Lead and potential health risks from subsistence food crops in urban Kenya

Lead, zinc and cadmium were analysed in a range of subsistence crops cultivated in and around Nairobi city centre. Lead was found to be the only contaminant of concern, being widely dispersed with elevated levels found in crops and soils from both suburban and city centre areas. Extremely high concentrations were recorded in the edible portions of a variety of crops, and high soil Pb levels were recorded within 30m of busy roads. Based on these data, it is estimated that subsistence on a diet of crops cultivated in and around Nairobi could increase Pb intake by 10–100 times the FAO/WHO maximum tolerable levels, potentially contributing substantially to existing health problems.     

Groundwater management by watershed agencies: an evaluation of the capacity of Ontario's conservation authorities

Watershed-based resource management organizations around the world are becoming more involved in groundwater management. This reflects, among other considerations, growing awareness of the critical role that these local agencies can and should play in the management of groundwater resources. Ontario's conservation authorities (CAs) are an important example. CAs are taking on new responsibilities for groundwater data collection, monitoring and planning. Unfortunately, not all local organizations are equally capable of participating effectively in groundwater management. This certainly is the case among Ontario's 38 CAs, which have highly variable levels of financial and staff resources. Local capacity for water management can be explored from the perspective of the institutional environment, the watershed community, and the financial, technical and staff resources of the organizations. This paper presents an evaluation of the groundwater management capacity of Ontario's conservation authorities, drawing on two detailed case studies (the Upper Thames River CA and the Ganaraska Region CA), and additional data gathered from all 38 CAs. Institutional issues, such as the clarity of management roles and senior government commitment to local management, as well as resourcing concerns, local working relationships, and public support, largely determine the capacity of CAs to expand their involvement in groundwater management. Strengthening the capacity of watershed-based agencies to participate in groundwater management is an important challenge in all jurisdictions, as these agencies are well placed to reinforce municipal groundwater management by identifying local needs and trends, facilitating communication and cooperation, and promoting best management practices.     

Community Capacity for Adaptation to Climate-Induced Water Shortages: Linking Institutional Complexity and Local Actors

There is growing concern for the capacity of urban and rural communities to manage current water shortages and to prepare for shortages that may accompany predicted changes in climate. In this paper, concepts relating to the notion of climate adaptation and particularly capacity building are used to elucidate several determinants of community-level capacity for water management. These concepts and criteria are then used to interpret empirically derived insights relating to local management of water shortages in Ontario, Canada. General determinants of water-related community capacity relate to upper tier political and institutional arrangements; the characteristics of, and relationships among, pertinent agencies, groups, or individuals involved in water management; and the adequacy of financial, human, information, and technical resources. The case analysis illustrates how general factors play out in local experience. The findings point to geographically specific factors that influence the effectiveness of management. Key factors include collaboration between water managers, clarification of agency roles and responsibilities, integration of water management and land-use planning, and recognition and participation of both urban and rural stakeholders, whose sensitivities to water shortages are spatially and temporally variable.     

Cadmium phytoextraction using short-rotation coppice Salix: the evidence trail

A substantial body of evidence has now accumulated that raises expectations that clean-up of Cd-contaminated land can be achieved through cultivation and harvest of selected clones of short-rotation coppice willow within a realistic crop lifecycle. Cd uptake rates into Salix are high compared to other trace elements and to other plant species. Effective phytoextraction would require (i) careful targeting of hotspots, (ii) repeated harvest prior to leaf fall and (iii) final removal of the root bole.     

