Correlation of cadmium distribution coefficients to soil characteristics

Cadmium (Cd) distribution between the soil solid phase and the soil solution is a key issue in assessing the environmental effect of Cd in the terrestrial environmental. Previous studies have shown that many individual minerals and other components found in soils can bind Cd, but most studies on whole soil samples have shown that pH is the main parameter controlling the distribution. To identify further the components that are important for Cd binding in soil we measured Cd distribution coefficients (Kd) at two fixed pH values and at low Cd loadings for 49 soils sampled in Denmark. The Kd values for Cd ranged from 5 to 3000 L kg(-1). The soils were described pedologically and characterized in detail (22 parameters) including determination of contents of the various minerals in the clay fraction. Correlating parameters were grouped and step-wise regression analysis revealed that the organic carbon content was a significant variable at both pH values. Cation exchange capacity (CEC) and gibbsite were important at the low pH (5.3) while iron oxides also were important at the high pH (6.7). None of the other clay minerals present in the soils (illite, smectite, kaolinite, hydroxy interlayered clay minerals [HIM], chlorite, quartz, microcline, plagioclase) were significant in explaining the Cd distribution coefficient.     

Reproduction and larval development in three scalpellid barnacles, Scalpellum scalpellum (Linnaeus 1767), Ornatoscalpellum stroemii (M. Sars 1859) and Arcoscalpellum michelottianum (Seguenza 1876), Crustacea: Cirripedia: Thoracica): implications for reproduction and dispersal in the deep sea

We studied reproduction and larval development in three species of pedunculated barnacles with different depth distribution, that is, Scalpellum scalpellum (30–200 m), Ornatoscalpellum stroemii (100–1,600 m) and Arcoscalpellum michelottianum (64–5,190 m). Morphology, position and number of males in the female/hermaphrodite, type of larval development and the number and size of eggs were recorded. All three species have a pair of pocket-like receptacles, each of which can host only a single male in O. stroemii, up to five males in S. scalpellum and up to 12 males in A. michelottianum. Eggs and larvae were smallest in S. scalpellum, intermediately sized in O. stroemii and largest in A. michelottianum. Brood size was comparable for S. scalpellum and O. stroemii, but five times higher in A. michelottianum. The ratio for body/egg size is almost similar in S. scalpellum and A. michelottianum, but much smaller in O. stroemii. Both S. scalpellum and A. michelottianum have nauplii that spend upwards of 10 days in the plankton while the larvae of O. stroemii hatch as cyprids that settle soon after release. All these reproductive data indicate that O. stroemii invests considerably more in each propagule than the other two species. We hypothesize that the observed differences in reproductive system and mode of development in the three species represent adaptations to their different habitats. S. scalpellum are mainly transported by currents in the coastal sublittoral zone. O. stroemii is presumably spread by intermediate deep currents along the shelf and shelf-slope, while A. michelottianum occurs on seamounts and is probably transported by demersal currents over wide areas of inhospitable soft-bottoms. Our observations are in accordance with the general pattern that, egg-size and propagule-size are positively correlated to bathymetric and geographic distribution, and that the continental slope environment represents a high disturbance environment, where a short larval stage is an advantage.     

45,X karyotype: May the diagnosis be suspected on ultrasonic examination in the second trimester of pregnancy?

We report three cases of Turner's syndrome with cystic hygromata, which were diagnosed by routine ultrasound scanning before amniocentesis in the second trimester of pregnancy. Maternal and amniotic level of alpha-fetoprotein were normal. Karyotyping carried out afterwards showed a 45,X karyotype. Our data indicate, that cystic hygromata in Turner's syndrome may coexist with a normal amniotic fluid AFP, thus questioning the theory of leakage from the hygroma. It remains to be investigated if all cases of Turner's syndrome present a cystic hygroma in utero.     

A distributed modelling system for simulation of monthly runoff and nitrogen sources, loads and sinks for ungauged catchments in Denmark

