Sorption of hydrophobic pesticides on a Mediterranean soil affected by wastewater, dissolved organic matter and salts

Irrigation with treated wastewaters as an alternative in countries with severe water shortage may influence the sorption of pesticides and their environmental effects, as wastewater contains higher concentrations of suspended and dissolved organic matter and inorganic compounds than freshwater. We have examined the sorption behaviour of three highly hydrophobic pesticides (the herbicide pendimethalin and the insecticides α-cypermethrin and deltamethrin) on a Mediterranean agricultural soil using the batch equilibration method. We considered wastewater, extracts from urban sewage sludge with different dissolved organic carbon contents, and inorganic salt solutions, using Milli Q water as a control. All pesticides were strongly retained by soil although some sorption occurred on the walls of the laboratory containers, especially when wastewater and inorganic salt solutions were used. The calculation of distribution constants by measuring pesticide concentrations in soil and solution indicated that pendimethalin sorption was not affected whereas α-cypermethrin and deltamethrin retention were significantly enhanced (ca. 5 and 2 times, respectively) when wastewater or salt solutions were employed. We therefore conclude that the increased sorption of the two pesticides caused by wastewater cannot be only the result of its dissolved organic carbon content, but also of the simultaneous presence of inorganic salts in the solution.     

Virus retention and transport as influenced by different forms of soil organic matter

Organic materials are widespread in natural soil and aquatic environments. Their effect on virus transport is very important in assessing the risk for contamination of ground water by viruses. This study aimed to determine how different forms (mineral-associated and dissolved) of natural organic matter influence the retention and transport of two bacteriophages (MS-2 and phiX174) in two porous media (a sand and a soil). We found that mineral-associated organic matter significantly promoted the transport of one virus (MS-2) but not the other (phiX174) in a phosphate-buffered saline solution. Similarly, MS-2 was retained less in sand columns with increasing concentrations of dissolved humic acid, while little effect was observed for phiX174 under the same conditions. The two viruses have different surface properties and thus exhibited different reactivity to the metal oxides present on sand particles and were affected differently by organic matter. Because the organic matter used in the study was negatively charged and hydrophilic, blocking of virus sorption sites and increasing of virus-medium electrostatic repulsion arising from modification of the sand and virus surface by organic matter are probably responsible for the facilitated transport. For dissolved humic acid, its competition for sorption sites with viruses was an additional mechanism involved. This study suggests that the effect of organic matter varied depending on the organic material properties and the type of viruses involved. As a general trend, the effect of organic matter was dominated by electrostatic rather than hydrophobic interactions.     

Effect of river sediment on phosphorus chemistry of similarly aged natural and created wetlands in the Atchafalaya Delta, Louisiana, USA

The goal of wetland creation is to produce an artificial wetland that functions as a natural wetland. Studies comparing created wetlands to similarly aged natural wetlands provide important information about creation techniques and their improvement so as to attain that goal. We hypothesized that differences in sediment phosphorus accretion, deposition, and chemistry between created and natural wetlands in the Atchafalaya Delta, Louisiana, USA were a function of creation technique and natural river processes. Sediment deposition was determined with feldspar marker horizons located in created and natural wetlands belonging to three age classes (<3, 5-10, and 15-20 yr old). Phosphorus fractions were measured in these deposited sediments and in suspended and bedload sediment from the Atchafalaya River. Bedload sediment had significantly lower iron- and aluminum-bound, reductant-soluble, and total phosphorus than suspended sediment due to its high sand percentage. This result indicates that wetlands artificially created in the Atchafalaya Delta using bedload sediment will initially differ from natural wetlands of the same age. Even so, similarities between the mudflat stratum of the <1- to 3-yr-old created wetland and the mudflat stratum of the 15- to 20-yr-old natural wetland support the contention that created wetlands in the Atchafalaya Delta can develop natural characteristics through the deposition of river suspended sediment. Differences between three created wetland strata, the 15- to 20-yr-old willow stratum and the <1- to 3-yr-old willow and mixed marsh strata, and their natural counterparts were linked to design elements of the created wetlands that prevented the direct deposition of the river's suspended sediment.     