SURFACE WATER QUALITY IMPACTS OF TILLAGE PRACTICES UNDER LIQUID SWINE MANIJRE APPLICATION1

ABSTRACT: Field studies were conducted to investigate the effects of tillage practices on the saturated hydraulic conductivity, and quantity and quality of surface runoff water resulting from the application of the liquid swine manure as a fertilizer. As part of the study, infiltration experiments were conducted on silt-loam soil with no-tillage (NT) and disk tillage (DT) practices. Liquid swine manure was applied on test plots, and the rainfall was applied by the portable rainfall simulator. The infiltration data was analyzed for the saturated hydraulic conductivity (K8) and runoff volume determinations. The surface runoff water was analyzed for total N, total P, ammonia, and nitrate concentration determinations. The study indicated that the tillage had significant effects on K_s, and quantity and quality of runoff water. The K_s values of the NT plots were found to vary from 0.693 to 1.734 mm/min, with a mean of 1.494 mm/min, while they varied from 1.056 to 2.543 mm/min, with a mean of 2231 mm/mm in the DT plots. The total N, total P, ammonium nitrogen and nitrate nitrogen concentrations were lower in runoff generated from DT plots, compared to that from the NT plots. The chemical concentration levels were significantly different in runoff waters collected one-day after manure application than in those collected 40-days after the manure application. Study suggested that the DT practice must be preferred over the NT practice if liquid swine manure is used as the fertilizer. The study is further continued to assess the long-term impacts of swine manure application and tillage on the quantity and quality of surface runoff water.     

"超级杂草"伴随着转基因作物而出现

最初的转基因大豆被基因工程业誉为“万金油”。它们能够在有除草剂的环境下生长，从理论上说，这将导致田地里那些不受欢迎的植物(比如杂草)的末日。这也将减少种植费用和除草剂的使用量。然而，多年来转基因技术的反对者们的预言现在已经变成了事实：随着时间的推移，“杂草”与转基因植物一样也具备了耐除草剂的特性。这便意味着必须应用其它除草剂，带来更多的花费。     

Further predictors of renal dysplasia in fetal obstructive uropathy: Bladder pressure and biochemistry of ‘fresh’ urine

Urine was aspirated on two consecutive days from the dilated bladder of nine fetuses with lower urinary tract obstruction. Gestational age ranged from 17 to 35 weeks. Renal dysplasia was diagnosed histologically in four fetuses, whereas the other five had normal renal histology or only partial dysplasia. Urinary sodium (Na⁺) and osmolality (Osm) decreased significantly in the second urine sample 1 day after bladder emptying (median decrease: Na⁺ = −11.3 per cent; Osm= −13.3 per cent). Although there were no significant differences between fetuses with or without renal dysplasia, normalization of an initially raised urine Na ⁺ concentration occurred at the second sample in a fetus with partially normal renal histology, thus correcting a false-positive diagnosis of dysplasia. Bladder pressure was measured at the time of the first urine sampling in seven fetuses and in a further eight with bladder outlet obstruction undergoing a single urine aspiration at 18–28 weeks. Bladder pressure was increased above the reference range in 8 of 15 fetuses with urinary obstruction, but there was no correlation between pressure and the degree of impairment of renal function. Although no conclusive clinical guidelines can be drawn from this study for the evaluation of fetal renal function, these findings suggest that, in lower urinary tract obstruction, tubular reabsorption is impeded by the standing pressure in the urinary tract and that improvement of renal function may occur following relief of obstruction.     

