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861.
Sherald H. Gordon Syed H. Imam Christopher James 《Journal of Polymers and the Environment》2000,8(3):125-134
A new chemometric method based on Beer's law was derived that uses peak ratios from Fourier transform infrared spectra of neat polymers and their composite plastics to quantify degradation of the individual polymers after biodegradation. The method affords direct measurement of polymer concentrations and weight losses without prior calibration against known composites. Unlike traditional chemometric methods, this method does not require sampling of as many or more different composites as the number of polymers in the composite being analyzed. When the neat polymer spectra are known, only two measurements, one before and one after biodegradation, are needed. A potentially major advance is that the method allows automation of analytical infrared wavelength selection by computer from all possible wavelength combinations. In this paper, the theoretical basis and derivation of the mathematical model for multicomponent systems is presented. The validity of the model was proved initially by applying the method to simulated two-polymer and three-polymer composites and finally by comparing test results with known samples of biodegradable composites prepared in the laboratory. Potential future development of the method for more challenging multicomponent plastics is discussed. 相似文献
862.
William G. MacIntyre Christopher P. Antworth Thomas B. Stauffer Riki G. Young 《Journal of contaminant hydrology》1998,31(3-4)
Properties related to sorption and transport of organic compounds have been determined on 126 sections of 17 cores taken in an aquifer at Columbus Air Force Base in Columbus, MS. Each core section was homogenized prior to analysis. Organic carbon content (OC), specific surface area (SA), distribution coefficient (Kd) for naphthalene, and particle size distribution were measured on each section. Hydraulic conductivity (Kh) for each section was calculated from the particle size distributions. Kh values obtained were comparable with those from earlier borehole flowmeter and pulse tracer tests. Frequency distributions for all properties were lognormal. The arithmetic means and standard deviations for all samples are: OC=0.028% (+0.031, −0.015), SA=4.02 m2/g (+3.95, −1.99), Kd=0.198 l/kg (+0.195, −0.098), Kh=0.00033 m/s (+0.00051, −0.00020). These standard deviations are asymmetrical about the mean because statistics were calculated using log-transformed data, and antilogarithms then taken to obtain the results in the units of property measurement. Variabilities, expressed as coefficients of variation, were similar for all properties. Correlations between the properties were investigated. A good correlation between naphthalene Kd and OC (r=0.78) was found, and other correlations were weak, thus indicating that organic carbon content may control sorption of nonpolar organic solutes in this low carbon aquifer. Autocorrelation (variogram) analysis indicated that, for all properties, correlation lengths were less than the distance between sample points, which were separated by about 20 m horizontally and 1 m vertically. Separate statistical analysis of two widely separated groups of wells showed the groups similar in all properties, except organic carbon. Large-scale inhomogeneity was not detected, although earlier tracer tests produced irregular plumes indicating inhomogeneity in observed solute transport. Implications of the results to site characterization, in situations where aquifers are heterogeneous on short length scales, are discussed. 相似文献
863.
Brandie Fariss Nicole DeMello Kathryn A. Powlen Christopher E. Latimer Yuta Masuda Christina M. Kennedy 《Conservation biology》2023,37(1):e13973
Efforts to devolve rights and engage Indigenous Peoples and local communities in conservation have increased the demand for evidence of the efficacy of community-based conservation (CBC) and insights into what enables its success. We examined the human well-being and environmental outcomes of a diverse set of 128 CBC projects. Over 80% of CBC projects had some positive human well-being or environmental outcomes, although just 32% achieved positive outcomes for both (i.e., combined success). We coded 57 total national-, community-, and project-level variables and controls from this set, performed random forest classification to identify the variables most important to combined success, and calculated accumulated local effects to describe their individual influence on the probability of achieving it. The best predictors of combined success were 17 variables suggestive of various recommendations and opportunities for conservation practitioners related to national contexts, community characteristics, and the implementation of various strategies and interventions informed by existing CBC frameworks. Specifically, CBC projects had higher probabilities of combined success when they occurred in national contexts supportive of local governance, confronted challenges to collective action, promoted economic diversification, and invested in various capacity-building efforts. Our results provide important insights into how to encourage greater success in CBC. 相似文献
864.
