Monitoring of nitrate leaching in sandy soils: comparison of three methods

Proper N fertilizer and irrigation management can reduce nitrate leaching while maintaining crop yield, which is critical to enhance the sustainability of vegetable production on soils with poor water and nutrient-holding capacities. This study evaluated different methods to measure nitrate leaching in mulched drip-irrigated zucchini, pepper, and tomato production systems. Fertigation rates were 145 and 217 kg N ha(-1) for zucchini; 192 and 288 kg N ha(-1) for pepper; and 208 and 312 kg N ha(-1) for tomato. Irrigation was either applied at a fixed daily rate or based on threshold values of soil moisture sensors placed in production beds. Ceramic suction cup lysimeters, subsurface drainage lysimeters and soil cores were used to access the interactive effects of N rate and irrigation management on N leaching. Irrigation treatments and N rate interaction effects on N leaching were significant for all crops. Applying N rates in excess of standard recommendations increased N leaching by 64, 59, and 32%, respectively, for pepper, tomato, and zucchini crops. Independent of the irrigation treatment or nitrogen rate, N leaching values measured from the ceramic cup lysimeter-based N leaching values were lower than the values from the drainage lysimeter and soil coring methods. However, overall nitrate concentration patterns were similar for all methods when the nitrate concentration and leached volume were relatively low.     

A remediation strategy based on active phytoremediation followed by natural attenuation in a soil contaminated by pyrite waste

Phytoremediation of metal-polluted soils can be promoted by the proper use of soil amendments and agricultural practices. A 4-year phytoremediation programme was applied to a site affected by the toxic spill of pyrite residue at Aznalcóllar (Spain) in 1998, contaminated with heavy metals (Zn, Cu, Pb, Cd) and arsenic. This consisted of active phytoremediation, using organic amendments (cow manure and compost) and lime and growing two successive crops of Brassica juncea (L.) Czern., followed by natural attenuation without further intervention. Changes in soil pH, extractable metal and As concentrations, organic carbon content and microbial biomass was evaluated. The initial oxidation of metal sulphides from pyrite residues released soluble metals and reduced soil pH to extremely acidic values (mean 4.1, range 2.0-7.0). The addition of lime (up to 64 t ha(-1)) increased soil pH to adequate values for plant growth, resulting in a significant decrease in DTPA-extractable metal concentrations in all plots. The natural attenuation phase showed also a decrease in extractable metals. Organic treatments increased the soil total organic carbon, which led to higher values of microbial biomass (11.6, 15.2 and 14.9 g kg(-1) TOC and 123, 170 and 275 microg g(-1) biomass-C in control, compost and manure plots, respectively). Active phytoremediation followed by natural attenuation, was effective for remediation of this pyrite-polluted soil.     

A case of ring chromosome 22 with deletion of the 22q13.3 region associated with agenesis of the corpus callosum,fornix and septum pellucidum

We report a 16-week-gestation foetus obtained by voluntary abortion after prenatal diagnosis, in which a ring chromosome 22 was observed with deletion of the 22q13.3 region. A prenatal study of the amniotic fluid by standard chromosome technique with G bands and FISH (fluorescence in situ hybridisation) was performed. After the abortion, the anatomopathological study of the obtained foetus was carried out. Morphological and histological analysis of the foetus did not reveal severe physical abnormalities, although alterations of the nervous system were observed consisting of corpus callosum, fornix and septum pellucidum agenesia. It could be that the genes in this region that were involved in the development of the central nervous system were responsible for the alterations found in the morphological study. The wide range of manifestations observed in patients with this cytogenetic alteration is probably due to size differences in the deleted region. Copyright © 2004 John Wiley & Sons, Ltd.     

Comparison between direct microscopy and flow cytometry for rRNA-based quantification of Candidatus Accumulibacter phosphatis in activated sludge.

A comparison of the quantification of a specific microbial group in activated sludge by fluorescent in-situ hybridization, coupled with either direct microscopic counting or flow cytometry, was performed using an enhanced-biological-phosphorus-removal, sequencing-batch reactor. The population dynamics of Candidatus Accumulibacter phosphatis (Cand. A. phosphatis) was evaluated during two separate runs of the reactor. With the operational conditions used, Cand. A. phosphatis was enriched until a failure in the pH controller eliminated its ecological advantage. As a result, the comparison of quantification techniques included Cand. A. phosphatis concentrations as low as 11% and as high as 96% of the total cells in the samples. The analysis demonstrated that, regardless of the particular limitations of each technique, both provided similar results when the activated-sludge flocs were easily dispersed. However, when the activated-sludge samples contained flocs that were difficult to disperse, flow cytometry failed to provide quantitative results.     