Particulate matter concentration and air quality affected by windblown dust in the Columbia plateau

The USEPA has proposed to regulate PM(coarse) (particulate matter 2.5 to 10 microm in diameter). Exceedance of the proposed National Ambient Air Quality Standard (NAAQS) for PM(coarse) is expected within the Columbia Plateau of the Pacific Northwest United States based on the high frequency of dust storms and the large contribution of crustal material to fugitive dust in the region. The objective of this study was to explore the implication of the proposed NAAQS for PM(coarse) on air quality. Concurrent observations of both PM10 (particulate matter 相似文献   

Sulfadimethoxine degradation kinetics in manure as affected by initial concentration, moisture, and temperature

Sulfadimethoxine is a widely used sulfonamide veterinary antibiotic and could be a source of agricultural contamination. Therefore, information is needed about its degradation kinetics in manure under aerobic conditions. Based on the analysis of first-order kinetics and the assumption that sulfadimethoxine availability for degradation in manure could be limiting, a new kinetic model was developed and was found to fit the degradation kinetics well. The degradation rate in sterile manure was found to be much lower than in nonsterile manure, indicating that biodegradation was significant. In biologically active manure, the degradation rate constant decreased with increasing initial concentration of sulfadimethoxine, implying that the activity of the degrading microorganisms was inhibited. Increasing moisture or temperature was found to increase sulfadimethoxine degradation in manure. Mixing manure containing high levels of sulfadimethoxine with manure containing lower levels may result in more rapid degradation, thus greatly diminishing sulfadimethoxine contamination in manure and significantly reducing sulfadimethoxine inputs into the environment. During treatment, keeping the manure moist and storing in a moderately warm place under aerobic conditions may also help to diminish sulfadimethoxine contamination.     

Social and economic considerations in conserving wetlands of indo-gangetic plains: A case study of Kabartal wetland,India

The Kabartal wetland situated in the upper Indo-Gangetic flood plains in northern India is significant because of its hydrological and ecological services, and the socio-economic and cultural values that it represents. Despite being designated as a wildlife sanctuary, this wetland is under threat from anthropogenic pressures. As in the case of most wetlands, the reason is incomplete information on its ecological services and functions, breakdown of traditional management structures and the lack of appropriate and recognized property rights. Our study assesses the economic linkages between the Kabartal wetland and the local people living around it, through socio-economic surveys and Contingent Valuation Method (CVM). The major objective of the study was to determine the importance of this wetland to the local people and to give an indication of the distribution of the benefits among various stakeholders. The people in the region are poor, have low literacy levels and high dependence on Kabartal and more than 50% want that the wetland should be drained and the land used for agriculture. However, they are willing to participate in collaborative management initiatives with the state. The willingness of people to accept compensation, as an alternative to access to Kabartal wetland, regressed on various socio-economic and attitudinal parameters, gave an estimated mean value of US $27,500 per household over a period of 60 years. This value is a pointer of the total value of access to Kabartal wetland to the surrounding villagers and would be useful when decisions to compensate people for lost access to Kabartal are made.     

Analysis of the metabolic utilization of carbon sources and potential functional diversity of the bacterial community in lab-scale horizontal subsurface-flow constructed wetlands

