Controlling the Behaviors of Biodegradable/Bioabsorbable Polymers with Cyclodextrins

The cyclic six, seven, and eight-membered oligosaccharides -, -, and -cyclodextrins (CDs) can serve as hosts for a variety of polymer guests to form crystalline inclusion compounds (ICs), wherein the guest polymers are included in the continuous narrow channels (0.5–1.0 nm in diameter) formed by the host CD stacks. Polymers included as guests in CD-ICs are highly extended and segregated from neighboring chains by the walls of the host CD bracelets. As a consequence, when polymer-CD-ICs are treated with solvents for CDs that are non-solvents for the included polymers or with amylase enzymes, the CDs are removed and the guest polymers are coalesced into bulk samples whose structures, morphologies, and even chain conformations are different from those achieved by consolidation from their randomly coiling, entangled solutions and melts. Often these CD-IC coalesced and consequently reorganized polymer samples exhibit properties that are distinct from their normally processed bulk samples. Here we describe the CD-IC processing of several biodegradable/bioabsorbable homopolymers, copolymers, and blends made from poly (L-lactic acid), poly (-caprolactone), and poly (-hydroxybutyrate)s, with special emphasis placed on their improved and controllable properties. For example, the phase segregation and consequent crystallinities of their normally incompatible homopolymer blends and their block copolymers may be controlled and thus improved. In addition, co-inclusion of small molecule guests, such as drugs or anti-bacterials, in their common CD-ICs, and subsequent coalescence, yields well-mixed blends of these biodegradable/bioabsorbable polymers and the small molecule co-guests, which may lead, for example, to the improved delivery of drugs.     

Effect of La3+ on the activities of antioxidant enzymes in wheat seedlings under lead stress in solution culture

In order to improve the plant ability to resist lead stress, effect of 0.05 mg/l La(NO₃)₃ on the activities of catalase (CAT), superoxide dismutase (SOD), the level of malondialdehyde (MDA) in wheat seedlings under lead stress was studied. The effect of La³⁺ on plant growth, chlorophyll content in wheat seedlings after adding 0, 50, 100 mg/l Pb(NO₃)₃ to the nutrient solution for 12 days was observed. The plants were grown in nutrient solution in a strictly controlled climate growth room. Effects of La³⁺ (with La treatment) compared with check groups was evidently observed. The activities of SOD and CAT in root were enhanced 0.45–1.69 times and 33.20–77.77% respectively and MDA content was reduced 11.05–27.49% in root after treatments from the second day till the end of the experiment. The activities of SOD and CAT was found to be increased slightly (P<0.05) and MDA content decreased in shoot and root of wheat seedlings by La³⁺ under lead stress within five days after treatments compared with Pb1 and Pb2 groups. It was assumed that antioxidant enzymes was found to be increased by La(NO₃)₃, the antioxidant potential of the wheat seedlings to resist lead stress enhanced. It is suggested that La³⁺ could be used to resist lead stress at the beginning under stress while the stress was not so serious.     

Modeling assessment of air emission flux of mercury from soils in terrestrial landscape components: model tests and sensitivities

The abilities of a screening-level model to predict variations in elemental mercury (Hg0) air emissions from soils in terrestrial landscapes are examined by comparing simulation results to published observational data and by performing sensitivity analyses. Despite uncertainties and simplifications, the model results obtained offer some degree of confidence in the model's joint ability to relate readily available environmental parameters to airborne emissions of Hg predicted by coupling simple atmospheric and soil parameters with Hg cycling and transport algorithms. The model reasonably predicted the observational data in the considered data sets except for one site for which significant uncertainty was associated with model input data. Predictions are consistent with many trends observed in the field studies; better predictions were obtained for nonvegetated systems (relative errors between 0.4 and 9.7%) than for shaded-soil landscapes (relative errors between 2.3 and 27%). The model reflected field data showing that daily average emission rates of Hg0, formed by the reduction of Hg(II), are primarily controlled by changes in solar radiation, soil moisture, temperature, and, to a lesser extent, wind conditions. The model may have potential use in several preliminary studies to characterize trends of airborne Hg emitted from terrestrial sources to the atmosphere.     

Kinetic modeling of bioavailability for sorbed-phase 2,4-dichlorophenoxyacetic acid

The degradation rate of 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in silica-slurry systems to evaluate the bioavailability of sorbed-phase contaminant. After the silica particles were saturated with 2,4-D, the system was inoculated with the 2,4-D-degrading microorganism Flavorbacterium sp. strain FB4. The disappearance rate of 2,4-D was found to be greater than the rate predicted based upon liquid-phase 2,4-D concentrations. A kinetic formulation, termed the enhanced bioavailability model, was developed to describe the desorption and biodegradation processes in this batch system. The approach assumes that 2,4-D resides in both the liquid and solid phases and degradation occurs via both suspended and attached biomass. All biomass can degrade liquid-phase 2,4-D at one rate, while only attached biomass can degrade sorbed 2,4-D at another rate. An enhanced transformation factor (Ef) was introduced to express the increased biodegradation rate over that expected from the liquid phase only. This approach was able to account for the increased degradation rates observed experimentally. The results provide evidence that desorption to the bulk solution is not prerequisite to degradation, and that sorbed substrate may be available for degradation.     

