Wet Weather Periods Research Articles

Removal of alkylphenols and polybromodiphenylethers by a biofiltration treatment plant during dry and wet-weather periods

This paper investigates the occurrence of alkylphenols (APs) and polybromodiphenylethers (PBDEs) in raw wastewater during dry and wet-weather periods, and their removal by physico-chemical lamellar settling and biofiltration techniques. Due to in-sewer deposit erosion and, to a lesser extent, to external inputs, raw effluents exhibit from 1.5 to 5 times higher AP and PBDE concentrations during wet periods compared with dry ones. The lamellar settler obtains high removal of APs and PBDEs under both dry and wet-weather flows (>53% for Σ(6)AP and >89% for Σ(4)PBDE), confirming the insensitivity of this technique to varying influent conditions. Indeed, despite the higher pollutant concentrations observed in raw effluents under wet-weather flows, adjusting the addition of coagulant-flocculent allows for efficient removal. By combining physical and biological processes, the biofiltration unit treats nutrient pollution, as well as Σ(6)AP and Σ(4)PBDE contamination (58 ± 5% and 75 ± 6% respectively). Although the operating conditions of the biofiltration unit are modified during wet periods, the performance in nutrient pollution, APs and light PBDE congeners remains high. Nevertheless, lower efficiency has been noted in nitrogen pollution, i.e. no denitrification occurs, and BDE-209 (not removed during wet-weather periods). In conclusion, this study demonstrates that the combination of both techniques treats AP and PBDE pollution efficiently during dry periods, but that they are also suitable for stormwater treatment.

Observations of turbidity in the Thames Estuary, United Kingdom

AbstractTwo years of data of water level, salinity and turbidity have been analysed to understand the response of the estuarine turbidity maximum in the Thames to variations in tidal range and freshwater flow. We show the increase in turbidity in spring, together with a sudden decrease in autumn after fluvial flooding. In order to try to understand the mechanisms, we also present data from individual tides. During dry periods, there is a period of slack water around high tide when settling occurs. There is little equivalent settling at low tide, nor is there any significant settling during wet weather periods, pointing to the importance of tidal asymmetry at certain times of year. We also present an empirical relationship between peak tidal water level and turbidity during flood tides, which clearly shows the greater landward transport of sediment under spring tides, although this is moderated by the availability of erodible material.

Assessing the Severity of Rainfall-Derived Infiltration and Inflow and Sewer Deterioration Based on the Flux Stability of Sewage Markers

This study investigated the flux stability of select chemical and biological sewage markers, including caffeine, total nitrogen (TN), total suspended solids (TSS), E. coli, and enterococci, and their suitability in assessing the severity of rainfall-derived infiltration and inflow (RDII) in a residential sewershed. To quantify and compare marker flux stability, concentrations of the candidate markers in two dry-weather periods were determined and the one-day lag autocorrelation coefficients (r) of their mass fluxes were calculated. TN (r = 0.82-0.88) exhibited higher and more consistent flux stability than TSS (r = 0.49-0.82), caffeine (r = 0.56-0.58), E. coli (r = 0.36-0.87), and enterococci (by culture; r = 0.40-0.52), all of which except enterococci by qPCR (r = -0.10-0.21) showed significant autocorrelation. Sewage flows and marker concentrations were also monitored in two wet-weather periods, and the severity of RDII (R(RDII)) were calculated using either flow measurements or marker concentrations independently. Corresponding to its outstanding flux stability, R(RDII) values estimated by TN predicted all severe RDII instances and gave the highest and most consistent correlation (r = 0.74-0.78) among the different sewage markers. Overall, the study illustrated the feasibility of using the flux stability of sewage markers in assessing the severity of RDII and thereby deterioration levels in sewer systems.

