Age dependence of potentially toxic elements (Sb,Cd, Pb,Ag) in human liver tissue from paediatric subjects

Toxic elements are present at low concentrations in the environment. This work was undertaken to investigate the age dependence of the liver content of selected elements in paediatric populations, as an index of internal exposure. Liver samples were collected at autopsy from 157 subjects, aged < 1 day to 6 years, as part of investigations on a possible role of Sb compounds in sudden infant death syndrome (SIDS). In addition to Sb, the concentrations of Ag, Cd and Pb were also determined by inductively coupled plasma mass spectrometry on the remaining digest. Comparison of 95% confidence intervals of the median concentrations of the four elements suggested that there were no differences between the two categories of cause of death, SIDS or those who had died of an identified disease. Cadmium, lead and antimony median concentrations were lower than corresponding values observed in adult populations. Silver concentrations were significantly higher at birth and decreased with age. Cadmium levels were almost negligible in neonates and infants, but increased in older children. The finding of non-negligible concentrations of both Ag and Pb in neonatal liver provides further direct evidence that these elements cross the human placental barrier. The reported data, by far the largest collection observed in subjects less than 1 year old, are the result of exposure, during pregnancy and in early childhood, to present levels of these elements in the environment. They can serve as a reference to compare post-mortem values from individuals or groups of subjects in this age range when an exposure risk is suspected and to highlight trends in human exposure.     

The use of sensor arrays for environmental monitoring: interests and limitations

Continuous, in situ monitoring of air, water and land quality is fundamental to most environmental applications. Low cost and non-invasive chemical sensor arrays provide a suitable technique for in situ monitoring. Their ability and performance under realistic conditions is discussed in this paper. Published studies report promising results despite a number of limitations that are associated with both the technology itself and its application in ever changing ambient conditions. Early investigations include the analysis of single substances as well as odour and wastewater organic load monitoring. Reported applications typically highlight the sensitivity of the currently available sensors to changes in temperature, humidity and flow rate. Two types of approaches are recommended to deal with these effects: either working under fixed experimental conditions or measuring the external parameters to numerically compensate for their change. The main challenge associated with the use of non-specific sensor arrays lies in establishing a relationship between the measured multivariate signals and the standards metrics that are traditionally used for quality assessment of gas mixtures. For instance, odour monitoring requires calibration against olfactometric measurements while investigations of wastewater samples still need to be correlated with organic pollution parameters such as BOD, COD or TOC. On the other hand, results obtained in the field have demonstrated how sensor arrays can be readily used as simple alarm devices or as early warning systems based on a general air/water quality index.     

IMPROVING AQUATIC HABITAT CONDITIONS OVER TIME WHILE PRODUCING WOOD PRODUCTS: AN EXAMINATION OF OPTIONS1

ABSTRACT: A land management activity scheduling model that can perform a multi-period, simultaneous evaluation of aquatic habitat quality and commodity production goals was used to identify alternatives which would allow the improvement of aquatic habitat conditions over time, while producing wood products. The scheduling model has the ability to use stream sediment index levels, stream temperature index levels, and equivalent clearcut acres (ECA) levels as primary goals. A secondary goal imbedded in the model is the achievement of an even-flow of timber harvest volume, and a tertiary goal is the achievement of maximum efficiency (maximum net present value). The scheduling model utilizes a heuristic programming technique (Tabu search) to guide the selection of timber harvests and road standards. A 14,643 acre case study watershed in eastern Oregon is used to illustrate several policy scenarios. Activities considered include: clearcutting and partial cutting; cable, skyline, ground-based, and helicopter logging; road obliteration; requiring lower truck tire pressures on forest roads; and tree planting in riparian areas. The scheduling model produced land management plans which were spatially and temporally feasible over ten ten-year time periods. Stream temperature was shown to be dramatically reduced if tree planting is performed in all riparian areas, regardless of whether harvesting activities occurred, and including meadows and forested areas where shade density is low. Timber harvest volume levels decreased 31 to 43 percent, and net present value levels decreased 36 to 46 percent, from an unconstrained case, when any of the following occurred: ECA was constrained to 15 percent, sediment index levels were required to decrease by 1 percent per decade, or temperature levels were constrained to “no harvest” levels. The use of a heuristic programming technique is a departure from traditional techniques that are commonly used in management plan development. Yet the heuristic technique allows the inclusion of complex management goals, many of which may be prohibited when using more traditional mathematical programming techniques. In addition, decision variables which require spatial information, requiring them to take on integer or non-linear representations, can be accounted for without realizing the limitations of the traditional techniques.     

