Organic chloramines in drinking water: An assessment of formation, stability, reactivity and risk

© 2016 Elsevier Ltd. Although organic chloramines are known to form during the disinfection of drinking water with chlorine, little information is currently available on their occurrence or toxicity. In a recent in vitro study, some organic chloramines (e.g. N-chloroglycine) were found to be cytotoxic and genotoxic even at micromolar concentrations. In this paper, the formation and stability of 21 different organic chloramines, from chlorination of simple amines and amino acids, were studied, and the competition between 20 amino acids during chlorination was also investigated. For comparison, chlorination of two amides was also conducted. The formation and degradation of selected organic chloramines were measured using either direct UV spectroscopic or colorimetric detection. Although cysteine, methionine and tryptophan were the most reactive amino acids towards chlorination, they did not form organic chloramines at the chlorine to precursor molar ratios that were tested. Only 6 out of the 21 organic chloramines formed had a half-life of more than 3 h, although this group included all organic chloramines formed from amines. A health risk assessment relating stability and reactivity data from this study to toxicity and precursor abundance data from the literature indicated that only N-chloroglycine is likely to be of concern due to its stability, toxicity and abundance in water. However, given the stability of organic chloramines formed from amines, more information about the toxicity and precursor abundance for these chloramines is desirable

Efeitos de imidazolinonas e sulfoniluréias sobre a produção de sementes e emergência de plântulas de quinquilho

Em 1990, 91 e 92 foi conduzido ensaio na Faculdade de Agronomia da UFRS, em Porto Alegre, RS, cujo objetivo foi investigar os efeitos de herbicidas aplicados durante a fase reprodutiva de quinquilho (Datura stramonium). Foram testados dois compostos imidazolinonas (imazaquin e imazethapyr) e duas sulfoniluréias (chlorimuron e metsulfuron) sobre a produção de sementes e viabilidade e germinação das sementes formadas. Todas as aplicações berbicidas realizadas no florescimento, exceto metsulfuron na meia-dose, reduziram em mais de 75% a produção de sementes. As aplicações herbicidas efetuadas no florescimento de quinquilho reduziram em 76% o número de sementes por planta em comparação aos tratamentos aplicados no enchimento de grãos. Na avaliação da viabilidade das sementes não se constatou efeitos dos herbicidas testados. Herbicidas aplicados na fase reprodutiva de quinquilho permitiram reduzir a perpetuação da mesma por diminuir a produção de suas sementes

Injúria potencial de herbicidas de solo ao girassol: I - clomazone Potential sunflower injury by soil applied herbicides: I - clomazone

Conduziu-se um ensaio de campo na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul, em Eldorado do Sul, RS, em 1989/90. O objetivo deste trabalho foi determinar o efeito residual potencial do herbicida clomazone, aplicado em três doses à superfície do solo (PRE) ou incorporado no mesmo (PPI), sobre a cultura de girassol. Através de ensaio complementar, realizado em casa-de-vegetação em 1990, procurou-se determinar o local de absorção de clomazone por plântulas de girassol. A localização de clomazone no solo foi muito importante na determinação de sua injúria para o girassol. A campo, clomazone promoveu injúria mais acentuada nas plântulas, quando aplicado em PRE do que em PPI. Clomazone, aparentemente, foi mais absorvido pelo hipocótilo do que pelo sistema radicular das plantulas de girassol. No entanto, nas maiores doses, a fitotoxicidade em PPI se acentuou com o decorrer do tempo, a ponto de desaparecerem as diferenças entre épocas de aplicação.<br>A field experiment was carried out during 1989/90 at the Eldorado do Sul Experimental Station of Federal University of Rio Grande do Sul, Brazil, with the objective of evaluating potential injury to sunflower by clomazone applied at three different dosages in pre-emergence (PRE) or preplant incorporated (PPI). A greenhouse trial was carried out in 1990 to determine the site of uptake for clomazone from the soil. Clomazone placement in the soil was very important in determining the level of injury to the plants. The leved of injury to seedlings was higher when clomazone was sprayed in PRE as compared to PPI. Apparently, more clomazone was absorbed through the sunflower hypocotyl than by the root system. Late season assessments indicated that higher dosages were equally phytotoxic under both application methods

