Primary Natural Resources Research Articles

Estimation of carbon stocks in the areas of a seasonally dry tropical forest in the Brazilian semi-arid region

In addition to its ecological importance, the Caatinga biome, one of the most extensive seasonally dry tropical forests (SDTF) in the world, has a relevant socioeconomic role as it is used as a primary natural resource by local communities. However, inadequate ecosystem management practices have resulted in gradual loss of natural vegetation in this ecosystem. Carbon stock estimation is a parameter that can contribute as a support tool for managing and maintaining the few remaining natural vegetated areas. In this study, we calibrated and validated the CENTURY model to simulate carbon stocks in areas of the Caatinga, in the state of Pernambuco, and compared the predictive capacity of the CENTURY model with available estimates. In the validation dataset, the average for biomass stocks was 33.1 Mg C ha−1, this value is close to those observed in the literature for the region. The model also performed well when estimating carbon stocks in the soil (r2 = 0.79, p = 0.017). Ecosystem modeling combined with Geographic Information Systems (GIS) is a promising tool for estimating carbon stocks in the Caatinga, where field sampling campaigns are generally expensive and have scarce research funding opportunities. Furthermore, it also allows the evaluation of the effect of environmental changes on C stocks in long-term studies, which is essential for creating and implementing public policies to mitigate and adapt to the impacts of climate change on the ecosystem. However, additional efforts are needed to improve C estimates, especially in areas with a strongly negative water balance.

Aspects of Nickel, Cobalt and Lithium, the Three Key Elements for Li-Ion Batteries: An Overview on Resources, Demands, and Production.

With the booming of renewable clean energies towards reducing carbon emission, demands for lithium-ion batteries (LIBs) in applications to transportation vehicles and power stations are increasing exponentially. As a consequence, great pressures have been posed on the technological development and production of valuable elements key to LIBs, in addition to concerns about depletion of natural resources, environmental impacts, and management of waste batteries. In this paper, we compile recent information on lithium, nickel, and cobalt, the three most crucial elements utilized in LIBs, in terms of demands, current identified terrestrial resources, extraction technologies from primary natural resources and waste. Most nickel and cobalt are currently produced from high-grade sulfide ores via a pyrometallurgical approach. Increased demands have stimulated production of Ni and Co from low-grade laterites, which is commonly performed through the hydrometallurgical process. Most lithium exists in brines and is extracted via evaporation-precipitation in common industrial practice. It is noteworthy that at present, the pyrometallurgical process is energy-intensive and polluting in terms of gas emissions. Hydrometallurgical processes utilize large amounts of alkaline or acidic media in combination with reducing agents, generating hazardous waste streams. Traditional evaporation-precipitation consumes time, water, and land. Extraction of these elements from deep seas and recycling from waste are emerging as technologies. Advanced energy-saving and environmentally friendly processes are under extensive research and development and are crucial in the process of renewable clean energy implementation.

Sustainability of the use of critical raw materials in electric vehicle batteries: A transdisciplinary review

The expected growth of electric mobility will have major sustainability implications in societies across the globe due to a global reliance on primary natural resources and the uneven distribution of benefits and impacts. There has been a call for comprehensive assessments that account for the complex causalities between technological, environmental, social, economic, and political aspects of electric mobility. We present a literature review examining the interconnections between aspects of sustainability in the use of critical materials in electric vehicle batteries. With a holistic review of social sciences, materials science, environmental policy, and innovation management literatures, five domains of sustainability tensions were identified: 1) resource sufficiency, 2) geographical distribution and global value chains, 3) regulation and policies, 4) circular economy, and 5) emerging battery technologies. The framework explicates the wickedness and complex causalities involved in the interdependencies of multiple sustainability dimensions and the related tensions. This study extends the examination to cover political aspects and adds to techno-industrial research on battery materials, supply chains and industrial policies and land use, electricity consumption and governance in EV battery production. This study proposes pathways forward that consider various sustainability interdependencies.

