Survey of heavy metal pollution and assessment of agricultural soil in Yangzhong district, Jiangsu Province, China

We investigated concentrations of Hg, Cd, Pb, Zn, Cu, As, Ni, and Cr in samples of soil, cereal, and vegetables from Yangzhong district, China. Compared to subsoils, the sampled topsoils are enriched in Hg, Cd, Cu, Pb, Zn, and As. High levels of Cd and Hg are observed in most agricultural soils. Concentrations of Cr and Ni show little spatial variation, and high Cu, Pb, and Zn contents correspond well to areas of urban development. High As contents are primarily recorded at the two ends of the sampled alluvion. The contents of Cd, Hg, and total organic carbon (TOC) increase gradually to maximum values in the upper parts of soil profiles, while Cr and Ni occur in low concentrations within sampled profiles. As, Pb, Cu, and Zn show patterns of slight enrichment within the surface layer. Compared to data obtained in 1990, Cd and Hg show increased concentrations in 2005; this is attributed to the long-term use of agrochemicals. Cr and Ni contents remained steady over this interval because they are derived from the weathering of parent material and subsequent pedogenesis. The measured As, Cu, Pb, and Zn contents show slight increases over time due to atmospheric deposition of material sourced from urban anthropogenic activity. Low concentrations of heavy metals are recorded in vegetables and cereals because the subalkaline environment of the soil limits their mobility. Although the heavy metal concentrations measured in this study do not pose a serious health risk, they do affect the quality of agricultural products.     

Bioremediation of kerosene I: A case study in liquid media

The ability of different local isolates in addition to some isolates from Germany to degrade kerosene in liquid medium was studied. The results showed that the percent of kerosene degradation varied among the different organisms and that 59–94% of kerosene was degraded after 21 d. Two local isolates (Pseudomonas sp. AP and Pseudomonas sp. CK) and one German isolate (Gordonia sp. DM) were selected for this study. The addition of wheat bran, as co-substrate, stimulated the kerosene degradation by the two local strains, while glucose inhibited the degradation rate using the three organisms with different rates. Ammonium nitrate and urea was the best nitrogen sources. The use of superphosphate (as phosphorus source) in the presence of urea stimulates the degradation rate. It was also observed that the addition of 1% surfactants, like Triton X-100, Igepal, Tergitol, or Tween 20 and 80 enhanced the kerosene degradation. The degradation percent lied between 94% and 98%. The ability of the tested organisms to degrade kerosene concentration from 2% to 8% was evaluated. It was found that the three organisms degraded about 65–85% from 8% kerosene after 21 d. The use of rice straw-immobilized cells reduced the time of degradation and enhanced the degradation ability of the organisms. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed the presence of a common protein band when the tested organisms were grown on kerosene.     

Modified Fenton reaction for trichlorophenol dechlorination by enzymatically generated H2O2 and gluconic acid chelate

Glucose oxidase is a well-known enzyme that catalyzes the oxidation of β-d-glucose to produce gluconic acid and hydrogen peroxide. Fenton reaction is a powerful oxidation technology used for the oxidation of groundwater pollutants. For the application of Fenton reaction in groundwater remediation, successful operation of Fenton reaction near neutral pH, and on-site generation of both H₂O₂ and chelate will be beneficial. The focus of this experimental study was to couple the glucose oxidation reaction with chelate-based Fenton reaction. The idea was to use the hydrogen peroxide and chelate gluconic acid generated during glucose oxidation for the dechlorination of 2,4,6-trichlorophenol (TCP) by Fenton reaction. The oxidation of glucose was achieved using the enzyme in free and immobilized forms. The rate of production of hydrogen peroxide was determined for each system, and was used to estimate the time required for complete consumption of glucose during the process, thus avoiding any traces of glucose in the Fenton reaction. In the case of free enzyme reaction, separation of the enzyme was achieved using an ultrafiltration membrane before initiating the Fenton reaction. The oxidation of TCP by Fenton reaction was performed at varying ratios of gluconic acid/Fe, and its effect on the decomposition of TCP and H₂O₂ was studied. TCP degradation was studied both in terms of parent compound degradation and free chloride generation.     