Microorganisms are an integral part of the biogeochemical processes in wetlands. To improve the performance of constructed wetlands, it is very important to know the metabolic properties and functional diversity of the microbial communities. The purpose of this study is to analyze the metabolic properties and functional diversity of the microbial community in a horizontal subsurface-flow constructed wetland (CW) in a laboratory study through the sole-carbon-source utilization profiles using Biolog-ECO microplates. The technique has advantages over traditional cell culture techniques, such as molecular-level techniques-RNA amplification, which are time-consuming, expensive, and only applicable to the small number of species that may be cultured. This CW was designed to treat rural eutrophic water in China, using the plant L. This study showed that the metabolic activities of upper front substrate microorganisms (UF) were greater than those of the lower back substrate microorganisms (LB) in the CW. Integrated areas under average well color development (AWCD) curves of substrate microorganisms in the UF were 131.9, 4.8, and 99.3% higher than in the lower front part (LF), the upper back part (UB), and the LB part of the CW, respectively. Principal components analysis showed significant differences in both community structure and metabolic utilization of carbon sources between substrate microorganisms from different sampling sites. Carbon source utilization of polymers, carbohydrates, carboxylic acids, and amino acids was higher in UF than in LF, but that of amines and phenolic compounds was very similar in UF and LF. The richness, evenness, and diversity of upper substrate microbial communities were significantly higher than those of lower substrate. The LF substrate microbial communities had lower evenness than the other sampling plots, and the lowest richness of substrate microbial community was found in the LB part of the CW.     

The role of condensed organic matter in the nonlinear sorption of hydrophobic organic contaminants by a peat and sediments

This study examines the effect of soil organic matter heterogeneity on equilibrium sorption and desorption of phenanthrene, naphthalene, 1,3,5-trichlorobenzene (1,3,5-TCB), and 1,2-dichlorobenzene (1,2-DCB) by soils and sediments. Two estuary sediments, a Pahokee peat (PP; Euic, hyperthermic Lithic Haplosaprist), and two subsamples (base- and acid-treated peat [TP] and acid-treated peat [FP]) of the peat were used as the sorbents. The contents of black carbon particles were quantified with a chemical extraction method. Petrographical examinations revealed the presence of the condensed soil and sediment organic matter (SOM) in Pahokee peat. The Freundlich isotherm model in two different forms was used to fit both sorption and desorption data. The results show that the sorption and desorption isotherms are generally nonlinear and that the apparent sorption-desorption hysteresis is present for phenanthrene and TCB. Detailed analysis of sorption data for the tested sorbent-sorbate systems indicates that black carbon is probably responsible for sorption isotherm nonlinearity for the two sediments, whereas the humic substances and kerogen may play the dominant role in nonlinear sorption by the peat. This investigation suggests that the microporosity of SOM is important for the hydrophobic organic contaminant (HOC) sorption capacity on the peat.     

Chemical composition of organic matter in extremely acid, lignite-containing lake sediments impacted by fly ash contamination

In the Lusatian lignite mining district of eastern Germany, extremely acid lakes developed during ground water rising after exploitation of lignite in open-cast mines. The reasons of plant colonization (Juncus bulbosus L.) of some lakes exhibiting moderate pH values while others remain extremely acid and unvegetated are unknown. Alkalinity gain may be achieved by addition of alkaline materials and/or decomposition of organic matter. Our objective was to examine fly ash deposition and the resulting changes in organic matter composition in the uppermost 0 to 5 cm of the sediment sampled from vegetated and unvegetated lakes. Bulk soil and particle size fractions were analyzed for elemental composition, magnetic susceptibility, and chemical structure of the organic matter by 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. The lignite content of the samples was estimated by 14C activity measurements. The pH values decreased with increasing depth and the changes in pH were found to be correlated with changes in magnetic susceptibility. Carbon and nitrogen contents were found to decrease with increasing depth. The C to N ratios are consistent with the (i) the presence of decomposing plant residues and/or microbial material such as algae in the upper 0 to 5 cm of the sediment and (ii) the dominance of lignite in the layers below this depth as confirmed by 14C activity measurements. The structural analyses of the particle size separates from the 0- to 5-cm depth were consistent with the presence of organic matter derived from plant material. This study confirms that fly ash is an important source of alkalinity in the upper 0 to 5 cm of the sediment that enhanced plant growth and led to enrichment of the sediment with organic matter derived from plant material.     

