Oil Spill Research Articles

Stranded heavy fuel oil exposure causes deformities, cardiac dysfunction, and oxidative stress in marine medaka Oryzias melastigma using an oiled-gravel-column system.

Heavy fuel oil (HFO) stranded on the coastline poses a potential threat to the health of marine fish after an oil spill. In this study, an oiled-gravel-column (OGC) system was established to investigate the toxic effects of stranded HFO on marine medaka Oryzias melastigma. HFO 380# (sulfur content 2.9%) was chosen as one type of high sulfur fuel oil for acute toxicity tests. The marine medaka larvae were exposed to the OGC system effluents with oil loading rates of 0 (control), 400, 800, 1600, and 3200µg HFO/g gravel for 144h, respectively. Results showed that a prevalence of blue sac disease signs presented teratogenic effects, including decreased circulation, ventricular stretch, cardiac hemorrhage, and pericardial edema. Moreover, the treatments (800, 1600, and 3200µg oil/g gravel) induced severe cardiotoxicity, characterized by significant bradycardia and reduced stroke volume with an overt decrease in cardiac output. Additionally, the antioxidant enzyme activities, including catalase (CAT), peroxidase (POD), and glutathione S-transferase (GST) were significantly upregulated at 800-3200µg oil/g gravel except for a marked inhibition of CAT activity at 3200µg oil/g gravel. Furthermore, significantly elevated protein carbonyl (PCO) levels were detected, suggesting that the organisms suffered severe protein oxidative damage subjected to the exposure. Overall, stranded HFO 380# exposure activated the antioxidant defense system (up-regulated POD and GST activities) of marine medaka and disrupted CAT activity, which could result in an oxidative stress state (elevated PCO levels) and might further contribute to cardiac dysfunction, deformities, and mortality.

Biosurfactants Used in the Bioremediation of Soils Contaminated With Hydrocarbons - Overview of the State of the Art and Future Perspectives.

The increasing industrialization and hydrocarbon use have led to concerning soil contamination. Oil spills and improper disposal of oily waste pose threats to ecosystems and human health. The recovery of these environments is essential, but separating oily components from soil remains challenging. Current bioremediation strategies using synthetic surfactants can cause secondary contamination. Microbial biosurfactants, which are biodegradable and low in toxicity, emerge as promising solutions, and this study reviews methods for utilizing these biosurfactants in the environmental bioremediation of hydrocarbons. This study explores the efficient and eco-friendly use of biosurfactants for hydrocarbon- contaminated soil management, providing a market-oriented analysis of recent patents and trends, and highlighting the transition from academic research to industrial applications. The methodology involves an extensive literature review, careful selection of recent studies and patents on biosurfactants in hydrocarbon bioremediation, critical analysis of in-situ and ex-situ application methods, assessment of commercial viability, and synthesis of findings to contribute to sustainable solutions in contaminated environments. The present study demonstrates the extensive applicability of biosurfactants across various industrial sectors. The increasing interest in incorporating biosurfactants into industrial processes is driven by the pressing need for sustainable solutions to address tangible market challenges. Notably, the cosmetics industry exhibited the highest number of patents related to the use of biosurfactants, underscoring its significant role in advancing the adoption of these environmentally friendly agents. This trend highlights the critical demand for sustainable alternatives in product formulations and underscores the pivotal role of biosurfactants in fostering eco-innovation within the industry.

Hydrocarbon metabolism and petroleum seepage as ecological and evolutionary drivers for Cycloclasticus.

Aqueous-soluble hydrocarbons dissolve into the ocean's interior and structure deep-sea microbial populations influenced by natural oil seeps and spills. n-Pentane is a seawater-soluble, volatile compound abundant in petroleum products and reservoirs and will partially partition to the deep-water column following release from the seafloor. In this study, we explore the ecology and niche partitioning of two free-living Cycloclasticus strains recovered from seawater incubations with n-pentane and distinguish them as an open ocean variant and a seep-proximal variant, each with distinct capabilities for hydrocarbon catabolism. Comparative metagenomic analysis indicates the variant more frequently observed further from natural seeps encodes more general pathways for hydrocarbon consumption, including short-chain alkanes, aromatics, and long-chain alkanes, and also possesses redox versatility in the form of respiratory nitrate reduction and thiosulfate oxidation; in contrast, the seep variant specializes in short-chain alkanes and relies strictly on oxygen as the terminal electron acceptor. Both variants observed in our work were dominant ecotypes of Cycloclasticus observed during the Deepwater Horizon disaster, a conclusion supported by 16S rRNA gene analysis and read-recruitment of sequences collected from the submerged oil plume during active flow. A comparative genomic analysis of Cycloclasticus across various ecosystems suggests distinct strategies for hydrocarbon transformations among each clade. Our findings suggest Cycloclasticus is a versatile and opportunistic consumer of hydrocarbons and may have a greater role in the cycling of sulfur and nitrogen, thus contributing broad ecological impact to various ecosystems globally.

