Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions.

Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C)--0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS)--in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

Pyrolysing poultry litter reduces N2O and CO2 fluxes.

Application of poultry litter (PL) to soil can lead to substantial nitrous oxide (N2O) emissions due to the co-application of labile carbon (C) and nitrogen (N). Slow pyrolysis of PL to produce biochar may mitigate N2O emissions from this source, whilst still providing agronomic benefits. In a corn crop on ferrosol with similarly matched available N inputs of ca. 116 kg N/ha, PL-biochar plus urea emitted significantly less N2O (1.5 kg N2O-N/ha) compared to raw PL at 4.9 kg N2O-N/ha. Urea amendment without the PL-biochar emitted 1.2 kg N2O-N/ha, and the PL-biochar alone emitted only 0.35 kg N2O-N/ha. Both PL and PL-biochar resulted in similar corn yields and total N uptake which was significantly greater than for urea alone. Using stable isotope methodology, the majority (~80%) of N2O emissions were shown to be from non-urea sources. Amendment with raw PL significantly increased C mineralisation and the quantity of permanganate oxidisable organic C. The low molar H/C (0.49) and O/C (0.16) ratios of the PL-biochar suggest its higher stability in soil than raw PL. The PL-biochar also had higher P and K fertiliser value than raw PL. This study suggests that PL-biochar is a valuable soil amendment with the potential to significantly reduce emissions of soil greenhouse gases compared to the raw product. Contrary to other studies, PL-biochar incorporated to 100mm did not reduce N2O emissions from surface applied urea, which suggests that further field evaluation of biochar impacts, and methods of application of both biochar and fertiliser, are needed.

Improving the statistical preparation for measuring soil N2O flux by closed chamber.

Nitrous oxide emissions from soil are known to be spatially and temporally volatile. Reliable estimation of emissions over a given time and space depends on measuring with sufficient intensity but deciding on the number of measuring stations and the frequency of observation can be vexing. The question of low frequency manual observations providing comparable results to high frequency automated sampling also arises. Data collected from a replicated field experiment was intensively studied with the intention to give some statistically robust guidance on these issues. The experiment had nitrous oxide soil to air flux monitored within 10 m by 2.5 m plots by automated closed chambers under a 3h average sampling interval and by manual static chambers under a three day average sampling interval over sixty days. Observed trends in flux over time by the static chambers were mostly within the auto chamber bounds of experimental error. Cumulated nitrous oxide emissions as measured by each system were also within error bounds. Under the temporal response pattern in this experiment, no significant loss of information was observed after culling the data to simulate results under various low frequency scenarios. Within the confines of this experiment observations from the manual chambers were not spatially correlated above distances of 1m. Statistical power was therefore found to improve due to increased replicates per treatment or chambers per replicate. Careful after action review of experimental data can deliver savings for future work.

Chemical and structural analysis of enhanced biochars: thermally treated mixtures of biochar, chicken litter, clay and minerals.

In this study biochar mixtures comprising a Jarrah-based biochar, chicken litter (CL), clay and other minerals were thermally treated, via torrefaction, at moderate temperatures (180 and 220 °C). The objectives of this treatment were to reduce N losses from CL during processing and to determine the effect of both the type of added clay and the torrefaction temperature on the structural and chemical properties of the final product, termed as an enhanced biochar (EB). Detailed characterisation indicated that the EBs contained high concentrations of plant available nutrients. Both the nutrient content and plant availability were affected by torrefaction temperature. The higher temperature (220 °C) promoted the greater decomposition of organic matter in the CL and dissociated labile carbon from the Jarrah-based biochar, which produced a higher concentration of dissolved organic carbon (DOC). This DOC may assist to solubilise mineral P, and may also react with both clay and minerals to block active sites for P adsorption. This subsequently resulted in higher concentrations of plant available P. Nitrogen loss was minimised, with up to 73% of the initial total N contained in the feedstock remaining in the final EB. However, N availability was affected by both torrefaction temperature and the nature of the clay minerals added.

Estrogen mediated effects in the Sydney rock oyster, Saccostrea glomerata, following field exposures to sewage effluent containing estrogenic compounds and activity.