“Return us where we can hunt and gather”: hierarchies and social structures that sustain exclusion of San minority in Zimbabwe

PurposeThe paper seeks to analyse the constellation of social structures, administrative institutions and hierarchies that sustain the exclusion of the San minority group in Zimbabwe, with a particular focus on how the European expansion in the eighteenth century, the modern state and private property owners have colluded to perpetuate exclusion from accessing forest as their natural habitat. The purpose of this paper is to therefore highlight the various abuses, including those social, administrative legislative frameworks that discriminate against the San minority and it advocates for actions the right to consultation and the right to free, prior and informed consent to proposed developments.Design/methodology/approachThrough the modern ethnographic approach, data generation was guided by the principles of indigenous and decolonising research methodologies, which place emphasis on the importance of San people telling their own stories thereby shifting the power of a researcher to the indigenous participants. This is a qualitative study that gives prominence to the descriptions of experiences (phenomenology) and interpretations (hermeneutic) of their survival. The paper employed cultural ecology theoretical framework as a lens through which to see the San’s exclusion from forest resources and how this has tragically shifted their egalitarian lifestyle characterised by reciprocity, sharing and levelling to adaptation to the unfamiliar sedentary farming practices.FindingsThe technical implementation of forest boundary demarcation and forcing the San to join sedentary farming form part of the state’s territorialisation that excludes, restricts and disrupts the San minority from accessing forest products. The treatment of the minority group reveals not only the enormous authority of the state to transfer alienation to individuals and companies but also to legitimise the exclusion by establishing laws and policies that safeguard the interests of those favoured by the state. The San, who are already overly dominated by the social administrative structures of the Ndebele and Kalanga tribes, lack systematic and organised responses to their marginalisation.Originality/valueThe San community in Zimbabwe is under-researched and under-theorised particularly in relation to how historically formed postcolonial hierarchies of exclusion and marginalisation manifest themselves in contemporary resource governance. Less is known about how those that are powerful – government officials, private property owners and Kalanga/Ndebele tribes benefit more from the environmental resources than the powerless minority San, whose livelihoods depend on the primary natural resources. The unequal power relations have been demonstrated by the evictions of the minority from wildlife areas that were converted into game parks. The study reveals how indigenous San not only resist exclusion but also develop adaptable strategies through negotiations to improve their situation with social and administrative institutions.

The prospects of intercropping of brinjal (Solanum melongena L.) with other vegetables on sorjan system in vulnerable southern coastal saline and non-saline areas of Bangladesh

The demand for food in Bangladesh is increasing due to the increasing population. Land is the primary natural resource that affords habitat and sustenance for living beings. In Bangladesh, the coastal areas cover an area of 47,201 km2 or 32 % of the total land under 19 districts of Bangladesh. The coastal southern saline and non-saline areas are vulnerable to water logging conditions and farmers cannot grow any crops except dry season (rabi). However, in some areas, farmers are trying to use their indigenous technologies to combat natural disasters to ensure food security. For example, floating, sorjan or raised bed systems are potential and farmers are practicing in these areas. Among these techniques, the sorjan bed system is one of the potential techniques that is extensively used in southern Bangladesh, particularly water logging conditions to improve food security. To enhance the production and make land cultivation profitable, the experiments were carried out at the farmers’ fields under the sorjan system in consecutive two growing seasons. The sole crop was brinjal (cv. BARI Begun-12), BARI Lalshak-1 (cv. Red amaranth), BARI Dhania-1 (cv. Coriander leaf), Cauliflower (cv. Cold queen), Cabbage (cv. Equatoria) and Knol Khol were utilized as intercropping with brinjal. The treatments were i) Sole brinjal, ii) Brinjal + Red amaranth, iii) Brinjal + Coriander leaf, iv) Brinjal + Cauliflower, v) Brinjal + Cabbage, and vi) Brinjal +. 24-day-old seedlings of the BARI Begun-12 grown in a nursery bed were transferred to the plots where the seeds of Red amaranth and Coriander leaf were directly sown. However, the seedlings of Cauliflower, Cabbage, and Knol Khol were also transplanted to the field after one week of transplanting brinjal. The results exposed that sole crops had the highest results in terms of days to flowering, days to first fruit set, days to first harvesting, leaf area, fruit length, fruit breadth, single fruit weight, fruits plant−1, fruit yield, TSS %, and dry matter %. In both years, brinjal exhibited the highest yield as the sole crop compared to intercropping. 48.12 t/ha and 46.27 t/ha in the first and second cropping seasons, respectively. In the first cropping season, Red amaranth, Coriander leaf, Cauliflower, Cabbage, and Knol Khol performed with a yield of 10.12, 7.23, 23.14, 22.87, and 9.05 t/ha. During the second cropping season, the same crops exhibited a yield of 10.05, 7.01, 23.09, 22.68, and 9.98 t/ha. The highest land equivalent ratio, gross return, net return, and BCR were obtained from brinjal-cauliflower intercropping, which was 1.74, 1049300 BDT, 553820 BDT, and 2.12, respectively, in the 2021–2022 cropping season and 1.78, 1057900 BDT, 562010 BDT, and 2.13, respectively, in the next season in 2022–2023. This intercropping approach resulted in a higher land equivalent ratio, net return, and benefit-cost ratio of 1.76, 557915 BDT, and 2.125, respectively, over the average of two successive cropping seasons.

