Atrazine removal in agricultural infiltrate by bioaugmented polyvinyl alcohol immobilized and free Agrobacterium radiobacter J14a: a sand column study

Bench-scale sand column breakthrough experiments were conducted to examine atrazine removal in agricultural infiltrate by Agrobacterium radiobacter J14a (J14a) immobilized in phosphorylated-polyvinyl alcohol compared to free J14a cells. The effects of cell loading and infiltration rate on atrazine degradation and the loss of J14a were investigated. Four sets of experiments, (i) tracers, (ii) immobilized dead cells, (iii) immobilized cells, and (iv) free cells, were performed. The atrazine biodegradation at the cell loadings of 300, 600, and 900 mg dry cells L(-1) and the infiltration rates of 1, 3, and 6 cm d(-1) were tested for 5 column pore volumes (PV). The atrazine breakthrough results indicated that the immobilized dead cells significantly retarded atrazine transport. The atrazine removal efficiencies at the infiltration rates of 1, 3, and 6 cm d(-1) were 100%, 80-97%, and 50-70%, respectively. Atrazine degradation capacity for the immobilized cells was not significantly different from the free cells. Both infiltration rate and cell loading significantly affected atrazine removal for both cell systems. The bacterial loss from the immobilized cell system was 10-100 times less than that from the free cell system. For long-term tests at 50 PV, the immobilized cell system provided consistent atrazine removal efficiency while the atrazine removal by the free cells declined gradually because of the cell loss.     

Carbon, nitrogen balances and greenhouse gas emission during cattle feedlot manure composting

Carbon and N losses reduce the agronomic value of compost and contribute to greenhouse gas (GHG) emissions. This study investigated GHG emissions during composting of straw-bedded manure (SBM) and wood chip-bedded manure (WBM). For SBM, dry matter (DM) loss was 301 kg Mg(-1), total carbon (TC) loss was 174 kg Mg(-1), and total nitrogen (TN) loss was 8.3 kg Mg(-1). These correspond to 30.1% of initial DM, 52.8% of initial TC, and 41.6% of initial TN. For WBM, DM loss was 268 kg Mg(-1), TC loss was 154 kg Mg(-1), and TN loss was 1.40 kg Mg(-1), corresponding to 26.5, 34.5, and 11.8% of initial amounts. Most C was lost as CO2 with CH4 accounting for <6%. However, the net contribution to greenhouse gas emissions was greater for CH4 since it is 21 times more effective at trapping heat than CO2. Nitrous oxide (N2O) emissions were 0.077 kg N Mg(-1) for SBM and 0.084 kg N Mg(-1) for WBM, accounting for 1 to 6% of total N loss. Total GHG emissions as CO2-C equivalent were not significantly different between SBM (368.4 +/- 18.5 kg Mg(-1)) and WBM (349.2 +/- 24.3 kg Mg(-1)). However, emission of 368.4 kg C Mg(-1) (CO2-C equivalent) was greater than the initial TC content (330.5 kg Mg(-1)) of SBM, raising the question of the net benefits of composting on C sequestration. Further study is needed to evaluate the impact of composting on overall GHG emissions and C sequestration and to fully investigate livestock manure management options.     

Study of individual reactions of the sour compression process for the purification of oxyfuel-derived CO2

Following the feasibility study of sour compression process as a novel purification method of producing NO_x-free, SO₂-free oxyfuel-derived CO₂ using actual fluegas, in this paper, we present the study of the individual reactions taking place in the process in a controlled environment. We have previously showed that an increase of NO/NO₂ concentration in the inlet stream is beneficial for SO₂ removal as NO₂ promotes SO₂ oxidation and the further removal as liquid acid. In this study we show that the reaction SO₂ + NO₂ → SO₃ + NO does not take place significantly in the absence of liquid water at a range of conditions relevant to the sour compression process. When liquid water is present, SO₂ is oxidised by NO₂ regenerating NO with the rate of conversion of SO₂ being dependent on the acid concentration in the liquid. The formation of small liquid droplets where very low levels of pH (?0) can be reached is shown to be of great importance to the SO₂ + NO₂ conversion process.     

