Willingness to pay to improve domestic water supply in rural areas of Central Tanzania: Implications for policy

This analysis estimates willingness to pay to improve community-based rural water utilities in the Dodoma and Singida Regions of Central Tanzania, using Multinomial Logit functions. An estimate of willingness to pay provides an indication of the demand for improved services and potential for them being sustainable. Surveys were conducted in a total of 30 villages in the two regions. In the Dodoma Region, about 14% of respondents indicated that they were satisfied with the status quo, 64% suggested increasing water discharge and watering points, and 22% proposed other improvements relating to water quality. In the Singida Region, 31% of the respondents were satisfied with the status quo, 59% wanted deeper boreholes and watering points, and 10% indicated other types of improvement relating to water quality. The Multinomial Logit functions indicated that the interaction between the water quality variable and proposed bids were important in making choices with reference to the type of improvement desired. Respondents who wanted to increase water supply in Dodoma Region were willing to pay 32 Tsh above the existing tariff of 20 Tsh/bucket. In the Singida Region, the analogous amount was 91 Tsh per household per year above the existing user fee of 508 Tsh per household per year. If the tariff or user fees have to be increased, the estimated average potential revenue for the surveyed villages was 252 million Tsh/year (US$265 263) in the Dodoma Region, and 5.2 million Tsh/year (US$5474) in the Singida Region. In the future, strategic planning is needed to ensure that improvements proposed potentially improve cost recovery initiatives and increase the level of consumer satisfaction. Also, care will be needed to ensure that more disadvantaged community members do not suffer unduly from increases in tariff or user fees.     

Identification and mapping of heavy metal pollution in soils of a sports ground in Galway City,Ireland, using a portable XRF analyser and GIS

Heavy metals in urban soils continue to attract attention because of their potential long-term effects on human health. During a previous investigation of urban soils in Galway City, Ireland, a pollution hotspot of Pb, Cu, Zn and As was identified in the sports ground of South Park in the Claddagh. The sports ground was formerly a rubbish dumping site for both municipal and industrial wastes. In the present study, a portable X-ray fluorescence (PXRF) analyser was used to obtain rapid in-situ elemental analyses of the topsoil (depth: about 5–10 cm) at 200 locations on a 20 × 20-m grid in South Park. Extremely high values of the pollutants were found, with maximum values of Pb, Zn, Cu and As of 10,297, 24,716, 2224 and 744 mg/kg soil, respectively. High values occur particularly where the topsoil cover is thin, whereas lower values were found in areas where imported topsoil covers the polluted substrate. Geographic Information Systems (GIS) techniques were applied to the dataset to create elemental spatial distribution maps, three-dimensional images and interpretive hazard maps of the pollutants in the study area. Immediate action to remediate the contaminated topsoil is recommended to safeguard the health of children who play at the sports ground.     

Robust, comparable population metrics through collaborative photo-monitoring of whale sharks Rhincodon typus.

The formulation of conservation policy for species that are rare and migratory requires broad cooperation to ensure that adequate levels of standardized data collection are achieved and that the results of local analyses are comparable. Estimates of apparent survival rate, relative change in abundance, and proportions of newly marked and returning individuals can inform local management decisions while highlighting corresponding changes at other linked research stations. We have applied computer-assisted photo-identification and mark-recapture population modeling to whale sharks Rhincodon typus at Ningaloo Marine Park (NMP), Western Australia, to create a baseline trend for comparison with other regional aggregations of the species. We estimate several ecological parameters of interest, including an average apparent survival rate of 0.55 yr(-1) for sharks newly marked (new) and 0.83 yr(-1) for sharks captured in multiple seasons (philopatric). The average proportion of philopatric sharks is found to be 0.65 of the total population, and we derive an average population growth rate of 1.12 yr(-1) for them. Our analysis uncovered significant heterogeneity in capture and survival probabilities in this study population; our chosen model structures and data analysis account for these influences and demonstrate a good overall fit to the time-series data. The results show good correspondence between capture probability and an available measure of recapture effort, suggesting that unmodeled systematic effects contribute insignificantly to the model fits. We find no evidence of a decline in the whale shark population at NMP, and our results provide metrics of value to their future management. Overall, our study suggests an effective approach to analyzing and modeling mark-recapture data for a rare species using computer-assisted photo-identification and opportunistic data collection from ecotourism to ensure the quality and volume of data required for population analysis.     

