The development of a UK kerbside scheme using known practice

Local authorities in the UK have been set challenging new targets for recycling household waste for 2003/4. This means many of them are urgently trying to determine which parameters in kerbside schemes are most important for increasing recycling rates. In this work information from previous kerbside schemes was used to plan significant improvements in an existing scheme in Horsham District, UK, and a trial was conducted using 1000 homes including a control group. It used fortnightly collection of residual waste with sets of recyclables collected on alternate weeks. The new scheme resulted in improvements of participation rates from 72 to 84%, and set-out rates from 45 to 59% (falling to 76 and 50% respectively, some months later). Details on participation and set-out for different groups of materials are given, as well as levels of excess waste and participation in the collection of garden waste.     

Systematic studies of shop and leisure voucher incentives for household recycling

This work reports on a series of medium scale trials of various voucher based incentives schemes for household recycling carried out in England. They show that increases of 10–20% in participation rates can be achieved with 3-month schemes. The results are drawn from 15 sub-projects carried out in 6 districts where parameters such as voucher value, types of shops used, demographics and community types were varied overall, allowing their effects to be explored. Surprisingly, the results show that the success does not depend on the affluence of the areas. Statistically strong data shows little difference across deprivation indices. Successful schemes were those where the vouchers were awarded on an individual household basis (very important), the value of each voucher was over £1 (€0.60), and the shops or facilities they are valid for were within half a mile (with suggestions from the public that if usable at supermarkets they would travel further). Although some improvements were seen in areas where participation rates were already over 65%, the schemes are more successful in areas which are not already achieving so highly, right down to those below 20%. Although schemes can be designed for maximum effect in small targeted areas, they could also be used on a large scale if e.g. supermarket vouchers were used. The study also reports on the costs of the schemes, which range from £5.15 per household to £12.10 per household over 3 months (including monitoring work). Possible savings of up to 50% are indicated.     

Direct measurements of urban OH reactivity during Nashville SOS in summer 1999

Emissions of volatile chemicals control the hydroxyl radical (OH), the atmosphere's main cleansing agent, and thus the production of secondary pollutants. Accounting for all of these chemicals can be difficult, especially in environments with mixed urban and forest emissions. The first direct measurements of the atmospheric OH reactivity, the inverse of the OH lifetime, were made as part of the Southern Oxidant Study (SOS) at Cornelia Fort Airpark in Nashville, TN in summer 1999. Measured OH reactivity was typically 11 s(-1). Measured OH reactivity was 1.4 times larger than OH reactivity calculated from the sum of the products of measured chemical concentrations and their OH reaction rate coefficients. This difference is statistically significant at the 1sigma uncertainty level of both the measurements and the calculations but not the 2sigma uncertainty level. Measured OH reactivity was 1.3 times larger than the OH reactivity from a model that uses measured ambient concentrations of volatile organic compounds (VOCs), NO, NO2, SO2, and CO. However, it was within approximately 10% of the OH reactivity from a model that includes hydrocarbon measurements made in a Nashville tunnel and scaled to the ambient CO at Cornelia Fort Airpark. These comparisons indicate that 30% of the OH reactivity in Nashville may come from short-lived highly reactive VOCs that are not usually measured in field intensive studies or by US EPA's Photochemical Assessment Monitoring Stations.     

Expanding the limits of the pollen-limitation concept: effects of pollen quantity and quality

Pollination commonly limits seed production, as addition of pollen to stigmas often increases fecundity. This response is usually interpreted as evidence that plants' stigmas receive too few pollen grains to maximize ovule fertilization (quantity limitation); however, many genetic studies demonstrate that poor-quality pollen can also reduce seed production (quality limitation). We explore both aspects of pollen limitation theoretically with a dose-response model that incorporates a saturating negative-exponential relation of seed production to pollen receipt. This relation depends on aspects of ovule production, pollen import, pollen-pistil interactions and seed development, all of which can contribute to pollen limitation. Our model reveals that quantity limitation is restricted to the lowest range of pollen receipt, for which siring success per pollen grain is high, whereas quality limitation acts throughout the range of pollen receipt if plants do not import the highest-quality pollen. In addition to pollinator availability and efficiency, quantity limitation is governed by all post-pollination aspects of seed production. In contrast, quality limitation depends on the difference in survival of embryos sired by naturally delivered pollen vs. by pollen of maximal quality. We briefly illustrate the distinction between these two components of pollen limitation with results from the mistletoe Tristerix corymbosus. Our model also shows that the standard pollen-supplementation technique neither estimates the total intensity of pollen limitation nor distinguishes between its quantity and quality components. As an alternative, we propose a methodological protocol that requires both measurement of seed production following excess pollination with only outcross pollen and quantification of the dose-response relation of seed output to pollen receipt. This method estimates both the total extent of pollen limitation and its two components. Finally, we consider the influences on quantity and quality limitation, which reveals that quantity limitation probably occurs much less often than has been inferred from pollen-supplementation experiments. These interpretations suggest that an expanded perspective that recognizes the fecundity consequences of pollination with poor-quality pollen would promote ecological understanding of pollen limitation.     

Two Measured Parameters Correlated to Participation Rates in Curbside Recycling Schemes in the UK

Local authorities in the United Kingdom are currently changing their approach towards recycling as they attempt to meet legislative targets. An important part of this drive is the provision of an effective curbside recycling service and it is vital to understand the parameters that influence the performance of the system offered. In this article, three primary datasets, collected from over 1400 households each, are examined for parameters correlated to participation rates. Two measured parameters were found that are not commonly identified in previous studies of curbside recycling schemes, and they are shown to merit further investigation as useful tools for planning purposes. One is the number of types of material collected; participation rates are greater for schemes collecting more materials. The second is the number of households situated on the same road; the lower the number, the higher the participation rate. In both cases, evidence of the measured correlation is presented, justifying their usefulness for planning. The multiple underlying factors causing the correlations are not identified here, but suggestions are made for further studies.