Pratap Srivastava

Current and emerging trends in bioremediation of petrochemical waste: A review

ABSTRACT Various industries release harmful petrochemical contaminants into the environment. To treat these petrochemical contaminants at source, different physical, chemical, and biological methods have been proposed and applied worldwide. However, physical and chemical methods have their own advantages and limitations; in this review, we majorly focused on the biodegradation of petrochemical wastes. First, a background study on the literature available in this field is presented. Second is a review of the toxic effects of petrochemical waste and various physical and chemical processes, followed by elaborate biological processes available for petrochemical waste degradation. Further, different aspects of bioremediation, such as modes, factors, limitations, and future perspectives are critically reviewed and presented. It was found that most of the studies performed on bioremediation of petrochemical waste employed bacteria for the degradation purpose. Some studies also made use of algae, fungi, yeast, genetically modified organisms, biosurfactants, or a consortium of these microbes. Moreover, use of bioremediation is still limited at field scale due to certain limitations, which have been elaborated in this article. Overall, we strongly believe that with bioremediation capturing the attention of environmentalists worldwide, there is still a prevailing need to scale up from lab to land level applications and adaptations.

Effect of invasion by Hyptis suaveolens on plant diversity and selected soil properties of a constructed tropical grassland

Aims Hyptis suaveolens (L.) Poit is an important invader of the tropical and sub-tropical regions of the world. In our study, it has been investigated that how does the H. suaveolens invasion regulate plant species diversity across the seasons in the dry tropical grassland. We hypothesized that a shift in soil inorganic-N availability is caused by invasion, and this shift is integral to access the invasion effect on plant diversity. Methods The study was performed in experimental plots at the Botanical Garden of the Banaras Hindu University (25°16′3.3′′ N and 82°59′22.7′′ E), Varanasi, Uttar Pradesh, India. Five replicates (each, 2 × 2m) of non-invaded grassland plots (NIG) and five grassland plots invaded with H. suaveolens (IG) were established. These plots were constructed by transplanting indigenous grassland patches from an adjacent native grassland. In the invaded plots, 20 individuals of H. suaveolens were transplanted per plot. After 1 year of establishment, diversity attributes and soil properties were recorded from these plots in three seasons as per standard protocol. Important Findings The results indicated that Hyptis invasion negatively affects plant diversity, with relatively higher impact in rainy season as compared to the winter season. IG exhibited lower soil moisture content and temperature than NIG in rainy season, whereas soil ammonium-N, nitrate-N, total inorganic-N, N mineralization registered higher values for IG than NIG in both rainy and winter season. Diversity indices were negatively correlated with soil inorganic-N pool and N mineralization. However, these indices were positively correlated with microbial biomass carbon (MBC), and the correlation coefficient for this relationship was higher for rainy season as compared to winter. Species richness (r = 0.65) and Shannon diversity (r = 0.757) were significantly correlated with the ratio of ammonium-N to nitrate-N. The negative effect of invasion by H. suaveolens on the plant diversity is possibly mediated by the effect of invasion on N mineralization processes (mainly nitrification) and the availability of soil inorganic-N pools. The study indicates that Hyptis invasion has an enormous potential to change the structure and composition of plant communities in the dry tropical grasslands.

Tree seedling establishment in dry tropics: an urgent need of interaction studies

The current anthropogenic activities and climate change are increasingly becoming a growing global concern for dry tropical forests. Worldwide, these ecologically important forests have degraded considerably since the past few decades due to such factors. These factors have harmful consequences on the vegetation structure and diversity especially tree seedlings, which may further aggravate climate change. Generally, the vegetation recovery is very slow and unpredictable in the dry tropics due to complex interaction among tree seedling, site (particularly, soil) and climatic conditions. We inculcated that a better understanding of the behavior of individuals of different tree species at seedling stage in dry forests is of immense importance. It is increasingly being recognized for explaining and managing the future composition of plant communities under changing environmental conditions. In this regard, the multi-factorial interaction studies under various resource–disturbance combinations are needed in dry tropical ecosystems to understand the: (1) impact of relative variability in resources and disturbances on the responses of tree seedlings of native species and (2) how the later relates to distinct functional and life history traits of the individual tree species. Most importantly, such studies would improve our limited understanding of how variation (natural and man-made) in nutrient availability, under the influence of other local environmental factors (such as water, light, grass competition, herbivory, fire, allelopathy and enhanced CO2 conditions), would affect the dynamics of dry tropical forest community. It may help in the proper management of these forests. Moreover, it may prove helpful in the current climate change scenario, as change in forest community dynamics may have consequences on soil C sequestration and CO2 efflux at global scale.

Chapter 22 – Understanding the Complex Interaction Between Soil N Availability and Soil C Dynamics Under Changing Climate Conditions1

Abstract With growing anthropogenic impacts, the understanding of the interaction between the C cycle, the N cycle, and the climate is becoming increasingly important. Globally, it is increasingly accepted that the availability of inorganic-N in soil and associated soil microbial attributes may hold crucial importance in governing soil C dynamics under changing climate conditions. However, a comprehensive review of soil inorganic-N pools with respect to (1) possible behavior under changing climate conditions, (2) impact on SOC dynamics, and (3) its role in the management of future climate, is unexplored. Specifically, whether we can control soil C dynamics via managing soil inorganic-N dynamics has been investigated in this study. We identified that a shift in the relative availability of inorganic-N pools in the soil under a changing soil moisture-temperature interaction may be important in determining the nature of SOC dynamics. This shift may possibly be attributed to a changing stoichiometric relationship between soil microbial processes that is associated with availability of soil inorganic-N pools. It is possible that the variable SOC dynamics may be a function of stoichiometric relationship between (1) the microbial immobilization rate of available ammonium-N and nitrate-N in the soil and/or (2) rate of ammonification and nitrification process. Therefore the interaction among the relative availability of soil ammonium-N and nitrate-N availability, microbial communities/functional groups, and soil ecological functioning under changing climate conditions (or soil moisture-temperature interaction) requires a thorough investigation, which may help in the identification of new indicators, drivers, and theories of the below-ground ecosystem functioning.