Thriving in salty environments: Aspergillus niger's halotolerance and BTEX biodegradation potential.

Benzene, toluene, ethylbenzene, and xylene (BTEX) can be found in marine and estuarine waters due to accidental spills of oil and derivatives, as well as in production water and effluents discharged from petrochemical plants. Addressing the bioremediation of these compounds in saline environments and effluents with elevated salinity levels is imperative. In this study, the halotolerance of Aspergillus niger was assessed by subjecting it to a stepwise increase in salinity, achieved through progressive addition of NaCl from 2 to 30‰ (v/v). The fungal strain exhibited optimal growth support up to a salinity concentration of 25‰, accompanied by a biomass production rate of (0.93 ± 0.11) g.d-1. The adapted biomass was employed in batch reactors to evaluate the biodegradation of BTEX (1,500 mg.L-1). In the absence of sucrose, the reactors inoculated with fungi demonstrated almost complete BTEX removal within 7 days, with rates ranked as follows: benzene (1.12 d-1) > toluene (0.78 d-1) > ethylbenzene (0.65 d-1) > xylene (0.63 d-1). Enhanced BTEX removal rates were obtained in the presence of sucrose, notably with 2g.L-1: benzene (3.63 d-1) > toluene (2.10 d-1) > ethylbenzene (1.56 d-1) > xylene (1.50 d-1). Notably, benzene was found to be the sole compound adsorbed onto the fungal mycelium (1.50 ± 0.19) to (13.35 ± 4.72) mg.g-1 of biomass.

Inversion for offshore oil-water emulsion concentration based on a six-flux model of laser-induced fluorescence

Oil-water emulsions, as one of the momentous weathering forms of the marine oil-spill, have caused more severe detriment to the marine environment. Laser-induced fluorescence (LIF) is an extremely influential technique for monitoring spilled oil at sea. However, the evaluation of offshore oil-water emulsion concentration based on LIF detection technology has been rarely discussed. Simultaneously, a scientific low-flux model including fluorescence flux has not been established and applied to detect oil spill at sea. In view of this, a six-flux model of laser-induced fluorescence is proposed to invert the concentration of oil-water emulsions at sea. On the cornerstone of laser flux, fluorescence flux is introduced. Utilizing the absorption, scattering, and other characteristics of flux in the medium, differential equations of various flux are established, and the solution framework of the differential equations is afforded. Thereafter, a formula of the fluorescence radiation transfer factor of the oil-water emulsions and their concentration is derived. Furthermore, the validity and availability of the proposed model are proved by experiments. The experimental results reveal that the proposed model has high accuracy in inverting the concentrations for oil-water emulsions, and the average error is within 6%. Meanwhile, this model consumes a short time, not exceeding 60 s at most. Utilizing the model, the concentration of oil-water emulsions can be evaluated in real time.

Effect of oil and diesel fuel pollution on enzymatic activity of meadow chernozem-like soil

In the laboratory experiment, the effect of oil pollution on the short-term dynamics of the activity of urease, phosphatase, catalase, peroxidase and polyphenol oxidase of the chernozem soil of the south of the Far East was studied. It was found that when soil was contaminated with oil and petroleum products, urease activity decreased by 20–44% at the end of incubation, peroxidase activity increased by 39–49% in the middle and end of incubation, polyphenol oxidase activity increased 1.6–2.0 times in the middle of incubation. The activity of phosphatase and catalase was stable at different levels of contamination throughout the experiment. Examining the effect of the incubation period, it was found that the maximum activity of urease was on the 10th day, phosphatase – on the 20th, peroxidase – on the 20th and 30th, polyphenol oxidase – on the 30th day of the experiment. Catalase activity was stable throughout all incubation periods. It was shown that in the case of contamination of chernozem-like soil with oil and diesel fuel in doses up to 5000 mg/kg, inhibition of enzymatic activity did not occur in the early stages.

