species like pakchoi might accumulate Zn in edible parts over human dietary toxic threshold before the dry matter yield reduction was observed.
We characterized the effect of nitrogen (N) fertilizer on root morphology, photosynthetic pigments and cadmium (Cd) accumulation in a series of hydroponic experiments by using hyper-accumulating ...ecotype of Sedum alfredii H. (HE) and non-hyperaccumulating ecotype (NHE) plants. Cd accumulation in both ecotypes increased with increase of N levels until it reached the peak at 16 mM and then decreased suddenly. Among all the three N forms tested, ammonium sulfate (NH4)2SO4 was found to be an optimum choice. Based on these findings, a pot experiment was also conducted to evaluate the effect of three N fertilizers on phytoextraction from a slightly Cd-contaminated soil by the hyper-accumulating plant Sedum alfredii H.
Transport of phosphorus (P) through surface runoff from agriculture is suspected to contribute to the eutrophication of surface waters in South Florida and elsewhere. There is minimal quantitative ...information on the concentrations and loads of various P forms in surface runoff water on a field‐scale. The objective of this study was to evaluate the annual loads of various P forms in runoff water from citrus and vegetable crop production systems in sandy soil regions in Florida and their relations to soil P status, fertilizer P input, and environmental conditions. Eleven field sites (four on vegetable farms and seven in citrus groves) were selected for this monitoring study over a 2‐yr period. The concentrations of total P (TP) in the runoff water samples varied widely from 0.01 to 22.74 mg L−1, with approximately half of the samples having the TP over 1 mg L−1 Eighty‐three percent of the samples had orthophosphate (PO4–P) higher than 0.02 mg L−1 The mean proportion of total dissolved P (TDP) in the TP was higher than that of the total particulate P (TPP). The TDP constituted the major proportion of P in runoff water from most of the sites. The PO4–P accounted for approximately 64% of the TDP. The annual median concentrations of various P forms in the runoff water varied spatially and temporally and were correlated with total and labile P in the soils (water‐P, Olsen‐P, Mehlich 1‐P, and Mehlich 3‐P) as well as fertilizer P rate. The vegetable farms had higher concentrations of P in the runoff water than citrus groves due to their more severe soil erosion and higher fertilizer P input, which resulted in higher soil P accumulation and availability. The annual loads of TP, TDP, and PO4–P varied among the field sites and between the 2 yr. The TP loads were significantly correlated with soil labile P estimated by the four extraction procedures, but the Olsen‐P was best related to runoff P. Runoff P concentrations and the annual discharge rate accounted for 55 to 64% of the variance in the annual P loads. These results indicate that P transport through surface runoff from agriculture is affected by soil P status and water management, and merits attention in the development of best management practices.
Water quality of Lake Okeechobee has been a major environmental concern for many years. Transport of dissolved organic matter (DOM) in runoff water from watershed is critical to the increased inputs ...of nutrients (N and P) and metals (Cu and Zn). In this study, 124 soil samples were collected with varying soil types, land uses, and soil depths in Lake Okeechobee watershed and analyzed for water-extractable C, N, P, and metals to examine the relationship between dissolved organic carbon (DOC) and water soluble nutrients (N and P) and metals in the soils. DOC in the soils was in 27.64–400 mg kg
−1
(69.30 mg kg
−1
in average) and varied with soil types, land uses, and soil depth. The highest water-extractable DOC was found in soils collected in sugar cane and field crops (277 and 244 mg kg
−1
in average, respectively). Water soluble concentrations of N and P were in the range of 6.46–129 and 0.02–60.79 mg kg
−1
, respectively. The ratios of water-extractable C/N and C/P in soils were in 0.68–12.52 (3.23 in average) and 3.19–2,329 (216 in average), and varied with land uses. The lowest water-extractable C/N was observed in the soils from dairy (1.66), resident (1.79), and coniferous forest (4.49), whereas the lowest water-extractable C/P was with the land uses of dairy (13.1) and citrus (33.7). Therefore, N and P in the soils under these land uses may have high availability and leaching potential. The concentrations of water soluble Co, Cr, Cu, Ni, and Zn were in the ranges of < method detection limit (MDL)–0.33, <MDL–0.53, 0.04–2.42, <MDL–0.71, and 0.09–1.13 mg kg
−1
, with corresponding mean values of 0.02, 0.01, 0.50, 0.07, and 0.37 mg kg
−1
, respectively. The highest water soluble Co (0.10 mg kg
−1
), Cr (0.26 mg kg
−1
), Ni (0.31 mg kg
−1
), and Zn (0.80 mg kg
−1
) were observed in soils under the land use of sugar cane, whereas the highest Cu (1.50 mg kg
−1
) was with field crop. The concentration of DOC was positively correlated with total organic carbon (TOC) (
P
<0.01), water soluble N (
P
<0.01), electrical conductivity (EC,
P
<0.01), and water soluble Co, Cr, Ni, and Zn (
P
<0.01), and Cu (
P
<0.05), whereas water soluble N was positively correlated with water soluble P, Cu, and Zn (
P
<0.01) in soils. These results indicate that the transport of DOC from land to water bodies may correlate with the loss of macro-nutrients (N, P), micro-nutrients (Cu, Zn, and Ni), and contaminants (Cr and Co) as well.
