Efficient Removal of Nickel from Wastewater Using Copper Sulfate-Ammonia Complex Modified Activated Carbon: Adsorption Performance and Mechanism.

The necessity to eliminate nickel (Ni) from wastewater stems from its environmental and health hazards. To enhance the Ni adsorption capacity, this research applied a copper sulfate-ammonia complex (tetraamminecopper (II) sulfate monohydrate, [Cu(NH3)4]SO4·H2O) as a modifying agent for a Phragmites australis-based activated carbon preparation. The physiochemical properties of powdered activated carbon (PAC) and a modified form ([Cu(NH3)4]-PAC) were examined by measuring their surface areas, analyzing their elemental composition, and using Boehm's titration method. Batch experiments were conducted to investigate the impact of various factors, such as Ni(II) concentration, contact time, pH, and ionic strength, on its substance adsorption capabilities. Additionally, the adsorption mechanisms of Ni(II) onto activated carbon were elucidated via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The findings indicated that modified activated carbon ([Cu(NH3)4]-PAC) exhibited a lower surface area and total volume than the original activated carbon (PAC). The modification of PAC enhanced its surface's relative oxygen and nitrogen content, indicating the incorporation of functional groups containing these elements. Furthermore, the modified activated carbon, [Cu(NH3)4]-PAC, exhibited superior adsorption capacity relative to unmodified PAC. Both adsorbents' adsorption behaviors conformed to the Langmuir model and the pseudo-second-order kinetics model. The Ni(II) removal efficiency of PAC and [Cu(NH3)4]-PAC diminished progressively with rising ionic strength. Modified activated carbon [Cu(NH3)4]-PAC demonstrated notable pH buffering and adaptability. The adsorption mechanism for Ni(II) on activated carbon involves surface complexation, cation exchange, and electrostatic interaction. This research presents a cost-efficient preparation technique for preparing activated carbon with enhanced Ni(II) removal capabilities from wastewater and elucidates its underlying adsorption mechanisms.

Impacts of shipyard oil leakage on the PAHs and PCBs occurrence in Xiangshan Bay, China.

Here, we studied the shipyard impacts on the distribution of PAHs and PCBs in the semi-enclosed Xiangshan Bay, an important mariculture zone in China. The results showed that the shipyard caused a pollution plume for PAHs but not for PCBs. As characteristic pollutants of oil leakage, the PAHs had concentrations of up to 55.82 ng L-1 in the water, 2235.04 ng g-1 in suspended particulate matter (SPM), and 1489.60 ng g-1 in sediment. The PAHs in water and SPM were dominated by phenanthrene and pyrene that were mostly derived from lubricant and diesel, while those in sediments were dominated by the high-molecular-weight PAHs, such as indeno[1,2,3-c,d]pyrene. In contrast, the PCBs concentrations reached up to 10.17 ng L-1, 79.72 ng g-1, and 124.33 ng g-1 in the seawater, SPM, and sediment samples, respectively, and they did not show spatial patterns affected by the shipyard. Moreover, the health risk assessment indicated that the shipyard discharge caused a substantial PAHs ecological risk to the adjacent and downstream water environment. Therefore, point source discharge in semi-enclosed bays should be paid close attention to due to the strong pollutant transport effect.

Impacts of terrestrial input on the distribution characteristics of microplastics in the East China Sea characterized by chromophoric dissolved organic matter (CDOM) analysis.

Large quantities of microplastics are found in the East China Sea (ECS), however, the impacts of complicated terrestrial input on the distribution characteristics of microplastics have not been studied. Hence, we aimed to characterize the microplastic distribution in the ECS combined with the fluorescence characteristics of chromophoric dissolved organic matter (CDOM), a sensitive technique to trace terrestrial substances in seawater. The average microplastic abundance in the surface seawater of ECS was 34.73 ± 4.05 items/m3 and sites in the north ECS had a higher microplastic abundance (55.90 ± 2.47 items/m3) than those in the southern region (11.22 ± 4.01 items/m3), due to its proximity to the Yangtze River estuary and Hangzhou Bay. Polyethylene (PE, 44.2 %) was the most abundant microplastic type in the northern region, whereas polyethylene terephthalate (PET, 28.4 %) had a higher proportion in the south ECS. Besides, sites in the north ECS had a higher diversity index of microplastics, suggesting various sources of microplastic pollution. Interestingly, a stronger correlation with the diversity index was found for protein-like component C3 (R2 = 0.56) in northern regions compared to fulvic-like component C1 (R2 = 0.32) and humic-like component C2 (R2 = 0.28), suggesting the significant impact of anthropogenic discharge. Moreover, no correlation between fluorescence components and microplastic diversity index was found in the south ECS, indicating that CDOM can reflect the impact range of terrestrial input on the distribution characteristics of microplastics. This research might be useful in assessing and reducing the impact of terrestrial input on the distribution characteristics of microplastics in the ECS.

