Hypolimnetic withdrawal coupled with oxygenation as lake restoration measures : the successful case of Lake Varese (Italy)

Lake Varese is a relatively small lake, belonging to the drainage basin of lake Maggiore (northern Italy). It has had a long history (since 1960s) of water quality deterioration as the result of cultural eutrophication. In 1967 a restoration project was designed, including a sewerage network, an O-ring sewage diversion system, and a centralised wastewater treatment plant with phosphorus and nitrogen control. Since the 1990's, the lake has been the object of a cooperative research program supported by the European Commission, the Italian Ministry of the Environment, the Lombardy Region, and the Varese Province. The subsequent studies revealed that the lake responded to the decreased external nutrient loads. Besides, mathematical models predicted a rather long period (30 years) to attain the restoration goal, recognising the importance of internal P loading from sediments. Also, it was predicted that the application of in-lake measures would be beneficial in accelerating lake recovery. Recently, two measures have been suggested, i.e. hypolimnetic withdrawal in the deepest section (maximum depth: 26 m) and oxygenation in the shallower section, during summer stratification. Lake Varese constitutes the first case in Italy where in-lake methods are used to counteract the problems caused by excessive nutrient enrichment in a relative large system (lake surface: 14.52 km2). In this paper, preliminary results of the first two years of operation (2000/2001) are summarised. The results are greatly encouraging. Lake water quality characteristics are as follows: Secchi transparency increased from 3.2 m to 4.9 m; annual mean total P concentrations decreased from 180 mg/m3 to 70 mg/m3; average chlorophyll values decreased from 40 mg/m3 to 17 mg/m3; the frequency of nuisance algal blooms declined to half in comparison to the 1990's and the algal density declined by a factor of 4, and anoxia periods decreased in time and space. Moreover, it has been evaluated that nutrient loads from lake Varese, due to the selected water discharges, did not affect the total nutrient budget of lake Maggiore and the downstream water quality.El lago Varese es un lago relativamente pequeño, situado en la cuenca de drenaje del lago Maggiore (norte de Italia). Presenta una larga historia (desde los años 60) de degradación de la calidad del agua como resultado de una eutrofización cultural. En 1967 se diseñó un proyecto de restauración, incluyendo una red de alcantarillado, un sistema en anillo de desvío de aguas residuales, y una planta centralizada de tratamiento de aguas residuales con control de fósforo y nitrógeno. Desde los años 90, el lago ha sido objeto de un programa de cooperación científica financiado por la Comisión Europea, el Ministerio de Medio Ambiente de Italia, la Región de Lombardy y la provincia de Varese. Los estudios resultantes mostraron la respuesta del lago a la disminución de la carga de nutrientes externa. Además, los modelos matemáticos predijeron un período bastante largo (30 años) para lograr el objetivo de restauración, reconociendo la importancia de la carga interna de P de los sedimentos. También, se predijo que la aplicación de medidas en el propio lago sería beneficiosa en la aceleración de la recuperación del lago. Recientemente, se han propuesto dos medidas, i.e. drenaje hipolimnético en la cubeta más profunda (profundidad máxima: 26 m) y oxigenación en la zona más somera, durante la estratificación estival. El lago Varese constituye el primer caso en Italia donde se han adoptado medidas en el propio lago para contrarrestar los problemas causados por un enriquecimiento excesivo de nutrientes en un sistema relativamente grande (superficie del lago: 14.52 km2). En este artículo se resumen los resultados preliminares de los dos primeros años de actuación (2000/2001). Los resultados son enormemente alentadores. Las características de la calidad del agua del lago son las siguientes: la transparencia del Secchi aumentó de 3.2 a 4.9 m; las concentraciones medias anuales de P total disminuyeron de 180 mg/m3 a 70 mg/m3; los valores medios de clorofila disminuyeron de 40 mg/m3 a 17 mg/m3; la frecuencia de florecimiento de algas se redujo a la mitad en comparación con los años 90 y la densidad de algas se dividió por un factor de 4, y los períodos de anoxia disminuyeron en el tiempo y en el espacio. Además, se ha comprobado que la carga de nutrientes procedente del lago Varese, a causa de las descargas de agua selectivas, no afectó al balance total de nutrientes del lago Maggiore ni a la calidad del agua del río aguas abajo

The seven lives of Airbnb. The role of accommodation types

This paper investigates how COVID-19 is impacting different accommodation types, and whether travellers' choices regarding accommodation type are affected by the need for physical distance. Study 1 shows that travellers are very reluctant to book shared flats on Airbnb during the pandemic. However, full flats – controlling for price levels - are preferred to hotel rooms. Study 2 clarifies the process behind the increased choice for full flats, i.e., the need for physical distance. In Study 3, we actively manipulate physical distance and show that assuring physical distance will reduce the concerns towards hotel and shared flat options. Apart from enlightening the psychological process behind accommodation choice, the study offers operators actionable suggestions on how to maximise bookings despite the pandemic. © 202

