Salt Marshes as Groundwater Buffers for Development: A Survey of South Carolina Salt Marsh Basins

Salt marshes serve as zones of intense groundwater mixing and reaction between freshwater uplands and estuaries. This raises the question of whether the impacts of upland development on nutrient and carbon species can be transmitted through salt marshes via groundwater, or whether salt marshes can buffer estuarine waters from coastal development. We sampled groundwater from fifteen tidal creek basins in South Carolina to test for compositional differences associated with development and marsh width. Groundwater samples from near creekbanks and below freshwater uplands were analyzed for salinity, total dissolved nitrogen and phosphorus, and dissolved organic carbon. Analyses revealed significantly higher TDN and TDP concentrations in creekbank samples from developed watersheds, independent of the season. Analyses of upland samples revealed significantly lower DOC concentrations in developed uplands, again independent of season. These results support the hypothesis that development can affect groundwater compositions in coastal groundwater and therefore may affect coastal nutrient and carbon fluxes. However, results also revealed significant linear correlations between marsh width, salinity, and nutrient concentrations in some marshes. These results suggest that salt marshes can act as buffers for development, and specifically suggests that the buffering capacity of salt marshes increases with width. Narrow or trenched salt marshes are far less likely to be effective buffers.

Novel AOPs-Based Dual-Environmental Digestion Method for Determination of Total Dissolved Nitrogen in Water

Based on a synergistic digestion method of ultraviolet combined with ozone (UV/O3), this article investigates the reaction characteristics of nitrogen-containing compounds (N-compounds) in water and the influence of ions on digestion efficiency. In this respect, a novel and efficient AOPs-based dual-environmental digestion method for the determination of total dissolved nitrogen (TDN) in waters with complex components is proposed, in the hopes of improving the detection efficiency and accuracy of total nitrogen via online monitoring. The results show that inorganic and organic N-compounds have higher conversion rates in alkaline and acidic conditions, respectively. Meanwhile, the experimental results on the influence of Cl−, CO32−, and HCO3− on the digestion process indicate that Cl− can convert to radical reactive halogen species (RHS) in order to promote digestion efficiency, but CO32− and HCO3− cause a cyclic reaction consuming numerous •OH, weakening the digestion efficiency. Ultimately, to verify the effectiveness of this novel digestion method, total dissolved nitrogen samples containing ammonium chloride, urea, and glycine in different proportions were digested under the optimal conditions: flow rate, 0.6 L/min; reaction temperature, 40 °C; pH in acidic conditions, 2; digestion time in acidic condition, 10 min; pH in alkaline conditions, 11; digestion time in alkaline conditions, 10 min. The conversion rate (CR) of samples varied from 93.23% to 98.64%; the mean CR was greater than 95.30%. This novel and efficient digestion method represents a potential alternative for the digestion of N-compounds in the routine analysis or online monitoring of water quality.

Do zebra mussels (dreissena polymorpha) alter the water chemistry in a way that favours Microcystis

Many factors may contribute to cyanobacterial bloom formation. This study examined possible relationships between the presence of zebra mussels (Dreissena polymorpha) and Microcystis spp. abundance. Experiments were conducted in twelve microcosms designed to mimic shallow lake ecosystems. Zebra mussels significantly reduced nitrate, dissolved organic nitrogen, and total dissolved nitrogen concentrations, and had no effect on ammonia, phosphate levels, or dissolved organic carbon. Consequently, the N:P ratio was reduced in microcosms with zebra mussels to 6:1, which is below the Redfield ration of 16:1. Zebra mussels also increased the abundance of Microcystis and Microcystis: Pseudokirchneriella biovolume. In experiments done without zebra mussels, nutrient ratios were manipulated and low N:P caused a similar increase in Microcystis and Microcystis: Pseudokirchneriella biovolume. The shift in N:P in the presence of zebra mussels were related to higher rates of nitrate flux into sediments and reduced flux of phosphate into sediments. It is this shift in N:P, and possibly some level of selective feeding, that is believed to have driven changes in the relative abundance of Microcystis. Finally, in order to compare the experimental results with changes caused by zebra mussel invasion in the natural environment, the data from 15 Wisconsin lakes before and after the zebra mussel invasions were analysed.

Do zebra mussels (dreissena polymorpha) alter the water chemistry in a way that favours Microcystis

Many factors may contribute to cyanobacterial bloom formation. This study examined possible relationships between the presence of zebra mussels (Dreissena polymorpha) and Microcystis spp. abundance. Experiments were conducted in twelve microcosms designed to mimic shallow lake ecosystems. Zebra mussels significantly reduced nitrate, dissolved organic nitrogen, and total dissolved nitrogen concentrations, and had no effect on ammonia, phosphate levels, or dissolved organic carbon. Consequently, the N:P ratio was reduced in microcosms with zebra mussels to 6:1, which is below the Redfield ration of 16:1. Zebra mussels also increased the abundance of Microcystis and Microcystis: Pseudokirchneriella biovolume. In experiments done without zebra mussels, nutrient ratios were manipulated and low N:P caused a similar increase in Microcystis and Microcystis: Pseudokirchneriella biovolume. The shift in N:P in the presence of zebra mussels were related to higher rates of nitrate flux into sediments and reduced flux of phosphate into sediments. It is this shift in N:P, and possibly some level of selective feeding, that is believed to have driven changes in the relative abundance of Microcystis. Finally, in order to compare the experimental results with changes caused by zebra mussel invasion in the natural environment, the data from 15 Wisconsin lakes before and after the zebra mussel invasions were analysed.