Luke Christopher Evans Matthew P. Greenwell Victoria L. Boult Thomas Frederick Johnson 《Conservation biology》2023,37(4):e14070
Social media is an arena of debate for contentious political and social topics. One conservation topic debated online is the acceptability of trophy hunting, a debate that has implications for national and international policy. We used a mixed-methods approach (grounded theory and quantitative clustering) to identify themes in the trophy hunting debate on Twitter. We examined commonly co-occurring categories that describe people's stances on trophy hunting. We identified 12 categories and 4 preliminary archetypes opposing trophy hunting—activism, scientific, condemning, and objecting—whose opposition derived from different moral reasoning. Few tweets (22) in our sample of 500 supported trophy hunting, whereas 350 opposed it. The debate was hostile; 7% of tweets in our sample were categorized as abusive. Online debates can be unproductive, and our findings may be important for stakeholders wishing to effectively engage in the trophy hunting debate on Twitter. More generally, we contend that because social media is increasingly influential, it is important to formally contextualize public responses to contentious conservation topics in order to aid communication of conservation evidence and to integrate diverse public perspectives in conservation practice. 相似文献
865.
Chris Seijger Daniela Kleinschmit Dietrich Schmidt-Vogt Muhammad Mehmood-Ul-Hassan Christopher Martius 《Ambio》2021,50(12):2311
Major land use changes such as deforestation and restoration influence water resources in agriculture–forest landscapes. Changes are observed in water flows, groundwater infiltration, water quality and rainfall. Interdisciplinary water–forest research has unravelled biophysical parts of the interplay that influences forest and water resources. In this Perspective paper, we propose an expanded interdisciplinary research approach to study water and policies in agriculture–forest frontiers. The approach differs in four important aspects from previous ones: (i) a conceptual ‘frontier’ understanding; an analytical focus on (ii) agriculture and (iii) policy–water linkages; (iv) empirical attention to northern and southern countries. The approach is put into practice with the “Pendulum” framework, with interventions and the agriculture–forest frontier oscillating over time between exploitation and restoration. Through the approach, a better understanding will be provided on the dynamic interplay of water and policies in oscillating agriculture–forest frontiers, with changing outcomes for people and environment. 相似文献
866.
Linda Westman James Patterson Rachel Macrorie Christopher J. Orr Catherine M. Ashcraft Vanesa Castn Broto Dana Dolan Mukesh Gupta Jeroen van der Heijden Thomas Hickmann Robert Hobbins Marielle Papin Enora Robin Christina Rosan Jonas Torrens Robert Webb 《Ambio》2022,51(6):1402
The crises that cities face—such as climate change, pandemics, economic downturn, and racism—are tightly interlinked and cannot be addressed in isolation. This paper addresses compound urban crises as a unique type of problem, in which discrete solutions that tackle each crisis independently are insufficient. Few scholarly debates address compound urban crises and there is, to date, a lack of interdisciplinary insights to inform urban governance responses. Combining ideas from complex adaptive systems and critical urban studies, we develop a set of boundary concepts (unsettlement, unevenness, and unbounding) to understand the complexities of compound urban crises from an interdisciplinary perspective. We employ these concepts to set a research agenda on compound urban crises, highlighting multiple interconnections between urban politics and global dynamics. We conclude by suggesting how these entry points provide a theoretical anchor to develop practical insights to inform and reform urban governance. 相似文献
867.
Kevin A. Schug Theodore R. Skingel Sandra E. Spencer Carlos A. Serrano Cuong Q. Le Christopher A. Schug Theodore W. Valenti Jr. Bryan W. Brooks Laura D. Mydlarz James P. Grover 《Journal of the American Water Resources Association》2010,46(1):33-44
Schug, Kevin A., Theodore R. Skingel, Sandra E. Spencer, Carlos A. Serrano, Cuong Q. Le, Christopher A. Schug, Theodore W. Valenti, Jr., Bryan W. Brooks, Laura D. Mydlarz, and James P. Grover, 2010. Hemolysis, Fish Mortality, and LC-ESI-MS of Cultured Crude and Fractionated Golden Alga (Prymnesium parvum). Journal of the American Water Resources Association (JAWRA) 46(1):33-44. DOI: 10.1111/j.1752-1688.2009.00389.x Abstract: Erythrocyte lysis and fish mortality assays, in combination with high performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis, were investigated for bioassay-guided fractionation of cultured golden alga (Prymnesium parvum). Intracellular constituents from isolated cell pellets and extracellular supernatant growth medium were fractionated by a variety of common separation modes, including reversed phase and normal phase solid phase extraction step fractionation procedures. For reversed phase fractionation of extracellular growth medium, one fraction was obtained that displayed hemolytic activity and adversely affected fish survival. Effective dose concentrations for this sample were similar in both assays and the LC-ESI-MS analysis of the fraction showed a number of mass spectral signals which were distinct to this fraction. Fractions obtained from separation of an ethanol extract of the lyophilized cell pellet provided one sample that was highly hemolytic, but not toxic to fish. Discrepancies such as this, along with notable fish behavioral responses from other nonhemolytic cell pellet fractions, problems with the use of unbonded silica gel for fractionation, and misleading mass spectral signatures are interesting in the context of our current understanding of P. parvum toxicity and remain to be investigated further. This work provides an account of ongoing research aimed toward comprehensive elucidation of toxic constituents produced by golden alga for the purpose of providing a better understanding and means to potentially remediate the ecological impact of this harmful bloom organism. 相似文献
868.