ИССЛЕДОВАНИЕ СТРУКТУРООБРАЗОВАНИЯ ВЯЖУЩЕЙ СИСТЕМЫ НА ОСНОВЕ ТЕРМИЧЕСКИ АКТИВИРОВАННОЙ КЕРАМЗИТОВОЙ ПЫЛИ

The production of Portland cement is associated with a high consumption of mineral raw materials and significant emissions of carbon dioxide into the atmosphere. Therefore, the partial replacement of cement with technogenic mineral additive in cement compositions is a rational way of utilizing production waste. Besides, the use of industrial waste products as mineral additives allows solving environment problems and reducing the consumption of primary natural resources.
 This paper presents the study on the hydraulic activity of thermally activated expanded clay dust used as an active mineral additive in cement compositions. Expanded clay dust is an industrial waste formed during the production of ceramsite gravel, and captured in the dust cleaning systems of kilns: dust chambers, cyclones, filters.
 A comprehensive study of the composition, containing expanded clay dust and water, was carried out using the IR spectral analysis, differential scanning calorimetry and scanning electron microscopy with X-ray microanalysis.
 It was established that the strength of baked samples increased by 80% after immersion in water. The main hydration products of baked expanded clay dust are three types of compounds - fibrous crystals of calcium hydrosulfoaluminate, calcium hydroaluminates in the form of cruciform twins, amorphized spherulite-like formations based on low-base calcium silicate hydrates.

Review on heavy metal contaminants in freshwater fish in South India: current situation and future perspective.

The primary natural resource we use in our daily lives for a variety of activities is freshwater for drinking and various developmental goals. Furthermore, the pace of human population increase worldwide is rising rapidly and has a great impact on the Earth's natural resources. Natural water quality has diminished owing to various anthropogenic activities. Water is crucial to the life cycle. On the other hand, chemical and agricultural industries pollute heavy metals. Acute and chronic diseases caused by heavy metals, such as slow metabolism and damage to the gills and epithelial layer of fish species, are divided into two categories. Pollutants can also harm liver tissues and result in ulceration as well as diseases such as fin rot, tail rot, and gill disease. The most prevalent heavy metals are As, Cr, Pb, and Hg, which are systemic toxicants that affect human health. These metals are categorized as carcinogens by the US Environmental Protection Agency and the worldwide agency for cancer research because they cause organ damage even at low exposure levels. The focus of the current study is to review various freshwater sources of heavy metal pollution.

Dynamic regime differences in the market behavior of primary natural resources in response to geopolitical risk and economic policy uncertainty

The study explores the dynamic effects of geopolitical risks and economic policy uncertainties on oil and natural gas prices in the US market's less volatile and highly volatile regimes, employing Markov regime-switching dynamic regression models (MS-DR) with monthly data from January 2000 to November 2022. Our empirical results demonstrate that a positive shock in the geopolitical risk of the USA (GPR_US) causes an increase in the growth rate of the prices of WTI at the high volatile periods (regime 1), and its one-period lagged effects are negative at time t in the less volatile periods (regime 0), and it cumulatively causes an increase in WTI price. GPR_US and one lagged effect negatively and positively natural gas prices (NGAS) at both regimes. respectively, where the dynamic cumulative impact of GPR_US causes NGAS to increase. World geopolitical risks (GPR) lead to an increase in WTI and natural gas prices. Furthermore, US economic policy exerts a reduction in WTI price at both less and highly volatile regimes, and its lag influences are positive at both regimes, where it cumulatively causes a decrease in WTI price. In a similar manner, global economic policy uncertainty also reduces WTI. US economic policy and its lag effects exhibit an increase and decrease in NGAS prices in the high volatile regime but exhibited a cumulatively positive response to shock in economic policy uncertainty. Global economic policy uncertainty causes nature gas prices to go up. Hence, geopolitical risks and economic policy uncertainty might have a complex impact on the prices of natural resources. It depends on the specific circumstances and the supply-demand dynamics in the market. Our findings offer insightful implications for economic agents.