Neural circuit tuning fly visual neurons to motion of small objects: II. Input organization of inhibitory circuit elements revealed by electrophysiological and optical recording techniques

Egelhaaf M, Borst A, Warzecha A-K, Flecks S, Wildemann A. Neural circuit tuning fly visual neurons to motion of small objects: II. Input organization of inhibitory circuit elements revealed by electrophysiological and optical recording techniques. Journal of neurophysiology. 1993;69(2):340-351.1. The FD1-cell in the visual system of the fly is an identified visual interneuron that is specifically tuned to motion of small objects. In the companion paper it was shown that this response property is mediated by one of the two CH-cells, the VCH-cell, that inhibits the FD1-cell by GABAergic synapses. Here the input organization of the two CH-cells is analyzed by both electrophysiological and optical recording techniques. 2. Both CH-cells are excited by front-to-back motion in the ipsilateral and by back-to-front motion in the contralateral visual field. They respond maximally to binocular rotatory motion about the vertical axis of the animal. The latter response is only slightly less than the sum of the corresponding monocular response components. The relative contribution of the ipsi- and contralateral eye to the binocular response varies considerably between flies. In extreme cases it is dominated by either the ipsi- or the contralateral eye. The two CH-cells are not equally sensitive along the vertical axis of the eye. The DCH-cell has its sensitivity maximum in the dorsal part, the VCH-cell in the ventral part of the visual field. 3. The CH-cells have two arborizations, a large one in the posterior part of the third visual neuropil, the lobula plate, and a smaller one in the ipsilateral ventrolateral brain. With the calcium-sensitive dye fura-2 as an activity marker, it is analyzed which of these branches of the CH-cells receive the ipsi- and contralateral motion input, respectively. During motion in the preferred direction within the ipsilateral visual field, calcium accumulates only in the CH-cells' main arborization in the lobula plate but not in their branches in the ventrolateral brain, indicating that the arborization in the lobula plate is postsynaptic to the ipsilateral input. In contrast, contralateral motion in the preferred direction leads to calcium accumulation in both arborizations, suggesting that both are postsynaptic to contralateral input elements. During preferred direction motion in the upper or lower part of the ipsilateral visual field, calcium accumulates in only dorsal or ventral branches of the CH-cells' arborization in the lobula plate, respectively, revealing that their ipsilateral motion input is organized retinotopically. Because this arborization, most likely, is also the main output terminal of the CH-cells, it is both pre- and postsynaptic. This specific neuronal design is discussed with respect to its consequences for the mechanism of tuning the FD1-cell to motion of small objects

Injúria potencial de herbicidas de solo ao girassol: IV - rendimento de aquênios e componentes do rendimento

Conduziu-se um ensaio em campo na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul, em Eldorado do Sul, RS, em 1989/90. O objetivo foi determinar o efeito dos herbicidas clomazone, chlorimuronethyl, imazaquin e imazethaphyr, aplicados em três doses à superfície do solo (PRE) ou incorporados no mesmo (PPI), sobre o rendimento de aquênios de girassol e seus componentes. Os herbicidas de solo para controle de plantas daninhas na cultura da soja com maior potencial de dano ao girassol cultivado em sucessão, conforme indicado pelo rendimento de aquênios, foram os seguintes, em ordem decrescente: imazaquin > clomazone > imazethapyr> chlorimuron-ethyl. O efeito mais pronunciado dos herbicidas foi a redução da população de plantas. Este foi o fator que mais influenciou no rendimento do girassol

