On marketable air-pollution permits: The case for a system of pollution offsets

After examining the properties of several alternative forms of marketable permit systems for the control of air pollution, this paper proposes a system of pollution offsets as the most promising approach. Under the pollution-offset scheme, sources of emissions are free to trade emissions permits subject to the constraint of no violations of the predetermined air-quality standard at any receptor point. The paper shows that the pollution-offset system has the capacity to achieve the predetermined standards of air quality at the minimum aggregate abatement cost, while making comparatively modest demands both on the sources and on the administering agency.     

Dynamic simulation of water depletion in the root zone

The joint effect of the distribution of the soil water potential and of the root mass in the crop root zone upon the water uptake by the crop is represented by a simple equation. This expression is used to join a layered crop canopy model for finding the evapotranspiration, as controlled by stomatal action and the weather, with a hydraulic flow model for the root zone and the underlying soil. The complete model is used for the calculation of the water extraction pattern and the changes, with time, of other plant and soil processes. A simulation of a 20-day drying period is performed, using S/360 CSMP, for a constant diurnal weather pattern, and for a fully developed sorghum crop. The results show that, after a few days of essentially constant water use by the crop, a monotonic decline sets in, that is principally attributable to the decrease in transpiration. For the entire drying period a substantial amount of water - about 30% of the total used - is contributed by upward flow into the root zone from the soil below. The results demonstrate the difficulty of quantitative definition of concepts such as “field capacity”, “wilting percentage”, and “available” or “extractable” water.     

Temporary natural resource cartels

We analyze the behavior of a nonrenewable resource cartel that anticipates being forced, at some date in the future, to break up into an oligopolistic market in which its members will then have to compete as rivals. Under reasonable assumptions about the value function of the individual firms in the oligopolistic equilibrium that follows the breakup, we show that the cartel will then produce more over the same interval of time than it would if there were no threat of dissolution, and that its rate of extraction is a decreasing function of the cartel's life; that there are circumstances under which the cartel will attach a negative marginal value to the resource stocks, in which case the rate of depletion will be increasing over time during the cartel phase; that, for a given date of dissolution, the equilibrium stocks allocated to the post-cartel phase will increase as a function of the total initial stocks, whereas those allocated to the cartel phase will increase at first, but begin decreasing beyond some level of the total initial stocks.     

硼配施多种微量元素对桉树生长的效应

针对广东省雷州半岛桉树人工林出现缺素生理病的现象,进行了桉树施硼及配施其它微量元素的田间试验,旨为桉树人工林持续发展提供依据。试验结果表明:(1)单施硼对刚果12号桉W5(Eucalyptus ABL12W5)和尾叶桉U6(Eucalyptus urophyllas U6)均有明显效果,但前者施硼的效果好于后者;(2)硼与铜、锌、铁、锰、钼等配施效果明显好于单施硼,但桉树不同树种对微量元素营养有一定的选择性;硼与铜、锌、铁、锰等配施可使刚果12W5大幅增产,而硼与钼配施对尾叶桉U6生长效应显著;(3)缺硼是诱发雷州半岛桉树缺素生理病的重要原因,施用硼可有效消除雷州半岛桉树垂稍病。     

Ungulate Reintroductions: Experiences with the Takhi or Przewalski Horse (Equus ferus przewalskii) in Mongolia

Experiences with the reintroduction of the takhi, or Przewalski horse ( Equus ferus przewalskii , in Mongolia can serve as valuable lessons for reintroduction of ungulates in general. We discuss the present taxonomic, historical, and biological evidence and conclude that the takhi should be viewed as a typical steppe herbivore. Its last refuge, the Dzungarian Gobi, should therefore be seen as a marginal habitat because it consists mainly of desert and semidesert. Since 1992 two reintroduction projects have been in the acclimatization phase in Mongolia. Despite promising developments, problems with cooperation, management, habitat choice, insufficient knowledge of the ethology of the species, and current land use within the different project areas could jeopardize the successful reintroduction of takhi. We review the conditions required for a potentially successful ungulate reintroduction. The planning of a reintroduction within the framework of safeguarding an entire ecosystem with an integrated management plan appears essential. Each potential reintroduction site should be assessed thoroughly for its suitability, including size, habitat types, current land use, socioeconomics, legislation, and potential problems. Each site should be provided with one or more acclimatization facilities to harbor genetically and physically healthy, socially adapted animals in biologically sound groups. An organization structure should be established for each reintroduction site. Its objective should be to develop an effective management plan and to carefully monitor the population and its surrounding ecosystem. Special attention should be given to local socioeconomic situations, community participation, and training of staff for management, research, and ranger and warden activities.     

