Land Reclamation Research Articles

Rehabilitation of Agricultural Land and Ecosystems Around Dams Using Modern Agricultural Techniques

Rehabilitation of Agricultural Land and Ecosystems Around Dams Using Modern Agricultural Techniques

Evaluation of the Success of Planting in the Rehabilitation of a Watershed Area in Sei Lesan Protected Forest, Indonesia

The high level of community activity in using river watershed land has resulted in the exploitation of land around the watershed which has resulted in a decline in soil quality and caused land degradation along the river flow, therefore areas along the river flow require land reclamation so that the natural balance around the watershed is maintained. Reclamation is an activity that aims to repair or organize the use of land that has been disturbed as a result of inappropriate environmental processing business activities so that it can function and be efficient according to its intended purpose. The research aim is to evaluate the level of success of planting in the rehabilitation process of PT Berau Coal in the Lesan River Protected Forest. The research was carried out in the Sei Lesan Protected Forest Area in the Segah Watershed, Kelay Sub Watershed in Kelay District, Berau Regency, East Kalimantan Province, Indonesia from July to August 2022. This research used systematic sampling with the random start method, namely plot measurement, The first measuring plot is created randomly and subsequent measuring plots are created systematically with a sampling intensity of at least 5%. The results of the research show that the level of plant growth in watershed rehabilitation activities at PT Berau Coal Watershed Rehabilitation was declared successful with a plant survival percentage value of 78.24%, and the planting results in the PT Berau Coal Block C watershed rehabilitation area were very good with a percentage of healthy plants of 76.08%.

LEGAL PROVISION OF SOIL (LAND) MELIORATION IN UKRAINE

Melioration is a powerful factor affecting the soil and soil cover, which changes the direction, periodicity and speed of soil processes and regimes, and leads to a gradual transformation of soils. The evolution of soils under the influence of various types of land reclamation is characterized by varying degrees of changes in chemical, physico-chemical, and agrophysical properties, and in the case of the complex application of various types of land reclamation, high agricultural culture acquires a positive direction, improving soil properties. In the case of a violation of the comprehensive implementation of meliorational effects and agrotechnical measures for the cultivation of agricultural crops, low resource provision, a negative balance of organic substances and an imbalance of macro- and microelements can be formed in the soil. Another determining factor in the change in the purpose of melioration effects on the soil is the transition to the ecological imperative of the agrosphere. This direction is the strategic goal of land reclamation in the foreseeable future, which is of great importance for Ukraine, as the world's leading agrarian state. Solving the problem of investments in the field of soil meioration, which arose due to the disorganization of the legal management of soil and land resources in the conditions of increased natural and anthropogenic loads, global climate changes, violation of the structural and landscape organization of the territory and technical requirements in the system of balanced land use, is gaining increasing relevance, perspective and public demand A feature of law-making practice in Ukraine are numerous environmental laws and departmental regulations, but their implementation is too slow. One of the areas of implementation of the provisions and requirements established by regulatory legal acts in the field of soil reclamation is the development of a regulatory and methodological framework in this field. To ensure the unity and effectiveness of the implementation of regulatory documents at different levels, it is necessary to develop and approve lists of documents, in particular standards, which, in the case of voluntary application, are proof of compliance with the requirements of the current legislation on land reclamation, their use and monitoring. Along with the existence of existing laws, it is necessary to adopt already developed draft laws "On soils and their fertility", "On soil monitoring", "On the removal of degraded and unproductive lands for conservation", "On soil insurance". The Law of Ukraine "On Land Leasing" needs to be revised, which needs to be supplemented in the direction of soil protection obligations on the part of tenants by increasing the minimum lease terms and improving the economic mechanism for stimulating the sustainable use and management of land resources, including their protection from degradation. Keywords: soils, melioration, soil protection, legal support.

