Suspended Particulate Matter Concentrations Research Articles

Operational parameters impact on spatial and temporal distribution and multifractal characteristics of particulate matter concentration under the sink effect

The influences of different factors on spatial and temporal mass transfer mechanism and dynamic characteristics of particulate matter (PM) under the sink effect are not clear. The objective of this study was to quantitatively analyze the influences of operational parameters on spatial and temporal distribution and multifractal characteristics of indoor suspended PM concentration under the sink effect. Results showed that with the increase of the applied voltage of the purification device, the reverse increase processes of PM1 and PM2.5 concentrations were progressively attenuated, and PM10 and total suspended particulates (TSP) concentrations decreased clearly. The dynamic evolution processes of the PM concentration series all presented strong persistence and obeyed the scale-invariant power-law statistical distributions. The positive correlation of the PM concentration series between five distances increased with the increase of applied voltage. This study can provide a reference basis for further refining the PM purification theory system under the sink effect.

AMBIENT AIR QUALITY MONITORING SYSTEM IN COIMBATORE CITY

Air pollution is dispersion of the particulates, biological molecules, or other harmful materials into the Earth’s atmosphere. Industrialization and urbanization are the two major causes of deteriorating air quality of the major cities in Tamil Nadu, India. Coimbatore is the second and most important commercial and industrial city in India. These industrial activities can add significant levels of heavy metals in the atmosphere. So, regular surveillance and consistent monitoring and modelling of the city would be much imperative. To evaluate the ambient air quality in Coimbatore city the pollutants such as PM10, Suspended Particulate Matter (SPM) and Heavy metals (Cd, Cr, Cu, Pb, Fe, Ni and Zn) were monitored at four locations of the city in this project. The concentration of PM10, SPM and seven heavy metals in the ambient air were estimated and the contributions of various sources were evaluated. The concentration of PM10 and SPM were found to be within the permissible limit. The aim of the project is to develop models, the concentration details of PM10 (Particulate mass). The quality analyzed parameter were compared with the values given by National Ambient Air Quality Standards (NAAQS) Nearly 8 Places in Coimbatore City.

Adaptive optical algorithms with differentiation of water bodies based on varying composition of suspended particulate matter: A case study for estimating the particulate organic carbon concentration in the western Arctic seas

High complexity and variability in composition of water constituents pose major challenges for development of algorithms to estimate biogeochemical data products from optical observations over the continuum of diverse aquatic environments. To address these challenges, we examined an adaptive optical approach that accounts for variability in composition of suspended particulate matter. We use the ratio of particulate organic carbon to suspended particulate matter concentration, POC/SPM, for optically discriminating water bodies with varying proportions of organic and mineral particles. Through the analysis of field data from the western Arctic seas that exhibit a broad range of water composition and optical properties, we developed empirical algorithms to estimate SPM and POC/SPM either from the particulate inherent optical properties (IOPs) of seawater, i.e., the spectral particulate absorption ap(λ) or backscattering bbp(λ) coefficients, or directly from the spectral remote-sensing reflectance of the ocean, Rrs(λ). The capability to retrieve POC/SPM from optical measurements was used to formulate the particle composition-specific algorithms for estimating POC from particulate IOPs or Rrs(λ). The evaluation of algorithms with the development field dataset demonstrates that the algorithm formulations accounting for changes in POC/SPM provide significant improvements in POC estimates along the continuum of optically-complex Arctic waters compared with algorithms that do not account for variations in particulate composition, such as the current standard POC algorithm used for global satellite applications. The results of example application of the particle composition-specific algorithm and standard global algorithm to satellite observations are consistent with comparisons of these algorithms for our field dataset, which supports a conclusion that the standard algorithm tends to overestimate POC in Arctic waters that exhibit a broad range of particle composition. Although this study demonstrates the adaptive approach using data from the Arctic region, it has broader significance and is amenable to further enhancements by including other optically-derivable water constituent properties. Further validation analyses and efforts are needed towards a unified approach with improved representation of cause-and-effect relationships between water composition and optical properties to enable improved optically-based applications across a wide range of water bodies.

