• A comparative study of analytical methodologies to determine the soil organic matter content of Lithuanian Eutric Albeluvisols

      Jankauskas, Benediktas; Slepetiene, Alvyra; Jankauskiene, Genovaite; Fullen, Michael A.; Booth, Colin A. (2006)
      Large archive databases of soil organic matter (SOM) widely exist in Lithuania and the other countries of Central and Eastern Europe. Despite the demise of the former Soviet Union over 16 years ago, and Lithuania's integration as a full European Union state, difficulties of SOM data acceptance remain where these results are presented for publication in international journals, due to methodological differences between laboratory protocols. Therefore, the scientific pilot project ‘Carbon sequestration in Lithuanian soils’, supported by the Leverhulme Trust (U.K.), included an objective to correlate soil carbon methodologies, using Lithuanian Eutric Albeluvisols. A comparison of SOM content data acquired using five different analytical methods is reported. The research programme included a specific objective to correlate analytical methods for SOM analyses. A total of 92 Eutric Albeluvisol samples were collected from topsoil (0–0.2 m: Ap, n=36; Ah, n=10) and subsoil (0.2–0.4 m: Bt, n=46) horizons of 46 long-term experimental field plots at the Kaltinenai Research Station of the Lithuanian Institute of Agriculture. Each sample was then subsampled and analysed for SOM using dry combustion (by automatic elemental analyser), Walkley–Black (USDA), Tyurin photometrical, Tyurin titrimetrical and loss-on-ignition (LoI) methods (the later performed, in parallel, in both Lithuania and U.K. laboratories). Linear correlation and paired regression equations were calculated. Correlation coefficients between the sets of results varied between r=0.81–0.96 (from 0–0.2 m, n=46, P<0.001) and r=0.76–0.98 (from 0.2–0.4 m, n=46, P<0.001). Based on the strength and significance of these relationships, it is proposed that simple linear or more complex paired regression equations can be confidently employed to recalculate SOM data between various analytical methodologies. Future work will continue these investigations on other soil units and environments, hereby enhancing the database.
    • A dynamic approach to urban road deposited sediment pollution monitoring (Marylebone Road, London, UK)

      Crosby, C.J.; Fullen, Michael A.; Booth, C.A.; Searle, D.E. (Elsevier, 2014-06)
      The use of mineral magnetic measurements (χLF, χARM and SIRM) as a potential pollution proxy using road deposited sediment (RDS) is explored as an alternative means of monitoring pollution on a busy city road. Comparison of sediment-related analytical data by correlation analysis between mineral magnetic, particle size and geochemical properties is reported. Mineral magnetic concentration parameters (χLF, χARM and SIRM) reveal significant (p < 0.001; n = 61) associations with PM1.0, PM2.5 and PM10. Significant associations were also found with mineral magnetic concentrations (χLF and SIRM) and specific concentrations of the elements Fe, Ni, Cu, Zn and Mn (p < 0.001; n = 61). Inter-geochemical correlation analysis found strong associations (p < 0.001; n = 61) between Fe, Ni, Cu, Zn and Mn and suggest anthropogenic enrichment influences. Low χFD% measurements imply an influence of multi-domain mineralogy, indicative of anthropogenic combustion processes. SEM micrographs also support this, as all samples contain Fe spherules indicative of vehicular combustion processes. This study advocates rapid and simple initial assessment of urban pollution episodes using mineral magnetic measurements as a dynamic explorative technology.
    • A multicriteria approach to evaluating habitat change in urban areas: an example from the Black Country (UK)

      Young, Christopher; Jarvis, Peter (Ashurst: WIT Press, 2003)
      THE BOOK: The pressure on land resources in densely populated industrialized countries is now immense. Multifunctional management is therefore a prerequisite for the sustainable use of landscapes, and the only general strategy that may address the problems created by constantly growing demands on resources arising from production, residence, dumping of waste, habitat, ecosystem services, and recreation. This volume focuses on the discussion and research recommendations relating to three different aspects of future landscape research concerning planning and management: Monitoring Multifunctional Landscapes; Biodiversity Versus Landscape Diversity in Multifunctional Landscapes; and Complexity of Landscape Management. (WIT Press)
    • A Novel Method for Cleaning Reaction Vessels.