ANALYZING THE SOCIO-LEGAL DYNAMICS AND IMPACT ASSESSMENT OF LAND ACQUISITION IN BANGLADESH: A COMPARATIVE PERSPECTIVE WITH INDIAN LAWS AND GLOBAL BEST PRACTICES

Land acquisition has continued to be a major concern in Bangladesh, a densely populated country, because of the nation’s limited land resources and the value of land to people’s livelihoods. There is a great deal of hardship and discontent as a result of inadequate land acquisition and rehabilitation policies, which have left the displaced with insufficient compensation and rehabilitation. This article compares and contrasts the land acquisition laws of India and Bangladesh, taking a critical look at both countries’ current legal frameworks. Although recent legislation has been introduced in both countries, Bangladesh’s framework is insufficient to protect the rights and interests of affected landowners. The Acquisition and Requisition of Immovable Property Act 2017 of Bangladesh has also fallen short of international standards on the acquisition process. In order to support sustainable growth and protect landowners’ rights, this article argues for the creation of a transparent legal framework and prudent policies. Based on global experiences and best practices, the paper offers a series of suggestions to improve the process of acquisition and guarantee equitable treatment for all impacted parties. Recognising the critical role of land acquisition in Bangladesh’s development trajectory and its profound impact on the livelihoods of millions, this article underscores the urgency of reforming the existing land acquisition law. This analysis contributes to the ongoing discourse on land acquisition in Bangladesh with the objective to establish a more equitable balance between public interests and the rights of landowners, ultimately benefiting society as a whole.

Tracing holocene paleoenvironmental changes along the northern Tyrrhenian coast (Cornia and Pecora coastal plains, Tuscany, Italy): data from geochemical and sedimentological proxies

In this paper, sedimentological and geochemical data from six cores are presented and discussed in order to better understand the Holocene palaeoenvironmental evolution of the coastal plains of the Pecora and Cornia Rivers (southern Tuscany, Italy). Overall, the stratigraphies show a general upward trend in the evolution of the sedimentary succession of lagoonal environments (low Zr/Rb, high EC values) connected or partially connected to the sea (low EC values), to a seaward progradation of marshy-swampy environments (Mn/Ti, high TOC values) and finally to continental environments with the progradation of distal alluvial plains (high Zr/Rb, low EC values) influenced by runoff phenomena or local water stagnation. This trend is closely related to the increasing input of sediments from inland due to soil erosion processes and, especially in the last two centuries, land reclamation works. In the Cornia coastal plain, the chronologies indicate that lagoonal environments were already present before ca. 8.2ka BC and started receding seaward at around 3.7ka BC. On the other hand, chronologies from ca. 0.5ka BC to ca. 0.6ka AD point to a persistence of lagoonal environments only in areas very close to those already identified as such in historical cartography. In the Pecora coastal plain, the chronologies show that the lagoon environments had already disappeared before ca. 3.3ka BC, whilst the peripheral environments were characterised by abundant vegetation. The latter gradually degraded in favour of the development of shallow to very deep, unvegetated marshlands, which persisted until ca. 1ka AD.

Hydrogeomorphology and recharge mechanism of a coastal aquifer in tectonic-controlled watersheds: A multi-proxy approach based on remote sensing and environmental isotopes

Coastal aquifers worldwide can be considered an essential water source required for preservation of the coastal ecosystems. However, these aquifers are vulnerable to seawater intrusions and over-pumping due to their proximity to the sea and human activities, respectively. Therefore, the investigation of recharge mechanism has special importance in the regions of tectonic rift activities where they exhibit complex geological structures and hydrogeological characteristics. In the current research, an integrated approach of remote sensing and environmental isotopes together with field investigation and subsurface datasets (aeromagnetic, gravity and well logs) are employed to identify the nature and factors affecting groundwater recharge of the Miocene coastal aquifer along the Red Sea-Gulf of Suez western margin (continental rift basin). The research findings reveal that: (1) The coastal Miocene aquifer consists of both clastic (sandstone, sand and gravels) and carbonate rocks (limestone and dolomite) with subsurface thickness ranges between 100 and 200 m. (2) Its groundwater shows contrast salinity values (expressed by total dissolved solids, TDS) between 2755 and 10,996 mg/l, due to the variation in recharge rates and the lithologic dissimilarity of the water bearing formations. (3) The environmental isotopes indicate that the Miocene groundwater has a mixed isotopic signature between modern meteoric (rainfall) and fossil waters. (4) The isotopic data of the Miocene aquifer and the enriched Gulf of Suez verifies that no seawater intrusions are affecting this aquifer with existing hydraulic barriers (clogged/sealed faults or impermeable massive blocks). (5) The hydrogeomorphological investigations, aeromagnetic and gravity data reveal an existence of two morphotectonic depressions (water collectors) which have paleo and recent recharge opportunities for the subsurface sedimentary layers (2–4 km thick). From the applied viewpoint, these two depressions have potential prospects for future groundwater exploration, which has significant impact on food security and land reclamation.