Kinetic and mechanistic insights into the degradation of clofibric acid in saline wastewater by Co2+/PMS process: a modeling and theoretical study.

Recently, the degradation of non-chlorinated organic pollutants in saline pharmaceutical wastewater by SO4˙--based advanced oxidation processes (AOPs) has received widespread attention. However, little is known about the oxidation of chlorinated compounds in SO4˙--based AOPs. This study chose clofibric acid (CA) as a chlorinated pollutant model; the oxidation kinetics and mechanistic pathway were explored in the Co2+/peroxymonosulfate (PMS) system. Notably, a high removal efficiency (81.0%) but low mineralization rate (9.15%) of CA within 120 min were observed at pH 3.0 during Co2+/PMS treatment. Exogenic Cl- had a dual effect (inhibitory then promoting) on CA degradation. Several undesirable chlorinated by-products were formed in the Co2+/PMS system. This demonstrated endogenic chlorine and exogenic Cl- both reacted with SO4˙- to generate chlorine radicals, which participated in the dechlorination and rechlorination of CA and its by-products. Furthermore, SO4˙- was the dominant species responsible for CA degradation at low Cl- concentrations (≤1 mM), whereas Cl2˙- was the predominant radical at [Cl-]0 > 1 mM. A possible degradation pathway of CA was proposed. Our findings suggested that chlorinated compounds in highly saline pharmaceutical wastewater will be more resistant and deserve more attention.

Effects of different treatment processes in four municipal wastewater treatment plants on the transport and fate of microplastics.

The behavior of microplastics in wastewater treatment plants has been investigated, but specific effects of treatment process on microplastics' fate are still unclear due to varied analysis methods and regional differences. In this study, four wastewater treatment plants in Ningbo of southeastern China with different treatment processes were selected to investigate transport and fate of microplastics. Based on number of microplastic particles, fibers and fragments were the main microplastics types in wastewater, while synthetic cellulose represented the largest fraction. The dominance of fibers (76.7%-90.0%) and small particle sizes (<2.0 mm, 62.5%-81.5%) in effluents suggested that they escaped easily from the wastewater treatment plants. The abundance of microplastics particles decreased from 78.0 ± 2.9 items/L in influent to 6.0 ± 2.8 items/L in effluent for anaerobic-anoxic-oxic process, 100.0 ± 3.1 items/L to 4.3 ± 3.4 items/L for sequencing batch reactor activated sludge process, 105.0 ± 5.3 items/L to 3.5 ± 2.6 items/L for cyclic activated sludge technology, 65.0 ± 4.3 items/L to 3.0 ± 1.6 items/L for oxidation ditch process. The microplastics removal capacity of primary and secondary treatment processes for four wastewater treatment plants ranged from 83.7% to 96.3%. Application of different tertiary treatment processes (coagulation/flocculation, membrane related technology and disinfection) enhanced microplastics removal to achieve overall removal rate of 92.3%-96.7%. The removed microplastics from the wastewater treatment plants were mainly transferred to sludge (226.1 ± 95.7-896.0 ± 144.0 items/g dry weight). The biological treatment unit played an important role in microplastics removal with rates varying between 86.9%-95.2%, while tertiary treatment reduced daily microplastics emission 1.4 × 108-2.3 × 108 items/day. This study suggests that proper selection of wastewater treatment unit could significantly reduce the emission number of microplastics, which supports an efficient control strategy of microplastics in wastewater treatment plants.