Design of Polarization Spectroscopy Integrated Imaging System

To simultaneously acquire the spectral and polarization information of the target and achieve the monitoring and identification of the target object, a polarization spectral integrated imaging system is proposed in this paper. Firstly, the structural principle of the polarization spectral integrated imaging system is introduced. The relationship between the spatial resolution, spectral resolution, and the system’s structural parameters is analyzed. The design of the optical part of the polarization spectral integrated imaging system is completed, along with the tolerance analysis. Secondly, the mechanical structure of the polarization spectral integrated imaging system is designed. Finally, by using a drone to carry the polarization spectral integrated imaging system, a simulation experiment for sea surface oil spill monitoring is conducted, and the hyperspectral and polarization information of the ocean, crude oil, fuel oil, palm oil, diesel, and gasoline are obtained. The polarization and spectral information were integrated. The integration of hyperspectral and polarization data yields remarkable enhancement outcomes, allowing for the clear delineation of previously challenging-to-identify crude oil contamination areas against the marine background in the fused images, characterized by sharper boundaries and improved discriminability. This accomplishment underscores the feasibility of our system for the rapid identification of large-scale oil spill events.

Predicting the drift of small cetaceans stranded along the Atlantic coast of the Iberian Peninsula: Parametrization of the MOTHY drift model.

Marine mammal populations, particularly the common dolphin Delphinus delphis in the North-East Atlantic, play an essential role as indicators of ecosystem health. Effective monitoring of these populations is essential for assessing anthropogenic impacts, especially in the context of current threats such as fisheries bycatch. The MOTHY drift model, initially designed for oil spills and then adapted to carcass drift, is being used in part of the North East Atlantic (Bay of Biscay, English Chanel, and North Sea) to estimate the bycatch mortality of common dolphins. This study presents the parametrization of the drift model to estimate the bycatch mortality of common dolphins in the Iberian Peninsula waters. By comparing the actual stranding location of tagged dolphin carcasses off the Galician coast with their stranding location predicted by the drift model, we determined the best setting for the environmental input parameters. The results reveal that a 4 arc-minutes bathymetry resolution, coupled with consideration for currents, optimally predicts stranding locations in the Iberian Peninsula coast. The model's accuracy in predicting stranding locations is 18.25 ± 14.77 km. This adaptation not only contributes to the ongoing assessment of the impacts of bycatch on common dolphin populations in the Iberian Peninsula, but also provides a standardized methodology for estimating bycatch mortality at the population level. This work can also be used as a basis for further applications for other small cetacean species in wider distribution areas, supporting comprehensive population-level assessments and management strategies.

Polyvinylidene Fluoride Nanofiber Murray Membrane for Quick Oil Absorption

With the rapid advancement of global industrialization, there is an increasing year-on-year demand for oil in society. The occurrence of oil spills during the processes of development, refining, and transportation has become an urgent issue that needs to be addressed. Electrospun fiber separation using selective oil/water absorption represents a relatively new yet promising technology. However, despite the lipophilic nature of the membrane for oil absorption, the rate of oil absorption is slow. There are still challenges in meeting the needs of developing communities. The plant employs a strategy of multi-branching with narrowed pores, which serves to enhance the efficiency of water and nutrient transfer. Inspired by plant transpiration, we adjusted the parameters of electrospinning and constructed a PVDF biomimetic nanofiber membrane with gradually reduced pore size through a bottom-up layer-by-layer spinning strategy. This PVDF biomimetic nanofiber membrane conforms to Murray's law. The experimental results showed that the oil absorption of carbon tetrachloride by PVDF Murray membrane was 3.06 g/g. Significantly, the PVDF Murray membrane demonstrates rapid adsorption of the oil slick (0.3 mL, n-hexane) in just 13s, as compared to 24s without the Murray structure. Therefore, the one-step preparation of the PVDF Murray membrane indicates a promising potential for its future application as a sustainable and quick oil-absorbent membrane.

Surfactant-Enhanced Spreading on Solids: Roles of the Surface Tension Gradient, Spreading Contact Angle, and Viscosity.