Study of design parameters for staged-filled slurry treated by prefabricated horizontal drains under vacuum preloading

The method of using Prefabricated Horizontal Drains (PHDs) placed in layers under vacuum preloading can significantly speed up consolidation of staged-filled soil slurry. The PHDs can settle with the soil slurry and maintain their shape/pattern and dewatering capacity largely in comparison with Prefabricated Vertical Drains (PVDs). This study presents a field trial focused on treating dredged sediments using PHDs under vacuum preloading for land reclamation purposes. The staged filling involved in the field trial is analyzed using a finite strain consolidation model based on the piecewise-linear finite-difference method. Then, the effects of horizontal and vertical spacings of PHDs on settlement and vacuum consolidation rate are evaluated, considering various combinations of variables for staged-filled soil. It is found that for soils with low compressibility, the consolidation rate is primarily affected by the vertical spacing of PHD layers. For soils with higher compressibility, the consolidation rate is more significantly affected by the horizontal spacing of PHDs, and the final settlement after vacuum preloading is mainly influenced by the vertical spacing of PHD layers. This study provides practical recommendations for cost-effective design of horizontal and vertical spacings of PHDs in efficiently treating soil slurry with different compressibility and initial conditions.

Environmental risk assessment of coastal dredging based on clustering of meteocean forcing

Dredging and dumping in-situ sediments is a fundamental operation for most coastal engineering projects and coastal defense projects, such as the construction of breakwaters, beach nourishment and land reclamation. Future projections in terms of coastal hazard suggest that coastal protection and land reclamation project will be more and more frequent. In this context, the assessment of the environmental and socio-economic impact of the risk induced by dredging is a fundamental step during both the design stage and the operational management. Most of the standard practices and available risk assessment frameworks rely on the numerical prediction of the sediment plume in the large field driven by coastal circulations forced by tides, winds and waves. In this study, we formulated a new risk assessment framework based on an unsupervised machine learning clustering algorithm, K-means clustering, for generating representative meteocean scenarios subsequently used to force a regional circulation model. Moreover, we introduced three criteria of hazard/risk based on the spatial and temporal evolution of the suspended sediment concentration that explained different environmental impacts and two new methods to synthetically present the risk values. The major improvement of the present framework is that the final probability of risk fully describes the statistics in terms of hydrodynamic and dredging conditions.This framework presents the probability analysis of risk spatial distribution based on representative hydrodynamic conditions and dredging scenarios, which is a major improvement of this study compared with previous risk assessment strategies that were unable to predict quantified dredging risk before field construction. Finally, to demonstrate the potentiality of the risk assessment framework, we applied this methodology to the Hong Kong Water and Pearl River Estuary (China) as a pilot case.

