The relative importance of mercury methylation and demethylation in rice paddy soil varies depending on the presence of rice plants.

Neurotoxic methylmercury (MeHg) accumulates in rice grain from paddy soil, where its concentration is controlled by microbial mercury methylation and demethylation. Both up- and down-regulation of methylation is known to occur in the presence of rice plants in comparison to non-vegetated paddy soils; the influence of rice plant presence/absence on demethylation is unknown. To assess the concurrent influence of rice plant presence/absence on methylation and demethylation, and to determine which process was more dominant in controlling soil MeHg concentrations, we maintained six rhizoboxes of paddy soil with and without rice plants. At the peak of plant growth, we simultaneously measured ambient MeHg, ambient inorganic mercury (IHg), and potential rate constants of methylation and demethylation (Kmeth and Kdemeth) in soil using stable isotope tracers and ID-GC-ICPMS. We also measured organic matter content, elemental S, and water-extractable sulfate. We found MeHg concentrations were differentially controlled by MeHg production and degradation processes, depending on whether plants were present. In non-vegetated boxes, MeHg concentration was controlled by Kmeth, as evidenced by a strong and positive correlation, while Kdemeth had no relation to MeHg concentration. These results indicate methylation was the dominant driver of MeHg concentration in non-vegetated soil. In vegetated boxes, Kdemeth strongly and negatively predicted MeHg concentration, indicating that demethylation was the dominant control in soil with plants. MeHg concentration, Kmeth, and % MeHg all had significantly less variance in vegetated than in non-vegetated soils due to a consistent elimination of greater values. This pattern suggests that reduced MeHg production capacity was a secondary control on MeHg concentrations in vegetated soils. We observed no difference in the magnitude or variance of Kdemeth between treatments, suggesting that demethylation was robust to soil chemical conditions influenced by the plant, perhaps because of a wider taxonomic diversity of demethylators. Our results suggest that methylation and demethylation processes could both be leveraged to alter MeHg concentrations in rice paddy soil.

Parental beliefs about the nature of ADHD behaviours and their relationship to referral intentions in preschool children.

BACKGROUND: Parental beliefs about child problem behaviour have emerged as closely related to referral intentions to mental health services. METHODS: This study compared beliefs of severity, impact and advice seeking for attention deficit/hyperactivity disorder (ADHD) behaviours of parents whose preschool children present ADHD behaviours with those of parents whose children do not display such behaviours. Both parents of 295 preschoolers, aged 4-6 years, enrolled in kindergartens in Athens, filled in: (i) a questionnaire composed by a vignette describing a hypothetical 5-year-old child presenting ADHD symptoms followed by rating scales assessing dimensions of severity, impact and referral intention, and (ii) the 'Strengths and Difficulties Questionnaire' for screening ADHD behaviours in their own child. RESULTS: Results showed that almost half of the parents who reported ADHD behaviours in their own child replied that they had never met a child exhibiting such behaviours. These parents also perceived such behaviours as being less severe and with less negative family impact than parents who did not report such behaviours in their own child. CONCLUSIONS: Parents whose preschool child displays ADHD behaviours tend to perceive them as normal developmental patterns and may suspend the referral of the child. Implications of these findings for early identification of ADHD are discussed.

Trainee nursery teachers' perceptions of disruptive behaviour disorders; the effect of sex of child on judgements of typicality and severity.

BACKGROUND: Adults' perceptions of children with disruptive behaviour disorders (DBDs), which usually interfere with socialization and referral of children to mental health services, might differ according to the child's sex. Given the importance of (a) the interactions between these children and their educators, and (b) early identification and referral, the impact of the child's sex on adults' perceptions is an important factor to consider. AIM: To examine the role of gender-related expectations in the identification and referral of childhood DBDs by trainee nursery teachers. SAMPLE: One hundred and fifty-eight female trainee nursery teachers (mean age = 20 years) at the Department of Early Childhood Education in Athens. METHOD: Trainee nursery teachers' perceptions of male and female children with DBDs were explored using a Greek version of the Parental Account of the Causes of Childhood Problems Questionnaire. Eighty-one participants answered questions about a set of disruptive behaviours ascribed to a boy and 77 about the same behaviour ascribed to a girl. RESULTS: DBDs ascribed to girls were considered to be no more severe or of greater concern than those ascribed to boys. Judgements of severity were related to concern in the same way for boys and girls. However, DBDs were regarded as less typical for girls than boys. CONCLUSIONS: The child's sex affected trainee teachers' judgements of typicality, but not severity, of children's behaviour problems. The implications of this finding for socialization practices and referral attitudes are discussed.