Colloidal and dissolved phosphorus in sandy soils as affected by phosphorus saturation

Fertilization exceeding crop requirements causes an accumulation of phosphorus (P) in soils, which might increase concentrations of dissolved and colloidal P in drainage. We sampled soils classified as Typic Haplorthods from four fertilization experiments to test (i) whether increasing degrees of phosphorus saturation (DPS) increase concentrations of dissolved and colloidal P, and (ii) if critical DPS levels can be defined for P release from these soils. Oxalate-extractable concentrations of P, iron (Fe), and aluminum (Al) were quantified to characterize DPS. Turbidity, zeta potential, dissolved P, and colloidal P, Fe, Al, and carbon (C) concentrations were determined in water and KCl extracts. While concentrations of dissolved P decreased with increasing depth, concentrations of water-extractable colloidal P remained constant. In topsoils 28 +/- 17% and in subsoils 94 +/- 8% of water-extractable P was bound to colloids. Concentrations of dissolved P increased sharply for DPS > 0.1. Colloidal P concentrations increased with increasing DPS because of an additional mobilization of colloids and due to an increase of the colloids P contents. In addition to DPS, ionic strength and Ca(2+) affected the release of colloidal P. Hence, using KCl for extraction improved the relationship between DPS and colloidal P compared with water extraction. Accumulation of P in soils increases not only concentrations of dissolved P but also the risk of colloidal P mobilization. Leaching of colloidal P is potentially important for inputs of P into water bodies because colloidal P as the dominant water-extractable P fraction in subsoils was released from soils with relatively low DPS.     

Soil carbon dioxide emission and carbon content as affected by irrigation, tillage, cropping system, and nitrogen fertilization

Management practices can influence soil CO(2) emission and C content in cropland, which can effect global warming. We examined the effects of combinations of irrigation, tillage, cropping systems, and N fertilization on soil CO(2) flux, temperature, water, and C content at the 0- to 20-cm depth from May to November 2005 at two sites in the northern Great Plains. Treatments were two irrigation systems (irrigated vs. non-irrigated) and six management practices that contained tilled and no-tilled malt barley (Hordeum vulgaris L.) with 0 to 134 kg N ha(-1), no-tilled pea (Pisum sativum L.), and a conservation reserve program (CRP) planting applied in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. In eastern Montana, treatments were no-tilled malt barley with 78 kg N ha(-1), no-tilled rye (Secale cereale L.), no-tilled Austrian winter pea, no-tilled fallow, and tilled fallow applied in dryland Williams loam (fine-loamy, mixed Typic Argiborolls). Irrigation increased CO(2) flux by 13% compared with non-irrigation by increasing soil water content in North Dakota. Tillage increased CO(2) flux by 62 to 118% compared with no-tillage at both places. The flux was 1.5- to 2.5-fold greater with tilled than with non-tilled treatments following heavy rain or irrigation in North Dakota and 1.5- to 2.0-fold greater with crops than with fallow following substantial rain in Montana. Nitrogen fertilization increased CO(2) flux by 14% compared with no N fertilization in North Dakota and cropping increased the flux by 79% compared with fallow in no-till and 0 kg N ha(-1) in Montana. The CO(2) flux in undisturbed CRP was similar to that in no-tilled crops. Although soil C content was not altered, management practices influenced CO(2) flux within a short period due to changes in soil temperature, water, and nutrient contents. Regardless of irrigation, CO(2) flux can be reduced from croplands to a level similar to that in CRP planting using no-tilled crops with or without N fertilization compared with other management practices.     

Changes in Connecticut salt-marsh vegetation as revealed by historical aerial photographs and computer-assisted cartographics

Procedures are discussed for the interpretation of historical aerial photographs for salt-marsh vegetation mapping, as are techniques for computer-assisted analysis of digital vegetation maps. The mappings indicate an increase in the coverage by the low marsh speciesSpartina alterniflora Loisel. at three marsh sites studied in photographs from the period 1934–1981. It is hypothesized that changes in salt-marsh vegetation may be in response to natural tidal fluctuations or to management practices.     

