Experimental simulation of nitrogen and phosphorus release during marine dumping of dredged sediment

Abstract

Marine dumping of dredged sediment results in the release of considerable amounts of nitrogen and phosphorus into the seawater. In this study, we evaluated the release pattern of nitrogen and phosphorus during sediment dumping through experimental simulation under different mixing ratios and temperatures. The concentration of NO3-N, PO4-P, and total phosphorus (TP) in seawater quickly increased in less than 1 h after mixing of sediment and seawater and remained stable thereafter. The concentration of NH4-N increased and peaked at 0.25 h, but quickly decreased thereafter. The concentration of NO3-N, NH4-N, PO4-P, and TP in seawater showed a positive correlation with the mixing ratio. The contribution of NO2-N from sediment to water was negligible and there was no obvious difference in the release amount among different mixing ratios. The release amount of each measured nutrient at 25°C was marginally higher than that at 15°C, suggesting that marine dredging and dumping should be performed in winter rather than in summer. The release amount of NO3-N, NO2-N, NH4-N, PO4-P, and TP in a 5000-m3 vessel reached 26.5, 17.6, 0.28, 1.68, and 1.68 kg, respectively. This study provides a detailed evaluation of nitrogen and phosphorus release pattern in marine sediment dumping process, which will be helpful for the conservation and selection of marine dumping areas.

Análise Espaço-Temporal da Pluma de Dispersão dos Sedimentos Dragados do Porto de Maceió, Alagoas

“…O MPS é constituído por partículas inorgânicas (sedimento) e elementos biogênicos (matéria orgânica dissolvida e particulada) em suspensão na água. Essas partículas possuem a capacidade de inibir ou enriquecer os ecossistemas costeiros, fixar ou adsorver poluentes de metal, produtos químicos ou de origem orgânica, podendo causar eutrofização e a degradação de habitats marinhos biologicamente produtivos (Fathollahzadeh et al, 2015;Song et al, 2016;Yu et al, 2017;Liu et al, 2019;Fonseca et al, 2020). Entre outras consequências estão a elevação da turbidez, da sedimentação e a diminuição de oxigênio dissolvido na água (Cesar et al, 2014;Falcão Filho et al, 2016;Caballero et al, 2018).…”

Effects of Lake Erie dredged material on microbiomes in a farm soil of northwestern Ohio

“…Dumping them back into the lake away from the ship channels was the standard practice. However, this practice carries tremendous environmental risks because it could interrupt local ecosystems and release high levels of nutrients into the water, posing a threat to water quality (Hull & Associates Inc., 2018; W. Liu et al., 2019; Moog et al., 2018). Consequently, open‐lake disposal has been banned by Ohio Laws since July 1, 2020 (Ohio Revised Code, 2015).…”

Assessing the effects of lake‐dredged sediments on soil health: Agricultural and environmental implications for northwestern Ohio

“…The Toledo Port, Ohio is dredged annually, and nearly 1 million tons of dredged sediments are disposed into the open waters of Lake Erie (OEPA, 2020; USACE, 2009). Open lake‐dredged sediment disposal poses a threat to the water quality by resuspending sediment, creating an immediate increase in the total suspended sediment and nutrient concentrations and lowering dissolved oxygen levels (Li et al., 2009; Liu et al., 2019; Moog et al., 2018). The total amount of N and P released to the water column can be nearly 50 kg (110 lbs.)…”

“…The total amount of N and P released to the water column can be nearly 50 kg (110 lbs.) per load from a hopper dredger having a capacity of 5,000 m 3 (6,540 yd 3 ) (Liu et al., 2019). An Ohio State Senate Bill, effective as of July 2020, prohibits the open water dumping of dredged material and recommends finding alternative beneficial uses (Gardner & Peterson, 2015).…”