Complex mixtures that may contain mutagenic and/or genotoxic components: a need to assess in vivo target-site effect(s) associated with in vitro-positive(s)

A battery of short-term in vitro assays and/or in vivo protocols to evaluate single-agent mutagenicity and/or genotoxicity is available. However, a protocol to assess the effect(s) of complex mixtures in vivo following a positive test finding in vitro remains difficult. Complex interactions may occur in vivo because component pharmacokinetics increases the unpredictability of pharmacodynamic outcomes. The question arises as to whether in vitro mutagenic component(s) of a complex mixture, probably unidentified, reach target organ(s) in vivo at a sufficient concentration. To address the issue of an in vitro positive, standard in vivo chromosome damage assays to test both mixtures and fractions could be conducted but, to assess site-of-contact effects, the alkaline single cell-gel electrophoresis ("comet") assay or DNA reactivity (e.g., (32)P-postlabelling of DNA adducts) might be employed. A newer approach may be the derivation of a "biochemical-cell fingerprint" of potential target sites using infrared microspectroscopy. There is interest in platforms such as gene expression, proteomics, epigenomics or metabolomics as biomarkers of signature genotoxic or non-genotoxic mechanisms. One still needs to address whether a mutagenic and/or genotoxic component reaches a target organ. An approach to track levels of target-organ exposure may be to radio-label components with a short-lived positron-emitting radionuclide. The parent compound retains its physicochemical properties whilst allowing non-invasive in vivo tissue-specific imaging. However, determining target-organ concentration(s) and effect(s) in vivo remains a difficult challenge.     

21,000 Years of Ethiopian African monsoon variability recorded in sediments of the western Nile deep-sea fan

The Nile delta sedimentation constitutes a continuous high-resolution record of Ethiopian African monsoon (EAM) regime intensity. Multi-proxy analyses performed on hemipelagic sediments deposited on the Nile deep-sea fan allow the quantification of the Saharan aeolian dust and the Blue/White Nile River suspended matter frequency fluctuations during the last 21,000 years. The radiogenic strontium and neodymium isotopes, clay mineralogy, elemental composition and preliminary palynological analyses reveal large changes in source components, oscillating between a dominant aeolian Saharan contribution during the Last Glacial Maximum (LGM) and the late Holocene (~4,000–2,000 years), a dominant Blue/Atbara Nile River contribution during the early Holocene (15,000–8,000 years) and a probable White Nile River contribution during the middle Holocene (8,000–4,000 years). The following main features are highlighted: (1) The rapid shift from the LGM arid conditions to the African Humid Period (AHP) started at about 15,000 years. The AHP extends until 8,000 years, and we suggest that the EAM maximum between 15,000 and 8,000 years is responsible for a larger Blue/Atbara Nile sediment load and freshwater input into the eastern Mediterranean Sea. (2) The transition between the AHP and the arid late Holocene is gradual and occurs in two main phases between 8,400–6,500 years and 6,500–3,200 years. We suggest that the main rain belt shifted southward from 8,000 to ~4,000 years and was responsible for progressively reduced sediment load and freshwater input into the eastern Mediterranean Sea. (3) The aridification along the Nile catchments occurred from ~4,000 to 2,000 years. This dry period, which culminates at 3,200 year, seems to coincide with a re-establishment of increased oceanic primary productivity in the western Mediterranean Sea. Such a pattern imposes a large and rapid northward shift of the rain belt over the Ethiopian highlands (5–15°N) since 15,000 years. Precipitation over Ethiopia increased from 15,000 to 8,000 years. It was followed by a gradual southward shift of the rain belt over the equator from 8,000 to 4,000 years and finally a large shift of the rain belt south the equator between 4,000 and 2,000 years inducing North African aridification. We postulate that the decrease in thermohaline water Mediterranean circulation could be part of a response to huge volumes of freshwater delivered principally by the Nile River from 15,000 to 8,000 years in the eastern Mediterranean.     

