Cadmium concentration in tobacco (Nicotiana tabacum L.) from different countries and its relationship with other elements

Cadmium accumulation in crop plants, such as tobacco (Nicotiana tabacum L.), can lead to human exposure to this carcinogenic metal. To better define actual Cd distribution in cured or processed tobacco leaves from chief tobacco-producing regions, we analyzed 755 leaf samples of three major types (Flue-cured, Burley, and Oriental) obtained from 13 countries during 2001-2003. This survey may help identify regions with low- or high-Cd concentrations in tobacco to obtain insight into the cause of the concentration extremes and to assist in defining strategies to reduce Cd in tobacco. Cadmium concentrations in the samples ranged from 0 to 6.78 microg g(-1), as determined by ICP-MS. Significant differences were found among types and among countries, but significant interactions between type and country were found. Variations in Cd concentrations were also found in all countries. Our results suggest an important contribution of the field (e.g., bioavailable Cd in soil, other soil characteristics) to the Cd concentration in tobacco. Finally, the correlation between the concentration of Cd and that of other elements differed among the types, which could be effectively discriminated based on the concentrations of 20 elements.     

Life history of a dominant polychaete, <Emphasis Type="Italic">Polygordius jouinae</Emphasis>, in inner continental shelf sands of the Mid-Atlantic Bight,USA

The life history of the polychaete Polygordius jouinae Ramey, Fiege, and Leander 2006 was studied in the sandy sediments of the LEO-15 research area off the coast of Tuckerton, New Jersey (39°27.69′N, 74°15.81′W). Divers collected sediment cores biweekly, from February 2004 to November 2005 to examine the temporal patterns of abundance and size–frequency distributions of P. jouinae. These parameters were also examined (for the first time) for P. jouinae in samples taken in ambient sediments and in three reciprocal 3 to 5-day sediment transplant experiments that were part of a previous, unrelated study at coarse sand and muddy sand sites (∼3 km apart) at LEO-15 in the summers of 1994 and 1995. Analysis of these previous data along with the current data provided a larger set of values for P. jouinae, as well as further insight into the life history, habitat selection, and dispersal of P. jouinae (not considered in previous studies). Polygordius jouinae is gonochoristic and the population was mostly composed of sexually mature individuals in late May 2004 and 2005. The reproductive period usually occurs from May to August and individuals that spawn generally have a 1-year life span. Non-spawning individuals of P. jouinae could potentially live longer than 1 year and therefore the population may sometimes consist of individuals of two generations. Recruitment begins no later than July as recently settled individuals (≤9 mm body length), which were not present during the first week of June 1995, 2004, and 2005, first appeared in July in all 3 years. The smallest individual was 2.01 mm long and 0.07 mm wide and this provides the first estimate of size at initial recruitment. Although some worms in sediment trays likely settled as larvae, most worms were recently settled juveniles (length categories 6 and 9 mm) transported in from the surrounding sediments, presumably as a consequence of re-suspension or bed load transport. As expected, larger individuals were present later in September. Although it is unknown whether P. jouinae were transported actively or passively these data suggest that recently settled juveniles are capable of habitat selection (prefer sand over mud) and show that post-settlement transport and selection influence community structure.     

Spatial relationships and matrilineal kinship in African savanna elephant (Loxodonta africana) clans

African savanna elephants, Loxodonta africana, live in stable family groups consisting of adult females and their dependent offspring. During the dry season, clans consisting of several family groups typically share a common home range. We compared spatial relationships and mitochondrial DNA (mtDNA) haplotypes among 14 adult female elephants within 3 clans during the dry season in northern Zimbabwe. Spatial relationships were studied by radio-tracking. Home-range similarity was quantified by correlating the estimated utilization distributions of all pairs of elephants. Clans were identified by cluster analysis of the home-range similarity values. All three clans contained at least two of the five mtDNA haplotypes that were found, indicating that clan members are not necessarily matrilineally related. Within clans, home ranges of elephants with the same haplotype were not significantly more similar to each other than those of elephants with different haplotypes. Most elephants within each clan used their shared home ranges independently of each other: the distribution of distances between their positions at any given time did not differ from the distribution expected by chance. However, 8 out of the 26 within-clan pairs exhibited long-term coordination of space use by remaining within known hearing distance of each others low-frequency calls significantly more often than expected by chance. At least four of these coordinated pairs consisted of animals in different family groups. Elephants in three of the four different-family pairs whose movements were coordinated had different haplotypes. Further research is needed to determine the relationship between these coordinated movements and conventionally defined bond-group behavior.Electronic Supplementary Material Supplementary material is available in the online version of this article at .Communicated by C. Nunn     

Contributions of biofilm and suspended sludge to nitrogen transformation and nitrous oxide emission in hybrid sequencing batch system

Hybrid system combines the nature of suspended growth and attached growth has been widely applied to wastewater treatment. In this research, the contributions to N transformation and N2O emission by biofilm and suspended sludge in the hybrid sequencingbatch reactor for a simultaneous nitrification, denitrification and phosphorus removal process were investigated. For the hybrid system, nitrification occurred mostly in the suspended sludge, while the biofilm played the major role in denitrification. The interaction of the biofilm and the suspended sludge in the same reactor resulted in a better overall nitrogen removal performance with simultaneous nitrification and denitrification. However, N2O emission was the main end product of nitrogen removal for the hybrid system; while it was N2 for the biofilm. The relative low N2O emissions from the pure biofilm and the pure suspended sludge corresponded to the relatively high nitrate at the end of the aeration period compared with the hybrid system.