The Sydney rock oyster, Saccostrea glomerata, has been demonstrated as a useful biomonitor of estrogenic compounds following laboratory exposures, yet its utility in the assessment of estrogenic exposure and effects under field conditions requires investigation. To achieve this aim, S. glomerata were deployed in Newcastle, Australia in the effluent receiving marine waters of Burwood Beach WWTP (Burwood Beach "near", <50 m from outfall and Burwood Beach "far", 100-150 m from outfall) and reference locations (Redhead, Fingal Island 1 and Fingal Island 2) at depths of 4, 8 and 12 m for six weeks. Effluent receiving waters of Burwood Beach WWTP were found to be a suitable impact location, demonstrated via measurement of estrogenic compounds and activity throughout the deployment. Estrogenic compounds were detected (average of combined solids and liquid fractions) at average concentrations of: 1.42 ng/L for estrone, 0.69 ng/L for 17ß estradiol, 3.83 ng/L for estriol (E3), 0.56 ng/L for 17α-ethynylestradiol, 64.2 ng/L for bisphenol A, 7.51 ng/L for 4-nonylphenol and 5.93 ng/L for 4-tert-octylphenol. Total estrogenic activity was estimated at 4.48 ng/L EEQ via the Yeast Estrogen Screen (YES(®)) assay (average of combined solid and liquid fractions). Female vitellogenin gene expression was highest at Burwood Beach locations, yet no significant differences were detected among locations for either sex. Vitellogenin protein was significantly higher (p<0.05) in S. glomerata at Burwood Beach Near compared to reference locations for the 4 and 12 m depths. Increased proportions of females were found at Burwood Beach Near, at 4m depth (p<0.05). Both Burwood Beach locations had higher proportions of mature female gonadal development stages compared to reference locations (p<0.05). Oocyte area was highest at both Burwood Beach locations, but no significant differences were detected among locations. Findings provided further evidence that female S. glomerata may be a suitable candidate species for assessment of effects of estrogenic compounds in Australian waters.

Effects of 4-nonylphenol and 17alpha-ethynylestradiol exposure in the Sydney rock oyster, Saccostrea glomerata: Vitellogenin induction and gonadal development.

Adult Saccostrea glomerata were exposed to environmentally relevant concentrations of 4-nonylphenol (1microg/L and 100microg/L) and 17alpha-ethynylestradiol (5ng/L and 50ng/L) in seawater over 8 weeks. Exposures were performed to assess effects on vitellogenin induction and gonadal development during reproductive conditioning. Chronic direct estrogenicity within gonadal tissue was assessed via an estrogen receptor-mediated, chemical-activated luciferase reporter gene-expression assay (ER-CALUX). Estradiol equivalents (EEQ) were greatest in the 100microg/L 4-nonylphenol exposure (28.7+/-2.3ng/g tissue EEQ) while 17alpha-ethynylestradiol at concentrations of 50ng/L were 2.2+/-1.5ng/g tissue EEQ. Results suggest 4-nonylphenol may be accumulated in tissue and is partly resistant to biotransformation; maintaining its potential for chronic estrogenic action, while 17alpha-ethynylestradiol, although exhibiting greater estrogenic potency on biological endpoints possibly exerts its estrogenic action before being rapidly metabolised and/or excreted. A novel methodology was developed to assess vitellogenin using high-performance liquid chromatography (HPLC). Exposure to both 17alpha-ethynylestradiol (50ng/L) and 4-nonylphenol (100microg/L) produced increases in vitellogenin for females, whereas males exhibited increases in vitellogenin when exposed to 50ng/L 17alpha-ethynylestradiol only. Females exhibited greater vitellogenin responses than males at 50ng/L 17alpha-ethynylestradiol only. Histological examination of gonads revealed a number of individuals exhibiting intersex (ovotestis) in 50ng/L 17alpha-ethynylestradiol exposures. Male individuals in 1microg/L and 100microg/L 4-nonylphenol exposures and 5ng/L 17alpha-ethynylestradiol were at earlier stages of spermatogenic development than corresponding controls.

The characteristics of rhizosphere microbes associated with plants in arsenic-contaminated soils from cattle dip sites.

