The distribution of metals in the forest floor of aged conifer stands at a plantation in Northern England

The distribution of the elements Cd, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn has been examined in the horizons of soils under aged Sitka spruce (Picea sitchensis (Bong.) Carr.) stands at a plantation in Northern England. The stands are under first-generation cultivation and are up to 33 years old. Cadmium, Mn, Pb and Zn concentrations were consistently higher in the organic layers than in the underlying mineral soil. This contrasted with the situation for Sr and V. Cadmium, Pb and Zn all showed an increase in concentration in the L + F horizons with stand age and a corresponding increase in the difference between L + F horizon concentrations. Soil pH declined with increasing stand age. Cadmium, Cr, Pb and Zn were all present at higher concentrations in the F horizon than in any other, while Cu and Ni were relatively constant through all the horizons studied. For all nine elements, the H horizon was the largest store of the three organic layers. Calculated rates of accumulation of Cd, Pb and Zn in the L + F horizons gave good agreement with estimated regional atmospheric deposition rates. In comparison to atmospheric deposition, biological mobilisation and deposition of Cd, Pb and Zn make a relatively minor contribution to the surface soil metal burden. Cadmium appeared to be the most readily leached of these three metals from the forest floor, although some transfer of atmospherically-derived Pb to the H+ soil horizons was indicated.     

Status of the Riparian Ecosystem in the Upper San Pedro River, Arizona: Application of an Assessment Model

A portion of Arizona’s San Pedro River is managed as a National Riparian Conservation Area but is potentially affected by ground-water withdrawals beyond the conservation area borders. We applied an assessment model to the Conservation Area as a basis for monitoring long-term changes in riparian ecosystem condition resulting from changes in river water availability, and collected multi-year data on a subset of the most sensitive bioindicators. The assessment model is based on nine vegetation bioindicators that are sensitive to changes in surface water or ground water. Site index scores allow for placement into one of three condition classes, each reflecting particular ranges for site hydrology and vegetation structure. We collected the bioindicator data at 26 sites distributed among 14 reaches that had similar stream flow hydrology (spatial flow intermittency) and geomorphology (channel sinuosity, flood-plain width). Overall, 39% of the riparian corridor fell within condition class 3 (the wettest condition), 55% in condition class 2, and 6% in the driest condition class. Condition class 3 reaches have high cover of herbaceous wetland plants (e.g., Juncus and Schoenoplectus spp.) along the perennial stream channel and dense, multi-aged Populus-Salix woodlands in the flood plain, sustained by shallow ground water in the stream alluvium. In condition class 2, intermittent stream flows result in low cover of streamside wetland herbs, but Populus-Salix remain abundant in the flood plain. Perennial wetland plants are absent from condition class 1, reflecting highly intermittent stream flows; the flood plain is vegetated by Tamarixa small tree that tolerates the deep and fluctuating ground water levels that typify this reach type. Abundance of herbaceous wetland plants and growth rate of Salix gooddingii varied between years with different stream flow rates, indicating utility of these measures for tracking short-term responses to hydrologic change. Repeat measurement of all bioindicators will indicate long-term trends in hydro-vegetational condition.     

Long-term tillage effects on atrazine and fluometuron sorption in Coastal Plain soils

Conservation tillage (CnT) management practices are known to increase levels of soil organic matter (SOM) in southeastern Coastal Plain soils. Plant residues in CnT systems accumulate at the surface and, with time, will form a layer enriched in SOM. The authors hypothesize that herbicide sorption will be highest in this SOM-enriched zone of CnT systems when compared to sorption at a similar depth in conventional tillage (CT) systems. The objective was to characterize the impact of two different tillage systems, CnT and CT, on sorption of atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] and fluometuron [N,N-dimethyl-N′-3-(trifluoromethyl)phenyl urea] in plots of Norfolk loamy sand (fine-loamy, siliceous thermic Typic Kandiudult). The plots have been under CnT and CT management for 18 yrs. Bulk (0–15 cm) and five equal incremental soil samples to a 15 cm depth were collected from 10 CnT and 10 CT plots, and the atrazine (ATR) and fluometuron (FLMT) sorption coefficients (K_d) were measured using batch equilibration. Significantly higher herbicide K_d values occurred in the CnT 0–3 cm samples, indicating that the highest amount of herbicide sorption occurred in the top few cm of soil. This corresponded to the stratified soil organic carbon (SOC) contents in topsoil of the CnT plots. In addition, analyses of covariance using SOC as the covariant to test for tillage effects indicated complex interactions among SOC, tillage, and depth. Those results confirm that tillage and soil depth will affect SOC contents of a Norfolk loamy sand, which correspondly will influence the magnitude of ATR and FLMT sorption.     

