Community mercury levels in the vicinity of peri-urban waste disposal sites and fossil fuel burning operations

INTRODUCTION: A study was conducted as a result of concern about mercury absorption amongst residents of a peri-urban area in Cape Town, South Africa, in close proximity to waste disposal sites and an industrial area. STUDY METHODS: The study compared urine mercury concentrations in a random sample of adult residents and children in both the formal and informal housing settlements of the "exposure" area (n = 90) and a control area (n = 90). A short questionnaire elicited demographic, lifestyle and medical details and possible occupational, household and environmental mercury exposures. RESULTS: The two samples were comparable with respect to background and potential confounding variables. The prevalence of urinary mercury levels>or=the WHO reference range in the exposure area was also higher than that in the control area (13% vs. 0%). The median urinary mercury concentrations in both study areas were below the World Health Organisation (WHO) reference level of 5.0 microg/g creatinine. The median level in the exposure area was slightly, but statistically significantly, higher than in the control area (1.1 vs. 0.25 microg/g creatinine), and the excess persisted after controlling for known possible mercury exposures. CONCLUSIONS: This is to our knowledge the first study of community inorganic mercury absorption in a developing country setting, and where airborne mercury was the exposure of concern. It was concluded that the health risk associated with the urinary mercury levels of residents in the exposure area was very low. However, low level environmental exposure in the area of concern could not be excluded.     

Global invasive potential of 10 parasitic witchweeds and related Orobanchaceae

The plant family Orobanchaceae includes many parasitic weeds that are also impressive invaders and aggressive crop pests with several specialized features (e.g. microscopic seeds, parasitic habits). Although they have provoked several large-scale eradication and control efforts, no global evaluation of their invasive potential is as yet available. We use tools from ecological niche modeling in combination with occurrence records from herbarium specimens to evaluate the global invasive potential of each of 10 species in this assemblage, representing several of the worst global invaders. The invasive potential of these species is considerable, with all tropical and subtropical countries, and most temperate countries, vulnerable to invasions by one or more of them.     

An analytical model for the assessment of pesticide exposure levels in soils and groundwater

The movement and degradation of pesticide residues in soils and groundwater are complex processes affected by soil physical, (bio)chemical, and hydrogeological properties, climatic conditions, and agricultural practices. This work presents a physically-based analytical model suitable for long-term predictions of pesticide concentrations in groundwater. The primary interest is to investigate the impact of soil environment, related physical and (bio)chemical processes, especially, volatilization, crop uptake, and agricultural practices on long-term vulnerability of groundwater to contamination by pesticides. The soil is separated into root and intermediate vadose zones, each with uniform properties. Transport in each soil zone is modeled on the basis of complete mixing, by spatial averaging the related point multiphase-transport partial differential equation (i.e., linear-reservoir models). Transport in the aquifer, however, is modeled by a two-dimensional advection-dispersion transport equation, considering adsorption and first-order decay rate. Vaporization in the soil is accounted for by assuming liquid-vapor phase partitioning using Henry's law, and vapor flux (volatilization) from the soil surface is modeled by diffusion through an air boundary layer. Sorption of liquid-phase solutes by crops is described by a linear relationship which is valid for first-order (passive) crop uptake. The model is applied to five pesticides (atrazine, bromacil, chlordane, heptachlor, and lindane), and the potential for pesticide contamination of groundwater is investigated for sandy and clayey soils. Simulation results show that groundwater contamination can be substantially reduced for clayey soil environments, where bio(chemical) degradation and volatilization are most efficient as natural loss pathways for the pesticides. Also, uptake by cross can be a significant mechanism for attenuating exposure levels in ground-water especially in a sandy soil environment, and for relatively persisting pesticides. Further, simulations indicate that changing agricultural practices can have a profound effect on vulnerability of groundwater to mobile and relatively persisting pesticides.     

