Variations in pesticide leaching related to land use, pesticide properties, and unsaturated zone thickness

Pesticide leaching through variably thick soils beneath agricultural fields in Morgan Creek, Maryland was simulated for water years 1995 to 2004 using LEACHM (Leaching Estimation and Chemistry Model). Fifteen individual models were constructed to simulate five depths and three crop rotations with associated pesticide applications. Unsaturated zone thickness averaged 4.7 m but reached a maximum of 18.7 m. Average annual recharge to ground water decreased from 15.9 to 11.1 cm as the unsaturated zone increased in thickness from 1 to 10 m. These point estimates of recharge are at the lower end of previously published values, which used methods that integrate over larger areas capturing focused recharge in the numerous detention ponds in the watershed. The total amount of applied and leached masses for five parent pesticide compounds and seven metabolites were estimated for the 32-km2 Morgan Creek watershed by associating each hectare to the closest one-dimensional model analog of model depth and crop rotation scenario as determined from land-use surveys. LEACHM parameters were set such that branched, serial, first-order decay of pesticides and metabolites was realistically simulated. Leaching is predicted to be greatest for shallow soils and for persistent compounds with low sorptivity. Based on simulation results, percent parent compounds leached within the watershed can be described by a regression model of the form e(-depth) (a ln t1/2-b ln K OC) where t1/2 is the degradation half-life in aerobic soils, K OC is the organic carbon normalized sorption coefficient, and a and b are fitted coefficients (R2 = 0.86, p value = 7 x 10(-9)).     

Spermiogenesis and spermatozoa in the relict bivalve genus Neotrigonia: relevance to trigonioid relationships,particularly Unionoidea

Spermiogenesis and spermatozoa in the relict trigonioid genus Neotrigonia are examined ultrastructurally. Mature Neotrigonia spp. spermatozoa exhibit the following features: (1) a blunt-conical nucleus; (2) an acrosomal complex composed of discoidal vesicles (9 to 15) arranged as a thin layer over the nuclear apex; (3) five (rarely four) spherical mitochondria positioned in depressions at the base of the nucleus; (4) proximal and distal centrioles (surrounded by the mitochondria); (5) a satellite complex anchoring the distal centriole and flagellum to the plasma membrane; and (6) a single flagellum. Spermatozoa of unionoids examined to date (Unionidae and Hyriidae only) exhibit similar features, including a nucleus with a blunt apex capped by a thin acrosomal complex (showing up to three vesicles). Among the Bivalvia, only Neotrigonia spp. and unionoid sperm possess an acrosomal complex composed of multiple vesicles. These data suggest that the Trigonioidea and Unionoidea are phylogenetically linked, but further work particularly on primitive unionoids is required to determine if this relationship is one of common ancestry or whether the Unionoidea have in fact been derived from the Trigonioidea.     

Exploring metapopulation-scale suppression alternatives for a global invader in a river network experiencing climate change

Invasive species can dramatically alter ecosystems, but eradication is difficult, and suppression is expensive once they are established. Uncertainties in the potential for expansion and impacts by an invader can lead to delayed and inadequate suppression, allowing for establishment. Metapopulation viability models can aid in planning strategies to improve responses to invaders and lessen invasive species’ impacts, which may be particularly important under climate change. We used a spatially explicit metapopulation viability model to explore suppression strategies for ecologically damaging invasive brown trout (Salmo trutta), established in the Colorado River and a tributary in Grand Canyon National Park. Our goals were to estimate the effectiveness of strategies targeting different life stages and subpopulations within a metapopulation; quantify the effectiveness of a rapid response to a new invasion relative to delaying action until establishment; and estimate whether future hydrology and temperature regimes related to climate change and reservoir management affect metapopulation viability and alter the optimal management response. Our models included scenarios targeting different life stages with spatially varying intensities of electrofishing, redd destruction, incentivized angler harvest, piscicides, and a weir. Quasi-extinction (QE) was obtainable only with metapopulation-wide suppression targeting multiple life stages. Brown trout population growth rates were most sensitive to changes in age 0 and large adult mortality. The duration of suppression needed to reach QE for a large established subpopulation was 12 years compared with 4 with a rapid response to a new invasion. Isolated subpopulations were vulnerable to suppression; however, connected tributary subpopulations enhanced metapopulation persistence by serving as climate refuges. Water shortages driving changes in reservoir storage and subsequent warming would cause brown trout declines, but metapopulation QE was achieved only through refocusing and increasing suppression. Our modeling approach improves understanding of invasive brown trout metapopulation dynamics, which could lead to more focused and effective invasive species suppression strategies and, ultimately, maintenance of populations of endemic fishes.     

