Pesticide and nitrate contamination of soil and groundwater from agriculture is an environmental and public health concern worldwide. Simazine, 6-chloro-N2,N4-diethyl-1,3,5-triazine-2,4-diamine, is a triazine herbicide used in agriculture for selective weed control with several types of crops and it is frequently applied to soils receiving N-fertilizers. Degradation experiments were performed in the laboratory to assess whether the biodegradation of simazine in soil may be influenced by the presence of urea. Simazine degradation rates under different experimental conditions (presence/absence of urea, microbiologically active/sterilized soil) were assessed together with the formation, degradation and transformation of its main metabolites in soil. Simazine degradation was affected by the presence of urea, in terms both of a smaller half-life (t(1/2)) and of a higher amount of desethyl-simazine formed. The soil bacterial community was also studied. Microbial abundances were determined by epifluorescence direct counting. Moreover in situ hybridization with rRNA-targeted fluorescent oligonucleotide probes was used to analyze the bacterial community structure. Fluorescent in situ hybridization (FISH) was used to detect specific groups of bacteria such as the alpha,beta,gamma-subdivisions of Proteobacteria, Gram-positive bacteria with a high G + C DNA content, Planctomycetes, Betaproteobacterial ammonia-oxidizing bacteria and nitrifying bacteria. The presence of the herbicide and/or urea affected the bacterial community structure, showing that FISH is a valuable tool for determining the response of bacterial populations to different environmental conditions.

Electrospray ionization mass spectrometry has been used to study the possible non-covalent interaction between oligonucleotides and beauvericin (B) mycotoxin. Beauvericin-oligonucleotide adduct formation was observed even at low mycotoxin concentration (25 pmol/microL). Adducts were found with different numbers of B ligands attached. The selectivity of binding of B ligands to two different oligonucleotides has been shown to be similar indicating that beauvericin does not have a strongly preferred base sequence or base site in the DNA. In a competitive complexation reaction, beauvericin forms specific adducts with oligonucleotide while another mycotoxin, nigeromicin, which causes apoptosis without fragmentation of DNA, does not.

Risks posed by antifouling agents (irgarol 1051, diuron and dichlofluanid) to the aquatic environment of the Gulf of Napoli have been estimated. Seawater samples were collected monthly in selected harbours and marinas of this area during the boating season (March to November 2005) and off-season (January 2006). Concentration levels have been measured, and the resulting data used to perform a probabilistic ecological risk assessment independently on each biocide. Diuron exhibited higher concentration levels than irgarol 1051 in all the investigated locations: Dissolved concentrations of diuron ranged from <1 to 1,380 ng l −1 , whereas dissolved concentrations of irgarol 1051 ranged from <0.2 to 173 ng l −1 . Contamination appears to be largely dependent on the type and configuration of sampling sites and on the residence time and the density of boats. High levels of booster biocides were associated with marinas housing several recreational water craft and/or fishing boats, whilst commercial ports usually exhibited low concentrations. A seasonal influence was observed, with peak and lowest values found in early summer months and during winter, respectively. The comparison of the respective toxicity benchmarks, expressed as 10th percentiles, suggests that plant species are more sensitive to irgarol 1051 (297 ng l −1 ) than diuron (4,846 ng l −1 ). Based on these conservative effect thresholds for plants, ecological risk from the single investigated biocides can be judged to be low in the study area.

No abstract

SUMMARY:The results of Monte Carlo simulations of systems of rodlike molecules with semiflexible terminal groups are compared with those of systems with terminal groups at a fixed angle s with respect to the rigid core and with those of a system containing the rigid cores alone in the same total volume. The nematic/ isotropic transition temperature decreases with increasing flexibility or with increasing s. For semiflexible groups, the transition is coupled with a conformational change favouring more extended conformations in the nematic phase. The results of the simulations are discussed in connection with those obtained for similar models in the recent literature and with the predictions of the Maier-Saupe and Flory-Ronca-Irvine theories.