Modeling pollutant release from a surface source during rainfall runoff

Though runoff from manure spread fields is recognized as an important mode of nonpoint-source pollution, there are no models that mechanistically describe transport from a field-spread manure-type source. A mechanistic, physically based model for pollutant release from a surface source, such as field-spread manure, was hypothesized, laboratory tested, and field-applied. The primary objective of this study was to demonstrate the potential applicability of a mechanistic model to pollutant release from surface sources. The laboratory investigation used stable sources and a conservative "pollutant" (KCl) so that the dynamic effects of source dissolution and chemical transformations could be ignored and transport processes isolated. The field investigation used runoff and soluble reactive phosphorus (SP) data collected from a dairy-manure-spread field in the Cannonsville watershed in the Catskills region of New York State. The model predictions corroborated well with observations of runoff and pollutant delivery in both the laboratory and the field. "Pollutant" release from surface sources was generally predicted within 11% of laboratory KCl measurements and field SP observations. Laboratory flume runoff predictions with 15 and 26% errors for 25 and 15 mm h(-1) simulated rainfall intensity experiments, respectively, represented root mean square errors of less than 0.2 mLs(-1). A 26% error was calculated for overland flow predictions in the field, which translated into approximately a 39 mLs(-1) error. Results suggest that the hypothesized model satisfactorily represents the primary mechanisms in pollutant release from surface sources.     

Greenhouse gas emissions during cattle feedlot manure composting

The emission of greenhouse gases (GHG) during feedlot manure composting reduces the agronomic value of the final compost and increases the greenhouse effect. A study was conducted to determine whether GHG emissions are affected by composting method. Feedlot cattle manure was composted with two aeration methods--passive (no turning) and active (turned six times). Carbon lost in the forms of CO2 and CH4 was 73.8 and 6.3 kg C Mg-1 manure for the passive aeration treatment and 168.0 and 8.1 kg C Mg-1 manure for the active treatment. The N loss in the form of N2O was 0.11 and 0.19 kg N Mg-1 manure for the passive and active treatments. Fuel consumption to turn and maintain the windrow added a further 4.4 kg C Mg-1 manure for the active aeration treatment. Since CH4 and N2O are 21 and 310 times more harmful than CO2 in their global warming effect, the total GHG emission expressed as CO2-C equivalent was 240.2 and 401.4 kg C Mg-1 manure for passive and active aeration. The lower emission associated with the passive treatment was mainly due to the incomplete decomposition of manure and a lower gas diffusion rate. In addition, turning affected N transformation and transport in the window profile, which contributed to higher N2O emissions for the active aeration treatment. Gas diffusion is an important factor controlling GHG emissions. Higher GHG concentrations in compost windrows do not necessarily mean higher production or emission rates.     

Integrating water-quality management and land-use planning in a watershed context

The spatial relationships between land uses and river-water quality measured with biological, water chemistry, and habitat indicators were analyzed in the Little Miami River watershed, OH, USA. Data obtained from various federal and state agencies were integrated with Geographic Information System spatial analysis functions. After statistically analyzing the spatial patterns of the water quality in receiving rivers and land uses and other point pollution sources in the watershed, the results showed that the water biotic quality did not degrade significantly below wastewater treatment plants. However, significantly lower water quality was found in areas downstream from high human impact areas where urban land was dominated or near point pollution sources. The study exhibits the importance of integrating water-quality management and land-use planning. Planners and policy-makers at different levels should bring stakeholders together, based on the understanding of land-water relationship in a watershed, to prevent pollution from happening and to plan for a sustainable future.     

Sorption, mobility, and transformation of estrogenic hormones in natural soil

Potent estrogenic hormones are consistently detected in the environment at low concentration, yet these chemicals are strongly sorbed to soil and are labile. The objective of this research was to improve the understanding of the processes of sorption, mobility, and transformation for estrogens in natural soils, and their interaction. Equilibrium and kinetic batch sorption experiments, and a long-term column study were used to study the fate and transport of 17beta-estradiol and its primary metabolite, estrone, in natural soil. Kinetic and equilibrium batch experiments were done using radiolabeled 17beta-estradiol and estrone. At the concentrations used, it appeared that equilibrium sorption for both estrogens was achieved between 5 and 24 h, and that the equilibrium sorption isotherms were linear. The log K(oc) values for 17beta-estradiol (2.94) and estrone (2.99) were consistent with previously reported values. Additionally, it was found that there was rate-limited sorption for both 17beta-estradiol (0.178 h(-1)) and estrone (0.210 h(-1)). An approximately 42 h long, steady-flow, saturated column experiment was used to study the transport of radiolabeled 17beta-estradiol, which was applied in a 5.00 mg L(-1) solution pulse for 44 pore volumes. 17beta-estradiol and estrone were the predominant compounds detected in the effluent. The effluent breakthrough curves were asymmetric and the transport modeling indicated that sorption was rate-limited. Sorption rates and distributions of the estrogens were in agreement between column and batch experiments. This research can provide a better link between the laboratory results and observations in the natural environment.     

油罐扬沸火灾预测方法的研究及安全预警系统的建立

通过研究扬沸前兆噪声特性及其声发射机理，并与典型环境噪声特性差异作了分 析、比较，提取出一组识别特征物理量，以便在扬沸火灾早期能诊断预报扬沸的发生。     

酚类化合物的HPLC测定

本文研究了酚类化合物的HPLC的测定条件:组装HPLC仪器包括:LKB2150高压泵,日立635M多波长检测器,UV—210和UV280nm,日本U—225M双笔记录仪。分离拄:500mm×2.6mm不锈钢,内填日立2618~#树脂。流动相:0.05％磷酸。流量0.015L/h～0.024 L/h。泵压:12000000～14000000Pa。进样量:0.0025～0.01ml。对苯酚,间苯三酚,邻苯三酚,邻苯二酚,对苯二酚,乙萘酚,邻甲酚,间甲酚等进行了分离测定。方法简易,灵敏度高,重复性好。