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Coastal Bangladesh experiences significant poverty and hazards today and is highly vulnerable to climate and environmental change over the coming decades. Coastal stakeholders are demanding information to assist in the decision making processes, including simulation models to explore how different interventions, under different plausible future socio-economic and environmental scenarios, could alleviate environmental risks and promote development. Many existing simulation models neglect the complex interdependencies between the socio-economic and environmental system of coastal Bangladesh. Here an integrated approach has been proposed to develop a simulation model to support agriculture and poverty-based analysis and decision-making in coastal Bangladesh. In particular, we show how a simulation model of farmer's livelihoods at the household level can be achieved. An extended version of the FAO's CROPWAT agriculture model has been integrated with a downscaled regional demography model to simulate net agriculture profit. This is used together with a household income–expenses balance and a loans logical tree to simulate the evolution of food security indicators and poverty levels. Modelling identifies salinity and temperature stress as limiting factors to crop productivity and fertilisation due to atmospheric carbon dioxide concentrations as a reinforcing factor. The crop simulation results compare well with expected outcomes but also reveal some unexpected behaviours. For example, under current model assumptions, temperature is more important than salinity for crop production. The agriculture-based livelihood and poverty simulations highlight the critical significance of debt through informal and formal loans set at such levels as to persistently undermine the well-being of agriculture-dependent households. Simulations also indicate that progressive approaches to agriculture ( i.e. diversification) might not provide the clear economic benefit from the perspective of pricing due to greater susceptibility to climate vagaries. The livelihood and poverty results highlight the importance of the holistic consideration of the human–nature system and the careful selection of poverty indicators. Although the simulation model at this stage contains the minimum elements required to simulate the complexity of farmer livelihood interactions in coastal Bangladesh, the crop and socio-economic findings compare well with expected behaviours. The presented integrated model is the first step to develop a holistic, transferable analytic method and tool for coastal Bangladesh.

Phytotoxins are a large class of highly diverse emerging environmental contaminants that have been detected at high concentrations in plants, water and soils. This study presents a novel modelling approach for assessing the fate of plant toxins in the soil–plant–atmosphere continuum, developed for the specific case of ptaquiloside (PTA), a carcinogenic phytotoxin produced by Pteridium aquilinum . The mechanistic model DAISY has been adapted for reproducing phytotoxin dynamics in plants, covering processes such as toxin generation in the canopy, wash off by precipitation and toxin recovery in the canopy after depletion events. Transport of the toxin in the soil was simulated by the advection–dispersion equation assuming weak sorption and degradation for two Danish soils. The model simulates realistic toxin contents in the plant during the growing season, where the actual PTA content is dynamic and a function of the biomass. An average of 48% of the PTA produced in the canopy is washed off by precipitation, with loads in the soil often in the order of mg m ?2 and up to a maximum of 13 mg m ?2 in a single rain event. Degradation in the soil removes 99.9% of the total PTA input to the soil, while only 0.1% leaches into the soil. The median annual flux-averaged predicted environmental concentrations during single events are often in the order of μg L ?1 , reaching up to 60 μg L ?1 for the worst-case scenario. The simulated results for both degradation and wash off are of the same order of magnitude as the published data. Based on the results, we conclude that DAISY, with the newly implemented processes, is a useful tool for understanding, describing and predicting the fate of PTA in the soil. Further work comparing the model results with real data is needed for the calibration and validation of the model.

The radical is the key intermediate in the atmospheric oxidation of benzaldehyde, and its further chemistry contributes to local air pollution. The reaction mechanisms of the radical with NO, NO 2 , and NO 3 were studied by quantum chemistry calculations at the CCSD(T)/CBS//M06-2X/def2-TZVP level of theory. The explicit potential energy curves were provided in order to reveal the atmospheric fate of the radical comprehensively. The main products of the reaction of with NO are predicted to be , CO 2 and NO 2 . The reaction of with NO 2 is reversible, and its main product would be C 6 H 5 C(O)O 2 NO 2 which was predicted to be more stable than PAN (peroxyacetyl nitrate) at room temperature. The decomposition of C 6 H 5 C(O)O 2 NO 2 at different ambient temperatures would be a potential long-range transport source of NO x in the atmosphere. The predominant products of the reaction are predicted to be C 6 H 5 C(O)O 2 H, C 6 H 5 C(O)OH, O 2 and O 3 , while HO˙ is of minor importance. So, the reaction of with would be an important source of ozone and carboxylic acids in the local atmosphere, and has less contribution to the regeneration of HO˙ radicals. The reaction of with NO 3 should mainly produce , CO 2 , O 2 and NO 2 , which might play an important role in atmospheric chemistry of peroxy radicals at night, but has less contribution to the night-time conversion of ( and RO˙) to ( and HO˙) in the local atmosphere. The results above are in good accordance with the reported experimental observations.