Procedures for outlier detection in circular time series models

It is known that the occurrence of outliers in linear or non-linear time series models may have adverse effects on the modelling and statistical inference of the data. Consequently, extensive research has been conducted on developing outlier detection procedures so that outliers may be properly managed. However, no work has been done on the problem of outliers in circular time series data. This problem is the focus of this paper. The main objective is to develop novel numerical and graphical procedures for detecting these outliers in circular time series data.A number of circular time series models have been proposed including the circular autoregressive model. We extend the iterative outlier detection procedure which has been successfully used in linear time series models to the circular autoregressive model. The proposed procedure shows a good performance when investigated via simulation for the circular autoregressive model of order one. At the same time, several statistical techniques have been used to detect the change of preferred trend in time series data using SLIME and CUSUM plots. While the methods fail to indicate directly the outliers in circular time series data, we use the ideas employed to develop three novel graphical procedures for identifying the outliers. For illustration, we apply the procedures to a particular set of wind direction data. An agreement between the results of the graphical and iterative detection procedures is observed. These procedures could be very useful in improving the modelling and inferential processes for circular time series data.     

Seasonal concentrations of lead in outdoor and indoor dust and blood of children in Riyadh,Saudi Arabia

Because detrimental effects of exposure to lead (Pb) on human health have been observed, we previously investigated concentrations of Pb in water supplies and blood of adult residents of Riyadh, Saudi Arabia. The objectives of the present study were to: (1) examine seasonal rates of deposition of Pb in dust in several areas of Riyadh city, (2) measure concentrations of Pb in both outdoor and indoor dust, (3) compare concentrations of Pb in dust in Riyadh with those reported for other cities, and (4) quantify Pb in blood of children living in Riyadh. Mean, monthly deposition of PB in outdoor dust was 4.7 × 10¹ ± 3.6 tons km^?2, with a mean Pb concentration of 2.4 × 10² ± 4.4 × 10¹ μg/g. Mean, monthly deposition of Pb in indoor dust was 2.7 ± 0.70 tons km^?2, with a mean concentration of 2.9 × 10¹ ± 1.5 × 10¹ μg Pb/g. There was a significant (P < 0.01) correlation between concentrations of Pb in outdoor and indoor dust. There was no correlation between concentrations of Pb in indoor dust and that in blood of children of Riyadh, whereas there was a weakly significant (P < 0.05) correlation between concentrations of Pb in outdoor dust and that in blood of children. The mean (±SD) concentration of Pb in blood of children in Riyadh was 5.2 ± 1.7, with a range of 1.7–1.6 × 10¹ μg/dl. Concentrations of Pb in blood of 17.8 % of children in Riyadh were greater than 10 μg/dl, which is the CDC’s level of concern.     

Effects of low doses of bisphenol A and o,p ′- DDT on reproductive function of posthatching male Japanese quail

Forty-six posthatched male Japanese quail (Coturnix japonica) were divided into five groups; Control (n = 8), Oil (n = 8), 2 mg Bisphenol A (BPA) (n = 12), 20 µg o, p′-DDT (n = 11) and Mix [BPA (2 mg) and o, p′-DDT (20 µg)/10 µL] (n = 7). Chemicals were given orally to the quail daily for about 100 days. At day 90 of the experiment, sexual behavior was studied. Moreover, one day before the quail were sacrificed, cloacal gland areas were measured. All birds were scarified at 100 days. Testicular weights as well as gonado-somatic index were recorded. Sperm concentration was analyzed by the computer-assisted sperm analysis system. The testes of each bird were subjected to histopathological examination and the diameter of 30 randomly selected seminiferous tubules was measured. Sexual maturity was significantly delayed in o, p′-DDT and Mix groups. In addition, quail that were given BPA and o, p′-DDT took a significantly longer time to perform the first sexual interaction. The diameters of seminiferous tubules were remarkably reduced in all treated groups. In conclusion, low doses of BPA, o, p′-DDT or a combination of these two agents affected reproductive functions in male Japanese quail, when administered at posthatching.     