Impacts of haze on the photobleaching of chromophoric dissolved organic matter in surface water.

Sunlight plays an important role in the photochemical processes of chromophoric dissolved organic matter (CDOM), which is closely related to water self-purification and primary productivity of healthy aquatic ecosystem health. The fine particles of haze, a widespread air pollutant, absorb natural ultraviolet (UV) irradiation and have an unknown degree of influence on the photochemical transformation of CDOM. Here, an in-situ experiment investigating how the amount and composition of CDOM changes under hazy conditions was conducted in Ningbo, southeastern China, a city that frequently suffers from seasonal haze pollution. The results indicated that haze attenuated UV light under different weather conditions. The UV intensities were reduced from 1124.90 ± 91.58 to 510.26 ± 40.26 µW cm-2 and 748.54 ± 101.68 to 316.32 ± 40.48 µW cm-2 on sunny and cloudy days, respectively; these values approached those on rainy days (186.97 ± 28.58 µW cm-2). Consequently, the loss of dissolved organic carbon during the irradiation test was reduced on hazy days (e.g., from 5.63% to 2.59% on sunny/hazy days). The impact of haze on CDOM photobleaching was further assessed by an excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis. On hazy days, the EEM-PARAFAC components were saved from photobleaching to different degrees; and humic-like substances showed a stronger protective effect from haze than protein-like substances because of their higher photosensitivity. Consequently, haze could cause more terrestrial CDOM to remain in surface water. UV intensity played a critical role in the composition characteristics of CDOM. This study identifies the linkage between atmospheric pollution and water quality and demonstrates that long-term and large-scale haze may adversely influence aquatic ecology through pollutant/nutrient accumulation.

A combined radical and non-radical oxidation processes for efficient degradation of Acid Orange 7 in the homogeneous Cu(II)/PMS system: important role of chloride.

Trace copper ion (Cu(II)) in water and wastewater can trigger peroxymonosulfate (PMS) activation to oxidize organic compounds, but it only works under alkaline conditions. In this work, we found that the presence of chloride could significantly accelerate the oxidation of Acid Orange 7 (AO7) by the Cu(II)/PMS process at a wide pH range (4.0-9.0). The observed pseudo-first-order rate constant k for AO7 oxidation was linearly correlated with the increased Cl- concentration (0-300 mM). An increase in mineralization rate was observed in the presence of Cl-, while the overall mineralization was quite low. Decomposition of PMS facilitated when Cl- concentration or pH value increased. Based on the scavenger experiments and electron paramagnetic resonance (EPR) measurement, the mechanism of Cu(II)-catalyzed PMS oxidation process in the presence of Cl- was proposed as both the radical and non-radical pathway, and 1O2 was the reactive oxygen species in the Cu(II)/PMS system. Finally, a possible degradation pathway of AO7 was elucidated. The feasibility of in situ utilizing high salinity and trace cupric species to accelerate the degradation of organic pollutants by the Cu(II)/PMS process in water and wastewater was demonstrated. However, the identification of undesired chlorinated by-products reminds us of cautiousness in assessing the application of Cu(II)/PMS system under chloride-rich environment. The findings of this work provide a simple and efficient approach to apply PMS in the remediation of refractory organic contaminants in the presence of trace cupric species under a high salinity environment with a wide range of pH.

Degradation and chlorination mechanism of fumaric acid based on SO4•-: an experimental and theoretical study.

It is well known that chloride ions could affect the oxidation kinetics and mechanism of contaminant based on SO4•- in the wastewater. Here, the degradation of an organic acid, fumaric acid (FA), was investigated in the presence of chloride (0-300 mM) by the Fe(II)/peroxymonosulfate (Fe(II)/PMS) system. A negative impact of chloride was observed on the rates of FA degradation. The degree of inhibitory effect was higher in Fe(II)/PMS addition order. Some chlorinated byproducts were identified during the FA oxidation process in the presence of Cl- by the ultraperformance liquid chromatography and quadrupole-time of flight mass spectrometer (UPLC-QTOF-MS). With the increasing content of Cl-, an accumulation of adsorbable organic halogen (AOX), an increase in acute toxicity, and an inhibition of mineralization were observed. According to the results of kinetic modeling, the production and transformation of oxidative species were dependent on Cl- dosage and reaction time. SO4•- was supposed to be the main radical for FA degradation with Cl- concentration below 5 mM, whereas Cl2•- was primarily responsible for the depletion of FA at [Cl-] > 5 mM. A possible degradation pathway of FA was discussed. This study reveals the potential environmental risk of organic acid and is necessary to explore useful strategies for ameliorating the treatment of chloride-rich wastewater.