Efeitos de herbicidas aplicados no período reprodutivo sobre o crescimento inicial de plantas daninhas na geração seguinte Effects of herbicides applied during reproductive period on initial growth of weed seedlings of the next generation

Em 1990, 91 e 92 foi conduzido experimento na Faculdade de Agronomia da UFRS, em Porto Alegre, RS, com o objetivo de avaliar os efeitos de herbicidas aspergidos durante a fase reprodutiva em balãozinho (Cardiospermum halicacabum), corriola (Ipomoea grandifolia) e quinquilho (Datura stramonium). Foram testados dois compostos imidazolinonas (imazaquin e imazethapyr) e duas sulfoniluréias (chlorimuron e metsulfuron), e avaliadas as áreas foliar e cotiledonar, estatura e matéria seca das plântulas da geração seguinte. Em quinquilho, as áreas foliar e cotiledonar das plântulas aspergidas não diferiram da testemunha. Já as estaturas de balãozinho e quinquilho foram afetadas pelos herbicidas: em quinquilho, especialmente por clorimuron; em balãozinho, além de clorimuron, também por metsulfuron. Diversos tratamentos afetaram a matéria seca total ou de segmentos de plântulas de quinquilho. Em corriola não se constataram efeitos dos tratamentos herbicidas nas variáveis avaliadas. De modo geral, as características de plântulas da geração seguinte foram afetadas por alguns herbicidas aplicados na fase reprodutiva, como matéria seca em quinquilho e estatura em balãozinho, dependendo do produto, dose e época de aplicação.A trial was conducted in 1990, 91 and 92 at Federal University of Rio Grande do Sul, in Porto Alegre, RS, Brazil, to investigate the effects of herbicides sprayed during the reproductive period of balloonvine (Cardiospermum halicacabum), morningglory (Ipomoea grandifolia), and jimsonweed (Datua stramonium). Two imidazolinones (imazaquin and imazethapyr) and two sulfonylureas (chlorimuron and metsulfuron) were tested and evaluated on foliar and cotyledonar areas, plant height, and dry matter of weed seedlings. ln jimsonweed, foliar and cotyledonar areas of seedlings did not differ from the control. However, the beights of ballonvine and jimsonweed seedlings were affected by the herbicides: in jimsonweed specially by chlorimuron, in baloonvine by chlorimuron, and metsulfuron. Multiple treatment influenced total plant dry matter and also dry matter of some components of jimsonweed plants. ln morningglory no effects of herbicide treatment on the traits evaluated were observed. ln general, characteristics of seedlings of the next generation were influenced by some herbicides applied during the reproductive period of the mother plants, for example dry matter in jimsonweed and height in baloonvine, depending on the compound and rate used and its time of application

Continuous expansion of the geographic range linked to realized niche expansion in the invasive Mourning gecko Lepidodactylus lugubris (Duméril & Bibron, 1836).

Lepidodactylus lugubris is a parthenogenetic gecko which has been increasingly expanding its range during the last century. This invasive species has been reported from multiple tropical and subtropical countries in five continents, most of which were colonized in recent times. In order to understand how the realized niche of the species was affected by this dramatic geographic range expansion, we reconstructed the history of the geographic range expansion. We built models of the realized niche of the species at different points in time during the invasion process. This was achieved through the implementation of modern hypervolume construction methods, based on the Hutchinson's niche concept. The models were then compared to detect possible realized climatic niche expansion over time. Furthermore, we investigated possible pathways used by the species to spread. A progressive expansion of the realized niche was identified. As the species spread into new areas, we observed a tendency to colonize regions with warmer temperatures and higher precipitation rates. Finally, we found evidence for cargo shipping being the major pathway through which the species expands its range. Further studies on this topic should aim to investigate the role of biological interactions, and how they shape the distribution of L. lugubris on a global scale. A deeper understanding of this kind of processes will help us tackle the issue of invasive species, which has become a major challenge in conservation biology