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Long-term laborious and thus costly monitoring of phosphorus (P) fractions is required in order to provide reasonable estimates of the levels of bioavailable phosphorus for eutrophication studies. A practical solution to this problem is the application of passive samplers, known as Diffusive Gradient in Thin films (DGTs), providing time-average concentrations. DGT, with the phosphate adsorbent Fe-oxide based binding gel, is capable of collecting both orthophosphate and low molecular weight organic phosphorus (LMWOP) compounds, such as adenosine monophosphate (AMP) and myo-inositol hexakisphosphate (IP6). The diffusion coefficient ( D ) is a key parameter relating the amount of analyte determined from the DGT to a time averaged ambient concentration. D at 20 °C for AMP and IP6 were experimentally determined to be 2.9 × 10 ?6 cm 2 s ?1 and 1.0 × 10 ?6 cm 2 s ?1 , respectively. Estimations by conceptual models of LMWOP uptake by DGTs indicated that this fraction constituted more than 75% of the dissolved organic phosphorus (DOP) accumulated. Since there is no one D for LMWOP, a D range was estimated through assessment of D models. The models tested for estimating D for a variety of common LMWOP molecules proved to be still too uncertain for practical use. The experimentally determined D for AMP and IP6 were therefore used as upper and lower D , respectively, in order to estimate minimum and maximum ambient concentrations of LMWOP. Validation of the DGT data was performed by comparing concentrations of P fractions determined in natural water samples with concentration of P fractions determined using DGT. Stream water draining three catchments with different land-use (forest, mixed and agriculture) showed clear differences in relative and absolute concentrations of dissolved reactive phosphorus (DRP) and dissolved organic P (DOP). There was no significant difference between water sample and DGT DRP ( p 0.05). Moreover, the upper and lower limit D for LMWOP proved reasonable as water sample determined DOP was found to lie in-between the limits of DGT LMWOP concentrations, indicating that on average DOP consists mainly of LMWOP. “Best fit” D was determined for each stream in order to practically use the DGTs for estimating time average DOP. Applying DGT in a eutrophic lake provided insight into P cycling in the water column.

The sorption of hydrophobic organic compounds (HOC) onto microplastics is relatively well reported in the literature, while their desorption remains poorly investigated, especially in biological fluids. The present study investigated the sorption and desorption of progesterone on polyethylene (PE), polypropylene (PP), and polystyrene (PS) microplastics. The sorption experiments showed that the equilibrium was reached in a few hours for all plastics. A sorption efficiency of 357.1 μg g ?1 was found for PE and PS, and 322.6 μg g ?1 for PP. Sorption experiments indicated that adsorption would certainly happen via surface sorption and a potentially pore-filling mechanism. The desorption was carried out in Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF), whose formulations were more complex than similar models reported so far. It has been found that the desorption was higher in SIF as compared to SGF, due to micelle formation in SIF promoting the pollutant solubilization. The sorption of pepsin onto microplastics has also been revealed, suggesting a competition between pollutants and pepsin for sorption sites and a potent reduction in pollutant solubilization. This study indicates that the ingestion of microplastics could be considered as an additional route of exposure to pollutants and therefore emphasizes pollutant bioavailability for aquatic organisms.

To explore the oxidation effects and mechanisms for the oxidation of alkanes by H 2 O 2 in a Fenton system catalyzed by two types of iron bound to soil organic matter (Fe-SOM) in crude oil-contaminated soil, an oxidation experiment was performed in active Fe-SOM and Fe-SOM systems. The results showed that the TPH removal ability of active Fe-SOM (average 0.36 g TPH/g Fe-SOM) was 2.25-fold higher than the corresponding value of Fe-SOM. Active Fe-SOM contained both –NH 2 and –OH functional groups, and had a higher content of iron with high binding energy, while Fe-SOM only contained –NH 2 groups. Thus, a large yield of hydroxyl radicals (·OH) was generated (8.92 a.u.) by active Fe-SOM catalyzing the decomposition of H 2 O 2 , while the corresponding yield of ·OH in the Fe-SOM system was only 4.81 a.u. In addition, the removal efficiency of C 17 –C 23 (70%) was comparable to that of C 24 –C 30 (69%), not restricted by the hydrophobicity of different alkanes. The alkane removal by active Fe-SOM was higher than that by Fe-SOM, although the content of Fe-SOM was double that of active Fe-SOM. In summary, the active Fe-SOM formed in the soil sample containing humic acid-like and hydrophobic acid derivates could catalyze H 2 O 2 decomposition to improve the removal efficiency of crude oil in contaminated soil.