Pattern of planktonic bioluminescence in the northern Sargasso Sea: Seasonal and vertical distribution

The vertical structure of bioluminescence potential (BPOT) and flash density (FD) were measured on five cruises to the northern Sargasso Sea in 1987 and 1988. Depth-integrated (0 to 150 m) BPOT did not vary seasonally, remaining within the range 9 to 15 × 10¹⁵ photons m^–2 in all months sampled. Conversely, depth-integrated FD was significantly higher (> 2 × 10⁵ flashes m^–2) during winter (November and March) than during summer (< 9 × 10⁴ flashes m^–2 in May and August). The vertical patterns of BPOT and FD were well correlated within a single profile, more highly so in summer than in winter. Despite intracruise variability in the vertical pattern of BPOT and FD, there were clear summer-winter differences in the vertical distribution of BPOT and FD. During winter, BPOT and FD were maximal and relatively uniform throughout the surface mixed layer; for example in November they declined sharply within the thermocline at 130 to 150 m. During summer, BPOT and FD were greatest (12 to 25 × 10¹³ photons m^–3 and 600 to 1 200 flashes m^–3, respectively) at subsurface depths. Commonly in summer, the upper depth limit of high BPOT and FD occurred at the base of the surface mixed layer (10 to 40 m) and the lower depth limit was located at the base of the subsurface fluorescence maximum (usually at 100 to 120 m).     

Seasonal exposures to triazine and other pesticides in surface waters in the western Highveld corn-production region in South Africa

The objective of this study was to characterize concentrations of atrazine, terbuthylazine, and other pesticides in amphibian habitats in surface waters of a corn-production area of the western Highveld region (North-West Province) of South Africa. The study was conducted from November 2001 to June 2002, coinciding with the corn-production season. Pesticide residues were measured at regular intervals in surface water from eight ponds, three in a non-corn-growing area (NCGA) and five within the corn-growing area (CGA). Measured atrazine concentrations differed significantly among sites and between samples. In the five CGA sites, the maximum atrazine concentrations measured during the study ranged from 1.2 to 9.3 microg/L. Although no atrazine was recorded as being applied in the catchment of the three NCGA sites, maximum concentrations from 0.39 to 0.84 microg/L were measured during the study, possibly as a result of atmospheric transport. Maximum measured concentrations of terbuthylazine ranged from 1.22 to 2.1 microg/L in the NCGA sites and from 1.04 to 4.1 microg/L in the CGA sites. The source of terbuthylazine in the NCGA sites may have been in use other than in corn. The triazine degradation products, deisopropylatrazine (DIA) and deethylatrazine (DEA) and diaminochlorotriazine (DACT) were also found in water from both the CGA and NCGA sites. Concentrations of DIA were > or = 1 microg/L throughout the season, while DEA concentrations were mostly <0.5 microg/L before planting but increased after planting and application of herbicides to concentrations >2 microg/L in some locations. Concentrations of DACT were highly variable (LOD to 8 microg/L) both before and after planting and application, suggesting that they resulted from historical use of triazines in the area. Other herbicides such as simazine and acetochlor were only detected infrequently and pesticides such as S-metolachlor, cypermethrin, monocrotophos, and terbuphos, known to be used in the CGA, were not detected in any of the samples. Because of dilution by higher than normal rainfall in the study period, these concentrations may not be predictive of those in years of normal rainfall.     

Evaluation of quick tests for phosphorus determination in dairy manures

Nutrients in animal manure are valuable inputs in agronomic crop production. Rapid and timely information about manure nutrient content are needed to minimize the risks of phosphorus (P) over-application and losses of dissolved P (DP) in runoff from fields treated with manure. We evaluated the suitability of a commercial hand-held reflectometer, a hydrometer, and an electrical conductivity (EC) meter for determining DP and total P (TP) in dairy manures. Bulk samples (n = 107) collected from farms across CT, MD, NY, PA, and VA were highly variable in total solids (TS) concentration, ranging from 11 to 213gL(-1), in suspensions' pH (6.3-9.2), and EC (6.2-53.3 dS m(-1)). Manure DP concentrations measured using the RQFlex reflectometer (RQFlex-DP(s)) were related to molybdate-reactive P (MRP(s)) concentrations as follows: RQFlex-DP(s) = 0.471 x MRP(s) + 1102 (r2 = 0.29). Inclusion of pH and squared-pH terms improved the prediction of manure DP from RQFlex results (r2 = 0.66). Excluding five outlier samples that had pH < or = 6.9 the coefficient of determination (r2) for the MRP(s) and RQFlex-DP(s) relationship was 0.83 for 95% of the samples. Manure TS were related to hydrometer specific gravity readings (r2 = 0.53) that were in turn related to TP (r2 = 0.34), but not to either RQFlex-DP or MRP. Relationships between suspensions' EC and DP or TP were non-significant. Therefore, the RQFlex method is the only viable option for on-site quick estimates of DP that can be made more robust when complemented with TS and pH measurements. The DP quick test can provide near real-time information on soluble manure nutrient content across a wide range of handling and storage conditions on dairy farms and quick estimates of potential soluble P losses in runoff following land applications of manure.     

