The Chilia branch is the north branch of the Danube River at the Romania-Ukraine border in the Danube Delta; it is a complex system with economic and ecological values. The surface water quality is a major concern and monitoring programs have been developed at the national and international level. The objective of this study was to evaluate the water quality of the Chilia branch in different sampling points from the mouth to the discharge in the Black Sea. The assessment of water quality was done at the individual level taking into account the nutrient concentrations and the standard limits for good ecological status and at integrative levels, using CCME WQI. The longitudinal distribution of Chilia branch water quality was done using GIS method. A total of 106 water samples were collected between 2013 and 2019 from five sampling points. At the individual level, the Chilia branch has a good ecological status except for its levels of total nitrogen, due to the organic nitrogen contribution in 2015. In 90% of nutrient concentrations, low values predominate and high values are considered extreme; only in 10% do high values predominate and low values are considered extreme concentrations. In equal percentages, 50% of the nutrient concentrations have a high degree of heterogeneity and the other 50% of concentration values are very close to the average values, with a high degree of homogeneity. CCME WQI method indicated that 39.93% of surface waters from the Chilia branch had an excellent quality, 45.45% a good quality, and only 14.62% a fair quality.

Pesticides play an important role in boosting agricultural production by controlling pests. Pesticides can be algicides, antimicrobials, disinfectants, herbicides, insecticides, molluscicides, pheromones, rodenticides (raticides), and biopesticides. Despite regulations, pesticide pollution remains a threat to human health, food security, and the environment. Pesticides can harm the environment, affecting water quality and biodiversity, and can be toxic to non-target species. This study aimed to assess the impact of pesticide residues on the surface waters of the Danube River through concentrations determined in the period 1995–2023 in the Danube River Basin. In the present study, scientific techniques were used to collect scientific evidence, consulting academic literature databases such as Google Scholar, Science Direct, MDPI, etc. The study also looked at the quantities of pesticides used in the countries of the Danube River Basin compared to agricultural production during 2014–2022. Five compounds from the pesticide class were selected from the literature. This selection was based on the frequency of determination in surface waters from the Danube River Basin. Pesticides have a negative effect on both the aquatic ecosystem and humans, directly affecting the proper functioning of the body. Continuous monitoring of pesticide residues is essential for determining the quality of the Danube water, as well as for biodiversity.

The crystallographic texture of the whole valves of bivalve mollusks from the family Unionidae Unio pictorum Linnaeus, 1758 and Anodonta cygnea Linnaeus, 1758 is studied using pole figures measured using neutron diffraction. The use of neutron diffraction, in contrast to X-rays, makes it possible to study the valves without destroying them. Thus, we can discuss the study of the global texture of the entire valve. It was revealed that the pole figures of aragonite in the valves repeat their shape. The pole density maxima for U. pictorum from the Danube Delta and the Gulf of Finland in the Baltic Sea, living at different salinities and temperatures, differs by 0.41 mrd. The maximum value of the crystallographic texture for A. cygnea from the Danube Delta was also measured (5.07 mrd). In terms of texture sharpness, it surpasses the shell of marine bivalve mollusks, which are partially or completely composed of aragonite. Although U. pictorum and Mya arenaria Linnaeus, 1758 have different microstructures, their pole figures are very similar in isolines pattern, but differ in pole density maxima. No relationship was found between the crystallographic texture and the microstructure in U. pictorum. In addition, we report good qualitative agreement between aragonite X-ray pole figures of Sinanodonta woodiana Lea, 1834 from the Czech river Luznice, and neutron pole figures of U. pictorum from the Danube Delta.

In this study, we report the findings regarding the toxicity of surface waters collected in March 2023 from five sampling stations in the Zaghen restoration area, located within the Danube Delta Biosphere Reserve, Romania. The assessment of acute toxicity was conducted using two microbiotests: the Thamnotoxkit F and the Daphtoxkit F^TM magna. Even if the acute toxicity effects are less than 50% and do not allow the calculation of a toxicity score for the water samples, the experiments show a different vulnerability of the two zooplanktonic species to the presence of heavy metals in the water with mortality being higher in Thamnocephalus platyurus (20%) than in Daphnia magna (15%).