Comparison of two commonly used methods for identifying water quality thresholds in freshwater ecosystems using field and synthetic data.

Defining ecological thresholds has become increasingly relevant for water resource management. Despite the fact that there has been a rapid expansion in methods to evaluate ecological threshold responses to environmental stressors, evaluation of the relative benefits of various methods has received less attention. This study compares the performance of Gradient Forest (GF) and Threshold Indicator Taxa Analysis (TITAN) for identifying water quality thresholds in both field and synthetic data. Analysis of 14 years of macroinvertebrates data from the Mediterranean catchments of the Torrens and Onkaparinga Rivers, South-Australia, identified electrical conductivity (EC) and total phosphorus (TP) as the most important water quality variables affecting macroinvertebrates. Water quality thresholds for macroinvertebrates identified by both methods largely corresponded at low EC (GF: 400-900 µS cm-1 vs. TITAN: 407-951 µScm-1), total phosphorus (TP) (GF: 0.02-0.18 mg L-1 vs. TITAN: 0.02-0.04 mg L-1) and total nitrogen (TN) (GF: 0.2 mg L-1 vs. TITAN: 0.28-0.67 mg L-1) concentrations. However, multiple GF-derived thresholds, particularly at high stressor concentrations, were representative of low data distribution, and thus need to be considered with caution. In another case study of South Australian diatom data, there were marked differences in GF and TITAN identified thresholds for EC (GF: 5000 µScm-1 vs. TITAN 1004-2440 µS cm-1) and TP (GF: 250-500 µg L-1 vs. TITAN: 11-329 µg L-1). These differences were due to the fact that while TITAN parsed species responses into negative and positive taxa, GF overestimated thresholds by aggregating the response of taxa that increase and decrease along environmental gradients. Given these findings, we also evaluated the methods' performance using different distributions of synthetic data i.e. with both skewed and uniform distribution of samples and species responses. Both methods identified similar change-points in the case of a uniform environmental gradient, except when species optima were simulated at centre of the gradient. Here GF detected the change-points but TITAN failed to do so. GF also outperformed TITAN when four simulated species change-points were present. Thus, the distribution of species responses and optima and the evenness of the environment gradient can affect the models' performance. This study has shown that both methods are robust in identifying change in species response but threshold identification differs depending both on the analysis used and the nature of ecological data. We recommend the careful application of GF and TITAN, noting these differences in performance, will improve their application for water resource management.

Arsenic and fluoride co-contamination in shallow aquifers from agricultural suburbs and an industrial area of Punjab, Pakistan: Spatial trends, sources and human health implications.

Release of arsenic (As) and fluoride (F-) species into groundwater is a serious health concern around the world. The present study was the first systematic baseline study conducted in Rahim Yar Khan district, Punjab, focusing on As and F- contamination in groundwater. A total of 51 representative groundwater samples comprising of 44 samples from agricultural suburbs and 7 from an industrial base were analysed. Statistical parameters, principal component analysis-multiple linear regression (PCA-MLR) and health risk assessment model were used to investigate the hydro geochemistry, spatial patterns, interrelation, source contribution and associated health risks of high As and F- in groundwater of the study area. Results showed high risk of F- exposure to people of the study area, with all samples exceeding the WHO standard of 1.5 mg/L, and for As, 32.5% of the studied groundwater samples exceeded the WHO standard (10 µg/L). The maximum As (107.23 µg/L) and F- (26.4 mg/L) levels were observed in samples close to the agricultural and smelting areas, implicating the frequent use of fertilizers and influence of industrial effluents in the study area. The PCA-MLR receptor model quantitatively illustrates that the majority of As and F- comes from natural sources, while, among anthropogenic sources, industrial and agricultural activities contributed the most. Health risk assessment revealed a high risk of As and F- contamination to the exposed population; therefore, detailed control strategies and policies are required in order to mitigate the health risks.

Investigation of organochlorine pesticides from the Indus Basin, Pakistan: sources, air-soil exchange fluxes and risk assessment.