Variation in some chemical parameters and organic matter in soils regenerated by the addition of municipal solid waste

The organic fraction of a municipal solid waste was added in different doses to an eroded soil formed of loam and with no vegetal cover. After three years, the changes in macronutrient content and the chemical-structural composition of its organic matter were studied. The addition of the organic fraction from a municipal solid waste had a positive effect on soil regeneration, the treated soils being covered with spontaneous vegetation from 1 yr onwards. An increase in electrical conductivity and a fall in pH were noted in the treated soils as were increases in macronutrients, particularly N and available P and the different carbon fractions. Optical density measurements of the organic matter extracted with sodium pyrophosphate showed that the treated soils contained an organic matter with less condensed compounds and with a greater tendency to evolve than the control. A pyrolysis-gas chromatography study of the organic matter extracted with pyrophosphate showed large quantities of benzene both in the treated soils and control; pyrrole was also relatively abundant, although this fragment decreased as the dose rose. Xylenes and pyridine were present in greater quantities in the control and furfural in the treated soils. Three years after addition to the soil, the organic matter had a higher proportion of fragments derived from aromatic compounds and a smaller proportion derived from hydrocarbons. Similarity indices showed that, although the added and newly formed organic matter 3 yr after addition continued to differ from that of the original soil and to be more mineralizable, the transformations it has undergone made it more similar to the original organic matter of the soil than it was at the moment of being added.     

Effect of organic matter oxidation on the fractionation of copper, zinc, lead, and arsenic in sewage sludge and amended soils

Long-term land application of sewage sludge (SS) has caused concern over the potential release of trace metals into the environment following the degradation of organic matter (OM). This study was performed to assess the impact of OM degradation on the relative distribution of Cu, Zn, Pb, and As in SS and SS-amended soils. Three SSs of different ages and two soils treated with SS were subjected to incubation and direct chemical oxidation using diluted HO, followed by a sequential extraction. The majority of Cu, Pb, and As were bound to OM, whereas the majority of Zn was bound with Fe/Mn oxides for all three SSs. Incubation of SS for 6 mo did not result in a substantial decrease in OM content or a change in the relative distribution of Cu, Zn, Pb, and As. Direct OM oxidation to 30 and 70% by diluted HO resulted in a significant decrease in organically bound Cu but increased its exchangeable, carbonate-bound, and Fe/Mn-bound fractions. Oxidation of OM slightly decreased organically bound Zn but significantly increased exchangeable Zn in all SSs. Oxide- and carbonate-bound Zn also decreased following OM oxidation. Exchangeable fractions of As and Pb were minute before and after OM degradation, indicating that release into the environment would be unlikely. The relative distribution of Cu, Zn, Pb, and As in SS-treated soils was similar to that of SS, suggesting a dominant role of SS properties in controlling metal distribution following OM oxidation. Overall, OM oxidation increased the mobility and bioavailability of Zn and Cu, whereas it had less impact on Pb and As.     

Indirect carbon reduction by residential vegetation and planting strategies in Chicago, USA

Concern about climate change has evoked interest in the potential for urban vegetation to help reduce the levels of atmospheric carbon. This study applied computer simulations to try to quantify the modifying effects of existing vegetation on the indirect reduction of atmospheric carbon for two residential neighborhoods in north-west Chicago. The effects of shading, evapotranspiration, and windspeed reduction were considered and were found to have decreased carbon emissions by 3.2 to 3.9% per year for building types in study block 1 where tree cover was 33%, and -0.2 to 3.8% in block 2 where tree cover was 11%. This resulted in a total annual reduction of carbon emission averaging 158.7 (+/- 12.8) kg per residence in block 1 and 18.1 (+/- 5.4) kg per residence in block 2. Windspeed reduction greatly contributed to the decrease of carbon emission. However, shading increased annual carbon emission from the combined change in heating and cooling energy use due to many trees in the wrong locations, which increase heating energy use during the winter. The increase of carbon emission from shading is somewhat specific to Chicago, due in part to the large amount of clean, nuclear-generated cooling energy and the long heating season. In Chicago, heating energy is required for about eight months from October to May and cooling energy is used for the remaining 4 months from June to September. If fossil fuels had been the primary source for cooling energy and the heating season had been shorter, the shading effects on the reduction of carbon emission would be greater. Planting of large trees close to the west wall of buildings, dense planting on the north, and avoidance of planting on the south are recommended to maximize indirect carbon reduction by residential vegetation, in Chicago and other mid and high-latitude cities with long heating seasons.     

