Soil Enzymatic Activities as Influenced by Lead and Nickel Concentrations in a Vertisol of Central India

A pot-culture was conducted in Completely Randomized Design with three replicates to study the effect of Pb and Ni on enzymatic activities in a Vertisols. Results indicated that increasing in the levels of Pb from 0, 100, 150 and 300 mg kg^?1 soil significantly reduced the dehydrogenase activity (DHA) 38.9, 32.1, 30.9, 18.1 µg triphenylformazan g^?1 soil 24 h^?1; acid phosphatase activities 73, 61, 58, 55 µg PNP g^?1 soil h^?1 and alkaline phosphatase activities 80.7, 69.4, 66.2 and 64.0 µg PNP g^?1 soil h^?1, respectively. Application of Ni up to 100 mg kg^?1 had significantly improved the soil enzymatic activities and thereafter there was no such change up to the highest level (300 mg Ni kg^?1). Among soil enzymatic activities, DHA was more sensitive to Pb application. The findings generated through this study can be useful for managing waste water for safe disposal as well as sustainable crop production.     

Horizontal and Vertical Distribution of Lead,Cadmium, and Zinc in Farmlands Around a Lead-Contaminated Goldmine in Zamfara,Northern Nigeria

This study was undertaken to evaluate the vertical and horizontal distribution of lead (Pb), cadmium (Cd), and zinc (Zn) in farmlands around a Pb-contaminated goldmine. Total concentrations of Pb and Cd recorded were at maximum values of 2,246.55 and 68.7 mg kg^?1, respectively; these are greater than the threshold values for Pb (300 mg kg^?1) and Cd (3 mg kg^?1). However, the concentration of Zn was within acceptable limits (300 mg kg^?1). Down the soil profile, concentrations of Pb, Cd, and Zn showed two peaks; these were attributed to facilitated transport and ground-water enrichment. Incubation of the soil samples with glucose indicated low microbial process(es), which could be due to the increased levels of Pb and Cd. Factor analysis showed a close association of Pb and Cd with the soil-exchange complex with a possibility of these heavy metals replacing Ca and other divalent cations in the soil-exchange site. This will, however, increase the risk of Pb and Cd leaching and uptake by plants. Although the metals were more associated with resistant soil fraction (sand), which also indicates their geogenic origin, chemical weathering under the influence of pH could release these metals into the soil-exchange site.     

Accumulation and Distribution Characteristics of Zinc and Cadmium in the Hyperaccumulator Plant Sedum plumbizincicola

Accumulation and distribution of Zn and Cd in the hyperaccumulator plant Sedum plumbizincicola were investigated in a hydroponic experiment. Mean Cd and Zn concentrations in shoots (7,010 and 18,400 mg kg^?1) were about sevenfold and fivefold higher than those in roots (840 and 3,000 mg kg^?1) after exposure to 100 μM CdSO₄ and 600 μM ZnSO₄, respectively. Cd and Zn concentrations in young leaves (4,330 and 9,820 mg kg^?1) were about sixfold and twofold higher than those in mature leaves (636 and 2,620 mg kg^?1), respectively. MicroPIXE analysis showed that Zn was predominantly localized in epidermal cells in both young and mature leaves, but large amounts of Zn occurred in mesophyll cells in young leaves. Leaf tissue fractionation showed that soluble and cell wall fractions were different at the two stages of leaf growth. Young and mature leaves of S. plumbizincicola also showed different accumulation and distribution characteristics for Zn and Cd.     

Tungsten (W) bioavailability in paddy rice soils and its accumulation in rice (Oryza sativa)

The aim of this study was to investigate the accumulation characteristics of tungsten (W) by different indica rice cultivars from the soil and to assess the potential risks to human health via dietary intake of W in rice consumption. A total of 153 rice (ear) samples of 15 cultivars and the corresponding surface soil samples were collected from 7 cities in Fujian Province of southeastern China. The available soil W were extracted using H₂C₂O₄·2H₂O-(NH₄)₂C₂O₄·H₂O at pH 3.3). Results showed that the total soil W ranged from 2.03 mg kg^?1 to 15.34 mg kg^?1 and available soil W ranged from 0.03 mg kg^?1 to 1.61 mg kg^?1. The W concentration in brown rice varied from 7 μg kg^?1 to 283 μg kg^?1 and was significantly correlated with the available soil W. The highest mean TF_avail (transfer factor based on available soil W) was 0.91 for Te-you 627 (hybrid, indica rice), whereas the lowest was 0.08 for Yi-you 673 (hybrid, indica rice). The TF_avail decreased with the increase in available soil W, clay content, and cation exchange capacity. The consumption of the brown rice produced from the investigated areas in some cultivars by the present study may cause risks to human health.     

