A summary of environmental legislation targeting disposable diapers and review of related literature

In recent years state and local governments, as well as private citizens, have become very concerned about the mounting solid waste disposal problem facing our nation. Special concern has been expressed over the presence of disposable diapers in the solid waste stream. Responding to the concerns, legislators in at least 25 states proposed actions regarding disposable diapers between 1990 and 1992. Several factors contributed to the number of legislative proposals regarding disposable diapers over the past few years. First was the public's and legislators' misconception about the contribution of disposable diapers to the solid waste stream. Second was an erroneous assumption held by the public and some legislators that biodegradation readily occurs in landfills. Third was the desire to increase demand for agricultural products by requiring the use of degradable products. These contributing factors and other issues surrounding the proposal and passage of environmental legislation pertaining to disposable diapers are presented in this paper and the relevant literature is summarized. To provide the necessary context, the paper contains a review of the literature concerning disposable diapers, their composition and usage; and their environmental impact and fate and a comparison of their performance and cost to those of cloth diapers.     

Diel oscillations of the photosynthesis-irradiance (P-I) relationship in natural assemblages of phytoplankton

Diel oscillations in the photosynthesis-irradiance (P-I) relationship are described for marine phytoplankton assemblages at 6 stations in an upwelling area off the southern California coast (USA) between May and August 1980. The initial slope () and asymptote (P _max) of P-I curves changed significantly over the day; both parameters were in phase and had similar changes in amplitude. The diel oscillations in photosynthesis appeared unrelated to changes in chlorophyll a concentrations. Amplitudes of daily variations in photosynthesis ranged from approximately 3 to 9, as measured by the maximum to minimum ratio for photosynthetic capacity (P _max). Diatom-rich samples collected during an upwelling event and those dominated by dinoflagellates both had midday to early afternoon maxima in and P _max. Samples from other locations had peak photosynthetic activity later in the afternoon. The relationship between and P _max was consistent in all phytoplankton samples analyzed, with a surprisingly high correlation considering the spatial and temporal scales encompassed in this study. These results indicate that the photosynthesis-irradiance (P-I) relationship is time-dependent and, moreover, that changes in and P _max are closely coupled for a variety of natural phytoplankton assemblages.     

Statistical hypothesis testing formulations for U.S. environmental regulatory standards for ozone

Environmental regulatory standards are intended to protect human health and environmental welfare. Current standards are based on scientific and policy considerations but appear to lack rigorous statistical foundations and may have unintended regulatory consequences. We examine current and proposed U.S. environmental regulatory standards for ozone from the standpoint of their formulation and performance within a statistical hypothesis testing framework. We illustrate that the standards can be regarded as representing constraints on a percentile of the ozone distribution, where the percentile involved depends on the defined length of ozone season and the constraint is stricter in regions with greater variability. A hypothesis testing framework allows consideration of error rates (probability of false declaration of violation and compliance) and we show that the existing statistics on which the standards are based can be improved upon in terms of bias and variance. Our analyses also raise issues relating to network design and the possibilities of defining a regionally based standard that acknowledges and accounts for spatial and temporal variability in the ozone distribution.     

Comparison of pollination and defensive buzzes in bumblebees indicates species-specific and context-dependent vibrations

Bees produce vibrations in many contexts, including for defense and while foraging. Buzz pollination is a unique foraging behavior in which bees vibrate the anthers of flowers to eject pollen which is then collected and used as food. The relationships between buzzing properties and pollen release are well understood, but it is less clear to what extent buzzing vibrations vary among species, even though such information is crucial to understanding the functional relationships between bees and buzz-pollinated plants. Our goals in this study were (1) to examine whether pollination buzzes differ from those produced during defense, (2) to evaluate the similarity of buzzes between different species of bumblebees (Bombus spp.), and (3) to determine if body size affects the expression of buzzing properties. We found that relative peak amplitude, peak frequency, and duration were significantly different between species, but only relative peak amplitude differed between pollination and defensive buzzes. There were significant interactions between species and buzz type for peak frequency and duration, revealing that species differed in their patterns of expression in these buzz properties depending on the context. The only parameter affected by body size was duration, with larger bees producing shorter buzzes. Our findings suggest that although pollination and defensive buzzes differ in some properties, variability in buzz structure also exhibits a marked species-specific component. Species differences in pollination buzzes may have important implications for foraging preferences in bumblebees, especially if bees select flowers best matched to release pollen for their specific buzzing characteristics.     

