Behavior of chlorpyrifos and its major metabolite TCP (3,5,6-trichloro-2-pyridinol) in agricultural soils amended with drinking water treatment residuals

Purpose

Chlorpyrifos can be effectively adsorbed by drinking water treatment residuals (WTR), ubiquitous and non-hazardous by-products of potable water production. The major metabolite 3,5,6-trichloro-2-pyridinol (TCP) was found to be much more mobile and toxic than its parent chlorpyrifos. To assess the feasibility of WTR amendment for attenuation of chlorpyrifos and TCP pollution, the sorption/desorption and degradation behavior of chlorpyrifos and TCP in WTR-amended agricultural soils was examined in the present study.

Materials and methods

Two representative agricultural soils were sampled from southern and northern China, respectively. The soils were amended with WTR at the rates of 0, 2, 5, and 10 % (w/w). Batch sorption/desorption test were applied to investigate the sorption/desorption characteristics of chlorpyrifos and TCP in WTR-amended soils. The influence of WTR amendment on chlorpyrifos degradation and TCP formation was evaluated using the incubation test, and its effect on the soil bacterial abundance was further studied through DNA extraction and PCR amplification.

Results and discussion

Results showed that WTR amendment (0–10 %, w/w) significantly enhanced the retention capacity of chlorpyrifos and TCP in both soils examined (P < 0.05). Fractionation analyses further demonstrated that the bioavailability of chlorpyrifos was considerably reduced by WTR amendment, resulting in a decreased chlorpyrifos degradation rate. The WTR amendment also significantly reduced the mobility of TCP formed in chlorpyrifos-contaminated soils (P < 0.001). The chlorpyrifos toxicity to soil bacteria community was largely mitigated following WTR amendment, resulting in increased total bacterial abundance.

Conclusions

Results obtained in the present study indicate a great deal of potential for the beneficial reuse of WTR as soil amendments for chlorpyrifos and TCP pollution control.

     

Sediment transport below a small alpine reservoir desilted by controlled flushing: field assessment and one-dimensional numerical simulation

Purpose

Sediment transport and riverbed sedimentation were investigated in an alpine stream below a small hydropower reservoir desilted by a controlled sediment flushing (CSF) operation. The term “controlled” refers to the operational tasks implemented to mitigate the downstream environmental impact of the operation. The experimental dataset acquired before, during, and after the CSF was also used to carry out and calibrate a one-dimensional sediment transport model of the monitored event.

Materials and methods

The investigated reservoir is located in the central Italian Alps, and its original storage was 160,000 m³, about 30% filled by a mixture of sand and silt/clay before the CSF. Downstream sediment concentration was controlled by releasing clear water from upstream reservoirs and regulating the work of earth-moving equipment in the emptied reservoir. A 3.6-km-long reach with average slope of 0.015 was monitored: concentration and grain size of suspended sediment were measured during the CSF and the riverbed alteration was evaluated by volumetric sampling and measurements of the deposits’ thickness. Sedimentation and River Hydraulics—One Dimensional (SRH-1D) was used to simulate sediment transport during the monitored CSF. Model parameters were calibrated by comparing the computed and the observed amount of sediment deposited along the study reach.

Results and discussion

Sediment flushing was carried out in October 2010 for 3 days. Ca. 16,000 m³ of sediment were evacuated, representing approximately 30% silt/clay and 70% sand. 2.4 Mm³ of clear water was released to reduce sediment concentration and increase transport capacity downstream. About 3000 m³ of sand was deposited in the study reach after the CSF, with maximum height up to 0.2 m. Although the riverbed before the CSF was simply set as mono-granular, after calibrating the parameters, good agreement was achieved between the depositional pattern computed by SRH-1D and the one observed, both in terms of deposit thickness and grain size of deposited sediment. The sensitivity analysis revealed a major role of the parameters controlling bed mixing processes in affecting the simulated deposition after the CSF.

Conclusions

Sediment below 0.1 mm in diameter was not detected in river deposits after the flushing: the effects on river biota associated with substrate clogging by very fine sediment were therefore minimized. After proper calibration, 1-D sediment transport modeling can effectively support the planning of CSF operations: to minimize the downstream environmental effects, concurrently achieving acceptable flushing efficiency, the analyzed scenarios as well as the model outputs need to be carefully evaluated from a multidisciplinary perspective.

     

Beta-carotene isomer composition of sub- and supercritical carbon dioxide extracts. Antioxidant activity measurement

In the present work sub- and supercritical extraction conditions using carbon dioxide were studied in order to obtain extracts with different compositions from the green microalgae Dunaliella salina. Different compositions of beta-carotene isomers were identified in the extracts by using HPLC-DAD. Also, antioxidant activity of the extracts was measured using a TEAC assay. An experimental design was applied considering two factors, extraction pressure and temperature, in a wide range of values, trying to maximize the extraction yield. Higher yields were obtained at high pressures and low temperatures, that is, at higher CO2 densities. Attempts were made to correlate the antioxidant activity of the extracts with their chemical composition by means of principal component analysis. A certain relationship was found between their antioxidant activity and the isomeric composition of beta-carotenes. As a result, an original equation is proposed to predict the antioxidant activity of extracts from D. salina in terms of the ratio 9-cis-beta-carotene/all-trans-beta-carotene, the concentration of alpha-carotene, and, especially, the concentration of 9-cis-beta-carotene.     