Simulating forest structure, timber production, and socioeconomic effects in a multi-owner province.

Protecting biodiversity has become a major goal in managing coastal forests in the Pacific Northwest--an area in which human activities have had a significant influence on landscape change. A complex pattern of public and private forest ownership, combined with new regulations for each owner group, raises questions about how well and how efficiently these policies achieve their biodiversity goals. To develop a deeper understanding of the aggregate effect of forest policies, we simulated forest structures, timber production, and socioeconomic conditions over time for the mixture of private and public lands in the 2.3-million-ha Coast Range Physiographic Province of Oregon. To make these projections, we recognized both vegetative complexity at the stand level and spatial complexity at the landscape level. We focused on the two major factors influencing landscape change in the forests of the Coast Range: (1) land use, especially development for houses and cities, and (2) forest management, especially clearcutting. Our simulations of current policy suggest major changes in land use on the margins of the Coast Range, a divergence in forest structure among the different owners, an increase in old-growth forests, and a continuing loss of the structural elements associated with diverse young forests. Our simulations also suggest that current harvest levels can be approximately maintained, with the harvest coming almost entirely from private lands. A policy alternative that retained live trees for wildlife would increase remnant structures but at a cost to landowners (5-7% reduction in timber production). Another alternative that precluded thinning of plantations on federal land would significantly reduce the area of very large diameter (>75 cm dbh) conifer forests 100 years into the future     

Toxicity of fipronil and its enantiomers to marine and freshwater non-targets

Fipronil is a phenylpyrazole insecticide used in agricultural and domestic settings for controlling various insect pests in crops, lawns, and residential structures. Fipronil is chiral; however, it is released into the environment as a racemic mixture of two enantiomers. In this study, the acute toxicity of the (S,+) and (R,-) enantiomers and the racemic mixture of fipronil were assessed using Simulium vittatum IS-7 (black fly), Xenopus laevis (African clawed frog), Procambarus clarkii (crayfish), Palaemonetes pugio (grass shrimp), Mercenaria mercenaria (hardshell clam), and Dunaliella tertiolecta (phytoplankton). Results showed that S. vittatum IS-7 was the most sensitive freshwater species to the racemic mixture of fipronil (LC50 = 0.65 microg/L) while P. pugio was the most sensitive marine species (LC50 = 0.32 microg/L). Procambarus clarkii were significantly more sensitive to the (S,+) enantiomer while larval P. pugio were significantly more sensitive to the (R,-) enantiomer. Enantioselective toxicity was not observed in the other organisms tested. Increased mortality and minimal recovery was observed in all species tested for recovery from fipronil exposure. These results indicate that the most toxic isomer of fipronil is organism-specific and that enantioselective toxicity may be more common in crustaceans than in other aquatic organisms.     

What difference might sewage treatment performance make to endocrine disruption in rivers?

An assessment of the steroid estrogen removing performance of 23 different sewage treatment plants (STPs) was performed. The assessment relied on a model to estimate influent concentrations, and completed questionnaires on the STP treatment details from the relevant water companies. This information was compared with observed effluent 17beta-estradiol (E2) and estrone (E1) concentrations. The 10 biological filter plants (BFP) in the study performed poorly with only 30% (SD 31) removal on average for E1. This reduced E1 removal performance of the BFPs compared to all the other STP types in the survey was statistically significant (p<0.001). Scenarios of all the STPs as activated sludge types, and one as all BFP types were modelled using the GREAT-ER model set up for the Aire/Calder catchment in the UK. This difference was shown to have an important effect on predicted river E1 concentrations and consequent risk classifications.     