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin or 2,2',4,4',5,5'-hexachlorobiphenyl on vitamin K-dependent blood coagulation in male and female WAG/Rij-rats

Newborns are susceptible to hemorrhages (hemorrhagic disease of the newborn or HDN) due to vitamin K deficiency. Induction of cytochrome P450 in the fetal liver by maternal anticonvulsant therapy such as phenobarbital or phenytoin is considered to be a major cause. An observed increase in late hemorrhagic disease (LHD) in breast fed neonates gave rise to the hypothesis that PCBs and dioxins, P450-inducing contaminants present in human milk, might effect vitamin K-dependent blood coagulation. This hypothesis was studied in rats. Administration of a single oral dose of 0.003, 0.03, 0.3, 3 or 30 nmol 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) per kg bodyweight or 0.75, 4, 20, 100 or 500 micromol 2,2',4,4',5,5'-hexachlorobiphenyl/kg bw (HxCB) to female and male rats resulted in dose-related reductions of the vitamin K-dependent coagulation factor VII. The highest factor VII reduction in female rats was 44%, observed after TCDD exposure. The Lowest Observed Adverse Effect Level (LOAEL) of TCDD on female factor VII levels was 0.3 nmol/kg bw (96 ng/kg). There was a significant inverse correlation between Factor VII levels and induction of hepatic ethoxyresorufin O-deethylating (EROD) activity, reflecting CYP1A1, and total P450 content. HxCB had no effect on female coagulation factors. In contrast, in male rats only exposure to HxCB, which induces mainly CYP2B1 and 2B2, decreased both coagulation factors dramatically up to 88%. The LOAEL of HxCB on factor VII in male rats was 100 micromol/kg bw (36 mg/kg). In general, effects on coagulation factors in male rats exceeded those in females. In addition, sex-dependent differences of TCDD and HxCB were observed on the hepatic vitamin K cycle enzyme activities in female and male rats. Vitamin K-dependent (gamma-glutamyl carboxylase activity was mainly induced in female rats; 2.3-fold in the highest dose group of TCDD. In male rats only vitamin K 2,3-epoxide reductase (KO-reductase) activity was induced 1.7-fold by the highest dose of HxCB. KO-reductase activity in female rats was also increased by TCDD, however, less pronounced than the carboxylase activity. Concluding, the hepatic vitamin K cycle still functions and is not blocked by TCDD or HxCB, thus explaining the observed reduction in factor VII. Finally, the possible role of P450 in vitamin K deficiency is discussed. Based on these results it is suggested to investigate the possible role of PCBs and dioxin-like compounds in LHD in more detail.     

Scenarios of animal waste production and fertilizer use and associated ammonia emission for the developing countries

Livestock production and the use of synthetic fertilizer are responsible for about half of the global emission of NH₃. Depending on the animal category between 10 and 36% of the N in animal excreta is lost as NH₃. The current annual NH₃ emission in developing countries of 15 million ton N accounts for of the global emission from animal excreta. In addition, 7.2 million tons NH₃N of synthetic N fertilizers are lost as NH₃ in developing countries. This is 80% of the global NH₃ emission from synthetic fertilizer's use. Along with human population increase and economic growth, livestock production in developing countries may even increase by a factor of 3 between now and 2025. The net result of rapid increase of livestock production combined with higher efficiency is an increase in NH₃ emissions of only 60% from 15 to 24 million tons NH₃N between 1990 and 2025 in developing countries. Livestock production is an important consumer of feedstuffs, mainly cereals, thereby inducing additional demand for synthetic fertilizers. Despite the projected major increase of synthetic fertilizer use from 42 to 106 million ton N between 1990 and 2025, the NH₃ loss in developing countries may decrease if a shift towards other fertilizer types, that are less vulnerable to NH₃ volatilization, is realized. According to the scenario, the total emission of NH₃ associated with food production in developing countries will increase from 22 to 30 million ton N yr⁻¹ between 1990 and 2025. Although the NH₃ emission increases more slowly than food production, in particular, animal production may show geographic concentration in certain regions, which may lead to high local emission densities and associated environmental problems.