Creatine kinase estimation in pure fetal blood samples for the prenatal diagnosis of duchenne muscular dystrophy

This paper compares the results of a survey of plasma creatine kinase (CK) activity measured in fetuses at-risk for Duchenne muscular dystrophy (DMD) with a reliable control series. Only pure fetal blood samples obtained by fetoscopy at between 17–24 weeks gestational age were used. Of the at-risk group 19 male pregnancies, mostly at low risk for DMD, proceeded to term with a normal outcome; there was no significant difference between their fetal plasma CK activities and the control group. Another 21 male pregnancies were terminated. This group included the highest risk mothers and hence was expected to contain a significant proportion of affected fetuses. The fetal plasma CK activity range was overlapping but significantly higher than the control group. No grossly elevated CK value was obtained. We conclude that, on average, DMD fetuses at this gestational age have higher plasma CK activity than controls. The problems of applying this finding to the prenatal diagnosis of DMD are discussed.     

Biochemical responses during starvation and subsequent recovery in postlarval Pacific white shrimp,Penaeus vannamei

Postlarval shrimp, Penaeus vannamei Boone, 1931, were held individually in cages and exposed to two feeding regimes. One group was starved for 12 d and then fed during the following 12 d. A second group was fed throughout the 24 d study. Four individuals were sampled from each of the two groups on Days 0, 1, 2, 4, 8, 12, 13, 14, 16, 20, and 24. Molting and growth among the starved-fed postlarvae stopped after 2 d starvation, while fed postlarvae increased significantly in size throughout the 24 d study. Among the starved-fed postlarvae, water content increased rapidly in response to starvation. DNA and sterol concentrations increased significantly during starvation due to selective catabolism of cellular components. After 12 d, RNA concentration was not significantly different between the fed and starved-fed postlarvae, but became significantly higher in the starved-fed postlarvae 48 h after feeding resumed. Triacylglycerol reserves were severely depleted during the first day of starvation, while protein concentrations began to decrease after the second day of starvation. RNA, protein, and the polyamines spermidine and spermine, when expressed as a ratio to DNA, decreased in response to starvation. Concentrations of all measured parameters in the starved-fed postlarvae returned to levels similar to those in the fed group 8 to 12 d after feeding resumed. Results of this study suggest that triacylglycerol provides energy during short periods of starvation, while protein is utilized during prolonged starvation. The ratios of RNA:DNA, protein:DNA, spermidine:DNA, spermine:DNA, two unidentified amine compounds, and percent water content are all useful indicators of prolonged nutritional stress in postlarval P. vannamei.     

Reactive oxygen species responsible for the enhanced desorption of dodecane in modified Fenton's systems.

The enhanced treatment of sorbed contaminants has been documented in modified Fenton's reactions; contaminants are desorbed and degraded more rapidly than they desorb by fill-and-draw or gas-purge desorption. The reactive species responsible for this process was investigated using dodecane as a model sorbent. Hydroxyl radical, hydroperoxide anion, and superoxide radical anion were generated separately to evaluate their roles in enhanced dodecane desorption. Dodecane desorption from silica sand over 180 minutes was negligible in gas-purge systems and in the hydroxyl radical and hydroperoxide anion systems. In contrast, enhanced desorption of dodecane occurred in superoxide systems, with >80% desorption over 180 minutes. Scavenging of superoxide eliminated the enhanced desorption of dodecane in both superoxide and modified Fenton's systems, confirming that superoxide is the desorbing agent in modified Fenton's reactions. Conditions that promote superoxide generation in Fenton's reactions may enhance their effectiveness for in situ subsurface remediation of sorbed hydrophobic contaminants.     