Nutrient processing capacity of a constructed wetland in western Ireland

In Ireland, constructed wetland systems are increasingly being used to perform tertiary treatment on municipal waste effluent from small towns and villages located in areas whose receiving waters are deemed sensitive. The bedrock formation in the west of Ireland is primarily karst limestone and where the overburden-soil cover is very shallow, such waters are highly sensitive to pollution sources, as little or no natural attenuation and/or treatment will occur. Constructed wetland technology has been seen to offer a relatively low-cost alternative to the more conventional tertiary treatment technologies, particularly when dealing with low population numbers in small rural communities. This paper examines the waste treatment performance, in terms of nutrient (P and N) reduction, of a recently constructed surface-flow wetland system at Williamstown, County Galway, Ireland. Performance evaluation is based on more than two years of water quality and hydrological monitoring data. The N and P mass balances for the wetland indicate that the average percentage reduction over the two-year study period is 51% for total N and 13% for total P. The primary treatment process in the wetland system for suspended solids (between 84 and 90% reduction), biological oxygen demand (BOD) (on average, 49% reduction), N, and P is the physical settlement of the particulates. However, the formation of algal bloom during the growing season reduces the efficiency of the total P removal.     

The mimetic repertoire of the spotted bowerbird <Emphasis Type="Italic">Ptilonorhynchus maculatus</Emphasis>

Although vocal mimicry in songbirds is well documented, little is known about the function of such mimicry. One possibility is that the mimic produces the vocalisations of predatory or aggressive species to deter potential predators or competitors. Alternatively, these sounds may be learned in error as a result of their acoustic properties such as structural simplicity. We determined the mimetic repertoires of a population of male spotted bowerbirds Ptilonorhynchus maculatus, a species that mimics predatory and aggressive species. Although male mimetic repertoires contained an overabundance of vocalisations produced by species that were generally aggressive, there was also a marked prevalence of mimicry of sounds that are associated with alarm such as predator calls, alarm calls and mobbing calls, irrespective of whether the species being mimicked was aggressive or not. We propose that it may be the alarming context in which these sounds are first heard that may lead both to their acquisition and to their later reproduction. We suggest that enhanced learning capability during acute stress may explain vocal mimicry in many species that mimic sounds associated with alarm.     

Thermochemical pretreatment of meat and bone meal and its effect on methane production

Since the solubilization of meat and bone meal (MBM) is a prerequisite in many MBM disposal approaches, enhancement of the solubilization by means of thermochemical pretreatment was investigated in this study at two temperatures (55°C and 131°C) and six sodium hydroxide (NaOH) concentrations (0, 1.25, 2.5, 5, 10 and 20 g/L). The MBM volatile solid (VS) reduction ratio was up to 66% and 70% at 55°C and 131°C, respectively. At the same temperature, the VS reduction ratio increased with the increase in the dosage of NaOH. The study on the methane (CH₄) production potential of pretreated MBM shows that the addition of NaOH at 55°C did not cause the inhibition of the succeeding CH₄ production process. However, CH₄ production was inhibited by the addition of NaOH at 131°C. The CH₄ production potential was in the range of 389 to 503 mL CH₄/g VS MBM and 464 to 555 mL CH₄/g VS MBM at 55°C and 131°C, respectively.     