Assessment of the Biyadh groundwater quality and geochemical process in Saudi Arabia using statistical, modelling, and WQI methods

This research aimed to understand the variations in the groundwater quality and hydrochemical processes in the Biyadh aquifers in central Saudi Arabia. The Biyadh Aquifer in the Riyadh area is the primary natural water resource for Wadi Sahba and Wasia Well Fields. The present study collected thirty groundwater samples from the Biyadh aquifer in the outcrop and confined parts. The samples were evaluated by multivariate statistical methods and hydrochemical modelling to understand the geochemical processes that control the groundwater. Also, it used various indexes to find the groundwater's suitability for drinking, agricultural, and industrial purposes. The analysis revealed a general evolution in groundwater quality as groundwater flowed east and northeast. The TDS increases from 1730 mg/l in WS to 2370 mg/l in WWF. The groundwater facies developed from Ca-Mg-SO4-Cl to Ca-Na-Mg-SO4-Cl in WS and ended with Ca-Na-SO4-Cl in WWF. Applying Pearson's correlation matrix, cluster analyses, and factor analyses indicate that the ions significantly influence groundwater mineralization. The geochemical modelling revealed that the dissolution of the calcite, halite, anhydrite, and gypsum minerals increases with the direction of groundwater flow. In addition, the agriculture activities in Wadi Sahba mixed with irrigation return water to groundwater and increase nitrate (NO3) concentration. Biyadh groundwater has a better quality for drinking in the confined aquifer than in the unconfined aquifer, and both areas are suitable for irrigation. The TH indicates that the groundwater becomes more suitable for industrial purposes as it flows toward the confined part of the aquifer.

Comparative analysis of machine learning techniques for so2 prediction modelling

Sulphur dioxide (SO2) is produced both naturally and by human activity. The primary natural resource is derived from volcanoes. The burning of fossil fuels is the primary anthropogenic source (especially coal and diesel). Therefore, a reliable and accurate predicting method is essential for an early warning system for SO2 atmospheric concentration. There are still limited studies in Malaysia that use machine learning methods to predict SO2 concentrations. With the aid of machine learning, this study seeks to develop and predict future SO2 concentrations for the next day using the maximum daily data from Klang, Selangor. RapidMiner Studio is the data mining tool used for this research work. Based on the results, it showed that the SVM model was the best guide to be used compared with the other five models (GLM, DL, DT, GBT, and RF). The performance indicators showed that the SVM model was adequate for the next day’s prediction (R2 = 0.77, SE = 8.26, REL = 18.69%, AE = 1.46, and RMSE = 2.82). The developed model in this research can be used by Malaysian authorities as a public health protection measure to give Malaysians an early warning about the problem of air pollution. The goal of predictive modelling is to make a reasonable prediction of the variable of interest, and frequently, to determine how much the independent variable contributed to the dependent variable. The results also showed that the previous SO2 concentrations were one of the most influential parameters used to predict the future SO2 concentrations.

Natural Capital and Its Services in the Caatinga Phytogeographic Domain

A new millennium has begun, and a new paradigm in exploitation of natural resources to generate products has emerged. In this sense, a model in line with local environmental reality and based on the sustainable development goals (SDG) proposed by the UN is required. The document addresses the suitability of natural capitals in the Caatinga phytogeographic domain (CPD) for generating products, encompassing primary (solar energy and rainfall) and secondary (soil and vegetation) natural resources. These resources have well-defined scarcity (water, soil, and vegetation) and abundance (solar radiation) characteristics. Water is scarce due to uncertain rainfall and frequent droughts. Due to their fragility, soils, when shallow and/or with a low organic matter content, are susceptible to erosion and salinization. In turn, vegetation is scarce due to low potential for biomass production (50% of the area has a biomass production below 2 Mg ha-1. As for solar energy, there is no uncertainty regarding its occurrence in the CPD. Moreover, the region has the highest solar radiation intensities in Brazil, with daily averages ranging from 4.8 to 6.0 Kwh m-2 within a year. Therefore, a new model must be adopted, in which socioeconomic development is based on the potential of local natural resources. In short, abundant resources should be prioritized over scarce ones. Furthermore, exploitation must be democratized and not only in the hands of few privileged individuals

Dynamics of Reservoir Environment Carrying Capacity (Case of Kedungombo Reservoir, Central Java, Indonesia)

The development of dams or reservoirs requires continuous attention. The dynamics of rain as the primary natural resource and the water utilization may change from the design. Climate change is thought to have caused changes in reservoir inflow patterns where the patterns may change throughout the service life of the reservoir. The way of the utilization of catchment areas and reservoir inundation is also very dynamic, along with the dynamics of water demand which is generally aimed at obtaining better human welfare. At the same time, such activities may affect the quality of the reservoir waters, followed by disturbances in the water utilization for various purposes. This paper presents the results of evaluating the carrying capacity of the reservoir environment based on the data obtained from reservoir sedimentation and water monitoring of Kedungombo Reservoir. The adopted method of the environmental carrying capacity of the Kedungombo Reservoir considers the four environment-related carrying capacities, i.e., reservoir sedimentation, water utilization, recreation, and aquaculture. The term overall carrying capacity is introduced, adopting three approximations of weighting factor α of the four parameters. The analysis results show a promising method to evaluate the reservoir environment carrying capacity that could be dynamics during its service life.

ВИКОРИСТАННЯ ВІДХОДІВ СКЛОБОЮ В ДОРОЖНЬОМУ БУДІВНИЦТВІ

. One of the perspective directions of today that reduce the negative human-made pressure on the environment and the population in the implementation of construction and economic activities is the creation of resource-saving technologies that use secondary raw-materials instead of primary, which reduces the disposal of unused waste in the resource cycle, while reducing the use of primary natural resources. The possibility of using glass waste, the bulk of which is cullet, in road construction is considered. The results of researches are presented and it is shown that for performance of road-building works at the device of a design of road clothes, slag can be applied practically in all its layers.

Chicoric Acid: Natural Occurrence, Chemical Synthesis, Biosynthesis, and Their Bioactive Effects.

Chicoric acid has been widely used in food, medicine, animal husbandry, and other commercial products because of its significant pharmacological activities. However, the shortage of chicoric acid limits its further development and utilization. Currently, Echinacea purpurea (L.) Moench serves as the primary natural resource of chicoric acid, while other sources of it are poorly known. Extracting chicoric acid from plants is the most common approach. Meanwhile, chicoric acid levels vary in different plants as well as in the same plant from different areas and different medicinal parts, and different extraction methods. We comprehensively reviewed the information regarding the sources of chicoric acid from plant extracts, its chemical synthesis, biosynthesis, and bioactive effects.

Analysis of oil extractivism in Mexico and industry perspectives

The extractivism is an economic growth model based on the exploitation of primary natural resources, little transformed, including oil, to be sold on the world market. Several countries, including Mexico, were inserted into an extractivist model, to obtain the highest possible income, through which their industrialization and development were financed; on the other hand, these resources have also been used to pay for growing public spending. The objective of this research work is to determine the impact of oil extractivism on the economic growth of Mexico. For which an econometric model was developed, by ordinary least squares, analyzing the period of time 1990-2020. The results obtained show negative effects associated with a high dependence on public finances toward oil extractivism, in addition, derived from the lack of transformation and improvements of the Mexican extractivism model, negative impacts are generated in the economy that, if not addressed, can trigger a domino effect with greater losses for the oil sector, which could lead to increasing the country risk, an aggravating the economic and social situation of the country in the medium term.