Uncertainty estimation of a complex water quality model: The influence of Box–Cox transformation on Bayesian approaches and comparison with a non-Bayesian method

In urban drainage modelling, uncertainty analysis is of undoubted necessity. However, uncertainty analysis in urban water-quality modelling is still in its infancy and only few studies have been carried out. Therefore, several methodological aspects still need to be experienced and clarified especially regarding water quality modelling. The use of the Bayesian approach for uncertainty analysis has been stimulated by its rigorous theoretical framework and by the possibility of evaluating the impact of new knowledge on the modelling predictions. Nevertheless, the Bayesian approach relies on some restrictive hypotheses that are not present in less formal methods like the Generalised Likelihood Uncertainty Estimation (GLUE). One crucial point in the application of Bayesian method is the formulation of a likelihood function that is conditioned by the hypotheses made regarding model residuals. Statistical transformations, such as the use of Box–Cox equation, are generally used to ensure the homoscedasticity of residuals. However, this practice may affect the reliability of the analysis leading to a wrong uncertainty estimation. The present paper aims to explore the influence of the Box–Cox equation for environmental water quality models. To this end, five cases were considered one of which was the “real” residuals distributions (i.e. drawn from available data). The analysis was applied to the Nocella experimental catchment (Italy) which is an agricultural and semi-urbanised basin where two sewer systems, two wastewater treatment plants and a river reach were monitored during both dry and wet weather periods. The results show that the uncertainty estimation is greatly affected by residual transformation and a wrong assumption may also affect the evaluation of model uncertainty. The use of less formal methods always provide an overestimation of modelling uncertainty with respect to Bayesian method but such effect is reduced if a wrong assumption is made regarding the residuals distribution. If residuals are not normally distributed, the uncertainty is over-estimated if Box–Cox transformation is not applied or non-calibrated parameter is used.

Factors Affecting the Quality of the Plant Influent and Its Suitability for Prefermentation and the Biological Nutrient Removal Process

To understand wastewater quality transformations in the sewer system, a full-scale study focused on the characteristics of the influent wastewater in a middle-sized wastewater-treatment plant receiving only municipal sewage. The objective was to identify conditions in which prefermentation prior to the biological nutrient removal (BNR) process would be useful. Prefermentation aims at increasing the fraction of readily biodegradable organic matter in the wastewater. A correlation between weather conditions and the presence of readily biodegradable organic matter in the feed wastewater was found, but contrary to the expectations, wet weather periods deteriorated the quality of the feed water more than the cold period. Moreover, influent load showed seasonal variation which changes in discharged wastewater could not explain. During the warm water period, significant biological oxidation and nitrogen removal took place in the sewer system, but the plant influent water contained readily biodegradable organic m...

Seasonal influence on urban dust PAH profile and toxicity in Sydney, Australia

Road dust is one of the major threats to the urban environment due to wash-off of dust to the surrounding catchments during wet weather period. The dust contains wide range of toxic contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHS) and endocrine disrupting chemicals. Among the toxic contaminants, PAHs are of environmental concern due to their potential carcinogenic and mutagenic effect besides endocrine disruptive behaviour. Eighteen road dust samples from Sydney were collected in different time periods for a year and analysed for 16 US EPA PAHS. Total PAHs content range in the dust was 9-105 pg/g. Total and individual PAH contents were highest in the finest size fraction (<75 microm) and in winter compared to the other seasons. The PAH profiles in the different particle sizes were similar but different between the four seasons. The concentrations of higher molecular weight PAHS (4- and 5-rings) were much greater than the concentrations of lower molecular weight PAHs (2- and 3-rings). Toxicity equivalency factor application showed that the longer the dry weather period the higher the total PAHs content and toxicity in the dust.

