The persistence of insecticidal chemicals in soils treated with granular formulations of disulfoton and their uptake by potato plants

Abstract

Potatoes were grown from cut seed in Plainfield sand treated in‐furrow with disulfoton (Di‐Syston 15G, 3.36 kg Al/ha) in 1983 and from whole seed in similarly treated loam in 1991. Soils were contained in 2 m² field plots. Soil, seed potato and foliage were analyzed for the insecticide and its sulfoxide and sulfone metabolites during the 8–12 wk following planting. Disulfoton disappeared at different rates from the two soils (k_sand=0.024 day^‐1, k_loam=0.056 day^‐1) with partial conversion to the sulfoxide and sulfone in both. Larger quantities of the three insecticidal components were absorbed by the seed potato in the cut‐seed/sand combination. The relative amounts of these components in the seed potato also differed between treatments with disulfoton being the largest component of the cut‐seed/sand and smallest in the whole‐seed/loam. Disulfoton sulfoxide and sulfone were the major insecticidal components of the foliage and concentrations in the initial foliage (each ca. 10 ppm) were similar for both treatments. Sulfoxide concentrations in the foliage decreased more rapidly than the sulfone and the decrease in concentration of each of the components was similar for the two treatments.     

Fluid bed gasification – Plasma converter process generating energy from solid waste: Experimental assessment of sulphur species

Often perceived as a Cinderella material, there is growing appreciation for solid waste as a renewable content thermal process feed. Nonetheless, research on solid waste gasification and sulphur mechanisms in particular is lacking. This paper presents results from two related experiments on a novel two stage gasification process, at demonstration scale, using a sulphur-enriched wood pellet feed.Notable SO₂ and relatively low COS levels (before gas cleaning) were interesting features of the trials, and not normally expected under reducing gasification conditions. Analysis suggests that localised oxygen rich regions within the fluid bed played a role in SO₂’s generation. The response of COS to sulphur in the feed was quite prompt, whereas SO₂ was more delayed. It is proposed that the bed material sequestered sulphur from the feed, later aiding SO₂ generation. The more reducing gas phase regions above the bed would have facilitated COS – hence its faster response. These results provide a useful insight, with further analysis on a suite of performed experiments underway, along with thermodynamic modelling.     

Simple Modeling Tool for Reconstructing Source History Using High Resolution Contaminant Profiles From Low‐k Zones

An innovative but simple analytical modeling tool for reconstructing contaminant concentration versus time trends (i.e., “source history”) for a site using high‐resolution contaminant profiles from low permeability (low‐k) zones was developed and tested. Migration of contaminants into low‐k zones via diffusion (and possibly slow advection) produce concentration versus depth profiles that can be used to understand temporal concentration trends at the interface with overlying transmissive zones, including evidence of attenuation over time due to source decay. A simple transport‐based spreadsheet tool for generating source history estimates fit to the profiles was developed and applied to published soil concentration versus depth data from five distinct areas of four different sites contaminated with chlorinated ethenes. Using the root mean square error as an optimization metric, strong fits between measured and model‐predicted soil data were obtained in the majority of cases using site‐specific values for input parameters. In general, significant improvements could not be obtained by varying these parameters. As a result, the source history estimates generated by the tool were similar to those that had already been generated using more intensive analytical or numerical inverse modeling approaches. This included confirmation of constant source histories at locations where dense nonaqueous‐phase liquid was present (or suspected to be present), and declining source histories for locations where source isolation and/or attenuation had occurred. The advantage of the modeling tool described here is that it provides a simpler yet more dynamic method for understanding source behavior over time than existing approaches. ©2015 Wiley Periodicals, Inc.     

空气污染与儿童肺功能指标的相关分析

采用两步回归法研究了中国4城市空气污染与儿童肺功能指标的相关关系.结果表明,PM_2.5、PM₁₀、TSP等与FEV₁、FEV₁/FVC的调整均值、FEV₁/FVC≤80%的异常率有显著的统计相关关系.说明空气中颗粒物污染是导致儿童小气道通气功能障碍的重要因素之一.研究中未发现SO₂、NO_X污染与儿童的肺功能指标有统计上的相关性.     

空气污染对儿童及其父母呼吸系统健康的影响

 根据空气污染数据对广州、武汉、兰州、重庆4城市8个点位进行了空气污染的聚类分析,并按空气污染程度进行了排序.在此基础上,分析了空气污染程度与儿童及其父母呼吸系统健康的关系.发现儿童11种患病率随空气污染程度加重而呈上升趋势.污染最重组的患病率是污染较轻组的1.71(3.95倍.污染最重组的比数比(即OR值)是污染较轻组的3.313(6.942倍.空气污染对儿童父母的呼吸系统患病率也有轻度至中度的影响.     