Nitrate leaching to subsurface drains as affected by drain spacing and changes in crop production system

Subsurface drainage is a beneficial water management practice in poorly drained soils but may also contribute substantial nitrate N loads to surface waters. This paper summarizes results from a 15-yr drainage study in Indiana that includes three drain spacings (5, 10, and 20 m) managed for 10 yr with chisel tillage in monoculture corn (Zea mays L.) and currently managed under a no-till corn-soybean [Glycine max (L.) Merr.] rotation. In general, drainflow and nitrate N losses per unit area were greater for narrower drain spacings. Drainflow removed between 8 and 26% of annual rainfall, depending on year and drain spacing. Nitrate N concentrations in drainflow did not vary with spacing, but concentrations have significantly decreased from the beginning to the end of the experiment. Flow-weighted mean concentrations decreased from 28 mg L(-1) in the 1986-1988 period to 8 mg L(-1) in the 1997-1999 period. The reduction in concentration was due to both a reduction in fertilizer N rates over the study period and to the addition of a winter cover crop as a "trap crop" after corn in the corn-soybean rotation. Annual nitrate N loads decreased from 38 kg ha(-1) in the 1986-1988 period to 15 kg ha(-1) in the 1997-1999 period. Most of the nitrate N losses occurred during the fallow season, when most of the drainage occurred. Results of this study underscore the necessity of long-term research on different soil types and in different climatic zones, to develop appropriate management strategies for both economic crop production and protection of environmental quality.     

Root exudation, phosphorus acquisition, and microbial diversity in the rhizosphere of white lupine as affected by phosphorus supply and atmospheric carbon dioxide concentration

White lupine (Lupinus albus L.) was used as a phosphorus (P)-efficient model plant to study the effects of elevated atmospheric CO(2) concentrations on (i) P acquisition, (ii) the related alterations in root development and rhizosphere chemistry, and (iii) the functional and structural diversity of rhizosphere microbial communities, on a P-deficient calcareous subsoil with and without soluble P fertilization. In both +P (80 mg P kg(-1)) and -P treatments (no added P), elevated CO(2) (800 micromol mol(-1)) increased shoot biomass production by 20 to 35% and accelerated the development of cluster roots, which exhibit important functions in chemical mobilization of sparingly soluble soil P sources. Accordingly, cluster root formation was stimulated in plants without P application by 140 and 60% for ambient and elevated CO(2) treatments, respectively. Intense accumulation of citrate and increased activities of acid and alkaline phosphatases, but also of chitinase, in the rhizosphere were mainly confined to later stages of cluster root development in -P treatments. Regardless of atmospheric CO(2) concentrations, there was no significant effect on accumulation of citrate or on selected enzyme activities of C, N, and P cycles in the rhizosphere of individual root clusters. Discriminant analysis of selected enzyme activities revealed that mainly phosphatase and chitinase contributed to the experimental variance (81.3%) of the data. Phosphatase and chitinase activities in the rhizosphere might be dominated by the secretion from cluster roots rather than by microbial activity. Alterations in rhizosphere bacterial communities analyzed by denaturing gradient gel electrophoresis (DGGE) were related with the intense changes in root secretory activity observed during cluster root development but not with elevated CO(2) concentrations.     