The evolution of female social relationships in nonhuman primates

Considerable interspecific variation in female social relationships occurs in gregarious primates, particularly with regard to agonism and cooperation between females and to the quality of female relationships with males. This variation exists alongside variation in female philopatry and dispersal. Socioecological theories have tried to explain variation in female-female social relationships from an evolutionary perspective focused on ecological factors, notably predation and food distribution. According to the current “ecological model”, predation risk forces females of most diurnal primate species to live in groups; the strength of the contest component of competition for resources within and between groups then largely determines social relationships between females. Social relationships among gregarious females are here characterized as Dispersal-Egalitarian, Resident-Nepotistic, Resident-Nepotistic-Tolerant, or Resident-Egalitarian. This ecological model has successfully explained differences in the occurrence of formal submission signals, decided dominance relationships, coalitions and female philopatry. Group size and female rank generally affect female reproduction success as the model predicts, and studies of closely related species in different ecological circumstances underscore the importance of the model. Some cases, however, can only be explained when we extend the model to incorporate the effects of infanticide risk and habitat saturation. We review evidence in support of the ecological model and test the power of alternative models that invoke between-group competition, forced female philopatry, demographic female recruitment, male interventions into female aggression, and male harassment. Not one of these models can replace the ecological model, which already encompasses the between-group competition. Currently the best model, which explains several phenomena that the ecological model does not, is a “socioecological model” based on the combined importance of ecological factors, habitat saturation and infanticide avoidance. We note some points of similarity and divergence with other mammalian taxa; these remain to be explored in detail. Received: 30 September 1996 / Accepted after revision: 20 July 1997     

False elevation of amniotic fluid enzymes of relevance for prenatal diagnosis: Creatine kinase measurement in relation to duchenne muscular dystrophy

The creatine kinase activity of amniotic fluid was measured in samples collected at fetoscopy. In our first study, the control sample range was 0-25 IU/1, although four samples had activities of 35–85 IU/1. Elevated values did not correlate with the activities in the fetal or maternal circulations. Electrophoresis revealed the presence of the BB isozyme of creatine kinase rather than just the MM form as expected. This suggested that the source of the elevated enzyme activity was from the myometrium, damaged by insertion of the trocar and cannula. In a further series the first 2 ml of amniotic fluid withdrawn yielded a much higher creatine kinase activity than a second aliquot. A control series of such second samples (first 2 ml discarded) gave an activity range of 0–7 IU/1 with no spuriously high values. This compares favourably with a series from single samplings taken by amniocentesis. Normal creatine kinase activities were found in the amniotic fluids from 20 pregnancies at risk for Duchenne muscular dystrophy. We conclude that for accurate measurement of amniotic fluid enzyme activity the first portion withdrawn should be discarded. Amniotic fluid creatine kinase activity is of no value for the prenatal diagnosis of Duchenne muscular dystrophy.     

Water quality parameters controlling the photodegradation of two herbicides in surface waters of the Columbia Basin,Washington

The water quality parameters nitrate-nitrogen, dissolved organic carbon, and suspended solids were correlated with photodegradation rates of the herbicides atrazine and 2,4-D in samples collected from four sites in the Columbia River Basin, Washington, USA. Surface water samples were collected in May, July, and October 2010 and analyzed for the water quality parameters. Photolysis rates for the two herbicides in the surface water samples were then evaluated under a xenon arc lamp. Photolysis rates of atrazine and 2,4-D were similar with rate constants averaging 0.025 h⁻¹ for atrazine and 0.039 h⁻¹ for 2,4-D. Based on multiple regression analysis, nitrate-nitrogen was the primary predictor of photolysis for both atrazine and 2,4-D, with dissolved organic carbon also a predictor for some sites. However, at sites where suspended solids concentrations were elevated, photolysis rates of the two herbicides were controlled by the suspended solids concentration. The results of this research provide a basis for evaluating and predicting herbicide photolysis rates in shallow surface waters.