Cloudbursts Strike over Foothill Himalayas of Uttarakhand, India: A Case Study from Maldeota, Dehradun District

The present study highlights the cloudburst issues that occurred in Raipur area of Dehradun City. On the night of August 20, 2022, the Raipur area of Uttarakhand state capital Dehradun was lashed by excessive rainfall or cloudbursts resulting in the water level of sub-watersheds of the Song River rising enormously, particularly Bandal Nadi and Song river. Bhaiswar and Sarkhet villages came in limelight which are situated on the Bandal valley due to loss of human lives and property. 5 people were killed while 3 people were injured and 24 animals lost whereas about 8.25 ha of agricultural fields were damaged and 12 families became homeless in these incidences. The transport connectivity of the Sarkhet and adjoining areas was disrupted due to washing off the road in several places. A detailed investigation was carried out in the affected areas to ascertain the causes and impacts of the disaster and the feasibility of rehabilitation land. Geologically, the devastated area is observed to be fragile due to its proximity to Main Boundary Thrust (MBT) and subsequent Fault as also lies to the Eastern fringe of the Mussoorie Syncline. It was also observed that untraditionally ways of habitation patterns in the region and economic opportunities due to increasing tourist inflow in the area are responsible for the enhanced devastating potential of disaster. This work mainly concentrates on future risk and suggestions for future risk mitigation within the area.

Changes of Chinese forest‐grassland ecotone in geographical scope and landscape structure from 1990 to 2020

Forest–grassland ecotone (FGE) has essential ecological and economic value. Unfortunately, it is impacted greatly by environmental changes and anthropogenic disturbance, and is considered one of the most severely threatened biomes in China. To protect Chinese FGE, identifying its exact boundary and exploring its landscape structure dynamic are badly needed, especially on nationwide scale at one‐year temporal resolution. Here, we mapped the annual FGE distribution of China from 1990 to 2020, investigated its changing trends of area, location and landscape patterns, and revealed the underlying driving factors. Our results showed that FGE area over the 31 years totaled 1 011 870 km2, covering about 10.54% of China's land. The FGE area first increased from 1990 and peaked in 1999, and then kept decreasing until 2020. The FGE gravity center has moved accumulatively 590.15 km over the 31 years, with the net moving distance of 228.76 km southwestward. From 1990 to 2020, forest area increased continuously while grassland and cropland area decreased, but these three landscape types had been dominating the FGE. The increase in forest area was largely converted from grassland. The decline in grassland mainly resulted from its conversion into cropland and forest. Meanwhile, the conversion of cropland to grassland supplemented grassland loss to a certain extent. At landscape level, the total area with decreased fragmentation is larger than that with increased fragmentation. Returning Farmland to Grassland Project and land reclamation were primary drivers for changes of fragmentation in the northern and middle part of the FGE, while temperature and precipitation were primary drivers in southern part. Our results will improve the understanding into the dynamic trends of distribution and pattern of FGE at nationwide scale, and thus help to optimize the designing of ecological projects and protective schemes for FGE as a unique and integral biome.

Response of the soil bacterial community to seasonal variations and land reclamation in a desert grassland

Soil bacteria are important participants in biogeochemical cycles, and the stability of their community structure is not only affected by fluctuations in time and environment, but also by the participation and regulation of anthropogenic interference. With the increasing reclamation of farmland in the agropastoral transitional zone of northern China, it is imperative to understand the characteristics of soil bacterial communities in response to seasonal variations and anthropogenic reclamation. In this study, desert grassland, artificial shrubland, and desert grassland reclaimed farmland on the western side of the Mu Us Sandy Land were used as research objects. The following main results were obtained through soil sampling in April and September, and physicochemical analyses combined with 16S high-throughput sequencing: seasonal variations increased soil pH and soil water content, whereas land reclamation significantly increased soil total carbon, total phosphorus, soil available phosphorus, and soil available potassium contents. Changes in soil physicochemical properties altered the structure of soil bacterial communities to varying degrees, with Actinobacteriota and Acidobacteriota being the differential phyla among the three sampling sites under seasonal variations (p < 0.05). The relative abundance of Actinobacteriota was significantly higher in April than in September at all three sampling sites, and that of Acidobacteriota was significantly lower in April than in September. Therefore, Actinobacteriota and Acidobacteriota are key ecological indicators for predicting changes in the physicochemical properties of desert grassland soils. Actinobacteriota not only affected the complexity of the soil bacterial network, but also had a significant linear relationship with bacterial community stability. Actinobacteriota subgroups (Solirubrobacterales, Propionibacterales, 0319-7L14, and Gaiellales) were also strongly associated with soil bacterial community stability. Solirubrobacter, Gaiella, Nocardioides, Marmoricola, and Kribbella, which play crucial roles in maintaining the stability of bacterial communities, responded positively to changes in pH and soil water content. This study demonstrates the response of soil bacterial communities to environmental changes in a desert grassland and emphasizes the importance of Actinobacteriota as an indicator of soil ecosystem health.

Militarized granularity: Sand’s making of men and masculinity in Singapore

ABSTRACT Land reclamation is the process of transforming mined sand from rivers, estuaries, the seabed and even islands into new land parcels. This article examines Singapore’s insatiable appetite for sand and discusses the relationality between a singular grain of sand’s capacity to militarize and gender the Southeast Asian island-state. With opaque sand supply chains, Singapore can project its sovereignty as a militarized nation-state through the neo-colonialist like extraction of sand from other countries to widen its territorial frontiers. In placing the spotlight on extensive land-reclamation works to expand Tekong Island, Singapore’s largest outlier into a military base, I explain how sand serves the role of creating a militarized boundary object. While sand’s coarseness configures military masculinity, sand’s smoothness serves the additional function of maintaining civilian support for militarism by way of ‘packaging’ masculinity. The granular cartographies of trauma arising from Singapore’s territorial expansions wrought upon Southeast Asia’s rural poor require urgent recuperation.

Вплив геологічних структур на характер русел правобережних приток річки Дністер

The proposed study aims to determine the influence of geological structures on the features of the channels of the largest right-bank tributaries of the Dniester River - the Stryi, Bystrytsia, and Limnytsia rivers. For this purpose, we conducted zoning of the river based on morphometric and hydrological characteristics. Three parts were identified: mountainous, pre-mountainous area and plain area, which differ significantly in channel properties, their changes over time, and deformation processes. Objective. Based on remote sensing images of various resolutions, the use of historical maps over time, and specialized maps, to investigate the nature of the channels of the right-bank tributaries of the Dniester: Stryi, Limnytsia, and Bystrytsia, from their sources to the estuarine part where they flow into the Dniester River, depending on the geological and lithological features of the surface. The main research methods involve the transformation of various materials from remote sensing, historical, and special maps for the purpose of studying specific phenomena of river processes. The methodology involves the preparation of input materials, including historical topographic maps, geological maps, satellite images, maps and images georeferencing, satellite image processing, river channel vectorization, analysis of river channels depending on geological structures. Results. Considering the morphology, valley width, manifestation, and development of channel processes, the Stryi, Bystrytsia, and Limnytsia rivers were categorized into three sections: mountainous, pre-mountainous and plain area with developed accumulative forms. In the mountainous section, all three rivers have single channels, while in the pre-mountainous section, multichannel patterns are observed, which have decreased from the 19th to the 21st century in terms of the width of multichannelity and the number of channels. This indicates a decrease in the flow modulus. For the plain sections of channels with undeveloped accumulative forms, a clear tendency towards dependence of channel type on structural-lithological features is traced. Originality. The paper has established the dependence of channel processes of right-bank tributaries of the Dniester River on geological and sedimentological structures of the Skole Beskids and Subcarpathian Depression. Practical significance. The results of monitoring channel processes need to be considered in addressing a range of tasks, including the construction of hydraulic structures, designing power transmission networks at river crossings, developing gas pipelines, determining flood zones, assessing the consequences of erosion after floods, land reclamation, establishing water protection zones, managing recreational and border lands, and establishing interstate borders along rivers.

