Model reactor for photocatalytic degradation of persistent chemicals in ponds and waste water

A laboratory scale flow-through model reactor for the degradation of persistent chemicals using titanium dioxide (TiO₂) as photocatalyst immobilized on glass beads is presented. In the test system with a volume of 18 L contaminated water is pumped to the upper part of the floating reactor and flows over the coated beads which are exposed to UV-radiation. The degradation of two dyes of different persistance was investigated. Primary degradation of methylene blue did not fit a first order kinetic due to coincident adsorption onto the photocatalyst and direct photolysis, resulting in a half-life of 6 h. A filtrate of a green algae suspension accelerated the colour removal. In contrast, reactive red 2 was degraded only by photocatalysis; neither adsorption nor direct photolysis led to a colour removal. The course of primary degradation followed a first order kinetic with a half-life of 18 h and a rate constant of 0.04 h⁻¹. Analysis of the degradation products indicated mineralization by detection of NO₂⁻ and NO₃⁻, accompanied by a decrease of pH and an increase of conductivity. A successful adaptation of the model reactor (scale 1:10) to dimensions required for surface waters and waste water treatment plants would be a costefficient and environmentally sustainable application of photocatalysis for the treatment of industrially polluted water and could be of relevance for third world contries, particularly those favoured by high solar radiation.     

Enzymatic degradation of poly([R,S] β-hydroxybutyrate)

The synthetic analogue of a bacterially produced polyester, poly(-hydroxybutyrate) (PHB) was synthesized from racemic -butyrolactone using anin situ trimethyl aluminum-water catalyst. The polymer was fractionated into samples differing in molecular weight and isotactic diad content. The latter was closely related to degree of crystallinity. The biodegradation of these fractions were examined by monitoring mass loss over time in the presence of anAlcaligenes faecalis T1 extracellular bacterial poly(-hydroxybutyrate) depolymerase. The fraction with high isotactic diad tacticity content showed little or no degradation over a 50 hour incubation period, whereas the fraction of intermediate isotactic diad content degraded in a continuous steady fashion at a rate that was less than that for bacterial PHB. The low isotactic diad fraction underwent a rapid initial degradation, followed by no further mass loss. The presence of stereoblocks in the polymer structure of the various fractions was an influence on the degree of susceptibility towards degradation and is related to sample crystallinity.     

大气CO_2增加对生态系统的影响

根据Ｃ＿３植物和Ｃ＿４植物对高浓度ＣＯ＿２的不同反应，评述了富ＣＯ＿２大气对生态系统的影响。结论是大气ＣＯ＿２浓度增加将导致生态系统发生一系列变化，包括生物多样世的减少、营养循环受阻、虫灾发生和温室效应加剧等。     

Scenarios of major terrestrial ecosystems in China

The spatial pattern and mean-center shift of major terrestrial ecosystems, termed Holdridge Life Zones (HLZ), during the periods from 1961 to 1990 (T1), from 2010 to 2039 (T2), from 2040 to 2069 (T3) and from 2070 to 2099 (T4) were analyzed by combining the zonal patterns of climatic change in China and the climatic change scenarios of HadCM2 and HadCM3. The results showed that nival area would decrease rapidly with temperature increase in the future. HadCM2 and HadCM3 predicted that the nival areas might disappear in 552 years and 204 years, respectively. Using both HadCM2 and HadCM3, the five HLZ types with the largest areal extent are nival zone, cool temperate moist forest, warm temperate moist forest, subtropical moist forest and boreal wet forest, which collectively account for more than 50% of China's land mass. Among these five HLZ types, nival zone, warm temperate moist forest and boreal wet forest would decrease continuously, whereas subtropical moist forest and cool temperate forest would increase continuously during the four periods. HLZ diversity and patch connectivity would increase continuously in the 21st century. The shift distances of mean centers of HLZ types simulated using HadCM3 were markedly greater than those simulated using HadCM2, in general. The results from both HadCM2 and HadCM3 showed that boreal wet forest, subtropical moist forest, tropical dry forest, warm temperate moist forest and subtropical wet forest had bigger shift ranges, indicating that these HLZ types are more sensitive to the climatic change scenarios of HadCM2 and HadCM3.     

KClO3对龙眼产期的调控效应

以自行配制、主要有效成份为KClO3的龙眼产期调控剂进行田间试验．结果表明：催花土壤施用剂量以每平方米树冠面积180g效果最佳；不同品种龙眼对药物的敏感程度不同，以石硖、储良龙眼最为敏感，平均抽花率可达80％以上．不同季节和不同梢期施药，龙眼抽花率存在显著差别；药剂干施回泥后淋水、干施淋水后回泥和拌水淋施这3种土壤给药方式的促花效果差异不显著；反季节与正造栽培收获的龙眼相比，果实质量存在一定差异，春季收获的果实个大肉厚，外观较佳，但糖份含量等品质指标则较差．KClO3调控龙眼产期的效果明显，配合相应的树体管理和土壤水分养分调控措施，可实现龙眼产期的人工合理控制．表7参20     

广东土地退化及治理对策

本文概述土地退化的原因和状况。通过对广东山区土壤和东江流域低产耕地的大批土壤剖面分析数据的统计和推算,结果表明,广东的林地退化面积约占全省陆地面积的35％;旱地土地退化面积占全省旱地总面积的95％;水田土地退化面积约占全省水田总面积的25％。根据广东的省情,提出土地退化治理的对策:提高认识,增加投入,组织力量,开展调查摸底;制订整体治理规划,分步实施;明确治理的中心任务,推进面上治理利用,加强研究工作。     