      Cox, Jeffrey J.; Gibbons, M. N. N.; Hudson, I. D.; Williams, Craig D. (NISCAIR, 2002)
      The objective of zeolite synthesis is the production of pure phase material and a study by Lowe et al. showed that small and possibly significant amounts of template remaining in supposedly clean vessels could influence the crystallisation of subsequent gels. Two cleaning methods are widely used to clean the synthesis reaction vessels i.e. hydrofluoric acid or a solution of sodium hydroxide at reaction temperature, but their efficacy has not been tested. Zeolite omega was synthesized with both organic and inorganic templates and, following synthesis, the reaction vessels were cleaned by a novel method, described here, using hydrofluoric acid, crown ethers, and ultrapure water. This new method was compared to the standard methods by using a ‘scavenging gel’ to test the cleanliness of the vessels. The ‘scavenging gel’ produced some crystalline material when used following conventional cleaning whereas, when the vessels were cleaned using the method described here, the gel failed to crystallise. Conductivity measurements have proved a reliable index to the cleanliness of the reaction vessels.
    • A Simple Method for Predicting the Consequences of Land Management in Urban Habitats

      Young, Christopher; Jarvis, Peter (Springer New York, 2001)
      Land management in urban areas is characterized by the diversity of its goals and its physical expression in the landscape, as well as by the frequency and often rapidity of change. Deliberate or accidental landscape alterations lead to changes in habitat, some of which may be viewed as environmentally beneficial, others as detrimental. Evaluating what is there and how changes may fit into the landscape context is therefore essential if informed land-management decisions are to be made. The method presented here uses a simple ecological evaluation technique, employing a restricted number of evaluation criteria, to gather a spatially complete data set. A geographical information system (GIS) is then used to combine the resulting scores into a habitat value index (HVI). Using examples from Wolverhampton in the United Kingdom, existing real-world data are then applied to land-management scenarios to predict probable landscape ecological consequences of habitat alteration. The method provides an ecologically relevant, spatially complete evaluation of a large, diverse area in a short period of time. This means that contextual effects of land-management decisions can be quickly visualized and remedial or mitigating measures incorporated at an early stage without the requirement for complex modeling and prior to the detailed ecological survey. The strengths of the method lie in providing a detailed information baseline that evaluates all habitats, not just the traditional “quality” habitats, in a manner that is accessible to all potential users—from interested individuals to professional planners. (Springer Verlag)
    • A study of the chemistry of isomorphous substitution and characterisation of Al-ZSM-5 and Sc-ZSM-5 synthesised in fluoride media.

      Brigden, Clive T.; Williams, Craig D.; Apperley, David C. (MAIK Nauka/Interperiodica distributed exclusively by SpringerLink, 2007)
      Al-ZSM-5 and Sc-ZSM-5 samples have been synthesized using fluoride media at around neutral pH. The synthesis chemistry has been studied and it is shown how the lower tendency of scandium to undergo increased fluoro-complexation (compared with aluminum) coupled with its tendency to hydrolyze is conductive to its isomorphous substitution and framework incorporation into the MFI zeolite structure. Clear unit cell volume expansion, elongation of the c crystallographic axis with increased scandium content, and a strong positive linear correlation between the unit cell volume expansion and the calculated unit cell framework scandium content are shown. Chemical shifts are assigned to tetrahedral and octahedral scandium from 45Sc MAS NMR analysis. Shoulders and a peak at lower wavenumber on the main internal T-O asymmetric stretches in the FT-IR spectra indicate that an interaction exists between framework-incorporated scandium and the SiO4 tetrahedra. It is concluded from the experimental evidence that isomorphous substitution of scandium into the zeolite framework has been achieved.
    • A tin-lead alloy found in a zeolitic amygdale at Carsaig Bay on the Hebridean Isle of Mull.