Plant Community Hemeroby is a Reliable Indicator of the Dynamics of Reclamation of Lands Disturbed by Mining

Abstract Reliable indicators of success are needed to monitor the process of reclaiming disturbed land in order to understand the achievement of reclamation objectives. The formation of coherent dynamics of vegetation and soil development is ultimately a crucial condition for the success of reclaiming territory disturbed by surface mining and the possibility of using reclaimed land in agricultural production. The study revealed a relationship between the phytoindicator of vegetation hemeroby and the physical properties of technosols to prove its application as a measure of the restoration of the disturbed ecosystem in the reclamation process. The plant communities were classified into beta-, alpha-euhemerobic, polyhemerobic and metahemerobic levels of anthropogenic transformation. The technosols varied in the proportion of hemeroby levels of plant communities. The hemeroby level was consistent with the physical properties of technosols. A decrease in hemeroby level resulted in increased soil electrical conductivity, decreased soil penetration resistance and altered soil aggregate structure. The hemeroby of plant communities is a dependable phytoindicator of ecosystem restoration during reclamation.

Conceptualizations of Abandoned Mine Land Reclamation: A Case Study of the Daniel Boone National Forest

abstract: The Daniel Boone National Forest (DBNF) contains numerous abandoned mine sites left over from eastern Kentucky's history of coal mining, many of which are leaching contaminants into the environment. The United States Forest Service is acting to reclaim these sites to mitigate negative impacts. There are several other governmental and non-governmental actors in Appalachia with different conceptualizations of reclamation's purpose. This research examines the mine land reclamation process on a protected area within a region with a history of resource extraction and builds on previous work to understand different conceptualizations of abandoned mine land reclamation in Appalachia. Content analysis was conducted on DBNF project documentation, interviews, and documentation from state and federal agencies, and NGOs. These documents indicate that government entities tend to conceptualize reclamation and its purpose in a siloed manner. This research also reveals that non-governmental actors tend to conceptualize reclamation in a holistic manner but are less able to exert control over an area. The DBNF largely conceptualizes the purpose of reclamation as achieving ecosystem restoration but may benefit from working more closely with NGOs and adopting a similarly holistic approach. Opening a dialogue between these actors could help address the knowledge gap present at the DBNF's sites.

Storage effectiveness of cajuput seedcake (Melaleuca cajuputi Powell) to increase the success of post-mining land reclamation

Storage effectiveness of cajuput seedcake (Melaleuca cajuputi Powell) to increase the success of post-mining land reclamation

Study on environmental characteristics of sustainable biomimetic soil preparation and its application in gangue reclamation

To address the key challenges in achieving large-scale ecological reclamation of coal gangue in situ, this study utilized loess from a mining area in Northwest China to prepare a biomimetic soil. A new inorganic curing agent (ISA) was developed using coal-based solid waste and cement. The study investigates the influence of different ISA dosages and their interaction with Polyacrylamide (PAM) on the environmental characteristics of biomimetic soil, including geotechnical, ecological, and heavy metal stabilization properties. Results indicate that the addition of ISA significantly enhanced the geotechnical performance of the in-situ soil, with unconfined compressive strength exceeding 350 kPa when ISA content was above 6 %. Soil evaporation experiments and soil water characteristic curve tests demonstrated that a 6 % ISA dosage combined with 0.05 ‰ PAM could maintain soil's good water retention capability while preserving a bimodal pore structure. The biomimetic soil exhibited effective stabilization of heavy metals, including Pb, Zn, Cu, and As. The particles of PAM and the hydration products of ISA not only filled soil pores and increased soil strength but also adsorbed, encapsulated, and immobilized heavy metals. “Biomimetic soil-gangue” leaching test results confirmed that the gangue samples treated with biomimetic soil met the standards for Class III underground water in China regarding heavy metal leaching values. This study provides an effective solution for the large-scale in-situ disposal and resource utilization of gangue in Northwestern mining areas of China.

