Environmental forensic characterization of former rail yard soils located adjacent to the Statue of Liberty in the New York/New Jersey harbor

Effects of different fertilization methods on Lolium multiflorum Lam. growth and bacterial community in waste slag

Waste slag has low nutrient content, so it has insufficient nutrient cycling and transformation in the soil ecosystem. There are few studies on the application of oligotrophic phosphate-solubilizing bacteria and phosphate (P) fertilizer to improve the properties of waste slags. In this study, three oligotrophic bacterial strains with P solubilizing activity, namely, Bacillus subtilis 2C (7.23 μg/mL), Bacillus subtilis 6C (4.07 μg/mL), and Bacillus safensis 2N (5.05 μg/mL), were isolated from waste slags. In the pot experiment, compared with no application of P fertilizer, inoculation of Bacillus subtilis 2C with a 50% recommended dose of P fertilizer significantly increased the available phosphorus (AP), total phosphorus (TP), and total nitrogen (TN) in slag by 33.16%, 76.70%, and 233.33%, respectively. The N, P uptake and fresh weight of Lolium multiflorum Lam. were significantly improved by 114.15%, 139.02%, and 100%, respectively. The analysis of the bacterial community showed that the application of P fertilizer decreased the diversity and richness of the bacterial community, and with the addition of phosphorus fertilizer and Bacillus subtilis 2C, the bacterial community in the slag developed towards eutrophication. Redundancy analysis (RDA) showed that the TP content in the slag was significantly correlated with the bacterial community (P = 0.001, < 0.01), followed by the TN content. This study on different P fertilizer application methods can provide some basic ideas for improving the performance of waste slag.

Mycorrhizal Infection Can Ameliorate Abiotic Factors in Urban Soils

Once abandoned, urban and post-industrial lands can undergo a re-greening, the natural regeneration and succession that leads to surprisingly healthy plant communities, but this process is dependent upon microbial activity and the health of the parent soil. This study aimed to evaluate the effects of arbuscular mycorrhizal fungi (AMF) in facilitating plant production in post-industrial soils. In so doing, we helped to resolve the mechanism through which AMF ameliorate environmental stress in terrestrial plants. An experiment was established in which rye grass (Lolium perenne) was grown in two heavy metal-contaminated soils from an urban brownfield in New Jersey, USA, and one non-contaminated control soil. One set of the treatments received an AMF inoculum (four species in a commercial mix: Glomus intraradices, G. mosseae, G. etunicatum and G. aggregatum) and the other did not. Upon harvest, dried plant biomass, root/shoot ratio, AMF colonization, and extracellular soil phosphatase activity, a proxy for soil microbial functioning, were all measured. Plant biomass increased across all treatments inoculated with AMF, with a significantly higher average shoot and root mass compared to non-inoculated treatments. AMF colonization of the roots in contaminated soil was significantly higher than colonization in control soil, and the root/shoot ratio of plants in contaminated soils was also higher when colonized by AMF. Mycorrhizal infection may help plants to overcome the production limits of post-industrial soils as is seen here with increased infection and growth. The application of this mechanistic understanding to remediation and restoration strategies will improve soil health and plant production in urban environments.

Artificial root exudates restore microbial functioning in a metal contaminated, barren, inactive soil

Restoring enzyme function in barren, brownfield soils using green strategies can improve microbial functioning and enable phytoremediation. It is known that adding simple, readily metabolized substrates secreted by growing plant roots (root exudates) or a laboratory prepared solution of root exudates (artificial root exudates) can stimulate soil microbial function. It is not known whether and how well this strategy works in a contaminated, low functioning soil from an industrial barren site because contaminants in the barren soil might inhibit microbial survival and functioning, or the microbial community might not be adapted to functionally benefit from root exudates. The objective of this study was to determine whether artificial root exudates stimulate microbial function in a barren soil. We collected soils from a barren brownfield (25R) site and an adjacent vegetated brownfield site (25F), with low and high enzyme activities, respectively. We subjected both soils to three treatments: switchgrass (native to the site), artificial root exudates, and a combination of switchgrass and artificial root exudates. We measured enzymatic activity, plant growth, soil moisture, organic matter content, and easily extractable glomalin content over 205 days. By day 157, artificial root exudates increased the phosphatase activity by 9-fold in previously vegetated brownfield soil and by 351-fold in barren brownfield soil. When exudates were added to the barren soil, the plant shoot mass was higher (52.2 ± 2.5 mg) than when they were not (35.4 ± 3.6 mg). In both soils, adding artificial root exudates significantly increased the percent moisture, organic matter, and glomalin content. Treating contaminated, barren soil with artificial root exudates resulted in increased soil microbial function and improved soil properties that might promote a hospitable habitat to support vegetation in such extreme environments. Summary: We added artificial root exudates to stimulate enzymatic function in two contaminated soils. Plant shoot mass, soil percent moisture, glomalin content, and organic matter content significantly increased due to the addition of artificial root exudates to the study soils. Microbially-mediated phosphatase activity was established in a barren, previously inactive, polluted soil.