Fossil fuel divestment: implications for the future of sustainability discourse and action within higher education

This paper provides a critical overview and analysis of the student-led fossil fuel divestment (FFD) movement and its impact on sustainability discourse and actions within US higher education. Analysing higher education institutes’ (HEIs) divestment press releases and news reports shows how institutional alignment with cultures of sustainability and social justice efforts played key roles in HEIs’ decisions to divest from fossil fuels. Key stated reasons for rejection were: minimal or unknown impact of divestment, risk to the endowment, and fiduciary duty. Participant observation and interviews with protagonists reveal the intricate power structures and vested business interests that influence boardroom divestment decision-making. While some HEIs embrace transformative climate actions, we contend that higher education largely embraces a business-as-usual sustainability framework characterised by a reformist green-economy discourse and a reluctance to move beyond business-interest responses to climate politics. Nonetheless, the FFD movement is pushing HEIs to move from compliance-oriented sustainability behaviour towards a more proactive and highly politicised focus on HEIs’ stance in the modern fossil fuel economy. We offer conceptual approaches and practical directions for reorienting sustainability within HEIs to prioritise the intergenerational equity of its students and recognise climate change as a social justice issue. Fully integrating sustainability into the core business of HEIs requires leadership to address fundamental moral questions of both equity and responsibility for endowment investments. We contend that HEIs must re-evaluate their role in averting catastrophic climate change, and extend their influence in catalysing public climate discourse and actions through a broader range of external channels, approaches, and actors.     

Local and regional air pollution in Ireland during an intensive aerosol measurement campaign

An intensive two month measurement campaign has been performed during a two year study of major component composition of urban PM10 and PM2.5 in Ireland (J. Yin, A. G. Allen, R. M. Harrison, S. G. Jennings, E. Wright, M. Fitzpatrick, T. Healy, E. Barry, D. Ceburnis and D. McCusker, Atmos. Res., 2005, 78(3-4), 149-165). Measurements included size-segregated mass, soluble ions, elemental carbon (EC) distributions, fine and coarse fraction organic carbon (OC) and major gases along with standard meteorological measurements. The study revealed that urban emissions in Ireland had mainly a local character and therefore were confined within a limited area of 20-30 km radius, without significantly affecting regional air quality. Gaseous measurements have shown that urban emissions in Ireland had clear, but fairly limited influence on the regional air quality due to favorable mixing conditions at higher wind speeds, in particular from the western sector. Size-segregated mass and chemical measurements revealed a clear demarcation size between accumulation and coarse modes at about 0.8 microm which was constant at all sites. Carbonaceous compounds at the urban site accounted for up to 90% of the particle mass in a size range of 0.066-0.61 microm. Nss SO4(2-) concentrations in PM2.5 were only slightly higher at the urban site compared to the rural or coastal sites, while NO3- and NH4+ concentrations were similar at the urban and coastal sites, but were a factor of 2 to 3 higher than at the rural site. OC was highly variable between the sites and revealed clear seasonal differences. Natural or biogenic OC component accounted for <10% in winter and up to 30% in summer of the PM2.5 OC at urban sites. A contribution of biogenic OC component to PM2.5 OC mass at rural site was dominant.     

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

Groundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a statistical framework and hydrogeological techniques. Nitrate–N (NO₃-N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO₃-N concentration in shallow groundwater (<5 m below ground level) generated from an agricultural point source on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (K_sat) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6 mg NO₃-N L⁻¹ showed, when assessed individually in a step wise procedure, K_sat was significantly related to groundwater NO₃-N concentration. Distance of the point dirty water pollution source becomes significant when included with K_sat in the model. The model relationships show areas with higher K_sat values have less time for denitrification to occur, whereas lower K_sat values allow denitrification to occur. Areas with higher permeability transport greater NO₃-N fluxes to ground and surface waters. When the distribution of Cl⁻ was examined by the model, K_sat and ground elevation had the most explanatory power but K_sat was not significant pointing to dilution having an effect. Areas with low NO₃ concentration and unaffected Cl⁻ concentration points to denitrification, low NO₃ concentration and low Cl⁻ chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO₃-N was significantly (P < 0.05) related to groundwater N₂/Ar ratio, redox potential (Eh), dissolved O₂ and N₂ and was close to being significant with N₂O (P = 0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors.