The relationship between reserves of oil endowment and economic growth from the resource curse viewpoint: a case study of oil producing countries

This research investigated the effective economic growth determinants using a panel data set over the period 1995 to 2010 in oil-rich countries divided by the level of democracy into two groups: countries with low and high democracy. The result of OLS method rejects the curse hypothesis; however, TSLS method reveals the reserves of oil endowment has a negative effect on economic growth of low democracy countries and the curse hypothesis is approved

Can location of sample area and expert knowledge affect the results of geopedological approach in soil mapping?

Soil maps are used for different purposes like agriculture, natural resources, mining and engineering. Thus, their quality is a prerequisite for rational land use and soil management. New versions of soil surveys are used to increase the reliability of soil maps. Geopedology is a systematic approach of geomorphic analysis for soil mapping that construct field operation upon work mainly in a sample area and generalization of the results obtained from sample area to similar landforms in the region. The objective of this study is to determine the effect of location of sample area and expert knowledge on credibility of generalization the results of geopedological approach for similar landforms in south-east of Borujen area, Central Iran. After preparation of primitive interpretation map of the study area on air photos (1:20 000), considering different locations of Pi111 unit that encompasses the maximum space of the study area, the sample area was planed in three different locations. Then, a second-order soil survey was conducted and final soil map was prepared. Also, the idea of two different experts was considered to determine the amount of credibility of generalization the results of geopedological approach for the mentioned unit. Results showed that changing the location of sample area has taxonomic levels (order, subgroup and/or family) and map unit type (complex and consociation) differences in Pi111 unit. In spite of similarity the profiles selected by two experts, soil taxonomy of these profiles were different in comparison with representative pedons (at family level). Therefore, the use of landform phases is recommended to increase the accuracy of geopedological results

Evaluation of Soil Quality Using Labile Organic Carbon and Carbon Management Indices in Agricultural Lands of Neyriz, Fars Province

Introduction: Soil organic matter is considered as an indicator of soil quality, because of its role on the stability of soil structure, water holding capacity, microbial activity, storage and release of nutrients. Although changes and trends of organic matter are assessed on the basis of organic carbon, it responds slowly to changes of soil management. Therefore, identifying sensitive components of organic carbon such as carbon labile lead to better understanding of the effect of land use change and soil management on soil quality. The main components of sustainable agriculture in arid and semi-arid regions are the amount of water; and soil and water salinity. Water deficit and irrigation with saline water are important limiting factors for cropping and result in adverse effects on soil properties and soil quality. Soil carbon changes is a function of addition of plant debris and removal of it from soil by its decomposition. If the amount of organic carbon significantly reduced due to the degradation of the soil physical and chemical properties and soil quality, agricultural production will face serious problems. To this end, this study was done to evaluate soil quality using soil labile carbon and soil carbon management indices in some agricultural lands of Neyriz area, Fars province, Iran. Materials and Methods: Five fields were selected in two regions, Dehfazel and Tal-e-mahtabi, consisted of irrigated wheat and barley with different amount of irrigation water and water salinity levels. Three farms were located in Dehfazel and two farms in Tal-e-Mahtabi region. In each farm, three points were randomly selected and soil samples were collected from 0-40 cm of the surface layer. Plant samples were taken from a 1x1 square meter and grain crop yield was calculated per hectare. Water samples were obtained in each region from the wells at the last irrigation. Physical and chemical characteristics of the soil and water samples were determined. Soil labile carbon and carbon management indices also were calculated. In carbon management index calculation, a reference farm was chosen at the vicinity of two regions which were abandoned for years. Statistical analysis like analysis of variance and correlation coefficients was done using SPSS 16.0 software. Results and discussion: Results revealed that the highest crop yield (with the average of 5.7 tonh-1) was related to the farm which was irrigated with saline water (water EC 8.1 dSm-1) with enough water crop requirement. As this farm received the highest amount of water (with thw volume of 1039.5 mm), it seems that much more irrigation water probably provided the leaching fraction and prevented salt accumulation in the the root zone. Therefore, water salinity could not be a limiting factor for crop growth in this farm. This farm also had the highest content of organic carbon but it didn’t have the highest labile organic carbon and carbon management index (the value of 161.5). On the other hand, the farm containing the highest labile carbon and carbon management indices (the value of 284), didn’t have the highest crop yield (with the average of 2.6 tonha-1) although it has recieved enough amount of water as well as non-saline irrigation water (water EC 2.28 dSm-1). The more carbon management index represents the higher soil carbon lability and soil quality and it demonstrates that soil have better condition for living microorganisms. Therefore, it can be concluded from the results that the higher soil quality not necessarily resulted in higher crop yield. Many researchers reported that better soil properties are not always resulted in the higher productivity. Taking everything into account, carbon management index is not related to crop yield, but since it indirectly is related to microbial activity and calculated easily, it could be a useful indicator for rapid assessment of soil quality. Meanwhile, this indicator may be associated with qualitative properties of the crops such as grain protein, which is recommended for future investigations. Conclusion: Results showed that labile organic carbon is more sensitive to crop management than total organic carbon. Amount of irrigation water and its salinity can influence the labile organic carbon content and thus the soil quality even in the fields with the same crop yield and management. Although, a higher amount of carbon management index does not result in higher yield production, it may be associated with crop quality attributes. More investigation is needed to give better idea in this regard

Stand structure and spatial pattern of trees in mixed Hyrcanian Beech forests of Iran