Receiving water body quality assessment: an integrated mathematical approach applied to an Italian case study

This study presents a basin-scale approach to the analysis of receiving water body quality considering both point and non-point pollution sources. In particular, this paper describes an extensive data gathering campaign carried out in the Nocella catchment, which is an agricultural and semi-urbanised basin located in Sicily, Italy. Two sewer systems, two wastewater treatment plants and a river reach were monitored during both dry and wet weather periods. A mathematical model of the entire integrated system was also created. Specifically, a detailed modelling approach was developed by employing three well known models: Storm Water Management Model, GPS-X and Soil and Water Assessment Tool. The study proposed a comprehensive modelling approach to analyse the importance of diffuse and concentrated polluting sources on receiving water quality. The study demonstrated that point pollution loads can be more influential during wet periods by an order of magnitude compared with the dry weather period. In the long term, diffuse and point pollution sources were demonstrated to affect river quality and they have both to be considered. The use of the proposed integrated model-based approach may support water managers in decision making about which strategies should be preferred with the aim of water quality preservation.

Historic variability in fire-generated landscape heterogeneity of subalpine forests in the Canadian Rockies

Question: This study evaluates historical changes in landscape structure and heterogeneity in subalpine forests. We use response to severe fires in 2001 and 2003, along with historical reconstructions to examine crown-fire effects on landscape heterogeneity and to assess, comparatively, effects of fire exclusion management in the 20th century. Location: Subalpine forests of Kootenay National Park (KNP), Canadian Rockies. Methods: Using a landscape-level model based on a fire-origin stand age map, we reconstructed decadal burned areas within the landscape for 1750-2000 (forming reconstructed landscapes). Landscape pattern was analysed for each reconstructed landscape map, and we compared landscape pattern indices (total area, number of patches, mean patch area, patch area variation, largest patch index, edge density, perimeter–area ratio, landscape shape index) with those in 2005 after recent large fires. Results: After large fires in 1926, connectivity of the KNP landscape increased and its diversity was quite low. After 2001 and 2003 fires, the post-fire landscape of 2005 was highly heterogeneous in terms of size, variation, edge density and perimeter–area ratio of the remnant forest patches. Since the decline in occurrence of large fires after 1926 reflected a period of wet weather, fuel build-up resulting from landscape homogenization within the 20th century landscape could not be attributed solely to fire exclusion. This period without fires greatly enhanced connectivity of late-successional forests that finally burned in 2001/2003, but connectivity was within the historical range for these forests. The gradual increase in stand connectivity before recent large fires may indicate that fire exclusion was less responsible than often believed for fuel build-up in these fire-susceptible older forests. Conclusions: The large fires at the beginning of the 21st century are within the natural range of disturbances for this landscape, and do not stand out as “human-induced disasters” in their effects on landscape patterns. Such stochastic large disturbances contribute to maintenance of highly heterogeneous landscape structure, which is important for many taxa and natural ecological processes. Identifying future probability of such large disturbances and their ecological roles should be incorporated into management of these dynamic, disturbance-prone systems.

First Report of Marasmiellus mesosporus Causing Marasmiellus Blight on Seashore Paspalum.