Nitrogen fertilizer replacement value of cattle slurry in grassland as affected by method and timing of application

Slurry application with methods such as trailing shoe (TS) results in reduced emissions of ammonia (NH3) compared with broadcast application using splashplate (SP). Timing the application during cool and wet weather conditions also contributes to low NH3 emissions. From this perspective, we investigated whether reduced NH3 emissions due to improved slurry application method and timing results in an increase in the nitrogen (N) fertilizer replacement value (NFRV). The effects of application timing (June vs. April) and application method (TS vs. SP) on the apparent N recovery (ANR) and NFRV from cattle slurry applied to grassland were examined on three sites over 3 yr in randomized block experiments. The NFRV was calculated using two methods: (i) NFRV(N) based on the ANR of slurry N relative to mineral N fertilizer; and (ii) NFRV(DM) based on DM yield. The TS method increased the ANR, NFRV(N), and NFRV(DM) compared with SP in the 40- to 50-d period following slurry application by 0.09, 0.10, and 0.10 kg kg(-1), respectively. These values were reduced to 0.07, 0.06, and 0.05 kg kg(-1), respectively, when residual harvests during the rest of the year were included. The highest NFRV(DM) for the first harvest period was with application in April using STS (0.30 kg kg(-1)), while application in June with SP had the Slowest (0.12 kg kg(-1)). The highest NFRV(DM) for the cumulative harvest period was with application in April using TS (0.38 kg kg(-1)), while application in June with SP had the lowest (0.17 kg kg(-1)). Improved management of application method, by using TS instead of SP, and timing, by applying slurry in April rather than June, offer potential to increase the NFRV(DM) of cattle slurry applied to grassland.     

Industrial odours as environmental stressors: Exposure-annoyance associations and their modification by coping, age and perceived health

The degree of association between industrial odours and reported annoyance was investigated by means of field studies in four German cities, namely Duisburg (n = 400), Brühl (n = 539), Dortmund (n = 400) and Rodenkirchen (n = 200). The degree of odour exposure was assessed by estimating the frequency of odours by means of systematic field observations, whereas annoyance was assessed by personal interviews using standardized questionnaires. Both studies revealed highly significant associations between odour exposure and degree of annoyance. Odour annoyance was correlated with personal factors: age was negatively related to annoyance, whereas dissatisfaction with health exhibited positive associations with annoyance. Coping strategies were also associated with odour annoyance: high scores in problem-oriented coping strategies increased annoyance, whereas high scores in avoidance coping reduced annoyance. Coping strategies based upon the reduction of emotional stress were not associated with annoyance. Since none of the interaction terms of the full regression model proved significant, no true moderators were identified. In order to check for aquiescence bias, people who were interviewed personally were compared with those who could not be approached directly and who were therefore contacted by mail. Despite some significant differences in terms of gender, education, occupation, problem-oriented coping and avoidance coping, both groups did not differ in terms of annoyance.     

Carbon sequestration in dryland soils and plant residue as influenced by tillage and crop rotation

Long-term use of conventional tillage and wheat (Triticum aestivum L.)-fallow systems in the northern Great Plains have resulted in low soil organic carbon (SOC) levels. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)], five crop rotations [continuous spring wheat (CW), spring wheat-fallow (W-F), spring wheat-lentil (Lens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)], and Conservation Reserve Program (CRP) planting on plant C input, SOC, and particulate organic carbon (POC). A field experiment was conducted in a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) from 1998 to 2003 in Havre, MT. Total plant biomass returned to the soil from 1998 to 2003 was greater in CW (15.5 Mg ha(-1)) than in other rotations. Residue cover, amount, and C content in 2004 were 33 to 86% greater in NT than in CT and greater in CRP than in crop rotations. Residue amount (2.47 Mg ha(-1)) and C content (0.96 Mg ha(-1)) were greater in NT with CW than in other treatments, except in CT with CRP and W-F and in NT with CRP and W-W-F. The SOC at the 0- to 5-cm depth was 23% greater in NT (6.4 Mg ha(-1)) than in CT. The POC was not influenced by tillage and crop rotation, but POC to SOC ratio at the 0- to 20-cm depth was greater in NT with W-L (369 g kg(-1) SOC) than in CT with CW, W-F, and W-L. From 1998 to 2003, SOC at the 0- to 20-cm depth decreased by 4% in CT but increased by 3% in NT. Carbon can be sequestered in dryland soils and plant residue in areas previously under CRP using reduced tillage and increased cropping intensity, such as NT with CW, compared with traditional practice, such as CT with W-F system, and the content can be similar to that in CRP planting.