Simultaneous determination of fenitrothion and aminocarb in blueberry foliage and fruits: Application to the analysis of residues in field samples

Abstract

Samples of blueberry foliage and fruits were collected from spray blocks in Ontario after aerial application of fenitrothion and aminocarb at dosage rates of 210 g active ingredient (AI)/ha and 70 g AI/ha respectively. Residues were extracted from the samples by homogenizing with ethyl acetate, cleaned up by microcolumn chromatography using alumina as adsorbent, and analyzed by GLC‐AFID with a glass column packed with 1.5% OV‐17 and 1.95% OV‐210 on 80–100 mesh Chromosorb W‐HP. Average recoveries for fenitrothion and aminocarb from foliage at three fortification levels (1.0, 0.10 and 0.01 ppm) were respectively 99 and 96%. The corresponding values for the fruits were 99 and 95%. Foliage samples collected 1 h post‐spray contained on average 1.13 ppm of fe‐nitrothion and 1.14 ppm of aminocarb. However, residue levels reached below the detection limit (<0.01 ppm) in foliage collected 15 d after treatment. In addition, the fruit samples collected after 15 d post‐spray contained extremely low levels (0.03 ppm for fenitrothion and 0.02 ppm for aminocarb) of residues, and were barely above the detection limit.     

A comparative study on metal sorption by brown seaweed

This study compared the sorption of Ag, Cd, Co, Cd, Mn, Ni, Pb and Zn by a Ca-treated Sargassum biomass at pH 5.0, under low and high ionic strength (IS) conditions. The sorption isotherms of As [As(V)] and Cr [Cr(III) and Cr(VI)] were also determined at low IS. The isotherm data for the eight cationic metals and Cr(III) were well fitted by Langmuir equations. Generally, the maximum metal uptake (Umax) followed: Cr(III) > Pb approximately Cu > Ag approximately Zn approximately Cd > Ni approximately Mn approximately Co > Cr(VI) > As(V) at low IS and Pb > Cu > Co > Mn approximately Cd > Zn approximately Ag > Ni at high IS. As(V) did not bind to the seaweed at pH 5.0. The results indicated that sorption of Pb was not affected by the increasing IS, though the percentage of free Pb ions in the water was greatly reduced as predicted by the speciation model. High IS lowered Umax by 10-36% (except Co and Pb), and lowered the affinity constant of the metal by 33-91% for all cationic metals, as compared to low IS. Moreover, the removal efficiency of the cationic metals and Cr decreased exponentially with initial metal concentrations and was lower at high IS. Ion-exchange was the mechanism responsible for the cationic metal sorption onto the seaweed, and Na ion interfered with the cationic metal binding through electrostatic interaction. In conclusion, this study showed the differential binding capacity of the Sargassm biomass for different metals and oxidation states and the differential effects of IS. According to the present results, Sargassum may be considered a good biosorbent for cationic metals (especially Pb) in both low and high-salt containing wastewater.     

Control of hydrogen sulphide in digestor gas using iron salts

Different dosages of ferrous chloride and ferric chloride were added to digestors separately, and the volumes of methane and hydrogen sulphide contained in the digestor gas (biogas) were monitored. It was noted that the effects of adding of 16, 18 and 32 kg ferrous chloride/ tonne volatile solids, and 16 and 18 kg ferric chloride/tonne volatile solids were similarly effective in controlling the hydrogen sulphide levels.

According to an average amount of undigested sludge (primary sludge mixed with surplus activated sludge) of 41 tonne volatile solids produced each day during the sewage treatment process in Shatin sewage treatment works, and the required dosage of 16 kg ferric chloride/ tonne volatile solids, the amount of iron salts required should be 656 kg/day or 3.3 mg/L for the actual application, based on an average sewage flow of 200,000 m³/day.     

基于基础设施性能的资产管理策略(英文)

基础设施的可持续发展需要系统地研究包括资产管理在内的基础设施管理的各个相关方面。本文构建了基于基础设施性能的资产管理策略的框架,并详细讨论了其主要原则与关键内容。     

Relative sensitivity of two marine bivalves for detection of genotoxic and cytotoxic effects: a field assessment in the Tamar Estuary, South West England

The input of anthropogenic contaminants to the aquatic environment is a major concern for scientists, regulators and the public. This is especially relevant in areas such as the Tamar valley in SW England, which has a legacy of contamination from industrial activity in the nineteenth and twentieth centuries. Following on from previous laboratory validation studies, this study aimed to assess the relationship between genotoxic and cytotoxic responses and heavy metal concentrations in two bivalve species sampled from locations along the Tamar estuary. Adult cockles, Cerastoderma edule, and blue mussels, Mytilus edulis, were sampled from five locations in the Tamar and one reference location on the south Devon coast. Bivalve haemocytes were processed for comet and neutral red retention (NRR) assays to determine potential genotoxic and cytotoxic effects, respectively. Sediment and soft tissue samples were analysed for metal content by inductively coupled plasma mass spectrometry. Sediment concentrations were consistent with the physico-chemical nature of the Tamar estuary. A significant correlation (P?=?0.05) was found between total metal concentration in sediment and C. edule soft tissues, but no such correlation was found for M. edulis samples. DNA damage was elevated at the site with highest Cr concentrations for M. edulis and at the site with highest Ni and Pb concentrations for C. edule. Analysis of NRR revealed a slight increase in retention time at one site, in contrast to comet data. We conclude that the comet assay is a reliable indicator of genotoxic damage in the field for both M. edulis and C. edule and discuss reasons for the apparent discrepancy with NRR.     

Effect of food availability on egg production and packaging in the intertidal scavenging gastropod Nassarius festivus

Individuals of the scavenging gastropod Nassarius festivus (Powys) were maintained for 12 weeks at one of the three ration levels, i.e. one meal every 2, 7 or 14 d, and the effect on growth and fecundity were determined. The number and size of egg capsules, number of eggs per capsule and the calorific value of eggs together with the egg capsules decreased as food availability decreased. The size of the eggs, however, was not affected. At the end of the experiment, the cumulative mortalities were high for individuals maintained at the high and medium ration and were 56.3% and 50%, respectively, whereas the mortality was only 16.7% at the low ration. There was no increase in the shell length but a decrease in the total wet weight for all the treatments. As food availability decreased, the proportion of consumed energy allocated to reproduction decreased from 7.2% to 1.4%. This plastic life history may be a mechanism enabling scavengers to survive in an environment of which the food availability is patchy and unpredictable. Received: 14 August 1998 / Accepted: 23 July 1999