Seashore paspalum (Paspalum vaginatum Sw.) is a newly cultivated C4 turfgrass that has exceptional salinity tolerance and is highly suited for use on golf courses in coastal areas. In October 2008 and June 2009, circular patches of blighted seashore paspalum ranging from 30 cm to >3 m in diameter were observed in fairways, tees, and roughs established with 'Supreme' seashore paspalum at Roco Ki Golf Club in Macao, Dominican Republic. Affected patches were initially chlorotic followed by reddish brown necrosis of leaves and leaf sheaths. Reddish brown-to-gray lesions were also observed on leaf sheaths during the early stages of necrosis. During periods of wet or humid weather from June through October, basidiocarps were produced on necrotic plant tissue and identified as Marasmiellus mesosporus Singer (2). Three isolates were obtained by plating symptomatic leaf sheaths that were surface sterilized with a 0.5% NaOCl solution on potato dextrose agar amended with 50 ppm each of streptomycin, chloramphenicol, and tetracycline (PDA+++). Sequences of the internal transcribed spacer (ITS) region of rDNA, obtained from these three isolates and three stipes of basidiocarps, were identical to each other and 99% similar to a M. mesosporus sequence deposited in the NCBI database (Accession No. AB517375). To confirm pathogenicity, a M. mesosporus isolate obtained from symptomatic plant tissue was inoculated onto 6-week-old P. vaginatum ('Seaspray') planted (0.5 mg seed/cm2) in 10-cm-diameter pots containing a mixture of 80% sand and 20% reed sedge peat. Two weeks prior to inoculation, the isolate was grown on a sterilized mixture of 100 cm3 of rye grain, 4.9 ml of CaCO3, and 100 ml of water. Infested grains were placed 0.5 cm below the soil surface for inoculation. Pots were inoculated with five infested grains or five sterilized, uninfested grains with three replications of each treatment. After inoculation, pots were placed in a growth chamber with a 12-h photoperiod set to 30°C during the day and 26°C at night. Approximately 20% of plants in inoculated pots were necrotic 7 days postinoculation and this increased to 75% by 21 days postinoculation. Diseased plants in inoculated pots exhibited symptoms similar to those observed in the field. Leaves were initially chlorotic with brown lesions on lower leaf sheaths and eventually turned necrotic, reddish brown, and collapsed. Pots receiving uninfested grains were healthy and showed no symptoms on all rating dates. At 21 days postinoculation, basidiocarps were observed emerging from three colonized plants at the base of the oldest leaf sheath near the crown. Three reisolations were made on PDA+++ from stem lesions surface sterilized with a 0.5% NaOCl solution. All reisolations were confirmed as M. mesosporus by culture morphology and ITS sequence data. M. mesosporus was previously reported causing disease on American beachgrass (Ammophila breviligulata Fernald) in North Carolina (1) and recently in Japan (3). The pathogen was initially placed in the genus Marasmius and reported as the cause of the disease Marasmius blight (1). Subsequent morphological observation found that the pathogen belonged in the genus Marasmiellus (2). To our knowledge, this is the first report of M. mesosporus causing Marasmiellus blight on seashore paspalum, a high-amenity turfgrass.

Contributions of wastewater, runoff and sewer deposit erosion to wet weather pollutant loads in combined sewer systems

An observatory of urban pollutants was created in Paris for the purpose of assessing the dynamics of wastewater and wet weather flow (WW and WWF) pollutant loads within combined sewers. This observatory is composed of six urban catchments, covering land areas ranging in size from 42 ha to 2581 ha. For a wide array of parameters including total suspended solids (TSS), chemical and biochemical oxygen demand (COD and BOD 5), total organic carbon (TOC), total Kjeldahl nitrogen (TKN), heavy metals (Cu and Zn) and polycyclic aromatic hydrocarbons (PAHs), this article is intended to evaluate the contributions of wastewater, runoff and in-sewer processes to WWF pollutant loads through the use of an entry–exit mass balance approach. To achieve this objective, a total of 16 rain events were sampled on these sites between May 2003 and February 2006. This study has confirmed that at the considered catchment scale (i.e. from 42 ha to 2581 ha) the production and transfer processes associated with WWF pollutant loads do not vary with basin scale. Entry–exit chemical mass balances over all catchments and for a large number of rain events indicate that wastewater constitutes the main source of organic and nitrogenous pollution, while runoff is the predominant source of Zn. For Cu, PAHs and TSS, the calculation underscores the major role played by in-sewer processes, specifically by sediment erosion, as a source of WWF pollution. A significant loss of dissolved metals was also observed during their transfer within the sewer network, likely as a consequence of the adsorption of dissolved metals on TSS and/or on sewer deposits. Moreover, the nature of eroded particles was examined and compared to the various sewer deposits. This comparison has highlighted that such particles exhibit similar organic and PAH contents to those measured in the organic layer, thus suggesting that the deposit eroded during a wet weather period is organic and of a nature comparable to the organic layer. Despite the extent of initial field investigations, no organic deposit was observed to be present on sewer lines within the catchments, which implies that this organic deposit is probably present in another form or to be found elsewhere in the main trunks.