Behavior of dialifor,dimethoate, and methidathion in artificially fortified grape juice processed into wine

Abstract

Dialifor and methidathion were added to diluted “Zinfandel”; grape concentrate at 25 ppm and dimethoate at 1.0 and 25 ppm prior to fermentation with Saccharomyces cerevisiae. The finished wine 56 days later contained 10% (2.5 ppm) of the dialifor, 46% (12 ppm) of the methidathion and 85% (21 and 0.98 ppm) of the dimethoate added to the grape must. Residues in wine stored at 24°C dissipated by hydrolysis; half‐lives in wine were 7 days for dialifor and methidathion and 30 days for dimethoate. Residues were unchanged in wine in frozen storage for one year. Analysis of seven commercial wines for dimethoate indicated less than 0.03 ppm dimethoate was present; identity could not be confirmed by thin‐layer chromatography at this level.     

The Impact of Stratospheric Ozone on Tropospheric Air Quality

A background of ozone (O₃), principally of stratospheric origin, is present in the lower free troposphere. Typical mean O₃ levels of 50 ppb, 40 ppb, and 30 ppb are encountered here in spring, summer, and fall, respectively. Maximum hourly O₃ concentrations which are twice these mean values can be expected. Ozone from the free troposphere is routinely brought down to ground level under turbulent atmospheric conditions. Deep and rapid Intrusions of stratospheric air into the lower troposphere are associated with low-pressure troughs and occur regularly. In the mid troposphere, O₃ levels as high as 300 ppb are found within these intrusions. Observational data showing these intrusions, containing high O₃ concentrations, to directly reach ground level are currently lacking. Over the United States, an intrusion was present aloft on 8 9% of the days in 1978. The frequency, however, is somewhat reduced in summer and a northward movement is evident. During 1978, no intrusion occurred south of 30°N between June and August and none south of 40 °N in August.

The hypothesis that low levels of stratospheric O₃ produce disproportionately large amounts of O₃ in the polluted atmosphere cannot be supported from currently known chemistry but should be studied further. The experimental technique involving a ⁷Be/O₃ ratio to estimate the daily stratospheric component of ground level O₃ is unverified and considered to be inadequate for air quality applications. Estimates resulting from such a technique are considered uncertain by a factor of more than three. Specially designed aircraft studies provide the best means to determine quantitatively the impact of stratospheric O₃ on ground level air quality.     

Evaluation of Trickle Bed Air Biofilter Performance as a Function of Inlet VOC Concentration and Loading,and Biomass Control

ABSTRACT

The 1990 Amendments to the Clean Air Act have stimulated strong interest in the use of biofiltration for the economical, engineered control of volatile organic compounds (VOCs) in effluent air streams. Trickle bed air biofilters (TBABs) are especially applicable for treating VOCs at high loadings. For long-term, stable operation of highly loaded TBABs, removal of excess accumulated bio-mass is essential. Our previous research demonstrated that suitable biomass control for TBABs was achievable by periodic backwashing of the biofilter medium. Backwashing was performed by fluidizing the pelletized biological attachment medium with warm water to about a 40% bed expansion. This paper presents an evaluation of the impact of backwashing on the performance of four such TBABs highly loaded with toluene. The inlet VOC concentrations studied were 250 and 500 ppmv toluene, and the loadings were 4.1 and 6.2 kg COD/m³ day (55 and 83 g toluene/m³ hr). Loading is defined as kg of chemical oxygen demand per cubic meter of medium per day. Performance deterioration at the higher loading was apparently due to a reduction of the specific surface of the attached biofilm resulting from the accumulation of excess biomass. For a toluene loading of 4.1 kg COD/m³ day, it was demonstrated that the long-term performance of biofilters with either inlet concentration could be maintained at over 99.9% VOC removal by employing a backwashing strategy consisting of a frequency of every other day and a duration of 1 hr.