GC/MS analysis of polynuclear aromatic hydrocarbons in sediment samples from the Niger Delta region

Thirteen sediment samples from different locations in the Niger Delta region of Nigeria were analyzed for the presence of 16 polynuclear aromatic hydrocarbons (PAHs) via gas chromatography/mass spectrometry. The specific target compounds for this study included naphthalene, acenaphthylene, acenaphthene, flourene, phenanthrene, anthracene, flouranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]flouranthene, benzo[a]pyrene, benzo[ghi]perylene, dibenz[a,h]anthracene, and indeno[1,2,3-cd]pyrene. Four isotopically labeled polynuclear aromatic hydrocarbons (acanaphthene-d10, phenanthrene-d10, chrysene-d12 and perylene-d12) were used for internal standardization. All 16 PAHs were found in most of the thirteen samples with concentration ranging from 0.1 microg/kg to 28 microg/kg. It was also found that the 5 and 6-ring PAHs were present in higher concentrations than all the other compounds, indicating their high resistance to microbial degradation.     

The role of soil organic matter in maintaining the productivity and yield stability of cereals in China

The role of soil organic matter (SOM) in agricultural systems has been widely studied in conjunction with the potential for greenhouse gas mitigation. However, the link between SOM accumulation in croplands, crop productivity and yield stability has not yet been clearly established. In this paper, we collected data on provincial yearly crop productivity (yields, total cropland area) during 1949–1998 and the average SOM contents in croplands sampled and determined from the National Soil Survey in 1979–1982 of mainland China. The cereal productivity was assessed both with an overall mean of 1949–1998 and with the mean values for different time periods within this overall time, respectively. The yield variability within a single stabilizing stage, and between the fluctuating years, was calculated as a negative measure of yield stability. The correlation between SOM and cereal productivity was very significant for most provinces, but the relationship has become less significant as we approach the present. Moreover, the average yield variability was very significantly and negatively correlated with the cropland SOM level. The findings support our previous hypothesis from case studies, that C sequestration in China's croplands may provide win–win benefits, by enhancing crop productivity and stabilizing yield. This offers a sound basis as a greenhouse gas mitigation strategy by promoting C sequestration in croplands, and enhancing food security in China's agriculture.     

Soil C storage as affected by tillage and straw management: An assessment using field measurements and model predictions

Soil tillage and straw management are both known to affect soil organic matter dynamics. However, it is still unclear whether, or how, these two practices interact to affect soil C storage, and data from long term studies are scarce. Soil C models may help to overcome some of these problems. Here we compare direct measurements of soil C contents from a 9 year old tillage experiment to predictions made by RothC and a cohort model. Soil samples were collected from plots in an Irish winter wheat field that were exposed to either conventional (CT) or shallow non-inversion tillage (RT). Crop residue was removed from half of the RT and CT plots after harvest, allowing us to test for interactive effects between tillage practices and straw management. Within the 0–30 cm layer, soil C contents were significantly increased both by straw retention and by RT. Tillage and straw management did not interact to determine the total amount of soil C in this layer. The highest average soil C contents (68.9 ± 2.8 Mg C ha^?1) were found for the combination of RT with straw incorporation, whereas the lowest average soil C contents (57.3 ± 2.3 Mg C ha^?1) were found for CT with straw removal. We found no significant treatment effects on soil C contents at lower depths. Both models suggest that at our site, RT stimulates soil C storage largely by decreasing the decomposition of old soil C. Extrapolating our findings to the rest of Ireland, we estimate that RT will lead to C mitigation ranging from 0.18 to 1.0 Mg C ha^?1 y^?1 relative to CT, with the mitigation rate depending on the initial SOC level. However, on-farm assessments are still needed to determine whether RT management practices can be adopted under Irish conditions without detrimental effects on crop yield.