Relative yields of monomeric and dimeric adducts induced by sulphur mustard in isolated and cellular DNA as determined by HPLC/tandem mass spectrometry

Sulphur mustard (SM) is known as an efficient vesicating agent as well as a carcinogenic chemical. This warfare agent remains a threat for both civilians and militaries. DNA alkylation is one of the critical molecular pathways at the origin of the symptoms associated with SM exposure. SM forms monoadducts with guanine and adenine as well as a biadduct between two guanine bases. The aim of the present work is to determine the relative yields of these three lesions in DNA samples after SM exposure without using radiolabeled SM as in earlier works. For this purpose, we have developed a high performance liquid chromatography/tandem mass spectrometric method to simultaneously quantify the SM monoadducts and biadduct in the same DNA sample. We observed in isolated and cellular DNA that the guanine monoadduct was the predominant lesion, while the biadduct was present in twofold lower yield. The adenine monoadduct was generated in lowest amounts. The analytical approach was extended to 2?chloroethyl ethyl sulphide, a widely used SM analog. Again, the adenine adduct was much less frequent than the guanine derivative. The developed assay will allow performing studies involving large numbers of samples.     

Concentration of some polycyclic aromatic hydrocarbons in rain,soil and ground water around Ismailia,Egypt

Residues of acenaphthylene, fluorene, anthracene, pyrene, chrysene, benzo(b)fluoranthene and benzo(k)fluoranthene were monitored in rain, soil and groundwater around Ismailia, in northeast Egypt. Residues detected in rain water in 1995 and 1996 were mainly of relatively low molecular weight. Both acenaphthylene and fluorene were detected in rain for the two consecutive years. Top soil has shown a wider spectrum and higher concentrations of (PAHs) than those detected in deep soil, rain and ground water. Only three compounds, acenaphthylene, fluorene and anthracene were detected in samples collected at 50 cm depth. While no traces of PAHs were detected at 1 m depth detectable concentrations of fluorene and anthracene were monitored in groundwater.     

Fractionation of trace metals (Mn,Zn, Cu,Pb) in Red Sea sediments,Gulf of Aden,Yemen

A sequential extraction technique was applied to estimate the chemical association of Mn, Zn, Cu and Pb in five chemical phases (exchangeable, carbonate, Fe–Mn oxides, organic matter and residual) in sediments of the Gulf of Aden, Yemen. The results indicated that a higher level of Mn was associated with the residual fraction (natural sources) than the non-residual fraction (anthropogenic sources). Zn fractionations revealed that it was associated more with Fe–Mn oxides and organic fractions than exchangeable and carbonate fractions. Most of the Cu was present in the residual form (60–72%) except for in the main port area (zone III), where it was associated with the organic phase (77% of the total Cu content, the organic matter content was 5%). Similarly, most Pb was bound in the residual fraction (56–71%) except the main port area where ～ 62% of the total Pb was bound in non-residual fractions. It was also found that the Pb concentration in the exchangeable fraction was very high compared with other metals. The risk assessment code for the metals showed a low risk for Zn and Cu, but low to medium risk for Mn. Fractionation of Pb showed medium risk at most of the regions except at the eastern area, which revealed a high risk for the aquatic environment.     

The effects of application of agricultural wastes to firing range soil on metal accumulation in Ipomoea aquatica and soil metal bioavailability

The immobilisation of heavy metals in the soil of a 25-year-old active firing range using durian (Durio zibethinus L.) tree sawdust (DTS), coconut coir (CC) and oil palm empty fruit bunch (EFB) was investigated. The immobilisation effects were evaluated in terms of metal accumulation in water spinach (Ipomoea aquatica) and soil metal bioavailability. A pot experiment was conducted by amending the firing range soil with DTS, CC and EFB at application rates of 0%, 1% and 3% (w/w), respectively. All amendments increased the biomass yield and reduced the uptake of heavy metals in the plant tissue. Zn had the highest values of Bioconcentration Factor (BCF: 0.301–0.865) and Translocation Factor (TF: 1.056–1.883). Pb was the least-accumulated and transported metal in the plant tissues, with the BCF and TF values of 0.019–0.048 and 0.038–0.116, respectively. The bioavailable fraction of heavy metals in the firing range soil decreased following the application of the three agricultural wastes studied. DTS, CC and EFB did not cause toxicity symptoms in the water spinach over the pot experiment. Therefore, DTS, CC and EFB are considered promising immobilising agents for the remediation of metal-contaminated land.