Spatiotemporal variations in chromophoric dissolved organic matter (CDOM) in a mixed land-use river: Implications for surface water restoration.

A challenge for current surface water restoration and management in China is acquiring the source information for complex pollution scenarios in order to develop effective control strategies. As an important part of dissolved organic matter, chromophoric dissolved organic matter (CDOM) contains unique chemical signals related to various pollution sources. Spectral methods such as fluorescence excitation-emission matrices coupled with parallel factor analysis enable rapid and low-cost CDOM characterization for source tracking. In this study, a typical small-sized river flowing through mixed land-use regions in southeastern China, the Lujiang River, was investigated to determine the responses of CDOM to spatiotemporal factors. The effects of land-use patterns were reflected by the fluorescent components of terrestrial and sewage substances. A high and stable proportion of terrestrial-like components (C1 + C2) in each sampling period (i.e., March: 47.6 ± 5.7% and October: 44.3 ± 2.7%) indicated a high input of non-point source (NPS) pollution from both agriculture and urban areas. In addition, the difference in solar radiation intensity induced by climate and air quality changes was also reflected by variability in the photodegradation product component (C3) of terrestrial precursors between October (24.8 ± 2.6%) and March (4.5 ± 2.0%), suggesting that terrestrial components could be a sensitive indicator for NPS pollutant monitoring. Increased sewage impact in downstream regions was reflected by a spike in the tryptophan-like component (C4); temporal variations in C4 (paired t-Test, p < 0.005) also indicated that sewage substances were more prone to removal by microbial activity in warmer seasons. The dynamics of C4 could serve as a good indicator of sewage disposal performance. The results of this study demonstrate that CDOM data have important practical applications for existing water restoration campaigns in southeastern China, as well as substantial potential for routine water quality monitoring.

Multiple roles of Ca2+ in the interaction of ciprofloxacin with activated sludge: Spectroscopic investigations of extracellular polymeric substances.

Calcium ion is an important cation influencing the binding of recalcitrant organic contaminants with activated sludge during wastewater treatment process, but there is still unknown about its role in amphoteric fluoroquinolones binding. Binding experiments show that Ca2+ markedly inhibited binding of ciprofloxacin (CIP) onto sludge, causing 7-203 times of CIP release. Multi-spectroscopic examinations indicate that tryptophan-like and tyrosine-like proteins in extracellular polymeric substances (EPS) were dominant components for CIP binding by static quenching and forming CIP-proteins complexes. Addition of Ca2+ into EPS and CIP binding systems induced increase of association constants (from 0.024-0.064 to 0.027-0.084 L/µmol) and binding constants (from 0.002-0.039 to 0.012-0.107) and decrease of binding sites number (from 0.893-2.007 to 0.721-1.386). Functional groups of EPS and secondary structure of proteins were remarkably changed upon reactions with CIP and Ca2+. Calcium ion interacted with EPS and CIP binding system in two distinct ways: Ca2+ shielded CO in amide I in EPS for CIP binding, whereas strengthened binding between CIP and functional groups including CO in carboxyl groups in extra-microcolony polymers and OH in extra-cellular polymers by forming ternary complexes. Cation competition for CO in amide I is responsible for Ca2+ induced CIP release from the sludge. Results suggest the highly potential release of CIP from high saline wastewater and cation-conditioned sludge which needs further monitoring and evaluation.

How biofilms affect the uptake and fate of hydrophobic organic compounds (HOCs) in microplastic: Insights from an In situ study of Xiangshan Bay, China.