Studies of the behaviour and fate of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate and tri-(2.4-di-t-butylphenyl)phosphite in the environment.

In order to evaluate the environmental risk potential of the polymer-additives octadecyl-3-(3.5-di-t-butyl-4-hydroxyphenyl)propionate (additive 1) and tri-(2.4-di-t-butylphenyl)phosphite (additive 2) we have studied the degradation of the 14C-labelled single components and their release from a polypropylene matrix in abiotic and biotic test systems as well as their transport behaviour in soil. The biotic degradation in waste compost, activated sludge and in soil was studied. In order to conduct release tests, waste disposal material were used as well. The abiotic degradation was effectuated by photooxidation at a catalytic surface. The highest mineralisation rates were obtained by photooxidative degradation of the two test substances. The maximum content of bounded residues was found for additive 1 in soil and for additive 2 in waste compost. In the extracts of soil and compost, the principal metabolites could be identified in the case of additive 1 as 7.9-di-t-butyl-1-oxaspiro[4.5]deca-6.9-dien-2.8-dion and in activated sludge as the methyl ester of 3-(3.5-di-t-butyl-4-hydroxyphenyl) propionic acid. Additive 2 metabolised in all degradation tests nearly completely under formation of two products. The main component was identified as tri-(2.4-di-t-butylphenyl)phosphate. Both polymer-additives were eluated from the chosen soil types. The transport behaviour of additive 1 was independent from the soil type. In all test matrices additive 1 as well as additive 2 were released from polypropylene. Because the amounts of additive 1 and 2 absorbed onto soil particles were taken into account, the highest liberation rates were found in the soil test.     

Effect of chlorophenolic pesticides on the photochemistry of riboflavin

The possibility of riboflavin sensitized photo‐oxidation of polychlorinated pesticides was investigated. The dye proved to be an inefficient sensitizer for that purpose, when irradiated with visible light, in aereated aqueous solutions. A quenching of singlet and triplet excited states of the chromophore (depending on the concentrations of the quencher) is responsible for this failure in the photo‐degradation of the pesticides, which resulted easily oxidizable, via singlet oxygen mechanism, when proflavine was employed as a sensitizer. Parallel, and as a direct consequence, the rate of aerobic riboflavin photobleaching decreased drastically in the presence of the chlorophenols.

The implication of our results on the inhibition of riboflavin degradation by the presence of chlorinated phenolic pesticides in the environment, is discussed, from the point of view of a kinetic and mechanistic study.     

Importance of atmospherically deposited nitrogen to the annual nitrogen budget of the Neuse River estuary,North Carolina

Wet deposition of nitrogen, as NH(4)(+), NO(3)(-), and organic N, contributes up to 50% of the total externally supplied or 'new' N flux to the Neuse River Estuary (North Carolina). Excessive nitrogen (N) loading to N-sensitive waters such as the Neuse River Estuary has been linked to changes in microbial and algal community composition and function (harmful algal blooms), hypoxia/anoxia, and fish kills. In a 4-year study from July 1996 to July 2000, the weekly wet deposition of NH(4)(+), NO(3)(-), and dissolved organic N was calculated, based on concentration and precipitation measurements, at 11 sites on a northwest-southeast transect in the watershed. Data from this period indicate that the annual mean total wet atmospherically deposited (AD)-N flux was 11 kg ha(-1) year(-1). Deposition was fairly evenly distributed between nitrate, ammonium, and organics (32%, 32%, and 36%, respectively). Seasonally, the summer (June-August) months contained the highest weekly wet total N deposition; this trend was not driven by precipitation amount. Estimates of watershed N retention and in-stream riverine processing revealed that the AD-N flux contributed an estimated 20% (range of 15-51%) of the total 'new' N flux to the estuary, with direct deposition of N to the estuary surface accounting for 6% of the total 'new' N flux. This study did not measure the dry depositional flux, which may double the contribution of AD-N to the estuary. The AD-N is an important source of 'new' N to the Neuse River Estuary as well as other estuarine and coastal ecosystems downwind of major emission sources. As such, AD-N should be included in effective nutrient mitigation and management efforts for these N-sensitive waters.     

