Adsorption and chlorination of dibenzo-p-dioxin and 1-chlorodibenzo-p-dioxin on fly ash from municipal incinerators

Adsorption and chlorination reactions for dibenzo-p-dioxin (DD) and 1-chlorodibenzo-p-dioxin (1-MCDD) on fly ash were characterized quantitatively using laboratory-based simulation of stack emissions with air and HCl-air atmospheres. Influences of contact time and temperature were studied and results showed behavior of DD and 1-MCDD consistent with that for 1,2,3,4-tetrachlorodibenzo-p-dioxin. Di-, tri-, and tetra-chlorinated dioxins were major compounds produced from heterogenous phase reactions of DD and 1-MCDD with HCl in air. Total conversion through reactions alone were as high as 81% and 58% respectively.     

A theory on the mechanisms regulating the bioavailability of mercury in natural waters

A number of quantifiable properties of natural waters have been used by various scientists to 'explain' the Hg content in fish (e.g. pH, level of bioproduction, humosity, conductivity, calcium content, oxygen conditions, zinc and selenium content). This work presents a theory aimed at providing an explanation of the chemical mechanisms behind many established statistical relationships. The theory focuses on some equilibrium reactions and the causal relationships behind these reactions. The basic concept of the theory is that the activity of Hg(2+) in natural waters is essentially regulated by the activity of S(2-), which, in turn, is strongly affected by pH and redox conditions. Due to protonisation reactions, the S(2-) activity is very low at natural pH levels. The equilibrium between Hg(2+) and HgS(s) is given by the solubility constant Ks = 10(-52). This is an extremely low constant, which indicates that, in the presence of sulphide, essentially all Hg will appear as HgS(s). The Hg(2+) activity, and the Hg content in fish, can be increased if the S(2-) activity is decreased by lowering the pH and/or increasing the redox potential. Besides sulphide there are two other elements with a similar relationship towards Hg; namely, Se and Te (Ks = 10(-58) and Ks = 10(-70), respectively). The Hg(2+) concentration in natural waters varies quite widely, but is often about 5 ng litre(-1). This is a high concentration in these contexts. Such as high concentration can prevail only if the S(2-) (and/or the Se(2-)) activity is very small. In waters where the S(2-) and/or the Se(2-)) activity is high, e.g. from sulphide rocks in the drainage area, or if S(2-) and/or Se(2-) are added to the water, the Hg(2+) activity, and the Hg content in fish, will be effectively reduced.     

Carcinogenic and co-carcinogenic potential of 2,3,7,8-tetrachlorodibenzo-p-dioxin in a host-mediated in vivo/in vitro assay

In an in vivo/in vitro assay system (Massa et al., 1990) we have detected the carcinogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The carcinogenic potential measured in this system is concentration-dependent. Experiments with other carcinogenic compounds have revealed that TCDD at low doses can act as co-carcinogen. At higher concentrations TCDD induces TNF-α production.     

Soil contamination at abandoned sawmill areas

Contamination of soil by technical chlorophenol formulation at wood preserving sites was studied. The examined soils contained 50 to 1000 mg of polychlorinated phenols (CPs), 1 to 50 mg of polychlorinated phenoxyphenols (“pre-dioxins”, PCPPs) and 0.1 to 5 mg of polychlorinated dibenzofurans (PCDFs) per kg of dry soil. CPs were found to be mobile, leaching deep into the soil, while PCPPs and PCDFs accumulated in the top soil. All three classes of contaminants were stable in soil.     

High average daily intake of PCDD/Fs and serum levels in residents living near a deserted factory producing pentachlorophenol (PCP) in Taiwan: influence of contaminated fish consumption

An abandoned pentachlorophenol plant and nearby area in southern Taiwan was heavily contaminated by dioxins, impurities formed in the PCP production process. The investigation showed that the average serum PCDD/Fs of residents living nearby area (62.5 pg WHO-TEQ/g lipid) was higher than those living in the non-polluted area (22.5 and 18.2 pg WHO-TEQ/g lipid) (P<0.05). In biota samples, average PCDD/F of milkfish in sea reservoir (28.3 pg WHO-TEQ/g) was higher than those in the nearby fish farm (0.15 pg WHO-TEQ/g), and Tilapia and shrimp showed the similar trend. The average daily PCDD/Fs intake of 38% participants was higher than 4 pg WHO-TEQ/kg/day suggested by the world health organization. Serum PCDD/F was positively associated with average daily intake (ADI) after adjustment for age, sex, BMI, and smoking status. In addition, a prospective cohort study is suggested to determine the long-term health effects on the people living near factory.     

Levels of trace elements in green turtle eggs collected from Hong Kong: Evidence of risks due to selenium and nickel

Concentrations of 22 trace elements were determined in green turtle (Chelonia mydas) eggs collected from Hong Kong. Concentrations of selenium, lead and nickel in these eggs were generally higher than those reported in other studies. The predicted no effect concentrations (PNEC; ng/g wet weight) of Pb (1000), Se (340 and 6000 for the worst-case and best-case scenarios, respectively) and Ni (17) in the green turtle eggs were estimated. Hazard quotients (HQs) estimate that Se (HQs: 0.2-24.5) and Ni (HQs: 4.0-26.4) may pose some risks to the turtles. Our study also found that concentrations of Ag, Se, Zn, Hg and Pb in the shell of the turtle eggs were significantly correlated with levels in the whole egg contents (yolk+albumen). Once the precise relationships of specific elements are established, egg-shell concentrations may be used as a non-lethal, non-invasive, surrogate for predicting whole egg burden of certain contaminants in marine turtles.     

3,3′,4,4′-Tetrachlorobiphenyl in human fat and milk samples

Samples of adipose tissue from 7 male persons and 10 samples of human milk were analyzed for 3,3′,4,4′-tetrachlorobiphenyl by HRGC-HRMS. The levels found are in the lower ppt-range on a fat weight basis     

Effects of ozone and soil water deficit on roots and shoots of field-grown soybeans

Water-stressed and well-watered soybean (Glycine max cvs. Williams and Corsoy) plants were exposed to increasing seasonal doses of ozone (O(3)) using open-top field chambers and ambient air plots. Chamber O(3) treatments included charcoal filtered (CF) air, non-filtered (NF) air, NF + 0.03, NF + 0.06 and NF + 0.09 microl litre(-1) O(3). Soil water potentials measured at 25 and 45 cm averaged -0.40 MPa and -0.05 MPa, respectively, for the plots in the water-stressed and well-watered series. Total root length/core, root length densities, and biomasses (dry weights) were determined. With Williams, a very popular cultivar in recent years, total root length for all O(3) treatments averaged 58% more under water-stress conditions than in well-watered plots, but the range was from 136% to 11% more for NF air and NF + 0.09 microl litre(-1) O(3), respectively. Increasing the O(3) exposure dose did not affect root lengths or weights in the well-watered series. With Corsoy, water stress did not significantly increase root development. In both soil moisture regimes, with both cultivars, there was a linear decrease in seed yield and top dry weight as the O(3) exposure dose increased.