The Role Played by Acetyl Group Distribution Patterns in Substituted Starch Toward Enzymatic De-acetylation and Chain Fragmentation

The nature and distribution of the acetylated groups were evaluated by ¹³C-NMR and ¹H-NMR. The starch substrate with a DS of 1.5 comprises only two patterns: -(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose. The starch with a DS of 3.0 also comprises two patterns: 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose; whereas starch (DS = 1.9) contains 4 patterns: 2,3,6-tri-O-acetyl--(14)-d-glucopyranose, 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose terminal, 2,6-di-O-acetyl--(14)-d-glucopyranose, and 3,6-di-O-acetyl--(14)-d-glucopyranose. Using esterase from Viscozyme, it has been possible to hydrolyze up to 7% of the DS 3.0 starch. An -amylase (Fungamyl 800) was then added to these acetylesterases. With a 2.4 FAU/mL fraction of -amylase and 2.4 U/mL from the Viscozyme's acetylesterase, 28% of the acetylated end groups were hydrolyzed for the starch substrates with DS 3.0. Moreover, a synergic action between -amylase and acetylesterase was noticed, allowing fragmentation of 32% for DS 1.5, 30% for DS 1.9, and 11% for DS 3.0.     

Polymer Mineralization in Soils: Effects of Cold Storage on Microbial Populations and Biodegradation Potential

Soil retrieval, processing and storage procedures can have a profound effect on soil microorganisms. In particular, changes in soil microbial populations may adversely affect the biological activity of a soil and drastically alter the soil's potential to mineralize added substrates. The effects of cold storage on the biodegradation of a series of test polymers was investigated using two soils—a synthetic soil mix (SM-L8) and a field soil (Bridgehampton silt loam) from Rhode Island (RI-1). Biodegradation tests were conducted using freshly prepared/collected soil and again following storage at 4°C for 3 to 8 months. Prior to each biodegradation test, the soils were incubated at 60% water-holding capacity (WHC) and 25°C to rejuvenate the microbial populations; the soils were incubated for periods of 48 h (freshly collected soil) or 25 days (soils stored at 4°C). Soil microbial populations were assessed by enumerating different segments of the population on agar plates containing different selective media. Mineralization of the test polymers (cellulose, poly-3-hydroxybutyrate, and starch acetate, d.s. 1.5) was monitored using standard respirometric techniques. Our results demonstrated that cold storage had a generally negative effect on the soil microbial populations themselves but that its effect on the capacity of the soil microorganisms to degrade the test polymers varied between soils and polymer type. Whereas cold storage resulted in dramatic shifts in the community structure of the soil microbial populations, substantial restoration of these populations was possible by first conditioning the soils at 60% WHC and ambient temperatures for 25 days. Likewise, although the effects of cold storage on polymer mineralization varied with the test polymer and soil, these effects could be largely offset by including an initial 25-day stabilization period in the test.     

Environmental degradation by mud in tropical estuaries

In wet tropical countries, the intense rainfall and the lack of effective restrictions on human activities in the river catchment leads to increased rates of soil erosion. This has increased the sediment loads many times over from the natural level. As a result, estuarine and coastal waters are becoming increasingly muddy with associated losses for society in terms of increased flooding and a degradation of the environment, the fisheries and the economic use of these waters. It is suggested that science-based models be used to predict the fate of mud in estuaries and coastal waters when planning development in river catchments, particularly in wet tropical countries. This would help integrate land and water management. Modelling technology is demonstrated by a combination of field and model studies in four turbid tropical estuaries, namely the Fly River in Papua New Guinea, the Mekong River in Vietnam, the Cimanuk River in Indonesia, and Hinchinbrook Channel in Australia. The final model is adapted to local conditions and extensively uses data assimilation especially for open boundary conditions. There can be a feedback between the hydrodynamics and the mud dynamics when the system silts; in wet tropical countries this can occur rapidly, sometimes in only 30 years. Electronic Publication     

Environmental Persistence of Chemicals

- DOI: http://dx.doi.org/10.1065/espr2006.01.008 Background The hazard criterion of persistence as it applies to chemicals in the environment is reviewed and discussed. This quantity can not be measured directly in the environment, thus it must be estimated using models that synthesise information on chemical half-lives and partitioning properties, the nature of the environment and how the chemical is released into the environment. Main Features It is suggested that the preferred criterion is the average residence time of the chemical in the environment, i.e. conceptually the sum of the life-times of all molecules (attributable only to losses by degrading reactions) divided by the number of molecules. If all chemical fate processes are first order, this persistence is independent of the quantity of chemical introduced and whether introduction is steady- or unsteady-state in nature. It is shown that in a multimedia environment persistence is affected not only by degradation kinetics, but also by mode-of-entry and partitioning. For screening level purposes a Level II equilibrium model may be adequate but a Level III model is generally preferable for estimating the average persistence. If a distribution of persistences is required a dynamic Level IV model must be used. Discussion The implications for regulating chemicals on the basis of persistence are discussed. Conclusion It is concluded that the preferred strategy is to use Level II, III, and IV models and that the use of only degradation kinetics or media-specific half-lives can be misleading and uneconomical.