Urbanization of a Subtropical Island (Okinawa, Japan) Alters Physicochemical Characteristics and Disrupts Microbial Community Dynamics in Nearshore Ecosystems

Subtropical and tropical islands are undergoing rapid urbanization as the human population expands globally. Urbanization disrupts coastal ecosystems through several pathways—including the replacement of natural habitats with concrete structures that increase runoff pollution—but it remains difficult to isolate and characterize specific impacts of urbanization on marine ecosystems. The historical gradient in urbanization on the subtropical island of Okinawa, Japan, sets up a natural laboratory to study urbanization effects on nearshore ecosystems. Physicochemical parameters and bacterial community composition were assessed every 2 weeks for 1 year at two nearshore sites adjacent to watersheds with > 70% urban land use and two nearshore sites adjacent to watersheds with > 70% rural land use. Urbanization increased freshwater input and nutrient loading—indicated by decreased salinity and elevated nitrate + nitrite, ammonium, and phosphate at urban sites—despite the urban sites being more open to flushing due to land reclamation projects filling in the coral lagoon. Urbanization significantly altered microbial community composition by increasing diversity through the addition of fecal indicator and pathogenic bacteria—eight orders of bacteria were only detected in urban samples, whereas only Verrucomicrobiales was unique to rural samples. The change in microbial community composition at urban sites persisted throughout the seasonal cycle, suggesting a regime change or sustained disturbance. The altered physicochemical conditions and microbial communities at urban sites could degrade nearby coral reefs and their ecosystem services, highlighting the importance of coastal land management in marine conservation efforts.

PFAS fate using lysimeters during degraded soil reclamation using biosolids.

Carbon- and nutrient-rich biosolids are used in agriculture and land reclamation. However, per- and polyfluoroalkyl substances (PFAS) typically present in biosolids raise concerns of PFAS leaching to groundwater and plant uptake. Here, we investigated PFAS persistence and leaching from biosolids applied to a site constructed artificially to mimic degraded soils. Treatments included biosolids and biosolids blended with mulch applied at different rates to attain either one and five times the agronomic N rate for vegetable crops and a control treatment with synthetic urea and triple superphosphate fertilizer. Leachates were collected for a 2-year period from 15-cm depth zero-tension drainage lysimeters. Soils were analyzed post biosolids application. PFAS were quantified using isotope-dilution, solid-phase extraction and liquid chromatography tandem mass spectrometry. Leachate profiles exemplified an initial high total PFAS concentration, followed by a sharp decline and subsequent small fluctuations attributed to pre-existing soil conditions and rainfall patterns. Quantifiable PFAS in leachate were proportional to biosolids application rates. Short-chain perfluoroalkyl acids (CF2<6) were dominant in leachate, while the percentage of longer chains homologues was higher in soils. A 43% biosolids blend with mulch resulted in 21% lower PFAS leachate concentrations even with the blend application rate being 1.5 times higher than biosolids due to the blend's lower N-content. The blending effect was more pronounced for long-chain perfluoroalkyl sulfonic acids that have a greater retention by soils and the air-water interface. Biosolids blending as a pragmatic strategy for reducing PFAS leachate concentrations may aid in the sustainable beneficial reuse of biosolids.

Soil Organic Nitrogen Mineralization and N2O Production Driven by Changes in Coastal Wetlands

AbstractPlant invasion and land reclamation have drastically transformed the landscape of coastal wetlands globally, but their resulting effects on soil organic nitrogen (SON) mineralization and nitrous oxide (N2O) production remain unclear. In this study, we examined 21 coastal wetlands across southern China that have undergone habitat transformation from native mudflats (MFs) to Spartina alterniflora marshes (SAs), and subsequently to earthen aquaculture ponds (APs). We determined the SON net mineralization rate and the presence of pertinent enzyme‐encoding genes, namely chiA, pepA, and pepN. The SON net mineralization rate increased by 46.7% following the conversion of MFs to SAs but decreased by 33.1% in response to the transformation of SAs to APs. Nevertheless, there was no significant difference in the estimated mineralization efficiency of soil microbes among the habitat types. The results of structural equation modeling showed that N‐mineralization gene abundance played a major role in regulating SON mineralization. Although less than 20% of the SON was estimated to be labile/semi‐labile, SON mineralization was important in sustaining soil N2O production, with 5.8% of the mineralized N being fed into N2O production. Overall, our findings showed that the presence of S. alterniflora increased both SON content and mineralization rate, which would in turn promote further proliferation of this exotic plant along the coast. The conversion of S. alterniflora marshes to APs partially mitigated the positive effects of exotic plant invasion on SON turnover.