linjekällor

Linjekällor, or linear sources, are sources of heat, pollutants, or energy that extend along a line rather than at a single point. Commonly used in hydrology, environmental engineering, and atmospheric dispersion, linjekällor model continuous releases along roads, pipelines, ditches, or stream banks. The concept helps simulate distributed emissions that cannot be represented well by a single point source.

In mathematical models, a linjekälla is described by a line segment in space with a distributed strength q(s). The total release Q is the integral of q(s) along the line: Q = ∫ q(s) ds. The resulting concentration or temperature field is obtained by integrating the line-source Green's function over the line. This approach contrasts with point-source and area-source formulations.

Applications include estimating road-traffic emissions in air-quality models, leakage along buried pipelines in groundwater studies, nutrients from drainage lines in soils, and thermal plumes from industrial lines. Linjekällor can be time-dependent, with q depending on time t, allowing short-term events or continuous operations to be represented.

Data requirements include accurate line geometry, source strength distributions, and atmospheric or hydrological transport properties. Estimation often uses GIS to map lines, tracer tests, and inverse modeling to calibrate q(s) against observed concentrations or temperatures. Computational tools may implement linjekällor in finite-difference or finite-element models.

See also: point source, area source, Gaussian plume, advection-dispersion equation, environmental modeling.