Risk assessment of trace elements in the stomach contents of Indo-Pacific Humpback Dolphins and Finless Porpoises in Hong Kong waters

The potential health risks due to inorganic substances, mainly metals, was evaluated for the two resident marine mammals in Hong Kong, the Indo-Pacific Humpback Dolphin (Sousa chinensis) and the Finless Porpoise (Neophocaena phocaenoides). The stomachs from the carcasses of twelve stranded dolphins and fifteen stranded porpoises were collected and the contents examined. Concentrations of thirteen trace elements (Ag, As, Cd, Co, Cr, Cs, Cu, Hg, Mn, Ni, Se, V and Zn) were determined by inductively coupled plasma mass spectrometer (ICP-MS). An assessment of risks of adverse effects was undertaken using two toxicity guideline values, namely the Reference Dose (RfD), commonly used in human health risk assessment, and the Toxicity Reference Value (TRV), based on terrestrial mammal data. The levels of trace metals in stomach contents of dolphins and porpoises were found to be similar. Risk quotients (RQ) calculated for the trace elements showed that risks to the dolphins and porpoises were generally low and within safe limits using the values based on the TRV, which are less conservative than those based on the RfD values. Using the RfD-based values the risks associated with arsenic, cadmium, chromium, copper, nickel and mercury were comparatively higher. The highest RQ was associated with arsenic, however, most of the arsenic in marine organisms should be in the non-toxic organic form, and thus the calculated risk is likely to be overestimated.     

Microbial degradation and impact of Bracken toxin ptaquiloside on microbial communities in soil

The carcinogenic and toxic ptaquiloside (PTA) is a major secondary metabolite in Bracken fern (Pteridium aquilinum (L.) Kuhn) and was hypothesized to influence microbial communities in soil below Bracken stands. Soil and Bracken tissue were sampled at field sites in Denmark (DK) and New Zealand (NZ). PTA contents of 2.1 +/- 0.5 mg g(-1) and 37.0 +/- 8.7 mg g(-1) tissue were measured in Bracken fronds from DK and NZ, respectively. In the two soils the PTA levels were similar (0-5 microg g(-1) soil); a decrease with depth could be discerned in the deeper B and C horizons of the DK soil (weak acid sandy Spodosol), but not in the NZ soil (weak acid loamy Entisol). In the DK soil PTA turnover was predominantly due to microbial degradation (biodegradation); chemical hydrolysis was occurring mainly in the uppermost A horizon where pH was very low (3.4). Microbial activity (basal respiration) and growth ([3H]leucine incorporation assay) increased after PTA exposure, indicating that the Bracken toxin served as a C substrate for the organotrophic microorganisms. On the other hand, there was no apparent impact of PTA on community size as measured by substrate-induced respiration or composition as indicated by community-level physiological profiles. Our results demonstrate that PTA stimulates microbial activity and that microorganisms play a predominant role for rapid PTA degradation in Bracken-impacted soils.     

Anaerobic inhibition and biodegradation of antibiotics in ISO test schemes

Municipal sewage is the main exposure route for antibiotics that are used in human medical care. Antibiotics that adsorb to the primary sludge and/or sur-plus activated sludge will enter the anaerobic digesters of municipal sewage treatment plants. Here anaerobic biodegradation or inhibition of anaerobic bacteria resulting in a disturbance of the process might occur. ISO standards 13641 (2003) and 11734 (1999) were used for assessing the anaerobic inhibition of 16 and the anaerobic biodegradability of 9 antibiotics respectively. Digestion sludge from a municipal sewage treatment plant (1g/l d.s.) was used as inoculum in both tests. In ISO 13641 (2003) most antibiotics showed only moderate inhibition effects after a 7 day incubation period, with EC50 values between 24 mg/l and more than 1000 mg/l (equal to mg/g d.s.). In contrast, metronidazol was decisively toxic to anaerobic bacteria with an EC50 of 0.7 mg/l. In the anaerobic degradation tests according to ISO standard 11734 (1995), only benzylpenicillin showed certain ultimate biodegradation after 60 days and most antibiotics inhibited the digesting sludge in the respective parallel tested inhibition controls. Thus the inhibition of anaerobic bacteria by antibiotics observed in the degradation tests was higher than expected from the results of the inhibition tests. The possible explanations are that distinct substrates are used (yeast extract versus sodium benzoate), that the digestion sludge loses activity during the washing steps performed for the degradation tests and that the exposure time in the degradation tests was 8 times longer than in the inhibition test.     