Additive economy and new horizons of innovative business development

The disruptive technologies and cyber-physical production systems are important factors that bring transformations to socio-economic formations. The paper aims to formulate the content, key directions, positive and negative effects of additive economy (AE) in the current transition phase to Industry 4.0. The research method is based on the analysis of structural links in socio-economic systems, where the additive economy potential is realized. The additive economy is treated as a new approach to production technological aspect based on the additive principle of manufacturing and aimed at minimizing the use of primary natural resources for dematerialization of social production. AE is the antithesis of the subtractive economy, which dominates today and uses only a tiny proportion of extracted natural resources. Among the positive effects of AE, there are the reduction in energy intensity of products, dematerialization of production, solidarity of society, economic systems sustainability, and intellectualization of technologies and materials. Among the negative expectations of AE, there are increased information vulnerability of production, risk of losing control over cyber-physical systems, expanding the unification of individuals, and increasing psychological stress. The additive economy is more sustainable than the subtractive economy since it does not require extra components to the production spheres, reduces the resource scarcity, and could satisfy more economic agents’ needs. Therefore, improved production efficiency due to AE promises economic growth acceleration, environmental burden and social risk reduction. Acknowledgment The publication was prepared in the framework of the research projects “Sustainable development and resource security: from disruptive technologies to digital transformation of Ukrainian economy” (№ 0121U100470); Fundamental bases of the phase transition to an additive economy: from disruptive technologies to institutional sociologization of decisions (No. 0121U109557).

On the Program of Integrated Use of Primary Natural Resources

On the Program of Integrated Use of Primary Natural Resources

Neither prepared nor transformed: Institutional responses to unconventional oil and gas development in Australian and Canadian communities

Resource dependent regions in Australia, Canada, and in other industrialized areas have experienced rapid change due to forces of both political and economic restructuring over the past three decades. Policy and program responses by senior levels of government to these accelerating processes of change have too often only exacerbated the negative impacts of major resource exploitation. As a result, rural and small-town places dependent upon primary industries and natural resource sectors continue to struggle to find traction in a new economy marked by the vagaries of demographic, economic, social, cultural, political, and environmental change. In this paper, we explore these resource economy and institutional dynamics within the context of unconventional oil and gas development (UOGD). Our comparative case context includes the Surat Basin in eastern Australia and the Peace River region in northeastern British Columbia, Canada. Both regions have significant recent experience with UOGD. The paper draws upon staples theory and evolutionary economic geography to frame the dynamics of truncated development patterns and the prospects for path variation. Despite the well-known negative impacts and disruptions associated with major resource projects, we make three inter-related arguments challenging the efficacy of senior government responses to the community and regional impacts of UOGD. These are that senior governments: 1) react too slowly in their mitigation responses; 2) are generally dragged into action by local opposition to construct institutional and redistributive funding measures to compensate for local disruption, that; 3) ultimately fall short in terms of offering any kind of strategic, post-resource boom transformational potential to restore or redirect the economic future of resource regions.

Circular economy in agricultural sector

The goal is to provide a conceptual framework for a gradual transition to a circular economy through the analysis of authoritative literature sources. Methods are based on the principles of system-structural analysis, scientific analysis and synthesis, and logical explanation and description of the problem are also presented. For various solutions, appropriate qualitative and quantitative research methods were used: analytical, synthetic, logical, etc. Outcomes – the ways to increase resource efficiency by minimizing the use of primary natural resources (e.g. water, electricity), reducing pollution by synthetic fertilizers, and maximizing the use of biomaterials (e.g. agricultural waste) and treated wastewater, thus contributing to a smooth transition to the closed cycle economy in agricultural industry are presented. Taking into account the importance of the circular economy, the importance of supporting this concept at the State level should be noted. Conclusions – the recycling of agricultural waste in the future will provide a number of benefits in economic, environmental and social aspects. The State should invest capital in the development of a circular economy, since in the long-term perspective the actual benefits of this transition will increase significantly. It is important to research not only the efficiency and functionality of the circular economy, but also to conduct the research and implement innovations that contribute to the functioning of this system.

Geology and construction: survey of archaeological sites and their natural environments (Gulf of Corinth, Greece)

This study attempts to demonstrate how Greek builders exploited their geological environment during the Archaic to Hellenistic periods. Four major sites in the eastern part of the Gulf of Corinth are compared: the old city of Corinth, the sanctuary of Poseidon at Isthmia, ancient Sikyon and the Heraeum at Perachora. Ancient builders utilised primary topographic features and natural resources to their advantage, thus reducing costs. They preferred local low-density stones sourced from the more recent Corinth syn-rift deposits (calcarenite, oolitic grainstone, sandstones, stromatolites and conglomerates), rather than the pre-rift Mesozoic carbonates. These local stones represent more than 90% of the volume employed for public construction. Greek builders also imported allochthonous high-porosity limestones for their temples. Hard stones, such as marbles, do not appear to have been attractive to ancient builders at any of the studied sites.