Despite its important technological applications, surfactant-enhanced (spontaneous) spreading on a solid surface and how to optimize it on surfaces with different wettabilities are not well understood. Spontaneous spreading involves a surface tension gradient (Marangoni stresses), which enhances spreading over a large area. Experimental observations reveal that the spreading rate and surfactant concentration have an optimum substrate wettability of 60 ± 5° (Hill, R. M. Curr. Opin. Colloid Interface Sci. 1998, 3, 247).This paper discusses why the optimum for surfactant-enhanced spreading requires an initial macroscopic three-phase contact angle of 60 ± 5°. An equation based on experimental evidence allows for the calculation of the surface tension gradient over time using data on the spreading rate, spreading macroscopic contact angle, and droplet spreading radius. This novel approach for estimating the surface tension gradient and explaining the optimum substrate wettability underscores the role of the surface tension gradient, viscosity, and substrate wettability in surfactant-enhanced spreading on solids. The roles of the spreading three-phase contact angle and surface tension gradient in surfactant-enhanced spreading were analyzed, demonstrating that the surface tension gradient contributes more significantly to the spreading rate than the contact angle. Fingering instability formation, an instability at the droplet spreading edge caused by the Marangoni stresses, also serves as evidence of the role that the surface tension gradient plays in surfactant-enhanced spreading. Furthermore, applications of surfactant-enhanced spreading were demonstrated, suggesting potential uses in oil spill removal, leaf pesticide delivery, and oil spill remediation. The goal of the proposed study is to use experimental evidence to develop a model for calculating the optimum spreading rate during the first several seconds of surfactant-enhanced spreading on a solid substrate.

Assessing socio-economic and natural vulnerability to oil spills: a case study of Azerbaijan’s Caspian shoreline

ABSTRACT This study addresses the environmental and socio-economic impacts of oil spills on the Caspian shoreline. Proactive ecological management must include diverse static and dynamic information to measure pollution’s environmental and human impacts. This study develops a hybrid environmental sensitivity index (ESI) map for Azerbaijan’s coast, integrating biological, socio-economic, and physical sensitivity data with historical risk measures. The ESI assists local and national managers to plan and improve response readiness to oil spills. The approach could also be applied across all Caspian littoral states, where increasing oil activities heighten risks in vulnerable areas.

A few-shot oil spill segmentation network guided by multi-scale feature similarity modeling

Segmentation of oil spills with few-shot samples using UAV optical and SAR images is crucial for enhancing the efficiency of oil spill monitoring. Current oil spill semantic segmentation predominantly relies on SAR images, rendering it relatively data-dependent. We propose a flexible and scalable few-shot oil spill segmentation network that transitions from UAV optical images to SAR images based on the image similarity of oil spill regions in both types of images. Specifically, we introduce an Adaptive Feature Enhancement Module (AFEM) between the support set branch and the query set branch. This module leverages the precise oil spill information from the UAV optical image support set to derive initial oil spill templates and subsequently refines and updates the query oil spill templates through training to guide the segmentation of SAR oil spills with limited samples. Additionally, to fully exploit information from both low and high-level features, we design a Feature Fusion Module (FFM) to merge these features. Finally, the experimental results demonstrate the effectiveness of our network in enhancing the performance of UAV optical-to-SAR oil spill segmentation with few samples. Notably, the SAR oil spill detection accuracy reaches 75.88% in 5-shot experiments, representing an average improvement of 5.3% over the optimal baseline model accuracy.

Ultrahigh-Resolution Mass Spectrometry Advances for Biogeochemical Analysis: From Seafloor Sediments to Petroleum and Marine Oil Spills.

