Biochar application to soil has been proposed as a mechanism for improving soil quality and the long term sequestration of carbon. The implications of biochar on pesticide behavior, particularly in the longer term, however, remains poorly understood. Here we evaluated the influence of biochar type, time after incorporation into soil, dose rate and particle size on the sorption, biodegradation and leaching of the herbicide simazine. We show that typical agronomic application rates of biochar (10–100 t ha−1) led to alterations in soil water herbicide concentrations, availability, transport and spatial heterogeneity. Overall, biochar suppressed simazine biodegradation and reduced simazine leaching. These responses were induced by a rapid and strong sorption of simazine to the biochar which limits its availability to microbial communities. Spatial imaging of 14C-labeled simazine revealed concentrated hotpsots of herbicide co-localized with biochar in the soil profile. The rate of simazine mineralization, amount of sorption and leaching was inversely correlated with biochar particle size. Biochar aged in the field for 2 years had the same effect as fresh biochar on the sorption and mineralization of simazine, suggesting that the effects of biochar on herbicide behavior may be long lasting. We conclude that biochar application to soil will reduce the dissipation of foliar applied pesticides decreasing the risk of environmental contamination and human exposure via transfer in the food chain, but may affect the efficacy of soil-applied herbicides.
Houston is one of the fastest growing metropolitan areas in the U.S. By the year 2000, it will be the third largest city in the nation. The city's human waste disposal demand is increasing on an average of 300,000 gal/mo. Steps in an 8 yr wastewater treatment program are outlined. The Houston Ship Channel, declared biologically dead in 1966, supports shrimp, crabs, and even flounder. (2 photos)
This article is a revision of the previous edition article by D.L. Jones, E.C. Rowe, volume 2, pp. 741–748, © 2003, Elsevier Ltd.
No abstract is provided for this article.
The application of biochar to soil has been shown to cause an apparent increase in soil respiration. In this study we investigated the mechanistic basis of this response. We hypothesized that increased CO2 efflux could occur by: (1) Biochar-induced changes in soil physical properties (bulk density, porosity, moisture content); (2) The biological breakdown of organic carbon (C) released from the biochar; (3) The abiotic release of inorganic C contained in the biochar; (4) A biochar-induced stimulation of decomposition of native soil organic matter (SOM) which could occur both biotically or abiotically; (5) The intrinsic biological activity of the biochar results in the liberation of CO2. Our results show that most of the extra CO2 produced after biochar addition to soil came from the equal breakdown of organic C and the release of inorganic C contained in the biochar. Using long-term 14C-labelled SOM, we show that biochar repressed native SOM breakdown, counteracting the release of CO2 from the biochar. A range of mechanisms to describe this negative priming response is presented. Although biochar-induced significant changes in the physical characteristics of the soil, overall this made no contribution to changes in soil respiration. Similarly, the evidence from our study suggests that changes in soluble polyphenols do not help explain the respiration response. In summary, biochar induced a net release of CO2 from the soil; however, this C loss was very small relative to the amount of C stored within the biochar itself (ca. 0.1%). This short-term C release should therefore not compromise its ability to contribute to long-term C sequestration in soil environments.
The worldwide spread of SARS-CoV-2 and the resulting COVID-19 pandemic has been driven by international travel. This has led to the desire to develop surveillance approaches which can estimate the rate of import of pathogenic organisms across international borders. The aim of this study was to investigate the use of wastewater-based approaches for the surveillance of viral pathogens on commercial short-haul (3.5 h transit time) roll-on/roll-off passenger/freight ferries operating between the UK and the Republic of Ireland.
Acidifying slurry with sulfuric acid (H2SO4) is practiced in some countries for reducing ammonia (NH3) emissions during slurry storage and spreading to land. However, knowledge on how the application of acidified slurry affects soil health and nutrient cycling is lacking. This is particularly important since acidification with H2SO4 can substitute a sulfur (S) mineral fertilizer to increasingly S-deficient agricultural soils. We hypothesized that (ⅰ) slurry acidification would decrease the soil pH over a prolonged period, and as a result (ⅱ) would increase the extractable N, P, C and S concentrations, (ⅲ) and decrease greenhouse gas emissions. By using laboratory mesocosms, the nutrient (C, N, P and S) dynamics were monitored in an arable sandy clay loam soil receiving acidified and non-acidified cattle slurry in a 2-month incubation. Estimations of greenhouse gas emissions (CO2, CH4, N2O), soil-pore- water components (NO3−, NH4+, PO43−, SO42−, DOC, DON, pH) were performed on static mesocosms. In addition, a parallel set of mesocosms were used for soil extractions using distilled water and 0.5 M K2SO4. There were six treatments: (1) soil (control), (2) soil + slurry, (3) soil + acidified slurry (with H2SO4, pH =5.5), (4) soil + HCl, (5) soil + K2SO4, and (6) soil + K2SO4 + H2SO4. Our results showed that over the incubation, slurry acidification reduced soil pH by at least 0.4 units. Water soluble PO43−-P concentration was also reduced, whilst extractable DOC and NO3—N concentrations were increased; the latter as a result of stimulated N mineralization in the acidification treatments (3, 4 and 6). Differences in water soluble SO42- -S concentrations per treatment were not significant over time. Slurry acidification did not significantly affect N2O emissions but decreased net CO2 and CH4 emissions leading to an overall reduction in the soil's total greenhouse gas footprint (expressed as CO2e). We conclude that application of acidified slurry to soil can reduce soil pH by at least 0.4 pH units for up to 2-months before it is buffered back to the pH level of the soil that received the non-acidified slurry. In addition to increasing organic N mineralization with limited impacts on P and S dynamics of the soil and the slurry.
Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are able to provide key ecosystem services, protecting plants against biotic and abiotic stresses. Here, we hypothesized that a combination of AMF (Rhizophagus clarus) and PGPR (Bacillus sp.) could enhance 33P uptake in maize plants under soil water stress. A microcosm experiment using mesh exclusion and a radiolabeled phosphorus tracer (33P) was installed using three types of inoculation: i) only AMF, ii) only PGPR, and iii) a consortium of AMF and PGPR, alongside a control treatment without inoculation. For all treatments, a gradient of three water-holding capacities (WHC) was considered i) 30% (severe drought), ii) 50% (moderate drought), and iii) 80% (optimal condition, no water stress). In severe drought conditions, AMF root colonization of dual-inoculated plants was significantly lower compared to individual inoculation of the AMF, whilst 33P uptake by dual-inoculated plants or plants inoculated with bacteria was 2.4-fold greater than the uninoculated treatment. Under moderate drought conditions the use of AMF promoted the highest 33P uptake by plants, increasing it by 2.1-fold, when compared to the uninoculated treatment. Without drought stress, AMF showed the lowest 33P uptake and, overall, plant P acquisition was lower for all inoculation types when compared to the severe and moderate drought treatments. The total shoot P content was modulated by the water-holding capacity and inoculation type, with the lowest values observed under severe drought and the highest values under moderate drought. The highest soil electrical conductivity (EC) values were found under severe drought in AMF-inoculated plants and the lowest EC for no drought in single or dual-inoculated plants. Furthermore, water-holding capacity influenced the total soil bacterial and mycorrhizal abundance over time, with the highest abundances being found under severe and moderate drought. This study demonstrates that the positive influence of microbial inoculation on 33P uptake by plants varied with soil water gradient. Furthermore, under severe stress conditions, AMF invested more in the production of hyphae, vesicles and spore production, indicating a significant carbon drain from the host plant as evidenced by the lack of translation of increased 33P uptake into biomass. Therefore, under severe drought the use of bacteria or dual-inoculation seems to be more effective than individual AMF inoculation in terms of 33P uptake by plants, while under moderate drought, the use of AMF stood out.
Pycnidiospores of Coniothryium minitans Campb. were freeze-etched and examined in the electron microscope. The cell wall is composed of an outer granular layer, with large protuberances giving the outer surface a verrucose appearance, a fibrillar middle layer and possibly a thin amorphous inner layer. The plasmalemma is characterized by the presence of invaginations of various lengths and also by the presence of randomly distributed particles on its outer and inner surface. Within the cytoplasm are spherical vacuoles, whose inner and outer surfaces also bear particles, a large storage vesicle with lamellae, mitochondria with cristae, and a nucleus with nuclear pores. By comparison, examination of ultrathin sections of chemically fixed pycnidiospores embedded in resin yielded little information on the fine structure of the cells. The freeze-etching technique with its unique fracturing process gives much clearer views of the cell walls and cell organelles and furthermore reveals their surface features.
Livestock slurry stores are a key source of ammonia (NH 3 ) and greenhouse gas (GHG) emissions.This study evaluated the potential to reduce NH 3 , CO 2 , CH 4 and N 2 O emissions by adding effective microorganisms (EM) and brewing sugar to beef cattle slurry in a replicated small-scale (1 litre slurry volume) experiment.The effect of EM and brewing sugar was explored at two concentrations (5 v / w and 10% w / w respectively) and in two environments (cold and warm) over a period of 30 days slurry storage.Greenhouse gas emissions were measured by taking headspace samples from the closed vessels over a 1 hour period, whilst relative NH 3 loss was quantified at the same time by placing an acid trap within the closed headspace.Brewing sugar addition induced 'selfacidification' of the slurry, via lactic acid production and accumulation, resulting in a decrease in slurry pH from pH 7.8 to <4.5.This was effective in lowering average NH 3 loss in the cold and warm environments by 40% and 70%, respectively.Methane emissions were also reduced following the addition of brewing sugar, by up to 75%, resulting in a reduction in the cumulative total GHG (N 2 O + CH 4 + CO 2 ) emission (expressed as CO 2 equivalent; CO 2 e) of 34% and 85%, respectively.The total greenhouse gas emission (CO 2 e) during slurry storage was dominated by CH 4 , representing at least 59% of total CO 2 e emitted.Effective microorganisms had little impact on NH 3 and GHG emission, and are not deemed a useful mitigation strategy for these gases.
A sensitive method for the determination of citrate and malate in sub-microliter samples of soil solution is described. The organic acids were derivatized with a pyrene reagent (1-pyrenebutanoic acid hydrazide) and analysed by micellar electrokinetic chromatography separation. The citrate and malate derivatives were detected within 10 min by using a fluorescence detector with a broad excitation wavelength of 240-400 nm and an emission wavelength of 400 nm. The detection limits (noise x 3) were about 0.24 µM for citrate and 0.72 µM for malate. By using internal standardization, this method was applicable to the determination of citrate and malate in soil solution. Furthermore, application of siphon injection with a commercial micropipette enabled the injection of a sub-microliter sample into the analytical system with acceptable reproducibility. When combined with a microsampling method, the method presented here will be useful for the sensitive and selective analysis of citrate and malate in soil solution with high spatial resolution.