Soil microorganisms and plants were studied in samples of arsenic-contaminated soil from two cattle dip sites. The aim was to delineate the parameters that will determine the feasibility of future remediation by growing arsenic-accumulating plants, including the identity and characteristics of some rhizosphere soil microbes. The soil samples contained high total, but low soluble arsenic concentrations which, together with other properties, resembled the previously reported characteristics of dip-site soils from this region of rural Australia. A glasshouse trial demonstrated that dip-site rhizosphere microbes promoted arsenic accumulation by the grass Agrostis tenuis on contaminated dip-site soil without inhibition of growth. The arsenic content of the shoots was increased by 45%. We studied the colonization of roots of dip-site plants by mycorrhizal fungi and tentatively identified six genera of other fungi present in the soil samples. Two plant species growing at the sites, Kikuyu grass (the most abundant plant) and Rainbow fern, exhibited mixed infections of their roots by endomycorrhizal fungi (tentatively identified as Acaulospora and Gigaspora) and by soil-born pathogens. Five rhizosphere bacteria were identified to genus level and we determined the effect of arsenic on their growth. The two most prevalent strains differed greatly in their growth sensitivity to arsenate; Arthrobacter sp. being the most sensitive while Ochrobactrum sp. exhibited exceptional resistance to arsenate. Of the other, less prevalent strains, two were Bacillus spp. and the last, Serratia sp., was the most resistant to arsenite. These findings show the importance of understanding plant-soil microbe interactions for developing future strategies aimed at a phytoremediation-based approach to removing arsenic from soil at dip sites.

Enhancing cell survival of atrazine degrading Rhodococcus erythropolis NI86/21 cells encapsulated in alginate beads.

AIMS: To develop a method to produce beads with encapsulated Rhodococcus erythropolis NI86/21 with high cell density, extended shelf life, ease of handling and good atrazine degradation capabilities in both liquid and in agricultural soil. METHODS AND RESULTS: Our findings show that the supplementary recovery step in nutrient broth media shortly after cell encapsulation facilitates cell survival in both wet and dry beads upon extended storage at 4 degrees C. Air drying has little or no impact on encapsulated R. erythropolis cell's ability to degrade atrazine in liquid or soil. Bead storage for periods extending up to 12 months at 4 degrees C did not affect the capacity of R. erythropolis encapsulated cells to degrade atrazine in either BMN or nonsterile soil extracts. Bentonite-amended beads formulated with 1% skim milk and exposed to the supplementary growth step, outperformed all other bead formats. These beads provided adequate numbers of vigorous R. erythropolis cells in either liquid or soil media to degrade atrazine. CONCLUSIONS: Supplementary growth in nutrient broth media immediately following cell encapsulation greatly enhances R. erythropolis cells survival in both wet and dry beads upon extended storage at 4 degrees C. Wet and dried beads have similar capacity for atrazine degradation, and their usefulness and appeal in agronomic practise will only be known after bioassay evaluation and successful demonstration at field scale using incurred residues. SIGNIFICANCE AND IMPACT OF THE STUDY: R. erythropolis NI86/21 encapsulated cells have the potential to reduce residual atrazine in soil, thereby minimizing the likelihood of off-site transport to ground or river water and reduce the loss of crops because of phytotoxicity of residual herbicide. Owing to their ease of handling, storage and possible compatibilities with pre-existing mechanical equipment, dried bead formats are ideally suited for agricultural and remediational applications.

Atrazine degradation by encapsulated Rhodococcus erythropolis NI86/21.

AIMS: To develop an encapsulation procedure for Rhodococcus erythropolis NI86/21 and demonstrate its use as a slow-release inoculant for reducing atrazine levels in aquatic and terrestrial environments. METHODS AND RESULTS: Alginate encapsulation procedures were developed for the atrazine-degrading bacteria R. erythropolis NI86/21. Several bead amendments, including bentonite, powdered activated carbon (PAC) and skimmed milk (SM), were evaluated for slow release of R. erythropolis NI86/21 and efficacy of atrazine degradation. All bead types demonstrated a capacity to degrade atrazine in basal minimal nutrient buffer whilst continually releasing viable bacterial cells. We found that the addition of bentonite hastened cell release whilst SM sustained cell viability in bead formulations. Reducing the percentage of SM to 1% (w/v) resulted in faster rates of atrazine degradation in both liquid and soil, and was found to prolong cell survival upon bead storage. Limited oxygen transfer affects the capacity of the encapsulated R. erythropolis cells to degrade atrazine. CONCLUSIONS: Degradation studies have demonstrated the efficacy of R. erythropolis encapsulated cells to degrade atrazine in amended liquid and soil. However, in their current formulation, the wet alginate-based beads are impractical for field application because of their poor cell viability during storage. SIGNIFICANCE AND IMPACT OF THE STUDY: R. erythropolis NI86/21-encapsulated cells have the potential to reduce atrazine residues in a number of soil and water environments, possibly ensuring the continued registration and use of atrazine in agriculture by minimizing or eliminating nontarget effects.

Determination of DDT and its metabolites in cattle dip soil available in aqueous phase after remediation.