Validating a novel allele of viviparous-1 (Vp-1Bf) associated with high seed dormancy of Chinese wheat landrace, Wanxianbaimaizi

Pre-harvest sprouting (PHS) can easily lead to yield losses of wheat and downgrading of grain quality in wheat-growing areas where long periods of wet weather occur frequently during harvest. As a main component of PHS, seed dormancy is often evaluated by germination index (GI). Previous researches have proved allelic variations of Vp-1B to have a close relationship with dormancy of white-grained wheat. In the present study, a mapping population covering 157 recombinant inbred lines was developed from a cross of two white-grained varieties, Wanxianbaimaizi and Jing411. Wanxianbaimaizi is a strongly dormant landrace carrying a novel allele, Vp-1Bf; whereas, Jing411 is a non-dormant variety with wild allele, Vp-1Ba. Our objective was to validate the association between the novel allele and seed dormancy using the population. The results of sequences alignment indicated an insertion of 193 bp and a deletion of 109 bp were both identified in the novel allele, respectively, compared with wild allele in Jing411. Here, the deletion was first detected. As for lines possessing Vp-1Ba, the average GI value was 0.584, significantly higher than that of lines holding Vp-1Bf. Among three genotypes, Vp-1Bf allele was generally corresponded to the lowest average of GI value (0.195), and the highest dormancy; in addition, lines with heterozygous genotype often showed intermediate GI value (0.356). Of 92 RILs with Vp-1Ba, over 70 lines showed higher GI value (>0.40), and only about 7 lines had lower GI value ( 0.60). The result of composite interval mapping revealed that a major QTL for seed dormancy was flanked by Xwmc446 and Vp1 on 3BL, which was proximal to Vp1 (7.6–8.4 cM). The locus could explain 24.6–40.7% of total phenotypic variation across three crop seasons. The above results could confirm that the novel allele had a striking association with high seed dormancy, and may be useful for improving PHS tolerance of white-grained wheat.

Rapid channel response to variability in sediment supply: Cutting and filling of the Tarndale Fan, Waipaoa catchment, New Zealand

In the headwaters of the Waipaoa catchment, fluvio-mass movement gully complexes are currently significant contributors of sediment, delivery of which is buffered by fans which have developed in the small tributaries that lead from the gully complexes. Biannual channel cross-section surveys made since 1983 show seasonal aggradation / incision cycles; channels generally incise in summer and infill during the winter months. This seasonal pattern of cutting and filling is driven by variations in sediment supply from the gully complexes. In this paper, to better understand patterns and processes of sediment delivery at the top of the sediment cascade, we examine cut and fill cycles on the ~ 11 ha Tarndale Fan over a two and a half year period. Analysis of sequential DEMs compiled from survey data obtained between December 2004 and August 2007 indicates cutting and filling may involve up to 47,000 tonnes of sediment over as little as three months. During discrete severe rainstorm and/or wet weather periods, mass movements in the gully complex are enhanced and contribute large quantities of sediment to the fan, via debris flows and landslides, which infill channels. During drier periods, mass movement activity is inhibited and runoff incises the feeder channels.

Quantification of diffuse and concentrated pollutant loads at the watershed-scale: an Italian case study

In this study, diffuse and point source pollutant loads were evaluated using an Italian case study: the Nocella catchment, which has been subject to extensive monitoring. The Nocella catchment is located in Sicily (Italy) and has an area of about 60 km(2). The river receives wastewater and stormwater from two urban areas drained by combined sewers. The two sewer systems, two wastewater treatment plants and a river reach were monitored during both dry and wet weather periods. Thereafter, an integrated catchment-scale model was applied to simulate point pollutant sources, i.e., pollution coming from the urban drainage system, and nonpoint pollutant sources, i.e., pollution coming from agricultural and wildlife activities. Different models were combined and long-term simulations were carried out in order to reconstruct the total pollutant loads discharged into the receiving water body and identify the roles of the different pollutant sources. This study demonstrates the complexity of water quality assessment in partially urbanised natural basins where neither point nor nonpoint sources can be neglected. Point sources are mainly responsible for acute oxygen demanding polluting impact during wet weather periods, and both point and nonpoint sources are responsible for the impact of nutrients on the receiving water body.

