نشریه علوم محیطی
سال هشتم شماره 4 (پیاپی 32، تابستان 1390)

The objective of this study is to develop a new process for the production of pulp using the wheat straw. Environmentally-friendly wheat straw pulp with potassium hydroxide was prepared، and their mechanical and optical properties were studied. Pulping tests were carried out varying active alkali (16، 18 and 20 wt %) and cooking time (60 and 90 min). Liquor-to-solid ratio، time to reach the maximum temperature and the cooking temperature were kept constant. The increase in active alkali significantly reduced the yield and kappa number of the pulp. Chemical pulps of 48. 71–53. 73% yield produced from the KOH pulping process exhibited acceptable papermaking properties comparable to those of soda pulp. Refining the pulps increased the tensile index، breaking length، and burst index of the handsheets. The tear index and brightness were lower for refined pulp compared with the unrefined one. The black liquor of this process can be utilized as a fertilizer for agricultural production.

The present study was undertaken with a view to choosing a macroeconomic policy for preventing soil erosion in Iran. In choosing the appropriate policy، this study not only calculated the environmental impacts of various policies، but also it analyzed their impacts on some important economic indices such as total real production، in a General Equilibrium framework. Results show that both the economic and environmental impacts of an Upland Food Production Tax are very favorable in comparison with a Lowland Food Production Subsidy. Finally، as a policy recommendation، it is suggested that regardless of any practical problems associated with either of the policies، the Upland Food Production Tax is potentially the appropriate policy to overcome the soil erosion of upland areas which are under cultivation by rain-fed crops.

Companies need to design engineering software to obtain emission limits before construction and commissioning the plants to control air pollutants. During the design of plants، all emissions should be studied and measured. Since some emissions are lighter or higher than air، there are different methods for their modeling. These models are used for reviewing the effect of gases on the environment and the best model is the one that can design an accident before dispersion. In this research three software packages، namely PHAST، CIRRUS and SHELL FRED، were compared with a newly-created software for measuring the ground level concentration of H2S and SO2. The software packages were based on the Gaussian model for point sources. In these models، for simplicity، some assumptions were made based on one point source above the ground. According to the results، the new software was similar to CIRRUS in D stability of the air that can be used instead.

Ignorance to the principals of sustainable development has affected mangrove forests due to development projects. In order to study the effects of reduction in tidal flooding on vegetative structure of mangrove forests in Nayband coastal national park، a survey was conducted using linear transect method. By comparing the structure of mangroves in the Nayband area with Mound protected area the amount of destruction in this area was studied. Linear transact was used to determine the structure of the mangrove forests in this area. 5 Stations were considered. From that four stations were located in Nayband national park and the last one was situated in Mound protected area as control. A quadrate sample plot with 100 m2 in each transect has been used as the measuring unit with random–systematic distribution. In each plot، the height and steed diameter of trees as well as the height and diameter of crowns were measured. Furthermore، 1 m2 micro plots were used to measure the quantity and height of aerial roots as well as number of seedlings. Results showed that the road construction in this protected area resulting in decrease of water streams in some parts which are the main factor for destruction of this worthy ecosystem. Increase of the number of dried trees، reduction of canopy and the number of aerial roots are main evidences to prove these claim. The green density of mangroves was reduced to 60 and 40 % in the stations 1 and 4 respectively. The canopy in these stations was 40 and 52% respectively; that makes a spare canopy of mangroves forests. There was no seedling in station 1. Therefore، more efforts are need to improve the mangrove vegetation in these stations with strengthening of tidal fluctuations.

The aims of our study were to compare the effectiveness of different nutrition systems and fungi Piriformospora indica on yield and the concentration of elements in shoot and grain of fennel (Foeniculum Valgare Mill). A field study was conducted in 2009 in the Tehran region and the type of design was a randomized complete block with a factorial arrangement and three replications. Five levels of manure (without organic manure، 100% cattle manure، 100% spent mushroom compost and 50% cattle manure with 50% spent mushroom compost and 100% N) along with two levels of inoculation and not-inoculation of the plant with Piriformospora indica. Results showed that different nutrition systems impacted significantly on yield، dry matter، harvest index and nitrogen concentration of plant and grain. The result also showed that fungi significantly affected all of the measured traits except for the potassium concentration of plant and grain. Also، the interaction effects of fungi ´ nutrition systems was not significant in all measured traits except the harvest index. The result showed that the highest (1559 kg/ha) and the least (632 kg/ha) grain yield was produced in chemical systems Piriformospora indica and fertilization systems respectively.

This research considers the determination of the preservation value of Gaz trees on the banks of Fahliyan River located in Rostam and Mamasani region and measures individuals willingness to pay (WTP) for the preservation of these trees using a contingent valuation method. A Logit model was used for measuring individuals WTP and the model indicators were estimated through maximum likelihood (ML). The results showed that 78.50/0 of individuals were willing to pay for preservation of these trees. The average amount of WTP for the annual preservation value of Gaz trees were calculated at 5540 Rials per month for each household. The annual preservation value was estimated 1650 million RLs. This value is an acceptable justification for politicians and decision makers to show more support to the quality and quantity of Gaz trees.

With urbanism and city development، the natural environments around cities change and lose their natural character. These natural landscapes، affected by city development and overuse for recreational purposes، gradually become destroyed. The main objective of this research is to preserve the natural landscapes near large cities، both to limit the city boundary and to create ecotourism sites with less interference in nature and creating the potential for people to enjoy and relax from these beautiful natural scenes. The Alborz hills are one of the natural resources in the north of Tehran. These highlands can provide many environmental and recreational services. District one of Tehran municipality is one of the northern areas of Tehran which has a rich potential for tourism and ecotourism sites. In this research، the foothills between Darabad valley and Jamshidieh Park were selected as forming part of a natural zone near Tehran which is affected by city growth as a case study. Then by using maps، aerial photography، satellite images and field visits، two walking trails were defined and located on the map. Finally four sites (stations) along these trails proposed and designed based on environmental studies such as topography، vegetation cover، water resources، erosion and landscape analysis.

The presence of organic chemical materials in surface water resources، besides having adverse effects on the consumer، reduces the desirability of aquatic fauna and even results in their complete annihilation. Determination of Diazinon residues in the Tajan River (TR) was traced in order to investigate the level of concentration of this pollutant from the agricultural activities around the river. This was accomplished by taking samples in 2008، starting in April at three-week intervals and continued up to October. After each sampling، the existing Diazinon concentration was determined in the laboratory using a high performance liquid chromatography (HPLC) instrument. The largest Diazinon concentration was 47 micrograms per liter found in June and at the third sampling station. Analysis of the results confirmed that the Diazinon concentration of Tajan River increases with the beginning agricultural activities in specific fields covered with rice. This Diazinon concentration appeared throughout summer at different concentrations. According to the criteria recommended by EPA for Diazinon pollutants to protect the river ecosystem، with a one-hour average concentration of 0. 17 µg/lit which is not exceeded more than once every three years (acute toxicity criteria)، it can be concluded that Diazinon concentration in the Tajan river affected agricultural activities and increased the risk to the river ecosystem.