Effects of the herbicide imazapyr on benthic macroinvertebrates in a logged pond cypress dome

Increased herbicide use in silviculture over the last several decades has led to concern over potential water contamination, which may affect biotic health. In the southeastern United States, pine flatwoods are important for timber production and are often interspersed with cypress wetlands. Cypress domes are isolated, shallow basins that collect surficial waters from adjacent forested areas and therefore might be expected to contain pesticide from storm runoff. This study utilizes in situ microcosm experiments to assess the effects of a concentration gradient of the herbicide imazapyr (0.184, 1.84, and 18.4 mg/L, equivalent to 1, 10, and 100 times the expected environmental concentration from a normal application rate) on the macroinvertebrate community of a logged pond cypress dome using changes in macroinvertebrate composition, chironomid biomass, and chironomid head-capsule deformities. The control core was not significantly different from the surrounding cypress dome for any parameter, suggesting that enclosure effects were likely of minimal importance in the final experimental results. The lack of statistical difference (p < 0.05) in macroinvertebrate community composition, chironomid deformity rate, and chironomid biomass between treatments suggests that imazapyr did not affect the macroinvertebrate community at the concentrations tested. Chironomid deformity rate ranged from 0.97% for imazapyr control to 4.96% for the 100x treatment, with chironomid biomass being 1.79 and 1.87 mg/L, respectively.     

Distribution and retention of atrazine and carbofuran in farm pond ecosystems

The distribution and retention of atrazine and carbofuran in farm ponds were examined after application of 0.3 ppm of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine] for two years and 0.025 ppm of carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) the first year and 0.050 ppm for the second year. Samples of water, mud, and various biological components for the systems were collected periodically for residue analyses by gas chromatography. Soon after atrazine was applied, it was found in all physical and biological components. No biological magnification was observed. Carbofuran showed up only in the water and mud immediately after application; from then on it was absent from all components. No adverse effects from either pesticide were observed in the biological components.Supported in part by North Central Regional Project NC-96, Environmental implications of pesticide usage, and the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, Kansas 66506.     

The impact of Furadan 3G (carbofuran) applications on aquatic macroinvertebrates in irrigated rice in Senegal

Chemical compounds known to be teratogenic to frog embryos were tested singly and in binary mixtures and Weibull functions were used to model their concentration-response relationships. A separate Weibull function with an additive concentration variable modeled the mixtures using only single chemical test data. Seven chemicals in five binary mixtures at 3/1, 1/1, and 1/3 mixture proportions each were tested. The ratios of measured and calculated model parameters and median concentrations were estimated for comparing the results. The ratios ranged from 0.72 and 1.44 with an average at 0.99, an agreement that was qualitatively similar to modeling mixtures of narcotic chemicals which are known to produce additive concentration effects. The model reliability in determining mixture response classes and prediction of effects based on single chemical data was quantified. The model is useful for environmental risk assessment of chemical mixtures in hazardous waste sites and for the design of mixture experiments.     

Effect of prairie grass on the dissipation, movement, and bioavailability of selected herbicides in prepared soil columns

Phytoremediation of pesticide-contaminated sites using a prairie grass mixture (big bluestem, yellow indiangrass, and switch grass) has been suggested as a low-cost in situ remediation strategy. In this study, the proposed phytoremediation technique was applied to artificially prepared soil columns that were fortified with high concentrations of four herbicides (atrazine, alachlor, metolachlor, and pendimethalin). The fate and toxicity of the herbicides were compared with results from soil columns lacking vegetation. After either 150 or 240 d of phytoremediation, soils were watered with 7.5 cm of water, and leachate was collected. Columns were then divided into three sections (top, middle, bottom). For each section of the column, chemical analysis (ethyl acetate and water extractions), earthworm accumulation tests, and lettuce seedling growth tests were performed. The leachate was chemically analyzed and tested for chronic toxicity to algae. Atrazine and alachlor degraded rapidly in the column, and the total amount recoverable was less than 2% of applied. After 250 d, vegetation reduced the total recoverable amounts of metolachlor and pendimethalin by 78 and 39%, respectively. Metolachlor was the only compound found in leachate, and the amounts recovered were reduced 5- to 20-fold by vegetation. Vegetation decreased the bioavailability of pendimethalin as measured by 8-d, earthworm bioaccumulation factors (BAFs) and lettuce seedling growth assays. Decreases in mobility and bioavailability indicate that this technique may stabilize pesticide residues in addition to increasing dissipation rates.     

Evaluating ammonia toxicity in sewage effluent to stream macroinvertebrates: I. A multi-level approach

A multi-level approach incorporating instream biological response, water quality, and toxicity testing was used to evaluate the toxicity of ammonia in sewage effluent to macroinvertebrates in two Ozark border streams. Macroinvertebrate community compositions at sites upstream from effluent discharge were most similar, while communities at upstream vs downstream sites were least similar. Upstream sites had abundant mayflies, blackflies, and caddisflies, which were absent immediately below effluent discharge. Water quality was also different at upstream vs downstream sites and was significantly correlated with differences in macroinvertebrate communities (r²=–0.66, P<0.05) when data for all months were combined. However, differences in water quality could not consistently be explained by ammonia, which contributed from <1% to 31% of total variation in water quality among sites.The failure of observed NH₃-N concentrations to consistently explain differences in water quality and macroinvertebrate community composition among sites in field studies was corroborated by results of 96-h, static-renewal, ammonia toxicity tests conducted on Chironomus riparius in undiluted sewage effluent and well water. Ammonia concentrations measured in-stream were not toxic to C. riparius in toxicity tests. By using a multi-level approach, a more realistic evaluation of ammonia toxicity in sewage effluent to macroinvertebrates was obtained than by using methods that focus on only one aspect of effluent toxicity.     