Microplastic (MP) has been identified as an emerging vector that transports hydrophobic organic compounds (HOCs) across aquatic environments due to its hydrophobic surfaces and small size. However, it is also recognized that environmental factors affect MP's chemical vector effects and that attached biofilms could play a major role, although the specific mechanisms remain unclear. To explore this issue, an in situ experiment was conducted at Xiangshan Bay of southeastern China, and dynamics of HOCs (i.e., polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs)) and bacterial communities related to the model MP (i.e., PE fibers) were analyzed and compared. Through bacterial characterizations including the 16S rRNA approach, higher summer temperatures (31.4 ± 1.07 °C) were found to promote colonizing bacterial assemblages with larger biomasses, higher activity and more degrading bacteria than winter temperatures (13.3 ± 2.49 °C). Consequently, some sorbed pollutants underwent significant decline in the summer, and this decline was particularly the case for PAHs with low (2-3 rings) and median (4 rings) molecular weights such as phenanthrene (59.4 ± 1.6%), chrysene (70.6 ± 4.2%), fluoranthene (77.1 ± 13.3%) and benz[a]anthracene (71.5 ± 11.0%). In our winter test, however, most pollutants underwent a consistent increase throughout the 8-week exposure period. Moreover, more biorefractory pollutants including PCBs and high molecular weight (5-6 rings) PAHs accumulated regardless of bacterial characteristics. Two putative PAH-degrading bacteria appeared with high relative abundances during the summer test, i.e., family Rhodobacteraceae (18.6 ± 0.5%) and genus Sphingomicrobium (22.4 ± 3.6%), associated with drastic decreases in low (45.2 ± 0.4%) and median (66.0 ± 2.5%) molecular weight PAHs, respectively. Bacterial degradation effects of biofilms on PAHs are also supported by the correlative dynamics of salicylic acid, an important degradation intermediate of PAHs. The results of this study indicate that MP's HOC vector effects are essentially determined by interactions between attached pollutants and microbial assemblages, which are further related to bacterial activity and pollutant features. Further studies of biofilm effects on MP toxicity and on the metabolic pathways of MP-attached HOCs are required.

Fluorescence characteristics and biodegradability of dissolved organic matter (DOM) leached from non-point sources in southeastern China.

Under the increasingly intensive measures for surface water restoration in China, point source discharge has been strictly regulated; however, for non-point sources, which constitute a large part of surface water pollutants, effective control has been difficult to reach. A comprehensive understanding of the characteristics of non-point source pollutants is essential for surface water improvement programs of cities such as Ningbo, on the southeast coast of China. Ningbo has made tremendous efforts in the past few years to control point source pollutants, but available data and management strategies on the non-point source pollutants are still limited. To this end, leachates of representative non-point source samples from the territory of Ningbo, including cropland and wetland soil, urban channel sediment, and poultry manure, were examined and compared focusing on the fluorescence characteristics and biodegradability of the dissolved organic matter (DOM). Results indicated that biodegradable dissolved organic carbon (BDOC) accounting for the total DOC was 46.7 ± 0.7% for cropland, wetland (56.3 ± 6.8%), non-sewage channel (60.1 ± 0.4%), sewage channel (74.5 ± 1.1%), and poultry manure (62.7 ± 4.5%). The leachates of the studied samples showed significant differences in both the amount and composition of DOM. However, a fluorescence component representing tryptophan-like substances identified by the excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis effectively predicted the BDOC variations among the studied samples. Moreover, under the studied nutrient concentrations, which were equivalent to Grade III water quality in China, nutrient limitation of microbial degradation was not observed. Threats to water quality, especially excessive consumption of dissolved oxygen, could be posed by the non-point source leachates due to their high bioavailability, large distribution, and weak nutrient restraint. Further investigations, including a quantitative evaluation of the non-point source pollution contribution, and pollutant blocking techniques are required.

[Analysis of the Relationship Between Dissolved Organic Matter (DOM) and Watershed Land-use Based on Three-dimensional Fluorescence-Parallel Factor (EEM-PARAFAC) Analysis].