Investigation of a new approach to decompose two potent greenhouse gases: photoreduction of SF(6) and SF(5)CF(3) in the presence of acetone

In this paper, we addressed the utilization of photochemical method as an innovative technology for the destruction and removal of two potent greenhouse gases, SF(6) and SF(5)CF(3). The destruction and removal efficiency (DRE) of the process was determined as a function of excitation wavelength, irradiation time, initial ratio of acetone to SF(5)X (X represented F or CF(3)), initial SF(5)X concentration, additive oxygen and water vapor concentration. A complete removal was achieved by a radiation period of 55min and 120min for SF(6)-CH(3)COCH(3) system and SF(5)CF(3)-CH(3)COCH(3) system respectively under 184.9nm irradiation. Extra addition of water vapor can enhance DRE by approximately 6% points in both systems. Further studies with GC/MS and FT-IR proved that no hazardous products such as S(2)F(10), SO(2)F(2), SOF(2), SOF(4) were generated in this process.     

Municipal waste compost as an alternative to cattle manure for supplying potassium to lowland rice

The importance of the use of potassium in agriculture is increasing in South Asia for making most productive use of the nutrient in terms of economic returns. Nutrient supply traditionally by cattle manure is constrained by its insufficient availability. Municipal waste compost may be an alternative source of nutrient supplements. Field experiments were conducted at the Experimental Farm of Calcutta University, West Bengal, India during the wet seasons of 1997, 1998 and 1999 on flooded lowland rice. Potassium fractions in municipal waste compost and cattle manure were determined by sequential extraction and also the potassium uptake by rice to compare the effectiveness of municipal waste compost with traditional manure. Potassium was significantly bound to the organic matter in municipal waste compost. Potassium uptake by rice grain and straw increased significantly with the combined application of organics and fertilizers and it was higher in grain than in straw. Water-soluble and non-exchangeable potassium contents of municipal waste compost and cattle manure were highly correlated with the uptake of potassium by straw and grain. Exchangeable and residual potassium were also significantly correlated with the uptake of potassium by straw and grain of rice. Much higher uptake of K in rice straw and rain resulted from applying the manures in conjunction with fertilizers than when applied singly.     

Growth performance and biochemical responses of three rice (Oryza sativa L.) cultivars grown in fly-ash amended soil

The disposal of fly-ash (FA) from coal-fired power stations causes significant economic and environmental problems. Use of such contaminated sites for crop production and use of contaminated water for irrigation not only decreases crop productivity but also poses health hazards to humans due to accumulation of toxic metals in edible grains. In the present investigation, three rice cultivars viz., Saryu-52, Sabha-5204, and Pant-4 were grown in garden soil (GS, control) and various amendments (10%, 25%, 50%, 75% and 100%) of FA for a period of 90 days and effect on growth and productivity of plant was evaluated vis-a-vis metal accumulation in the plants. The toxicity of FA at higher concentration (50%) was reflected by the reduction in photosynthetic pigments, protein and growth parameters viz., plant height, root biomass, number of tillers, grain and straw weight. However, at lower concentrations (10-25%), FA enhanced growth of the plants as evident by the increase of studied growth parameters. The cysteine and non-protein thiol (NP-SH) content showed increase in their levels up to 100% FA as compared to control, however, maximum content was found at 25% FA in Saryu-52 and Pant-4 and at 50% FA in Sabha-5204. Accumulation of Fe, Si, Cu, Zn, Mn, Ni, Cd and As was investigated in roots, leaves and seeds of the plants. Fe accumulation was maximum in all the parts of plant followed by Si and both showed more translocation to leaves while Mn, Zn, Cu, Ni and Cd showed lower accumulation and most of the metal was confined to roots in all the three cultivars. As was accumulated only in leaves and was not found to be in detectable levels in roots and seeds. The metal accumulation order in three rice cultivars was Fe > Si > Mn > Zn > Ni > Cu > Cd > As in all the plant parts. The results showed that rice varieties Saryu-52 and Sabha-5204 were more tolerant and could show improved growth and yield in lower FA application doses as compared to Pant-4. Thus, Sabha-5204 and Saryu-52 are found suitable for cultivation in FA amended agricultural soils for better crop yields.