      Dyer, Alan; Green, David I.; Taylor, Beryl; Williams, Craig D. (Russell Society, 2005)
    • Agricultural soil properties and crop production on Lithuanian sandy and loamy Cambisols after the application of calcareous sapropel fertilizer

      Bakšienė, Eugenija; Fullen, Michael A.; Booth, Colin A. (Taylor & Francis, 2006)
      Lake-derived organic-rich mud (sapropel) is used as a soil fertilizer on sandy loam Haplic Luvisols in Lithuania. Various application rates (50, 100, 150 and 200 t ha-1) were applied to crop rotations (maize, barley, clover, winter rye, potatoes and oats) and their subsequent long-term influences on soil physico-chemical properties and crop production determined. Soil agrochemical properties were evaluated before (1984 – 1985) and after the end of the first (1989 – 1990), second (1995 – 1996) and third (2001 – 2002) crop rotations from seven treatments with four replications. In most cases, after each crop rotation, there were notable increases in pH, total absorbed bases, total nitrogen content, available phosphorus and potassium and soil organic matter content (humus). After three rotations, changes in soil acidity, total nitrogen and humus on all sapropel treatments were significant (p < 0.05), but effects on phosphorus and potassium were not significant. In comparison, for most treatments, manure produced greater improvements in soil properties than sapropel. However, after 18 years of application, sapropel did improve crop productivity almost to the level achieved by applications of manure and fertilizers. Therefore, results demonstrate there are long-term benefits of sapropel applications, namely improvements in soil properties and crop productivity.
    • Agro-environmental lessons from the 'sustainable highland agriculture in South-East Asia' (SHASEA) project

      Fullen, Michael A.; Booth, Colin A.; Panomtaranichagul, Mattiga; Subedi, Madhu; Li, Yongmei (Taylor & Francis, 2011)
      To promote sustainable agro-environmental development in the highlands of South-East Asia, an international multidisciplinary research team examined the effectiveness of selected agronomic and soil conservation treatments (both modified and novel cropping practises) using farmer-managed runoff plots. The study sites were located in the highlands of Yunnan Province (Wang Jia Catchment), China and Mae Honson Province (Pang Mapa District), Northern Thailand. Project lessons relating to co-operation, research partnerships, time horizons, multidisciplinarity, income generation, information dissemination and education are discussed.
    • Agro-environmental project duration and effectiveness in South-east Asia

      Subedi, Madhu; Fullen, Michael A.; Hocking, Trevor J.; McCrea, Alison R.; Milne, Eleanor (IP Publishing, 2010)
      Considerable emphasis has been placed on developing technologies for agricultural sustainability. Many bilateral projects are working to achieve this outcome. A desk review was conducted to study the importance of project duration for the effectiveness of sustainable agricultural projects. Longer-duration projects were successful in addressing more holistic issues than short projects. However, funding agencies tend to fund shorter-duration projects, so projects become progressively shorter. At the same time, the number of projects implemented each year is increasing. Despite the decrease in total development assistance, increases in project numbers, particularly since 1986, appear to be at the cost of project duration. Short project duration was one of the most cited reasons for not completing essential dissemination activities for wider adoption, whereas longer- duration projects were usually considered more successful in addressing more holistic issues. It is difficult to produce tangible outputs from agricultural and soil conservation projects within five years. Considering the slow changes in the system and in agricultural and environmental sustainability, the authors suggest that project developers should be advised to plan for a minimum of 5–10 years, depending on the nature of activities. It is time for funding agencies to reconsider their tendency to fund shorter-duration projects.
    • Agro-environmental sustainability of the Yuanyang rice terraces of Yunnan (China): lessons for Europe.