Dissolved organic matter (DOM) is a characteristic index of water quality, and reflects many factors, such as the economic development and protection policies of watershed. In this study, surface water samples were collected from four watersheds with different levels of urbanization in Ningbo. The DOM was analyzed using an excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) to explore the relationship between land-use and DOM. The results show that the urbanization level affected both the amount and the composition of the DOM in the studied watersheds. The concentrations of DOM evaluated by dissolved organic carbon (DOC) in urban areas (DOC=3.18 mg·L-1) and an urban-rural combined area (DOC=7.45 mg·L-1) were much higher than those in rural areas with low urbanization (DOC between 2.16 and 2.62 mg·L-1, ANOVA, P<0.001). A total of seven PARAFAC components were identified in the studied watersheds, mainly including humic-like and protein-like substances. In the highly urbanized area, DOM was mainly composed of humic-like substances, with a proportion of 61.3%. However, the water samples from the urban-rural combined area exhibited a high proportion (59.4%) of protein-like substances, indicating a strong influence of sewage and industrial discharge. In contrast, although the DOM amounts in rural areas were relatively low, the proportions of humus-like substances were high, ranging from 63.6% to 65.7%. Agricultural non-point sources were the main contributor to DOM in these areas. Moreover, the results suggest that the urbanization process could intensify the damage to the surface waters. At the initial stage of urbanization (i.e., urban-rural combined area), contaminants are mainly discharged from sewage and industrial sources; when urbanization reaches a certain level, e.g., with a well-constructed sewage collection system, water contaminants originate more from surface runoff rather than sewage. The results of this study suggest that the EEM-PARAFAC technique can provide semi-quantitative source tracking of surface water, as well as an inexpensive and effective tool for policy makers to overcome the insensitivity of general water quality indices.

Microplastics and associated PAHs in surface water from the Feilaixia Reservoir in the Beijiang River, China.

Microplastics have been a prevalent and persistent contamination problem in the global aquatic environment. In particular, microplastics that can adsorb persistent organic pollutants (POPs) and therefore transfer these POPs to organisms in the aquatic environment have received much attention. In this study, an investigation of microplastics in the surface water of the Feilaixia Reservoir (Guangdong Province, China), which is an important part of people's daily lives in Guangdong Province was carried out, mainly focusing on the characteristics and spatial distribution of microplastics, as well as microplastics and their adsorded PAHs in the surface water of the Feilaixia Reservoir were investigated. The average abundance of microplastics in the surface water of the Feilaixia Reservoir was 0.56 ±â€¯0.45 items/m3. Six kinds of polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), expanded polystyrene (EPS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET), were identified, among which PP (52.31%) and PE (27.39%) were the major compositions. Four shapes of microplastics, i.e., foams, films, fragments and fibers were found, and films (37.78%) being the main shape. The most common typical size of the plastic particles ranged from 0.6 to 2 mm (41.36%). The total concentration of the sixteen PAHs carried on the EPS, PE and PP microplastics ranged from 282.4 to 427.3 ng/g; chrysene, benzo [ghi] perylene, and phenanthrene were abundant in the samples, at concentrations of 39.5-89.6 ng/g, 34.6-56.8 ng/g and 25.6-45.6 ng/g, respectively. Based on the ratios of the PAH isomers (Flut/Py < 1 and Phe/Ant >10), it was speculated that the source of the PAHs may be derived from the imperfect combustion of fossil fuels.

Assessment of microplastics derived from mariculture in Xiangshan Bay, China.

Mariculture activities including enclosure, raft and cage cultures employ a variety of plastic gear such as fishing nets, buoyant material and net cages. The plastic gear poses a potential source of microplastics to the coastal environment, but relevant data on the impacts of mariculture are still limited. To this end, a semi-enclosed narrow bay (i.e., Xiangshan Bay, China) with a long-term mariculture history was investigated to assess how mariculture activities affect microplastics in seawater and sediment. The results indicated that mariculture-derived microplastics accounted for approximately 55.7% and 36.8% of the microplastics in seawater and sediment, respectively. The average microplastic abundances of seawater and sediment were 8.9 ±â€¯4.7 (mean ±â€¯SD, n = 18) items/m3 seawater and 1739 ±â€¯2153 (n = 18) items/kg sediment, respectively. The types of mariculture-derived microplastics included polyethylene (PE) foam, PE nets, PE film, polypropylene (PP) rope, polystyrene (PS) foam and rubber. PE foam had the highest proportion (38.6%) in the seawater samples. High usage rates and the porous structure of PE foam led to the high abundance. The average microplastic sizes of seawater and sediment are 1.54 ±â€¯1.53 mm and 1.33 ±â€¯1.69 mm, respectively. The spatial variations in the abundance and size of microplastics implied that the mariculture-derived microplastics in Xiangshan Bay were transported along the Bay to the open sea. The results of this study indicate that mariculture activity can be a significant source of microplastics. Further research is required to investigate how the high microplastic abundance in mariculture zone affects marine organisms, especially cultured seafood.