By a combination of transient absorption spectroscopy and steady-state irradiation experiments, we investigated the transformation of phenol and furfuryl alcohol (FFA) sensitised by irradiated 4-carboxybenzophenone (CBBP). The latter is a reasonable proxy molecule to assess the reactivity of the excited triplet states of the chromophoric dissolved organic matter that occurs in natural waters. The main reactive species for the transformation of both phenol and FFA was the CBBP triplet state, despite the fact that FFA is a commonly used probe for 1 O 2 . In the case of FFA it was possible to develop a simple kinetic model that fitted well the experimental data obtained by steady-state irradiation, in a wide range of FFA concentration values. In the case of phenol the model was made much more complex by the likely occurrence of back reactions between radical species ( e.g. , phenoxyl and superoxide). This problem can be tackled by considering only the experimental data at low phenol concentration, where the degradation rate increases linearly with concentration. We do not recommend the use of 1 O 2 scavengers/quenchers such as sodium azide to elucidate CBBP photoreaction pathways, because the azide provides misleading results by also acting as a triplet-state quencher. Based on the experimental data, we propose a methodology for the measurement of the CBBP triplet-sensitisation rate constants from steady-state irradiation experiments, allowing for a better assessment of the triplet-sensitised degradation of emerging contaminants.

The in situ manufacture of cured-in-place-pipe (CIPP) plastic liners in damaged sewer pipes is an emerging mobile source of anthropogenic air pollution. Evidence indicates volatile organic compounds (VOCs) can be released before, during, and after manufacture. The chemical composition of a popular uncured styrene-based CIPP resin was examined, along with the VOCs that remained in the new cured composite. The roles of curing temperature and heating time in waste discharged into the air were examined. Uncured resin contained approximately 39 wt% VOCs. Multiple hazardous air pollutants were present, however, 61 wt% of the uncured resin was not chemically identified. A substantial mass of VOCs (8.87 wt%) was emitted into the air during manufacture, and all cured composites contained about 3 wt% VOCs. Some VOCs were created during manufacture. Curing temperature (65.5–93.3 °C) and heating time (25–100 min) did not cause different composite VOC loadings. High styrene air concentrations inhibited the detection of other VOCs in air. It is estimated that tens of tons of VOCs may be emitted at a single CIPP manufacturing site. Regulators should consider monitoring, and potentially regulating, these growing mobile air pollution and volatile chemical product sources as they are operating in urban and rural areas often in close proximity to residential and commercial buildings.

Nitrogen (N) loss from rice production systems in the form of ammonia (NH 3 ) can be a significant N loss pathway causing significant economic and environmental costs. Yet, data on NH 3 fluxes in wetland rice ecosystems are still very scarce which limits the accuracy of national and global NH 3 budgets. We measured the NH 3 fluxes in situ in a wetland rice field and estimated emission factors (EF) under two soil management systems ( i.e. conventional tillage, CT and strip tillage, ST); two residue retention levels ( i.e. 15%, LR and 40% crop residue by height, HR); and three N fertilization rates ( i.e. 108, 144 and 180 kg N ha ?1 ) in two consecutive years (2019 and 2020). The highest NH 3 peaks were observed within the first 3 days after urea application. The mean and cumulative NH 3 fluxes significantly increased with the increases in N fertilization rates and were 18.5% and 18.6% higher in ST than in CT in 2020 but not in 2019. Overall, the highest mean NH 3 fluxes were in 180 kg N ha ?1 coupled with either HR or LR and ST or CT. In 2019, the NH 3 EF was unchanged by any treatments. In 2020, the lower EF was in CT coupled with LR (15%) than all other treatment combinations, where ST with HR showed the highest EF (20%). Likewise, the lowest N rate (108 kg N ha ?1 ) in ST had the highest NH 3 EF (20%) that was similar to higher N rates (144 and 180 kg N ha ?1 ) in the same tillage treatment and to 180 kg N ha ?1 in CT. Our results highlight that NH 3 fluxes in rice field particularly the effects of ST correlated with higher soil pH and NH 4 + content and lower redox potential. Our results highlight that NH 3 fluxes are a potentially large N loss pathway in wetland rice under conventional and decreased soil disturbance regimes.