Use of 15N Natural Abundance and N Species Concentrations to Assess N-Cycling in Constructed and Natural CoastalWetlands

Natural abundance of N stable isotopes used in combination with concentrations may be useful indicators of N-cycling in wetlands. Concentrations and 15N signatures of NO −3 , NH + 4 , and sediment organic nitrogen (SON) were measured in two impacted coastal golf course retention ponds and two natural marshes. Limited NO − 3 was detected in natural site surface water or pore water, but both isotopic signature and concentrations of NO − 3 in surface water of impacted sites indicated anthropogenic inputs. In natural sites, NH + 4 concentrations were greatest in deeper pore water and least in surface water, suggesting diffusion predominates. The natural sites had greater %SON, and 15N indicated that the natural sites also had greater NH + 4 released from SON mineralization than impacted sites. In NO − 3 -limited systems, neither concentrations nor 15N natural abundance was able to provide information on N-cycling, while processes associated with NH + 4 were better elucidated by using both concentrations and 15N natural abundance

The Relationship Between Mental Retardation and Developmental Delays in Children and the Levels Of Arsenic, Mercury and Lead in Soil Samples Taken Near Their Mother\u27s Residence During Pregnancy

This study was designed to evaluate the association between lead, mercury, and arsenic in the soil near maternal residences during pregnancy and mental retardation or developmental disability (MR/DD) in children. The study was conducted using 6,048 mothers who did not move throughout their pregnancies and lived within six strips of land in South Carolina and were insured by Medicaid between January 1, 1997 and December 31, 2002. The mother child pairs were then followed until June 1, 2008, through their Medicaid reimbursement files, to identify children diagnosed with MR/DD. The soil was sampled for mercury (Hg), lead (Pb), and As based on a uniform grid, and the soil concentrations were Kriged to estimate chemical concentration at individual locations. We identified a significant relationship between MR/DD and As, and the form of the relationship was nonlinear, after controlling for other known risk factors

Are clusters of mental retardation correlated with clusters of developmental delay?

Mental retardation (MR) is a subset of developmental delay (DD), a broader classification of childhood disability. The purpose of this study was to determine if clusters of these two conditions were statistically significantly correlated. The residential addresses of 81,935 Medicaid insured pregnant women during each month of pregnancy were used to identify clusters of MR and DD in their children. Correlations between MR and DD were computed based on the sets of P-value surface from selected centroid points, where the P-value for cumulative relative risk of MR and DD was known. The correlations are quite small for all the 10 gestational months for which maternal addresses were available, but they are all statistically significant. This indicates MR and DD are correlated, but they are not linear. When MR was used as the centroid point to identify a cluster the only correlations that were statistically significant were for gestational month 5 and 6 with correlation 0.14 (P = 0.007) for both months. When the centroid points were selected based on the significance of risk of DD, the correlations between MR and DD are not statistically significant for any month. Correlation between MR and DD based on the sets of P-value surfaces from 4 MR clusters are significant in gestational month 5, 6 and 7 with correlation 0.17 (P = 0.047), 0.16 (P = 0.060) and 0.17 (P = 0.044), respectively. Our finding suggests that locations of high risk for the more severe condition, MR, also identify a spatial area where less severe cases of DD might be present, however the reverse is not the case