Heavy metal distribution in various environmental matrices and their risk assessment in Ganga River Basin, India

This study focuses on heavy metals distribution and their ecological risk in river water, bed sediment, and suspended particulate matter (SPM) along the Ganga River basin. Overall abundance of the metals followed the sequence, Fe > Al > Mn > Pb > Ni > Cd > Cr > Zn > Co in water, Al > Fe > Mn > Zn > Cr > Cu > Ni > Co > Pb > Cd in bed sediment, while Al > Fe > Mn > Cr > Zn > Ni > Cu > Pb > Co > Cd in SPM. Among the abundant metals, Fe and Mn average concentrations exceeded BIS and WHO limits in river water. Similarly, Fe, Cd, and Zn, and most metals exceeded local background concentrations in bed sediment and SPM, respectively. Major ion chemistry in water signified carbonate weathering dominance during the time of sampling. Generally, Mn, Ni, Cu, Cr, and Co were derived from natural weathering and erosion, while Zn, Cd, and Pb were derived from both natural and anthropogenic sources. Metal index (MI) for river water showed that 27% of the locations were anthropogenically affected, whereas contamination factor and ecological risk assessment indicated highest contamination and risk from Cr and Cd in suspended sediments around urban centers in the middle basin. Furthermore, the confluence of Chambal and Yamuna increased heavy metal load in Yamuna and Ganga, respectively. The study highlighted the role of the water–sediment interaction indicating SPM is acting as a sink for metals followed by bed sediment.

Suspended Particulate Matter Analysis of Pre and During Covid Lockdown Using Google Earth Engine Cloud Computing: A Case Study of Ukai Reservoir.

Presence of suspended particulate matter (SPM) in a waterbody or a river can be caused by multiple parameters such as other pollutants by the discharge of poorly maintained sewage, siltation, sedimentation, flood and even bacteria. In this study, remote sensing techniques were used to understand the effects of pandemic-induced lockdown on the SPM concentration in the lower Tapi reservoir or Ukai reservoir. The estimation was done using Landsat-8 OLI (Operational Land Imager) having radiometric resolution (12-bit) and a spatial resolution of 30m. The Google Earth Engine (GEE) cloud computing platform was used in this study to generate the products. The GEE is a semi-automated workflow system using a robust approach designed for scientific analysis and visualization of geospatial datasets. An algorithm was deployed, and a time-series (2013-2020) analysis was done for the study area. It was found that the average mean value of SPM in Tapi River during 2020 is lowest than the last seven years at the same time.

A Generic Relation Between Turbidity, Suspended Particulate Matter Concentration, and Sediment Characteristics

AbstractOptical turbidity sensors have become standard instrumentation to estimate suspended particulate matter concentration (SPMC). However, turbidity readings respond to factors other than SPMC, such as particle size and shape, organic fraction, sediment density and color. Therefore, local and site dependent calibrations are needed to transfer turbidity to SPMC. In this study, we propose a new relation between turbidity, suspended particulate matter (SPM) carbon content and particle size, which helps to move from local calibrations between turbidity and SPMC toward generic relations based on inherent SPM properties. Organic content is known to influence particle size, density and, as a result, turbidity, but an explicit formulation of turbidity accounting for organic content has not yet been established. We address this knowledge gap by collecting field data from four sites representing contrasting land use types, geological settings and watershed size. The sites were monitored with a turbidity meter, a LISST‐200X particle size analyzer and an automatic water sampler. SPM samples were collected and analyzed for particle size, carbon content, and color. Local calibrations between turbidity and SPMC derived at each site were compared with a generic calibration, where SPMC was obtained as a function of turbidity, carbon content, particle size and color. The mean relative error associated to predicted SPMCs was equal to 3% when using the generic calibration, which is only marginally lower than the mean relative error of 5% obtained using the local calibrations.

Mercury levels in an environmentally protected estuarine area in Northeast Brazil: partitioning in the water column and transport to the ocean.