We validated an existing physically based 3D MIKE SHE groundwater resource model (DK-model) at 175 Danish gauging stations covering different catchment sizes in order to calculate monthly water runoff in the 50% ungauged part of Denmark. Model performance was in most cases good (61% of gauging stations had a Nash-Sutcliffe (NS) coefficient >0.60) but nevertheless showed a large seasonal and georegion specific bias. Therefore, bias correction factors had to be developed before applying the DK-model simulations of runoff in the ungauged areas. Simulated monthly runoff from ungauged areas and the measured monthly runoff from 178 gauging stations were distributed to 2663 smaller Hydrological Units (ca. 15 km(2)) and linked with a new empirical model for flow-weighted monthly total nitrogen (TN) concentrations (R(2) = 0.43; P < 0.0001) developed based on 20 years of observations (1990-2009) in 83 small catchments for calculation of monthly gross diffuse TN-loads from HU's. Nitrogen retention was calculated in streams, lakes and wetlands utilising both lake specific models and rate coefficients to calculate N retention in surface water bodies. The whole model complex was linked in the DK-QN concept for simulation of monthly TN losses from point sources and diffuse sources, TN retention and resulting loadings to Danish coastal waters. The DK-QN model was validated in 118 gauged catchments and the model simulations had for >25% of the observations of monthly discharge weighted TN concentrations a NS larger than 0.26. Catchment specific monthly TN-loadings were modelled with a higher performance as 50% of the catchments had a NS greater than 0.75. The model concept allows calculation of N retention in streams, lakes and wetlands and the average annual model calculated N retention amounted to 21% of the modelled gross riverine TN loadings. The average annual gross TN loading to surface freshwater in Denmark derived from diffuse sources amounted to 97 000 tonnes N (91% of gross TN loadings) which is 54% of the total estimated N-leaching from the root zone on the Danish land area (212 000 tonnes N) during the period 1990-2009.     

The CPCAT as a novel tool to overcome the shortcomings of NOEC/LOEC statistics in ecotoxicology: a simulation study to evaluate the statistical power

Species reproduction is an important determinant of population dynamics. As such, this is an important parameter in environmental risk assessment. The closure principle computational approach test (CPCAT) was recently proposed as a method to derive a NOEC/LOEC for reproduction count data such as the number of juvenile Daphnia. The Poisson distribution used by CPCAT can be too restrictive as a model of the data-generating process. In practice, the generalized Poisson distribution could be more appropriate, as it allows for inequality of the population mean \(\mu\) and the population variance \(\sigma ^2\). It is of fundamental interest to explore the statistical power of CPCAT and the probability of determining a regulatory relevant effect correctly. Using a simulation, we varied between Poisson distribution (\(\mu =\sigma ^2\)) and generalized Poisson distribution allowing for over-dispersion (\(\mu <\sigma ^2\)) and under-dispersion (\(\mu >\sigma ^2\)). The results indicated that the probability of detecting the LOEC/NOEC correctly was \(\ge 0.8\) provided the effect was at least 20% above or below the mean level of the control group and mean reproduction of the control was at least 50 individuals while over-dispersion was missing. Specifically, under-dispersion increased, whereas over-dispersion reduced the statistical power of the CPCAT. Using the well-known Hampel identifier, we propose a simple and straight forward method to assess whether the data-generating process of real data could be over- or under-dispersed.     

Social network analysis and valid Markov chain Monte Carlo tests of null models

Analyses of animal social networks derived from group-based associations often rely on randomisation methods developed in ecology (Manly, Ecology 76:1109–1115, 1995) and made available to the animal behaviour community through implementation of a pair-wise swapping algorithm by Bejder et al. (Anim Behav 56:719–725, 1998). We report a correctable flaw in this method and point the reader to a wider literature on the subject of null models in the ecology literature. We illustrate the importance of correcting the method using a toy network and use it to make a preliminary analysis of a network of associations among eagle rays.

Synchronous variation in water chemistry for 80 lakes in Southern Sweden

Variation in water chemistry was studied in 80 lakes in southern Sweden. The lakes had forest dominated catchments. The length of the time series was 14 years. Synchrony was calculated as Pearsons product moment correlation coefficients for all combinations of lakes, i.e. 3160 lake-pairs. The chemical variables studied were non-marine sulphate (SO₄ ^*), non-marine calcium (Ca^*), absorbance and acid neutralising capacity (ANC). Statistically significant synchrony occurred in 93% of all lake-pairs for SO₄ ^*, and between 58 and 67% for absorbance, Ca^* and ANC. In 70% of all lake-pairs, the synchrony was \s>0.71 for SO₄ ^*, which means that more than half of the variation in one lake could be explained by the variation in the other lake. For absorbance, Ca^* and ANC, about 25% of the lake-pairs had a synchrony \s>0.71. The relatively high synchrony for SO₄ ^* occurred during an overall downward trend in SO₄ ^* concentration.The degree of synchrony in our study was at a level comparable to other studies in northern America and England. However, our study included lakes in a much larger area, with distances of up to 500 km between the lakes, while earlier studies were made on small lake districts with lakes located within approximately 50 km. In contrast to these earlier studies, there was no correlation between synchrony and distance, lake characteristics or catchment characteristics. However, when a small subset of 15 lakes in the southeast of Sweden was selected, such relations were found.     