This Perspective explores the transformative impact of ultrahigh-resolution mass spectrometry (UHR-MS), particularly Fourier transform ion cyclotron resonance (FT-ICR-MS), in the characterization of complex environmental and petroleum samples. UHR-MS has significantly advanced our ability to identify molecular formulas in complex mixtures, revolutionizing the study of biogeochemical processes and organic matter evolution on wide time scales. We start by briefly reviewing the main technological advances of UHR-MS in the context of petroleum and environmental applications, highlighting some of the challenges of the technology such as quantitation and structural identification. We then showcase a selection of impactful applications published in the last 20+ years. In the field of environmental lipidomics, high-resolution analysis of lipids in sediments enables multiproxy studies and provides novel insights into past environmental conditions. UHR-MS has also facilitated the characterization of kerogen, a complex, poorly soluble mixture formed from sedimented organic matter over geological time scales, and the identification of polar compounds within its fractions. In petroleum (geo)chemistry, UHR-MS has enabled the identification of biomarkers such as petroporphyrins, asphaltenes, and high-molecular-weight naphthenic acids, shedding light on the molecular complexity of crude oil. The application of UHR-MS in oil spill science has revealed significant molecular transformations during weathering processes, such as photo-oxidation, which are crucial for assessing the environmental impact of past spills and improving the preparedness for future spills. These advancements underscore the role of this maturing analytical technology in deepening our understanding of geochemical processes and biogeochemical cycles, highlighting its potential for future research directions in organic geochemistry.

Nutrient amendments enrich microbial hydrocarbon degradation metagenomic potential in freshwater coastal wetland microcosm experiments.

The impact of oil spills in a freshwater aquatic environment can pose dire social, economic, and ecological effects on the region. An oil spill in the Laurentian Great Lakes region has the potential to affect the drinking water of more than 30 million people. The light synthetic crude oil used in this experimental microcosm study is transported through an underground pipeline crossing the waterway between two Laurentian Great Lakes. This study collected metagenomic data (experiments in triplicate) and assessed the quantity of BTEX compounds, which connected microbial degradation function to gene potential. The resulting data documented the bioremediation capabilities of native microbes in a freshwater coastal wetland. This study also provided evidence for this region that bioremediation can be a viable remediation strategy instead of invasive physical methods.

Oil spill effects on seagrass ecosystems: a systematic review

Oil spill effects on seagrass ecosystems: a systematic review

Investigating Oil Entrance from Hendijan Oil Field in the Northwest of the Persian Gulf Using Chemical Fingerprinting.

Concerning the entrance of oil into the Persian Gulf due to the presence of oil fields in this ecosystem, a wide investigation was carried out in 2017 to evaluate the hydrocarbons source identification and chemical fingerprinting. To this end, surface sediments were collected from the Persian Gulf. In the laboratory, compounds (n-alkanes, PAHs, hopane and sterane) were then extracted with a Soxhlet system and two steps of chromatographic columns and analyzed using a GC-MS instrument. The results showed that the concentrations of the n-alkanes and Σ30 PAHs increased with a reduction in distance from hot spots. This suggests that high concentrations of hydrocarbons in the locations near the hot spots might be due to oil leakage, transportation of and exploration for oil, pipeline fractures and industrial activities. A positive relation between total organic matter (TOM) and hydrocarbons was observed. A common petrogenic hydrocarbon source was strongly implied in most places by the presence of unresolved compounds resolved (UCM), lower molecular weight/higher molecular weight (LMW/HMW) and carbon preference index (CPI) ratios < 1. Typical profiles of petrogenic PAHs with predominant alkyl substituted naphthalene and phenanthrene, various PAH ratios and multivariate analysis showed that PAHs were mainly derived from petrogenic sources. Simultaneous use of n-alkanes and PAHs in source identification can be effective to precisely specify the hydrocarbon sources in complicated mixture ecosystems. Furthermore, using multivariate analysis and chemical fingerprinting of n-alkanes, PAHs, hopanes and sterane confirmed that Hendijan crude oil may be the source of the sediment pollution in the study area.

Ultra-Antifouling Liquid-Like Surfaces for Sustainable Viscous Water-in-Oil Emulsions Separation and Oil Recovery.

The demand for efficient separation techniques in industries dealing with high viscosity emulsions has surged due to their widespread applications in various scenarios, including emulsion-based drug delivery systems, the removal of emulsified impurities in formulations and oil spill remediation. However, membrane fouling is a major challenge for conventional separation methods, leading to decreased efficiency and increased maintenance costs. Herein, a novel approach is reported by constructing liquid-like surfaces with double anti-fouling structure, incorporating soft nanomicelles within a rigid, chemically cross-linked network for both anti-membrane-fouling and effective viscous water-in-oil emulsion separation. The coating significantly outperforms perfluorinated and commercial polytetrafluoroethylene (PVDF) membranes, effectively preventing the adhesion of viscous oils like crude oil and pump oil, and alleviating severe membrane fouling. For high-viscosity emulsions (97.3 cP and 52.8 cP), it maintains over 99% separation efficiency after 3h continuous use. Even after 15h immersion in strong acids, alkalis, salts, or organic solvents, its separation efficiency remains above 95%. In addition, thanks to the anti-membrane-fouling ability, this work achieved 6h continuous emulsion separation performance for the first time, demonstrating unparalleled long-term stability. Overall, this study offers valuable insights into the development of innovative coatings for efficient and eco-friendly separation of high-viscosity emulsions.