High-temperature tolerance of photosynthesis in the red alga Chondrus crispus

Chondrus crispus (Stackhouse) is a perennial red seaweed, common in intertidal and shallow sublittoral communities throughout the North Atlantic Ocean. In the intertidal zone, C. crispus may experience rapid temperature changes of 10 to 20C° during a single immerison-emerision cycle, and may be exposed to temperatures that exceed the thermal limits for long-term survival. C. crispus collected year-round at Long Cove Point, Chamberlain, Maine, USA, during 1989 and 1990, underwent phenotypic acclimation to growth temperature in the laboratory. This phenotypic acclimation enhanced its ability to withstand brief exposure to extreme temperature. Plants grown at summer seawater temperature (20°C) were able to maintain constant rates of lightsaturated photosynthesis at 30°C for 9 h. In contrast, light-saturated photosynthetic rates of plants grown at winter seawater temperature (5°C) declined rapidly following exposure to 30°C, reached 20 to 25% of initial values within 10 min, and then remained constant at this level for 9 h. The degree of inhibition of photosynthesis at 30°C was also dependent upon light intensity. Inhibition was greatest in plants exposed to 30°C in darkness or high light (600 mol photons m^-2s^-1) than in plants maintained under moderate light levels (70 to 100 mol photons m^-2s^-1). Photosynthesis of 20°C-acclimated plants was inhibited by exposure to 30°C in darkness or high light, but the degree of inhibition was less than that exhibited by 5°C-grown plants. Not only was light-saturated photosynthesis of 20°C plants less severely inhibited by exposure to 30°C than that of 5°C plants, but the former also recovered faster when they were returned to growth conditions. The mechanistic basis of this acclimation to growth temperature is not clear. Our results indicate that there were no differences between 5 and 20°C-grown plants in the thermal stability of respiration, electron transport associated with Photosystems I or II, Rubisco or energy transfer between the phycobilisomes and Photosystem II. Overall, our results suggest that phenotypic acclimation to seawater temperature allows plants to tolerate higher temperatures, and may play an important role in the success of C. crispus in the intertidal environment.     

TARGETING REMEDIAL MEASURES TO CONTROL NONPOINT SOURCE POLLUTION1

ABSTRACT_: The watershed model GAMES is used for the evaluation of a targeting approach to control fluvial sedimentation arising from soil erosion in agricultural areas. The data considered for the analysis consists of output from the application of the model to existing and hypothetical soil and crop management systems in two small watersheds of southern Ontario, one in the rolling uplands and the other in a very flat lowland area. The model output includes estimates of spring sediment yield from field-size cells to the stream outlet for existing agricultural management conditions, and estimates of sediment yield resulting from the successive implementation of two levels of soil erosion controls under four remedial measures strategies. The results reveal that, for the rolling upland watershed exhibiting a wide range of soil erosion and sediment yield rates, targeted control programs can be expected to provide an extremely effective approach to sediment control. For flat lowland watersheds, exhibiting relatively uniform soil erosion and sediment yield rates, the strategy of targeting controls may be somewhat more effective than a random approach to control, but not as efficient as in the case of watersheds in more rolling terrain. It is evident from the study that a screening model such as GAMES provides a very useful tool for the planning and evaluation of erosion and sediment control programs.     

Prolonged mating in the milkweed leaf beetle Labidomera clivicollis clivicollis (Coleoptera: Chrysomelidae): a test of the “sperm-loading” hypothesis

Summary Female milkweed leaf beetles (Labidomera clivicollis clivicollis) frequently mate with more than one male, and pairs form mating associations which last for up to 42 h in the field. I tested the hypothesis that males remaining with females for long periods of time benefit by numerically overwhelming the sperm of their competitors. Male L.c.clivicollis copulated intermittently with females throughout an 11 hour period in the laboratory. When virgin females were allowed a single copulation, 94.3% of the sperm they received were located in the spermatheca immediately afterward. Males were not sperm-depleted, for they had large numbers of sperm available after one copulation (mean=230,000±43,200); the maximal number of sperm a male transferred to a female in 24 h was 30,500. There was a positive linear relationship between the number of sperm transferred and time up to 24 h after mounting (r ²=0.178, P<0.003). These data suggest that males transfer increasing numbers of sperm throughout a 24-h-period. Mating duration was the most important determinant of paternity when females were placed with one male for 24 h and another male for 6 hours. Females whose first matings were longer showed first male sperm predominance (as determined by starch-gel electrophoresis), while females whose second matings were longer showed last male sperm predominance. In view of these data, it is puzzling that males do not inseminate with large numbers of sperm immediately after mounting the female. It is possible that female refractory behaviors make insemination difficult and favor prolonged mating by male milkweed leaf beetles.