Migration studies to assess the safety in use of a new antioxidant active packaging

Both specific and overall migration tests have been applied to new experimental food packaging-active plastic films with antioxidant properties, including in its composition a natural rosemary extract. Determination of volatile and semivolatile compounds migrating from plastic to the four established simulants showed that both specific and overall migration was very low. The results obtained gave values 20 times lower than the established limits in the worst case. So, from the point of view of health risk, the new active packaging can be considered as safe. Analytical procedure used provided the necessary information about the migration behavior, with good analytical characteristics and detection limits in the sub mug kg(-1) range. Besides, no significant difference was found between laboratory and factory-made samples, which is an important issue for industrial production, the next step in the development of the new antioxidant active film.     

Threshold wind velocity as an index of soil susceptibility to wind erosion under variable climatic conditions

Wind erosion starts when the threshold wind velocity (µ_t) is exceeded. We evaluated the sensitivity of µ_t to determine the wind erosion susceptibility of soils under variable climatic conditions. Three years field data were used to calculate µ_t by means of the equation µ_t = ū ‐ σ Φ⁻¹ (γ), where ū is the mean wind speed (m s⁻¹), σ the ū standard deviation (m s⁻¹), γ the saltation activity and Φ the standard normal distribution function of γ. Saltation activity was measured with a piezoelectric sensor (Sensit). Results showed that ū of the whole studied period (3·41 m s⁻¹) was lower than µ_t (7·53 m s⁻¹), therefore, wind erosion was produced mainly by wind gusts. The µ_t values ordered in the sequence: Winter (6·10 m s⁻¹) < Spring (8·22 m s⁻¹) = Summer (8·28 m s⁻¹) < Autumn (26·48 m s⁻¹). Higher µ_t values were related to higher air humidity and lower wind speeds and temperatures. The µ_t values did not agree with the erosion amounts of each season, which ordered as follows: Summer (12·88 t ha⁻¹) > Spring (3·11 t ha⁻¹) = Winter (0·17 t ha⁻¹) = Autumn (no erosion). Low µ_t and erosion amounts of Winter were produced by a scarce number of gusts during eroding storms. We concluded that µ_t is useful as an index of soil susceptibility to wind erosion of different climatic periods. The use of a unique µ_t value in wind erosion prediction models can lead to erroneous wind erosion calculations. Copyright © 2008 John Wiley & Sons, Ltd.     

Diversity characterisation of broccoli (Brassica oleracea L. var. italica Plenck) landraces for their on-farm (in situ) safeguard and use in breeding programs

Brassica oleracea L. is an important species that originated in the eastern Mediterranean area. From there, B. oleracea L. subsp. capitata (L.) DC. convar. botrytis (L.) Alef. var. italica Plenck (broccoli) was introduced into Italy where considerable diversification took place. Several landraces of broccoli, which are highly appreciated by local people for their organoleptic traits, are presently cultivated in both large fields and home gardens. In this study, 10 landraces, 4 synthetics derived from landraces and 4 of the most used F1 hybrids were characterised for morpho-physiological and molecular traits with the principal aim of feeding information into the landrace protection schemes being developed in Italy and into breeding programs. The landraces and derived synthetics are well differentiated from each other and from the F1 hybrids for important agronomic and genetic traits. The principal component analysis based on analysis of morpho-physiological traits showed that overall the 2 main components accounted for 67.74 % of the total variation. The neighbour joining tree, based on 23 microsatellite markers, grouped accessions into 2 main clusters. One includes one synthetic variety and 2 F1 hybrids, while the other cluster includes all the other accessions. There were also several sub clusters. Most of the materials examined showed within-accession diversity. The information gathered in this study can be used to protect landraces through the schemes presently being developed in Italy and to register them in the European common catalogue of “conservation varieties”. In situ (on-farm) conservation of landrace diversity is discussed with reference to landrace use.     

Carotenogenesis up-regulation in Scenedesmus sp. using a targeted metabolomics approach by liquid chromatography-high-resolution mass spectrometry

Carotenoids have potent antioxidant activity as well as therapeutic value, and their formation has been seen to be induced in algae by stress, including high-salt culture conditions. A differential profiling of carotenoids was conducted using a targeted metabolomics approach with accurate mass data generated by liquid chromatography-electrospray-time-of-flight (LC-ESI-TOF) mass spectrometry followed by postacquisition filtering based on isotope patterns and mass defects to detect carotenoids up-regulated in Scenedesmus sp. exposed to high-salt conditions. Algal cultures treated with high concentrations of sodium acetate or sodium chloride were found to cause an increase in various carotenoids. On the basis of differential analysis, astaxanthin and canthaxanthin increased upon salt treatment. Astaxanthin, in its free form and as fatty acid esters, was seen to increase in Scenedesmus sp. using accurate mass MS. A few other carotenoid compounds increased upon salt treatment, including echinenone and adonirubin, involved in the pathway of astaxanthin biosynthesis from β-carotene, as well as isomers of astaxanthin and canthaxanthin. A time course study of acetate treatment was done to observe the time-dependent up-regulation of carotenogenesis.