Present study aimed to evaluate the contamination status of organochlorine pesticides (OCPs) and their associated potential for air-soil exchange and health risks from ecologically important sites of the Indus Basin, Pakistan. Among different OCPs investigated, ΣDDTs and ΣHCHs were more prevalent compounds in the agricultural soils and ambient air samples of the study area. The average concentrations for DDTs were found higher at downstream agricultural sites, particularly at Head Panjnad (Soil: 320 ng/g; Air: 743 pg/m(3)) and acting as an ultimate sink of ΣOCP burden in soils. Spatial distribution patterns inferred ubiquitous distribution of ΣDDTs in soils and air of the study area. Source diagnostic ratios demonstrated that studied OCPs either are illegally being used in agricultural practices or/and they are residues of past use in the environment. Fugacity fraction model revealed wide variations (ff=0.12-0.94) with 20% of OCPs above equilibrium range and net volatilization of α-endosulfan, ß-HCH and o,p'-DDD. Assessment of cancer risks for OCPs indicated a higher cancer risk (CR>1×10(-6)) for the residents of the Indus Basin. According to the available soil quality guidelines, DDTs and HCHs were above the permissible limits and pose a threat to natural habitat and biodiversity of the Indus Basin.

Ethnobotanical uses of medicinal plants in the highlands of Soan Valley, Salt Range, Pakistan.

ETHNOPHARMACOLOGICAL RELEVANCE: Two thirds of the world's population relies on medicinal plants for centuries for several human pathologies. Present study aimed to identify, catalogue and document the large number of medicinal plants used in traditional medicine in Soan Valley, Salt Range, Pakistan. MATERIALS AND METHODS: Informal interviews were conducted involving a total of 255 villagers (155 male and 65 female and 35 herbalists) to elicit the knowledge and use of medicinal plants. RESULTS: Local communities possessed knowledge of fifty eight (58) medicinal plant species belonging to thirty five (35) families to treat fifteen ailment categories. Whole plant and leaves were the most frequently used plant parts (24%) followed by seed (14%), root (12%), flower (7%), bulb (6%), fruit (4%), stem (3%), latex and rhizome (2%) and sap and gum (1%). Frequently used growth forms of medicinal plants were wild herbs (63%) followed by cultivated herbs (14%), wild trees (11%), wild shrubs (10%) and wild and cultivated herbs (2%). Preparations were administrated generally through oral and topical routes. Local people were familiar mostly with the species in order to deal common ailments particularly cough, cold, digestive problems, fever, headache, and skin infections. Complex ailments were treated by traditional healers. Justica adhatoda, Olea ferruginea, Amaranthus viridis and Mentha royleana were identified as plants with high use value (UV). CONCLUSIONS: This study revealed that the area harbors high diversity of medicinal flora. Despite gradual socio-cultural transformation, local communities still hold ample knowledge of plants and their uses. The reliance on traditional medicines was associated with the lack of modern health care facilities, poverty and the traditional belief of their effectiveness. Medicinal plants play a significant role in management of various human diseases in the study area. A high degree of consensus among the informants was an indicative that plant use and knowledge were still strong, and preservation of this knowledge showed good foresight in the future. Awareness was thus needed to be raised among local people on sustainable utilization and management of plant resources.

Arsenic concentration variability, health risk assessment, and source identification using multivariate analysis in selected villages of public water system, Lahore, Pakistan.

This paper reports high levels and variability in arsenic (As) levels at locations identified as one of the highest As-contaminated locations in Pakistan. Groundwater pollution related to arsenic has been reported since many years in the areas lying in outskirts of District Lahore, Pakistan. A comparative study is done to determine temporal variations of As from three villages, i.e., Kalalanwala (KLW), Manga Mandi (MM), and Shamki Bhattian (SKB). Seventy-three percent of the 30 investigated samples ranging in depth from 20 to 200 m, show an increasing trend in variations of As concentration over a time span of 4 years and 87% of samples exceeded the WHO standard of 10 µg/L for As while 77% of samples have As concentration >50 µg/L (national standard). Further results indicate that high levels of As is accompanied with increase pH (r = 0.8) favoring desorption of As from minerals at higher pH under oxidizing conditions. For health risk assessment of arsenic, the average daily dose, hazard quotient (HQ), and cancer risk were calculated. The residents of the studied areas had toxic risk index in the order of SKB>KLW>MM, with 87% of samples exceeding the typical toxic risk index 1.00 (ranging from 2.3-48.6) which was 83% (ranging from 0.3-41) 4 years before. The results of the present study therefore indicate that arsenic concentrations are increasing in the area, which needs an immediate attention to provide alternate sources of water to save people at risk.