Water Particulate Matter Research Articles

Evaluation of optical detection methods for waterborne suspensions

Making design criteria for turbidimeters more stringent would enable an integrated approach to turbidity measurement and particle detection.Turbidimeters and optical particle counters (OPCs) are used to monitor particulate matter in water. The response from these instruments is governed by the optical properties of the suspension and the instrument design. The recommended design criteria for turbidimeters allow for large tolerances that lead to variations in measurements from different instruments. OPCs provide size‐specific information but may inaccurately size microorganisms or particles having optical properties different from those of the calibration particles. The authors evaluate the effects of optical design parameters in turbidimeters and OPCs. Performance data from two OPCs are presented. A multiple‐angle light‐scattering method was developed to obtain “optical signatures” from suspensions of monodisperse spheres and several microorganism isolates. Such “signatures” provide more optical information on waterborne particles and may also be used to identify specific types of microorganisms in real time.

Rapid measurement of suspended C, N, and P from Precambrian Shield Lakes using Near-infrared Reflectance Spectroscopy

Rapid (<2 min), simultaneous, non-chemical, non-destructive, cost-efficient measurement of the C, N, and P concentrations in suspended, particulate matter in water from lakes of varying trophic status, pH, and extent of metal contamination was attempted by the use of near-infrared reflectance spectroscopy (NIRS). This technique, widely used in the agricultural, food, pharmaceutical, petrochemical, and textile industries, is being explored for its applications to aquatic and environmental sciences. Suspended matter from lake water (10–100 ml) was collected on 2.5 cm dia. G/FC glass fibre filters so that filters bore 10.5–109.2 μg C, 0.8–18.9 μg N, and 0.09-2.67 μg P per filter. Filters were oven-dried and scanned with an NIRSystems 6500 near-infrared spectrophotometer. The spectral data were treated by multiple linear regression analysis to develop mathematical relationships (calibrations) between absorbance at particular wavelengths and amounts of C, N, and P determined by conventional chemical analytical methods. These calibrations were used to predict C, N, and P from an independent set of spectra. Agreement between these NIRS-predicted values and their chemical values was generally greater than 0.9 for C, N, and P ( r 2 from 0.88 to 0.97).

Extracts from settling particulate matter collected in the Stockholm archipelago waters: Embryolethality, immunotoxicity and erod‐inducing potency of fractions containing aliphatics/monoaromatics, diaromatics or polyaromatics

AbstractBioassays previously used for evaluating the toxic potency of specific compounds as well as mixtures proved useful for testing extracts of environmental samples. Samples of settling seston, that is, settling particulate matter in water, were collected with sediment traps placed in the Stockholm archipelago. The samples were Soxhlet extracted with toluene, the extracts run through an Si column, and the eluates separated by HPLC into (a) aliphatics and monoaromatics, (b) diaromatics (e.g., polychlorinated dibenzo‐p‐dioxins [PCDDs] and dibenzofurans [PCDFs] and polychlorinated biphenyls [PCBs]), and (c) polyaromatics. Toxic potency was evaluated in terms of mortality in chick embryos, induction of 7‐ethoxyresorufin‐O‐deethylase (EROD) in chick embryos, inhibition of lymphoid development in chick embryo bursae, and inhibition of lymphoid development in mouse thymus anlagen in vitro. The polyaromatic fraction from seston collected at a location (inner archipelago) close to the center of Stockholm was the most potent of the tested fractions. The polyaromatic fractions were analyzed to determine their contents of 15 polycyclic aromatic hydrocarbons (PAHs) that had previously been toxicity tested. The concentrations of these PAHs were too low to explain the toxicities of the polyaromatic fractions. The diaromatic fraction from the inner archipelago was about four‐ to fivefold less potent as an EROD inducer and at inhibiting lymphoid development in mouse thymus anlagen in vitro, compared with the polyaromatic fraction from this location. Analysis of PCDD/Fs and three coplanar PCBs in this diaromatic fraction revealed that these compounds were responsible only for a minor part of the toxicity of the fraction.