Responses of fisheries ecosystems to marine heatwaves and other extreme events.

Marine ecosystems and their living marine resources (LMRs) continue to respond to the effects of global change, with environmental factors impacting marine fisheries biomass, distribution, harvest, and associated economic performance. Extreme events such as high-category hurricanes, harmful algal blooms, marine heatwaves, and large-scale hypoxia affect major regions and subregions of United States waters, with their frequency expected to increase over the next decades. The impacts of extreme events on fisheries biomass, harvest, and economic performance have not been examined as closely as a system (i.e., cumulatively), or in terms of their differential effects on particular functional groups of a given system. Among several U.S. subregions, we examined responses of fisheries biomass, landings, and revenue for particular functional groups to large-scale environmental perturbations (i.e., marine heatwaves, Hurricane Katrina, Deepwater Horizon oil spill). Distinct negative short-term consequences to annual fisheries biomass, landings, and revenue were observed in all regions, including at the system-level scale for several ecosystems which have higher proportions of pelagic species composition and variable shellfish-based revenue. In addition, shifts in species composition often were associated with environmental perturbations. Recovery to pre-perturbation levels (both in the immediate years following the event and over the post-event period of study) and resilience at the system level was observed in several cases, although post-event declines in biomass and landings occurred in the California ecosystem. Certain extreme events are expected to become more common in marine environments, with resulting perturbations throughout multiple components of U.S. socioecological systems. The recognition and understanding of the consequences of extreme events throughout marine ecosystems is necessary for effective, holistic, and sustainable management practices.

Verification of Construction Method for Smart Liners to Prevent Oil Spill Spread in Onshore

Onshore oil spills are directly related to soil contamination and significantly impact groundwater, vegetation, and human life. Immediate cleanup work is carried out when an oil spill occurs, but the currently used preventive measures are insufficient. Therefore, this study independently developed a smart liner that allows general groundwater flow but blocks groundwater in the event of a spill to prevent further spread, and aims to verify the excellence of the product through verification. Because the verification of the smart liner performance in real-life conditions is difficult for various reasons, large-scale experiments were simulated using a container. The Roll Spreading and Inserting Method (RSIM) and Panel Injecting Method (PIM) were used as installation methods due to the properties of the material employed. Through rainfall simulations, the discharge amount and groundwater levels before and after an oil spill were measured, and a reaction diagram was created following the smart liner’s demolition. From the results, it was found that both installation methods successfully blocked more than 99% of the drainage, and soil contaminants were not detected outside the installation area. These results confirm the effectiveness of the smart liner. Additionally, the reaction diagram indicated that the RSIM and PIM installation reaction areas were identical, validating the suitability of both methods. By conducting this study, the performance of the smart liner was verified, demonstrating its potential as an effective preventive measure against the spread of oil contamination in soil.

SR-SqueezeNet: A lightweight hyperspectral identification model for oil spills based on smoothed activation functions

The demand for real-time identification of oil spills in disaster emergency response is urgent, Unmanned Aerial Vehicles (UAVs) are important monitoring means for oil spills by advantage of their flexible, fast and low-cost, so it's crucial of developing lightweight model for UAVs. This paper proposed a lightweight hyperspectral identification model called SR-SqueezeNet, which based on SqueezeNet model and used the designed smooth-type activation function Smooth-ReLU. And this research conducted a series of experiments based on the multi-dimensional airborne images of the oil spills. The results show that SR-SqueezeNet performs the best in both model lightweighting and extraction accuracy. Compared with the traditional SqueezeNet, the identification accuracy is improved by 1.92 %, the number of parameters is reduced by 75.11 %, and the model size is reduced from 26.46 MB to 12.15 MB. Therefore, the SR-SqueezeNet model has potential ability in the practical needs of oil spill UAVs' lightweight detection.