Conspecific threat,predation avoidance,and resource defense: implications for grouping in langurs

Data on langur (Presbytis entellus) populations were gathered from the literature to test the importance of three selective pressures in determining group size and composition: predation pressure, intergroup resource defense, and conspecific threat. There were no detectable difference in the size of groups in populations facing nearly intact predator communities compared to those populations where predators were severely reduced in number or absent, although there was a trend for the number of adult males per group to increase in areas with nearly intact predator communities. Using population density as an indirect measure of the frequency of intrusions into a group’s home range and thereby as an index of the demographic pressure favoring resource defense, we predicted that higher densities would result in larger defensive coalitions and higher numbers of females per group. This prediction was not upheld. Our third selective pressure, conspecific threat, encompasses those selective forces resulting from physical attack on females, infants, and juveniles. Our index of conspecific threat uses the number of non-group males divided by the number of bisexual groups, because in langurs, the major source of conspecific threat derives from non-group males who, following group take-over, kill infants, wound females, and expel juveniles from groups. This index of conspecific threat was strongly related to the mean number of resident females, was weakly related to the mean group size, but was not related to the number of males in the group. In addition, as predicted, populations with a high index of conspecific threat had higher levels of juvenile expulsion. These analyses were corroborated by a simulation model which used a computer-generated series of null populations to calculate expected slopes of immatures regressed on adult females. These randomly generated populations, matched to means and ranges of real populations, allowed us to determine if deviations of the observed slopes from the expected null slopes could be explained by variation in predation pressure, population density, or conspecific threat. We found no evidence that predation pressure was associated with decreases in immature survival in smaller groups, as would be predicted by the predation-avoidance hypothesis. We found no evidence that immature survival was compromised by small group size in high-density populations, as would be predicted by the resource-defense hypothesis. However, as the index of conspecific threat increased, groups with larger numbers of females were more successful than groups with fewer females in reducing mortality or expulsion of immatures. Overall, conspecific threat received the strongest support as a selective pressure influencing langur group size and composition, suggesting that this selective pressure should be evaluated more widely as a factor influencing composition of animal groups. Received: 23 January 1995/Accepted after revision: 18 February 1996     

Seasonal growth in Laminaria longicuris: Relations with reserve carbohydrate storage and production

Growth rates of Laminaria longicruris increase during January and February, and the role of carbohydrate reserves as a carbon source for this growth was investigated. Seasonal variations in the levels of laminaran and mannitol showed maximum values for both in late summer. Minimum values occurred in February at the time when growth rates were increasing rapidly. Erosion of the blades in winter carried away much of the tissue containing carbohydrate reserves accumulated during the previous summer. Experimental reduction of carbohydrate reserves by fertilization with sodium nitrate during the summer did not affect subsequent winter growth rates. Truncation of the plants in November significantly reduced growth rates. The lower rate of growth is attributed to a reduction in photosynthetic area rather than a loss of storage products.NRCC No. 16478     

Testing sediment biological effects with the freshwater amphipod Hyalella azteca: the gap between laboratory and nature

The freshwater amphipod, Hyalella azteca, is widely used in laboratory sediment toxicity and bioaccumulation tests. However, its responses in the laboratory are probably very different from those in the field. A review of the literature indicates that in its natural habitat this species complex is primarily epibenthic, derives little nutrition from the sediments, and responds primarily to contaminants in the overlying water column (including water and food), not sediment or porewater. In laboratory sediment toxicity tests H. azteca is deprived of natural food sources such as algal communities on or above the sediments, and is subjected to constant light without any cover except that afforded by burial into the sediments. Under these constraining laboratory conditions, H. azteca has been reported to respond to sediment or porewater contamination. In nature, contamination of overlying water from sediment is less likely than in the laboratory because of the large, generally non-static sink of natural surface water. H. azteca does not appear to be the most appropriate test species for direct assessments of the bioavailability and toxicity of sediment contaminants, though it is probably appropriate for testing the toxicity of surface waters. Toxic and non-toxic responses will be highly conservative, though the latter are probably the most persuasive given the exposure constraints. Thus H. azteca is probably a suitable surrogate species for determining sediments that are likely not toxic to field populations; however, it is not suitable for determining sediments that are likely toxic to field populations.     

Nitrogen uptake characteristics of Chordaria flagelliformis (Phaeophyta) in batch mode and continuous mode experiments

The uptake of NH ₄ ⁺ and urea by Chordaria flagelliformis was measured in a perturbed system (batch mode) and in an apparent steady-state system (continuous mode). The maximum uptake rates (V_max) measured in short-term depletion experiments greatly exceeded those determined under a steady nutrient supply. C. flagelliformis briefly exposed to high nutrient concentrations has an impressive capacity for rapid uptake (high V_max)_which is uncoupled from growth. In contrast, under continous, homogenous low N concentrations the alga appears well equipped (low half-saturation constant, K_m) to take up the available N. The results show that previous work based on batch mode uptake experiments probably overestimated the N requirements for the growth of many seaweeds.     

Seasonal growth of Laminaria solidungula in the Canadian High Arctic in relation to irradiance and dissolved nutrient concentrations

Pontomyia is a genus of tiny flightless marine midges, with 4 described species, found on tropical or subtropical sea shores of the western Pacific Ocean. They are rarely noticed because of their small size (about 1.5 mm) and ephemeral adult life (1 to 3 h). They usually occur in association with seagrasses and seaweeds on which the larvae feed. The oar-like wings of adult males propel them over the water surface, but do not enable them to fly. Adult females are not only wingless but virtually legless. Emergence of the adults in the field may occur either during the day or at night. In a laboratory aquarium population of P. cottoni Womersley, maintained for about 18 months in a 12 h light-12 h dark cycle, males began to emerge at the end of the light period, whereas females emerged only after the onset of darkness. Field observations suggest that emergence times are probably influenced also by tides.