Dye-sensitized photodegradation of the fungicide carbendazim and related benzimidazoles

The present work studies the visible-light-promoted photodegradation of the colorless fungicide carbendazim (methyl 2-benzimidazolecarbamate) and several 2-substituted benzimidazoles (SBZ's), in water or water-methanol solution, in the presence of air and, as a photosensitizer, the synthetic xanthene dye Rose Bengal (RB) or the natural pigment riboflavin (Rf). The results indicate that the degradation of each particular SBZ depends on its chemical structure and on the sensitizer employed. In the presence of RB, the degradation always operates via a singlet molecular oxygen (O(2)((1)Delta(g)))-mediated mechanism, through a highly efficient process, as deduced from the comparison of the rate constants for physical and chemical quenching of O(2)((1)Delta(g)). In the presence of Rf, the visible-light irradiation of any of the studied SBZ's produces a series of competitive processes that depend on the relative concentrations of Rf and SBZ. These processes include the quenching of excited singlet and triplet Rf states by the SBZ and the generation of both O(2)((1)Delta(g)) and superoxide radical anion (O(2)(-)), the latter generated by electron transfer from excited Rf species to the dissolved oxygen. The overall result is the photodegradation of the SBZ and the photoprotection of the sensitizer.     

Early atmospheric detection of carbon dioxide from carbon capture and storage sites

The early atmospheric detection of carbon dioxide (CO₂) leaks from carbon capture and storage (CCS) sites is important both to inform remediation efforts and to build and maintain public support for CCS in mitigating greenhouse gas emissions. A gas analysis system was developed to assess the origin of plumes of air enriched in CO₂, as to whether CO₂ is from a CCS site or from the oxidation of carbon compounds. The system measured CO₂ and O₂ concentrations for different plume samples relative to background air and calculated the gas differential concentration ratio (GDCR = ?ΔO₂/ΔCO₂). The experimental results were in good agreement with theoretical calculations that placed GDCR values for a CO₂ leak at 0.21, compared with GDCR values of 1–1.8 for the combustion of carbon compounds. Although some combustion plume samples deviated in GDCR from theoretical, the very low GDCR values associated with plumes from CO₂ leaks provided confidence that this technology holds promise in providing a tool for the early detection of CO₂ leaks from CCS sites. Implications: This work contributes to the development of a cost-effective technology for the early detection of leaks from sites where CO₂ has been injected into the subsurface to enhance oil recovery or to permanently store the gas as a strategy for mitigating climate change. Such technology will be important in building public confidence regarding the safety and security of carbon capture and storage sites.     

The kin recognition system of carpenter ants (Camponotus spp.)

Summary The phenotypic cues that provide for rejection of non-nestmates by workers of the ant genus Camponotus could derive from any or all of four sources: (1) environmental odors; (2) the individual's own genetically-determined recognition pheromones or discriminators; (3) a gestalt or mixture of transferable discriminators, produced by each nestmate and absorbed by all; and/or (4) the discriminators of the queen applied to all nestmates. To test these hypotheses, four series of small experimental colonies were created: inter- and intraspecific mixed colonies containing queens, queenless worker groups, and pairs of worker groups between which a single queen was repeatedly switched. Intraspecific mixed colonies and queenless groups were further divided into groups receiving different diets. Aggression of workers in 165 experimental colonies was assayed in a total of 4064 neutral arena tests. Workers adopted into inter- and intraspecific mixed colonies with queens were highly aggressive to unfamiliar kin from pure colonies, independent of diet and of the proportion of different kin groups in the colony. However, queenless workers exhibited less aggression to unfamiliar kin than to non-kin, demonstrating the existence of worker discriminators. Diet differences slightly enhanced aggression among unfamiliar queenless kin. Non-kin sharing a switched queen were as unaggressive to one another as were sisters. The ability to adopt queenless workers between colonies gradually declined over 1–2 wks following their emergence from pupae. We propose a hierarchy of importance of cue sources in determining nestmate discrimination in small Camponotus colonies: Queen discriminators> worker discriminators>environmental cues. A flow-diagram model of social insect kin recognition, based on the phenotype matching concept of Holmes and Sherman (1983), is discussed.