      Fullen, Michael A. (2009)
      The Hani minority people of Yunnan Province (south-west China) have developed a complex and sustainable agro-environmental system of terraced rice paddy fields in Yuanyang (22°49’-23°19’N, 102°27-103°13’E). The Hani people have maintained this intricate and elaborate system for over 1500 years, with some 3,000 terraces covering about 11,000 hectares. Hence, during the Ming Dynasty (1368-1644), the Emperor awarded the Hani people the title of ‘Magic Mountain Sculptors.’ However, geographic isolation and proximity to the, until recently, politically-sensitive border with Vietnam, has meant the Yuanyang terraces have attracted scant scientific attention. If we can understand how this system is sustained, we can learn lessons which hopefully can be applied more generally. The sustainability of the system seems to be the result of complex interplays between cultural, agronomic and environmental factors. These include the cultural and spiritual beliefs of the Hani people, a hydrogeological system which provides ample water resources, the maintenance of genetic diversity within the dominant rice cropping agro-ecosystem and the operation of complex fertigation practises. Distilling and understanding the ‘secrets’ of the Hani people and their terraces should enable broader application and dissemination of the principles of sustainability. Currently a joint Chinese-European team are working towards a greater understanding of these lessons. The research team postulate that these lessons will have some applicability for agro-environmental sustainability in Europe. Identified lessons relate to resource optimization, landscape multifunctionality and cultural attitudes. Landuse within Yuanyang is zoned on the basis of ecological principles. Upland grassland progresses downslope into forest and then in a downslope sequence into tea plantations, bamboo woodland and rice terraces. Grasslands are used for the grazing of water buffalo, while wooded areas provide timber (deciduous, pine and bamboo) and food (mushrooms, wild vegetables and honey). The local Yunnan pine (Pinus yunnanensis) provides an excellent source of timber. Furthermore, the forest is very effective in conserving soil and water and releases high quality water from the upper to lower slopes. Besides providing rice, the perennially wet paddy fields provide food for domestic consumption (carp, eels, mudfish, ducks, frogs and snails) and weeds for pig-feed. Thus, there is multifunctional use of each eco-agricultural zone, which ensures optimum use of resources, effective recycling of materials and minimal waste. Often, the net waste from these subsystems is virtually zero. The Hani people have a unique cultural system that reveres the land. The Hani religion embraces polytheism and the worship of nature. They pay particular devotion to the ‘forest god,’ which is perceived as the source of life-giving water. Deforestation is considered a religious violation and the Hani people actively teach their children to respect the forest. This concept significantly contributes to forest conservation and ecosystem stability. In Europe, we can learn much from these positive environmental attitudes, in terms of improving public understanding and appreciation of land resources (land literacy) and agro-environmental education at multiple levels (school, college and university)
    • Agro-environmental Sustainability of the Yuanyang Rice Terraces of Yunnan Province, China

      Fullen, Michael A. (Programa de Pós-Graduação em Geografia da Universidade Federal do Rio de Janeiro, 2014)
      The Hani minority people of Yunnan Province (south-west China) have developed a complex and sustainable agro-environmental system of terraced rice paddy fields in Yuanyang (22°49’-23°19’N, 102°27-103°13’E). The Hani people have maintained this intricate and elaborate system for over 1,300 years, with some 3,000 terraces covering about 11,000 hectares. Hence, during the Ming Dynasty (1368-1644), the Emperor awarded the Hani people the title of “Magic Mountain Sculptors” for “building their ladders to Heaven.” However, geographic isolation and proximity to the, until recently, politically-sensitive border with Vietnam, has meant the Yuanyang terraces have attracted scant scientific attention. If we can understand how this system is sustained, we can learn lessons which hopefully can be applied more generally.
    • An evaluation of the introduction of modified cropping practices in Yunnan Province, China, using surveys of farmers' households

      Subedi, Madhu; Hocking, Trevor J.; Fullen, Michael A.; McCrea, Alison R.; Milne, E.; Mitchell, David J.; Wu, Bozhi (Chinese Academy of Agricultural Sciences. Published by Elsevier B.V., 2009)
      Problems associated with land degradation are serious in China. Sloping land in South China has experienced a decline in crop productivity by 30-60% due to soil erosion and it has been predicted that most topsoil will be lost within the next 100 years if current erosion rates continue. Considering these situations, an agro-environmental research and development project (Sustainable Highland Agriculture in South-East Asia – SHASEA) was conducted in a catchment in Yunnan Province, China, to address the objectives of increasing crop productivity in sustainable and environmentally-friendly ways. A range of cropping practices was developed and implemented in a rural upland catchment (Wang Jia). At the end of the project, farmers were surveyed to evaluate project effectiveness. All farmers from Wang Jia Catchment, who were involved in project implementation, were surveyed. A sample of farmers working in an adjacent catchment (not associated with the project) was surveyed for comparative purposes. Farmers had different perceptions of the cropping practices employed. Contour cultivation was preferred and likely to be adopted. Others practices such as straw mulching and intercropping were seen as less appropriate and unlikely to be adopted. Polythene mulch was recognized as effective, but likely to be adopted only if financial returns were favourable. The availability of relevant information had an important impact on the extent of technology testing by farmers and their willingness to adopt the practices in the future.
    • Application of mineral magnetic concentration measurements as a particle-size proxy for urban road deposited sediments

