Dynamic characteristics of net anthropogenic phosphorus input and legacy phosphorus reserves under high human activity - A case study in the Jianghan Plain.

The increase of phosphorus (P) input related to human activities is one of the main reasons for eutrophication. Notably, in areas with high population densities and intensive agricultural activities, eutrophication has occurred frequently in the Jianghan Plain, so quantitative evaluation of anthropogenic P input is of great significance for the formulation of P pollution control measures. This study estimated net anthropogenic P input (NAPI), riverine total P exports (TP exports), and the pool of P stored in the terrestrial system (legacy P reserves) at the county scale from 1990 to 2019 in the Jianghan Plain. The results showed that NAPI increased from 2645 kg·km-2·yr-1 in 1991 to 5812 kg·km-2·yr-1 in 2014, and then decreased to 4509 kg·km-2·yr-1 in 2019. Non-point sources were the main form of NAPI, of which 75-96% came from agricultural systems. Meanwhile, P fertilizer input was the largest source of NAPI. It is worth noting that the contribution of seed P input in some counties, such as Jiangling County, is relatively high, even exceeding that of net food/feed P input. The P fertilizer application and livestock density were the main drivers for NAPI change. Only 3% of NAPI was exported into rivers, so a large amount of legacy P accumulated in the terrestrial system. An empirical model incorporating NAPI components, cultivated land area ratio, and annual precipitation was established. Based on this model, the average contribution of annual NAPI and the sum of legacy P and natural background sources to TP exports were calculated to be 71% and 29%, respectively. So it is necessary to control P pollution by improving fertilizer use efficiency and enhancing manure management. The results provide a scientific basis for targeted solutions to the sources of P nutrient and its control measures in the middle reach of the Yangtze River.

Effect of Farm Additives on the Potential Bioavailability of Some Nutritional Elements from Kenyan Wild Plants.

In this study, the effects of farm additives on eight wild plants from Nyamira County, Kenya were evaluated for their release of iron, copper, calcium, potassium and magnesium. A hundred and sixty traditional medicinal practitioners were surveyed and found to use Solanum indicum, Carissa edulis, Urtica dioica, Clerodendrum myricoides, Aloe vera, Plectranthus barbatus, Bidens pilosa and Solanum mauense. Atomic absorption spectrophotometer was used to determine the total nutritional element contents in the plants while ultra filtration and physiologically based extraction tests were used to determine the release and solubility of the nutritional elements. The plants from areas with high use of farm additives were found to have statistically significant high total levels of copper from the area with no or little application. Elemental analysis of the molecular species fractions into < 3 kDa, 3-10 kDa, 10 kDa-0.45 µm and 0.45-5 µm mass fractions showed that the mass distribution of the elements in the plants depended on the element. The nutritional elements released by gastrointestinal digestion were more than those released aquatically. Farm additives had no significant effect on the levels of most nutritional elements determined and the plants can be used as mineral element supplements in the human body in addition to their therapeutic activity.

Environmental assessment of agricultural activities and groundwater nitrate pollution susceptibility: a regional case study (Southwestern Romania).

Diffuse pollution of water resources from agricultural sources is a major environmental issue in Europe. The nutrients released in groundwater from cultivated fields and livestock production, together with pesticides, are the main source of concern in the framework of the European Nitrates Directive (91/676/EEC). Southern Romania continues to represent one of the most important cereal production areas of the country. The intensive exploitation during the communist period continues to have repercussions for the precarious quality of groundwater. The aim of our study was to establish the environmental conditions, quantify the agricultural activities at the local administrative unit level and afterwards, to highlight areas of susceptibility to nitrate pollution of groundwater within the Oltenia Plain. One of the most efficient methods to evaluate human influences by agricultural activities on groundwater is using different types of indicators, such as land use indicators (cultivated surfaces), animal husbandry indicators (livestock and great beef units), and agri-environmental indicators (use of fertilisers based on nitrogen and phosphorus, quantity/ha). Throughout the paper, GIS methods are used to determine the degree of influence on nitrate pollution of several eco-pedological indicators: soil types and subtypes, slope of the land, soil texture, soil permeability, and groundwater level. Statistics indicate that 85% of the study area is susceptible to nitrate pollution from agriculture. Indicators provide information that can be easily interpreted by decision and policy makers, and they facilitate the process of reducing nitrate pollution. This study shows that the correlation of statistics and GIS modelling is a useful method for guiding prevention practices for groundwater pollution at the regional scale in Southwestern Romania.