Simulation of heat export by rainfall–runoff from a paved surface

Summary The overall goal of our research has been to create a hydro-thermal model to quantify the impact on stream temperature of urban development in watersheds of cold-water streams. In this paper we describe a significant component of that modeling effort, namely a sub-model for predicting storm water runoff rates and temperatures from paved surfaces during a rainfall event. An unsteady 1-D model has been formulated from basic principles of heat transfer and runoff processes on planar impervious surfaces for both dry- and wet-weather periods. The model predicts runoff flow rates and temperatures as a function of both distance and time on a paved surface, taking into account the magnitude of the radiative, convective, evaporative and conductive heat fluxes at the surface. It also predicts the ‘total heat export’ for an event, which is defined as the heat contained in the runoff above a reference temperature. A case study is presented in which the model is applied to a parking lot, and simulated runoff flow, temperature, and heat export closely match observations of these quantities for an early-evening rainfall event in August. A sensitivity study was performed to investigate to which extent heat export is affected by antecedent pavement temperature, characteristics of the rainfall event, and physical parameters of the paved surface. It was found that heat export is more sensitive to rainfall intensity, rainfall duration, and antecedent pavement temperature than the physical properties (slope, roughness, and length) of the paved surface. An increase in rainfall duration increases the total event heat export, especially for high-intensity events. Heat exchange with the atmosphere typically reduces runoff temperature and heat export versus a case in which atmospheric heat fluxes are neglected, with greater effect occurring as rainfall intensity decreases.

Priority pollutants in wastewater and combined sewer overflow

Implementation of the European Water Framework Directive and its affiliated directives requires Member States to improve their understanding of priority pollutants (PPs) in urban areas and obviously within wastewater systems. As a direct consequence, this study is intended to furnish data on both PP occurrence and the significance of concentrations in wastewater during dry and wet periods within combined sewers. Various sampling sites within the Paris combined sewer network were selected; for each sample, a total of 66 determinants, including metals, polycyclic aromatic hydrocarbons (PAHs), pesticides, organotins, volatile organic compounds, chlorobenzenes, phthalates and alkylphenols, were analysed. A broad range of PPs was observed in wastewater during dry as well as wet weather periods. Of the 66 elements investigated, 33 and 40 priority substances could be observed in raw sewage and wet weather effluent, respectively. As expected, a majority of metals were present in all samples, reflecting their ubiquitous nature. For both periods, chlorobenzenes and most of the pesticides always remained below the limit of quantification, while the majority of other organic pollutants assessed were identified within the µg l − 1 range. As highlighted by the larger number of substances detected in wet weather samples and the significance of their concentrations, runoff via atmospheric inputs and/or surface leaching was found to induce a wider range of PPs ( n = 40) and lead to higher concentrations of certain metals, PAHs, pesticides and other individual compounds. The data generated during this survey, which constitutes one of the first studies conducted in Europe to report concentrations for a variety of priority substances in wastewater within combined sewers, may be used in the future to identify PPs of potential significance for dry and wet weather periods and targeted for further investigation.