Using choice experiments to design wetland management programmes: The case of Severn Estuary Wetland,UK

This paper reports the results of a pilot valuation study, which was undertaken to investigate whether the public located around the Severn Estuary derive positive economic values from its sustainable management. One hundred members of the public took part in a choice experiment, the results of which indicate that overall the public derives positive and significant values from sustainable management of this wetland, however, there is some preference heterogeneity. The findings demonstrate that the choice experiment method is a promising tool, which can aid the design of socially optimal policies for sustainable management of the Severn Estuary, with possible implications for other similar wetlands in the UK.     

Modification of an ecosystem model for filling medium-sized gaps in tower-based estimates of net ecosystem productivity

Gap filling of flux data is necessary to assist with periodic interruptions in the measurement data stream. The gap-filling model (GFM), first described in Xing et al. [Xing, Z., Bourque, C.P.-A., Meng, F.-R., Zha, T.-S., Cox, R.M., Swift, E., 2007. A simple net ecosystem productivity model for gap filling of tower-based fluxes: an extension of Landsberg's equation with modifications to the light interception term. Ecol. Model. 206, 250–262], was modified to account for the day-to-day control of net ecosystem productivity (NEP) by incorporating air and soil temperature as new controlling variables in the calculation of NEP. To account for the multiple-phase influences of air and soil temperature on plant growth we model ecosystem respiration as a function of soil and canopy respiration. The paper presents model development in an incremental fashion in order to quantify the contribution of individual model enhancements to the prediction of NEP during periods when air and soil temperature variations are important.     

Expert variability provides perspective on the strengths and weaknesses of citizen-driven intertidal monitoring program

Citizen scientist programs are a means to efficiently conduct large-scale surveys of ecosystems or managed species, provided that concerns over the quality and use of data generated by nonexperts can be addressed. This study presents actions taken in a citizen science program to assure data quality and demonstrates the validity of citizen-generated data. In this case the accuracy of data collected by secondary school students as citizens in a program that quantitatively sampled benthic rocky intertidal communities at 13 sites on Maui, Molokai, Oahu, and Hawai'i island during the years 2004-2007 was evaluated. In 2007, two independent research teams collected data simultaneously with students at five sites on eight sampling dates. Comparisons of Shannon diversity and Bray-Curtis similarity values computed and simulated from student and researcher collected data revealed that nonexpert students accurately collect community-level data within the range of the variation that occurs between researchers. Students were, however, likely to misidentify cryptic and rare species. These findings have direct implications for the conservation goals of the monitoring program as the assessment reveals that students are likely to misidentify early alien introductions but are able to monitor the abundances of native and introduced species once they become established. The validity assessment designed for this investigation is unique in that it directly compares consistent errors made by citizens in data collection to expert variability to identify usage limitations and can be a guide for future studies that involve the efforts of trained volunteers.     

应用时间-活动模式估计儿童个体NOx暴露水平

将时间-活动模式与微环境空气污染物监测相结合估计儿童个体NO_x暴露水平. 分别在北京和青岛两市各选择3所学校监测校园环境污染物,并在每个学校选择10名儿童监测其家庭居室空气中ρ(NO_x)及个体24 h NO_x暴露水平,同时收集其时间-活动信息,采用时间-活动模式估计儿童的个体暴露水平. 交通工具中的NO_x暴露水平可通过校门口空气中ρ(NO_x)和交通工具的污染水平系数(λ)估计.结果表明:利用时间-活动模式模拟的儿童个体24 h NO_x暴露水平为0.041 mg/m3,与调整后的个体暴露实测水平相关性较好(R0.785,P<0.01),差值为(-0.002　6±0.013　0) mg/m3,二者的差异无统计学意义 (t0.139,P>0.05).表明采用时间-活动模式与微环境空气质量监测结果相结合方法估计的儿童NO_x暴露水平与个体实际暴露水平一致.