Chapter Ten. Chapter Eleven. Chapter Twelve. Chapter Thirteen. Chapter Fourteen. Chapter Fifteen. Chapter Sixteen. Chapter Seventeen. Chapter Eighteen. The sixth and penultimate book in the New York Times bestselling I Am Number Four series! For years the Garde have fought the Mogadorians in secret. Now all . The Fate of Ten by Pittacus Lore, , available at Book Depository with free delivery worldwide.
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Read the first two chapters of the penultimate book in the Lorien Legacies (you know, that I Am Number Four series), The Fate of Ten. In the. The sixth and penultimate book of the #1 New York Times bestselling I Am Number Four series! For years the Garde have fought the Mogadorians in secret, but. The Fall of Five, The Revenge of Seven, The Fate of Ten and United as One. The Little Prince by Antoine de Saint-Exupéry (epub, pdf).
Furthermore, parameters for heteroaggregation are still poorly known, which also calls for further refinement. The study is framed as purely theoretical as empirical data on microplastic emissions and concentrations were not available. The model is based on an existing hydrobiogeochemical multimedia model, INCA-contaminants [ 93 ], with a sediment transport module [ 95 ], a rainfall-runoff module [ 94 ], and the possibility to add direct effluent inputs from, for instance, WWTPs. It is a lumped model as it assumes homogeneous rainfall and temperature distributions.
The model accounted for surface runoff and effluent inputs and reentrance to the system by resuspension.
Whether particles are transported by surface runoff depended on the microplastic pool available for mobilization, the transport capacity of the overland flow both for microplastics and sediment, and the detachment of plastics through splash erosion and flow erosion.
In the stream, the particles are assumed to be uniformly mixed within each section, and the transport processes advection, settling, and size-dependent resuspension from the sediment bed were taken into account.
Microplastic properties were defined by dimension and density. The study assumed plastic particles were pristine, that is, effects of biofouling were not taken into account. The transport dynamics were more influenced by size than by density, which confirms the findings by Besseling et al.
The particle size range of the simulated particles was 0. The model did not include biofouling, aggregation, or fragmentation.
These processes influence the hydrodynamic behavior and size distribution of the particles but according to the authors should be better understood before they can be included in the model. Nanoparticles are also not included in the model yet [ 37 ]. The NanoDUFLOW model seems more complete as it includes aggregation, which has been shown to be a crucial process, especially for submicron particles [ 59 , 60 ]. The model by Besseling et al. Given the study aim, Besseling et al. This difference can be explained from the fact that NanoDUFLOW accounted for aggregation of these small plastic particles, which allowed for the simulation of the increased sedimentation of these small plastic particles captured in heteroaggregates.
This emphasizes the need to include this process. It has been shown that because heteroaggregation captures virtually all free nanosized particles, uncertainty with respect to the exact parameterization of heteroaggregation is of minor importance [ 73 , 96 , ].
Also laboratory experiments have shown that processes like biofouling and aggregation [ 57 , 62 , 84 ] and particle properties like density, size, and shape [ 52 , 55 ] significantly influence particle fate. Quality assurance criteria are common in analytical chemistry or ecotoxicology [ , ] but are less self-evident for monitoring of plastic debris which is a relatively young field of science [ ].
There also is an urgent need to standardize the units used to quantify abundance of plastic debris [ 81 ].
For instance, for freshwater systems, concentrations of plastics in water and sediment have until now been reported in mass per unit of volume of water [ 13 ], mass per mass of sediment [ 15 ], particles per volume of water [ 13 , 19 ], particles per surface area of water [ 18 , 19 , 83 , ], and particles per mass of sediment [ 15 ]. Utility of data for modeling would improve enormously if studies would at least mention both mass and particle count data and, when taking water samples, mention the sampling depth and sampling net dimensions, which would enable a surface-to-volume conversion or vice versa.
This conversion only holds under the assumption that particles are evenly distributed over the sampled depth, which is also often assumed in models. Depending on the aims of the modeling, measured plastic abundances should meet specific requirements. To validate mass flow analysis, an estimate of the total mass of plastic per unit of volume of the modeled media would be required.
Because the latter models start with emission data, i. For deterministic spatiotemporally explicit modeling, sufficient detail with respect to actual size and polymer density distributions is required because such approaches aim to simulate the reality as closely as possible.
This implies that analysis and characterization of plastic in environmental samples would need to include a sufficient detail in the particle size and density distributions and b sufficient detail in the classification of shape, i.
Given that particle interactions as well as potential ecological effects across different species traits are size dependent, standardization of methods, including those for nano- and micrometer-sized plastic particles, is considered very important. Recommendation for Model Validation Validation would require sufficient data to verify the credibility of the model with statistical rigor.
For mass flow or multimedia models, limited data per system yet for a high number of aquatic systems would be preferred. For spatiotemporally resolved models, however, it would be preferred to sample one catchment in detail.
Such a case study catchment could then be used to calibrate and validate models, which could later be applied to other catchments. As for process parameters, little is known yet especially about the time scales of aggregation, fragmentation, and biofouling.
This means that experimental work is needed, after which the parameter values obtained from these experiments can be applied in models. The development of fate models for freshwater may also benefit from experimental and model studies on marine plastic aggregation, fragmentation, and biofouling. In the previous sections, we described different categories of models in detail. Here, we briefly discuss what category of model is needed for which type of question or application.
In essence, this categorization does not differ from that for soluble chemicals or engineered nanomaterials. For emission-based regional estimates of environmental concentrations of plastic debris, mass balance, mass flow, and especially mechanistic multimedia models are adequate.
Recently, for nanoparticles such models have been developed, like the SB4N model [ 63 , 72 , 73 ] and the MendNano model [ ]. It is highly recommended that such mechanistic multimedia models are adapted for plastic as well.
Being neither temporal nor spatially explicit, such models are screening level models that can be used to assess relative concentrations among classes of nano- and microplastics or among plastic emission scenarios.
Hence, such models are useful to calculate regional average or background concentrations PECs, predicted environmental concentrations for different plastic types, for different regions, or for different future emission scenarios. Multimedia particle models can also be used to detect the parameters to which the model output is most sensitive or to quantify uncertainty in PECs, which than can be applied in probabilistic risk assessments discussed below.
Compared to the output provided by multimedia models, more realistic estimates of local environmental fate and concentrations can be obtained with spatiotemporally explicit models. However, fate models that are spatially explicit only yield better estimates if data on spatial variability in emission intensities are available.
At present, there is only limited information on such spatial variation. Global river models like Global NEWS link mass flow models for river catchments, which thus accounts for spatial variation among catchments on a global scale, but not within catchments [ 91 , ]. As for applications, such models can rank catchments, regions, countries, or continents with respect to emission intensity to the marine environment [ 92 ].
The multimedia model SB4N can also accommodate various spatial scales, like regional, continental, and global, but always calculates one average concentration for soil, sediment, air, lake, river, and seawater.
For more accurate local estimates of concentrations of plastic debris, system-specific zero-D mass balance approaches can be used for smaller systems, like lakes [ 63 ].
However, to better account for variability, spatiotemporally explicit models in 1, 2, or 3 dimensions can be used. By defining small segments in a river, full hydrology can be taken into account. It has been argued recently that such models may be able to predict biologically relevant nanoparticle aggregate species as a function of time and space, which in turn can be linked to exposure by biota inhabiting the water system in question [ 24 ].
We propose that a similar approach also is possible for plastic debris, although further validation of fate models as well as further assessment of what has to be considered bioavailable and ecologically relevant is required.
These last steps are particularly important when models are used in the framework of a formal risk assessment. Here, we postulate that for plastic debris the same basic components of ERA can be used as for traditional chemicals and engineered nanomaterials: problem definition stage, an exposure assessment, an effect assessment, and a risk characterization step [ , ].
For plastic debris, exposure presently is difficult to measure, so there is a relatively high need for modeling tools. For soluble chemicals, the ERM always is concentration, which is why ERA for chemicals uses the ecotoxicologically relevant concentration. Effect assessment and risk characterization are beyond the scope of this review, which focuses on freshwater models for fate and exposure see [ ] for details. However, in order to frame models in the context of ERA, here we briefly touch upon the wide variety of adverse outcome pathways AOPs that exists for plastic debris.
As plastic debris is a complex mixture of sizes, types, and shapes, which also can be associated with chemicals, there will be a multitude of ERMs. Each ERM captures the unique features of a particular type of debris present in a habitat in combination with specific traits of species in that habitat, leading to an AOP describing the preset ecological or human health protection goals.
ERMs for physical effect of plastic can be defined in the form of a matrix where exposure and effect criteria such as habitat, species, life stage, mode of action, plastic size, plastic shape, and exposure duration are tabulated and scored. Using population models, effects on individuals then can be integrated with those from other stressors and habitat factors and, where needed, scaled to the population level similar to pesticide effect models e.
Ideally, fate models as described in this review should thus be able to simulate or predict all relevant ERMs emerging from the broad suite of species and particles that can be encountered in a habitat that has to be protected. Here, as mentioned before, for relatively simple site or material prioritizations, regional background concentrations as produced by multimedia models may suffice.
Multimedia models can also be used in probabilistic ERA where spatial heterogeneity is accounted for by using a probability function that quantifies the spatial variation. Due to considerable uncertainty compared to ERA for traditional chemicals, probabilistic approaches are recommended, which can be adopted from recent developments in the ERA of engineered nanoparticles [ ].
In this review we argue that in order to conduct a proper risk assessment of plastic pollutants and their sources, and given the scarcity of data, models are useful complementary methods for exposure assessment. These models can build on existing transport models that simulate other types of particles, only changing the plastics-specific parameters and characteristics. As a material to model, plastic is unique given its wide range of sizes, shapes, and densities.
It can aggregate or fragment and obtain a biofilm, all of which influence the hydrodynamics and size distribution of the particles. The first models developed for plastic transport so far range from mass-balance point-emission models to spatiotemporally explicit models.
These models, however, have not yet been calibrated because of a lack of data.
We recommend that before large measurement campaigns start, units to express abundance of plastics and methods for the analysis of plastics in the environment are standardized, which would increase the usability of the measurements. References 1. Whether she is a friend or a foe, however, remains to be seen. Meanwhile, Six, Marina, and Adam are trapped in Mexico. They fought their way into the Sanctuary and were able to awaken the force hidden within, but they don't have any way to reach the others The Garde are stretched thin.
Their only shot at saving the world is to eliminate the Mogadorian leader once and for all—but his fate is now irrevocably tied with Ella's. The Garde can't destroy one without the other. And if they can't find another way to stop the Mogs, humanity will suffer the same fate as the Loric: Pittacus Lore is Lorien's ruling Elder. He has been on Earth preparing for the war that will decide Earth's fate. His whereabouts are unknown. We want your feedback!