Sorption behaviors of phenanthrene on the microplastics identified in a mariculture farm in Xiangshan Bay, southeastern China.

Recently, with the accumulation of evidence that microplastic can be ingested by a variety of marine organisms, microplastic sorption behaviors towards organic contaminants (OCs) have become the subject of more studies due to the concerns about the contaminant vector effect. In this study, the priority microplastics identified in a mariculture farm in Xiangshan Bay, China, including polyethylene (PE) and nylon fibers (i.e., derived from new fishing ropes and nets), were examined for their sorption behaviors. The results indicate that both plastic fibers show linear isotherms towards phenanthrene, a common target hydrophobic organic contaminant (HOC), revealing the characteristics of a partitioning mechanism. The sorption capacity of PE fiber was found to be 1-2 orders of magnitude higher (evaluated by Freundlich parameter log KF) than that of nylon fiber, suggesting the importance of plastic surface functional groups (i.e., with or without hydrophilic groups). By comparing carbon normalized log KF with literature data, the organic affinity of PE fiber was found to be 1-2 orders of magnitude lower than that of vectors, such as carbonaceous geosorbents (CG), but was 1-2 orders of magnitude higher than that of marine sediments. Small size and rough surface tended to enhance the sorption of plastic fibers of phenanthrene. In addition, phenol (log KOW: 1.46), a low-hydrophobicity compound, showed approximately 3 orders of magnitude lower sorption amounts onto both fibers compared to phenanthrene (log KOW: 4.46), indicating the selectivity of hydrophobicity. The results of this study demonstrate that the high abundance of plastic fibers distributed in mariculture farms could lead to a higher contaminant transfer effect than marine sediments, and their effects on cultured seafood (e.g., crab and fish) need further investigation.

Impacts of land-use on surface waters at the watershed scale in southeastern China: Insight from fluorescence excitation-emission matrix and PARAFAC.

In recent years, the Chinese government has strengthened its efforts in surface water protection and restoration through strict policies and heavy investments. A clear understanding of the impacts of land use on water quality is necessary in order to ensure an effective and efficient implementation of the ongoing surface water restoration program in China. To this end, four small watersheds (less than 5000 ha) in southeastern China, which have clear gradients in the intensities of agriculture (17.0-45.4%), forest (35.2-73.6%) and built-up area (3.3-8.5%), were investigated regarding the impacts of land use on water quality. In addition to the general water quality indices, characteristic components derived by fluorescence excitation-emission matrices (FEEMs) coupled with parallel factor analysis (PARAFAC) were employed to explore a more accurate association between land use and water quality. The results show that agricultural intensity has significant effects by elevating the concentrations of dissolved organic carbon (DOC, an approximate six-fold increase) and total phosphorous (TP, an approximate four-fold increase) in the surface waters. A total of five PARAFAC components representing terrestrial (three components) and protein-like (two components) substances were identified. The PARAFAC results indicate that land-use patterns affected the dissolved organic matter (DOM) in the aspects of both amount and composition. The intensity (R.U.) of the terrestrial components showed a strong correlation (r2 = 0.95, p = 0.01) with agricultural land percentage. Moreover, although the proportion of built-up area varies with a relatively small range, a protein-like component could predict its impact with excellent sensitivity (r2 = 0.94, p = 0.02), whereas the general water quality indices were incapable of predicting the impact due to their multiple sources. The results of this study demonstrate that the FEEMs-PARAFAC technique provides an inexpensive and effective tool for policy makers to overcome the insensitivity of general water quality indices, particularly for the restoration of watersheds with complex land-use patterns.

Occurrence and distribution of microplastics at selected coastal sites along the southeastern United States.