Koffi L. Dagnon Christopher Thellen Jo Ann Ratto Nandika A. D’Souza 《Journal of Polymers and the Environment》2010,18(4):510-522
The degradation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) coated brown Kraft paper and its components in a constructed soil environment was investigated. Soil burial tests were
carried out over 8 weeks. Weight loss measurements, photographic analysis, environmental scanning electron microscopy (ESEM),
dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were conducted to assess the physical, structural,
mechanical and thermal behavior before and after the soil burial test. Paper showed the highest physical degradation and weight
loss. With respect to the control samples, the stiffness of the partially degraded samples decreased. The overall crystallinity
of the biopolymer and the coated paper was affected significantly by burial. The pure biopolymer’s weight loss was substantially
enhanced when coated on paper. This result reveals a possible increased microbial population in the coated paper relative
to the pure biopolymer. 相似文献
869.
van Leeuwen JA Lewis R Goonan P Struve N Everson A Nothrop S Smernik RJ Chow CW Fabris R Rupasinghe M 《Environmental science and pollution research international》2012,19(6):2151-2158
Purpose
The characteristics of organics in sulphite pulp mill effluent and in the receiving environment of effluent discharge were investigated to assess the basis for the persistence or attenuation of colour.Methods
Characterization of organics was conducted through determination of SUVA, specific colour, and molecular weight distribution of organics using high performance size exclusion chromatography and by solid-state 13?C cross polarization (CP) NMR. The characteristics of organics from mill wastewater before and after secondary aerobic treatment, followed by lime treatment and from the receiving environment, an enclosed brackish lake were compared. Changes in the character of organics in lake water over a period of 14?years were studied in the context of changes in mill processing and climate impacts.Results
High colour in mill effluent and in receiving waters correlated with high SUVA and specific colour levels, high molecular weight range and aromatic content. Conversely, lake waters with low colour had UV absorbing compounds of much lower molecular weight range and low relative abundance of aromatic compounds. Attenuation of colour and changes in the character of organics in the receiving environment coincided with increased concentrations of metal cations.Conclusions
These increased concentrations appear to be due to the effects of climate change, lake management and their presence in mill effluent, with subsequent discharge to the lake. Attenuation of colour was found to be predominantly through removal of high molecular weight aromatic compounds where the removal processes could be through adsorption and co-precipitation with divalent metals, as well as through dilution processes. 相似文献870.
He Y Pedigo CE Lam B Cheng Z Zheng Y 《Journal of environmental science and health. Part. B》2012,47(2):74-80
Rice can be a major contributor to dietary arsenic exposure because of the relatively high total arsenic concentration compared to other grains, especially for people whose main staple is rice. This study employed in vitro gastrointestinal fluid digestion to determine bioaccessible or gastrointestinal fluid extractable arsenic concentration in rice. Thirty-one rice samples, of which 60 % were grown in the United States, were purchased from food stores in New York City. Total arsenic concentrations in these samples ranged from 0.090 ± 0.004 to 0.85 ± 0.03 mg/kg with a mean value of 0.275 ± 0.161 mg/kg (n = 31). Rice samples with relatively high total arsenic (>0.20 mg/kg, n = 18) were treated by in vitro artificial gastrointestinal fluid digestion, and the extractable arsenic ranged from 53 % to 102 %. The bioaccessibility of arsenic in rice decreases in the general order of extra long grain, long grain, long grain parboiled, to brown rices. 相似文献