Contamination of rural surface and ground water by endosulfan in farming areas of the Western Cape, South Africa

BACKGROUND: In South Africa there is little data on environmental pollution of rural water sources by agrochemicals. METHODS: This study investigated pesticide contamination of ground and surface water in three intensive agricultural areas in the Western Cape: the Hex River Valley, Grabouw and Piketberg. Monitoring for endosulfan and chlorpyrifos at low levels was conducted as well as screening for other pesticides. RESULTS: The quantification limit for endosulfan was 0.1 μg/L. Endosulfan was found to be widespread in ground water, surface water and drinking water. The contamination was mostly at low levels, but regularly exceeded the European Drinking Water Standard of 0.1 μg/L. The two most contaminated sites were a sub-surface drain in the Hex River Valley and a dam in Grabouw, with 0.83 ± 1.0 μg/L (n = 21) and 3.16 ± 3.5 μg/L (n = 13) average endosulfan levels respectively. Other pesticides including chlorpyrifos, azinphos-methyl, fenarimol, iprodione, deltamethrin, penconazole and prothiofos were detected. Endosulfan was most frequently detected in Grabouw (69%) followed by Hex River (46%) and Piketberg (39%). Detections were more frequent in surface water (47%) than in groundwater (32%) and coincided with irrigation, and to a lesser extent, to spraying and trigger rains. Total dietary endosulfan intake calculated from levels found in drinking water did not exceed the Joint WHO/FAO Meeting on Pesticide Residues (JMPR) criteria. CONCLUSION: The study has shown the need for monitoring of pesticide contamination in surface and groundwater, and the development of drinking water quality standards for specific pesticides in South Africa

Water Quality Assessment by Multiparameters Flow Citometry

WATER QUALITY CONTROL UTILISES ALGAL BIOASSAYS TO STUDY THE EFFECTS OF CHEMICAL POLLUTANTS ON WATER BODIES. SUCH RESEARCH NEEDS TO MAKE LABORATORY SYSTEMS CLOSER RESEMBLE NATURAL ECOSYSTEMS, THE FIRST STEP BEING TO STUDY MIXED ALGAL POPULATIONS. A HOME-BUILT MULTIPARAMETER INSTRUMENT HAS BEEN USED IN THE FIRST SUCH FLOW CYTOMETRIC STUDIES ON FRESHWATER ALGAL POPULATIONS, MEASURING MULTI-ANGLE LIGHT SCATTER FOR MORPHOLOGICAL DISTINCTION AND TWO WAVELENGHT FLUORESCENCE EMISSION FOR TOXONOMIC DISCRIMINATION. A TOXICOLOGI- CAL STUDY WAS MADE ON THE EFFECTS OF ENVIRONMENTAL CONCENTRATIONS OF TRACE METALS (E.G. 1-10 MG/1 CU OR CD) ON FIVE ALGAE (PANDORINA MORUM, PEDIASTRUM BORYANUM, SELENASTRUM CAPRICORNUTUM, STAUVERSTRUM CINGULUM, STICHOCOCCUS SP.) QUANTIFIED BY THE ES50 AFTER 96 H. SIGNIFICANT GREATER EFFECTS WERE OBTAINED USING CYTOMETRIC DATA WHICH ACCOUNTS FOR THE DEAD POPULATION FRACTION VIA CHLOROPHYLL AUTOFLUORESCENCE (E.G. EC50 OF CU FOR PEDIASTRUM. COULTER - 190 MG/1, CYTOMETER - 100 MG/1, EC50 OF CD FOR STAURASTRUM. COULTER - 18.5 MG/1, CYTOMETER - 1.8 MG/1). A SECOND STUDY SHOWED THAT PREDICTED ENVIRONMENTAL CONCENTRATIONS (10-100 MG/1) OF NITRILOTRIACETIC ACID (NTA) CAUSE A SHIFT TO DOMINANCE OF TWO GREEN ALGAE (PANDORINA, SELENASTRUM) OVER A BLUE-GREEN (OSCIL- LATORIA REDEKEI) IN SYNTHETIC MEDIUM (FROM 52% BIOVOLUME GREENS, 48% BLUE-GREEN IN THE CONTROL TO 72% GREENS, 28% BLUE-GREEN IN 100 MG/1 NTA). NO CHANGE IN RELATIVE CELL NUMBERS WAS OBSERVED AND NO SUCH SHIFT WAS EVIDENT WHEN THE EXPERIMENT WAS REPEATED IN A NATURAL MEDIUM. THE ADVANTAGE OF MULTI-SPECIES BIOASSAYS IS NOTEABLE SINCE NO SINGLE SPECIES APPEARED UNIVERSALLY MOST- SENSITIVE TO THE CONTAMINANTS STUDIEDNA-NOT AVAILABL