Water quality measurements in Buzzards Bay by the Buzzards Bay Coalition Baywatchers Program from 1992 to 2018

The Buzzards Bay Coalition’s Baywatchers Monitoring Program (Baywatchers) collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers documents nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality.

Seasonal variation of nitrogen biogeochemical processes constrained by nitrate dual isotopes in cascade reservoirs, Southwestern China

<p>The increase of affected river reaches by reservoirs has drastically disturbed the original hydrological conditions, and subsequently influenced the nutrient biogeochemistry in the aquatic system, particularly in the cascade reservoir system. To understand the seasonal variation of nitrogen (N) behaviors in cascade reservoirs, hydrochemistry and nitrate dual isotopes (δ<sup>15</sup>N-NO<sub>3</sub><sup>− </sup>and<sup></sup>δ<sup>18</sup>O-NO<sub>3</sub><sup>−</sup>) were conducted in a karst watershed (Wujiang River) in southwest China. The results showed that NO<sub>3</sub><sup>−</sup>–N accounted for almost 90% of the total dissolved nitrogen (TDN) concentration with high average concentration 3.8 ± 0.4 mg/L among four cascade reservoirs. Higher N concentration (4.0 ± 0.8 mg/L) and larger longitudinal variation were observed in summer than in other seasons. The relationship between the variation of NO<sub>3</sub><sup>−</sup>–N and dual isotopes in the profiles demonstrated that nitrification was dominated transformation, while assimilation contributed significantly in the epilimnion during spring and summer. The high dissolved oxygen concentration in the present cascade reservoirs system prevented the occurrence of N depletion processes in most of the reservoirs. Denitrification occurred in the oldest reservoir during winter with a rate ranging from 18 % to 28 %. The long-term record of surface water TDN concentration in reservoirs demonstrated an increase from 2.0 to 3.6 mg/L during the past two decades (~ 0.1 mg/L per year). The seasonal nitrate isotopic signature and continuously increased fertilizer application demonstrated that chemical fertilizer contribution significantly influenced NO<sub>3</sub><sup>−</sup>–N concentration in the karst cascade reservoirs. The research highlighted that the notable N increase in karst cascade reservoirs could influence the aquatic health in the region and further investigations were required.</p>

Enriched Co-Treatment of Pharmaceutical and Acidic Metal-Containing Wastewater with Nano Zero-Valent Iron

Among traditional hazardous waste sources, pharmaceutical-containing wastewater and acidic mine drainage need treatment to preserve the expected water supply quality. A nano zero-valent iron (nZVI)-enriched treatment of these two streams is evaluated for simultaneous removal of various heavy metal ions, organic pollutants, sulfates, the efficiency of the treatment system, and separation of reaction products in the fluidized-bed reactor. The reactor packed with silica sand was inoculated with sludge from an anaerobic digester, then 1–3 g/L of nZVI slurry added to cotreat a hospital feed and acid mine wastewater at 5:2 v/v. The biotreatment process is monitored through an oxidation–reduction potential (Eh) for 90 days. The removal pathway for the nZVI used co-precipitation, sorption, and reduction. The removal load for Zn and Mn was approximately 198 mg Zn/g Fe and 207 mg Mn/g Fe, correspondingly; achieving sulfate (removal efficiency of 94% and organic matter i.e., chemical oxygen demand (COD), biological oxygen demand (BOD), dissolved organic carbon (DOC), total dissolved nitrogen (TDN) reduced significantly, but ibuprofen and naproxen achieved 31% and 27% removal, respectively. This enriched cotreatment system exhibited a high reducing condition in the reactor, as confirmed by Eh; hence, the nZVI was dosed only a few times in biotreatment duration, demonstrating a cost-effective system.

Impacts of the aquaculture on the distribution of dissolved organic matter in the coastal Jeju Island, Korea, revealed by absorption and fluorescence spectroscopy

To demonstrate behavior of dissolved organic matter (DOM) derived from coastal aquaculture, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), chromophoric dissolved organic matter (CDOM), and fluorescent dissolved organic matter (FDOM) were measured around the coastal Jeju Island, Korea. As reported by previous studies, pristine groundwater with extremely depleted DOC (< 30 µM) has been used as culturing water in the coastal aquafarms. However, the concentration of DOC within 1.5 km from the discharge outlet of the aquafarms was approximately two times higher than that in the groundwater. In addition, the concentration of TDN exponentially increased close to the discharge outlet. These distribution patterns indicate the aquafarm is a significant DOM source. Herein, principal component analysis including the absorption coefficient (a350), spectral slope coefficient (S250 − 600), specific UV absorbance (SUVA254), and five fluorescent components were applied to categorize DOM origins. We found two distinct groups: aquaculture activity for TDN with high molecular weights and natural biological activity for DOC enrichment. Our study has also critical implications for the efficient monitoring of anthropogenic organic pollutant from aquafarms using unique optical signals.