Although phosphate phosphorus (P) is strongly sorbed in many soils, it may be quickly transported through the soil by preferential flow. Under flood irrigation, preferential flow is especially pronounced and associated solute losses may be important. Phosphorus losses induced by flood irrigation were investigated in a lysimeter study. Detailed soil chemical analyses revealed that P was very mobile in the topsoil, but the higher P-fixing capacity of the subsoil appeared to restrict P mobility. Application of a dye tracer enabled preferential flow pathways to be identified. Soil sampling according to dye staining patterns revealed that exchangeable P was significantly greater in preferential flow areas as compared with the unstained soil matrix. This could be partly attributed to the accumulation of organic carbon and P, together with enhanced leaching of Al- and Fe-oxides in the preferential flow areas, which resulted in reduced P sorption. The irrigation water caused a rapid hydrologic response by displacement of resident water from the subsoil. Despite the occurrence of preferential flow, most of the outflowing water was resident soil water and very low in P. In these soils the occurrence of preferential flow per se is not sufficient to cause large P losses even if the topsoil is rich in P. It appears that the P was retained in lower parts of the soil profile characterized by a very high P-fixing capacity. This study demonstrates the risks associated with assessing potential P losses on the basis of P mobility in the topsoil alone. 相似文献
Metabolic transformation plays a major role in the mechanism of toxicity of organophosphorous (OP) pesticides. The modulation of their toxicity by oxonases and monooxygenases, alone or in combination, has been shown in mammals and fish. Very limited information exists for the identification of the metabolic factors relevant in the human toxicology of such chemicals. In this paper, we develop a simple algorithm, based on in vitro data, for the identification of fish species more susceptible to diazinon (D). Similar algorithms are likely to be applicable to other organophosphothionate (OPT) pesticides. We also report on preliminary studies on the OPT substrate specificity of human liver cytochromes P450 (CYPs): such information may be useful to understand the role of sulphoxidation in OPT toxicity to humans and to identify individuals with increased susceptibility to OPT toxicity. Studies of the mechanism of OPT toxicity may provide useful tools for a more detailed characterisation of these chemicals, with reference to the risk for the human population and to the impact on the fish species present in specific environments. 相似文献
Climate change has impacts on both natural and human systems. Accurate information regarding variations in precipitation and temperature is essential for identifying and understanding these potential impacts. This research applied Mann–Kendall, rescaled range analysis and wave transform methods to analyze the trends and periodic properties of global and regional surface air temperature (SAT) and precipitation (PR) over the period of 1948 to 2010. The results show that 65.34 % of the area studied exhibits significant warming trends (p?<?0.05) while only 3.18 % of the area exhibits significant cooling trends. The greatest warming trends are observed in Antarctica (0.32 °C per decade) and Middle Africa (0.21 °C per decade). Notably, 62.26 % of the area became wetter, while 22.01 % of the area shows drying trends. Northern Europe shows the largest precipitation increase, 12.49 mm per decade. Western Africa shows the fastest drying, ?21.05 mm per decade. The rescaled range analysis reveals large areas that show persistent warming trends; this behavior in SAT is more obvious than that in PR. Wave transform results show that a 1-year period of SAT variation dominates in all regions, while inconsistent 0.5-year bands are observed in East Asia, Middle Africa, and Southeast Asia. In PR, significant power in the wavelet power spectrum at a 1-year period was observed in 17 regions, i.e., in all regions studied except Western Europe, where precipitation is instead characterized by 0.5-year and 0.25-year periods. Overall, the variations in SAT and PR can be consistent with the combined impacts of natural and anthropogenic factors, such as atmospheric concentrations of greenhouse gases, the internal variability of climate system, and volcanic eruptions. 相似文献
The acceptable margin of error for the organic waste reactivity measured by the oxygen uptake method was assessed. Oxygen uptake was determined by the Dynamic Respiration Index (DRI) (mgO2/kgVS h). The composed uncertainty (uC) of the experimental set up used for the DRI test was evaluated and the uncertainty (u) of all the components of the apparatus was evaluated. A procedure for calculating the uC of the apparatus is proposed. The components affecting the uC of the DRI to a more significant extent were the one of the oxygen mass rate and the u of the amount of VS in the sample analyzed. For a confidence level of 99.73%, the extended uC (UC) interval for a DRI = 1024 mgO2/kgVS h was ±440 mgO2/kgVS h, whereas for a DRI = 3489 mgO2/kgVS h, the UC interval was ±1288 mgO2/kgVS h. When oxygen consumption and VS content become lower than 600 mgO2/h and 0.9 kg, respectively, the UC interval is similar to the measured DRI. 相似文献
This paper represents the first result of an active collaboration between the University of Sannio and the San Pio Hospital (Benevento, Italy), started in the 2018, that aims to a detailed mineralogical investigation of urinary stones of patients from Campania region. Herein, selected human bladder stones have been deeply characterized for clinical purposes and environmental biomonitoring, focusing on the importance to evaluate the concentration and distribution of undesired trace elements by means of microscopic techniques in the place of conventional wet chemical analyses. A rare bladder stone with a sea-urchin appearance, known as jackstone calculus, were also investigated (along with bladder stones made of uric acid and brushite) by means a comprehensive analytical approach, including Synchrotron X-ray Diffraction and Simultaneous Thermal Analyses. Main clinical assumptions were inferred according to the morpho-constitutional classification of bladder stones and information about patient’s medical history and lifestyle. In most of the analyzed uroliths, undesired trace elements such as copper, cadmium, lead, chromium, mercury and arsenic have been detected and generally attributable to environmental pollution or contaminated food. Simultaneous occurrence of selenium and mercury should denote a methylmercury detoxification process, probably leading to the formation of a very rare HgSe compound known as tiemannite.
Organic phosphorus(nonreactive P,NRP)is a major component of P in sediments,but information about its chemical forms and dynamic transformation is limited.The chemical forms and dynamic behaviors of NRP in a sediment profile from Lake Taihu,a freshwater and eutrophic lake in China,were investigated.Five forms of NRP in the sediments were extracted based on a chemical fractionation technique,including easily labile NRP(NaHCO3-NRP),reactive metal oxide-bound NRP(HCl-NRP),humic acid-associated NRP(NaOH-NRPHA),fulvic acid-associated NRP(NaOH-NRPFA)and residual NRP(Res-TP).There were notable transformations with increasing sediment depth from the labile NaHCO3-NRP and NaOH-NRP pools to the recalcitrant HCl-NRP and Res-TP pools,which caused the NRP to become increasingly recalcitrant as the early diagenetic processes proceeded.Further analyses showed that the relative changes in contents of organic matter and reactive Fe oxides in the sediment profile triggered a competition for binding NRP fractions and led to the transformation of NRP.The results highlighted the importance of abiotic processes in regulating the diagenesis of organic P and its stability in sediments. 相似文献