Effect of herbicide residues on microbial processes in pond sediment

An assay system is described for examination of potential effects of herbicides on non-target sediment microorganisms. A key feature was to standardize a procedure for collecting and incubating intact miniature soil samples for assaying a variety of microbial activities. Potted pond sediment compared to undisturbed sediment cores showed no difference in initial carbon mineralization, acetylene reduction, phosphatase, and dehydrogenase activities, but did show a significant difference in methanogenesis. CuSO₄, after one week in pond sediment, inhibited phosphatase activity (1,000 ppm CuSO₄) and methanogenesis (20-1,000 ppm CuSO₄); no effect was noted for acetylene reduction, dehydrogenase activity and glucose mineralization. Simazine stimulated pond sediment acetylene reduction (1,000 ppm simazine); inhibited phosphatase activity (1,000 ppm simazine) and methanogenesis (50-1,000 ppm simazine); and had no effect on dehydrogenase activity and glucose mineralization. Chronic effects and effects at lower concentrations by these herbicides were less apparent. The results support the concept that a battery of tests are required to profile and evaluate the effects of herbicides on sediment microbial communities.     

Effect of endosulfan runoff from cotton fields on macroinvertebrates in the Namoi river

Of the several pesticides used in the pest management strategy for cotton, endosulfan is ranked as having the greatest impact on the riverine ecosystem. A survey of changes in the densities of six abundant macroinvertebrate taxa (ephemeropteran nymphs Jappa kutera, Atalophlebia australis, Tasmanocoenis sp., and Baetis sp. and two trichopteran larvae, Cheumatopsyche sp. and Ecnomus sp.) between upstream and downstream zones of the cotton-growing region in the Namoi River was conducted between November 1995 and February 1996. In November and December 1995, there were few differences in population densities between all sites. In January and February 1996, population densities of the study taxa increased 7- to 10-fold higher at the two reference sites, with low concentrations of endosulfan in sediment and in passive samplers placed in the water column. In contrast, densities of these taxa at sites with exposure to 25-fold higher concentrations of endosulfan remained static and were between one and two orders of magnitude lower than densities at the reference sites in January and February. Population densities of Baetis sp., a mobile ephemeropteran, did not indicate any inverse relationship with endosulfan concentrations. Multivariate redundancy analysis indicated that endosulfan concentrations were the leading environmental predictor of changes in density of the five benethic taxa. Laboratory 48-h LC50 values of technical endosulfan in river water were 0.6, 1.3, and 0.4 ppb for early-instar nymphs of A. australis and J. kutera, and larvae of Cheumatopsyche sp., respectively. Endosulfan sulfate formed a large proportion of the total endosulfan concentrations measured from in situ passive samplers, indicating that its main route of entry into the river is through surface runoff during storm events.     

An outbreak of viral meningitis associated with a public swimming pond

From July to October 2001, 215 cases of aseptic meningitis occurred among the inhabitants of the German city of Kassel and neighbouring counties. A matched case-control study identified bathing in a public, nature-like pond during the beginning of the outbreak as a risk factor for disease [matched odds ratio (mOR) 44.8, 95% confidence interval (CI) 3.9-515.6]. Among bathers, patients with meningitis spent more time in the water (mOR 18.8, 95% CI 2.0-174.1) and swallowed water more frequently (mOR = 7.3, 95% CI 0.7-81.8). Of 30 cerebrospinal fluid samples tested, echovirus 30 was cultured from 16, and echovirus 13 from seven. An echovirus 30 sequence obtained from one pond water sample showed a 99% nucleotide and 100% amino-acid homology with patient isolates. This outbreak demonstrates the potential of nature-like swimming ponds to cause widespread community infection with substantial public health impact.     

Effect of zinc on diversity of riverine benthic macroinvertebrates: estimation of safe concentrations from field data

We conducted field surveys at 25 sites in three Japanese catchments to provide conservative estimates of the safe concentration of zinc (Zn) for the protection of riverine macroinvertebrate diversity. The relationships between the Zn concentration and six macroinvertebrate metrics for taxon richness were determined by using regression analysis; this included a piecewise regression model, where two lines are joined at an unknown point. For each metric the piecewise regression model with a zero slope below a threshold concentration was selected as the best model to explain the influence of Zn. Under the assumption that macroinvertebrate diversity reductions of <10% are acceptable, the safe concentrations of Zn were estimated to be 84, 115, 84, 80, 85, and 70 μg/L for total taxon richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, mayfly richness, caddisfly richness, chironomid richness, and estimated total taxon richness at the riffle scale, respectively. These concentrations are more than twice the water quality standard for Zn in Japan (30 μg/L), suggesting that the standard is likely overprotective for macroinvertebrate diversity. Field studies are useful for evaluating the level of protectiveness of safe concentrations (water quality standards) based on individual-level effects from laboratory toxicity tests, and this evaluation process will have a crucial role in implementing more purpose-driven ecological risk managements that aim to protect natural populations and communities.     

Effects of using a Charnley-Howorth enclosure in a district general hospital

A high rate of infection was found to occur when total hip replacement were performed in an operating theatre used by a variety of surgical specialities. Because of this, a downward displacement laminar flow enclosure was installed to provide ultraclean air operating conditions. Retrospective examination of 419 total hip replacements, carried out over a six-year period during which the enclosure was installed, showed a reduction in the infection rate from 3.2% to 0.4% (P = 0.05) when using the enclosure. The infections were associated with a postoperative wound discharge and with revision surgery but were less frequent when the enclosure was used. Prosthetic loosening was found to be common when metal-to-metal prostheses were used. Working in an enclosure with side panels, wearing body exhaust units, was generally considered to be so noisy as to restrict communication.