Modified Whittaker plots as an assessment and monitoring tool for vegetation in a lowland tropical rainforest

Resource exploitation in lowland tropical forests is increasingand causing loss of biodiversity. Effective evaluation and management of the impacts of development on tropical forests requires appropriate assessment and monitoring tools. We proposethe use of 0.1-ha multi-scale, modified Whittaker plots (MWPs) to assess and monitor vegetation in lowland tropical rainforests.We established MWPs at 4 sites to: (1) describe and comparecomposition and structure of the sites using MWPs, (2) compare these results to those of 1-ha permanent vegetation plots (BDPs),and (3) evaluate the ability of MWPs to detect changes in populations (statistical power). We recorded more than 400 species at each site. Species composition among the sites was distinctive, while mean abundance and basal area was similar. Comparisons between MWPs and BDPs show that they record similarspecies composition and abundance and that both perform equallywell at detecting rare species. However, MWPs tend to record morespecies, and power analysis studies show that MWPs were more effective at detecting changes in the mean number of species of trees 10 cm in diameter at breast height (dbh) and in herbaceous plants. Ten MWPs were sufficient to detect a change of 11% in the mean number of herb species, and they were able to detect a 14% change in the mean number of species of trees 10 cm dbh. The value of MWPs for assessment and monitoringis discussed, along with recommendations for improving the sampling design to increase power.     

Cleanup of fractured rock aquifers. II. Effects of matrix diffusion and nonaqueous phase liquid

Model calculations are used to explore the effects of the kinetics of diffusion of dissolved organic compounds into and out of low-permeability porous materials and of the rate of solution of nonaqueous phase liquid (NAPL) droplets (into the aqueous phase) on the rate of cleanup of contaminated aquifers. Two models are presented: (1) the flushing of organic compounds initially distributed as NAPL droplets in a fracture in a porous rock aquifer, and (2) the removal of organic compounds initially present as NAPL in an aquifer containing low-permeability porous clay lenses. NAPL droplet size is found to be of much less importance than the spacing of the fractures in the porous rock in the first model or the thickness of the clay lenses in the second.     

Effect of design parameters in horizontal flow constructed wetland on the behaviour of volatile fatty acids and volatile alkylsulfides

A pilot-scale horizontal flow constructed wetland (HFCW) system planted with common reed (Phragmites sp.) was constructed to study how hydraulic loading rate (HLR), aspect ratio, water depth, and granular medium affect to the fate of several organic matter degradation intermediates namely, acetic acid (HAc), isovaleric acid (Isoval), and dimethylsulfide (DMS). ANOVA statistical analysis performed on the data set of 8 months of operation shows that the HLR and the water depth are two major factors that control the performance of HFCWs for the target analytes. A clear difference in the HFCW effluent concentrations was obtained according to water depth. Effluents of the shallow water depth contained lower DMS (1.05-1.44 microg l-1), HAc (7.91-10.9 mg l-1), and Isoval (0.11-0.15 mg l-1) concentrations than the deeper beds (DMS: 1.68-2.40 microg l-1; HAc: 9.29-14.4 mg l-1, and Isoval: 0.20-0.31 mg l-1). Such differences could be accounted to the different formation and consumption rates of the organic matter degradation intermediates, which is related with the redox potentials (E). Indeed, it could lead to different biochemical reactions of organic matter degradation according with the E value. HLR has a statistically significant influence on the effluent HAc, Isoval, and DMS concentrations. Seasonal variability of effluent HAc concentration shows that it is independent on the HAc loading. While the loading showed no seasonal pattern, the removal efficiency was clearly higher in cold months, which suggests a predominant internal production of HAc in HFCWs in the warm season from the accumulated organic particulate matter. Similar results were also found when Isoval and DMS were considered.     

Atmospheric Aerosols over a Southwestern Region of Texas

Speciated samples of PM_2.5 were collected at the Big Bend site from July of 2003 to June 2006 and the McDonald Observatory site from July of 2003 to August of 2005 in southwestern Texas, respectively, by the US Environmental Protection Agency. A total of 175 samples for the Big Bend site and 105 samples for the McDonald Observatory site with 52 species were measured; however, 30 and 32 species from the Big Bend and McDonald Observatory sites, respectively, were excluded because of too much below-detection-limit data. Due to the laboratory change about November 1 of 2004 and possible analytical artifacts, phosphorous was excluded as well. Among the species excluded, 31 species are common to both sites. The two data sets were analyzed by positive matrix factorization to infer the sources of PM observed at the two sites. The analysis resolved five source-related factors for Big Bend and four for McDonald Observatory. Sulfate-rich secondary aerosol, coal burning, motor vehicle/road dust, and a mixed factor were identified as common sources to both sites. The other factor identified for Big Bend is related to soil. Sulfate mainly exists as ammonium salts. The sulfate-rich secondary aerosols account for about 62% and 66% of the PM_2.5 mass concentration at the two sites, respectively. The highest concentration of Si associated with Ca, Fe, \textSO₄^{2 -} {\text{SO}}_4^{2 - } , and organic carbon at the two sites was possibly attributed to the coal-fired power plants in the region. Basically, the factor of sulfate and coal burning at the two sites showed similar chemical composition profiles and seasonal variation that reflect the regional characteristics of these sources. The regional factors of sulfate, coal burning, and soil showed predominantly low-frequency variations; however, the area-related and/or local factors showed both high and low frequency variations. The motor vehicle/road dust and the mixed factors were likely to be area-related and/or local source.     

Construction and demolition waste management process modeling: a framework for the Brazilian context

Journal of Material Cycles and Waste Management - In Brazil, municipal public authorities are responsible for construction and demolition (C&D) waste management. However, there is a lack of...