Multiple pollution sources unravelled by environmental forensics techniques and multivariate statistics

Industrial sites affected by anthropogenic contamination, both past and present-day, commonly have intricate pollutant patterns, and source discrimination can be thus highly challenging. To this goal, this paper presents a novel approach combining multivariate statistics and environmental forensic techniques. The efficiency of this methodology was exemplified in a severely polluted estuarine area (Avilés, Spain), where factor analysis and clustering were performed to identify sub-areas with distinct geochemical behaviour. Once six clusters were defined and a pollution index applied, forensic tools revealed that the As speciation, Pb isotopes, and PAHs molecular ratios were useful to categorise the cluster groups on the basis of distinct pollution sources: Zn-smelting, coaly particles and waste disposal. Overall, this methodology offers valuable insight into pollution sources identification, which can be extended to comparable scenarios of complexly polluted environmental compartments. The information gathered using this approach is also important for the planning of risk assessment procedures and potential remediation strategies.

Natural versus urban global soil organic carbon stocks: A meta-analysis

Increasingly, the human existence in urban environments is growing. In addition, anthropogenic activity has altered the global carbon (C) cycle and triggered climate change. Soil is the largest pool of organic C in terrestrial ecosystems, but its ability to retain and store C varies. As humans move forward to mitigate climate change, there is a growing need to understand the C storing capacity of soils and their interactions with factors like climate, vegetation or a footprint of human activity. Here, we constructed a meta-analysis which focused on 30 cm soil depth by collecting data from over 191 studies measuring soil organic carbon (SOC) stocks across natural, urban green space, and urban intensive habitats. We then compared the SOC data between different climatic zones, vegetation types, and anthropogenic influences with the human footprint index. The results indicate that SOC stocks in natural habitats (98.22 ± 49.10 Mg ha^-1) are significantly higher than those of urban green spaces (54.61 ± 22.02 Mg ha^-1) and urban intensive habitats (65.88 ± 35.27 Mg ha^-1). We find a significant and negative relationship between the human footprint and SOC stocks of natural habitats but not between the human footprint and either of the urban habitats. Urban intensive and urban green space habitat soils store less C than natural ones. However, when compared across climatic zones or vegetation types, the capacity of natural soils to store C is variable and vulnerable to human activity. Carbon storage in urban soils is likely limited by persistent and stable anthropogenic influences keeping variability low. This is most pronounced in urban green spaces where human management is high (i.e. a golf course) and SOC is low. A comprehensive understanding of C storage in soils is essential to land management and climate mitigation measures.

Organic petrographic evaluation of carbonaceous material in sediments of the Kinnickinnic River, Milwaukee, WI, U.S.A

This study examines the use of organic petrology techniques to quantify the amount of coal and carbonaceous combustion by-products (i.e., coke, coal tar/pitch, cenospheres) in sediments taken from the Kinnickinnic River adjacent to the former site of the Milwaukee Solvay Coke and Gas Company. These materials are of concern as contaminants like polycyclic aromatic hydrocarbons (PAHs) are known to readily adsorb to coal and combustion byproducts. Kinnickinnic River sediment samples (n = 36) ranging in depth (1-11 ft.) were collected from eight core locations to quantify and characterize carbonaceous material in the sediments. To determine the amount (vol%) of organic particulates, U.S. Geological Survey (USGS) modified the existing ASTM D2799 using the following categories: coal, coke, coal tar/pitch, inertinite organics, plant material, cenospheres, and mineral matter. Coal fragments were subdivided by rank using vitrinite reflectance (R_o, %) and organic components were further subdivided into the size fractions of coarse (250-1000 μm), fine (63-250 μm), and very fine (<63 μm). Of the 36 samples analyzed, concentrations of coal, coke, and coal tar/pitch ranged from 0 to 18.2 vol%, 0 to 32.0 vol%, and 0 to 2.6 vol%, respectively, with the highest concentrations occurring near point sources (e.g. discharge pipe and coal unloading operations). Samples that were furthest upstream and downstream from the Solvay site exhibited a marked decrease in particulate organics, with exception of one upstream location which had 19.8 vol% coke. Overall, the modified ASTM method provided a means to quantify the abundance of carbonaceous material present in the sediments. Petrography and total PAH concentrations did not provide a clear correlation to organic matter type or size fraction but the samples with the highest vol% organic matter in each core generally corresponded to the sample with the highest bulk PAH content.