Exposure Assessment to Glyphosate of Two Species of Annelids

Adult mortality, biomass, fecundity and viability of cocoons were studied in Eisenia fetida and Octolasion tyrtaeum, in response to glyphosate exposure in soil. Exposure tests were carried out following USEPA procedure, with five concentrations of glyphosate in soil and a control. O. tyrtaeum was more sensitive to the highest concentration of glyphosate (50,000 mg kg^?1), with 100 % mortality by day 7 of exposure, compared with 71 % for E. fetida. Although biomass of O. tyrtaeum was significantly different between the control and 5,000 mg kg^?1 dose at day 14, E. fetida was not affected at that concentration, and only showed a significant weight loss after 7 days of exposure to 50,000 mg kg^?1. Adverse effects upon adult fecundity and cocoon viability were observed at glyphosate concentrations of 5,000 mg kg^?1 and above. Adverse effects were observed at concentrations that greatly exceeded the recommended field application rates of glyphosate.     

Evaluation of the Persistence and Leaching Behaviour of Thiram Fungicide in Soil,Water and Oil Palm Leaves

The residual levels and persistence of thiram in the soil, water and oil palm seedling leaves were investigated under field conditions. The experimental plots were carried out on a clay loam soil and applied with three treatments namely; manufacturer’s recommended dosage (25.6 g a.i. plot^?1), manufacturer’s double recommended dosage (51.2 g a.i. plot^?1), and control (water) were applied. Thiram residues were detected in the soil from day 0 to day 3 in the range of 0.22–27.04 mg kg^?1. Low concentrations of thiram were observed in the water and leave samples in the range of 0.27–2.52 mg L^?1 and 1.34–12.28 mg kg^?1, respectively. Results have shown that thiram has a rapid degradation and has less persistence due to climatic factors. These findings suggest that thiram is safe when applied at manufacturer’s recommended dosage on oil palm seedlings due to low residual levels observed in soil and water bodies.     

Involvement of an Antioxidant Defense System in the Adaptive Response to Cadmium in Maize Seedlings (Zea mays L.)

Chemical and biological analyses were used to investigate the growth response and antioxidant defense mechanism of maize seedlings (Zea mays L.) grown in soils with 0–100 mg kg^?1 Cd. Results showed that maize seedlings have strong abilities to accumulate and tolerate high concentrations of Cd. For soil with 50 mg kg^?1 Cd, the Cd contents in roots and shoots of maize seedlings are as large as 295.6 and 153.0 mg kg^?1 DW, respectively, without visible symptoms of toxicity. Lower soil Cd concentrations lead to a decrease in reduced glutathione (GSH) content in leaves of maize seedlings, whereas higher soil Cd concentrations resulted in an increase in the activities of superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase. Maize seedlings have strong capacities to adapt to low concentrations of Cd by consuming GSH and to develop an antioxidative enzyme system to defend against high-Cd stress.     

Biodegradation of Imidacloprid by Consortium of Two Soil Isolated Bacillus sp.

Imidacloprid degradation potential of bacterial cultures from sugarcane growing soils was studied in liquid culture and Bacillus aerophilus and Bacillus alkalinitrilicus showed maximum potential to degrade imidacloprid. Hence, into a clay loam soil imidacloprid was added at 50, 100, and 150 mg kg^?1 along with 45 × 10⁷ cells g^?1 soil of both species under autoclaved and unautoclaved conditions. Under autoclaved conditions imidacloprid residues were degraded after 56 days to 3.18, 5.83 and 10.48 mg kg^?1 and under unautoclaved conditions to 5.17, 6.23 and 10.31 mg kg^?1. 6-chloronicotinic acid, nitrosimine and imidacloprid-NTG metabolites were detected in measurable concentrations under both conditions. Dissipation pattern of imidacloprid did not follow first order kinetics under both sets of conditions. The half life value of imidacloprid ranged from 13 to 16 days after bacterial inoculation. This is first report of use of mixed culture of native soil bacterial isolates for remediation of imidacloprid contaminated soils.     

