POTENTIAL IMPACT OF IRRIGATION ON WATER RESOURCES IN THE LITTLE WABASH BASIN OF ILLINOIS1

The level of water demand for supplemental irrigation and the impact of such demand on water supplies were estimated, as a function of the price of corn (Zea Mays L.). The method of estimation was based on an economic analysis of irrigation practice which assumed constant irrigation costs, profit maximizing behavior on the part of irrigators, and which was deliberately structured to underestimate the level of irrigation water use. The analysis was applied to and used data from the Little Wabash basin in Illinois. No irrigation was predicted at a corn price below $3.50 per bushel. Between $3.50 and about $6.50 per bushel, irrigation was estimated to be profitable for a small region of the basin where acceptable groundwater was available. Above about $6.50 to $7.50, irrigation was found to be profitable in the remainder of the basin, where impoundment storage was required. The potential impact on the water resources of the basin is significant. For a corn price between $3.50 and about $6.50, the probability of a shortfall, defined as the event where the potential demand exceeds the supply, was estimated to be between 2 percent and 20 percent during the growing season. Above about $7.50, this probability was found to be about one-third. The development of policies to control withdrawals for irrigation and other uses is endorsed.     

The challenge of providing environmental flow rules to sustain river ecosystems.

Accounting for natural differences in flow variability among rivers, and understanding the importance of this for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide, is a great challenge for water managers and scientists. Nevertheless, despite considerable progress in understanding how flow variability sustains river ecosystems, there is a growing temptation to ignore natural system complexity in favor of simplistic, static, environmental flow "rules" to resolve pressing river management issues. We argue that such approaches are misguided and will ultimately contribute to further degradation of river ecosystems. In the absence of detailed empirical information of environmental flow requirements for rivers, we propose a generic approach that incorporates essential aspects of natural flow variability shared across particular classes of rivers that can be validated with empirical biological data and other information in a calibration process. We argue that this approach can bridge the gap between simple hydrological "rules of thumb" and more comprehensive environmental flow assessments and experimental flow restoration projects.     

Sequential removal of heavy metals ions and organic pollutants using an algal-bacterial consortium

The residual algal-bacterial biomass from photosynthetically supported, organic pollutant biodegradation processes, in enclosed photobioreactors, was tested for its ability to accumulate Cu(II), Ni(II), Cd(II), and Zn(II). Salicylate was chosen as a model contaminant. The algal-bacterial biomass combined the high adsorption capacity of microalgae with the low cost of the residual biomass, which makes it an attractive biosorbent for environmental applications. Cu(II) was preferentially taken-up from the medium when the metals were present both separately and in combination. There was no observed competition for adsorption sites, which suggested that Cu(II), Ni(II), Cd(II), and Zn(II) bind to different sites and that active Ni(II), Cd(II) and Zn(II) binding groups were present at very low concentrations. Therefore, special focus was given to Cu(II) biosorption. Cu(II) biosorption by the algal-bacterial biomass was characterized by an initial fast cell surface adsorption followed by a slower metabolically driven uptake. pH, Cu(II), and algal-bacterial concentration significantly affected the biosorption capacity for Cu(II). Maximum Cu(II) adsorption capacities of 8.5+/-0.4 mg g-1 were achieved at an initial Cu(II) concentration of 20 mg l-1 and at pH 5 for the tested algal-bacterial biomass. These are consistent with values reported for other microbial sorbents under similar conditions. The desorption of Cu(II) from saturated biomass was feasible by elution with a 0.0125 M HCl solution. Simultaneous Cu(II) and salicylate removal in a continuous stirred tank photobioreactor was not feasible due to the high toxicity of Cu(II) towards the microbial culture. The introduction of an adsorption column, packed with the algal-bacterial biomass, prior to the photobioreactor reduced Cu(II) concentration, thereby allowing the subsequent salicylate biodegradation in the photobioreactor.     

Tradescantia micronucleus test indicates genotoxic potential of traffic emissions in European cities

Urban atmospheres contain complex mixtures of air pollutants including mutagenic and carcinogenic substances such as benzene, diesel soot, heavy metals and polycyclic aromatic hydrocarbons. In the frame of a European network for the assessment of air quality by the use of bioindicator plants, the Tradescantia micronucleus (Trad-MCN) test was applied to examine the genotoxicity of urban air pollution. Cuttings of Tradescantia clone #4430 were exposed to ambient air at 65 monitoring sites in 10 conurbations employing a standardised methodology. The tests revealed an elevated genotoxic potential mainly at those urban sites which were exposed to severe car traffic emissions. This bioassay proved to be a suitable tool to detect local 'hot spots' of mutagenic air pollution in urban areas. For its use in routine monitoring programmes, however, further standardisation of cultivation and exposure techniques is recommended in order to reduce the variability of results due to varying environmental conditions.     

Levels and distribution of organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers in sediments and biota from the Danube Delta, Romania

Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and analogues, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), were measured in sediments and biota (invertebrates, 11 fish species and cormorant tissues) collected in 2001 from the Danube Delta, the biggest European wetland. DDTs were the predominant pollutants in all samples. A high variability in the concentrations of pollutants within the same species was observed and this was related to sampling location, age, length and sex. DDTs were also the main organohalogenated contaminants in cormorant muscle and liver, followed by PCBs, HCHs, HCB and PBDEs. The present levels of DDTs in cormorant tissues are lower than levels measured in cormorant eggs sampled from the Danube Delta in 1982 and 1997, respectively. The variance of delta15N for herbivores was much greater than for carnivores, while carp and bream showed higher delta15N signatures than expected, probably due to a higher dietary proportion of benthos, typically more delta15N enriched relative to pelagic biota.     