Soil as a tool of revelation in forensic science: a review

Soil contains diverse and complex natural elements having physical, chemical, mineralogical and biological components. Soil being a transferable physical component (it can be transferred from one location to another with the help of shoes, tires, clothes, tools etc.), acts as a tool of forensic investigation to correlate a specific crime scene with criminal suspects. A variety of techniques and combinations of methods can be used to discriminate soil from different geographical locations. The present review highlights various analytical techniques (ATR-FTIR, pyGC-MS, SEM-EDX, ICP-MS/OES and XRD) for soil analysis (colour comparison, texture and particle size determination, density gradient methods and organic matter estimation) and discusses some of the famous cases solved with soil trace evidence. The objective of the present study is to provide an overview of the importance of soil as physical evidence in forensic science based on literature analysis that will help forensic scientists and researchers to select appropriate methods to discriminate different soil samples. This article reviews various analytical techniques used to differentiate soils and provides compiled information regarding soil as trace evidence in order to help academicians, researchers and forensic soil scientists.

Benzo[a]pyrene sourcing and abundance in a coal region in transition reveals historical pollution, rendering soil screening levels impractical

Benzo[a]pyrene (BaP) is a hazardous compound for human health and for environmental compartments. Its transfer and deposition through the atmosphere affects soil quality. In this context, we quantified the content of BaP and other Polycyclic Aromatic Hydrocarbons (PAHs) in the soils of a prominent Coal Region in Transition to test whether the soil screening levels in force are realistic and whether they reflect the complexity of regions closely linked to heavy industries and mining. In this regard, soil screening levels are thresholds often established without considering historical anthropogenic activities that affect soil (diffuse pollution). The 150 soil samples studied showed a notable content of high molecular weight PAHs, and BaP surpassed the threshold levels in practically the entire area. PAH-parent diagrams revealed a relatively homogenous fingerprint of four clusters obtained in a multivariate statistical study. In addition, molecular diagnostic ratios pointed to coal combustion as the main pollution source, whereas only some outliers appeared to be related to specific spills. A BaP threshold was calculated to be 0.24 mg kg^-1, over 10 times the limit established in Spain. Finally, a factor analysis revealed a positive correlation of BaP with elements usually emitted in coal combustion processes, such as Tl and V. This observation fosters the hypothesis of a historical and indelible pollution fingerprint in soils whose sources, characteristics and potential environmental and health concerns deserve further attention. All things considered, caution should be taken when using soil screening levels in regions associated with coal exploitation and heavy industry.

Plants mitigate restrictions to phosphatase activity in metal contaminated soils

Soil anthropogenic contaminants can limit enzymatic nutrient mineralization, either by direct regulation or via impacts on the microbial community, thus affecting plant growth in agricultural and non-agricultural soils. The impact on phosphatase activity of mixing two contaminated, post-industrial rail yard soils was investigated; one was vegetated and had high phosphatase function, the other was barren and had low enzymatic function. The two soils had different abiotic properties, including contaminant load, vegetation cover, soil aggregate size distribution, and phosphatase potential. An experimental gradient was established between the two soils to systematically vary the abiotic properties and microbial community composition of the two soils, creating a gradient of novel ecosystems. The time dependence of extracellular phosphatase activity, soil moisture, and organic matter content was assessed along this gradient in the presence and absence of plants. Initially, mixtures with higher percentages of functional, vegetated soil had higher phosphatase activities. Phosphatase activity remained unchanged through time (65 days) in all soil mixtures in unplanted pots, but it increased in planted pots. For example, in the presence of plants, phosphatase activity increased from 0.6 ± 0.1 to 2.4 ± 0.3 μmol•h^-1•g_{dry soil}^-1 from day one to day 65 in the 1:1 functional:barren soil mixture. The presence of plants also promoted moisture retention. Inoculation of poorly functioning soil with 10% of the functional soil with its microbial community did not, over 65 days, revitalize the poorly functioning soil. The findings showed that abiotic limitations to enzymatic activity in barren brownfield soils could be mitigated by establishing primary production but not by the addition of enzymatically active microbial communities alone.

A multi-faceted, environmental forensic characterization of a paradigmatic brownfield polluted by hazardous waste containing Hg, As, PAHs and dioxins

Hg and As mining-metallurgy plants have severely impacted environmental compartments. La Soterraña site (northern Spain) has been previously studied in this context. However, here we used a novel multi-purpose forensic approach to examine accumulations not only of mining-metallurgical waste (volumes above 80,000 t) but also C&D waste as a repository of pollutants (above 10% of As leached in standard tests) at this site. High Hg and As content in very fine grain-size fractions (up to 100,000 mg/kg of As in metallurgy waste below 10 μm) was significant, as was the predominance of As (III) in metallurgy waste. In addition, GC-MS techniques revealed the predominance of PAHs (secondarily Oxy-PAHs and PCBs), which showed a pyrogenic fingerprint, as determined by molecular ratios. Moreover, toxic organometallics (Hg-aromatics) were detected and metallurgy waste was identified as a source of dioxins and furanes (TEQ close to 30). On the basis of our observations, La Soterraña emerges as one of the most polluted sites in Europe and therefore requires urgent remediation. Our key findings indicate that C&D waste should be considered hazardous. Metallurgy waste, in turn, raises maximum concern given the simultaneous presence of toxic inorganic and organic contaminants.