Ecotoxicity of Cr, Cd, and Pb on Two Mediterranean Soils

Three potentially toxic elements [chromium (Cr), lead (Pb), and cadmium (Cd)] were tested to assess their effects on two soils of different properties and origin. The soils were a granitic soil (Haplic Arenosol), which meets the requirements of OECD ecotoxicity testing, and a calcareous soil (Calcaric Regosol) with properties often found in the Mediterranean areas. The metal concentrations used ranged from 0.001 to 5,000 mg kg^?1 soil. The effects on soil microbial activity and community composition (respirometry and polymerase chain reaction–denaturing gradient gel electrophoresis analysis), as well as the effects on plant germination and elongation (Lactuca sativa), were assessed. The toxicity of the soil water extracts was also evaluated by the growth inhibition of algal populations (Pseudokirschneriella subcapitata). Cr showed the highest level of toxicity to soil organisms in the assays performed because this element remains in soil as anionic form and is less retained by the soil solid matrix than Cd and Pb. The lowest observed–adverse effect level for Cr ranged from approximately 0.1 mg kg^?1 [substrate induced respiration (SIR) test for the granitic soil] to 10 mg kg^?1 (basal respiration and SIR tests for the calcareous soil). For Pb (SIR) and Cd (SIR and alga tests), these levels were approximately 100 mg kg^?1. Germination and algal tests showed higher sensitivity in Regosol soil than in Arenosol soil for Cr due to differences in the bioavailability between the soils. In the cases or areas where alkaline soils are abundant, these should also be considered in laboratory ecotoxicity testing to avoid underestimation of ecotoxicological risks.     

Persistence and Dissipation of Quinalphos in/on Cauliflower and Soil Under the Semi Arid Climatic Conditions of Karnataka, India

Persistence and dissipation of quinalphos residues in/on cauliflower was studied after giving spray applications at 2 concentrations, i.e. recommended dose of 500 g a.i. ha^?1 and double the recommended dose of 1,000 g a.i. ha^?1. Residue analysis of cauliflower curds was carried out after the third spray over a period of 15 days. Initial residues of quinalphos on cauliflower from the two treatments were 1.19 and 1.842 mg kg^?1. The residues persisted up to 15 days from both the treatments. The residues of quinalphos dissipated from both treatments with the half-life of 4.8 and 5.3 days. Based on the persistence study and maximum residue limit value of 0.05 mg kg^?1 the safe pre-harvest interval was worked out as 17 and 22 days from treatment at the recommended and double the recommended dose, respectively. Analysis of soil samples was carried out on the 15th day of sampling and residues were found to be 0.013 and 0.044 mg kg^?1.     

Effects of Complex Pollution of Pb and B[a]P on the Growth and Physiological and Biochemical Indexes of Ryegrass

Effects of complex pollution of Pb and B[a]P on the growth and physiological and biochemical indexes of ryegrass were investigated in a potted soil. The results showed that under single Pb treatment condition, low-concentration (0–100 mg kg^?1) Pb stimulated the increase of ryegrass biomass while high-concentration (200–400 mg kg^?1) Pb obviously inhibited ryegrass growth. Under single B[a]P pollution condition, low-concentration (0–30 mg kg^?1) B[a]P facilitated the growth of ryegrass while high-concentration (50–100 mg kg^?1) B[a]P had toxic effect on ryegrass. Under joint impacts of Pb and B[a]P at low concentrations, biomass, chlorophyll content and carotenoid content as well as POD and CAT activities of ryegrass presented firstly rising and then descending trends, SOD accumulation increased slightly and MDA didn’t experience obvious change. Under co-existence of Pb and B[a]P, Pb was the main toxic factor for ryegrass growth and it controlled the variation trend of whole growth cycle of ryegrass.     

Modelling the Long-Term Fate of Mercury in a Lowland Tidal River. II. Calibration and Comparison of Two Models with Field Data

This study presents results of the application of two-one-dimensional/dynamic-deterministic models developed to evaluate and predict mercury contamination of a lowland river, the River Yare, Norfolk, UK. As a general indication of model performance, MODEL 1 produced a prediction of the overall mass balance of mercury in the River Yare that was 6% lower than an estimate, based on measurements, and 10% lower than the prediction provided by MODEL 2. The mercury surficial sediment concentrations calculated by MODEL 1 varied from 0.46 mg kg^?1 in 1995 (Reach 3) to 3.55 mg kg^?1 in 1986 (Reaches 6 and 7), whereas the minimum mercury concentration calculated by MODEL 2 was 0.42 mg kg^?1 in 1995 (Reach 3) and the maximum was 8.45 mg kg^?1 in 1986 (Reach 5). Average mercury concentrations experimentally measured in surficial sediments ranged from 0.47 mg kg^?1 in 1995 (Reach 3) to 8.10 mg kg^?1 in 1986 (Reach 6). MODEL 2 gave an excellent prediction of mercury in fish flesh compared with the results obtained from the actual analysis of fish flesh. Both models demonstrated good ability to simulate actual values determined for all compartments, water, surficial sediments, bottom sediments, and fish.     