      Crosby, C. J.; Booth, Colin A.; Worsley, Annie T.; Fullen, Michael A.; Searle, David E.; Khatib, Jamal M.; Winspear, C. M. (Southampton : Wessex Institute of Technology Press, 2009)
      The application of mineral magnetic concentration parameters (χLF, χARM and SIRM) as a potential particle size proxy for urban road deposited sediment collected from Scunthorpe, North Lincolnshire, U.K. has been investigated. Correlation analyses between each magnetic parameter and traditional particle size classes (i.e. sand, silt and clay) and respiratory health related size classes (i.e. PM10, PM2.5 and PM1.0) are reported. Significant relationships (p <0.01; n = 35) exist between clay content and two of the magnetic concentration parameters (χARM and SIRM). This is also the same for each of the PM10, PM2.5 and PM1.0 sizes. Of the three magnetic parameters, χARM displays the strongest correlation (r = 0.45; p <0.01; n = 35) values and is the most significant parameter, which is consistent with class sizes of each approach. In doing so, these associations indicate mineral magnetic associations have considerable potential as a particle size proxy for determining urban roadside particulate matter concentrations. Given the speed, low-cost and sensitivity of the measurements, this suggests magnetic techniques could be potentially used as an alternative and/or complementary technology for pilot particulate pollution investigations. Furthermore, in certain instances, it could be useful for examining linkages between respiratory health and particulate pollution and vehicle emissions.
    • Assessing the structural heterogeneity of urban areas: an example from the Black Country (UK)

      Young, Christopher; Jarvis, Peter (Springer Netherlands, 2001)
      The increasing acknowledgement of the importance of urban habitats in the maintenance of biodiversity has brought with it a need to quantify this importance at a scale appropriate to the characteristic patch sizes encountered in urban areas. Taking a study area in the Black Country (UK) we used a spatially complete, rapid assessment method to evaluate habitat patches in terms of their internal structural heterogeneity. This method recognises the importance of both natural and anthropogenic processes in providing a diverse range of habitats and niches for both flora and fauna. It also recognises the key role of context in determining the ecological significance of each patch within the urban landscape. All habitats studied had a complex mix of both natural and artificial structural elements, where an element is a within-patch contributor to structural diversity, with each habitat type having a large range of element totals. Characteristic totals, reflecting the level of habitat structural diversity, were observed in some habitat types with residential areas having high values and industrial and commercial areas having low values. Certain structural elements were also associated with each habitat type allowing characteristic element assemblages to be derived. If structural diversity is linked with biodiversity, as seems to be the case in many (though not all) habitat types, then this unique method of viewing the urban landscape becomes a powerful tool for informing wildlife ecologists, nature conservationists, urban planners, environmental managers and landscape architects. (Springer Verlag)
    • Butterfly Activity in a Residential Garden

      Young, Christopher (Brooklyn, NY: Brooklyn Botanic Garden, 2008)
      Butterflies are a highly visible, well-loved, and well-studied part of Britain's native fauna, yet there is still very little known about how butterflies use one of the country's most commonly available habitats, the residential garden. Studies in a Wolverhampton (UK) garden demonstrate that the majority of individuals use these spaces as movement routes through the urban matrix. Of 516 observed individual visits by butterflies over three recording seasons (2000–2002), only 13.8% involved a stop for some purpose. The duration of these visits was characteristically short, with a mean visit time of nine seconds. Individuals tended to fly through the study garden using distinct entry and exit points largely dictated by variations in structure within the study garden and in the immediately surrounding gardens. Individual garden use by butterflies would therefore seem to be defined as much by structural imperatives as by availability of nectar- or food-plant species. When considered as systems of interconnected green spaces on the level of the housing block (defined as a continuous area of residential land use bounded by infrastructure or contrasting land uses) and of the urban area as a whole, residential gardens represent an extraordinarily valuable and dynamic component of the urban habitat.
    • Carbon sequestration and relationship between carbon addition and storage under rainfed soybean–wheat rotation in a sandy loam soil of the Indian Himalayas

