Alma Chávez

Accumulation and leaching potential of some pharmaceuticals and potential endocrine disruptors in soils irrigated with wastewater in the Tula Valley, Mexico.

The reuse of wastewater for irrigation of agricultural land is a well established practice but introduces many contaminants into the terrestrial environment including pharmaceuticals and personal care products. This study reports the persistence and leaching potential of a group of acidic pharmaceuticals, carbamazepine, and three endocrine disruptors in soils from the Tula Valley in Mexico, one of the largest irrigation districts in the world that uses untreated wastewater. After irrigation of soil columns with fortified wastewater over the equivalent of one crop cycle, between 0% and 7% of the total added amounts of ibuprofen, naproxen, and diclofenac and between 0% and 25% of 4-nonylphenol, triclosan, and bisphenol-A were recovered from the soil profiles. Carbamazepine was more persistent, between 55% and 107% being recovered. Amounts in leachates suggested that movement through the soil was possible for all of the analytes, particularly in profiles of low organic matter and clay content. Analysis of soil samples from the Tula Valley confirmed the general lack of accumulation of the acidic pharmaceuticals (concentrations from below the limit of detection to 0.61 μgkg(-1)) and endocrine disruptors (concentrations from below the limit of detection to 109 μgkg(-1)) despite continual addition through regular irrigation with untreated wastewater; there was little evidence of movement through the soil profiles. In contrast, carbamazepine was present in horizon A of the soil at concentrations equivalent to several years of additions by irrigation (2.6-7.5 μgkg(-1)) and was also present in the deeper horizons. The persistence and mobility of carbamazepine suggested a potential to contaminate groundwater.

Performic acid for advanced wastewater disinfection.

The disinfection efficiency of performic acid (PFA) against various microbial contaminants has been studied in municipal secondary effluent. The study demonstrated that PFA provides rapid, efficient and safe disinfection, degrading both bacteria and viruses even at low doses. The resistance order starting from the most resistant microorganism is as follows: MS2-coliphages > DNA-coliphages > enterococci and Escherichia coli. PFA is also efficient in the elimination of Salmonella spp., Clostridium perfringens spores and Giardia cysts. The results showed that a PFA dose as low as 0.5-1 mg L(-1) with contact time of 10 min was efficient in achieving and maintaining for 72 h the disinfection level required for unrestricted agricultural water reuse (≤3 log units for faecal coliforms). However, the optimal dose will depend on the quality of wastewater. Regarding the formation of by-products during disinfection with PFA, very low amounts of hydrogen peroxide and organic per-acids were observed; active oxygen was not detected. The amounts of adsorbable organically bound halogens (AOX) compounds formed were significantly lower compared to the amounts generated during chlorine disinfection. This chlorine-free solution enables compliance with microbiological criteria for various water reuse applications and is already on the market for advanced disinfection.

Regulation of Cell Division in Higher Eukaryotes

Publisher Summary This chapter presents concepts regarding the proteolytic system and updates the roles of the other systems regulating the mitotic cell cycle of higher eukaryotic cells. Major reviews have been updated in each area, but neither the meiotic cell cycle nor studies in other eukaryotic cells are analyzed in detail. First, a general overview is provided. Then regulation of the G 1 -S phase transition, regulation of the G 2 -M phase transition and exit from mitosis are discussed. The mitotic cell cycle of higher eukaryotes consists of four phases— gap phase 1 or G 1 phase, S phase, a second gap period or G 2 , and mitosis. Mitosis also consists of various phases—prophase, when chromosome condensation takes place; prometaphase-metaphase, in which two members of each pair of sister chromatids attach to microtubules; anaphase, when sister chromatids are separated and move along the microtubules; and telophase, with the reformation of nuclei and the decondensation of the chromosomes. In the first three phases, the cell prepares for cell division, which actually takes place during mitosis. To guarantee the high-fidelity transmission of genetic information, eukaryotic cells have developed a complicated network of molecules that act in a finely coordinated manner. Central participants in this process include cyclins, cyclindependent-kinases (CDKs), CDK inhibitors, transcription factors, such as the products of tumor suppressor genes (for example, pRB, p53), and the ubiquitin-mediated proteolytic system. These central participants are discussed in detail. Transgenic mice are also explained in the chapter. Once a putative molecule has been cloned and shown to be of relevance in the cell cycle in “in vitro” assays, the final goal is to test its potential regulatory activity in “in vivo” conditions. This has been achieved by the creation of transgenic mice for each one of the molecules of interest. A partial list of the transgenic mice specifically created for evaluating the activity of cell cycle regulator proteins is shown.