In this study, total Hg concentrations (HgT) were determined in the suspended particulate matter (SPM) and the dissolved fraction of the water column to evaluate their behavior through a gradient of physical-chemical parameters in a continuum between rivers and the Serinhaém River estuary of the Pratigi Environmental Protection Area, a pristine environment without point sources of Hg contamination, located in Northeast Brazil. Twelve points were sampled, forming a river-estuary transect, and two samplings were carried out (April and September 2019). Significant spatial and temporal effects were detected only for particulate HgT and not for dissolved HgT. Considering both samplings, the mean HgT concentrations in SPM were 1112 ± 824 and 44 ± 33ng·g-1 in the river and estuary, respectively. Also, HgT concentrations in the dissolved fraction (1.61 ± 0.61ng·L-1) were below the limits established by environmental agencies (CONAMA = 2μg∙L-1 and USEPA = 1.4μg·L-1). Salinity and SPM concentrations were important predictors of HgT in the water column (R2 = 0.81, p < 0.0001; R2 = 0.56, p < 0.0001, respectively). Mercury transport to the ocean through SPM was 2kg∙year-1, 4000 times greater than the dissolved fraction.

210Po and 210Pb as tracers for particle cycling in a shallow semi-enclosed bay of Taiwan Strait

Naturally-occurring 210Po and 210Pb are good tracers for particle cycling in the estuarine and coastal environment. Activities of 210Po and 210Pb were measured in samples of bulk (wet + dry) atmospheric deposition, river water and surface seawater collected in the Zhangjiang Estuary-Dongshan Bay to investigate the geochemical scavenging rates (or residence times) of these particle-reactive nuclides. The spatial distribution of 210Po and 210Pb were strongly influenced by suspended particulate matter (SPM) concentrations and in almost all stations, 210Po and 210Pb were mainly in particulate form (51.7%–92.2% of the total for 210Po and from 44.3% to 90.3% for 210Pb). Due to the very high SPM concentration, enhanced scavenging of 210Po and 210Pb was observed in the maximum turbidity zone of Zhangjiang River, with a marked decrease of dissolved nuclides’ activities. We built a mass balance model and we found out that atmospheric inputs are the major source of these radionuclides comparing with other sources (e.g., river inputs or ingrowth production) in the study area. Residence times of 210Pb were calculated to be 2.2–9.8 and 0.5–8.9 days for dissolved and particulate 210Pb, respectively. And residence times of dissolved and particulate 210Po were 6.3–31.7 and 2.2–13.9 days, respectively. In the turbidity zone, we found an unexpected result that particulate 210Po and 210Pb had the longest residence times (about two weeks), suggesting that SPMs in the turbidity zone would not be easy to sink to the sea floor. We also found that different SPMs showed significantly different 210Po/210Pb activity ratios, which increased in the following order: atmospheric deposition in dry season < SPMs in river < SPMs in the Zhangjiang Eastuary-Dongshan Bay < biogenic particles (including detritus, fecal pellets, cells of phytoplankton and zooplankton). This phenomenon implied that 210Po/210Pb activity ratio in the particles has the potential application in distinguishing SPM sources in the coastal seas.

Typhoon triggers estuarine heavy metal risk by regulating the multifractal grainsize of resuspended sediment

The turbulent boundary layer generated by wind in the estuarine surface water serves as a main factor affecting the distribution of suspended particulate matter (SPM) and suspended sediment concentration (SSC). In this study, representative typhoon-induced variation of surface fine SPM (<63 μm) was simulated in the Yangtze River Estuary (YRE) under two time scenarios. Each scenario contained four grainsize SPM fractions named Fraction 1 (<8 μm), Fraction 2 (8–16 μm), Fraction 3 (16–32 μm), Fraction 4 (32–63 μm). The typhoon-induced resuspended multifractal SSC quantification (TRMSQ) based on the relationship between SPM grainsize and heavy metal adsorption capacity was proposed to assess the variation in the resuspended threat of heavy metal to 6 key estuarine protected objects (three reservoirs & three national reserves) between Scenarios 1 and 2. The results presented that Fraction 3 exhibited the maximum increment in SSC resuspension mass and longest regression time from typhoon. Combined with TRMSQ, chromium (Cr) was calculated to be the riskiest typhoon-induced factor. The integrated resuspended risk of heavy metals for each protected object tends to increase from the northwest of Chongming Island (1.2) towards the maximum turbidity zone (>9) downstream, with an estuary-wide mean of 3.3.