Ground surface temperature simulation for different land covers

Summary A model for predicting temperature time series for dry and wet land surfaces is described, as part of a larger project to assess the impact of urban development on the temperature of surface runoff and coldwater streams. Surface heat transfer processes on impervious and pervious land surfaces were investigated for both dry and wet weather periods. The surface heat transfer equations were combined with a numerical approximation of the 1-D unsteady heat diffusion equation to calculate pavement and soil temperature profiles to a depth of 10 m. Equations to predict the magnitude of the radiative, convective, conductive and evaporative heat fluxes at a dry or wet surface, using standard climate data as input, were developed. A model for the effect of plant canopies on surface heat transfer was included for vegetated land surfaces. Given suitable climate data, the model can simulate the land surface and sub-surface temperatures continuously throughout a six month time period or for a single rainfall event. Land surface temperatures have been successfully simulated for pavements, bare soil, short and tall grass, a forest, and two agricultural crops (corn and soybeans). The simulations were run for three different locations in US, and different years as imposed by the availability of measured soil temperature and climate data. To clarify the effect of land use on surface temperatures, the calibrated coefficients for each land use and the same soil coefficients were used to simulate surface temperatures for a six year climate data set from Albertville, MN. Asphalt and concrete give the highest surface temperatures, as expected, while vegetated surfaces gave the lowest. Bare soil gives surface temperatures that lie between those for pavements and plant-covered surfaces. The soil temperature model predicts hourly surface temperatures of bare soil and pavement with root–mean–square errors (RMSEs) of 1–2 °C, and hourly surface temperatures of vegetation-covered surfaces with RMSEs of 1–3 °C.

Tillage effects on N2O emission from soils under corn and soybeans in Eastern Canada

The ways in which agricultural soils are managed influence the production and emission of nitrous oxide (N2O). A field study was undertaken in 2003, 2004, and 2005 to quantify and evaluate N2O emission from tilled and no-till soils under corn (Zea maysL.) and soybeans (Glycine max L. Merr) in Ontario. Overall, N2O emission was lowest in 2003, the driest and coolest of the 3 yr. In 2004, the significantly larger annual N2O emission from no-till soils and soils under corn was attributed to an episode of very high N2O emission following the application of fertilizer during a period of wet weather. That the N loss by N2O emission occurred only in no-till soils and was large and long-lasting (~4 wk) confirms the strong effect that management has in reducing fertilizer N losses. In 2005, tilled soils had significantly larger N2O emission than no-till soils, most of which was emitted before the end of June. Because the tilled soils were better aerated , nitrification was likely the primary process contributing to the larger emission. Relatively low N2O emission from soybeans suggests biological N fixation does not appear to contribute substantially to the annual N2O emission. Further study of methods to reduce N2O emission in agricultural systems should focus on improving N use efficiency within a particular tillage system rather than looking to differences between tillage systems. Key words: Tillage, corn, soybeans, nitrogen, nitrous oxide, biogenic gas emission, nitrification, denitrification, fertilization

First Report of Curvularia Blight of Zoysiagrass Caused by Curvularia lunata in the United States.