Soil taken from a former cattle tick dip site in NSW Australia, was remediated with a chemical leaching technology. The pre- and post-remediated soil (20g) was dispersed in water (100mL) and subjected to passive diffusion using polymeric membranes. The remediation reduced tDDT from 1174.3 microg/g to 102.9 microg/g (ash weight basis), which was further reduced to 43.2 microg/g with composting. The membranes accumulated 41.3 microg tDDT/g from the dip soil, 49.2 microg tDDT/g from the chemically leached soil and 3.1 microg tDDT/g from the leached composted soil. The chemical leaching removed over 90% of the tDDT, but released soil bound DDT, which was converted to DDE, while 2.99 microg/g was accumulated by the membranes from dip soil, 37.52 microg/g was accumulated from remediated soil. Composting, however, almost eliminated the availability for passive diffusion by the membranes from 50-60 microg/g in remediated soil to 3 -3.5 microg/g in composted soil. Variability studies of the membranes using eight replicates demonstrated that the accumulation by the membranes was reproducible with an average relative error of 20.3% for p,p'-DDT in soil type two, whilst the lowest average relative error for p,p'-DDE was 4.3%, suggesting that triplicate analyses will achieve acceptable accuracy.

Upper airway inflammation assessed by nasal lavage in compost workers: A relation with bio-aerosol exposure.

BACKGROUND: Exposure to microbial agents in the composting industry may cause work related airway inflammation. Nasal lavage (NAL) has been proposed as a noninvasive method to assess such effects in population studies. METHODS: Pre- and post-shift NAL were performed in the workers of a compost plant visited in 1995 (n = 14) and 1996 (n=15), of whom only four participated in both surveys. Total cells, cytokines and other inflammation markers were measured in NAL fluid, and pre-shift levels and post/pre concentration ratios were compared with NAL results obtained in the same periods in 10 and 9 controls, respectively, and with levels of airborne exposure to microbial agents endotoxin and beta(1,3)-glucan as measured in personal air samples. RESULTS: Job-title specific exposure levels in the first survey ranged from 75 to 527 EU/m(3) for endotoxin and from 0.54 to 4.85 microg/m(3) for beta(1,3)-glucan. In the second survey these values were lower, 29-285 EU/m(3) and 0.36-4.44 microg/m(3), respectively. In the first survey pre-shift NAL concentrations of total cells, MPO, IL-8, NO and albumin were significantly (1.1-4.8 fold) higher in compost workers than in controls. Post/pre ratios for various markers were significantly (1.2-3.2 fold) higher in compost workers in both surveys. NAL cells were mainly neutrophils, while eosinophils were only incidentally observed. A weak relation with exposure was found for pre-shift levels of MPO, uric acid and urea in the first survey. CONCLUSIONS: Occupational exposure of compost workers may cause acute and possibly (sub-)chronic inflammatory reactions in the upper airways, presumably induced by non-allergenic pro-inflammatory agents like endotoxins and beta(1, 3)-glucans.

Perceptions of the causes of bladder cancer, nasal cancer, and mesothelioma among cases and population controls.

To understand the reasons for underreporting of occupational cancers, we investigated cases' perceptions of the causes of cancer. As part of a case-control study in the province of British Columbia, Canada, 105 bladder cancer cases, 48 nasal cancer cases, 51 mesothelioma cases, and 159 population-based controls (frequency matched to cases on age and sex) were interviewed using structured questions about their smoking, medical, residential, occupational, and carcinogen exposure histories. We asked cases what they thought caused their disease, and asked population controls about their understanding of the etiologies of the three cancers. Most cases and controls (69%) indicated that they had "no idea" about causes, with the exception that the majority of mesothelioma cases (70%) recognized asbestos as a cause. Smoking was perceived as a cause of bladder cancer by 21 percent of cases. Many cases knew about the asbestos and smoking etiologies from discussions with their physicians. Chemicals were commonly cited as causes of nasal and bladder cancer, but very few specific known or probable carcinogens for these sites were named. Cases (12%) more frequently than controls (2%) thought prior disease or trauma was a cause for all three types of cancer. Other etiologic factors less frequently listed by subjects included environmental pollution, hereditary factors, drugs, and radiation. Most cases recognized the major cause of mesothelioma, but few subjects knew about lifestyle or occupational causes of bladder cancer or nasal cancer, suggesting that education about the multiple cancer risks of smoking and about occupational carcinogens needs to be improved.