High-energy milling to decontaminate soils polluted by polychlorobiphenyls and atrazine

Mechanical energy has been used so far for running chemical reactions and for preparing new materials in absence of solvents. Very recently, the technology has been applied to solve environmental problems. In this paper, we describe the application of high-energy milling (HEM) for the remediation of soils contaminated by chlorinated organic compounds such as polychlorobiphenyls (PCBs) and agrochemicals like atrazine. NaBH₄ and LiAlH₄ have been successfully used for the total dehydrohalogenation of both classes of compounds, leaving a residue lower than 2 ppmw of the starting compound in the treated soil. LiAlH₄ was found to be more active than NaBH₄.     

Courtship display by great frigatebirds, Fregata minor: an energetically costly handicap signal?

We used detailed time-budget observations, mark-resight data, and doubly labeled water estimates of energy expenditure to test whether energy spent on courtship display by male frigatebirds functions as a sexually selected handicap signal. During a 2-day period of time budget observations, males displayed on average 29.5% of the time (range 0–100% for 15 different males), and this value was correlated with an index of season-long display effort. Season-long display effort was strongly predictive of pairing success. Average field metabolic rate (FMR) during the 2-day time budget period was 676.5 kJ/day (range 464.8–1035.0), substantially lower than the mass-specific FMR predicted from studies of other seabirds during incubation or chick-rearing. Despite a low overall FMR, display effort could function as an energetic handicap, either if FMR correlates positively with the amount of courtship performed or if high-quality males display at a high rate because they pay a lower energy cost per unit of display than do low-quality males. We found no relationship between FMR and display rate, despite good power for doing so. We also did not find a significant difference in energy spent divided by courtship time for males that were or were not chosen by females (inferred to be high- and low-quality males, respectively), though the medians differed in the predicted direction (preferred males having lower relative costs than non-preferred males) and the confidence interval on the difference between groups was very wide. Thus, we found evidence that male courtship effort is predictive of pairing success, we rejected one mechanism by which energetic cost of display could function as a handicap, and our test of the alternate energetic handicap mechanism was equivocal.     

若尔盖西部草甸的基本类型、特点及近几十年来的变化

2000年8月对若尔盖西部草地的调查，确定了该地18个草丛类型（不包括典型的沼泽植被）。经群丛间Pearson最大相关系数配合生境作图，将该地区的草地群丛分成3大类，即沼生草地，中生性草甸和旱生性草地。各群丛的SW指数，物种丰富度，地上生物量，裸地面积按照生境序列作图，显示中性草甸具有最高的物种丰富度和地上生物量。群丛C和J分别是沼生和旱生植被与中生性草甸之间的拐点式过渡类型，其物种丰富度明显比周期的群丛低，生境转换关键种分别为鹅绒委陵菜和垂穗披碱草。在草地物种组成上，杂类草占81．3％，莎草类仅占6．8％；群丛建群种方面，杂类草占61％，莎草类占28％；在次优势种方面，杂类草和禾草所占比重都有所增加。草原成分出现在丛中生至旱生的群丛中，在有些群丛中甚至成为次优势种。沼泽消退，黄河河道附近沙化以及过牧的阳坡山地生长带刺的旱生化植被，说明当地正经历着干旱化的过程，原因不仅有自然的还有人为的，特别是草地的过度使用。最后对当地草场的管理及发展提出了一些建议。图3表2参20     

Distribution of organochlorine pesticides, polychlorinated biphenyls and alpha-HCH enantiomers in pork tissues

The distribution of HCH isomers, DDT analogues and selected PCB congeners in pork organs collected from the same individuals raised in Romanian farms was investigated. Organochlorine pesticides (HCHs and DDTs) were the principal contaminants in all samples, while PCB concentrations were low, in accordance with previously reported concentrations from Romanian animal farms. The most part of the pollutant load in the body is retained in the adipose tissue, with HCHs ranging between 16 and 27.7 ng/g lipid and with higher concentrations of DDTs ranging between 65.9 and 334.5 ng/g lipid. The highest PCB levels (up to 32 ng/g lipid) were measured in lung and liver. The lipid-normalized concentrations in the brain were lower than in all other tissues due to the presence of the blood-brain barrier or due to a lower proportion of the neutral lipids such as triglycerides. The highest concentrations of DDTs were measured in muscle and fat, with p,p'-DDE being the principal contributor and with a variable contribution of p,p'-DDD and p,p'-DDT. In liver, p,p'-DDD has a higher contribution to the sum DDTs, while in all analyzed livers, the concentration of p,p'-DDT was very low. beta-HCH was the most persistent HCH isomer in all tissues, accounting for 40-97% of sum HCHs. For all animals, the highest concentrations of beta-HCH and HCHs were found in liver, while the lowest HCH concentrations were measured in brain and spinal marrow. Additionally, the distribution of alpha-HCH enantiomers in the tissues was discussed. In all samples (except 2 brain samples), (+) alpha-HCH was depleted and (-) alpha-HCH was enantioenriched. Enantiomeric ratios in brain were the highest measured values between all organs. For all studied animals, ERs increased in the order fat < muscle < liver < brain.