Symptoms of an unknown foliar blight have been observed in zoysiagrass (Zoysia matrella, Z. japonica, and hybrids) landscapes in North Carolina since 2002. Disease activity is most common during spring and summer when temperatures are between 21 and 30°C. Affected leaves initially exhibit small, chocolate brown spots, followed by dieback of leaves from the tips, and eventually blighting of entire tillers. Symptoms appear in small, irregular patches as much as 15 cm in diameter, but numerous patches may coalesce to impact large sections of turf. Infected turf appears tan or brown from a distance, but often turns black during periods of wet or humid weather. Microscopic analysis revealed profuse sporulation of Curvularia spp. on the surface of symptomatic leaves. Leaf sections were surface disinfested in 10% Clorox for 1 to 2 min, blotted dry, then plated on potato dextrose agar (PDA) containing 50 mg/l of tetracycline, streptomycin, and chloramphenicol. Twenty-eight fungal isolates were obtained from six locations. Examination of conidia produced in culture revealed 21 isolates of Curvularia, two isolates of Drechslera, one isolate of Nigrospora, and four unidentified sterile fungi. Curvularia isolates were identified to species on the basis of morphological characteristics (1) and ITS-rDNA sequences. Known isolates of C. eragrostidis, C. geniculata, C. inequalis, C. lunata, C. pallescens, and C. trifolii were obtained from the American Type Culture Collection for comparison. All unknown isolates produced conidia that were characteristic of C. lunata (lacking a protuberant hilum, smooth walled, tri-septate, predominantly curved, and mid- or dark brown, average dimensions 17 to 25 × 8 to 12 μm). Colonies on PDA lacked stroma or the zonate appearance indicative of C. lunata var. aeria. The pathogenicity of C. lunata isolates was tested on zoysiagrass cvs. El Toro (Z. japonica) and Emerald (Z. japonica × matrella). Cores (11.4 cm in diameter) of established zoysiagrass were potted in calcined clay (Turface Allsport; Profile Products LLC, Buffalo Grove, IL), and transferred to a greenhouse where the average temperature was 26°C. Five isolates were selected to represent the geographic range of Curvularia blight in North Carolina, and conidia were produced on PDA under continuous fluorescent illumination. Each isolate was inoculated to one pot of each zoysiagrass variety by spraying with 25 ml of a suspension containing 2 × 105 conidia/ml with an airbrush. Inoculated pots were placed in a sealed, nontransparent plastic container for 48 h at 28°C to encourage infection and then transferred back to the greenhouse bench. Pathogenicity tests were repeated four times over time. Isolates ZFB3 and ZFB28 were most virulent with initial symptoms of foliar dieback appearing within 1 week after inoculation. Continued disease progress resulted in necrosis of the entire plant. Other isolates induced symptoms within 2 to 3 weeks after inoculation; however, disease severity was lower as compared with ZFB3 and ZFB28 throughout each experiment. Cvs. Emerald and El Toro were equally susceptible to infection by C. lunata. To our knowledge, this is the first report of Curvularia blight of zoysiagrass in the United States. This disease was previously described in Japan where it is commonly referred to as 'dog footprint' (3) and Brazil (2).

A case study: delayed failure of a deep cutting in lodgement till

Recent research on the delayed failure of cuttings in clay clearly recognises and predicts progressive delayed failure of deep cuttings. This is due to a combination of strain-softening, weathering, dissipation of negative excess pore water pressure generated at the time of excavation, and frequent occurrence of prolonged periods of wet weather. There have been several slope failures of this kind in Northern Ireland. This paper discusses a case study based on a failure of a deep cutting, excavated at a slope of 1 in 2, on the A1 near Dromore (County Down) in Northern Ireland. The cutting was in lodgement till, a stiff, heavily overconsolidated clay. The failure occurred approximately 30 years after the cutting was excavated, following a prolonged period of heavy rainfall. An analysis of the failure, together with laboratory test data on soil samples taken from the site, confirmed that by using long-term soil strength parameters the factor of safety of this slope was unity. The conclusion of the analysis is that slopes excavated in this soil should be designed (and assessed) on long-term strength parameters.

Pollution en hydrocarbures transitant par temps sec et par temps de pluie dans le réseau d’assainissement unitaire parisien

Click to increase image sizeClick to decrease image sizeThis work, carried out on the phase 2 of the OPUR (Observatory of Urban Pollutants) research programme, aims to study the spatial variability of the aliphatic (AH) and polycyclic aromatic hydrocarbon (PAH) loads within the Parisian combined sewer during dry and wet weather periods. For both periods, investigations reveal a quite homogeneity of the AH and PAH loads between the six urban catchments considered (from 42 to 2 581 ha). This observation mainly suggests that the hydrocarbon loads in dry and wet weather flows do not change in relation to the spatial scale. The second part of this article focused more especially on the transfer of hydrocarbons during wet weather period. Therefore, contributions from wastewater, runoff and in-sewer deposit erosion to the wet weather pollutant loads were assessed. Whatever the site considered the erosion of in-sewer deposits constitute an important source, contributing to 40 and 66% of the total AH and PAH loads, respectively. In the same way, runoff contribute mainly to the AH loads (50%) and to a lesser extent to the PAH loads (17%).