•BPA was more uniformly distributed between roots, stems, and leaves in lettuce.•NP concentrations were highest at site of exposure for both crops.•BPA concentrations were highest at site of exposure ...in tomatoes only.•Estimated daily intake of BPA ranged from 8.9 to 62.9μg.•Estimated daily intake of NP ranged from 11.9 to 95.1μg.
The potential uptake and distribution of bisphenol A (BPA) and nonylphenol (NP) (from reclaimed irrigation water) in edible crops was investigated. BPA and NP were spiked into simulated reclaimed water at environmentally relevant concentrations. Two crops (lettuce, Lactuca sativa and tomato, Lycopersicon esculentum) were grown hydroponically in a greenhouse using the spiked irrigation water under two irrigation exposure scenarios (overhead foliar exposure and subsurface root exposure). BPA concentrations in tomato fruit were 26.6±5.8 (root exposure) and 18.3±3.5 (foliar exposure) μgkg−1, while concentrations in lettuce leaves were 80.6±23.1 (root exposure) and 128.9±17.4 (foliar exposure) μgkg−1. NP concentrations in tomato fruit were 46.1±6.6 (root exposure) and 24.6±6.4 (foliar exposure) μgkg−1, while concentrations in lettuce leaves were 144.1±9.2 (root exposure) and 195.0±16.9 (foliar exposure) μgkg−1. BPA was relatively mobile in lettuce plants regardless of exposure route. Limited mobility was observed for NP in both crops and BPA in tomatoes. The estimated daily intake of BPA and NP through consumption of vegetables irrigated with reclaimed water ranged from 8.9–62.9 to 11.9–95.1μg, respectively, depending on the exposure route.
The potential risk of surface and ground water contamination by phosphorus (P) and heavy metals leached from compost-based containerized media has become an environmental concern. Solubility and ...fractionation of P and heavy metals were evaluated in media containing 0, 25, 50, 75, or 100% compost derived from biosolids and yard trimmings for potential impacts on the environment. As compost proportion in peat-based media increased from 0 to 100%, concentrations of total P, Cd, Cu, Ni, Pb, Zn, and Mn in the media increased whereas concentrations of total Co and Cr decreased. Except for Cu, all heavy metals in the water-soluble fraction decreased with increasing compost proportion in the media, because of higher Fe, Al, and Ca concentrations and pH values of the composts than the peat. When the media pH is controlled and maintained at normal range of plant growth (5.5-6.5), leaching of the heavy metals is minimal. Incorporation of compost to the peat-based media also decreased the proportion of total P that was water-soluble. However, concentrations of bioavailable inorganic phosphorus (NaHCO3-IP), readily mineralizable organic phosphorus (NaHCO3-OP), potentially bioavailable inorganic phosphorus (NaOH-IP), and potentially bioavailable organic phosphorus (NaOH-OP) were still higher in the media amended with compost because of higher total P concentration in the compost. Further study is needed to verify if less or no topdressing of chemical P fertilizer should be applied to the compost-amended media to minimize P effect on the environment when compost-amended potting media are used for nursery or greenhouse crop production systems.
