摘要：
Background. Methyl tertiary butyl ether (MTBE) is the second most highly produced industrial chemical in the US and a frequent groundwater pollutant. At the same time, MTBE is quite persistent to biotic and abiotic decomposition. The goal of this study was to find plant species that could degrade MTBE and might be used in phytoremediation. Methods. Excised roots and leaves (0.3 g) from more than 24 Danish plant species out of 15 families were kept in glass vessels with 25 ml spiked aqueous solution for 2 to 4 days. MTBE concentrations were 1 to 5 mg/L. Samples were taken directly from the solution with a needle and injected to a purge and trap unit. MTBE and the main metabolite, TBA, were measured by GC/FID. Results and Discussion. Solutions with roots of poplar (Populus robusta) and a willow hybrid (Salix viminalis x schwerinii) produced TBA in trace amounts, probably stemming from bacteria. Significant MTBE reduction (> 10%) was not observed in any of the tests. Leaves from none of the species (trees, grasses and herbs) reduced the concentration of MTBE in the solution and no TBA, nor any other known metabolite of MTBE, was detected. Conclusion. It was not possible to find plants capable of efficiently degrading MTBE. This gives rise to the conclusion that plants probably cannot degrade MTBE at all, or only very slowly. Recommendations and Outlook. For phytoremediation projects, this has, as consequence, that the volatilization by plants (except with genetically engineered plants) is the only relevant removal process for MTBE. For risk assessment of MTBE, degradation by the plant empire is not a relevant sink process.
摘要：
The contents, affecting factors, seasonal changes and availability of fixed ammonium in major types of paddy soils derived from different parent materials in Hunan Province, China, were studied using the Silva-Bremner method by laboratory and pot experiments. Results showed that the content of fixed ammonium in the plough horizons ranged from 88.3 mg kg(-1) to 388.1 mg kg(-1), with 273.2 +/- 77.7 mg kg(-1) on average, accounting for 11.2% of total soil N on average. Content of fixed ammonium decreased in the order of newly lacustrine clayey paddy soil > alluvial sandy paddy soil > purple clayey paddy soil > newly alluvial sandy paddy soil > yellow clayey paddy soil > reddish-yellow clayey paddy soil > granitic sandy paddy soil. There were four distribution patterns of fixed ammonium in the profiles to 1-m depth, i.e., increase with the depth, decrease with increasing depth, no distinct change with the depth, and abrupt increase or decrease in some horizon. Percentage of fixed ammonium in total N increased with the depth in most of the soils. Fixation of NH4+ by soil was higher at 30 degreesC than at 20 degreesC and 40 degreesC, and continuous submergence benefited the fixation of NH4+ in newly alluvial sandy paddy soil, purple clayey paddy soil and alluvial sandy paddy soil, while alternating wetting and drying contributed to the fixation of NH4+ in yellow clayey paddy soil mostly. Fixed ammonium content in the test paddy soils was significantly correlated with < 0.01 mm clay content (P < 0.05), but not with < 0.001 mm clay content, total N, organic N and organic matter. Fixed ammonium content varied with rice growth stages. Application of N fertilizer promoted fixation of NH4+ by soil, and N uptake by rice plant promoted release of fixed ammonium from the soil. Recently fixed ammonium in paddy soil after N fertilizer application was nearly 100% available to rice plant, while native fixed ammonium was only partly available, varying with the soil type and rice type.
摘要：
Acid Deposition and its Effects were Studied by Analysing the Chemistry in Precipitation, Stream Water, Soil Water and Soils in Two Catchments in Hunan.one Site, Linkesuo (Denoted LKS), is on the Outskirts of Changsha, the Provincial Capital of Hunan, the other (Bailutang, Denoted BLT) on the Outskirts of Chenzhou in Southern Hunan.Volume-weighted Average pH Values and Sulphate Concentrations in Wet Deposition were 4.58 (Blt) and 4.90 (Lks) and 174 μmolc L-1 and 152 μmolc L-1, Respectively.Wet Deposition of Sulphate has been Estimated as 4.3 gS m-2yr-1 and 3.4 gS m-2yr-1 at Blt and Lks, Respectively.Estimates of the Corresponding Total Depositions (Dry + Wet) are 6.1 gS m-2yr-1 and 5.3 gS m-2yr-1.in Precipitation and Throughfall, Sulphate was the Major Anion and Calcium the Major Cation.in Stream and Soil Water, Nitrate was Slightly Higher than Sulphate on an Equivalent Basis and Magnesium (Mg) not much Lower than Calcium (Ca).Important Soil Properties, such as Soil pH, Soil Organic Matter (SOM) Content, Exchangeable Acidic Cations, Exchangeable Base Cations, Effective Cation Exchange Capacity (CECe), Base Saturation (BS), and Aluminium (Al) and Iron (Fe) Pools, were Determined for Five Forest Soil Profiles (Consisting of Four Horizons) in each of the Two Catchments.the Soils in BLT are Generally more Acid, have Lower BS and Higher Al and Fe Pools than the LKS Soils.the Al- and Fe-pools were Generally Higher in the Topsoils (i.e. the O and a Horizons) than in Deeper Soils (i.e. E and B Horizons) especially at the most Acidic Site (BLT).there are Significant Correlations between Fe-pools and the Corresponding Al-pools in both Catchments except between the Amorphous Feox and Alox.considering the long-term High Deposition of Sulphate, there is a Risk of Future Ecological Damage Due to Acidification, especially in the BLT Catchment, although Vegetation Damage has yet to be Observed in the Catchments.This Condition Appears to be Representative of a Large Part of Hunan.
keyword: Acid Deposition, Soil Acidification, Catchment, Al-pools, Fe-pools, Hunan