Degradation Dynamics of Emamectin Benzoate on Cabbage Under Subtropical Conditions of Punjab, India

Emamectin benzoate (Proclaim 5 SG) was applied to cabbage at 8.5 and 17 g a.i. ha^?1, during the head initiation stage. A high performance liquid chromatography (HPLC) analytical method, for the determination of emamectin benzoate in cabbage, was developed. Average recoveries of emamectin benzoate ranged from 92 % to 96 % at different fortification levels (0.05, 0.25 and 0.50 mg kg^?1). The initial deposits, 0.11 and 0.21 mg kg^?1 of emamectin benzoate at 8.5 and 17 g a.i. ha^?1, dissipated below the determination limit of 0.05 mg kg^?1 in 3 and 5 days, respectively.     

Metal Pollution (Cd,Pb, Zn,and As) in Agricultural Soils and Soybean,Glycine max,in Southern China

Crops produced on metal-polluted agricultural soils may lead to chronic toxicity to humans via the food chain. To assess metal pollution in agricultural soils and soybean in southern China, 30 soybean grain samples and 17 soybean-field soil samples were collected from 17 sites in southern China, and metal concentrations of samples were analyzed by graphite furnace atomic absorption spectrophotometer. The integrated pollution index was used to evaluate if the samples were contaminated by Cd, Pb, Zn and As. Results showed that Cd concentration of 12 samples, Pb concentration of 2 samples, Zn concentration of 2 samples, and As concentrations of 2 samples were above the maximum permissible levels in soils. The integrated pollution index indicated that 11 of 17 soil samples were polluted by metals. Metal concentrations in soybean grain samples ranged from 0.11 to 0.91 mg kg^?1 for Cd; 0.34 to 2.83 mg kg^?1 for Pb; 42 to 88 mg kg^?1 for Zn; and 0.26 to 5.07 mg kg^?1 for As, which means all 30 soybean grain samples were polluted by Pb, Pb/Cd, Cd/Pb/As or Pb/As. Taken together, our study provides evidence that metal pollution is an important concern in agricultural soils and soybeans in southern China.     

Toxicological Responses of the Earthworm Eisenia fetida to 18-Crown-6 Under Laboratory Conditions

The earthworm Eisenia fetida was exposed to artificial soil supplemented with 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) to investigate its effects on earthworm mortality, growth, avoidance, burrowing behavior and respiration. The results revealed that 18-crown-6 had the potential to negatively affect the behavior of earthworms. The 7-d LC₅₀ was 585 mg kg^?1 soil. Avoidance behavior was the most sensitive endpoint, with a 48-h EC₅₀ of 120 mg kg^?1 soil. Growth, burrow length and respiration showed general decreases with increasing 18-crown-6 concentrations. Behavioral endpoints and respiration may be regarded as sensitive parameters in evaluating the toxicity of this chemical to earthworms.     

Identification of Heavy Metal Pollution Derived From Traffic in Roadside Soil Using Magnetic Susceptibility

The study integrates surface and vertical distribution of magnetic susceptibility and heavy metal contents (Pb, Cu, Zn and Fe) to characterize the signature of vehicle pollutants in roadside soils at Linfen city, China. Sites with reforestation and without vegetation cover were investigated. The results showed that magnetic susceptibility and heavy metal contents were higher at the roadside without trees than in the reforest belt. The variations of magnetic susceptibility and heavy metal contents decreased both with distance and with depth. The maximum value was observed at 5–10 m away from the roadside edge. The vertical distribution in soil revealed accumulation of pollutants in 0–5 cm topsoils. The average contents were higher than the background values and in the order Fe (107.21 g kg^?1), Zn (99.72 mg kg^?1), Pb (90.99 mg kg^?1), Cu (36.14 mg kg^?1). Coarse multi domain grains were identified as the dominating magnetic particles. Multivariate statistical and SEM/EDX analyses suggested that the heavy metals derived from traffic sources. Trees act as efficient receptors and green barrier, which can reduce vehicle derived pollution.     