The Effect of Suspended Particulate Matter on the Supraglacial Lake Depth Retrieval from Optical Data

Supraglacial lakes (SGL) are a specific phenomenon of glaciers. They are important for ice dynamics, surface mass balance, and surface hydrology, especially during ongoing climate changes. The important characteristics of lakes are their water storage and drainage. Satellite-based remote sensing is commonly used not only to monitor the area but also to estimate the depth and volume of lakes, which is the basis for long-term spatiotemporal analysis of these phenomena. Lake depth retrieval from optical data using a physical model requires several basic assumptions such as, for instance, the water has little or no dissolved or suspended matter. Several authors using these assumptions state that they are also potential weaknesses, which remain unquantified in the literature. The objective of this study is to quantify the effect of maximum detectable lake depth for water with non-zero suspended particulate matter (SPM). We collected in-situ concurrent measurements of hyperspectral and lake depth observations to a depth of 8 m. Additionally, we collected water samples to measure the concentration of SPM. The results of empirical and physically based models proved that a good relationship still exists between the water spectra of SGL and the lake depth in the presence of 48 mg/L of SPM. The root mean squared error for the models ranged from 0.163 m (Partial Least Squares Regression—PLSR model) to 0.243 m (physically based model), which is consistent with the published literature. However, the SPM limited the maximum detectable depth to approximately 3 m. This maximum detectable depth was also confirmed by the theoretical concept of Philpot (1989). The maximum detectable depth decreases exponentially with an increase in the water attenuation coefficient g, which directly depends on the water properties.

Wildfires on Cr-rich Ferralsols can cause freshwater Cr(VI) pollution: A pilot study in New Caledonia

In the context of global warming, environmental forcing of wildfires on continental ecosystems is on a growing trend. Among other environmental impacts, wildfires can enhance trace metals concentration in freshwater systems. In this regard, chromium is of particular environmental and health concern because the temperature-induced oxidation of the less mobile and toxic Cr(III) form to the most mobile and toxic Cr(VI) one might represent a risk of freshwater pollution. The aim of the present study was to make a first assessment of this risk in New Caledonia by quantifying the influence of soil heating on Cr(VI) mobility in Cr-rich Ferralsols that cover about 1/3 of this French overseas territory. The results obtained indicated an enhanced Cr(VI) mobility upon soil heating from 200 °C, with a marked turnaround from 400 °C. Based on these results, a solid/solution mass balance approach allowed to confirm the risk of freshwater Cr(VI) pollution as a function of suspended particulate matter (SPM) concentration issued from burned Cr-rich Ferralsols. In addition, the results obtained revealed an apparent control of the Fe-oxides/silicates ratio on Cr(VI) mobility upon soil heating. Since this ratio decreases from the top to the bottom of ultramafic catchments, this latter result suggests that the risk of freshwater Cr(VI) pollution could depend on the actual location of the wildfires at the top or slope/base of these catchments. Since freshwaters represent the major water resource for the inhabitants of New Caledonia, these results point to the need for a larger evaluation of the risk of wildfires-induced freshwater Cr(VI) pollution at other catchments composed of Cr-bearing soils like Cambisols and Vertisols. At the larger scale, they also point to the need to foster studies aimed at better evaluating the risk of wildfires-induced freshwater Cr(VI) pollution at Cr-bearing pedological settings worldwide.

Continuous Monitoring of Suspended Particulate Matter in Tropical Inland Waters by High-Frequency, Above-Water Radiometry.

Water and sediment discharges can change rapidly, and low-frequency measurement devices might not be sufficient to elucidate existing dynamics. As such, above-water radiometry might enhance monitoring of suspended particulate matter (SPM) dynamics in inland waters. However, it has been barely applied for continuous monitoring, especially under partially cloudy sky conditions. In this study, an in situ, high-frequency (30 s timestep), above-water radiometric dataset, collected over 18 days in a tropical reservoir, is analyzed for the purpose of continuous monitoring of SPM concentration. Different modalities to retrieve reflectance spectra, as well as SPM inversion algorithms, were applied and evaluated. We propose a sequence of processing that achieved an average unsigned percent difference (UPD) of 10.4% during cloudy conditions and 4.6% during clear-sky conditions for Rrs (665 nm), compared to the respective UPD values of 88.23% and 13.17% when using a simple calculation approach. SPM retrieval methods were also evaluated and, depending on the methods used, we show that the coefficient of variation (CV) of the SPM concentration varied from 69.5% down to 2.7% when using a semi-analytical approach. As such, the proposed processing approach is effective at reducing unwanted variability in the resulting SPM concentration assessed from above-water radiometry, and our work paves the way towards the use of this noninvasive technique for high-frequency monitoring of SPM concentrations in streams and lakes.