Increased anthropogenic inputs of Cu and Zn in soils have caused considerable concern relative to their effect on water contamination. Copper and Zn contents in surface soil directly influence the ...movement of Cu and Zn. However, minimal information is available on runoff losses of Cu and Zn in agricultural soils, and soil-extractable Cu and Zn in relation to runoff water quality. Field experiments were conducted in 2001 to study dissolved Cu and Zn losses in runoff in Florida sandy soils under commercial citrus and vegetable production and the relationship between soil-extractable Cu and Zn forms and dissolved Cu and Zn concentrations in runoff water. Five extraction methods were compared for extracting soil available Cu and Zn. Concentrations of dissolved Cu and Zn in runoff were measured and runoff discharge was monitored. Mean dissolved Cu in field runoff water was significantly correlated with the extractable Cu obtained only by 0.01 mol L−1 CaCl2, Mehlich 1, or DTPA–TEA methods. Dissolved Zn in runoff water was only significantly correlated with extractable Zn by 0.01 mol L−1 CaCl2 The highest correlations to dissolved Cu in runoff were obtained when soil-available Cu was extracted by 0.01 mol L−1 CaCl2 The results indicate that 0.01 mol L−1 CaCl2–extractable Cu and Zn are the best soil indexes for predicting readily released Cu and Zn in the sandy soils. Both runoff discharge and 0.01 mol L−1 CaCl2–extractable Cu and Zn levels had significant influences on Cu and Zn loads in surface runoff.
Growth of Bolivian sunset (
Gloxinia sylvatica (HBK) Wiehler), Brazilian plume (
Justicia carnea Lindl.), and golden globe (
Lysimachia congestiflora) transplants was evaluated in media containing ...25, 50, 75, or 100% compost (derived from biosolids and yard trimmings) as compared to commercial peat-based media. Compost-based media had higher pH, EC, bulk density, particle density and total porosity as compared to peat-based media. The effects of media composition on plant growth and development varied with each species tested.
Gloxinia generally were smaller with reduced flower development when grown in compost-based media as compared to peat-based media. However, regardless of media composition, plants were of high visual color and quality.
Justicia were similar in size or smaller when grown in compost-based media as compared to peat-based media but flower development was unaffected. However, the visual color and quality of the plants suffered when plants were grown in compost alone. Growth indexes of
Lysimachia were similar among media or slightly reduced by 12%. Although, flower development was reduced by 16% in the second trial, plants were still acceptable in terms of visual color and quality, regardless of media composition.
Silverleaf whitefly (SLW) (
Bemisia argentifolii Bellows and Perring) feeding on tomato (
Lycopersicon esculentum Mill.) plants induces a disorder in the fruit known as irregular ripening. The ...effects of silverleaf whitefly feeding on ripening of tomato fruit both attached to and detached from the plant are described. ‘Florida Petite’ tomatoes free of SLW, attached to the plant, began an ethylene climacteric between 40 and 45 days after anthesis (DAA), coincident with a rapid increase in red color and loss of firmness. The ethylene climacteric began between 45 and 50 DAA in tomato fruit from plants infested with SLW, and the fruit developed less red color and softened less than did fruit from plants free of SLW. Fruit harvested 45 DAA from plants free of SLW reached the respiratory and ethylene climacteric peak 3 days after harvest, developed normal red color, and softened similar to fruit ripened on the plant. In contrast, fruit harvested 45, 50 or 55 DAA from SLW-infested plants showed no respiratory or ethylene climacteric, had poor color development, and did not soften to the same extent as did fruit from plants free of SLW.
Bisphenol A (BPA), nonylphenol (NP), and steroidal estrogens in vegetables and fruits were analyzed using gas chromatography with tandem mass spectrometry (GC-MS/MS). Isotope dilution standards were ...spiked before the extraction to account for extraction inefficiency and loss of analytes during sample workup. Recoveries were >90% for all of the compounds in each matrix. The limit of detection (LOD) ranged from 0.03 to 0.3 μg kg–1, whereas the limit of quantitation (LOQ) ranged from 0.1 to 1.0 μg kg–1. All analytes can be monitored in a single GC-MS/MS run with a run time of 20 min. Occurrence of these endocrine-disrupting chemicals (EDCs) in vegetables and fruits from local markets was observed using the established analytical method. BPA was detected in all vegetable and fruit samples, ranging from 0.2 ± 0.1 to 9.0 ± 4.9 μg kg–1, indicating significant exposure potential for humans. NP was detected in pumpkin, sweet potato, citrus, and apple samples. The concentration of 4-n-NP ranged from 5.3 ± 2.4 to 18.9 ± 8.0 μg kg–1, whereas that of 4-NP ranged from 5.1 ± 2.6 to 12.2 ± 3.6 μg kg–1. Concentrations of 17-β-estradiol in vegetables and fruits ranged from 1.3 ± 0.4 to 2.2 ± 1.0 μg kg–1 except those in tomato and strawberry, in which no 17-β-estradiol was detected. The estimated daily intake of 17-β-estradiol was beyond the recommended acceptable daily intake (ADI) for children as recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA).
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