Mixed beech forests (Fagus orientalis) are the most important forests with the highest degree of naturalness in Hyrcanian forest of Iran. These forests commonly dominate by shade tolerance species with irregular and uneven-aged stand structure. The aim of this study is to analyze the stand structure and spatial pattern in order to identify specific structural patterns. We studied the stand structure and spatial pattern of trees in mixed beech forest in the Shastkolate Educational Forest to examine the coexistence strategies of different species. Data was collected from a 16.9 ha permanent plot on a 406×416m quadrate area. We measured all trees exceeded than 7.5cm in diameter at breast height on permanent plot. The six main species were divided into two groups based on density and stand structure. Group A had higher density than group B, as well as reverse J shaped DBH distribution of live standing trees. Species in group A have clump spatial distribution pattern in all layers. However, clump intensity is more than in understory and size of patch clump was smaller in this group. This situation for group A may explaining by having numerous coppice, sucker and patch regeneration in the understory layer. Middlestory and understory stems of the six major tree species were patchily distributed throughout the plot. However, for Alder (Alnus subcordata) and Maple (Acer velutinum) common pattern in canopy layer was complete spatial randomness. The distributions of beech trees were negatively associated with other species. These results suggest species differences in favorable canopy condition

Toxicity and Origins of PAHs in Sediments of Shadegan Wetland, in Khuzestan Province, Iran

Background and purpose: Shadegan wetland as the largest wetland in Iran is constantly exposed to hydrocarbons entering through the main entrance of the lagoon including Jarahi River, outbursts of seasonal rivers from upstream, Persian Gulf tides from downstream, atmospheric deposition, and possible leaks from oil pipelines. The aim of this study was to investigate toxicity and identifying the sources and spatial distribution of polycyclic aromatic hydrocarbon (PAH) in surface sediments of the study area for its appropriate management. Materials and methods: Sediment samples were collected (in 2015) from 202 stations at the top 5 cm of the sediment according to a systematic-random sampling design. The concentrations of PAHs were analyzed by GC–MS. Results: The total PAHs (sum of 30 PAH compounds) ranged from 593.74 to 53393.86 ng/g dw. The results of diagnostic ratios indicated that the study area was highly contaminated by petrogenic hydrocarbon sources. The concentrations of PAHs in this research were substantially higher than those found in many other aquatic systems and significantly more than current sediment quality criteria (ERL). Conclusion: High levels of petrogenic contamination were found in sediments of Shadegan wetland. A vast majority of the study area (90%) is subjected to chronic pollution of oil contaminants that could adversely affect benthic biota

Pollution assessment and spatial distribution of trace elements in soils of Arak industrial area, Iran: Implications for human health

Emerging industrial hubs have resulted in soil and dust pollution by trace elements, being a potential source and pathway for human exposure to nearby cities. The aim of this study was to determine the spatial distribution, levels, sources and health risk assessment of metals and arsenic in soils of Arak industrial area, Iran. A total of 235 topsoil (0–5 cm) samples were collected from the vicinity of Arak, and the concentrations of As, Zn, Ni, Pb, Cu and Cd were 152, 104, 93, 38, 14 and 1.2 mg kg−1, respectively, and exceeded the background values, with the exception of Cu. Values of pollution indexes revealed that most of the soils are especially enriched by As and Cd. Multivariate statistical analysis showed that Pb and Zn originated from common anthropogenic sources related to industrialization and mining, whereas Cu and Ni are probably associated with geological sources. Cd was mainly derived from the input of agricultural and industrial activities, and As should be attributed to residues in mining. Spatial risk maps showed the high risk of trace elements pollution in the order of As (100%) > Cd (62%) > Ni (12%) > Pb (5%) > Zn (4%) > Cu (0%). The results of the noncarcinogenic risk assessment showed that chronic daily intake in children and adults for ingestion pathway was higher than for dermal contact and inhalation. Values of hazard index (HI) for trace elements were below the safe level (HI ≤ 1), indicating that no noncarcinogenic risk threaten children and adults. Likewise, the total carcinogenic risk of Cd in both groups is less than the EPA threshold (1 × 10−6), indicating a low carcinogenic risk, however As (1 × 10−6 to 1 × 10−4) indicates an acceptable risk.The authors gratefully acknowledge Shahrekord University (Fund no.: 122/701-2017) and Ministry of Science, Research and Technology (MSRT), Iran, (Fund no.: 97664654) for providing the financial support. They also thank the anonymous reviewers for their valuable and critical comments.Peer reviewe

Human health risk assessment of arsenic and trace metals in atmospheric dust of Arak industrial area, Iran

In order to investigate concentrations, variability, sources, and human health risk of trace elements, 38 atmospheric dust samples were collected around Arak industrial area. The average concentrations of Cd~Zn, As, and Pb were 3.3, 2.5, and 2.4 times higher than the corresponding geochemical background, respectively, while concentrations of Co, Cu, Ni, and Hg were lower. Based on geo-accumulation index (Igeo), trace elements were classified between practically uncontaminated to moderate contaminated levels. The potential risk (RI) map showed that about 86% of the study area for all trace elements was in the moderate risk class. According to the results of positive matrix factorization (PMF) model, four factors were extracted for trace elements, including industrial sources, natural sources, mining, and transportation, that contributed about 30, 27, 26, and 17% to pollution of the area, respectively. The carcinogenic risks for inhalation exposure to Cd, As, Ni, and Co were lower than the permissible risk limit than the EPA recommend (10−6), indicating an acceptable level of risk. Results of the health risk evaluation indicated that the non-carcinogenic health risk (i.e., hazard quotient, HQ) for children and adults decrease following: As > Pb > Ni > Zn > Cd > Cu > Co > Hg. When excluding As, the hazard index (HI) was lower than the safe level (HI < 1) for all the trace elements, whereas HQ values of As for children and adults were 17.1 and 1.6, respectively, indicating a potential risk for children. In sum, several remedial actions to eliminate or to reduce the dust pollution are urgently required in the industrial area of Arak.Peer reviewe