Persistence and Metabolism of Fipronil in Sugarcane Leaves and Juice

Fipronil gives effective control of early shoot borer and termites in sugarcane. The persistence and metabolism of fipronil in sugarcane leaves and juice were studied following application of fipronil (Regent 0.3 G) at 75 and 300 g a.i. ha^?1. Samples of sugarcane leaves were collected at various time intervals. Samples of sugarcane juice were collected at harvest. Residues of fipronil and its metabolites were quantified by gas liquid chromatograph. The limit of quantification of fipronil and its metabolites was 0.01 mg kg^?1 for sugarcane leaves and juice. Total residues of fipronil and its metabolites in sugarcane leaves after 7 days of its application at 75 and 300 g a.i. ha^?1 were 0.26 and 0.66 mg kg^?1, respectively. Residues could not be detected after 60 and 90 following fipronil application at either concentration. In sugarcane leaves, fipronil was found to be the main constituent, followed by its metabolites amide, desulfinyl, sulfone and sulfide. Samples of sugarcane juice did not reveal the presence of fipronil or its metabolites following its application at both the dosages at harvest.     

Persistence Behavior of Imidacloprid and Carbosulfan in Mango (Mangifera indica L.)

Imidacloprid was sprayed on mango cv. Dashehari at 0.3 mL L^?1 of water during pre-bloom stage with 6–8 cm panicle size (first week of March) to control hopper and carbosulfan was sprayed at 2.0 mL L^?1 of water in the trees of mango hybrid (H-1000) during fruit development stage (first week of May) to control leaf webber. Residues of both the insecticides were analysed in peel, pulp and fruit at different stages of fruit development and maturity. The initial residues of imidacloprid, after 30 days of spraying, were 1.21, 0.56 and 1.77 mg kg^?1 in peel, pulp and whole fruit, respectively. The residues persisted in peel for 60 days and in pulp for 50 days and dissipated with a half-life of 38 days. Mature Dashehari fruits at harvest (after 85 days of spraying) were free from imidacloprid residues. Carbosulfan in mango peel dissipated from 5.30 mg kg^?1 (after 1 h of spraying) to 0.05 mg kg^?1 at the time of harvest (after 45 days of spraying). Carbosulfan residue in pulp was very low (0.08 mg kg^?1) after 1 h of spraying, which increased gradually to 0.90 mg kg^?1 after 10 days and finally came down to 0.04 mg kg^?1 after 26 days of spraying. The insecticide residue was not detected in the pulp at the time of harvest. The residues persisted in pulp for 26 days and in peel for 45 days and degraded with a half-life of 7 days. The dissipation of both imidacloprid and carbosulfan followed first order rate kinetics in whole fruit (peel + pulp). Therefore, the safe pre-harvest intervals were suggested to be 55 days for imidacloprid and 46 days for carbosulfan before consumption of mango fruits after spraying of these insecticides.     

Dissipation and Dynamics of Mesotrione in Maize and Soil Under Field Ecosystem

Modified QuEChERS-HLPC (quick, easy, cheap, effective, rugged and safe) methods for the analysis of mesotrione in maize and soil were developed and validated. At three fortification levels of 0.01, 0.1 and 0.5 mg kg^?1 mesotrione, the recoveries of mesotrione in maize plants, maize and soil were in the range of 85.95 %–96.05 %, with relative standard deviations (RSD) of 2.89 %–9.83 %. The limit of quantification (LOQ) of method was 0.001 mg kg^?1 for maize and soil. In the supervised field trials, the degradation rates of mesotrione were described using first-order kinetics and mesotrione dissipation in maize plants coincided with C _t  = 1.735e^?1.0194t with the half-life 3.94 days in Tianjin, and C _t  = 4.9536e^?0.7237t with the half-life 5.10 days in Jilin. As for soil, C _t  = 20.272e^?1.208t with the half-life 2.98 days in Tianjin, and C _t  = 5.5835e^?8141t with the half-life 4.49 days in Jilin. At pre-harvest interval (PHI) of 0 and 20 days, the final residue levels of mesotrione could not be detected in maize and soil at the recommended dosage and 1.5 times recommended dosage.