Correlation analysis and application investigation of multi-angle simultaneous polarization measurement data and concentration of suspended particulate matter in the atmosphere

Determining the composition, particle size distribution and concentration changes of suspended particulate matter in the atmosphere is important for evaluating the quality of air and its impact on public health. The scattering and absorption of light by suspended particulate matter can change the polarization state of light, which can be used to extract characteristic information of measured particles. Firstly, we use our previously developed multi-angle simultaneous polarization measurement device to monitor the particulate matter around Dianshan Lake, Shanghai, and obtain high-throughput, high-dimensional Stokes data for nearly 1 month. The correlation between the Stokes data measured and the reference concentrations of five suspended particulate matter (Si, K, Fe, Ca, and Zn) was analyzed using the Periodical canonical correlation analysis (PCCA) method. The study shows a strong correlation between the three Stokes vectors and the concentrations of two types of suspended particulate matter in the atmosphere. Moreover, a prediction model for the concentration change of suspended particles was proposed by combining the locally weighted linear regression (LWLR) and the auto regressive moving average (ARMA) model. The prediction results on the concentration change of K and Fe in the atmosphere verified the validity of our method. The research in this work offers the possibility of continuous analysis and prediction of atmospheric suspended particulate matter in real environments.

Variation of ambient air pollutants concentration over Lucknow city, trajectories and dispersion analysis using HYSPLIT4.0

The present study deals with the analysis of daily average concentrations of respirable suspended particulate matter (RSPM- PM10), sulfur dioxide (SO2), and nitrogen dioxide (NO2) at seven monitoring stations namely, Hazratganj, Talkatora, Mahanagar, Aliganj, Sarai Mali Khan, Gomtinagar, and Ansal TC in Lucknow city from 2016 to 2020. The analysis shows that the annual average concentration of RSPM varies from 148.74 to 323.05 µg/m3, SO2 varies from 7.11 to 8.94 µg/m3 and NO2 from 23.52 to 31.86 µg/m3 at all the locations. From the analysis of seasonal variation, it is found that the minimum concentration of RSPM found to be 81.59 µg/m3 in monsoon and maximum concentration was found to be 447.47 µg/m3 in post-monsoon. However, the seasonal variation of SO2 was found in the range of 5.55 to 10.94 µg/m3 and NO2 in the range of 20.23 to 38.40 µg/m3, which are below the prescribed standards. The pollution level decreased to some extent due to the COVID-19 lockdown in the year 2020 but not below the prescribed standard for RSPM. The levels of PM10 in Lucknow are not reducing despite the government of India banning industries and adopting other safeguards within the city. The Trajectory and Dispersion study using the HYSPLIT4.0 model shows insufficient local pollution control, and pollutants are carried from adjacent locations due to the wind blowing from north-west direction to keep daily pollution levels over the standards prescribed by Central Pollution Control Board (i.e., 100 µg/m3). The peak concentration of RSPM is recorded to be 323.05 µg/m3 for the year 2017 at the Hazratganj monitoring station. Over the study region, wavelet analysis of monthly averaged values of PM10 data sets at all seven stations revealed that the presence of semi-annual and annual periodicity. The findings reveal that controlling of particulate matter pollution in the city is a significant concern and has an alarming situation as compared to SO2 and NO2 pollutants.

The HYPERMAQ dataset: bio-optical properties of moderately to extremely turbid waters

Abstract. Because of the large diversity of case 2 waters ranging from extremely absorbing to extremely scattering waters and the complexity of light transfer due to external terrestrial inputs, retrieving main biogeochemical parameters such as chlorophyll-a or suspended particulate matter concentration in these waters is still challenging. By providing optical and biogeochemical parameters for 180 sampling stations with turbidity and chlorophyll-a concentration ranging from 1 to 700 FNU and from 0.9 to 180 mg m−3 respectively, the HYPERMAQ dataset will contribute to a better description of marine optics in optically complex water bodies and can help the scientific community to develop algorithms. The HYPERMAQ dataset provides biogeochemical parameters (i.e. turbidity, pigment and chlorophyll-a concentration, suspended particulate matter), apparent optical properties (i.e. water reflectance from above water measurements) and inherent optical properties (i.e. absorption and attenuation coefficients) from six different study areas. These study areas include large estuaries (i.e. the Rio de la Plata in Argentina, the Yangtze estuary in China, and the Gironde estuary in France), inland (i.e. the Spuikom in Belgium and Chascomùs lake in Argentina), and coastal waters (Belgium). The dataset is available from Lavigne et al. (2022) at https://doi.org/10.1594/PANGAEA.944313.