Vegetation Placement for Summer Built Surface Temperature Moderation in an Urban Microclimate

Urban vegetation can mitigate increases in summer air temperature by reducing the solar gain received by buildings. To quantify the temperature-moderating influence of city trees and vine-covered buildings, a total of 13 pairs of temperature loggers were installed on the surfaces of eight buildings in downtown Toronto, Canada, for 6 months during the summer of 2008. One logger in each pair was shaded by vegetation while the other measured built surface temperature in full sunlight. We investigated the temperature-moderating benefits of solitary mature trees, clusters of trees, and perennial vines using a linear-mixed model and a multiple regression analysis of degree hour difference. We then assessed the temperature-moderating effect of leaf area, plant size and proximity to building, and plant location relative to solar path. During a period of high solar intensity, we measured an average temperature differential of 11.7 °C, with as many as 10–12 h of sustained cooler built surface temperatures. Vegetation on the west-facing aspect of built structures provided the greatest temperature moderation, with maximum benefit (peak temperature difference) occurring late in the afternoon. Large mature trees growing within 5 m of buildings showed the greatest ability to moderate built surface temperature, with those growing in clusters delivering limited additional benefit compared with isolated trees. Perennial vines proved as effective as trees at moderating rise in built surface temperature to the south and west sides of buildings, providing an attractive alternative to shade trees where soil volume and space are limited.     

A method for quick assessment of CO2 storage capacity in closed and semi-closed saline formations

Saline aquifers of high permeability bounded by overlying/underlying seals may be surrounded laterally by low-permeability zones, possibly caused by natural heterogeneity and/or faulting. Carbon dioxide (CO₂) injection into and storage in such “closed” systems with impervious seals, or “semi-closed” systems with non-ideal (low permeability) seals, is different from that in “open” systems, from which the displaced brine can easily escape laterally. In closed or semi-closed systems, the pressure buildup caused by continuous industrial-scale CO₂ injection may have a limiting effect on CO₂ storage capacity, because geomechanical damage caused by overpressure needs to be avoided. In this research, a simple analytical method was developed for the quick assessment of the CO₂ storage capacity in such closed and semi-closed systems. This quick-assessment method is based on the fact that native brine (of an equivalent volume) displaced by the cumulative injected CO₂ occupies additional pore volume within the storage formation and the seals, provided by pore and brine compressibility in response to pressure buildup. With non-ideal seals, brine may also leak through the seals into overlying/underlying formations. The quick-assessment method calculates these brine displacement contributions in response to an estimated average pressure buildup in the storage reservoir. The CO₂ storage capacity and the transient domain-averaged pressure buildup estimated through the quick-assessment method were compared with the “true” values obtained using detailed numerical simulations of CO₂ and brine transport in a two-dimensional radial system. The good agreement indicates that the proposed method can produce reasonable approximations for storage–formation–seal systems of various geometric and hydrogeological properties.     

Occurrence and distribution of PCB metabolites in blood and their potential health effects in humans: a review

In recent years, attention has been directed to chemicals with possible endocrine-disrupting properties. Polychlorinated biphenyls (PCBs) and their metabolites belong to one group of environmental contaminants that have been shown to interact with the endocrine system in mammals, including humans. Although recent developments have been made in terms of determination of PCB metabolites in blood samples, still limited number of studies have been able to elucidate their profiles and toxicological and health effects in humans. This review aims to evaluate and compare the levels of hydroxylated PCBs (OH-PCBs) and methyl sulfone PCBs (MeSO₂-PCBs) in blood and their relationship to parent compounds and also address the potential risks and adverse health effects in humans. Levels of OH-PCBs varied between 0.0002 and 1.6 ng g^?1 w/w in human serum/plasma from the selected literature, correlating well with ∑PCBs. In contrast, ∑OH-PCB/∑PCB ratio in animals did not show a significant correlation, which might suggest that the bioaccumulation plays an even more important role in the concentration of OH-PCBs compared to PCB metabolism. Highest levels of MeSO₂-PCBs were reported in marine mammals with high selectivity retention in the liver. Health effects of PCB metabolites included carcinogenicity, reproductive impairment, and developmental neurotoxicity, being more efficiently transferred to the brain and across the placenta from mother to fetus in comparison to the parent PCBs. Based on the lack of knowledge on the occurrence and distribution of lower chlorinated OH-PCBs in humans, further studies to identify and assess the risks associated to human exposure are essential.