To investigate the occurrence and distribution of microplastics in the southeastern coastal region of the United States, we quantified the amount of microplastics in sand samples from multiple coastal sites and developed a predictive model to understand the drift of plastics via ocean currents. Sand samples from eighteen National Park Service (NPS) beaches in the Southeastern Region were collected and microplastics were isolated from each sample. Microplastic counts were compared among sites and local geography was used to make inferences about sources and modes of distribution. Samples were analyzed to identify the composition of particles using Fourier transform infrared spectroscopy (FTIR). To predict the spatiotemporal distribution and movements of particles via coastal currents, a Regional Ocean Modeling System (ROMS) was applied. Microplastics were detected in each of the sampled sites although abundance among sites was highly variable. Approximately half of the samples were dominated by thread-like and fibrous materials as opposed to beads and particles. Results of FTIR suggested that 24% consisted of polyethylene terephthalate (PET), while about 68% of the fibers tested were composed of man-made cellulosic materials such as rayon. Based on published studies examining sources of microplastics, the shape of the particles found here (mostly fibers) and the presence of PET, we infer the source of microplastics in coastal areas is mainly from urban areas, such as wastewater discharge, rather than breakdown of larger marine debris drifting in the ocean. Local geographic features, e.g., the nearness of sites to large rivers and urbanized areas, explain variance in amount of microplastics among sites. Additionally, the distribution of simulated particles is explained by ocean current patterns; computer simulations were correlated with field observations, reinforcing the idea that ocean currents can be a good predictor of the fate and distribution of microplastics at the sites sampled here.

Distribution and fate modeling of 4-nonylphenol, 4-t-octylphenol, and bisphenol A in the Yong River of China.

In this study, the concentrations of 4-nonylphenol (4-NP), 4-tert-octylphenol (4-t-OP), and bisphenol A (BPA) in the water column of the Yong River were investigated and found to be in the range of 140-3948, 6-828, and 15-1415 ng L-1, respectively. A fate and transport model coupled with the Water Quality Analysis Simulation Program (WASP) was developed. After model calibration and validation, the distributions of 4-NP, 4-t-OP, and BPA in the Yong River were modeled for the duration of 2015. The total contaminant loads from the upstream boundary, four tributaries and two wastewater treatment plants were determined to be 2318 kg yr-1 for 4-NP, 506 kg yr-1 for 4-t-OP, and 970 kg yr-1 for BPA. Both measured and modeled results reported higher concentrations of the selected contaminants near river confluences and at the outfalls of the wastewater treatment plants. Peak concentrations were found to always appear in months with relatively reduced precipitation. The influences of adsorption and degradation on the dissolved concentrations of the selected chemicals were also modeled. The combined effects of adsorption and degradation were found to reduce dissolved concentrations of 4-NP, 4-t-OP, and BPA by 17.9%, 30.7%, and 12.1%, respectively. Adsorption was shown to reduce 4-NP concentrations in the Yong River more than degradation. Conversely, adsorption and degradation caused almost equal reductions in the dissolved concentrations of 4-t-OP and degradation caused larger decreases than adsorption in the dissolved concentrations of BPA.

Occurrence of microplastics in the beach sand of the Chinese inner sea: the Bohai Sea.

The occurrence of microplastics in the beach sand of the Bohai Sea was investigated for the first time. The Bohai Sea is the largest Chinese inner sea and its coastal region is one of the most densely urbanized and industrialized zones of China. Samples from three costal sites (i.e., Bijianshan, Xingcheng and Dongdaihe) were collected, quantified and identified for microplastic analysis. Effects of sample depth and tourism activity were investigated. Surface samples (2 cm) contained higher microplastic concentrations than deep samples (20 cm). Samples from the bathing beach exhibited higher microplastic concentrations than the non-bathing beach, suggesting the direct contribution of microplastics from tourism activity. Of eight types of microplastics that were found, PEVA (polyethylene vinyl acetate), LDPE (light density polyethylene) and PS (polystyrene) were the largest in abundances. Moreover, the non-plastic items from samples were analyzed and results revealed that the majority abundance of the observed non-plastics were viscose cellulose fibers. Further studies are required to evaluate the environmental hazards of microplastics, especially as they may "act as a contaminant transporter" to the Bohai Sea ecosystem.