      Kundu, S.; Bhattacharyya, Ranjan; Prakash, Ved; Ghosh, B.N.; Gupta, H.S. (Elsevier, 2007)
      Soil organic matter (SOM) contributes to the productivity and physical properties of soils. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, no information is available on the effects of long-term manure addition along with mineral fertilizers on C sequestration and the contribution of total C input towards soil organic C (SOC) storage. We analyzed results of a long-term experiment, initiated in 1973 on a sandy loam soil under rainfed conditions to determine the influence of different combinations of NPK fertilizer and fertilizer + farmyard manure (FYM) at 10 Mg ha−1 on SOC content and its changes in the 0–45 cm soil depth. Concentration of SOC increased 40 and 70% in the NPK + FYM-treated plots as compared to NPK (43.1 Mg C ha−1) and unfertilized control plots (35.5 Mg C ha−1), respectively. Average annual contribution of C input from soybean (Glycine max (L.) Merr.) was 29% and that from wheat (Triticum aestivum L. Emend. Flori and Paol) was 24% of the harvestable above-ground biomass yield. Annual gross C input and annual rate of total SOC enrichment were 4852 and 900 kg C ha−1, respectively, for the plots under NPK + FYM. It was estimated that 19% of the gross C input contributed towards the increase in SOC content. C loss from native SOM during 30 years averaged 61 kg C ha−1 yr−1. The estimated quantity of biomass C required to maintain equilibrium SOM content was 321 kg ha−1 yr−1. The total annual C input by the soybean–wheat rotation in the plots under unfertilized control was 890 kg ha−1 yr−1. Thus, increase in SOC concentration under long-term (30 years) rainfed soybean–wheat cropping was due to the fact that annual C input by the system was higher than the required amount to maintaining equilibrium SOM content.
    • Chemistry for Environmental & Earth Sciences

      Duke, Catherine V. A.; Williams, Craig D. (CRC Press (Taylor & Francis), 2007)
      Synopsis: Tackling environmental issues such as global warming, ozone depletion, acid rain, water pollution, and soil contamination requires an understanding of the underlying science and chemistry of these processes in real-world systems and situations. "Chemistry for Environmental and Earth Sciences" provides a student-friendly introduction to the basic chemistry used for the mitigation, remediation, and elimination of pollutants. Written and organized in a style that is accessible to science as well as non-science majors, this textbook divides its content into four intuitive chapters: Fire, Earth, Water, and Air. The first chapter explains classical concepts in chemistry that occur in nature such as atomic and molecular structures, chemical bonding and reactions, states of matter, phase transitions, and radioactivity.Subsequent chapters focus on the chemistry relating to the geosphere, hydrosphere, and atmosphere-including the chemical aspects of soil, water, and air pollution, respectively.
    • Clinoptilolite and Heulandite from Wheal Hazard, St Just, Cornwall.

      Dyer, Alan; Green, David I.; Tindle, Andrew G.; Williams, Craig D. (Russell Society, 2006)
    • Concentrated flow erosion rates reduced through biological geotextiles

      Smets, T.; Poesen, Jean; Langhans, C; Knapen, A; Fullen, Michael A. (Wiley InterScience, 2009)
      Soil erosion by concentrated flow can cause serious environmental damage. Erosion-control geotextiles have considerable potential for reducing concentrated flow erosion. However, limited data are available on the erosion-reducing potential of geotextiles. In this study, the effectiveness of three biological geotextiles in reducing soil losses during concentrated flow is investigated. Hereto, runoff was simulated in a concentrated flow flume, filled with an erodible sandy loam on three slope gradients (13·5, 27·0 and 41·5%). Treatments included three biological geotextiles (borassus, buriti and bamboo) and one bare soil surface. Darcy–Weisbach friction coefficients ranged from 0·01 to 2·84. The highest values are observed for borassus covered soil surfaces, followed by buriti, bamboo and bare soil, respectively. The friction coefficients are linearly correlated with geotextile thickness. For the specific experimental conditions of this study, borassus geotextiles reduced soil detachment rate on average to 56%, buriti geotextiles to 59% and bamboo geotextiles to 66% of the soil detachment rate for bare soil surfaces. Total flow shear stress was the hydraulic parameter best predicting soil detachment rate for bare and geotextile covered surfaces (R² = 0·75–0·84, p < 0·001, n = 12–15). The highest resistance against soil detachment was observed for the borassus covered soil surfaces, followed by buriti, bamboo and bare soil surfaces, respectively. Overall, biological geotextiles are less effective in controlling concentrated flow erosion compared with interrill erosion. Copyright © 2009 John Wiley & Sons, Ltd.