Lessons Learnt from the Revitalisation of Chemical Factory in Marktredwitz and River Banks Downstream: When ‘Renaturation’ Can Be Harmful

Our study addressed mercury contamination hotspots that originated from Chemical Factory Marktredwitz, Germany. The factory was abandoned in 1985 but its legacy has been persistently endangering the river ecosystem of the Ohře River, a Labe (Elbe) River tributary in the Czech Republic. We identified the timing for the peak contamination of fine sediments entering the Skalka Reservoir located on the Ohře River downstream of the Czech German boundary. Age constraints for the reservoir sediments were obtained using gamma spectrometry analyses of 137Cs and unsupported (excess) 210Pb. We also summarised historical and current Hg concentrations in suspended particulate matter in the Kössein–Röslau–Ohře river system and recent Hg concentrations in aquatic plants. Secondary contamination and its transfer to the Czech stretch of the Ohře River and the Skalka Reservoir through severely contaminated suspended material peaked during the period of factory closure and the start of remediation. The Hg contamination import to the Czech Republic is not likely to improve if the river is left without traditional management of bank reinforcement. This case study highlights a gap in safety regulations for the management of severely contaminated rivers and demonstrates the need to consider the role of historical contamination in river ‘renaturation’.

Identification and trend analysis of organic cationic contaminants via non-target screening in suspended particulate matter of the German rivers Rhine and Saar

Non-target screening of suspended particulate matter (SPM), collected from the German rivers Rhine and Saar, was conducted with the goal of identifying organic, permanent cationic contaminants and of estimating their temporal trends over an extended period. Therefore, annual composite samples of SPM, provided by the German Environmental Specimen Bank, were extracted and analyzed with high resolution LC-QToF-MS/MS. To facilitate the identification of substances belonging to the class “permanent cations”, prioritization methods were applied utilizing the physicochemical properties of these compounds. These methods include both interactions of the analyte molecules with cation exchange resins and analyzing mass deviations when changing from non-deuterated to deuterated mobile phase solvents during LC-MS analysis. By applying both methods in a combined approach, 123 of the initially detected 2695 features were prioritized, corresponding to a 95% data reduction. This led to the identification of 22 permanent cationic species. The organic dyes Basic Yellow 28 and Fluorescent Brightener 363 as well as two quaternary ammonium compounds (QACs) were detected in environmental samples for the first time to best of or knowledge. The other compounds include additional QACs, as well as quaternary tri-phenylphosphonium compounds (QPC/TPP). In addition to identification, we determined temporal trends of all compounds over a period of 13 years and assessed their ecotoxicological relevance based on estimated concentrations. The two QACs oleyltrimethylammonium and eicosyltrimethylammonium show significant increasing trends in the Rhine SPM and maximum concentrations in the Saar SPM of about 900 and 1400 µg/kg, respectively. In the case of the dyes, constant trends have been observed at the end of the studied period, but also maximum concentrations of 400 µg/kg for Basic Yellow 28 in 2006 and 1000 µg/kg for Fluorescent Brightener 363 in 2015, potentially indicating a strong ecotoxicological risk.

Water Turbidity and Suspended Particulate Matter Concentration at Dredged Material Dumping Sites in the Southern Baltic.

Dredged material dumping is an activity that causes some of the greatest changes in coastal waters. It results in the need to regularly monitor the properties of seawater related to water quality. In this study, we present the first wide-ranging attempt to correlate seawater turbidity and suspended particulate matter (SPM) concentrations within dumping sites and adjacent waters on the basis of in situ measurements. In the years 2019–2020, we examined four dumping sites, namely Darłowo, Gdynia, Gdańsk, and DCT, located in Polish coastal waters of the Baltic Sea, in the course of four measurement campaigns conducted in the spring, summer, autumn, and winter. The measurements were conducted using a turbidity sensor to determine the turbidity, in formazin turbidity units (FTU), a spectrophotometer to determine the concentrations of nutrients (total phosphorus (P-tot), phosphate phosphorus (P-PO4−3), total nitrogen (N-tot), ammonium nitrogen (N-NH4+), and nitrate nitrogen (N-NO3−)), as well as glass microfiber filters to determine the concentrations of SPM. The analysis of the relationship between the turbidity and SPM within the dumping sites in comparison to reference points showed that the dumping sites are very complex waters and that the issue must be approached locally. The highest turbidity values were registered in the spring, and they correlated linearly with the SPM concentrations (R2 = 0.69). Moreover, we performed a statistical cluster analysis to illustrate the similarities between sampling points in the four dumpsites based on nutrient concentrations. We conclude that the influence of the dumping sites on the local bio-optical and chemical properties significantly exceeds their borders and spreads to the adjacent waters. Nutrient concentrations in many cases exceeded the legal policy limits.

Biosolar green roofs and ambient air pollution in city centres: Mixed results

Green roofs are known for their ability to reduce ambient air pollution. While the accurate valuation of the air pollution removal services provided by green roofs is rapidly developing, much of this research is still in its infancy, with only a small number of in-situ studies that truly examine the impact of green roofs on city air quality. In this study we present the longest study conducted on an Australian green roof with in-situ air quality monitoring. Field measurements were utilised to calculate the ambient air pollutant removal of an extensive green roof compared to a proximal, near-identical conventional roof over three seasons. The average concentrations of ambient ozone was lower on the green roof compared to that of the conventional roof surface. The theoretical ozone and nitrogen dioxide removal rates on the green roof were higher than the average concentrations calculated from previous research at 3.82 g m-2y-1 and 1.29 g m-2y-1 respectively. There was no significant difference in the average suspended particulate matter concentrations between the two roofs. The particulate matter removal rate was lower than the average previous findings at 0.29 g m-2y-1. The green roof studied was theoretically capable of removing 0.5 kg of PM2.5, 6.9 kg of O3 and 2.3 kg of NO2 per year, values which were significantly higher than the conventional roof. Ambient nitrogen dioxide concentrations were higher on the green roof – largely attributed to local construction activities.

In-situ long-period monitoring of suspended particulate matter dynamics in deep sea with digital video images

Suspended particulate matter (SPM) plays an important role in material transport, deposition, resuspension and the function of benthic communities’ processes in deep sea. SPM concentration data is usually indirectly measured by optical/acoustic sensors. However, converting these sensors’ signal to SPM concentration is associated with a number of uncertainties, which will lead to mis-estimation of the results. Some researchers recommend combining several optical/acoustic sensors to determine SPM concentration. However, due to the lack of corresponding video images, the interpretation of significant mismatch signals recorded by different sensors is subjective. Consequently, a better understanding of long-period SPM dynamics, especially in deep sea, is still a challenge. In this study, we seek to monitor the dynamics of SPM in deep sea, by firstly obtaining in-situ digital video images at a water depth of 1450 m on the northern slope of South China Sea in 2020, and secondly developing a digital image processing method to process the in-situ monitoring data. In this method, we defined an image signal which was the ratio between the area of the SPM and that of the total image, to characterize the SPM concentration. A linear regression model of the image signal and SPM concentration was established (R2 = 0.72). K-fold cross-validation showed that the performance of the model was well. We calculated the SPM concentration derived from image signal, and manually classified SPM into three distinct morphological groups. The long-period observation revealed that numerous aggregates existed in deep sea. The change of SPM concentration and morphology under hydrodynamics was synchronous. When current speed equaled to or exceeded 0.15 m/s, there was a significantly increase in SPM concentration and size. However, such increase was episodic. When current speed decreased, they will also decrease. In addition, we compared the image signal with the optical/acoustic backscattering signal, analyzed the mismatch period among these three signals. We found that the optical backscatter signal can’t accurately reflect the SPM concentration during the mismatch period. To our best knowledge, this is the first time that the in-situ digital video images were used to analyze the dynamics of SPM in deep sea.